The Polytropic Process:


The polytropic process is one in which the pressure-volume relation is given as



The exponent n may have any value from minus infinity to plus infinity depending on the process. Some of the more common values are given below.


Exponent n

Constant pressure


Constant volume

Isothermal & ideal gas


Adiabatic & ideal gas

k = CP/CV


Here k is the ratio of the specific heat at constant pressure, CP, to specific heat at constant volume, CV. The specific heats will be discussed later.

The boundary work done during the polytropic process is found by substituting the pressure volume relation into the boundary work equation. The result is



For an ideal gas under going a polytropic process the boundary work is



Notice that the results we obtained for an ideal gas undergoing a polytropic process when n = 1, is identical to that for an ideal gas undergoing the isothermal process.


Return to Outline

Contact UsMHHE HomeOrderSite IndexSearch

Copyright ©1998 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use and Privacy Policy. For further information about this site contact McGraw-Hill Higher Education is one of the many fine businesses of The McGraw-Hill Companies.

Corporate Link