Efficiency of a Cycle may be defined as the ratio of work done to the heat supplied during a cycle. Mathematically, efficiency of a cycle,

Since the work done during a cycle is equal to heat supplied minus the heat rejected, the efficiency of a cycle, therefore, may also be expressed as

__Notes:__

**1.** The efficiency, as given above, is the theoretical efficiency of the cycle. Therefore it is known as theoretical thermal efficiency.

**2.** It does not take into account the practical losses, which occur in running of the engine.

**3.** In order to compare the efficiency of the thermodynamic cycles, air is assumed to be the working substance inside the engine cylinder. Moreover, air is assumed to behave as a perfect gas. The efficiency, thus, obtained is known as air standard efficiency. It is also called ideal efficiency.

Comments are closed.