Optimization analyses on the performance of an auto-cascade absorption refrigeration system operating with mixed refrigerants

Waste heat can be well utilized in absorption refrigeration systems. The auto-cascade absorption refrigeration system could obtain a lower temperature than that of the traditional absorption refrigeration system since the non-azeotropic mixed refrigerants with large temperature glides were used. In this article, the performance of an auto-cascade absorption refrigeration system using R23/R134a/DMF (dimethylformamide) solutions as the working substance was analyzed. Optimization analysis results showed that, to some extent, the coefficient of performance (COP) could be increased when the low pressure of the system decreased or the high pressure increased. The reasonable upper limit of the high pressure was the high pressure at the turning point of COP, and the reasonable lower limit of the low pressure was the low pressure at the turning point of COP. The COP of the system monotonously increased with the increase of the mole fraction of R23 in solutions. The low R23 mole fraction solutions were more appropriate.