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Heat engineWHAT IS A HEAT ENGINE?A heat engine any device that is capable of converting thermal energy into mechanical energy. two main types of heat engines: external combustion and internal combustion:In anexternal combustion engine, the fuel burns outside and away from the main bit of the engine where the force and motion are produced.

In aninternal combustion engine, the fuel burnsinsidethe cylinder. In a typicalcar engine, for example, there are something like four to six separate cylinders inside which gasoline is constantly burning with oxygen to release heat energy. The cylinders "fire" alternately to ensure the engine produces a steady supply of power that drives the car'swheels.

Heat engines take many forms, from the internal combustion engine in the family car to the giant turbines that generate electricity for our homes.A fuel cell, which converts chemical energy into electricity -- can be described by its efficiency: the amount of energy input that is actually converted to useful output. In all heat engines, work is extracted from the flow of heat from a hot object to a cooler object. A good example is an electrical power plant.AHEAT ENGINEHAS THREE COMPONENTS:TheHot Reservoir(orHeat Source).TheCold ObjectorHeat Sink.The object on whichWorkis done.

HEAT CANNOT BE COMPLETELY CONVERTED, it is impossible to have 100 % efficiency.

The second law of thermodynamics (heat-enginestatement):It is impossible to construct a heat engine that, operating in a cycle,produces no effect other than the adsorption of energy from a reservoir and theperformance of an equal amount of work. (Kelvin Statement)

The important aspect here is that some ``waste heat'' is always expelled into the cooler reservoir; no heat engine could operate without such expulsion.

Shown is the energy transferdiagram of aheat engine.The work done percycle by a heatengine is:Wout = Qnet = QH QC

It is impossible to construct a heat engine that, operating in a cycle, produces no other effect than the absorption of energy from a reservoir and the performance of an equal amount of work Means that Qc cannot equal 0 Some Qc must be expelled to the environment Means that e cannot equal 100%Actual car engines and steam generators have 0.1 0.5.