Gases, the substances that circulate inside the refrigerant circuit, obey a number of laws of physics, depending on the transformations that they undergo inside the circuit.
Boyle's law says that pressure is inversely proportional to volume. That is, compressing a gas with a piston inside a sealed container, the pressure increases.
If the temperature remains constant, then these two values change so that Pressure x Volume=constant.
This law is applied when a gas undergoes the isothermal transformations, that is, at a constant temperature.


The mathematical equation for Boyle's law is: PV = Kt where k is a constant, that is, Pressure x Volume = Constant x Temperature.



Gay Lussac's law says that the volume occupied by a certain quantity of gas, at a constant temperature, is inversely proportional to the pressure; this is applied when a gas undergoes isobaric transformations, that is, at a constant pressure.

Gay Lussac's law also says that the pressure of a gas is directly proportional to increase in temperature when the volume remains constant, and is applied when a gas undergoes isochoric transformations, that is, at a constant volume.


Despite this, a gas (or better, a gaseous fluid) may undergo transformations in which none of the three values (t, V or p) remains constant.