What is the specific heat of combustion of gasoline? Fuel energy
(fig.14.1 - Calorific value
fuel ability)
Pay attention to the calorific value (specific heat of combustion) of different fuels, compare the indicators. The calorific value of the fuel characterizes the amount of heat released during the complete combustion of fuel with a mass of 1 kg or a volume of 1 m³ (1 l). Most often, the calorific value is measured in J / kg (J / m³; J / L). The higher the specific heat of combustion of the fuel, the lower its consumption. Therefore, the calorific value is one of the most significant characteristics of the fuel.
The specific heat of combustion of each type of fuel depends on:
- From its combustible components (carbon, hydrogen, volatile combustible sulfur, etc.).
- From its moisture and ash content.
| Table 4 - Specific heat of combustion of various energy sources, comparative analysis expenditures. | |||||||||
| Energy carrier type | Calorific value | Volumetric density of matter (ρ = m / V) | Unit price equivalent fuel | Coeff. useful action (Efficiency) of the system heating,% | Price per 1 kWh | Implemented systems | |||
| Mj | kWh | ||||||||
| (1MJ = 0.278kWh) | |||||||||
| Electricity | - | 1.0 kWh | - | 3.70 RUR per kWh | 98% | 3.78 RUR | Heating, hot water supply (DHW), air conditioning, cooking | ||
| Methane (CH4, temperature boiling point: -161.6 ° C) | 39.8 MJ / m³ | 11.1 kWh / m³ | 0.72 kg / m³ | 5.20 rub. per m³ | 94% | 0.50 rub. | |||
| Propane (C3H8, temperature boiling point: -42.1 ° C) | 46,34 MJ / kg | 23,63 MJ / L | 12,88 kWh / kg | 6,57 kWh / l | 0.51 kg / l | 18.00 rub. Hall | 94% | 2.91 RUR | Heating, hot water supply (DHW), food preparation, backup and constant power supply, autonomous septic tank (sewage), outdoor infrared heaters, outdoor barbecues, fireplaces, baths, designer lighting |
| Butane C4H10, temperature boiling point: -0.5 ° C) | 47,20 MJ / kg | 27,38 MJ / L | 13,12 kWh / kg | 7,61 kWh / l | 0.58 kg / l | 14.00 rub. Hall | 94% | 1.96 RUR | Heating, hot water supply (DHW), cooking, backup and constant power supply, autonomous septic tank (sewage), outdoor infrared heaters, outdoor barbecues, fireplaces, baths, designer lighting |
| Propane-butane (LPG - liquefied hydrocarbon gas) | 46,8 MJ / kg | 25,3 MJ / L | 13,0 kWh / kg | 7,0 kWh / l | 0.54 kg / l | 16.00 rub. Hall | 94% | 2.42 RUR | Heating, hot water supply (DHW), cooking, backup and constant power supply, autonomous septic tank (sewage), outdoor infrared heaters, outdoor barbecues, fireplaces, baths, designer lighting |
| Diesel fuel | 42,7 MJ / kg | 11,9 kWh / kg | 0.85 kg / l | RUB 30.00 per kg | 92% | 2.75 RUR | Heating (heating water and generating electricity are very expensive) | ||
| Firewood (birch, moisture - 12%) | 15,0 MJ / kg | 4,2 kWh / kg | 0.47-0.72 kg / dm³ | 3.00 rub. per kg | 90% | RUR 0.80 | Heating (inconvenient to prepare food, almost impossible to get hot water) | ||
| Coal | 22,0 MJ / kg | 6,1 kWh / kg | 1200-1500 kg / m³ | 7.70 rub. per kg | 90% | 1.40 RUR | Heating | ||
| MARP gas (mixture of LPG - 56% with methylacetylene propadiene - 44%) | 89,6 MJ / kg | 24,9 kWh / m³ | 0.1137 kg / dm³ | -R. per m³ | 0% | Heating, hot water supply (DHW), cooking, backup and constant power supply, autonomous septic tank (sewage), outdoor infrared heaters, outdoor barbecues, fireplaces, baths, designer lighting | |||
(fig. 14.2 - Specific heat of combustion)
According to the table "Specific calorific value of various energy carriers, comparative analysis of costs", propane-butane (liquefied petroleum gas) is inferior in economic benefits and prospects of using only natural gas (methane). However, attention should be paid to the tendency towards an inevitable increase in the cost of main gas, which is currently significantly underestimated. Analysts predict an imminent reorganization of the industry, which will lead to a significant rise in the price of natural gas, perhaps even exceed the cost of diesel fuel.
Thus, liquefied petroleum gas, the cost of which will practically not change, remains extremely promising - the optimal solution for autonomous gasification systems.
Humanity in the process of its evolution has learned to receive thermal energy by burning different types fuel. The simplest example is a firewood fire that was kindled by primitive people, and since then peat, coal, gasoline, oil, natural gas - all these are types of fuel, burning which a person receives thermal energy. So what is specific heat of combustion?
Where does the heat come from during combustion?
The combustion process itself is a chemical, oxidative reaction. Most fuels contain large amounts of carbon C, hydrogen H, sulfur S and other substances. During combustion, atoms C, H, and S combine with oxygen atoms O 2, resulting in molecules CO, CO 2, H 2 O, SO 2. At the same time, there is a selection a large number thermal energy that people have learned to use for their own purposes.
Rice. 1. Types of fuel: coal, peat, oil, gas.
The main contribution to the heat release is made by carbon C. The second largest contribution in terms of the amount of heat is made by hydrogen H.
Rice. 2. Carbon atoms react with oxygen atoms.
What is specific heat of combustion?
Specific heat of combustion q is physical quantity equal to the amount of heat released during complete combustion of 1 kg of fuel.
The specific heat of combustion formula looks like this:
$$ q = (Q \ over m) $$
Q is the amount of heat released during fuel combustion, J;
m - fuel mass, kg.
The unit of measurement for q in the international SI system is J / kg.
$$ [q] = (J \ over kg) $$
Non-systemic units of energy are often used to denote large q values: kilojoules (kJ), megajoules (MJ), and gigajoules (GJ).
The q values for different substances are determined experimentally.
Knowing q, we can calculate the amount of heat Q that will result from the combustion of fuel of mass m:
How specific heat of combustion is measured
To measure q, devices are used, which are called calorimeters (calor - heat, metreo - I measure).
A container with a portion of fuel is burned inside the device. The container is placed in water of known weight. As a result of combustion, the released heat heats the water. The amount of water mass and the change in its temperature make it possible to calculate the heat of combustion. Further, q is determined by the above formula.
Rice. 3. Measurement of specific heat of combustion.
Where can you find the values of q
Information on the values of specific heats of combustion for specific types of fuel can be found in technical reference books or in their electronic versions on Internet resources. Usually they are given in the form of a table like this:
Specific heat of combustion, q
Resources of the explored, modern species fuels are limited. Therefore, in the future, they will be replaced by other sources of energy:
- atomic, using the energy of nuclear reactions;
- solar, converting the energy of the sun's rays into heat and electricity;
- wind turbines;
- geothermal, using the heat of natural hot springs.
What have we learned?
So, we found out why a lot of heat is released when burning fuel. To calculate the amount of heat released during the combustion of a certain mass m of fuel, it is necessary to know the value q - the specific heat of combustion of this fuel. The q values are determined experimentally by calorimetry methods and are given in reference books.
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The tables show the mass specific heat of combustion of fuel (liquid, solid and gaseous) and some other combustible materials. The following fuels were considered: coal, firewood, coke, peat, kerosene, oil, alcohol, gasoline, natural gas, etc.
List of tables:
During an exothermic oxidation reaction of fuel, its chemical energy is converted into thermal energy with the release of a certain amount of heat. The resulting thermal energy is usually called the heat of combustion of the fuel. It depends on its chemical composition, humidity and is the main one. The heat of combustion of fuel per 1 kg of mass or 1 m 3 of volume forms the mass or volumetric specific heat of combustion.
Specific heat of combustion of fuel is the amount of heat released during the complete combustion of a unit of mass or volume of solid, liquid or gaseous fuel. In the International System of Units, this value is measured in J / kg or J / m 3.
The specific heat of combustion of the fuel can be determined experimentally or calculated analytically. Experimental methods for determining the calorific value are based on the practical measurement of the amount of heat released during the combustion of fuel, for example, in a calorimeter with a thermostat and a combustion bomb. For fuel with a known chemical composition, the specific heat of combustion can be determined using the Mendeleev formula.
Distinguish between higher and lower specific heats of combustion. The highest calorific value is maximum number the heat released during the complete combustion of the fuel, taking into account the heat spent on the evaporation of moisture contained in the fuel. Net calorific value less value higher by the value of the heat of condensation, which is formed from the moisture of the fuel and the hydrogen of the organic mass, which is converted into water during combustion.
To determine fuel quality indicators, as well as in heat engineering calculations usually use the lowest specific heat of combustion, which is the most important thermal and performance characteristic of the fuel and is shown in the tables below.
Specific heat of combustion of solid fuel (coal, firewood, peat, coke)
The table shows the values of the specific heat of combustion of dry solid fuel in terms of MJ / kg. The fuel in the table is sorted alphabetically by name.
The highest calorific value of the considered solid fuels is possessed by coking coal - its specific heat of combustion is 36.3 MJ / kg (or in SI units 36.3 · 10 6 J / kg). In addition, high heat of combustion is characteristic of coal, anthracite, charcoal and lignite coal.
Fuels with low energy efficiency include wood, firewood, gunpowder, milling peat, oil shale. For example, the specific heat of combustion of firewood is 8.4 ... 12.5, and gunpowder - only 3.8 MJ / kg.
| Fuel | |
|---|---|
| Anthracite | 26,8…34,8 |
| Wood pellets (pellets) | 18,5 |
| Dry firewood | 8,4…11 |
| Dry birch firewood | 12,5 |
| Gas coke | 26,9 |
| Blast furnace coke | 30,4 |
| Semi-coke | 27,3 |
| Powder | 3,8 |
| Slate | 4,6…9 |
| Combustible shale | 5,9…15 |
| Solid rocket fuel | 4,2…10,5 |
| Peat | 16,3 |
| Fibrous peat | 21,8 |
| Milling peat | 8,1…10,5 |
| Peat crumb | 10,8 |
| Brown coal | 13…25 |
| Brown coal (briquettes) | 20,2 |
| Brown coal (dust) | 25 |
| Donetsk coal | 19,7…24 |
| Charcoal | 31,5…34,4 |
| Hard coal | 27 |
| Coking coal | 36,3 |
| Kuznetsk coal | 22,8…25,1 |
| Chelyabinsk coal | 12,8 |
| Ekibastuz coal | 16,7 |
| Freztorf | 8,1 |
| Slag | 27,5 |
Specific heat of combustion of liquid fuel (alcohol, gasoline, kerosene, oil)
The table of specific heats of combustion of liquid fuel and some other organic liquids is given. It should be noted that such fuels as gasoline, diesel fuel and oil.
The specific heat of combustion of alcohol and acetone is significantly lower than traditional motor fuels. In addition, liquid rocket fuel has a relatively low calorific value and - with complete combustion of 1 kg of these hydrocarbons, an amount of heat will be released equal to 9.2 and 13.3 MJ, respectively.
| Fuel | Specific heat of combustion, MJ / kg |
|---|---|
| Acetone | 31,4 |
| Gasoline A-72 (GOST 2084-67) | 44,2 |
| Aviation gasoline B-70 (GOST 1012-72) | 44,1 |
| Gasoline AI-93 (GOST 2084-67) | 43,6 |
| Benzene | 40,6 |
| Diesel fuel winter (GOST 305-73) | 43,6 |
| Summer diesel fuel (GOST 305-73) | 43,4 |
| Liquid rocket fuel (kerosene + liquid oxygen) | 9,2 |
| Aviation kerosene | 42,9 |
| Lighting kerosene (GOST 4753-68) | 43,7 |
| Xylene | 43,2 |
| High-sulfur fuel oil | 39 |
| Low-sulfur fuel oil | 40,5 |
| Low-sulfur fuel oil | 41,7 |
| Sulphurous fuel oil | 39,6 |
| Methyl alcohol (methanol) | 21,1 |
| n-butyl alcohol | 36,8 |
| Oil | 43,5…46 |
| Methane oil | 21,5 |
| Toluene | 40,9 |
| White spirit (GOST 313452) | 44 |
| Ethylene glycol | 13,3 |
| Ethyl alcohol (ethanol) | 30,6 |
Specific heat of combustion of gaseous fuel and combustible gases
The table of specific heats of combustion of gaseous fuel and some other combustible gases in terms of MJ / kg is presented. Of the gases considered, the largest mass specific heat of combustion differs. With the complete combustion of one kilogram of this gas, 119.83 MJ of heat will be released. Also, such a fuel as natural gas has a high calorific value - the specific heat of combustion of natural gas is 41 ... 49 MJ / kg (for a pure 50 MJ / kg).
| Fuel | Specific heat of combustion, MJ / kg |
|---|---|
| 1-Butene | 45,3 |
| Ammonia | 18,6 |
| Acetylene | 48,3 |
| Hydrogen | 119,83 |
| Hydrogen, mixture with methane (50% H 2 and 50% CH 4 by mass) | 85 |
| Hydrogen, mixture with methane and carbon monoxide (33-33-33% by mass) | 60 |
| Hydrogen mixed with carbon monoxide (50% H 2 50% CO 2 by mass) | 65 |
| Blast furnace gas | 3 |
| Coke oven gas | 38,5 |
| Liquefied petroleum gas (LPG) (propane-butane) | 43,8 |
| Isobutane | 45,6 |
| Methane | 50 |
| n-Bhutan | 45,7 |
| n-Hexane | 45,1 |
| n-Pentane | 45,4 |
| Associated gas | 40,6…43 |
| Natural gas | 41…49 |
| Propadien | 46,3 |
| Propane | 46,3 |
| Propylene | 45,8 |
| Propylene, mixture with hydrogen and carbon monoxide (90% -9% -1% by mass) | 52 |
| Ethane | 47,5 |
| Ethylene | 47,2 |
Specific heat of combustion of some combustible materials
There is a table of specific heats of combustion of some combustible materials (wood, paper, plastic, straw, rubber, etc.). It should be noted materials with high combustion heat. These materials include: rubber different types, expanded polystyrene (polystyrene), polypropylene and polyethylene.
| Fuel | Specific heat of combustion, MJ / kg |
|---|---|
| Paper | 17,6 |
| Leatherette | 21,5 |
| Wood (bars with a moisture content of 14%) | 13,8 |
| Wood in stacks | 16,6 |
| Oak wood | 19,9 |
| Spruce wood | 20,3 |
| The wood is green | 6,3 |
| Pine wood | 20,9 |
| Nylon | 31,1 |
| Carbolite products | 26,9 |
| Cardboard | 16,5 |
| Styrene-butadiene rubber SKS-30AR | 43,9 |
| Natural rubber | 44,8 |
| Synthetic rubber | 40,2 |
| SKS rubber | 43,9 |
| Chloroprene rubber | 28 |
| Linoleum, polyvinyl chloride | 14,3 |
| Two-layer polyvinyl chloride linoleum | 17,9 |
| Felt-based PVC linoleum | 16,6 |
| Linoleum, polyvinyl chloride on a warm basis | 17,6 |
| Linoleum, polyvinyl chloride on a fabric basis | 20,3 |
| Linoleum rubber (relin) | 27,2 |
| Paraffin wax | 11,2 |
| Polyfoam PVC-1 | 19,5 |
| Styrofoam FS-7 | 24,4 |
| Foam FF | 31,4 |
| Expanded polystyrene PSB-S | 41,6 |
| Polyurethane foam | 24,3 |
| Fiber board | 20,9 |
| Polyvinyl chloride (PVC) | 20,7 |
| Polycarbonate | 31 |
| Polypropylene | 45,7 |
| Polystyrene | 39 |
| High pressure polyethylene | 47 |
| Low-pressure polyethylene | 46,7 |
| Rubber | 33,5 |
| Roofing material | 29,5 |
| Channel soot | 28,3 |
| Hay | 16,7 |
| Straw | 17 |
| Organic glass (plexiglass) | 27,7 |
| Textolite | 20,9 |
| Tol | 16 |
| TNT | 15 |
| Cotton | 17,5 |
| Cellulose | 16,4 |
| Wool and wool fibers | 23,1 |
Sources:
- GOST 147-2013 Solid mineral fuel. Determination of gross calorific value and calculation of net calorific value.
- GOST 21261-91 Petroleum products. Method for determining the gross calorific value and calculating the net calorific value.
- GOST 22667-82 Natural combustible gases. Calculation method for determining the calorific value, relative density and Wobbe number.
- GOST 31369-2008 Natural gas. Calculation of calorific value, density, relative density and Wobbe number based on component composition.
- Zemskiy G.T.
When a certain amount of fuel is burned, a measurable amount of heat is released. According to the International System of Units, the value is expressed in Joules per kg or m 3. But the parameters can be calculated in kcal or kW. If the value is related to the unit of measurement of the fuel, it is called specific.
What does the calorific value of different fuels affect? What is the value of the indicator for liquid, solid and gaseous substances? The answers to these questions are detailed in the article. In addition, we have prepared a table showing the specific heats of combustion of materials - this information is useful when choosing a high-energy type of fuel.
The release of energy during combustion should be characterized by two parameters: high efficiency and the absence of the production of harmful substances.
Artificial fuel is obtained during the processing of natural -. Regardless of the state of aggregation, substances in their chemical composition have a combustible and non-combustible part. The first is carbon and hydrogen. The second consists of water, mineral salts, nitrogen, oxygen, metals.
According to the state of aggregation, the fuel is divided into liquid, solid and gas. Each group is additionally branched into a natural and artificial subgroup (+)
When 1 kg of such a "mixture" is burned, different amounts of energy are released. How much of this energy will be released depends on the proportions of the indicated elements - combustible part, humidity, ash content and other components.
The heat of combustion of fuel (TCT) is formed from two levels - the highest and the lowest. The first indicator is obtained due to water condensation, in the second this factor is not taken into account.
The lowest TST is needed to calculate the need for fuel and its cost, with the help of such indicators, heat balances are compiled and the efficiency of plants operating on fuel is determined.
TST can be calculated analytically or experimentally. If chemical composition fuel is known, Mendeleev's formula is applied. Experimental techniques are based on the actual measurement of the combustion heat.
In these cases, a special combustion bomb is used - a calorimetric one together with a calorimeter and a thermostat.
The calculation features are individual for each type of fuel. Example: TCT in combustion engines is calculated from the lowest value, because liquid does not condense in the cylinders.
Parameters of liquid substances
Liquid materials, like solid ones, are decomposed into the following components: carbon, hydrogen, sulfur, oxygen, nitrogen. The percentage is expressed by weight.
Internal organic ballast of the fuel is formed from oxygen and nitrogen; these components do not burn and are conditionally included in the composition. External ballast is formed from moisture and ash.
Gasoline has a high specific heat of combustion. Depending on the brand, it is 43-44 MJ.
Similar indicators of specific heat of combustion are determined for aviation kerosene - 42.9 MJ. Diesel fuel also falls into the category of leaders in terms of calorific value - 43.4-43.6 MJ.
Liquid rocket fuel, ethylene glycol, is characterized by relatively low TST values. Alcohol and acetone differ in the minimum specific heat of combustion. Their performance is significantly lower than that of conventional motor fuels.
Fuel gas properties
Gaseous fuel consists of carbon monoxide, hydrogen, methane, ethane, propane, butane, ethylene, benzene, hydrogen sulfide and other components. These figures are expressed as a percentage by volume.
Hydrogen has the highest calorific value. Burning, a kilogram of matter releases 119.83 MJ of heat. But it is distinguished by an increased degree of explosiveness.
Natural gas also has high heating values.
They are equal to 41-49 MJ per kg. But, for example, pure methane has a higher combustion heat - 50 MJ per kg.
Comparative table of indicators
The table shows the values of the mass specific heats of combustion of liquid, solid, gaseous types of fuel.
| Type of fuel | Unit rev. | Specific heat of combustion | ||
| Mj | kw | kcal | ||
| Firewood: oak, birch, ash, beech, hornbeam | kg | 15 | 4,2 | 2500 |
| Firewood: larch, pine, spruce | kg | 15,5 | 4,3 | 2500 |
| Brown coal | kg | 12,98 | 3,6 | 3100 |
| Hard coal | kg | 27,00 | 7,5 | 6450 |
| Charcoal | kg | 27,26 | 7,5 | 6510 |
| Anthracite | kg | 28,05 | 7,8 | 6700 |
| Wood pellet | kg | 17,17 | 4,7 | 4110 |
| Straw pellet | kg | 14,51 | 4,0 | 3465 |
| Sunflower pellets | kg | 18,09 | 5,0 | 4320 |
| Sawdust | kg | 8,37 | 2,3 | 2000 |
| Paper | kg | 16,62 | 4,6 | 3970 |
| Vine | kg | 14,00 | 3,9 | 3345 |
| Natural gas | m 3 | 33,5 | 9,3 | 8000 |
| Liquefied gas | kg | 45,20 | 12,5 | 10800 |
| Petrol | kg | 44,00 | 12,2 | 10500 |
| Dis. fuel | kg | 43,12 | 11,9 | 10300 |
| Methane | m 3 | 50,03 | 13,8 | 11950 |
| Hydrogen | m 3 | 120 | 33,2 | 28700 |
| Kerosene | kg | 43.50 | 12 | 10400 |
| Fuel oil | kg | 40,61 | 11,2 | 9700 |
| Oil | kg | 44,00 | 12,2 | 10500 |
| Propane | m 3 | 45,57 | 12,6 | 10885 |
| Ethylene | m 3 | 48,02 | 13,3 | 11470 |
It can be seen from the table that the highest TST indicators of all substances, and not only of gaseous ones, have hydrogen. It belongs to high-energy types of fuel.
The combustion product of hydrogen is ordinary water. The process does not emit furnace slags, ash, carbon monoxide and carbon dioxide, which makes the substance an environmentally friendly combustible. But it is explosive and has a low density, so such fuel is difficult to liquefy and transport.
Conclusions and useful video on the topic
About the calorific value of different types of wood. Comparison of indicators per m3 and kg.
TST is the most important thermal and operational characteristic of fuel. This indicator is used in various spheres of human activity: heat engines, power plants, industry, housing heating and cooking.
Calorific values help to compare different kinds fuel according to the degree of energy released, calculate the required mass of fuel, save on costs.
Do you have anything to add, or do you have questions about the calorific value of different types of fuel? You can leave comments on the publication and participate in discussions - the contact form is in the lower block.
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