A fridge works by taking heat out rather than putting cold in. The fridge uses a reusable refrigirant that evaporates and condenses to take heat away from the fridge
external image Fridge%20Back%20Insulation.jpg

The refrigerant is compressed, as it compresses it gains more heat and energy

It then goes through a coil where it is turned into a liquid but it is still at high pressure. it is the coil you can see in this image

The liquid is then pushed through an expansion valve slowly where it loses pressure and evaporates

This removes the heat from the fridge by removing the high energy particles that are warm from the fridge

The refrigirant then goes back to to the begining and is compressed once again