Ministry of Education and Science

GOU VPO "Bratsk State University"

Faculty of Energy and Automation

Department of Industrial Heat Power Engineering

Discipline abstract

"Heat and ventilation"

Modern heat supply systems

Development prospects

Performed:

ST group TGV-08

ON THE. Snegireva

Supervisor:

Professor, Ph.D., Department of PTE

S.A. Semenov

Bratsk 2010

Introduction

1. Types of central heating systems and principles of their operation

4.2 Gas heating

4.3 Air heating

4.4 Electric heating

4.5 Piping

4.6 Boiler equipment

5. Prospects for the development of heat supply in Russia

Conclusion

List of used literature

Introduction

Living in temperate latitudes, where most of the year is cold, it is necessary to provide heat supply to buildings: residential buildings, offices and other premises. Heat supply provides comfortable living, if it is an apartment or a house, productive work, if it is an office or warehouse.

First, let's figure out what is meant by the term "Heat supply". Heat supply is the supply of heating systems of a building with hot water or steam. Thermal power plants and boiler houses are the usual source of heat supply. There are two types of heat supply for buildings: centralized and local. With a centralized one, separate areas (industrial or residential) are supplied. For the efficient operation of a centralized heat supply network, it is built, dividing it into levels, the work of each element is to perform one task. With each level, the task of the element decreases. Local heat supply - the supply of heat to one or more houses. Centralized heating networks have a number of advantages: lower fuel consumption and cost savings, use of low-grade fuel, and improved sanitary conditions in residential areas. The district heating system includes a heat source (CHP), a heating network and heat-consuming installations. The combined heat and power plant produces heat and energy. Sources of local heat supply are stoves, boilers, water heaters.

Heating systems differ in different temperatures and water pressures. It depends on customer requirements and economic considerations. With an increase in the distance over which it is necessary to "transfer" heat, the economic costs increase. At present, the distance of heat transfer is measured in tens of kilometers. Heat supply systems are divided according to the volume of heat loads. Heating systems are classified as seasonal, and hot water supply systems are classified as permanent.

1. Types of central heating systems and principles of their operation

District heating consists of three interconnected and sequentially proceeding stages: preparation, transportation and use of the heat carrier. In accordance with these stages, each system consists of three main links: a heat source (for example, a combined heat and power plant or boiler house), heating networks (heat pipelines) and heat consumers.

In decentralized heat supply systems, each consumer has its own heat source.

Heat transfer agents in central heating systems can be water, steam and air; the corresponding systems are called water, steam or air heating systems. Each of them has its own advantages and disadvantages. heat supply central heating

The advantages of a steam heating system are its significantly lower cost and metal consumption compared to other systems: when 1 kg of steam condenses, about 535 kcal is released, which is 15-20 times more than the amount of heat released during cooling of 1 kg of water in heating devices, and therefore steam pipelines have a much smaller diameter than pipelines of a hot water heating system. In steam heating systems, the surface of the heating devices is also smaller. In rooms where people stay periodically (industrial and public buildings), the steam heating system will make it possible to produce heating intermittently and at the same time there is no danger of the coolant freezing with subsequent rupture of pipelines.

The disadvantages of a steam heating system are its low hygienic qualities: dust in the air burns on heating devices heated to 100 ° C or more; it is impossible to regulate the heat transfer of these devices and the system must work intermittently for most of the heating period; the presence of the latter leads to significant fluctuations in air temperature in heated rooms. Therefore, steam heating systems are arranged only in those buildings where people stay periodically - in baths, laundries, shower pavilions, train stations and clubs.

Air heating systems consume little metal, and they can ventilate the room at the same time as heating the room. However, the cost of an air heating system for residential buildings is higher than other systems.

Hot water heating systems have a high cost and metal consumption compared to steam heating, but they have high sanitary and hygienic qualities, which ensure their widespread use. They are arranged in all residential buildings more than two stories high, in public and most industrial buildings. Centralized regulation of the heat transfer of devices in this system is achieved by changing the temperature of the water entering them.

Hot water heating systems are distinguished by the way water is moved and design solutions.

According to the method of water movement, systems with natural and mechanical (pumping) motivation are distinguished. Hot water heating systems with natural induction. The schematic diagram of such a system consists of a boiler (heat generator), a supply pipeline, heating devices, a return pipeline and an expansion vessel. returns to the boiler and then the water circulation is repeated. Its movement occurs under the action of a natural urge that arises in the system when the water in the boiler is heated.

The circulating pressure created during the operation of the system is spent on overcoming the resistance to the movement of water through the pipes (from the friction of water against the pipe walls) and on local resistance (in taps, taps, valves, heating devices, boilers, tees, crosses, etc.) ...

The magnitude of these resistances is the greater, the higher the speed of movement of water in the pipes (if the speed doubles, then the resistance is four times, that is, in a quadratic dependence). In systems with natural impulse in low-rise buildings, the value of the effective pressure is small, and therefore, high velocities of water movement in pipes should not be allowed in them; therefore, the pipe diameters must be large. The system may not be economically viable. Therefore, the use of systems with natural circulation is allowed only for small buildings. The range of such systems should not exceed 30 m, and the value of k should be at least 3 m.

When the water in the system is heated, its volume increases. To accommodate this additional volume of water in heating systems, an expansion vessel 3 is provided; in systems with top distribution and natural impulse, it simultaneously serves to remove from them the air released from the water when it is heated in boilers.

Pump-driven water heating systems. The heating system is always filled with water and the task of the pumps is to create the pressure necessary only to overcome the resistance to the movement of water. In such systems, natural and pumping impulses operate simultaneously; total pressure for two-pipe systems with top distribution, kgf / m2 (Pa)

For economic reasons, it is usually taken in the amount of 5-10 kgf / m2 per 1 m (49-98 Pa / m).

The advantages of systems with pumping motivation are the reduction in the costs of pipelines (their diameter is smaller than in systems with natural motivation) and the ability to supply heat to a number of buildings from one boiler house.

The devices of the described system, located on different floors of the building, operate in different conditions... The pressure p2, which ensures the circulation of water through the device on the second floor, is approximately two times greater than the pressure p1 for the device on the lower floor. At the same time, the total resistance of the ring of the pipeline passing through the boiler and the device of the second floor is approximately equal to the resistance of the ring passing through the boiler and the device of the first floor. Therefore, the first ring will operate with excess pressure, more water will enter the device on the second floor than is required by calculation, and accordingly the amount of water passing through the device on the first floor will decrease.

As a result, overheating will occur in the room on the second floor heated by this device, and underheating in the room on the first floor. To eliminate this phenomenon, special methods of calculating heating systems are used, and they also use double adjustment taps installed on the hot water supply to the devices. If you close these taps at the devices on the second floor, you can completely extinguish the excess pressure and thereby adjust the water flow for all devices located on the same riser. However, the uneven distribution of water in the system is also possible along individual risers. This is explained by the fact that the length of the rings and, consequently, their total resistances in such a system are not the same for all risers: the ring passing through the riser (closest to the main riser) has the least resistance; the longest ring passing through the riser has the greatest resistance.

It is possible to distribute water to individual risers by appropriate adjustment of plug (straight-through) valves installed on each riser. For water circulation, two pumps are installed - one is working, the second is a spare. Near the pumps, a usually closed, bypass line with a gate valve is made. In the event of a power outage and the pump stops, the valve opens and the heating system works with natural circulation.

In a pump-driven system, the expansion vessel is connected to the system in front of the pumps and therefore the accumulated air cannot be discharged through it. To remove air in previously installed systems, the ends of the supply risers were extended with air pipes, on which valves were installed (to shut off the riser for repair). The air line at the point of connection to the air collector is made in the form of a loop that prevents the circulation of water through the air line. At present, instead of such a solution, air taps are used, screwed into the upper plugs of the radiators installed on the upper floor of the building.

Bottom piped heating systems are more convenient to operate than top piped systems. So much heat is not lost through the supply line and water leaks from it can be detected and eliminated in a timely manner. The higher the heater is placed in lower wiring systems, the higher the pressure available in the ring. The longer the ring is, the greater its total resistance; therefore, in a system with a lower wiring, the excess pressures at the devices of the upper floors are much less than in systems with an upper wiring and, therefore, their adjustment is easier. In systems with a lower wiring, the value of natural inducement decreases due to the fact that, due to cooling in the supply risers of the ode, a downward movement arises that slows it down, therefore, the total pressure acting in such systems,

Currently, single-pipe systems are widespread, in which radiators are connected to one riser with both connections; such systems are easier to install and provide a more uniform heating of all heating devices. The most common one-pipe system with bottom piping and vertical risers.

The stand of such a system consists of lifting and lowering parts. Three-way taps can pass the estimated amount or part of the water into the devices in the latter case, the rest of it passes, bypassing the device, through the closing sections. The connection of the lifting and lowering parts of the riser is made by a connecting pipe laid under the windows of the upper floor. Air taps are installed in the upper plugs of the devices located on the upper floor, through which the locksmith removes air from the system during the start-up of the system or its abundant replenishment with water. In one-pipe systems, water flows through all devices in sequence and therefore must be carefully regulated. If necessary, the heat transfer of individual devices is adjusted using three-way taps, and the water flow through individual risers - by through (plug) taps or by installing throttling washers in them. If the riser receives an excessively large amount of water, then the heating devices of the riser first in the direction of the movement of water will give off heat more than is necessary according to the calculation.

As you know, the circulation of water in the system, in addition to the pressure created by the pump and natural impulse, is also obtained from the additional pressure Ap arising as a result of water cooling when moving through the pipelines of the system. The presence of this pressure made it possible to create an apartment water heating system, the boiler of which is not buried, but it is usually installed on the kitchen floor. In such cases, the distance, therefore, the system works only due to the additional pressure arising from the cooling of the water in the pipelines. The calculation of such systems is different from the calculation of heating systems in a building.

Apartment water heating systems are now widely used instead of stove heating in one- and two-story buildings in gasified cities: in such cases, instead of boilers, automatic gas water heaters(LGV), providing not only heating, but also hot water supply.

2. Comparison of modern heat supply systems of a hydrodynamic heat pump of the TC1 type and a classic heat pump

After the installation of hydrodynamic heat pumps, the boiler room will look more like a pumping station than a boiler room. There will be no need for a chimney. There will be no soot and dirt, the need for maintenance personnel will be significantly reduced, the automation and control system will completely take over the heat production management processes. Your boiler room will become more economical and high-tech.

Schematic diagrams:

Unlike a heat pump, which can provide the maximum heat carrier with a temperature of up to +65 ° C, a hydrodynamic heat pump can heat the heat carrier to +95 ° C, which means that it can be easily integrated into the existing heat supply system of a building.

In terms of capital costs for the heat supply system, a hydrodynamic heat pump is several times cheaper than a heat pump, because does not require a low-grade heat circuit. Heat pumps and hydrodynamic heat pumps, similar in name, but different in the principle of converting electrical energy into heat.

Like a classic heat pump, a hydrodynamic heat pump has a number of advantages:

· Efficiency (a hydrodynamic heat pump is 1.5-2 times more economical than electric boilers, 5-10 times more economical than diesel boilers).

· Absolute environmental friendliness (the possibility of using a hydrodynamic heat pump in places with limited MPE norms).

· Complete fire and explosion safety.

· Does not require water treatment. During operation, as a result of the processes taking place in the heat generator of the hydrodynamic heat pump, the coolant is degassed, which has a beneficial effect on the equipment and devices of the heat supply system.

· Fast installation. In the presence of the supplied electric power, the installation of an individual heating point using a hydrodynamic heat pump can be carried out in 36-48 hours.

· The payback period is from 6 to 18 months, due to the possibility of installation in an existing heat supply system.

Time until overhaul 10-12 years old. The high reliability of the hydrodynamic heat pump is structurally laid down and confirmed by the long-term trouble-free operation of hydrodynamic heat pumps in Russia and abroad.

3. Autonomous heat supply systems

Autonomous heat supply systems are designed for heating and hot water supply of single-family and block houses. An autonomous heating and hot water supply system includes: a heat supply source (boiler) and a pipeline network with heating devices and water fittings.

The advantages of autonomous heat supply systems are as follows:

· Lack of expensive external heating networks;

· Possibility of quick implementation of installation and commissioning of heating and hot water supply systems;

· Low initial costs;

· Simplification of the solution of all issues related to construction, since they are concentrated in the hands of the owner;

· Reduction of fuel consumption due to local regulation of heat supply and absence of losses in heating networks.

Such heating systems, according to the principle of the adopted schemes, are divided into schemes with natural circulation of the coolant and schemes with artificial circulation of the coolant. In turn, schemes with natural and artificial circulation of the coolant can be subdivided into one- and two-pipe. According to the principle of movement of the coolant, the schemes can be dead-end, associated and mixed.

For systems with natural induction of the coolant, schemes with top wiring are recommended, with one or two (depending on the load and design features at home) main risers, with an expansion tank installed on the main riser.

A boiler for one-pipe systems with natural circulation can be on the same level with the lower heating devices, but it is better if it is buried, at least to the level of a concrete slab, in a pit or installed in a basement.

The boiler for two-pipe natural circulation heating systems must be buried in relation to the lower heater. The deepening height is specified by calculation, but not less than 1.5-2 m. Systems with artificial (pumping) induction of the coolant have a wider range of applications. It is possible to design circuits with top, bottom and horizontal wiring of the coolant.

Heating systems are:

· Water;

· Air;

· Electric, including with a heating electric cable laid in the floor of the heated premises, and battery heating furnaces (designed with the permission of the energy supplying organization).

Water heating systems are designed vertical with heating devices installed under the window openings and with heating pipes embedded in the floor structure. In the presence of heated surfaces, up to 30% of the heating load should be provided with heating devices installed under the window openings.

Apartment air heating systems, combined with ventilation, should allow operation in full circulation mode (people are absent) only on external ventilation (intensive domestic processes) or on a mixture of external and internal ventilation in any desired ratio.

The supply air is processed as follows:

· Taken from outside (in the amount of sanitary standards per person 30 m3 / h) mixed with recirculated air;

· Cleaned in filters;

· Heated in air heaters;

· Is supplied to the serviced premises through a network of air ducts made of metal or embedded in building structures.

Depending on the external conditions, the system must ensure the operation of the unit in 3 modes:

· Outdoors;

· On complete recirculation;

· On a mixture of external air recirculation.

4. Modern heating and hot water supply systems in Russia

Heating devices are an element of the heating system, designed to transfer heat from the coolant to the air to the enclosing structures of the manned room.

A number of requirements are usually put forward for heating devices, on the basis of which one can judge the degree of their perfection and make comparisons.

· Sanitary and hygienic. Heating devices, if possible, should have a lower body temperature, have the smallest horizontal surface area to reduce dust deposits, and allow dust to be easily removed from the body and the enclosing surfaces of the room around them.

· Economic. Heating devices should have the lowest reduced costs for their manufacture, installation, operation, and also have the lowest metal consumption.

· Architectural and construction. The appearance of the heater should correspond to the interior of the room, and the volume they occupy should be as small as possible, i.e. their volume per unit of heat flux should be the smallest.

· Production and assembly. The maximum mechanization of work in the production and installation of heating devices must be ensured. Heating appliances. Heating devices must have sufficient mechanical strength.

· Operational. Heating devices must ensure controllability of their heat transfer and ensure heat resistance and water tightness at the maximum permissible hydrostatic pressure inside the device under operating conditions.

· Heat engineering. Heating devices must provide the highest specific heat flux per unit area (W / m).

4.1 Hot water heating systems

The most common heating in Russia is water... In this case, the heat is transferred to the premises by the hot water contained in the heating devices. The most common way is water heating with natural water circulation. The principle is simple: water moves due to temperature and density differences. Lighter hot water rises upward from the boiler. Gradually cooling down in the pipeline and heating devices, it becomes heavy and tends downward, back to the boiler. The main advantage of such a system is independence from power supply and rather simple installation. Many Russian craftsmen cope with its installation on their own. In addition, the low circulating pressure makes it safe. But the system requires larger diameter pipes. At the same time, reduced heat dissipation, a limited range and a large amount of time required to start, make it imperfect and suitable only for small houses.

More modern and reliable heating circuits with forced circulation. Here, the water is set in motion by the operation of the circulation pump. It is installed on the pipe supplying water to the heat generator and sets the flow rate.

Fast start-up of the system and, as a result, quick warm-up of the premises is the advantage of the pumping system. The disadvantages include the fact that when the power is turned off, it does not work. And this can lead to freezing and depressurization of the system. The heart of a water heating system is a heat supply source, a heat generator. It is he who creates the energy that provides heat. Such a heart is boilers on different types fuel. Most popular gas boilers... Another option is a diesel boiler. Electric boilers are favorably distinguished by the absence of open flames and combustion products. Solid fuel boilers are not convenient to operate due to the need for frequent heating. To do this, you need to have tens of cubic meters of fuel, space for its storage. And add here the labor costs of loading and procurement! In addition, the heat transfer mode of a solid fuel boiler is cyclical, and the air temperature in heated rooms fluctuates noticeably during the day. Fuel storage space is also required for liquid fuel boilers.

Aluminum, bimetallic and steel radiators

Before choosing any heating device, you need to pay attention to those indicators that the given device must meet: high heat transfer, low weight, modern design, small capacity, low weight. The most important characteristic of a heating device is heat transfer, that is, the amount of heat that should be in 1 hour per 1 square meter of the heating surface. The best device is considered to have a higher indicator. Heat transfer depends on many factors: the heat transfer medium, the design of the heating device, the installation method, the color of the paint, the speed of movement of the water, the speed at which the device is washed with air. All devices of the water heating system are divided by design into panel, sectional, convectors and columnar aluminum radiators or steel.

Panel heating devices

Manufactured from high quality cold rolled steel. They consist of one, two or three flat panels, inside which there is a coolant, and they also have ribbed surfaces that are heated by the panels. The room is heated faster than when using sectional radiators. The above panel water heating radiators are available with side or bottom connection. Side connection is used in cases of replacing an old radiator with a side connection or if the slightly unaesthetic appearance of the radiator does not interfere with the interior of the room.

Sectional hot water heating devices

They are made of steel, cast iron or aluminum. They use the convective method of heating the room, that is, they give off heat by circulating air through them. The air passes through the convector from top to bottom and heats up from a large number warm surfaces.

Convectors

They provide circulating air movement in the room, when warm air rises up, and cold air, on the contrary, falls down and, passing through the convector, heats up back.

Steel hot water radiator can be of sectional and panel type. Steel most often corrodes and therefore these radiators are most suitable for enclosed spaces. Two types of radiators are produced: with horizontal channels and with vertical channels.

Aluminum radiators

Aluminum radiators for water heating are lightweight and have good heat transfer, are aesthetic, but expensive. Often they do not withstand high pressure in the system. Their advantage is that they heat up the room much faster than cast-iron radiators.

Bimetallic radiators

Bimetallic water heating radiators consist of an aluminum body and steel pipes through which the coolant moves. Their main advantage over other radiators is durability. Their working pressure reaches up to 40 atm., While aluminum radiators for water heating operate at a pressure of 16 atm. Unfortunately, at the moment on the European market it is very rare to find these bimetallic water heating radiators on sale.

Column-type cast iron radiators are practically the most common type of radiators. They are durable and practical to use. Cast iron radiators are produced in two-column sections. These heaters can be operated at the highest operating pressure. Their disadvantage is their heavy weight and inconsistency with the design of the room. The above radiators are used in systems with poor heat carrier preparation. They are fairly inexpensive for the price.

4.2 Gas heating

The next most frequently used type of country house heating in Russia is gas. In this case, heating devices adapted for gas combustion are installed directly in the heated rooms.

Gas ovens are economical and have high thermal performance. A distinctive feature of such furnaces is the uniform heating of the outer surface. Gas fireplaces are used as additional sources of heat, which also add special comfort to the interior.

The advantage of gas heating lies primarily in the relatively low cost of natural gas. Its use makes it possible to automate the process of fuel combustion, significantly increases efficiency heating equipment, reduces operating costs. But it is explosive and unacceptable for self-made and installation.

4.3 Air heating

Air heating systems are distinguished depending on the method of creating air circulation: gravitational and ventilated. A gravitational air heating system is based on the difference in air density at different temperatures. During the heating process, natural air circulation occurs in the system. The fan system uses an electric fan that increases the air pressure and distributes it to the air ducts and rooms (forced mechanical circulation).

The air is heated in air heaters that are heated from the inside with water, steam, electricity or hot gases. The heater is placed either in a separate fan chamber (central heating system), or directly in the room that is heated (local system).

The absence of a freezing coolant makes this type of heating a good choice for homes with intermittent use. Air heating will quickly warm up the house, and automatic controls will maintain the temperature you set. The disadvantages of such heating can be attributed only to the danger of the spread of harmful substances by the moving air.

4.4 Electric heating

Direct stationary electric heating systems are very reliable, environmentally friendly and safe. Electricity heats up to 70% of low-rise buildings in Scandinavia and Finland. Electric heating equipment can be divided into 4 groups: - wall-mounted electric convectors; - ceiling heaters; - cable and film systems for floor and ceiling heating; - control thermostats and programmable devices.

Thanks to this variety, it is easy to choose the right option for each specific room. The equipment and operating costs of electrical systems are very low. The systems can automatically turn on and off to maintain the temperature at the set level. Let's say lower it to a minimum during your absence. This feature significantly saves energy costs. Rising prices for various types of fuel make electric heating very attractive for owners of private houses. The disadvantage of electric heating systems is that additional equipment will have to be installed to provide the house with hot water. In addition, we still experience long power outages, and owners of such a system should consider an additional heating source - just in case.

4.5 Piping

Pipelines for supplying the coolant to heating devices can be made of steel water and gas pipes, copper pipes and polymeric materials (metal-plastic pipes, polypropylene pipes and cross-sewn polypropylene pipes). Steel pipe lines are not suitable for concealed piping to radiators. All other pipes can be "hidden" under the finishing materials in compliance with certain system installation technologies. It should also be noted that the installation of a heating system from copper pipes is not allowed if aluminum sectional radiators are selected as heating devices.

4.6 Boiler equipment

As a rule, heating of urban housing is provided from centralized boiler houses and city heating networks, while heating of country houses is mainly carried out from their own (autonomous) heat sources and only occasionally from a boiler house operating for a group of buildings.

The market for boiler equipment in Russia is quite saturated. Almost all leading Western companies producing boiler equipment have their own representative offices. Although Russian boilers are widely represented on the market, they still cannot withstand competition with imported samples in terms of consumer qualities. At the same time, almost all Western manufacturers develop and supply to Russian market boilers adapted to our conditions:

· Multi-fuel boilers;

· Gas boilers operating without electricity.

Multi-fuel boilers

Almost all firms produce boilers for liquid fuel and gas, and some firms add a solid fuel option. It should be noted that multi-fuel boilers, due to the design of the burner, are quite noisy.

Gas boilers operating without electricity

Now the bulk of boilers are designed to work in heating systems with forced circulation of the coolant, and, in a typical Russian case of a power outage, the boiler simply stops and does not work until there is no electricity.

Boiler room control systems

The control system of boiler equipment, depending on the purpose of the boiler room (only heating of one building, heating and hot water supply, the presence of underfloor heating circuits, heating and hot water supply of several buildings), can vary from the simplest, performed on thermostatic regulators, to complex with microprocessor control.

5. Prospects for the development of heat supply in Russia

The main factors that determine the prospects for the development of heat supply in Russia include:

1. A course towards restructuring the unified energy system with the formation of a 3-tier system of enterprises: heat producers, heating networks and energy sellers. The restructuring will be accompanied by the redistribution of property in the energy complex in favor of private entrepreneurship. It is expected to attract large investments, including from abroad. In this case, the restructuring will affect the “big” energy sector.

2. Housing and communal reform associated with the reduction and withdrawal of subsidies to the population in payment utilities, including thermal energy.

3. Stable economic growth in the construction sector.

4. Integration of advanced heat and power technologies of Western countries into the country's economy.

5. Revision of the regulatory and legal framework for the thermal power industry, taking into account the interests of large investors.

6. Bringing domestic prices for fuel and energy resources closer to world prices. Formation in the domestic market of a "shortage" of fuel resources of export potential, first of all - natural gas and oil. Increase in the share of coal and peat in the country's fuel balance.

7. Formation of a balance of municipal and market mechanisms for the organization and management of heat supply in the regions.

8. Formation of modern accounting and billing systems in the market for the production, supply and consumption of heat energy.

Conclusion

Russia belongs to the countries with a high level of centralization of heat supply. Energy, environmental and technical advantage centralized heating over autonomous in the conditions of a monopoly of state ownership was considered a priori. Autonomous and individual heat supply of individual houses was removed from the energy sector and developed according to the leftover principle.

In the centralized heat supply system, CHP plants are widely used - enterprises for the combined generation of electricity and heat. Technologically, CHPPs are focused on the priority of power supply, the associated heat is demanded to a greater extent in the cold period of the year, and is discharged into the environment during the warm period. It is not always possible to harmonize the modes of production of heat and electric energy with the modes of their consumption. Nevertheless, the high level of large-scale power engineering predetermined "technological independence" and even a certain export potential of the country, which cannot be said about small-scale heat power engineering. Low prices for fuel resources, economically unjustified price of heat energy did not contribute to the development of technologies for "small" boiler construction.

Heat supply is an important industry in our life. It brings warmth to our home, provides coziness and comfort, as well as hot water supply needed every day in the modern world.

Modern heat supply systems significantly save resources, are more convenient in operation, meet sanitary and hygienic requirements, are smaller and look more aesthetically pleasing.

Bibliography

1.http: //www.rosteplo.ru

2.http: //dom.ustanovi.ru

3.http: //www.boatanchors.ru

4.http: // whttp: //www.ecoteplo.ru

Heat supply system

Questions

1. The concept of a heat supply system and its classification.

2. Centralized heating systems and their elements.

3. Schemes of heating networks.

4. Laying of heating networks.

1. Complex engineering equipment for rural settlements. / AB. Keatov, P.B. Maisels, I. Yu. Rubchak. - M .: Stroyizdat, 1982 .-- 264 p.

2. Kocheva M.A. Engineering equipment and landscaping of built-up areas: Textbook. - N. Novgorod: Nizhny Novgorod. state architect-build un.-t., 2003. – 121 p.

3. Engineering networks and equipment of territories, buildings and construction sites / I.А. Nikolaevskaya, L.P. Gorlopanova, N.Yu. Morozov; Under. ed by I.A. Nikolaevskaya. - M: Ed. Center "Academy", 2004. - 224 p.

The concept of a heat supply system and its classification

Heat supply system- a set of technical devices, units and subsystems providing: 1) preparation of the heat carrier, 2) its transportation, 3) distribution in accordance with the demand for heat among individual consumers.

Modern heat supply systems must meet the following basic requirements:

1. Reliable strength and tightness of pipelines and installed
on them fittings at the temperatures of the coolant expected under operating conditions.

2. High and stable in operational conditions heat and electrical resistance, resistance, as well as low air permeability and water absorption of the insulating structure.

3. The ability to manufacture in the factory all major "
elements of the heat pipe, enlarged to the limits determined by the type and
bone lifting vehicles. Assembling heat pipes on the track!
ready-made elements.

4. Possibility of mechanization of all labor-intensive construction and installation processes.

5. Maintainability, ie the ability to quickly identify the causes
the occurrence of failures or damage and elimination of malfunctions and their consequences by carrying out repairs at a given time.

Depending on the capacity of the systems and the number of consumers receiving heat energy from them, heat supply systems are divided into centralized and decentralized.

Thermal energy in the form of hot water or steam is transported from a heat source (combined heat and power plant (CHP) or a large boiler house) to consumers through special pipelines - heating networks.

Heat supply systems consist of three main elements: generator, in which heat energy is generated; heat pipelines, through which heat is supplied to heating devices; heating devices, serving to transfer heat from the coolant to the air of the heated room or air in ventilation systems, or tap water in hot water supply systems.

In small settlements, mainly two heat supply systems are used: local and centralized. Central systems are not typical for buildings no higher than three floors.

Local systems- in which all three main elements are located in the same room or in adjacent ones. The range of such systems is limited to a few small rooms.

Centralized systems characterized by the fact that the heat generator is removed from the heated buildings or hot water consumers in a special building. Such a heat source can be a boiler house for a group of buildings, a village boiler house or a combined heat and power plant (CHP).

Local heating systems include solid fuel stoves, gas stoves and heaters, floor or apartment water systems, and electric.

Solid fuel stove heating. Heating stoves are installed in settlements with low heat density. For sanitary and hygienic and fire safety reasons, they are allowed to be installed only in one- and two-story buildings.

The designs of indoor stoves are very diverse. They can be of various shapes in plan, with different finishes of the outer surface and with various schemes chimneys located inside the furnace, through which gases move. Depending on the direction of movement of gases inside the furnaces, a distinction is made between multi-turn channel and channelless furnaces. Firstly, the movement of gases inside the furnace occurs through channels connected in series or in parallel, and secondly, the movement of gases occurs inside the cavity of the furnace freely.

small volume buildings or in small auxiliary buildings at industrial sites remote from the main production buildings. Examples of such systems are stoves, gas or electric heating. In these cases, the production of heat and its transfer to the air of the premises are combined in one device and are located in the heated premises.

The central system heat supply is called a heat supply system for one building of any volume, from one heat source. As a rule, such systems are called heating systems of buildings that receive heat from a boiler installed in the basement of a building, or stand-alone boiler houses. This boiler can supply heat for the ventilation and hot water supply systems of this building.

Centralized heat supply systems are called in the case when heat is supplied from one heat source (CHP or district boiler houses) for many buildings. By the type of heat source, district heating systems are divided into district heating and heating. With district heating, the source of heat is the district boiler house, and with district heating - CHP (combined heat and power plant).

The heat carrier is prepared in the district boiler house (or GEC). The prepared coolant flows through pipelines to the heating and ventilation systems of industrial, public and residential buildings. In heating devices located inside buildings, the coolant gives off part of the heat accumulated in it and is removed through special pipelines to the heat source. Heating from district heating differs not only in the type of heat source, but also in the very nature of heat production.

District heating can be described as district heating based on combined heat and power generation. In addition to the heat source, all other elements in district heating and district heating systems are the same.

By the type of coolant, heat supply systems are divided into two groups - water and steam heat supply systems.

Heat carrier is called an environment that transfers heat from a heat source to heat-consuming devices of heating, ventilation and hot water supply systems. In the heat supply systems used in our country for cities and residential areas, water is used as a heat carrier. At industrial sites, in industrial areas, water and steam are used for heat supply systems. Steam is mainly used for power and technology needs.

Recently, they began to use a single coolant at industrial enterprises - water heated to different temperatures, which is also used in technological processes. The use of a single coolant simplifies the heat supply scheme, leads to a decrease in capital costs and contributes to high-quality and cheap operation.

Sanitary and hygienic, technical, economic and operational requirements are imposed on the heat carriers used in district heating systems. The main sanitary and hygienic requirement is that any coolant should not worsen the microclimatic conditions in closed rooms for people who are in them, but in industrial buildings and for equipment. The coolant should not have a high temperature, as this can lead to a high temperature of the surfaces of heating devices and cause decomposition of organic dust and unpleasantly affect the human body. The maximum temperature on the surface of heating devices should not be higher than 95-105 ° C in residential and public buildings; in industrial buildings, up to 150 ° C is allowed.

The technical and economic requirements for the coolant are reduced to the fact that when using one or another coolant, the cost of heating networks through which the coolant is transported is the lowest, as well as the mass of heating devices is small and the lowest fuel consumption for heating the premises is ensured.

The operational requirements are that the coolant has the qualities that allow for central (from one place, for example, a boiler room) regulation of the heat output of heat consumption systems. The need to change the heat consumption in heating and ventilation systems is caused by variable outdoor temperatures. The service life of heating and ventilation systems is also considered to be an operational indicator of a coolant when a particular coolant is used.

If we compare water and steam according to the listed main indicators, the following advantages can be noted.

Advantages of water: relatively low temperature of water and the surface of heating devices; the ability to transport water over long distances without significantly reducing its thermal potential; the possibility of central regulation of the heat output of heat consumption systems; ease of connection of water heating, ventilation and hot water supply systems to heating networks; preservation of heating steam condensate at CHPPs or in district boiler houses; long service life I of heating and ventilation systems.

Steam advantages: the possibility of using steam not only for heat consumers, but also for power and technological needs; quick warm-up and quick cooling of steam heating systems, which is valuable for a room with periodic heating; steam low pressure(usually used in heating systems of buildings) has a low volumetric mass (about 1650 times less than the volumetric mass of water); this circumstance in steam heating systems makes it possible to ignore the hydrostatic pressure and use steam as a heat carrier in multi-storey buildings; steam heat supply systems for the same reasons can be used with the most unfavorable terrain of the heat-supplied area; lower initial cost of steam systems due to the smaller surface of the heating devices and smaller pipe diameters; ease of initial adjustment due to self-distribution of steam; no energy consumption for steam transportation.

The disadvantages of steam, in addition to the listed advantages of water, can be attributed additionally: increased heat loss through steam pipelines due to a higher steam temperature; The rock service of steam heating systems is much less than that of water systems, due to the more intense corrosion of the inner surface of the condensate pipelines.

Despite some advantages of steam as a heat carrier, it is used for heating systems much less often than water, and then only for those rooms in which people are not for a long time. The building codes and regulations allow steam heating to be used in commercial premises, baths, laundries, cinemas, and in industrial buildings. In residential buildings, steam systems are not used.

In air heating and ventilation systems of buildings, where there is no direct contact of steam with room air, its use as a primary (heating air) heat carrier is permitted. Steam can also be used to heat tap water in hot water systems.

The correct choice, competent design and high-quality installation of the heating system are the guarantee of warmth and comfort in the house during the entire heating season. Heating must be of high quality, reliable, safe and economical. To choose the right heating system, you need to familiarize yourself with their types, installation and operation features of heating devices. It is also important to consider the availability and cost of fuel.

Types of modern heating systems

A heating system is a complex of elements used to heat a room: a heat source, pipelines, heating devices. Heat is transferred using a coolant - a liquid or gaseous medium: water, air, steam, fuel combustion products, antifreeze.

Heating systems for buildings must be selected so as to achieve the highest quality heating while maintaining air humidity that is comfortable for humans. Depending on the type of coolant, such systems are distinguished:

• air;
• water;
• steam;
• electrical;
• combined (mixed).

Heating devices of the heating system are:

• convective;
• radiant;
• combined (convective-radiant).

Diagram of a two-pipe heating system with forced circulation

The following can be used as a heat source:

• coal;
• firewood;
• electricity;
• briquettes - peat or wood;
• energy from the sun or other alternative sources.

The air is heated directly from the heat source without the use of an intermediate liquid or gaseous heat carrier. The systems are used to heat small private houses (up to 100 sq. M.). Installation of heating of this type is possible both during the construction of a building and during the reconstruction of an existing one. A boiler, heating element or gas burner serves as a heat source. The peculiarity of the system lies in the fact that it is not only heating, but also ventilation, since the internal air in the room and the fresh air coming from outside are heated. Air flows enter through a special intake grille, are filtered, heated in a heat exchanger, and then pass through the air ducts and are distributed in the room.

Temperature and ventilation are controlled by thermostats. Modern thermostats allow you to preset a program of temperature changes depending on the time of day. The systems also function in air conditioning mode. In this case, the air flows are directed through the coolers. If there is no need for heating or cooling the room, the system works as a ventilation system.

Diagram of an air heating device in a private house

Installation of air heating is relatively expensive, but its advantage is that there is no need to warm up the intermediate heat carrier and radiators, due to which fuel savings are at least 15%.

The system does not freeze, quickly responds to changes in temperature conditions and heats up the premises. Thanks to the filters, the air enters the premises already purified, which reduces the number of pathogenic bacteria and contributes to the creation of optimal conditions for maintaining the health of people living in the house.

Lack of air heating - overdrying the air, burning out oxygen. The problem can be easily solved if you install a special humidifier. The system can be improved in order to save money and create a more comfortable microclimate. So, the recuperator heats the incoming air, due to the outside. This allows you to reduce energy consumption for heating it.

Additional cleaning and disinfection of air is possible. For this, in addition to the mechanical filter included in the package, electrostatic fine filters and ultraviolet lamps are installed.

Air heating with additional devices

Water heating

This is a closed heating system, it uses water or antifreeze as a heat carrier. Water is piped from the heat source to the heating radiators. In centralized systems, the temperature is regulated at the heating point, and in individual systems - automatically (using thermostats) or manually (taps).

Types of water systems

Depending on the type of connection of heating devices, the systems are divided into:

• one-pipe,
• two-pipe,
• bifilar (two-fired).

According to the wiring method, they are distinguished:

• top;
• bottom;
• vertical;
• horizontal heating system.

In one-pipe systems, the heating devices are connected in series. To compensate for the heat loss that occurs with the sequential passage of water from one radiator to another, heating devices with different heat transfer surfaces are used. For example, can be used cast iron batteries with a lot of sections. In two-pipe, a parallel connection scheme is used, which allows you to install the same radiators.

The hydraulic regime can be constant and variable. In bifilar systems, heating devices are connected in series, as in one-pipe systems, but the heat transfer conditions of radiators are the same as in two-pipe systems. Convectors, steel or cast iron radiators are used as heating devices.

Scheme of two-pipe water heating of a country house

Advantages and disadvantages

Water heating is widespread due to the availability of the coolant. Another advantage is the ability to equip the heating system with your own hands, which is important for our compatriots, who are used to relying only on their own strength. However, if the budget allows you not to save money, it is better to entrust the design and installation of heating to specialists.

This will save you from many problems in the future - leaks, breakouts, etc. Disadvantages - freezing of the system when turned off, long warm-up time of the premises. Special requirements are imposed on the coolant. The water in the systems must be free of impurities, with a minimum content of salts.

Any type of boiler can be used to heat the coolant: solid, liquid fuel, gas or electricity. Most often, gas boilers are used, which implies connection to the mains. If this is not possible, then solid fuel boilers are usually installed. They are more economical than designs that run on electricity or liquid fuels.

Note! Experts recommend choosing a boiler based on a power of 1 kW per 10 sq. These figures are indicative. If the ceiling height is more than 3 m, the house has large windows, there are additional consumers or the premises are not well insulated, all these nuances must be taken into account in the calculations.

Closed home heating system

In accordance with SNiP 2.04.05-91 "Heating, ventilation and air conditioning", the use of steam systems is prohibited in residential and public buildings. The reason is the insecurity of this type of space heating. The heaters heat up to almost 100 ° C, which can cause burns.

Installation is complex, requires skills and special knowledge; during operation, difficulties arise with the regulation of heat transfer; when filling the system with steam, noise is possible. Today, steam heating is used to a limited extent: in industrial and non-residential premises, in pedestrian crossings, heating points. Its advantages are relative cheapness, low inertia, compactness of heating elements, high heat transfer, no heat loss. All this led to the popularity of steam heating until the middle of the twentieth century, later it was replaced by water heating. However, in factories where steam is used for industrial purposes, it is still widely used for space heating.

Steam heating boiler

Electric heating

It is the most reliable and easiest to use type of heating. If the area of ​​the house is no more than 100 m2, electricity is a good option, but heating a larger area is not economically viable.

Electric heating can be used as an additional one in case of shutdown or repair of the main system. Also this good decision for country houses in which the owners live only periodically. Electric fan heaters, infrared and oil heaters are used as additional heat sources.

Convectors, electric fireplaces, electric boilers, underfloor heating power cables are used as heating devices. Each type has its own limitations. So, convectors heat up rooms unevenly. Electric fireplaces are more suitable as a decorative element, and the operation of electric boilers requires significant energy consumption. Underfloor heating is installed with advance consideration of the furniture arrangement plan, because when moving it, the power cable may be damaged.

Scheme of traditional and electric heating of buildings

Innovative heating systems

Separately, mention should be made of innovative heating systems that are gaining popularity. The most common are:

• infrared floors;
• heat pumps;
• solar collectors.

Infrared floors

These heating systems have only recently appeared on the market, but have already become quite popular due to their efficiency and greater efficiency than conventional electric heating. Underfloor heating works from the mains, they are installed in a screed or tile adhesive. Heating elements (carbon, graphite) emit infrared waves that pass through the floor covering, heat the bodies of people and objects, and from them, in turn, heats up the air.

Self-adjusting carbon mats and foil can be mounted under furniture legs without fear of damage. Smart floors regulate temperature thanks to special property heating elements: with overheating, the distance between the particles increases, the resistance increases - and the temperature decreases. Energy costs are relatively low. When the infrared floors are turned on, the power consumption is about 116 watts per running meter, after warming up, it decreases to 87 watts. Temperature control is ensured by thermo-regulators, which reduces energy consumption by 15-30%.

Infrared carbon mats are comfortable, reliable, economical, easy to install

Heat pumps

These are devices for transferring thermal energy from a source to a heat carrier. The idea of ​​a heat pump system itself is not new; it was proposed by Lord Kelvin back in 1852.

How it works: A ground source heat pump takes heat from the environment and transfers it to the heating system. The systems can also work to cool buildings.

How the heat pump works

A distinction is made between open and closed loop pumps. In the first case, the installations take water from the underground stream, transfer it to the heating system, take away thermal energy and return it to the place of intake. In the second, a coolant is pumped through special pipes in the reservoir, which transfers / removes heat from the water. The pump can use the thermal energy of water, earth, air.

The advantage of the systems is that they can be installed in houses that are not connected to a gas supply. Heat pumps are difficult and expensive to install, but they can save on energy costs during operation.

The heat pump is designed to use the heat of the environment in heating systems

Solar collectors

Solar installations are systems for collecting solar thermal energy and transferring it to a coolant

Water, oil or antifreeze can be used as a heat carrier. The design includes additional electric heaters that turn on if the efficiency of the solar installation decreases. There are two main types of collectors - flat and vacuum. The flat ones have an absorber with a transparent coating and thermal insulation. In vacuum ones, this coating is multilayer; in hermetically sealed collectors, a vacuum is created. This allows you to heat the coolant up to 250-300 degrees, while flat installations are able to heat it only up to 200 degrees. The advantages of the units include ease of installation, low weight, and potentially high efficiency.

However, there is one "but": the efficiency of the solar collector depends too much on the temperature difference.

Solar collector in hot water supply and home heating systems Comparison of heating systems shows that there is no ideal heating method

Our compatriots still prefer hot water heating. Usually, doubts arise only about which specific heat source to choose, how best to connect the boiler to the heating system, etc. And yet there are no ready-made recipes suitable for absolutely everyone. It is necessary to carefully weigh the pros and cons, take into account the characteristics of the building for which the system is being selected. If in doubt, you should consult a specialist.

Video: types of heating systems

MODERN HEAT SUPPLY SYSTEMS

(, Khabarovsk Center for Energy Saving)

In Khabarovsk and Khabarovsk Territory, as in many other regions of Russia, "open" heat supply systems are mainly used.

An "open" system in thermodynamics means a system that exchanges mass with the environment, that is, a "non-dense" system.

In this publication, an "open" system means a heat supply system in which the hot water supply (DHW) system is connected via an "open" system, that is, with direct water intake from the heating system pipelines, and the heating and ventilation system is connected according to a dependent connection scheme to heating networks.

Open heating systems have the following disadvantages:

1. High consumption of make-up water and, therefore, high costs of water treatment. With this scheme, the coolant can be used both productively (for the needs of hot water supply) and unproductively: unauthorized leaks.

Unauthorized leaks include:

Leaks through shut-off and control valves;

Leaks in case of damage to pipelines;

Leaks through the risers of the heating system (discharges) with misaligned heating systems and with insufficient pressure drops at the elevator inputs;

Leaks (discharges) during repairs of the heating system, when you have to completely drain the water and then refill the system, and if the outlet valves "do not hold", then you have to "de-energize" the whole block or tie-in.

An example is the accident in November 2001 in Khabarovsk in the Bolshaya-Vyazemskaya microdistrict. In order to repair the heating system in one of the schools, an entire block had to be turned off.

2. With an open DHW circuit, the consumer receives water directly from the heating network. In this case, hot water can have a temperature of 90 ° C or more and a pressure of 6-8 kgf / cm2, which leads not only to excessive consumption of heat, but also potentially creates a dangerous situation for both sanitary equipment and people.

3. Unstable hydraulic regime of heat consumption (one consumer instead of another).

4. Poor quality of the heat carrier, which contains a large amount of mechanical impurities, organic compounds and dissolved gases. This leads to a decrease in the service life of pipelines of heat supply systems due to increased corrosion and to a decrease in their throughput due to "fouling", which violates the hydraulic regime.

5. The impossibility, in principle, of creating comfortable conditions for the consumer when using elevator heating systems.

It is necessary to answer that almost all heat points subscribers of Khabarovsk are equipped with an elevator heat input.

The main advantage of the elevator is that it does not consume energy for its drive. There was an opinion that the elevator has a low efficiency, and this would be true if it would be necessary to consume energy for its operation. In fact, for the mixing operation, the pressure difference in the pipelines of the heat supply system is used. If it were not for the elevator, then the flow of the coolant would have to be throttled, and throttling is a loss of energy. Therefore, as applied to heat inputs, an elevator is not a low-efficiency pump, but a device for re-using the energy spent on the drive of CHPP circulating pumps. Also, the advantages of the elevator include the fact that highly qualified specialists are not required to maintain it, since the elevator is a simple, reliable and unassuming device in operation.

The main disadvantage of the elevator is the impossibility of proportional regulation of the thermal power, since with a constant diameter of the nozzle opening, it has a constant mixing ratio, and the regulation process presupposes the possibility of changing this value. For this reason, in the West, the elevator is rejected as a device for heating stations. Note that this drawback can be eliminated by using an elevator with an adjustable nozzle.

However, the practice of using elevators with an adjustable nozzle has shown their low reliability with poor quality of network water (presence of mechanical impurities). In addition, such devices have a small control range. Therefore, these devices have not found wide application in Khabarovsk.

Another drawback of the elevator is the unreliability of its operation with a small available pressure drop. For stable operation of the elevator, it is necessary to have a pressure drop of 120 kPa or more. However, up to now, in Khabarovsk, elevator units are being designed with a pressure drop of 30-50 kPa. With such a difference, normal operation of elevator nodes is, in principle, impossible and therefore very often consumers with such nodes work for "dumping", which leads to excess losses of network water.

The use of elevator units slows down the introduction of energy-saving measures in heat supply systems, such as the complex automatic regulation of the parameters of the heat carrier in the building and the design of the heating system adequate to these tasks, ensuring the accuracy and stability of comfortable conditions and economical heat consumption.

Complex automatic regulation includes the following basic principles:

regulation in individual heating points (ITP) or automated control units (AUU), which, in accordance with the heating schedule, change the temperature of the coolant supplied to the heating system depending on the outside air temperature;

individual automatic control on each heating device using a thermostat that maintains the set temperature in the room.

All of the above has led to the fact that, starting in 2000, a large-scale transition from "open" dependent heat supply systems to "closed" independent systems with automated heat points began in Khabarovsk.

Reconstruction of the heat supply system with the use of energy-saving measures and the transition from "open" dependent systems to "closed" independent systems will allow:

To increase the comfort and reliability of heat supply by maintaining the required temperature in the premises, regardless of weather conditions and the parameters of the coolant;

It will increase the hydraulic stability of the heat supply system: the hydraulic regime of the main heating networks will be normalized due to the fact that the automation does not allow excess heat consumption to be exceeded;

To obtain a heat saving of 10-15% by regulating the temperature of the coolant in accordance with the outside air temperature and reducing the temperature at night in heated buildings by up to 30% during the transitional period of the heating season;

Increase the service life of pipelines of the building heating system by 4-5 times, due to the fact that, with an independent heat supply scheme, a clean coolant circulates in the internal circuit of the heating system, which does not contain dissolved oxygen, and therefore heating devices and supply pipelines are not clogged with dirt and corrosion products;

Dramatically reduce the recharge of heating networks and, consequently, the cost of water treatment, as well as improve the quality of hot water.

The use of independent heat supply systems opens up new perspectives in the development of intra-quarter networks and internal heating systems: the use of flexible pre-insulated plastic distribution pipelines with a service life of about 50 years, polypropylene pipes for interior systems, stamped panel and aluminum radiators, etc.

However, the transition in Khabarovsk to modern heat supply systems with automated heat points posed a number of problems for design and installation organizations, an energy supply organization, and heat consumers, such as:

Lack of year-round circulation of the coolant in the main heating networks.

An outdated approach to the design and installation of internal heat supply systems.

The need for maintenance modern heat supply systems.

Let's consider these problems in more detail.

Problem No. 1 Lack of year-round circulation in the main pipelines of heating networks.

In Khabarovsk, the main pipelines of the heat supply system are circulated only during the heating season: from about mid-September to mid-May. The rest of the time, the coolant enters through one of the pipelines: supply or return, and part of the time it is supplied one by one, and partly through another pipeline.

This leads to great inconvenience and additional costs when introducing energy-saving technologies in heat supply systems, in particular, in hot water supply systems (DHW). Due to the lack of circulation in the inter-heating season, it is necessary to use a mixed "open-closed" DHW system: "closed" in the heating season and "open" in the inter-heating season, which increases the capital costs of installation and equipment of the heating point by 0.5-3% ...

Problem # 2. An outdated approach to the design and installation of internal heating systems for buildings.

In the pre-perestroika period of development of our state, the government set the task of saving metal. In this regard, the massive introduction of one-pipe unregulated heating systems began, which was due to lower (compared to two-pipe) metal costs, installation costs and higher thermal and hydraulic stability in multi-storey buildings.

Currently, when commissioning new facilities in Russian cities, such as Moscow and St. Petersburg, as well as in Ukraine, in order to save energy, it is mandatory to use thermostats in front of heating devices, which, in fact, with minor exceptions, predetermines the design of two-pipe heating systems.

Therefore, the widespread use of one-pipe systems when equipping each heater with a thermostat has lost its meaning. In controlled heating systems, when a thermostat is installed in front of the heater, a two-pipe heating system turns out to be highly efficient and has increased hydraulic stability. At the same time, the discrepancies in metal costs in comparison with single-pipe are within ± 10%.

It should also be noted that one-pipe heating systems are practically not used abroad.

The schemes of two-pipe systems can be different, however, it is most advisable to use an independent scheme, since when using thermostats (thermostats), the dependent scheme is unreliable in operation due to the low quality of the coolant. With small holes in the thermostats, measured in millimeters, they quickly fail.

It is proposed to use one-pipe heating systems with thermostats only for buildings of no more than 3-4 floors. It also notes the inexpediency of using cast-iron heating devices in heating systems with thermostats, since during operation they wash out molding earth, sand, scale, which clog the holes of the thermostats.

The use of independent heat supply schemes opens up new prospects: the use of polymer or metal-polymer pipelines for internal systems, modern heating devices (aluminum and steel heating devices with built-in thermostats).

It should be noted that a two-pipe heating system, in contrast to a one-pipe heating system, requires mandatory adjustment using special equipment and highly qualified specialists.

It should be noted that even in the design and installation of automated heating points with weather regulation in Khabarovsk, only one-pipe heating systems without thermostats in front of heating devices are being designed and implemented. Moreover, these systems are hydraulically unbalanced, and sometimes so much (for example, an orphanage on Lenin Street) that in order to maintain a normal temperature in the building, the end risers work “for discharge” and this is with an independent heating scheme!

I would like to believe that underestimating the importance of balancing the hydraulics of heating systems is simply due to a lack of the necessary knowledge and experience.

If the Khabarovsk designers and installation organizations are asked the question: "Is it necessary to balance the wheels of the car?", Then the obvious answer will follow: "Undoubtedly!" But why, then, balancing the heating, ventilation and hot water supply system is not considered necessary. After all, incorrect flow rates of the coolant lead to incorrect air temperatures in the room, poor automation, noise, rapid failure of pumps, uneconomical operation of the entire system.

The designers believe that it is enough to carry out a hydraulic calculation with the selection of pipes and, if necessary, washers, and the problem will be solved. But this is not the case. Firstly, the calculation is approximate, and, secondly, during installation, a lot of additional uncontrollable factors arise (most often installers simply do not install choke washers).

It is believed that the hydraulics of heating systems can be linked by calculating the settings of thermostatic valves. This is also wrong. For example, if for some reason a sufficient amount of coolant does not pass through the riser, then the thermostatic valves will simply open, and the air temperature in the room will be low. On the other hand, if the coolant is overrun, a situation may arise when the vents and thermostatic valves are open. All of the above does not at all diminish the need and importance of installing thermostatic valves in front of heating devices, but only emphasizes that for their good operation, balancing of the system is necessary.

Balancing the system means setting up the hydraulics so that each element of the system: radiator, heater, branch, shoulder, riser, main line - have design costs. In this case, the definition and setting of the thermostatic valve settings is part of the commissioning process.

As mentioned above, in Khabarovsk, only hydraulically unbalanced one-pipe heating systems without thermostats are designed and installed.

Let us show by examples of new, commissioned facilities what this leads to.

Example 1. Orphanage No. 1 on the street. Lenin.

Commissioned at the end of 2001. The DHW system is closed, and the heating system is one-pipe, without thermostats, connected according to an independent scheme. Designed - Khabarovskgrazhdanproekt, installation of heating and hot water supply system - Khabarovsk installation department No. 1. Design and installation of a heating point - specialists of KhTsES. The substation is undergoing maintenance at KhTsES.

After the start of the heat supply system, the following shortcomings emerged:

The heating system is not balanced. Overheating was observed in some rooms: 25-27оС, and in others, underheating: 12-14оС. This is due to several reasons:

for balancing the heating system, the designers provided for washers, and the installers did not cut them in, citing the fact that "they will clog up in 2-3 weeks anyway";

individual heating devices are made without closing sections, their surface is overestimated, which leads to overheating of individual rooms.

In addition, in order to ensure circulation and normal temperature in subcooled rooms, the end risers worked for "discharge", which led to water leaks of 20-30 tons per day, and this is with an independent scheme !!!

The supply ventilation system does not work, which is unacceptable, since thermostatic windows with low air permeability are installed in the building.

At the request of the Customer, the specialists of KhTsES installed balancing valves on the risers and carried out balancing of the heating system. As a result, the temperature in the premises leveled off and amounted to 20-22 ° C, the system's make-up was reduced to zero, and the thermal energy savings amounted to about 30%. The ventilation system was not adjusted.

Example 2. Institute for advanced training of doctors.

Commissioned in October 2002. The DHW system is closed, the one-pipe heating system without thermostats is connected according to an independent scheme.

After starting the heating system, the following shortcomings were identified: the heating system is not balanced, there are no fittings for adjusting the system (the project does not even provide for throttling washers). The air temperature in the premises varies from 18 to 25 ° C, and in order to bring the temperature in the corner rooms to 18 ° C, it was necessary to increase the heat consumption by 3 times in comparison with the required one. That is, if the heat consumption of the building is reduced by three times, then in most rooms the temperature will be 18-20 ° C, but at the same time in the corner rooms the temperature will not exceed 12 ° C.

These examples apply to all newly introduced buildings with independent heating schemes in the city of Khabarovsk: a circus and a circus hotel (the vents are open in the hotel (overheating), and in the backstage part it is cold (underflow), residential buildings on Fabrichnaya street, Dzerzhinsky street, therapeutic building of the Railway Hospital, etc.

Problem No. 2 is closely intertwined with problem No. 3.

Problem number 3. The need for maintenance of modern heat supply systems.

As our three-year experience shows, modern heat supply systems for buildings, made with the use of energy-saving technologies, need constant maintenance during operation. To do this, it is necessary to attract highly qualified, specially trained specialists using special technologies and tools.

Let us show this with examples of automated heating points introduced in the city of Khabarovsk.

Example 1. Thermal points not serviced by specialized organizations.

In 1998 in the city of Khabarovsk the Khakobank building on Leningradskaya Street in the city of Khabarovsk was put into operation. The heating system of the building was designed and installed by specialists from Finland. Finnish equipment is also used. The heating system is made according to an independent two-pipe scheme with thermostats, equipped with balancing fittings. The DHW system is closed. The system was maintained by the bank's specialists. During the first three years of operation, a comfortable temperature was maintained in all rooms. After 3 years, complaints were sent from tenants of individual apartments that the apartment was “cold”. Residents turned to KhTSES with a request to examine the system and help establish a "comfortable" regime.

Inspection of the KhCES showed: the automatic control system does not work (the ECL weather regulator is out of order), the heat exchange surfaces of the heat exchanger of the heating system are clogged, which led to a decrease in its heat output by about 30% and an imbalance in the heating system.

A similar picture was observed in a residential building on the street. Dzerzhinsky 4, where the modern heating system was serviced by residents.

Example 2. Heat points serviced by specialized organizations.

To date, about 60 automated heating points are serviced in the Khabarovsk Center for Energy Saving. As our operating experience has shown, in the process of servicing such units, the following problems arise:

cleaning of filters installed in front of DHW and heating heat exchangers and in front of circulation pumps;

control over the operation of pumps and heat exchange equipment;

control over the work of automation and regulation.

The quality of the heat carrier and even cold water in Khabarovsk is very low and therefore the problem of cleaning the filters that are installed in the primary circuit of the DHW and heating heat exchangers, in front of the circulation pumps in the secondary circuit of the heat exchangers, constantly arises. For example, when commissioning in the heating season 2002/03. block of residential buildings on Fabrichniy lane, in each of which IHP was installed, the filter installed in the primary circuit of the heating heat exchanger had to be washed 1-2 times a day during the first 10 days after start-up and then, in the next two weeks, at least one once every 2-3 days. On the building of the circus and the circus hotel in the heating season 2001/02. I had to rinse the cold water filter 1-2 times a week.

It would seem that cleaning the filter installed in the primary circuit is a routine operation that can be performed by an unqualified specialist. However, in order to clean (pour) the filter, it is necessary to stop the entire heating system for some time, turn off the cold water, turn off the circulation pump in the DHW system and then start it all up again. Also, when the heat supply system is turned off, it is advisable to turn off and then restart the automation system to clean the filters so that no water hammer occurs when the heat supply system is started. In this case, if, when the primary circuit of the DHW system is disconnected, the secondary circuit for cold water is not disconnected, then due to temperature expansions in the DHW heat exchanger, a "leak" may appear.

The second problem that arises during the operation of automated heat points is the problem of monitoring the operation of equipment: pumps, heat exchangers, metering and regulation devices.

For example, before starting after the inter-heating period, circulation pumps are often in a "dry" state, that is, they are not filled with network water, and their stuffing box seals dry up, and sometimes even stick to the pump shaft. Therefore, before starting, in order to avoid leaks of heating water through the stuffing box seals, it is necessary to turn the pump smoothly several times by hand.

Also, during operation, it is necessary to periodically monitor the operation of the control valves so that they do not work constantly in the "closed" or "open" mode, pressure regulators, differential pressure, etc., in addition, it is necessary to monitor the change in the hydraulic resistance and heat transfer surface of heat exchangers ...

Changes in the hydraulic resistance and the area of ​​the heat transfer surface of heat exchangers can be monitored by registering or periodically measuring the temperature of the coolant in the primary and secondary circuits of the heat exchanger and the pressure drop and flow rate of the coolant in these circuits.

For example, in the heating season 2001/02. in the hotel of the circus, a month after the start of operation, the temperature of the hot water dropped sharply. Studies have shown that at the beginning of operation, the flow rate of the coolant in the primary circuit of the DHW system was 2-3 t / h, and a month after the start of operation, it was no more than 1 t / h. This happened due to the fact that the primary circuit of the DHW heat exchanger was clogged with welding products (scale), which led to an increase in hydraulic resistance and a decrease in the area of ​​the heat transfer surface. After the heat exchanger was disassembled and washed, the hot water temperature reached normal.

As the experience of servicing modern heat supply systems with automated heating points has shown, in the process of their operation it is necessary to carry out constant monitoring and make adjustments to the operation of automation and regulation systems. In Khabarovsk, in the last 3-5 years, the temperature schedule 130/70 has not been observed: even at temperatures below minus 30 ° C, the temperature of the coolant at the subscribers' inlet does not exceed 105 ° C. Therefore, the specialists of KhCES, serving automated heating points, on the basis of statistical observations of the heat consumption regime of objects before the start of the heating season for each object enter their temperature schedule into the controller, which is then adjusted during the heating season.

The problem of servicing automated heating points is closely related to the lack of a sufficient number of highly qualified specialists who are purposefully not trained within the Far Eastern region. In the Khabarovsk Center for Energy Saving, the maintenance of automated heating units is carried out by specialists - graduates of the Department of Heat Engineering, Heat and Gas Supply and Ventilation of the Khabarovsk State Technical University, trained at equipment manufacturers (Danfos, Alfa-Laval, etc.).

Note that KhTSES is a regional service center of companies supplying equipment for automated heating points, such as: Danfos (Denmark) - a supplier of controllers, temperature sensors, control valves, etc .; Vilo (Germany) - supplier of circulation pumps and pump automation; Alfa Laval (Sweden-Russia) - supplier of heat exchange equipment; TBN Energoservice (Moscow) - supplier of heat meters, etc.

In accordance with the service partnership agreement concluded between HCES and Alfa-Laval, HCES carries out maintenance work on the heat exchange equipment of Alfa-Laval, using personnel trained in the Alfa-Laval service center, and using for these purposes only permitted for operation Alfa-Laval original spare parts and materials.

In turn, Alfa-Laval supplied HCES with equipment, tools, consumables and spare parts necessary for servicing Alfa-Laval plate heat exchangers, trained HCES specialists in its service center.

This allows KhTSES to carry out collapsible and CIP flushing of heat exchangers directly from consumers in Khabarovsk.

Therefore, all issues related to the operation and repair of the equipment of automated heating points are resolved on the spot - in the city of Khabarovsk.

Note also that, unlike other companies involved in the implementation of automated heating units, KhTSES installs more expensive, but more reliable and better equipment (for example, collapsible rather than brazed heat exchangers, pumps with a dry rather than a wet rotor). This guarantees reliable operation of the equipment for 8-10 years.

The use of cheap, but less quality equipment does not guarantee the uninterrupted operation of automated heating points. As our experience, as well as the experience of other companies, shows, this equipment breaks down, as a rule, after 2-3 years and the consumer begins to feel thermal discomfort (see, for example, example 1 from problem No. 3).

Thermal tests of heat exchangers, carried out in St. Petersburg, showed:

The decrease in the thermal efficiency of the heat exchanger is 5% after the first year, 15% after the second, more than 25% after the third, 35% after the fourth, and 40-45% after the fifth;

A decrease in the heat output of the apparatus and the heat transfer coefficient is associated with contamination of the heat exchange surface both from the side of the primary circuit and from the side of the secondary circuit; these contaminants appear in the form of deposits, and from the side of the primary circuit the deposits are brown, and from the side of the secondary circuit they are black;

The brown color of deposits is mainly determined by iron oxides, which are formed in the network water due to the corrosion of the inner surface of heating pipelines; These contaminants from the primary circuit can be easily removed with a soft cloth under running warm water;

The black color of deposits in the secondary circuit is determined mainly by organic compounds, which are in large quantities in the water of the secondary circuit, which circulates in a closed circuit of the building heating system and is not subjected to any cleaning; it is not possible to remove deposits from the side of the secondary circuit in the same way as from the primary circuit, since they are not loose, but dense; to clean the heat exchange plates from the side of the secondary circuit, the plates had to be soaked in kerosene for 15-20 minutes, and then they were wiped with considerable effort with damp rags soaked in kerosene;

Due to the fact that biological deposits formed on the plates from the side of the secondary circuit have a very strong adhesion (adhesion) to the metal surface, CIP chemical flushing of the secondary circuit does not give satisfactory results.

Cheap equipment, as a rule, is used by those implementation firms that are not engaged in servicing the equipment they have implemented, since this requires having the appropriate equipment and materials, as well as qualified personnel, that is, investing heavily in the development of their production base.

Therefore, the consumer is faced with a choice:

To spend a minimum of capital investments and introduce cheap equipment (wet rotor pumps, brazed heat exchangers, etc.), which in 2-3 years will largely lose its properties or become completely unusable; at the same time, the operating costs for the repair and maintenance of equipment will increase sharply after 2-3 years and can be of the same order as the initial investment;

Spend a maximum of capital investments, introduce reliable expensive equipment (gasketed heat exchangers of proven companies, for example, Alfa-Laval, dry-rotor pumps with a frequency drive, reliable automation, etc.) and thereby significantly reduce their operating costs.

The choice is up to the consumer, but one must not forget that "the miser pays twice."

Summarizing the above, the following conclusions can be drawn:

1. In Khabarovsk, in the last 2-3 years, the process of transition from outdated "open" systems to modern "closed" heat supply systems with the introduction of energy-saving technologies has begun. However, in order to speed up this process and make it irreversible, it is necessary:

1.1. To break the psychology of Customers, designers, installers and operators, which consists in the following: it is easier and cheaper to implement outdated traditional schemes heat supply with one-pipe heating systems and elevator units that do not need maintenance and adjustment, than create additional pain and financial difficulties for yourself, moving to modern heat supply systems with automation and control systems. That is, to build an object with a minimum of capital expenditures, then transfer it, for example, to the municipality, which will have to look for funds for the operation of this object. As a result, the consumer (citizen) will again be extreme, who will consume "rusty" water from the heating system, freeze from underflood in winter and suffer from heat during the transition period (October, April) during overheating, carrying out window regulation, which leads to colds due to drafts.

1.2. Create specialized organizations that would deal with the entire chain: from design and installation to commissioning and maintenance of modern heat supply systems. For this purpose, it is necessary to carry out purposeful work on the training of specialists in the field of energy saving.

2. When designing these systems, it is necessary to closely link together all the elements of heat supply systems: heating, ventilation and hot water supply, taking into account not only the requirements of SNiPs and SP, but also considering them from an angle from the point of view of operators.

3. Unlike outdated, traditional systems, modern systems require maintenance that can only be carried out by specialized organizations that have special equipment and highly qualified specialists.

BIBLIOGRAPHY

1. On the practice of using two-pipe heating systems. Inzhenernye sistemy. ABOK. North-West, No. 3, 2002

2. Lebedev of hydraulics of HVAC systems // AVOK, No. 5, 2002.

3. Ivanov of operation of plate heaters in the conditions of St. Petersburg // News of heat supply, No. 5, 2003.

Energy saving in heat supply systems

Completed: students of group T-23

Salazhenkov M.Yu

D.

Introduction

Today, the energy conservation policy is a priority area for the development of energy and heat supply systems. In fact, at every state enterprise, plans for energy conservation and energy efficiency improvement of enterprises, workshops, etc. are drawn up, approved and implemented.

The country's heating system is no exception. It is quite large and cumbersome, consumes colossal amounts of energy and, at the same time, there are no less colossal losses of heat and energy.

Let us consider what the heat supply system is, where the greatest losses occur, and what complexes of energy-saving measures can be used to increase the "efficiency" of this system.

Heat supply systems

Heat supply - the supply of heat to residential, public and industrial buildings (structures) to ensure utility (heating, ventilation, hot water supply) and technological needs of consumers.

In most cases, heating is about creating a comfortable indoor environment - at home, at work or in a public place. Heat supply also includes heating tap water and water in swimming pools, heating greenhouses, etc.

The distance over which heat is transported in modern district heating systems reaches several tens of kilometers. The development of heat supply systems is characterized by an increase in the capacity of the heat source and the unit capacity of the installed equipment. Thermal power of modern CHPP reaches 2-4 Tcal / h, district boiler houses 300-500 Gcal / h. In some heat supply systems, several heat sources work together for common heating networks, which increases the reliability, maneuverability and efficiency of heat supply.

The water heated in the boiler room can circulate directly in the heating system. Hot water is heated in a heat exchanger of the hot water supply system (DHW) to a lower temperature, of the order of 50–60 ° С. The return water temperature can be an important factor in the protection of the boiler. The heat exchanger not only transfers heat from one circuit to another, but also effectively copes with the pressure difference that exists between the first and second circuits.

The required underfloor heating temperature (30 ° C) can be obtained by adjusting the temperature of the circulating hot water. The temperature difference can also be achieved by using a three-way valve mixing hot water with return in the system.

Regulation of heat supply in heat supply systems (daily, seasonal) is carried out both in the heat source and in heat-consuming installations. In water heat supply systems, the so-called central quality control of heat supply is usually carried out according to the main type of heat load - heating or by a combination of two types of load - heating and hot water supply. It consists in changing the temperature of the coolant supplied from the heat supply source to the heating network in accordance with the adopted temperature schedule (that is, the dependence of the required water temperature in the network on the outside air temperature). Central quality regulation is complemented by local quantitative regulation in heating points; the latter is most common in hot water applications and is usually automatic. In steam heating systems, local quantitative regulation is mainly carried out; steam pressure in the heat supply source is kept constant, steam consumption is regulated by consumers.

1.1 Composition of the heat supply system

The heat supply system consists of the following functional parts:

1) a source of thermal energy production (boiler house, CHP, solar collector, devices for utilization of industrial thermal waste, installations for using heat from geothermal sources);

2) transporting devices of thermal energy to the premises (heating networks);

3) heat-consuming devices that transfer thermal energy to the consumer (heating radiators, air heaters).

1.2 Classification of heat supply systems

At the place of heat generation, heat supply systems are divided into:

1) centralized (the source of heat energy production works for heat supply of a group of buildings and is connected by transport devices with heat consumption devices);

2) local (the consumer and the heat supply source are in the same room or in the immediate vicinity).

The main advantages of district heating over local heating are a significant reduction in fuel consumption and operating costs (for example, due to the automation of boiler plants and an increase in their efficiency); the possibility of using low-grade fuel; reducing the degree of air pollution and improving the sanitary condition of populated areas. In local heating systems, heat sources are ovens, hot water boilers, water heaters (including solar), etc.

By the type of coolant, heat supply systems are divided into:

1) water (with temperatures up to 150 ° С);

2) steam (under a pressure of 7-16 atm).

Water is mainly used to cover municipal and household loads, and steam is used to cover technological loads. The choice of temperature and pressure in heating systems is determined by consumer requirements and economic considerations. With an increase in the distance of heat transportation, an economically justified increase in the parameters of the coolant increases.

According to the method of connecting the heating system to the heat supply system, the latter are divided into:

1) dependent (coolant heated in a heat generator and transported through heating networks goes directly to heat-consuming devices);

2) independent (the coolant circulating through the heating networks in the heat exchanger heats the coolant circulating in the heating system). (Fig. 1)

IN independent systems consumer installations are hydraulically isolated from the heating network. Such systems are used mainly in large cities - in order to increase the reliability of heat supply, as well as in cases where the pressure mode in the heating network is unacceptable for heat-consuming installations due to the conditions of their strength, or when the static pressure created by the latter is unacceptable for the heating network ( such are, for example, heating systems for high-rise buildings).

Figure 1 - Schematic diagrams of heat supply systems by the method of connecting heating systems to them

By the method of connecting the hot water supply system to the heat supply system:

1) closed;

2) open.

In closed systems, hot water supply is supplied with water from the water supply system, heated to the required temperature with water from the heating network in heat exchangers installed in heat points. In open systems, water is supplied directly from the heating network (direct water intake). Water leakage due to leaks in the system, as well as its consumption for water intake are compensated for by additional supply of an appropriate amount of water to the heating network. To prevent corrosion and scale formation on the inner surface of the pipeline, the water supplied to the heating network undergoes water treatment and deaeration. In open systems, the water must also meet the drinking water requirements. The choice of the system is mainly determined by the availability of a sufficient amount of potable water, its corrosive and scale-forming properties. Systems of both types have become widespread in Ukraine.

By the number of pipelines used to transfer the coolant, heat supply systems are distinguished:

one-pipe;

two-pipe;

multi-pipe.

One-pipe systems are used in cases where the heat carrier is fully used by consumers and does not return back (for example, in steam systems without condensate return and in open water systems, where all water coming from the source is disassembled for hot water supply to consumers).

In two-pipe systems, the coolant is fully or partially returned to the heat source, where it is heated and replenished.

Multi-pipe systems are arranged when it is necessary to separate certain types of heat load (for example, hot water supply), which simplifies the regulation of heat supply, the mode of operation and methods of connecting consumers to heating networks. In Russia, two-pipe heat supply systems are predominantly used.

1.3 Types of heat consumers

Heat consumers of the heat supply system are:

1) heat-using sanitary-technical systems of buildings (heating, ventilation, air conditioning, hot water supply systems);

2) technological installations.

The use of heated water for space heating is quite common. At the same time, a variety of methods of transferring water energy are used to create a comfortable indoor environment. One of the most common is the use of heating radiators.

An alternative to radiators is underfloor heating when the heating circuits are located under the floor. The underfloor heating circuit is usually connected to the heating radiator circuit.

Ventilation - A fan coil unit that supplies hot air to a room, typically used in public buildings. Combinations of heating devices are often used, such as radiators for heating and underfloor heating or radiators for heating and ventilation.

Hot tap water has become a part of daily life and daily necessities. Therefore, a hot water installation must be reliable, hygienic and economical.

According to the mode of heat consumption during the year, two groups of consumers are distinguished:

1) seasonal, requiring heat only in the cold season (for example, heating systems);

2) year-round, requiring heat all year round (hot water supply systems).

Depending on the ratio and modes of individual types of heat consumption, three characteristic groups of consumers are distinguished:

1) residential buildings (seasonal heat consumption for heating and ventilation is typical and year-round consumption for hot water supply);

2) public buildings (seasonal heat consumption for heating, ventilation and air conditioning);

3) industrial buildings and structures, including agricultural complexes (all types of heat consumption, the quantitative ratio between which is determined by the type of production).

2 District heating

District heating is an environmentally friendly and reliable way to provide heat. District heating systems distribute hot water or, in some cases, steam from a central boiler room between numerous buildings. There is a wide variety of sources that are used to generate heat, including the burning of oil and natural gas or the use of geothermal waters. The use of heat from low-temperature sources, such as geothermal heat, is possible with the use of heat exchangers and heat pumps. The possibility of using unrecovered heat from industrial enterprises, surplus heat from waste processing, industrial processes and sewerage, targeted heating plants or thermal power plants in district heating, allows for the optimal choice of a heat source in terms of energy efficiency. This way you optimize costs and protect the environment.

Hot water from the boiler room is fed to a heat exchanger, which separates the production site from the distribution pipelines of the district heating network. The heat is then distributed among the end users and supplied through the substations to the respective buildings. Each of these substations usually includes one heat exchanger for space heating and one for hot water supply.

There are several reasons for installing heat exchangers to separate the heating plant and the district heating network. Where significant pressure and temperature differences exist that can cause serious damage to equipment and property, the heat exchanger can prevent contaminated or corrosive media from entering sensitive heating and ventilation equipment. Another important reason for separating the boiler house, distribution network and end users is the clear definition of the functions of each component of the system.

In a combined heat and power plant (CHP), heat and electricity are produced simultaneously, with heat as a by-product. Heat is commonly used in district heating systems, leading to increased energy efficiency and economy. The degree of utilization of energy obtained from fuel combustion will be 85–90%. The efficiency will be 35–40% higher than in the case of separate heat and power generation.

In a CHP plant, the combustion of fuel heats up the water, which turns into high pressure and high temperature steam. The steam drives a turbine connected to a generator that produces electricity. After the turbine, the steam is condensed in a heat exchanger. The heat released during this process is then fed into the district heating pipes and distributed among the end users.

For the end user, district heating means uninterrupted energy supply. District heating is more convenient and efficient than small individual home heating systems. Modern technologies combustion of fuels and purification of emissions reduce the negative impact on the environment.

In apartment buildings or other buildings heated by central heating points, the main requirement is heating, hot water supply, ventilation and floor heating for a large number of consumers with minimal energy consumption. By using quality equipment in the heating system, you can reduce your overall costs.

Another very important task of heat exchangers in district heating is to ensure the safety of the internal system by separating the end users from the distribution network. This is necessary due to the significant differences in temperature and pressure. In the event of an accident, the risk of flooding can also be minimized.

In central heating points, there is often a two-stage connection scheme for heat exchangers (Fig. 2, A). This connection means maximum heat utilization and a low return water temperature when using a hot water system. It is especially advantageous when operating in a combined heat and power plant where a low return water temperature is desired. This type of substation can easily provide heat supply for up to 500 apartments, and sometimes more.

A) Two-stage connection B) Parallel connection

Figure 2 - Connection diagram of heat exchangers

Parallel connection of a DHW heat exchanger (Fig. 2, B) is less complicated than a two-stage connection, and can be used for any size of installation that does not need a low return water temperature. Such a connection is usually used for small and medium-sized substations with a load of up to approximately 120 kW. Connection diagram for hot water heaters in accordance with SP 41-101-95.

Most district heating systems place high demands on the installed equipment. The equipment must be reliable and flexible, providing the necessary safety. In some systems, it must also meet very high hygiene standards. Another important factor in most systems is low operating costs.

However, in our country, the district heating system is in a deplorable state:

the technical equipment and the level of technological solutions in the construction of heating networks correspond to the state of the 1960s, while the radii of heat supply increased sharply, and there was a transition to new standard sizes of pipe diameters;

the quality of the metal of heat pipes, thermal insulation, shut-off and control valves, structures and laying of heat pipes is significantly inferior to foreign counterparts, which leads to large losses of heat energy in the networks;

poor conditions for thermal insulation of heat pipelines and channels of heating networks contributed to an increase in the damageability of underground heat pipelines, which led to serious problems of replacing equipment in heating networks;

the domestic equipment of large CHPPs corresponds to the average foreign level of the 1980s, and at present steam turbine CHPPs are characterized by a high accident rate, since almost half of the installed turbine capacity has exhausted its design life;

operating coal-fired CHPPs do not have systems for cleaning flue gases from NOx and SOx, and the efficiency of collecting solid particles often does not reach the required values;

the competitiveness of SCT at the present stage can only be ensured by the introduction of specially new technical solutions, both in the structure of systems and in schemes, equipment of energy sources and heating networks.

2.2 Efficiency of district heating systems

One of the most important conditions for the normal operation of the heat supply system is the creation of a hydraulic regime that provides pressure in the heating network sufficient to create heating water flow rates in heat-consuming installations in accordance with a given heat load. The normal operation of heat consumption systems is the essence of providing consumers with heat energy of an appropriate quality, and for the energy supplying organization it is to maintain the parameters of the heat supply mode at the level regulated by the Rules of Technical Operation (PTE) of power plants and networks of the Russian Federation, PTE of thermal power plants. The hydraulic regime is determined by the characteristics of the main elements of the heat supply system.

During operation in the existing centralized heat supply system due to a change in the nature of the heat load, the connection of new heat consumers, an increase in the roughness of pipelines, an adjustment of the design temperature for heating, a change in the temperature schedule for the supply of thermal energy (FC) from the FC source, as a rule, an uneven heat supply occurs. to consumers, overestimation of network water costs and a reduction in the throughput of pipelines.

In addition to this, there are usually problems in heat-consuming systems. Such as, misalignment of heat consumption regimes, understaffing of elevator units, unauthorized violation by consumers of connection schemes (established by projects, technical conditions and contracts). The indicated problems of heat consumption systems are manifested, first of all, in the deregulation of the entire system, characterized by increased flow rates of the coolant. As a result, there are insufficient (due to increased pressure losses) available pressure of the coolant at the inputs, which in turn leads to the desire of subscribers to provide the necessary difference by draining the network water from the return pipelines to create at least minimal circulation in heating devices (violation of connection schemes and etc.), which leads to an additional increase in flow rate and, consequently, to additional pressure losses, and to the emergence of new subscribers with reduced pressure drops, etc. There is a "chain reaction" in the direction of total misalignment of the system.

All this has a negative impact on the entire heat supply system and on the activities of the energy supplying organization: inability to comply with the temperature schedule; increased recharge of the heat supply system, and when the capacity of water treatment is depleted - forced replenishment of raw water (as a result - internal corrosion, premature failure of pipelines and equipment); forced increase in the supply of heat energy to reduce the number of complaints from the population; increase in operating costs in the system of transport and distribution of heat energy.

It is necessary to point out that in the heat supply system there is always a relationship between the steady-state thermal and hydraulic regimes. A change in the flow distribution (its absolute value inclusive) always changes the heat exchange condition, both directly at heating installations and in heat consumption systems. The result of abnormal operation of the heat supply system is, as a rule, heat return network water.

It should be noted that the temperature of the return network water at the source of thermal energy is one of the main operating characteristics intended for analyzing the state of the equipment of heating networks and operating modes of the heat supply system, as well as for assessing the effectiveness of measures taken by organizations operating heating networks in order to increase the level operation of the heat supply system. As a rule, in case of misalignment of the heat supply system, the actual value of this temperature significantly differs from its standard value calculated for the given heat supply system.

Thus, when the heat supply system is out of adjustment, the temperature of the network water, as one of the main indicators of the mode of supply and consumption of heat energy in the heat supply system, turns out to be: in the supply pipeline, in almost all intervals of the heating season, it is characterized by reduced values; the temperature of the return water supply, in spite of this, is characterized by increased values; the temperature difference in the supply and return pipelines, namely, this indicator (along with the specific consumption of network water for the connected heat load) characterizes the level of quality of heat energy consumption, is underestimated in comparison with the required values.

One more aspect should be noted, associated with an increase in relation to the calculated value of the flow rate of network water for the thermal regime of heat consumption systems (heating, ventilation). For direct analysis, it is advisable to use the dependence, which determines, in case of deviation of the actual parameters and structural elements of the heat supply system from the calculated ones, the ratio of the actual consumption of heat energy in heat consumption systems to its calculated value.

where Q is the consumption of heat energy in heat consumption systems;

g is the flow of heating water;

tп and tо - temperature in the supply and return pipelines.

This dependence (*) is shown in Fig. 3. The ordinate shows the ratio of the actual consumption of thermal energy to its calculated value, and the abscissa shows the ratio of the actual consumption of heating water to its calculated value.

Figure 3 - Graph of dependence of heat energy consumption by systems

heat consumption from the consumption of network water.

As general tendencies, it is necessary to point out that, firstly, an increase in the consumption of network water by n times does not cause an increase in the consumption of thermal energy corresponding to this number, that is, the coefficient of heat consumption lags behind the coefficient of consumption of network water. Secondly, with a decrease in the consumption of heating water, the supply of heat to the local heat consumption system decreases the faster, the lower the actual consumption of heating water in comparison with the calculated one.

Thus, heating and ventilation systems react very weakly to the overrun of supply water. Thus, an increase in the consumption of heating water for these systems relative to the calculated value by 50% causes an increase in heat consumption by only 10%.

The point in Fig. 3 with coordinates (1; 1) displays the calculated, actually achievable mode of operation of the heat supply system after carrying out adjustment measures. The actually achievable mode of operation means such a mode, which is characterized by the existing position of the structural elements of the heat supply system, heat losses of buildings and structures and determined by the total consumption of network water at the terminals of the heat energy source, which is necessary to provide a given heat load with the existing schedule of heat energy supply.

It should also be noted that the increased consumption of network water, due to the limited value of the throughput of heating networks, leads to a decrease in the values ​​of the available pressures at the inputs of consumers necessary for the normal operation of heat-consuming equipment. It should be noted that the pressure losses through the heating network are determined by the quadratic dependence on the flow rate of the heating network:

That is, with an increase in the actual flow rate of network water GF by 2 times relative to the calculated value of GР, the pressure losses through the heating network increase by 4 times, which can lead to unacceptably small available pressures at the heating units of consumers and, consequently, to insufficient heat supply to these consumers, which can cause unauthorized drainage of network water to create circulation (unauthorized violation by consumers of connection schemes, etc.)

Further development of such a heat supply system along the path of increasing the flow rate of the coolant, firstly, will require replacement of the head sections of heat pipelines, additional installation of network pumping units, an increase in the productivity of water treatment, etc., and secondly, it leads to an even greater increase in additional costs - the cost of compensation of electricity, make-up water, heat losses.

Thus, the development of such a system seems to be technically and economically more justified by improving its quality indicators - increasing the temperature of the coolant, pressure drops, increasing the temperature difference (heat removal), which is impossible without a dramatic reduction in the flow rate of the coolant (circulation and recharge) in heat consumption systems and , respectively, in the entire heat supply system.

Thus, the main measure that can be proposed to optimize such a heat supply system is the adjustment of the hydraulic and thermal regime of the heat supply system. The technical essence of this measure is to establish the flow distribution in the heat supply system based on the calculated (i.e., corresponding to the connected heat load and the selected temperature schedule) flow rates of network water for each heat consumption system. This is achieved by installing appropriate throttling devices (autoregulators, throttling washers, elevator nozzles) at the inputs to the heat consumption systems, the calculation of which is based on the calculated pressure difference at each input, which is calculated based on the hydraulic and thermal calculation of the entire heat supply system.

It should be noted that the creation of a normal mode of operation of such a heat supply system is not limited only to carrying out adjustment measures, it is also necessary to carry out work to optimize the hydraulic mode of the heat supply system.

Regime adjustment covers the main links of the centralized heat supply system: a water heating installation of a heat source, central heating points (if any), a heating network, control and distribution points (if any), individual heating points and local heat consumption systems.

The commissioning begins with a survey of the district heating system. The collection and analysis of initial data on the actual operating modes of the transport and distribution system of heat energy, information on the technical condition of heating networks, the degree of equipment of the heat source, heating networks and subscribers with commercial and technological measuring instruments is carried out. The applied modes of heat energy supply are analyzed, possible design and installation defects are identified, information is selected to analyze the characteristics of the system. The analysis of operational (statistical) information (sheets of accounting for the parameters of the coolant, modes of supply and consumption of energy, actual hydraulic and thermal modes of heating networks) is carried out at various values ​​of the outside air temperature in base periods, obtained according to the readings of standard measuring devices, and the analysis of reports of specialized organizations is carried out. ...

At the same time, a design scheme for heating networks is being developed. A mathematical model of the heat supply system is being created on the basis of the ZuluThermo calculation complex, developed by Polyterm (St. Petersburg), capable of simulating the actual thermal and hydraulic operation of the heat supply system.

It is necessary to point out that there is a fairly widespread approach, which consists in the maximum reduction of financial costs associated with the development of measures for the adjustment and optimization of the heat supply system, namely, the costs are limited to the acquisition of a specialized software package.

The “pitfall” in this approach is the reliability of the initial data. The mathematical model of the heat supply system, created on the basis of unreliable initial data on the characteristics of the main elements of the heat supply system, turns out to be, as a rule, inadequate to reality.

2.3 Energy Saving in DH Systems

Recently, there have been critical remarks about district heating based on cogeneration - the joint production of heat and electricity. As the main disadvantages, there are large heat losses in pipelines during heat transport, a decrease in the quality of heat supply due to non-observance of the temperature schedule and the required pressure from consumers. It is proposed to switch to decentralized, autonomous heat supply from automated boiler houses, including those located on the roofs of buildings, justifying this by the lower cost and the absence of the need to lay heat pipelines. But at the same time, as a rule, it is not taken into account that connecting the heat load to the boiler house makes it impossible to generate cheap electricity based on heat consumption. Therefore, this part of the non-generated electricity must be replaced by its production according to the condensation cycle, the efficiency of which is 2-2.5 times lower than that of the heating cycle. Consequently, the cost of electricity consumed by a building, which is supplied with heat from the boiler house, must be higher than that of a building connected to a district heating system, and this will cause a sharp increase in operating costs.

S. A. Chistovich at the jubilee conference "75 years of district heating in Russia", held in Moscow in November 1999, proposed that house boiler houses supplement centralized heat supply, acting as peak heat sources, where the lack of network capacity does not allow for high-quality supply warmth of consumers. At the same time, district heating is preserved and the quality of heat supply improves, but this decision blows away with stagnation and hopelessness. It is essential that the district heating supply fully fulfills its functions. After all, district heating has its own powerful peak boiler houses, and it is obvious that one such boiler house will be more economical than hundreds of small ones, and if the capacity of the networks is insufficient, then it is necessary to shift the networks or cut off this load from the networks so that it does not disrupt the quality of heat supply to other consumers.

Denmark has achieved great success in district heating, which, despite the low concentration of heat load per 1 m2 of surface area, is ahead of us in terms of per capita heating coverage. Denmark has a special government policy to preferentially connect new heat consumers to district heating. In West Germany, for example in Mannheim, district heating based on district heating is developing rapidly. In the Eastern Lands, where, focusing on our country, district heating was also widely used, despite the abandonment of panel housing construction, from central heating stations in residential neighborhoods that turned out to be ineffective in the conditions of a market economy and a Western lifestyle, the area of ​​centralized heat supply based on district heating continues to develop as the most environmentally friendly and cost effective.

All of the above indicates that at the new stage we must not lose our leading positions in the field of district heating, and for this it is necessary to modernize the district heating system in order to increase its attractiveness and efficiency.

All the advantages of the combined generation of heat and electricity were attributed to the electricity side, the centralized heat supply was financed on a leftover basis - sometimes the CHPP had already been built, and the heating networks had not yet been connected. As a result, low quality heat pipelines with poor insulation and ineffective drainage were created, the connection of heat consumers to heating networks was carried out without automatic load control, at best with the use of hydraulic regulators for stabilizing the flow rate of the heat carrier of very low quality.

This forced the supply of heat from the source according to the method of central quality control (by changing the temperature of the coolant depending on the outside temperature according to a single schedule for all consumers with constant circulation in the networks), which led to a significant waste of heat by consumers due to differences in their operating mode and impossibility of joint operation of several heat sources on a single network for mutual redundancy. The absence or ineffectiveness of the regulation devices at the points of connection of consumers to heating networks also caused an overrun of the volume of the coolant. This led to an increase in the return water temperature to such an extent that there was a danger of failure of station circulation pumps and this forced to reduce the heat supply at the source, disrupting the temperature schedule even in conditions of sufficient power.

Unlike us, in Denmark, for example, all the benefits of district heating in the first 12 years are given to the side of thermal energy, and then divided in half with electrical energy. As a result, Denmark was the first country to manufacture pre-insulated ductless pipes with a sealed cover layer and automatic system leak detection, which dramatically reduced heat loss during transportation. In Denmark, for the first time, silent, unsupported wet-running circulation pumps, heat metering devices and effective systems for automatic regulation of heat load were invented, which made it possible to construct automated individual heating points (ITPs) directly in the buildings of consumers with automatic regulation of the supply and metering of heat in its places. use.

The universal automation of all heat consumers made it possible to: abandon the high-quality method of central regulation at the heat source, which causes unwanted temperature fluctuations in the pipelines of the heating network; reduce the maximum parameters of water temperature to 110-1200C; to ensure the possibility of operation of several heat sources, including incinerators, on a single network with the most efficient use of each.

The water temperature in the supply pipeline of heating networks changes depending on the level of the established outside air temperature in three stages: 120-100-80 ° C or 100-85-70 ° C (there is a tendency for an even greater decrease in this temperature). And inside each stage, depending on the change in the load or the deviation of the outside temperature, the flow rate of the coolant circulating in the heating networks changes according to the signal of the fixed value of the pressure difference between the supply and return pipelines - if the pressure difference drops below the set value, then the subsequent heat-generating and pumping stations are switched on at the stations. installation. Heat supply companies guarantee each consumer a predetermined minimum level of pressure drop in the supply networks.

Consumers are connected through heat exchangers, and, in our opinion, an excessive number of connection steps is used, which is apparently caused by the boundaries of property ownership. So, the following connection scheme was demonstrated: to the main grids with design parameters of 125 ° C, which are under the jurisdiction of the energy producer, through a heat exchanger, after which the water temperature in the supply pipeline drops to 120 ° C, municipally owned distribution networks are connected.

The level of maintaining this temperature is set by an electronic regulator acting on a valve installed on the return pipe of the primary circuit. In the secondary circuit, the circulation of the coolant is carried out by pumps. The connection to these distribution networks of local heating and hot water supply systems of individual buildings is carried out through independent heat exchangers installed in the basements of these buildings with a full set of heat control and metering devices. Moreover, the regulation of the temperature of the water circulating in the local heating system is carried out according to the schedule, depending on the change in the outside air temperature. Under design conditions, the maximum water temperature reaches 95 ° C, recently there has been a tendency to decrease it to 75-70 ° C, the maximum value of the return water temperature is 70 and 50 ° C, respectively.

Connection of heating points of individual buildings is carried out according to standard schemes with parallel connection of a hot water storage tank or according to a two-stage scheme using the potential of the heat carrier from the return pipe after the heating water heater using high-speed hot water heat exchangers, while it is possible to use a pressure storage tank for hot water with a pump for charging the tank. In the heating circuit, pressure membrane tanks are used to collect water when it expands from heating; in our country, atmospheric expansion tanks installed at the top of the system are more used.

To stabilize the operation of the control valves at the inlet to the substation, a hydraulic constant pressure regulator is usually installed. And to bring heating systems with pump circulation to the optimal operating mode and to facilitate the distribution of the coolant along the risers of the system - a "partner valve" in the form of a balance valve, which allows setting the correct flow rate of the circulating coolant according to the pressure loss measured on it.

In Denmark, they do not pay special attention to an increase in the estimated flow rate of the heat carrier at a heating point when heating water for domestic needs is turned on. In Germany, it is legally forbidden to take into account the load on the hot water supply when selecting the heat output, and when automating heat points, it is assumed that when the hot water heater is turned on and when the storage tank is filled, the pumps that provide circulation in the heating system are turned off, i.e. the heat supply to the heating system is stopped. heating.

In our country, serious importance is also attached to preventing an increase in the power of the heat source and the estimated flow rate of the coolant circulating in the heating network during the hours of the maximum hot water supply. But the decision made in Germany for this purpose cannot be applied in our conditions, since we have a significantly higher ratio of loads of hot water supply and heating, due to the large value of the absolute consumption of domestic water and the higher population density.

Therefore, when automating heat points of consumers, a limitation of the maximum flow of water from the heating network is applied when the set value is exceeded, determined based on the average hourly load of hot water supply. When supplying heat to residential areas, this is done by closing the valve of the regulator of heat supply for heating during the hours when the maximum water consumption passes. By setting the heating regulator to a certain overestimation of the maintained schedule of the coolant temperature, the underheating in the heating system that occurs when the maximum of the watershed is passed is compensated during periods of water withdrawal below average (within the specified flow rate of water from the heating network - associated regulation).

The water flow sensor, which is a signal for limiting, is a water flow meter included in the set of a heat meter installed at the input of the heating network in the central heating station or ITP. The inlet differential pressure regulator cannot serve as a flow limiter, since it provides a predetermined pressure differential under conditions of full opening of the heating and hot water supply regulator valves installed in parallel.

With the aim of increasing the efficiency of the joint generation of heat and electric energy and leveling the maximum energy consumption in Denmark, thermal accumulators, which are installed at the source, are widely used. The lower part of the accumulator is connected to the return pipe of the heating network, the upper part through a movable diffuser with a supply pipe. When the circulation in the distribution heating networks is reduced, the tank is charged. With an increase in circulation, the excess flow rate of the coolant from the return pipeline enters the tank, and hot water is squeezed out of it. The need for heat accumulators increases in CHPPs with back pressure turbines, in which the ratio of the generated electric and thermal energy is fixed.

If the design temperature of the water circulating in the heating networks is below 100 ° C, then atmospheric storage tanks are used; at a higher design temperature, pressure is created in the tanks, which ensures that hot water does not boil.

However, the installation of thermostats together with heat flow meters for each heater leads to an almost double increase in the cost of the heating system, and in a one-pipe scheme, in addition, the required heating surface of the devices increases to 15% and there is a significant residual heat transfer from the devices in the closed position of the thermostat, which reduces the effectiveness of auto-regulation. Therefore, an alternative to such systems, especially in inexpensive municipal construction, are systems for frontal automatic heating control - for extended buildings and central ones with correction of the temperature schedule based on the deviation of the air temperature in the prefabricated exhaust ventilation ducts from the kitchens of apartments - for point buildings or buildings with a complex configuration.

However, it must be borne in mind that during the reconstruction of existing residential buildings for the installation of thermostats, it is necessary to enter each apartment with welding. At the same time, when organizing frontal auto-regulation, it is enough to embed jumpers between the frontal branches of sectional heating systems in the basement and in the attic, and for 9-storey attic buildings of mass construction of the 60-70s - only in the basement.

It should be noted that new construction per year does not exceed 1-2% of the existing housing stock in terms of volume. This demonstrates the importance of the reconstruction of existing buildings in order to reduce the cost of heat for heating. However, it is impossible to automate all buildings at once, and in conditions when several buildings are automated, real savings are not achieved, since the coolant saved on automated facilities is redistributed between non-automated ones. The aforementioned confirms once again that it is necessary to construct the IAC at an advanced pace on the existing heating networks, since it is much easier to automate simultaneously all buildings powered by one IAC than from a CHP, and other already created IACs will not let an excess amount of coolant into their distribution networks.

All of the above does not exclude the possibility of connecting individual buildings to boiler houses with an appropriate feasibility study with an increase in the tariff for consumed electricity (for example, when it is necessary to lay or relocate a large number of networks). But in the conditions of the existing system of centralized heat supply from CHPPs, this should be of a local nature. The possibility of using heat pumps, transferring part of the load to the CCGT and GTU is not excluded, but given the current conjuncture of prices for fuel and energy resources, this is not always profitable.

Heat supply of residential buildings and microdistricts in our country, as a rule, is carried out through group heating points (CHP), after which individual buildings are supplied through independent pipelines with hot water for heating and domestic needs with tap water heated in heat exchangers installed in the CHP. Sometimes up to 8 heat pipelines leave the central heating station (with a 2-zone hot water supply system and a significant ventilation load), and although galvanized hot water supply pipelines are used, due to the lack of chemical water treatment, they undergo intense corrosion and after 3-5 years of operation on them fistulas appear.

Currently, in connection with the privatization of housing and service enterprises, as well as with the rise in the cost of energy carriers, the transition from group heating points to individual heating points (ITPs) located in a heated building is relevant. This makes it possible to apply a more efficient system of frontal automatic heating control for extended buildings or a central one with correction for the internal air temperature in point buildings, allows you to abandon hot water distribution networks, reducing heat losses during transportation and energy consumption for pumping domestic hot water. Moreover, it is advisable to do this not only in new construction, but also in the reconstruction of existing buildings. There is such an experience in the Eastern Lands of Germany, where, just like ours, central heating stations were built, but now they are left only as pumping water supply stations (if necessary), and heat exchange equipment, together with circulation pumps, regulation and metering units, are transferred to the ITP of buildings ... Intra-quarter networks are not laid, hot water supply pipelines are left in the ground, and heating pipelines, as more durable, are used to supply overheated water to buildings.

To increase the controllability of heating networks, to which a large number of ITPs will be connected, and to ensure the possibility of redundancy in automatic mode, it is necessary to return to the device of control and distribution points (KRP) at the points of connection of distribution networks to the main ones. Each KRP is connected to the mains on both sides of the sectional valves and serves consumers with a heat load of 50-100 MW. In the KRP, switching electric valves are installed at the inlet, pressure regulators, circulation-mixing pumps, a temperature regulator, safety valve, heat and coolant metering devices, control and telemechanics devices.

The control valve automation scheme ensures that the pressure is maintained at a constant minimum level in the return line; maintaining a constant set pressure drop in the distribution network; reduction and maintenance of the water temperature in the supply pipeline of the distribution network according to a given schedule. As a result, in the redundancy mode, it is possible to supply a reduced amount of circulating water with an increased temperature through the mains from the CHP without disturbing the temperature and hydraulic regimes in the distribution networks.

KRP should be located in ground pavilions, they can be blocked with water pumping stations (this will allow in most cases to abandon the installation of high-pressure, and therefore noisier pumps in buildings), and can serve as the boundary of the balance of the heat-release organization and the heat-distributing (the next boundary between the heat-distributing and the heat-using organizations will be the wall of the building). Moreover, the KRP should be under the jurisdiction of the heat supply organization, since they serve to control and reserve the main networks and provide the ability to operate several heat sources for these networks, taking into account the maintenance of the coolant parameters set by the heat distribution organization at the exit from the KRP.

The correct use of the coolant by the heat consumer is ensured by the use of effective control automation systems. Now there are a large number of computer systems that can perform any control task of any complexity, but technological tasks and circuit solutions for connecting heat consumption systems remain decisive.

Recently, they began to build water heating systems with thermostats, which carry out individual automatic control of heat transfer from heating devices according to the air temperature in the room where the device is installed. Such systems are widely used abroad with the addition of the obligatory measurement of the amount of heat used by the device in shares of the total heat consumption by the building heating system.

In our country, in mass construction, such systems began to be used for elevator connection to heating networks. But the elevator is designed in such a way that with a constant nozzle diameter and the same available pressure, it passes a constant flow rate of the coolant through the nozzle, regardless of the change in the flow rate of water circulating in the heating system. As a result, in 2-pipe heating systems, in which the thermostats, by closing, lead to a reduction in the flow rate of the coolant circulating in the system, with the elevator connection, the water temperature in the supply pipe will rise, and then in the opposite direction, which will lead to an increase in heat transfer from the unregulated part of the system (risers) and to underutilization of the coolant.

In a one-pipe heating system with permanently acting closing sections, when the thermostats are closed, hot water is discharged into the riser without cooling, which also leads to an increase in the water temperature in the return pipeline and, due to the constant mixing ratio in the elevator, to an increase in the water temperature in the supply pipeline, and therefore to the same consequences as in a 2-pipe system. Therefore, in such systems, it is imperative to automatically control the water temperature in the supply pipeline according to the schedule, depending on the change in the outside air temperature. Such regulation is possible by changing the circuit solution for connecting the heating system to the heating network: replacing a conventional elevator with an adjustable one, using pump mixing with a control valve or by connecting it through a heat exchanger with pump circulation and a control valve on the heating system in front of the heat exchanger. [

3 DECENTRALIZED HEAT SUPPLY

3.1 Prospects for the development of decentralized heat supply

Earlier decisions on the closure of small boiler houses (under the pretext of their low efficiency, technical and environmental hazard) today turned out to be beyond the centralization of heat supply, when hot water passes 25-30 km from the CHP to the consumer, when the heat source is disconnected due to non-payment or emergency situation leads to the freezing of cities with a population of one million.

Most of the industrially developed countries followed a different path: they improved the heat-generating equipment, increasing the level of its safety and automation, the efficiency of gas-burner devices, sanitary, hygienic, environmental, ergonomic and aesthetic indicators; created a comprehensive energy accounting system for all consumers; brought the regulatory and technical base in line with the requirements of the expediency and convenience of the consumer; optimized the level of heat supply centralization; moved on to the widespread introduction of alternative sources of thermal energy. The result of this work was real energy saving in all spheres of the economy, including housing and communal services.

A gradual increase in the share of decentralized heat supply, the maximum approximation of the heat source to the consumer, accounting by the consumer of all types of energy resources will not only create more comfortable conditions for the consumer, but also provide real savings in gas fuel.

The modern system of decentralized heat supply is a complex set of functionally interconnected equipment, including an autonomous heat generating unit and engineering systems of the building (hot water supply, heating and ventilation systems). The main elements of the apartment heating system, which is a type of decentralized heat supply, in which each apartment in an apartment building is equipped with an autonomous heating and hot water supply system, are a heating boiler, heating devices, air supply and combustion products removal systems. Wiring is done using steel pipe or modern heat transfer systems - plastic or metal-plastic.

The system of centralized heat supply through CHP plants and main heat pipelines, traditional for our country, is known and has a number of advantages. But in the context of the transition to new economic mechanisms, the known economic instability and weakness of interregional, interdepartmental relations, many of the advantages of the district heating system turn into disadvantages.

The main one is the length of heating mains. The average percentage of wear is estimated at 60-70%. Specific damage to heat pipelines has now increased to 200 registered damages per year per 100 km of heating networks. According to an urgent assessment, at least 15% of heating networks require urgent replacement. In addition to this, over the past 10 years, as a result of underfunding, the main fund of the industry has practically not been renewed. As a result, heat losses during production, transportation and consumption reached 70%, which led to a low quality of heat supply at high costs.

The organizational structure of interaction between consumers and heat supply enterprises does not stimulate the latter to save energy resources. The system of tariffs and subsidies does not reflect the real costs of heat supply.

In general, the critical situation in which the industry finds itself presupposes the emergence of a large-scale crisis in the heat supply sector in the near future, the resolution of which will require colossal financial investments.

A pressing issue is a reasonable decentralization of heat supply, apartment heating. Decentralization of heat supply (DF) is the most radical, efficient and cheap way to eliminate many disadvantages. Justified use of diesel fuel in combination with energy-saving measures in the construction and reconstruction of buildings will give great savings in energy resources in Ukraine. In the current difficult conditions, the only way out is to create and develop a diesel fuel system through the use of autonomous heat sources.

Apartment heat supply is an autonomous provision of heat and hot water to an individual house or a separate apartment in a multi-storey building. The main elements of such autonomous systems are: heat generators - heating devices, heating and hot water supply pipelines, fuel supply, air and smoke removal systems.

The objective prerequisites for the introduction of autonomous (decentralized) heat supply systems are:

absence in some cases of free capacity at centralized sources;

the consolidation of the development of urban areas with housing objects;

in addition, a significant part of the development is located in areas with undeveloped engineering infrastructure;

lower capital investment and the possibility of phased coverage of thermal loads;

the ability to maintain comfortable conditions in the apartment in your own way on their own, which in turn is more attractive in comparison with apartments with centralized heat supply, the temperature in which depends on the directive decision on the beginning and end of the heating period;

the appearance on the market of a large number of various modifications of domestic and imported (foreign) heat generators of low power.

Today, modular boiler plants designed for the organization of an autonomous diesel fuel have been developed and are being serially produced. The block-modular construction principle makes it possible to easily build a boiler house of the required power. The absence of the need to lay heating mains and the construction of a boiler house reduces the cost of communications and significantly increases the pace of new construction. In addition, this makes it possible to use such boiler houses for the prompt provision of heat supply in emergency and emergency situations during the heating season.

Block boiler rooms are a fully functional finished product, equipped with all the necessary automation and safety devices. The level of automation ensures uninterrupted operation of all equipment without the constant presence of an operator.

Automation monitors the object's need for heat depending on weather conditions and independently regulates the operation of all systems to ensure the specified modes. This achieves better adherence to the heat schedule and additional fuel savings. In the event of emergency situations, gas leaks, the security system automatically cuts off the gas supply and prevents the possibility of accidents.

Many enterprises, oriented towards today's conditions and having calculated the economic benefit, are moving away from centralized heat supply, from remote and energy-intensive boiler houses.

The advantages of decentralized heating are:

no need for land allotments for heating networks and boiler houses;

reduction of heat losses due to the absence of external heating networks, reduction of network water losses, reduction of costs for water treatment;

significant reduction in the cost of repair and maintenance of equipment;

full automation of consumption modes.

If we take into account the lack of autonomous heating from small boiler houses and relatively low chimneys and, in connection with this, the violation of the environment, then a significant decrease in gas consumption associated with the dismantling of the old boiler house also reduces emissions by 7 times!

With all the advantages, decentralized heat supply also has negative aspects. In small boiler houses, including "roof" ones, the height of the chimneys is, as a rule, much lower than that of large ones, due to a sharp deterioration in the dispersion conditions. In addition, small boiler rooms are usually located near the residential area.

The introduction of programs for the decentralization of heat sources makes it possible to halve the need for natural gas and several times to reduce the cost of heat supply to end consumers. The principles of energy saving inherent in the existing heat supply system of Ukrainian cities stimulate the emergence of new technologies and approaches that can fully solve this problem, and the economic efficiency of diesel fuel makes this area very attractive for investment.

The use of an apartment-based heat supply system for multi-storey residential buildings makes it possible to completely eliminate heat losses in heating networks and during distribution between consumers, and significantly reduce losses at the source. It will allow organizing individual metering and regulation of heat consumption depending on economic opportunities and physiological needs. Apartment heating will lead to a decrease in one-time capital investments and operating costs, and also allows you to save energy and raw materials for the production of heat energy and, as a consequence, leads to a decrease in the load on the environmental situation.

The apartment heating system is an economically, energetically, environmentally efficient solution to the heat supply issue for multi-storey buildings. And yet, it is necessary to conduct a comprehensive analysis of the effectiveness of the use of a particular heat supply system, taking into account many factors.

Thus, the analysis of the components of losses in autonomous heat supply allows:

1) for the existing housing stock, increase the energy efficiency coefficient of heat supply to 0.67 versus 0.3 for centralized heat supply;

2) for new construction, only by increasing the thermal resistance of the enclosing structures, increase the energy efficiency of heat supply to 0.77 versus 0.45 with centralized heat supply;

3) when using the whole complex of energy-saving technologies, increase the coefficient to 0.85 against 0.66 with centralized heat supply.

3.2 Energy efficient diesel fuel solutions

With autonomous heat supply, you can use new technical and technological solutions, allowing to completely eliminate or significantly reduce all non-productive losses in the chain of generation, transportation, distribution and consumption of heat, and not just by building a mini-boiler house, but by the possibility of using new energy-saving and efficient technologies, such as:

1) transition to a fundamentally new system of quantitative regulation of heat generation and supply at the source;

2) effective use of a variable frequency drive on all pumping units;

3) reduction of the length of circulation heating networks and reduction of their diameter;

4) rejection of the construction of central heating points;

5) transition to a fundamentally new scheme of individual heating points with quantitative and qualitative regulation depending on the current outside air temperature using multi-speed mixing pumps and three-way control valves;

6) installation of a "floating" hydraulic regime of the heating network and complete rejection of hydraulic balancing of consumers connected to the network;

7) installation of regulating thermostats on heating devices in apartments;

8) apartment wiring of heating systems with the installation of individual heat consumption meters;

9) automatic maintenance of constant pressure on hot water supply devices for consumers.

The implementation of these technologies allows, first of all, to minimize all losses and creates conditions for the coincidence in time of the modes of the amount of generated and consumed heat.

3.3 Benefits of decentralized heating

If we trace the entire chain: source-transport-distribution-consumer, then the following can be noted:

1 Heat source - the allotment of land is significantly reduced, the construction part becomes cheaper (no foundations are required for the equipment). The installed capacity of the source can be chosen almost equal to the consumed one, while it is possible to ignore the load of hot water supply, since at the maximum it is compensated for by the accumulating capacity of the consumer's building. Today it is a reserve. The regulation scheme is being simplified and made cheaper. Heat losses are excluded due to the mismatch between the modes of production and consumption, the correspondence of which is established automatically. In practice, only the losses associated with the boiler unit efficiency remain. Thus, at the source it is possible to reduce losses by more than 3 times.

2 Heating networks - the length is reduced, diameters are reduced, the network becomes more maintainable. Constant temperature conditions increase the corrosion resistance of the pipe material. The amount of circulating water and its losses with leaks are reduced. There is no need to build a complex water treatment scheme. There is no need to maintain a guaranteed pressure drop before entering the consumer, and in this regard, there is no need to take measures for hydraulic balancing of the heating network, since these parameters are set automatically. Experts understand what a difficult problem it is - annually to make hydraulic calculations and perform work on hydraulic linking of a branched heating network. Thus, losses in heating networks are reduced by almost an order of magnitude, and in the case of a roof boiler house for one consumer, these losses are absent at all.

3 Distribution systems CHP and ITP. Necessary