Refrigeration is a cooling process that helps remove unwanted heat from an object and transfer it elsewhere. It helps lower the object’s temperature and maintain it around or below the ambient one. It can be accomplished in various ways, including ice, snow, cold water, or mechanical refrigeration. The mechanical refrigeration cycle uses a man-made heat exchange system – a vapor compression refrigeration system that compresses a vapor refrigerant in the system to achieve cooling.
The main components of the vapor compression refrigeration cycle are the compressor, condenser, expansion valve/throttle valve, and evaporator. The refrigeration process is looped in a cycle in which a special working fluid, refrigerant, undergoes four stages. First, the compressor squeezes refrigerant to raise its temperature. Second, the gas is then directed through heat dissipation coils, which release heat outside the object. Third, the refrigerant cools and condenses back into a liquid when it dissipates its high temperature. Fourth, this condensed liquid goes through a high and low-pressure threshold called an expansion valve. Going through this threshold causes the refrigerant liquid to expand and turn back into gas form. The final aim of the cycle is to continuously take heat from inside the object and transfer it outside.
The main element of the refrigeration cycle is a special liquid – refrigerator fluid. Its peculiarity is that it can boil at a low temperature and thus absorb excess heat. Refrigerants use a phase transition – boiling and condensation, through which they take away the heat of the object and, after compression, transfer it to the cooling medium. The primary refrigerants are ammonia, chlorofluorocarbons (CFCs), and hydrofluorocarbons (HFCs). However, ammonia and chlorofluorocarbons are toxic to humans and deplete the ozone layer through atmospheric emissions. Therefore, modern refrigerators use hydrofluorocarbons in a closed refrigeration cycle because they are non-toxic and do not affect the ozone layer.