The requirements for the working fluid are as follows:
1. A high latent heat of vaporization
2. High density of suction gas
3. Non-corrosive, non-toxic and non-flammable
4. Critical temperature and triple point outside the working range
5. Compatibility with materials of construction, with lubricating oils, and with other materials present in the system
6. Convenient working pressures, i.e. not too high and preferably not below atmospheric pressure
7. High dielectric strength (for compressors having integral electric motors)
8. Low cost
9. Ease of leak detection
10. Environmentally friendly
No single working fluid has all these properties and a great many different chemicals have been used over the years. The present situation has been dominated by the need for fluids which are environmentally friendly.
