In the steam compression refrigerator, the refrigerant selection should have excellent environmental characteristics besides the better thermodynamic and physicochemical properties. The specific requirements are as follows:
(1) The Human ecological environment has no destructive effect. Does not destroy the atmospheric ozone layer, does not produce greenhouse effect.
(2) The critical temperature is higher. Can be liquefied at normal temperature or at low temperatures. It is hoped that the critical temperature is much higher than the ambient temperatures, so as to reduce the loss of refrigerant throttle and improve circular economy.
(3) in the operating temperature range, with adequate steam pressure, the minimum evaporation pressure should not be lower than atmospheric pressure, lest external air infiltration system; condensation pressure should not be too high, or will cause the compressor consumption increase, and demand that the system has a higher pressure capacity, increase equipment costs.
(4) The unit volume refrigeration capacity is large. Can reduce the compressor gas transmission.
(5) The viscosity and density are small. Reduce the loss of flow resistance in the system.
(6) High thermal conductivity. The heat transfer coefficient of heat exchanger can be improved, and the heat transfer area reduces the material consumption.
(7) Not combustion, no explosion, non-toxic. To the metallic materials do not corrode, the lubricant does not take place chemical action, the high temperature does not decompose.
(8) The entropy index is small. can reduce the exhaust temperature, reduce the compression process consumption, favorable safe operation and improve the service life.
(9) The solidification temperature is low. Avoid solidification at evaporation temperatures.
(10) Good insulation performance.
(11) Low price and easy access.
(12) The unit volume compression work is small.