Cooling effect of fluorine free refrigerant HCR-22 used in heat pipe

Abstract: In order to reduce Freon refrigerant's damage to the ozone layer and its high potential value of climate warming, an accumulation of cold source device by the detached low temperature heat pipe was designed. The heat pipe cold storage device was composed of a reservoir, heat pipe, and temperature monitoring system. The refrigerant absorbs heat from the reservoir in the evaporation section of the heat pipe followed by its gasification. After that the exchanged heat and release of latent heat of vaporization with cold air in the condensation section of the heat pipe occur followed by liquefication of refrigerant. The liquefied refrigerant flows back to the evaporation section of the heat pipe by the action of gravity. As such an automatic cycle is accomplished in this way. With continuous progress of the gasification and liquefaction for the refrigerant, the coldness resource is continuously transferred and stored in the reservoir, and the temperature of reservoir gradually decreases. In this study, we replaced the traditional refrigerant R-22 with a new type of fluorine free refrigerant HCR-22, taking cold storage capacity as an index, and conducted an experiment for 70 h. We studied the cold storage effects of two kinds of refrigerant in different liquid filling ratio and condensation/evaporation section area ratio. The test results showed that the best filling ratio of HCR-22 for low temperature heat pipe was 80%, which was the same as R-22. When the heat pipe module was running 70 h, the cold storage capacity of refrigerant HCR-22 was higher, and the cold storage capacity of HCR-22 and R-22 were 16 230.52 and 16 252.09 kJ, respectively. Under the condition of best liquid filling, HCR-22 for low temperature heat pipe of the optimal condensation/evaporation section area ratio was 2.8:1, less than 3:1 with the R-22. Obviously, the use of HCR-22 refrigerant can save more metal materials. The heat transfer stability of HCR-22 and R-22 was the same in the phase change heat transfer, and the temperature variation was smooth in the test process, but the amount of refrigerant used by HCR-22 was only 1/3 of the R-22. Being an environmentally friendly and nature refrigerant, HCR-22 was composed of carbon and hydrogen, fluorine free, and found to have zero ozone depletion potential and lower global warming potential. If the natural cold source was chosen in the middle or high latitude winter, the detached low temperature heat pipe used in this experiment may lead to the process of cold storage with low energy consumption, and low economic and environmental costs. The achievement applied in grain storage can reduce the energy consumption and the cost of refrigeration equipment with green grain storage at low temperature accomplished. This study provides evidences and technical support for the new type refrigerant HCR-22 replacing the traditional refrigerant R-22 refrigerant, and provides protection for the popularization and application of low temperature heat pipe.