Experimental research on a Joule-Thomson refrigeration cycle with mixture R170/R290 for −60 °C low-temperature freezer

This paper presents an experimental investigation on a Joule-Thomson cycle based low-temperature freezer for −60 ℃ refrigeration. Natural binary mixture ethane/propane (R170/R290) adopted in the freezer was proved feasible to get the low temperature below −60 ℃ refrigeration in the experimental research. The influences of the mass fraction ratio and ambient temperature on the system's dynamic operation characteristics in the cool-down and on–off cycle processes were analyzed in detail. The results indicated that the concentration of the mixture significantly impacted system performance. The lowest freezing temperature, fastest cool-down rate, and minimum daily energy consumption of 3.612 kW h were obtained at the optimal R170 concentration of 35%. The excessively high concentration of the low boiling temperature component R170 could contribute to a drastic increase in the discharge pressure and discharge temperature, which reduced the compressor operation reliability. The compressor worked with a high compression ratio ranging from 21.8 to 26.8 in the selected operating conditions. Hence, reducing the operating pressure and compression ratio should be the possible directions to improve the low-temperature Joule-Thomson refrigerator's performance working with R170/R290.