Heat Engine and its Performance

HEAT ENGINE AND ITS PERFORMANCE

Heat engine is a device which operates a thermodynamic cycle and produces work by supplying heat from hot reservoir. Example: Internal combustion (I.C.) engines, boiler etc.

The performance of any engine is measured by the term 'efficiency'. It is defined as the ratio of network output produced by an engine to the amount of heat supplied to the engine. It is expressed as given below.

where

W - Work done

Q1 - Heat supplied from the heat reservoir at temperature T1

We know that

W = Q1 – Q2     ...(2.2)

where

Q2 - Heat rejected from the engine to the sink or cold reservoir at temperature T2

Substituting (2.2) in (2.1), then the efficiency becomes

where T1 and T2 are high and low temperature of reservoirs respectively.

The thermal efficiency of a heat engine is always less than unity. Thermal efficiency is a measure of how efficiently a heat engine converts the heat into work.