polytropic process (redirected from Politropic)

polytropic process [¦päl·i¦träp·ik ′prä·səs]

(thermodynamics)

An expansion or compression of a gas in which the quantitypVⁿis held constant, wherepandVare the pressure and volume of the gas, andnis some constant.

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Polytropic process

A process which occurs with an interchange of both heat and work between the system and its surroundings. The nonadiabatic expansion or compression of a fluid is an example of a polytropic process. The interrelationships between the pressure (P) and volume (V) and pressure and temperature (T) for a gas undergoing a polytropic process are given by Eqs. (1) and

(1) 

(2) 

(2), where a and b are the polytropic constants for the process of interest. These constants, which are usually determined from experiment, depend upon the equation of state of the gas, the amount of heat transferred, and the extent of irreversibility in the process. See Isentropic process, Isothermal process, Thermodynamic processes