1. The critical temperature should be high and the solidification temperature should be low. The critical temperature is high, which is convenient for condensing with general cooling water or air; the freezing temperature is low, so as to prevent it from solidifying at the evaporating temperature, which is convenient to meet the cooling requirements of lower temperature
2. The evaporation temperature under atmospheric pressure should be low
3. The pressure should be moderate. The evaporation pressure is preferably close to the atmospheric pressure and slightly higher than the atmospheric pressure to prevent air from penetrating into the refrigeration system, thereby reducing the refrigeration capacity. The condensing pressure should not be too high to reduce the pressure of the refrigeration equipment, so as to avoid excessive compression power consumption and reduce the possibility of leakage in the high-pressure system
4. The cooling capacity per unit volume QV should be large. In this way, when the cooling capacity is constant, the circulating amount of refrigerant can be reduced, and the size of the compressor can be reduced.
5. High thermal conductivity, low viscosity and density. To increase the heat transfer coefficient of each heat exchanger and reduce its flow resistance loss in the system
6. The adiabatic index K should be small. It can be seen from the relationship between the parameters in the adiabatic process that when the initial temperature and compression ratio are the same
7. Has chemical stability. No burning, no explosion, no decomposition under high temperature, no corrosion to metals, no chemical reaction with lubricating oil, no harm to human health
8. The price is cheap and easy to buy. And it has a certain degree of water absorption. On the one hand, when the refrigeration system penetrates and a small amount of water, it will produce ice plugs and affect normal operation.