The refrigerator is a device consisting of a thermally insulated chamber and a heat pump which transfers heat from the inside to the outside so that the inside cools down. The main purpose of a refrigerator is to keep food fresh. Cooler temperatures help food stay fresher for longer. The basic idea of cooling is to slow down bacterial activity, and the main function of refrigerators is to use food to evaporate. The main functional parts of a refrigerator include: compressor, condenser, evaporator, expansion valve, and coolant.