Editing Refrigeration (section)

====Gas cycle====
{{unreferenced section|date=February 2020}}
When the [[working fluid]] is a gas that is compressed and expanded but does not change phase, the refrigeration cycle is called a ''gas cycle''. [[Air]] is most often this working fluid. As there is no condensation and evaporation intended in a gas cycle, components corresponding to the condenser and evaporator in a vapor compression cycle are the hot and cold gas-to-gas [[heat exchanger]]s in gas cycles.

The gas cycle is less efficient than the vapor compression cycle because the gas cycle works on the reverse [[Brayton cycle]] instead of the reverse [[Rankine cycle]]. As such, the working fluid does not receive and reject heat at constant temperature. In the gas cycle, the refrigeration effect is equal to the product of the specific heat of the gas and the rise in temperature of the gas in the low temperature side. Therefore, for the same cooling load, a gas refrigeration cycle needs a large mass flow rate and is bulky.

Because of their lower efficiency and larger bulk, ''air cycle'' coolers are not often used nowadays in terrestrial cooling devices. However, the [[air cycle machine]] is very common on [[gas turbine]]-powered jet [[aircraft]] as cooling and ventilation units, because compressed air is readily available from the engines' compressor sections. Such units also serve the purpose of pressurizing the aircraft.