In Polytropic process the product of Pressure and Volume (PV) power 'n' is constant

where,

'n' is polytropic index

See wikipedia article on polytropic processes.

the value of polytropic exponent "n" in reversible process will vary from 1 to adiabatic constant "gamma"

1.2 to 1.4

A polytropic process is a process where ( P ) ( V )^n is maintained throughout the process; commonly a compression or an expansion. The n is called the polytropic exponent and is often between 1.0 and k , the specific heat ratio.

For a reversible, polytropic, and nonflow process :

WB = [ ( P2 ) ( V2 ) - ( P1 ) ( V1 ) ] / [ 1 - n ]

or

WB = [ 1 / 1 - n ][ ( P1 ) ( V1 ] [ ( P2 / P1 )^B - 1 ]

B = ( n - 1 ) / ( n )

For a reversible, polytropic, and steady flow process :

WSF = [ n / 1 - n ] [ ( P1 ) ( V1 )] [ ( P2 / P1 )^B - 1 ]

B = ( n - 1 ) / ( n )