# But why it is needed, the specific heat of combustion

After adaptations of old fire people for their needs are always looking for some new applications of heat and new fuels.The fuel used in different types of combustibles: solid, liquid, gaseous.And with all this specific heat of combustion?

By definition the amount of heat produced by the combustion of 1 kg of a solid cube or 1.meters of gaseous substances - this is the specific heat of combustion.For its measurement used Joule per kilogram (or per cubic meter) or calories per kilogram.

Already from the very definition it is clear that such a thing as the specific heat of combustion allows you to compare different types of fuel each other.In fact, this means how much energy as heat can be obtained from the unit fuel.Every substance, this value will be different.For a clearer understanding refer to the handbook.

turns out that wood specific heat of combustion is 8,4-11 MJ / kg, but this will be the coal of 15-16 MJ / kg.What does this mean?

But here everything is very simple.One kilogram of coal when burned gives more heat almost twice than is obtained by burning a kilogram of wood, and here we are talking about the wood with a certain humidity.Because if the humidity of firewood is high, the thermal energy will be spent on evaporation and vaporization of water contained in the wood, and the final result will be even worse.

You can also consider the practical application of this concept to the art.Let's go back a little back in the era of steam locomotives and ships.Even the fact that we see the specific heat of combustion (coal and firewood) is different, it is clear from this that the same way of the locomotive or steamship need firewood more than coal.Of course, if we assume that the energy they spend on the road the same way, regardless of the type of fuel.

And another conclusion arises from the above example.Knowing the specific heat of combustion is possible to determine how many kilometers will be able to drive a locomotive or sail boat, having a supply of fuel wood or charcoal.If you make a mistake with the fuel supply, all traffic on the route will end.

Already have practical application in the face of incomprehensible and unnecessary parameter.You can compare different substances and determine their applicability in a particular situation as a fuel, as well as assess the impact of this application.

Recently conducted a lot of talk about the transition to other energy sources instead of gasoline.If you look at this problem from the standpoint of the energy possibilities of fuel is not touching any other aspect of this issue, the situation becomes clear and transparent.So, for example, and further discussion, the specific heat of combustion of gasoline is 44-47 MJ / kg of ethyl alcohol - 27 MJ / kg.Although ethyl alcohol for use as fuel for internal combustion engines, in comparing these data is roughly the same situation as described above, with wood and coal.Ethyl alcohol should be more will drive the car on a gas station less, and the power of the engine by using alcohol to fall.

However, this applies to alcohol ethyl or methyl.If used as a fuel butyl alcohol, which specific heat of combustion is the same as that of gasoline, the practical experiments automakers confirm the possibility of its use as a fuel instead of gasoline, but that does not concern the issue in question.

Thus, it is clear that the specific heat of combustion is the energy characteristic of the substance, in particular fuel.This value allows you to compare the capabilities of different substances and materials, evaluate their advantages and disadvantages.