Cooling processes are carried out by chillers. The main components of chillers are: refrigerant, compressor, expansion valve, evaporator, and condenser. The refrigerant absorbs heat from one environment and transfers it to another. In general, the refrigerant is expected to have the following properties.
• It should have a high latent heat of vaporization and a sufficiently low evaporation temperature.
• It should have a high critical temperature and pressure.
• It should not pollute the environment and should not damage the ozone layer.
• It should not be chemically active, should not react with piping materials or the oil used, and should not degrade the properties of the oil.
• It should not decompose chemically and should not be flammable, explosive, or toxic.
• It should be inexpensive.
• It should have properties (such as odor or color) that allow leaks to be easily detected in case of leakage.
• It should have a small specific volume and low viscosity.
The main refrigerants used today: R134a: R134a (CF2CH2F) is the closest alternative refrigerant to R12 in terms of thermodynamic and physical properties. For low temperatures, two-stage compression is required. It has a zero ozone depletion potential and is one of the most commonly used refrigerants today. It is used in vehicle air conditioners and in domestic and commercial refrigeration systems. Since it is not compatible with mineral oils, it must be used with polyolester or polyalkylene glycol-based oils.