# Polytropic processes

1. Oct 31, 2011

### jason.bourne

polytropic processes are characterized by pvn = constant.

are they valid for both reversible as well as irreversible processes?

2. Oct 31, 2011

### Andrew Mason

It depends.

The relationship PV= constant (ie n = 1) for an ideal gas applies for all isothermal processes, reversible or non-reversible (ie. PV=nRT)

However, the adiabatic condition for an ideal gas:

$PV^\gamma = K$ applies only to a reversible adiabatic change.

AM

3. Oct 31, 2011

### jason.bourne

thanks Andrew.

suppose if there is a process in which heat flow is happening and the temperature of the system is not constant, lets assume that polytropic index is in the range 1 < n < γ.

if the process was reversible, then it is reversible polytropic process and we can characterize it by pvn = constant.

but what if there was friction or some other sort of irreversibility?
how do we take that into account? how can we characterize such polytropic processes?