Polytropic Process

Whenever a gas undergoes a reversible course in which there is heat transfer, the process often occurs in such a way that a plot of the Log P (pressure) vs. Log V (volume) is a straight line. Or expressed in equation form PVⁿ = a constant. This kind of process is termed as a polytropic process. An illustration of a polytropic process is the spreading out of the combustion gasses in the cylinder of a water-cooled reciprocating engine.