We can model these processes using the relative ship PV^n=Constant i.e. There can be infinite such processes and are all considered adiabatic – the heat transfer is insignificant compared with the work transfer. The web reference given by “Onno” is good one, but it does not cover the polytropic processes between the isothermal and isentropic processes. RE: Polytropic process sailoday28 (Mechanical) In Fact, the actual compression process of a as very nearly approaches adibatic compression because the time of compression is very short". Conversely, the smaller the trasnfer of heat the closer the polytropic compression processapproaches that of an adibatic process. The closer this polytropic compression process approaches the isothermal process path. Consequentlythe compression process is polytropic so that the the greater the transfer of heat the When the quantity of heat that a gas loses to its surroundings during a compression process is inadequate, it's temperature cannot be constantly maintained. These relationships also apply to the compression process. In processes in which the greater part of the energy to do the work comes from the surroundings, the process path approaches the isothermal, Similarly, when the geater part of the energy to do the work on the surroundingscomes from the gas itself, the process path approaches that of the adiabatic process. In other words, any expansion process in which the energy to do the work of expansion is supplied partly from the surroundings and partly from the gas within the system will follow a path that falls between those of isothermal and adiabatic. Gewnerally the term polytropic is only applied to those processes whose path falls between those of the isothermal and adiabaticprocesses. by this defination, all five thermodynamic processes are polyropic. " Broadly defined, a polytropic process is any process in which the specific heat of the gas remains constant. These comments were taken from "Principles of Refrigeration"R.J.
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