specific heat of combustion - specific heat— Topics oil and gas industry Synonyms specific heat capacity EN specific heat ...
The amount of heat released during complete combustion of 1 kg of fuel. The specific heat of combustion of fuel is determined experimentally and is the most important characteristic fuel. See also: Fuel Financial Dictionary Finam... Financial Dictionary
specific heat of combustion of peat by bomb- Higher heat of combustion of peat, taking into account the heat of formation and dissolution of sulfuric and nitric acids in water. [GOST 21123 85] Inadmissible, not recommended calorific value of peat for a bomb Topics peat General terms properties of peat EN ... ... Technical Translator's Guide
specific heat of combustion (fuel)- 3.1.19 specific heat of combustion (fuel): The total amount of energy released under regulated conditions of fuel combustion. Source …
Specific heat of combustion of peat by bomb- 122. Specific heat of combustion of peat by bomb Higher heat of combustion of peat taking into account the heat of formation and dissolution of sulfuric and nitric acids in water Source: GOST 21123 85: Peat. Terms and definitions original document... Dictionary-reference book of terms of normative and technical documentation
specific heat of combustion of fuel- 35 specific heat of combustion of fuel: The total amount of energy released under specified fuel combustion conditions. Source: GOST R 53905 2010: Energy saving. Terms and definitions original document... Dictionary-reference book of terms of normative and technical documentation
This is the amount of heat released during complete combustion of a mass (for solid and liquid substances) or volumetric (for gaseous) unit of a substance. Measured in joules or calories. Heat of combustion per unit mass or volume of fuel, ... ... Wikipedia
Modern encyclopedia
Heat of combustion- (heat of combustion, calorie content), the amount of heat released during complete combustion of fuel. There are specific heat of combustion, volumetric heat, etc. For example, specific heat of combustion coal 28 34 MJ/kg, gasoline about 44 MJ/kg; volumetric... ... Illustrated Encyclopedic Dictionary
Specific heat of combustion of fuel- Specific heat of combustion of a fuel: the total amount of energy released under specified combustion conditions...
It is known that the source of energy that is used in industry, transport, agriculture, in everyday life, is fuel. These are coal, oil, peat, firewood, natural gas etc. When fuel burns, energy is released. Let's try to find out how energy is released in this case.
Let us recall the structure of the water molecule (Fig. 16, a). It consists of one oxygen atom and two hydrogen atoms. If a water molecule is divided into atoms, then it is necessary to overcome the forces of attraction between the atoms, that is, work must be done, and therefore energy must be spent. Conversely, if atoms combine to form a molecule, energy is released.
The use of fuel is based precisely on the phenomenon of energy release when atoms join. For example, the carbon atoms contained in the fuel combine with two oxygen atoms during combustion (Fig. 16, b). In this case, a carbon monoxide molecule is formed - carbon dioxide- and energy is released.
Rice. 16. Structure of molecules:
a - water; b - the combination of a carbon atom and two oxygen atoms into a carbon dioxide molecule
When calculating engines, the engineer needs to know exactly how much heat the burned fuel can release. To do this, it is necessary to experimentally determine how much heat will be released during the complete combustion of the same mass of fuel of different types.
A physical quantity showing how much heat is released during the complete combustion of fuel weighing 1 kg is called the specific heat of combustion of the fuel.
The specific heat of combustion is denoted by the letter q. Unit specific heat combustion is 1 J/kg.
The specific heat of combustion is determined experimentally using rather complex instruments.
The results of the experimental data are shown in Table 2.
table 2
From this table it can be seen that the specific heat of combustion, for example, of gasoline is 4.6 10 7 J / kg.
This means that the complete combustion of gasoline weighing 1 kg releases 4.6 10 7 J of energy.
The total amount of heat Q released during the combustion of m kg of fuel is calculated by the formula
Questions
- What is the specific heat of combustion of fuel?
- In what units is the specific heat of combustion of fuel measured?
- What does the expression “specific heat of combustion of fuel equal to 1.4 10 7 J / kg” mean? How is the amount of heat released during fuel combustion calculated?
Exercise 9
- How much heat is released during complete combustion? charcoal weighing 15 kg; alcohol weighing 200 g?
- How much heat will be released during the complete combustion of oil, the mass of which is 2.5 tons; kerosene, the volume of which is 2 liters and the density is 800 kg / m 3?
- When dry wood was completely burned, 50,000 kJ of energy was released. What mass of wood burned?
Exercise
Using Table 2, construct a bar chart for the specific heat of combustion of firewood, alcohol, oil, hydrogen, choosing the scale as follows: the width of the rectangle is 1 cell, the height of 2 mm corresponds to 10 J.
Substances of organic origin include fuels that, when burned, release a certain amount of thermal energy. Heat production must be characterized by high efficiency and the absence of side effects, in particular, substances harmful to human health and the environment.
For ease of loading into the firebox wood material cut into individual elements up to 30 cm long. To increase the efficiency of their use, the firewood should be as dry as possible, and the burning process should be relatively slow. In many respects, wood from hardwoods such as oak and birch, hazel and ash, and hawthorn are suitable for heating premises. Due to high resin content, increased burning rate and low calorific value coniferous trees in this regard they are significantly inferior.
It should be understood that the value of the calorific value is affected by the density of wood.
This natural material plant origin, extracted from sedimentary rock.
In this form solid fuel contain carbon and other chemical elements. There is a division of material into types depending on its age. Brown coal is considered the youngest, followed by hard coal, and anthracite is older than all other types. The age of a combustible substance also determines its moisture content, which is more present in young material.
During the combustion of coal, environmental pollution occurs, and slag is formed on the boiler grates, which to a certain extent creates an obstacle to normal combustion. The presence of sulfur in the material is also an unfavorable factor for the atmosphere, since in the air space this element is converted into sulfuric acid.
However, consumers should not fear for their health. Manufacturers of this material, taking care of private customers, strive to reduce the sulfur content in it. The heating value of coal can vary even within the same type. The difference depends on the characteristics of the subspecies and its mineral content, as well as the geography of production. As a solid fuel, not only pure coal is found, but also low-enriched coal slag, pressed into briquettes.
Pellets (fuel granules) are solid fuels created industrially from wood and plant waste: shavings, bark, cardboard, straw.
The raw material, crushed to dust, is dried and poured into a granulator, from where it comes out in the form of granules a certain shape. To add viscosity to the mass, a plant polymer, lignin, is used. The complexity of the production process and high demand determine the cost of pellets. The material is used in specially equipped boilers.
Types of fuel are determined depending on the material from which they are processed:
- round timber of trees of any species;
- straw;
- peat;
- sunflower husk.
Among the advantages that fuel pellets have, it is worth noting the following qualities:
- environmental friendliness;
- inability to deform and resistance to fungus;
- easy storage even outdoors;
- uniformity and duration of combustion;
- relatively low cost;
- Possibility of use for various heating devices;
- suitable granule size for automatic download into a specially equipped boiler.
Briquettes
Briquettes are solid fuels that are in many ways similar to pellets. For their manufacture, identical materials are used: wood chips, shavings, peat, husks and straw. During the production process, raw materials are crushed and formed into briquettes by compression. This material is also an environmentally friendly fuel. It is convenient to store even on outdoors. Smooth, uniform and slow combustion of this fuel can be observed both in fireplaces and stoves, and in heating boilers.
The types of environmentally friendly solid fuel discussed above are a good alternative for generating heat. In comparison with fossil sources of thermal energy, which have an unfavorable effect on combustion environment and being, in addition, non-renewable, alternative fuels have clear advantages and relatively low cost, which is important for certain categories of consumers.
At the same time, the fire hazard of such fuels is much higher. Therefore, it is necessary to take some safety measures regarding their storage and the use of fire-resistant materials for walls.
Liquid and gaseous fuels
As for liquid and gaseous flammable substances, the situation here is as follows.
In this lesson we will learn how to calculate the amount of heat that fuel releases during combustion. In addition, we will consider the characteristics of the fuel - the specific heat of combustion.
Since our whole life is based on movement, and movement is mostly based on the combustion of fuel, studying this topic is very important for understanding the topic “Thermal Phenomena”.
After studying the issues related to the amount of heat and specific heat capacity, let's move on to consider amount of heat released when burning fuel.
Definition
Fuel- a substance that produces heat in some processes (combustion, nuclear reactions). Is a source of energy.
Fuel happens solid, liquid and gaseous(Fig. 1).
Rice. 1. Types of fuel
- TO hard types fuels include coal and peat.
- Liquid fuels include oil, gasoline and other petroleum products.
- Gaseous fuels include natural gas.
- Separately, we can highlight the very common recently nuclear fuel.
Combustion of fuel is chemical process, which is oxidizing. During combustion, carbon atoms combine with oxygen atoms to form molecules. As a result of this, energy is released, which a person uses for his own purposes (Fig. 2).
Rice. 2. Formation of carbon dioxide
To characterize the fuel, the following characteristic is used: calorific value. Calorific value shows how much heat is released during fuel combustion (Fig. 3). In physics, calorific value corresponds to the concept specific heat of combustion of a substance.
Rice. 3. Specific heat of combustion
Definition
Specific heat of combustion - physical quantity, which characterizes the fuel, is numerically equal to the amount of heat that is released during complete combustion of the fuel.
The specific heat of combustion is usually denoted by the letter . Units:
There is no unit of measurement, since fuel combustion occurs at an almost constant temperature.
The specific heat of combustion is determined experimentally using sophisticated instruments. However, there are special tables for solving problems. Below we present the values of the specific heat of combustion for some types of fuel.
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Substance |
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Table 4. Specific heat of combustion of some substances
From the given values it is clear that during combustion it is released great amount heat, so the units of measurement (megajoules) and (gigajoules) are used.
To calculate the amount of heat released during fuel combustion, the following formula is used:
Here: - mass of fuel (kg), - specific heat of combustion of fuel ().
In conclusion, we note that most of the fuel used by humanity is stored using solar energy. Coal, oil, gas - all this was formed on Earth due to the influence of the Sun (Fig. 4).
Rice. 4. Fuel formation
In the next lesson we will talk about the law of conservation and transformation of energy in mechanical and thermal processes.
Listliterature
- Gendenshtein L.E., Kaidalov A.B., Kozhevnikov V.B. / Ed. Orlova V.A., Roizena I.I. Physics 8. - M.: Mnemosyne.
- Peryshkin A.V. Physics 8. - M.: Bustard, 2010.
- Fadeeva A.A., Zasov A.V., Kiselev D.F. Physics 8. - M.: Enlightenment.
- Internet portal “festival.1september.ru” ()
- Internet portal “school.xvatit.com” ()
- Internet portal “stringer46.narod.ru” ()
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