Heat Engine

What is heat engine?

Heat engine is a device which convert chemical energy of the fuel to heat energy & further convert heat energy to mechanical energy.

This we have experienced in our real life where we fill petrol or diesel in our vehicle & if we start the vehicle, combustion of the fuel takes place. So the chemical energy of the fuel, once burn convert to heat energy and this heat energy is converted to mechanical energy which helps in the movement of the wheels of the vehicle, as a result our vehicle moves.


There are 2 types of heat engine:

1) External combustion engine
2) Internal combustion engine

External combustion engine: In such type of engine, product of combustion transfer heat to working fluid. eg. In power-plant we burn coal in the furnace which gives heat and this heat is transfer to boiler where steam is produce from water due to this heat added from the furnace. Now in power-plant this steam is used as a working fluid.Here steam produce the required output.

Internal combustion engine: In such type of engine, product of combustion produces power directly. eg. In petrol engine or in diesel engine, we burn mixture of air & fuel due to which huge pressure is generated and it moves the piston directly. So, combustion of air-fuel mixture is directly responsible for the output. Here there is no such system of heat transfer. Here the stroke of the piston produce power.