Refrigerant Selection Principles

In steam compression refrigerators, refrigerant selection should not only have good thermal and physicochemical properties, but also have excellent environmental characteristics. The specific requirements are as follows:
(1) It has no destructive effect on the human ecological environment. No damage to the atmospheric ozone layer and no greenhouse effect.
(2) The critical temperature is high. It can liquefy at room temperature or ordinary low temperature. I hope that the critical temperature is much higher than the ambient temperature in order to reduce refrigerant throttling loss and improve cycle economy.
(3) Within the working temperature range, there should be an appropriate saturated steam pressure, and the minimum evaporation pressure should not be lower than atmospheric pressure to prevent external air from infiltrating the system; The condensation pressure should not be too high, otherwise it will increase the power consumption of the compressor and require the system to have high pressure capacity, increasing equipment costs.
(4) Large refrigeration capacity per unit volume. It can reduce the gas delivery volume of the compressor.
(5) Low viscosity and density. Reduce the loss of flow resistance in the system.
(6) High thermal conductivity. It can improve the heat transfer coefficient of the heat exchanger, reduce the heat transfer area of the heat exchange equipment, and reduce material consumption.
(7) Non flammable, non explosive, non-toxic. It does not corrode metal materials, does not chemically react with lubricating oil, and does not decompose at high temperatures.
(8) The isentropic index is small. It can reduce the exhaust temperature, reduce the power consumption during the compression process, and is beneficial for safe operation and longer service life.
(9) Low solidification temperature. Avoid solidification at evaporation temperature.
(10) Has good insulation performance.
(11) Low price and easy to obtain.
(12) The compression work per unit volume is small.
At the time of publication, refrigerants that fully meet the twelve requirements mentioned above have not yet been discovered. But when choosing, comprehensive consideration can be given based on the purpose, usage conditions, and other factors.
For small enclosed compressor household devices, fluorine refrigerants are often used. Large industrial refrigeration often uses ammonia, while petrochemical industry often uses hydrocarbons.