During actual expansion and compression processes of gases, pressure and volume are often related by (PVn = ), where n and C are constants. A process of this kind is called a polytropic process. The (P-V) diagram for such a process is shown below.
As mentioned, the general equation for polytropic processes is expressed as:
PVn = C
From the above equation, we can derive the following equations in the same method as in adiabatic processes:
From Eq. (1), the work done is derived in the same method earlier and expressed as:
The heat transfer for polytropic processes does not equal zero and can be calculated from the following equation:
