Development of cascade non-flammable mixed refrigerant Joule-Thomson refrigerator for 100 K

Abstract

In this paper, a cascade type non-flammable mixed refrigerant (MR) Joule-Thomson (JT) refrigerator is suggested to achieve 100 K cooling temperature. The working fluid utilized in the main stage (low temperature cycle) of the MR JT refrigerator is composed of nitrogen (N2), argon (Ar), Tetrafluoromethane (R14) and Octafluoropropane (R218). An azeotropic mixture of R32 and R125 (R410A) is used for the precooling stage (high temperature cycle) refrigerant where the cooling temperature is nearby 240 K. The design specifications of the refrigerator are modeled by using a commercial software with Peng–Robinson equation of state (EOS). The maximum COP of the optimized MR JT refrigerator is obtained as 0.24, at the temperature of 106.6 K. Also, this MR JT refrigerator is fabricated and tested to investigate the refrigeration performance in comparison with the simulated results. The compression system of the refrigeration cycle is installed by modifying commercial air-conditioning compressors. The R410A precooling stage is simulated by a commercial Stirling cryocooler. The feasibility of the non-flammable MR in the MR JT refrigerator is validated by achieving the lowest temperature of 97.8 K, which is even below the freezing point of pure R218 (125 K).