A refrigerant is a substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle. In most cycles it undergoes phase transitions from a liquid to a gas and back again. It is a Refrigerating fluid used for heat transfer in a refrigerating system which absorbs heat at a low temperature and low pressure of the fluid and transfers heat at a higher temperature and higher pressure of the fluid, usually involving changes of state of the fluid
Properties of Refrigerant.
1) The refrigerant should have low boiling point and low freezing point.
2) It must have low specific heat and high latent heat. Because high specific heat decreases the refrigerating effect per kg of refrigerant and high latent heat at low temperature increases the refrigerating effect per kg of refrigerant.
3) The pressures required to be maintained in the evaporator and condenser should be low enough to reduce the material cost and must be positive to avoid leakage of air into the system.
4) It must have high critical pressure and temperature to avoid large power requirements.
5) It should have low specific volume to reduce the size of the compressor.