3: Isentropic Flow Relations for a Perfect Gas

3: Isentropic Flow Relations for a Perfect Gas

 

Assuming reversible processes (no losses), and with the only work being that due to volume change against a pressure,

,so that

 

Integrating from one state to another,

 

Define

Then

If is constant

=

Isentropic Process

or

 

Note: This is the relation between the pressure ratio and temperature ratio for an isentropic change from one state to another at constant specific heats.