The cryogenic test chamber refrigeration system is very important for the quality of the refrigerant when selecting the refrigerant. Usually we will judge and select through four aspects.
First, it must have excellent thermal physical properties. The detailed requirements are to have a relatively high heat transfer coefficient, a relatively low viscosity and a relatively small density.
It is necessary to have better chemical stability. In the work, it is required that the working medium has good chemical stability at high temperature, and it must be ensured that the working medium cannot be decomposed under the highest temperature working condition.
Second, it must have good mutual solubility with frozen oil.
The most important thing is to have safety. The low temperature test chamber refrigerant should be non-toxic, non-irritating, and unable to burn and explode.
Third, the quality requirements for low temperature test chamber refrigerant (freon, refrigerant)
Must have very good good thermodynamic properties, can have higher efficiency when circulating in a given temperature range. The detailed requirement is that the critical temperature is higher than the condensation temperature, the saturation pressure corresponding to the condensation temperature does not need to be too high, the standard boiling point in the system is lower, the specific heat capacity of the fluid is small, the adiabatic index is low, and the heat per unit volume is lower. Great.
Fourth, there must be electrical insulation
Economical: requires low working quality and easy access
It must also be environmentally friendly, requiring the ODP and the Global Warming Potential (GWP) of the working fluid to be as small as possible to reduce the ozone layer damage and cause global warming.
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