A study on the use of dual mixed refrigerant in a cascade dual mixed refrigerant cycle

Abstract

In this article, a precooling cycle was used to reduce the power consumption and improve the heat transfer efficiency of a mixed refrigerant cycle. Propane precooling and mixed refrigerant precooling are two common precooling methods. The cascade dual mixed refrigerant cycle, which involves mixed refrigerant precooling and has a specific power consumption 10.9% lower than that of propane precooling, has been widely used. In order to analyze the relationships among precooling temperature, mixed refrigerant composition, and specific power consumption, the specific power consumption of a cascade dual mixed refrigerant cycle was investigated. A mixed refrigerant cooling temperature of 223 K, a precooling mixed refrigerant comprising C 2 H 6 –C 5 H 12 , and a subcooling mixed refrigerant comprising N 2 and CH 4 –C 3 H 8 yielded optimal results. In addition, a mixed refrigerant component ratio optimization model was established for the dual mixed refrigerant cycle. The results indicated that the optimum mixed refrigerant component ratios corresponded with the lowest levels of specific power consumption. Furthermore, by studying the effects of the feed gas pressure and temperature on the mixed refrigerant component ratios, the optimal operating conditions of the cascade dual mixed refrigerant cycle were determined to be 5.0 MPa and 298 K.