Refrigeration can be defined as the process of transferring heat from low temperature region to high temperature region. In other words, it is the process of cooling the substance. This can be achieved only if heat is removed from that substance.
Principle of refrigeration: Principle of refrigeration is based on second law of thermodynamics. It states that heat doesn’t flow from low temperature body to high temperature body without the help of external work. In refrigeration process, since heat has to be transferred from low temperature body to high temperature body some external work has to be done according to second law of thermodynamics as shown below (fig 2.) Here, the external work is done by compressor, condenser etc. The machine which works under this principle and serves the purpose of refrigeration is called refrigerator. Read more