Experimental investigation on a non-flammable mixed refrigerant Joule-Thomson refrigerator for a 100 K cooling temperature

A non-flammable mixed refrigerant Joule-Thomson refrigerator is developed for a cooling temperature of 100 K without freezing of the working fluid itself. A mixture of nitrogen, argon, tetrafluoromethane (R14, CF4), and octafluoropropane (R218, C3F8) is selected as the working fluid of the cascade type Joule-Thomson refrigerator. The optimized composition of the mixed refrigerant components is determined as N2:Ar:R14:R218 = 0.2:0.3:0.3:0.2 which has the freezing temperature of lower than 77 K according to our previous research. The coefficient of performance was obtained as 0.162 with 60 % isentropic efficiency based on the numerical simulation with aforementioned composition in the cascade configuration. As a result, the lowest temperature of 98.5 K is realized, and the maximum cooling capacity is 15 J/g at 103 K, which is the normalized value with respect to the mass flow rate of the working fluid. Additionally, the inefficiency of the experimental apparatus is analyzed and the possibility of further improving the coefficient of performance is proposed. Additionally, the inefficiency of the experimental apparatus is analyzed and the possibility of further improving the COP is proposed. This paper demonstrates that the non-flammable mixed refrigerant Joule-Thomson refrigerator can achieve cooling temperature of 100 K, below the freezing point of its pure components. It confirms the potential of using non-flammable mixed refrigerant Joule-Thomson refrigerators in large-scale industries, such as high-temperature superconducting transmission cable industries, semiconductor manufacturing, or bio-preservation fields.