Study on open-cycle carbon dioxide refrigerator for movable mine refuge chamber

For a movable mine refuge chamber, the refrigeration system is important to remove minersʹ body heat and the heat input from the hot outside environment. The refrigeration cycle has been changed from closed cycle using traditional Freon refrigerant to open cycle using high pressure carbon dioxide. The open cycle refrigerator has no compressor and it consumes no electricity. The open system is composed of a Joule–Thomson (JT) valve, an evaporator, a capillary heat exchanger, a pneumatic blower and several connecting tubes. For the evaporator, a stainless steel heat exchanger as well as a smooth tube heat exchanger were designed and tested and compared with a conventional finned tube copper heat exchanger. The tests show that the performance of cooling and dehumidification is nearly the same for the three heat exchangers. Because the stainless heat exchanger has higher strength and lower cost than the two others, it might be the best choice in actual applications. A long capillary tube heat exchanger is used to decrease the carbon dioxide pressure from around 20–35 bar to 5 bar, and at the same time the gas is kept above a temperature of 10 °C by making use of the sensible heat.