Second Law of thermodynamic:
1) Kelvin Planck statement:
- It is impossible for engine to convert all the heat energy into work without rejecting some energy to sink i.e. no engine will have 100% efficiency.
- Presence of sink is essential for continuous conversion of heat into work.
2) Clausius statement:
- It is impossible to absorb heat energy from cold body and reject to hot body without doing work on it i.e. self acting refrigerator is impossible.
- Any device which converts heat energy continuously into mechanical work
- Its main parts are:
i)Source: A hot body at a constant high temperature (T1) from which the heat engine can draw heat (Q1).
ii)Sink: A cold body at a constant low temperature (T2) to which any amount of heat can be rejected.
iii)Working Substance: Working substance is an ideal gas which on being supplied with heat performs mechanical work.
Efficiency of heat engine:
- External work obtained to the heat energy absorbed by the working substance from the source.
- Denoted by ɳ
- When heat engines are placed in series then sink of 1st engine act as source for 2nd engine and so on.
- Efficiency of heat engine always less than 1 or 100%