In one complete cycle of refrigeration, the refrigerant, a liquid such as fluorinated hydrocarbon, goes through the following steps :
(1) The refrigerant in the closed tube passes through the nozzle and
expands, into a low-pressure area. This adiabatic expansion results
in reduction in pressure and temperature of the fluid and the fluid
turns into a gas.
(2) The cold gas is in thermal contact with the inner compartment of the
fridge. Here it absorbs heat at constant pressure from the contents of
the fridge.
(3) The gas passes to a compressor where it does work in adiabatic
compression. This raises its temperature and converts it back into a
liquid.
(4) The hot liquid passes through the coils on the outside of the
refrigerator and releases heat to the air outside in an isobaric
compression process.
The compressor, driven by an external source of energy, does work
on the refrigerant during each cycle.
