You'll more quickly understand refrigerator cooling systems if you think of their action as "removing heat from the air in the refrigerator" rather than "cooling the air in the refrigerator." All residential refrigerators work on the same principal for cooling. They all have:
A Compressor - the motor or engine of the cooling system. The compressor runs whenever the thermostat calls for cooling.
A Condenser - is a series of tubes with fins attached to them, similar to a radiator. It's always somewhere on the outside of the refrigerator, near the cooling fan to draw room air over the fins and dissipate heat from the tubes or fins.
A Metering Device (Capillary Tube) - a tiny copper tube attached from the end of the condenser to the beginning of the evaporator. The capillary tube controls the pressure and flow of the refrigerant as it enters the evaporator.
An Evaporator - The evaporator is always located on the inside of the refrigerator, usually inside the freezer compartment. It also resembles a radiator.
When the liquid refrigerant comes out of the small capillary tube, it�s injected into the larger tubes of the evaporator causing a pressure drop. This pressure drop allows the refrigerant to expand back into a gaseous state. This change of state from liquid to gas absorbs heat. The gaseous refrigerant travels through the evaporator tubes, back out of the refrigerator and down to the compressor to begin the circulation process again.
Simple as that !