A refrigerant is a compound used in a heat cycle that undergoes a phase change from a gas to a liquid and back.
The two main uses of refrigerants are :
1. refrigerators/freezers and
2. air conditioners.
Earlier, fluorocarbons, especiallychlorofluorocarbons, were used as refrigerants, but they are being phased out because of they are responsible for ozone depletion.
Other refrigerants used now are ammonia, sulphur dioxide, and non-halogenated methane like hydrocarbons.