Annual energetic evaluation of multi-stage dedicated mechanical subcooling carbon dioxide supermarket refrigeration system in different climate regions of China using genetic algorithm

Abstract

Supermarket is the main carbon producer due to the requirement of food refrigeration and freezing. In order to realize cleaner production, three configurations of carbon dioxide booster refrigeration system integrated with multi-stage dedicated mechanical subcooling (DMS) applied in commercial supermarkets in different climate regions of China are proposed in this study. Thermodynamic and cooling load models are established to study the energetic operation performance of proposed systems. The energy efficiency of the systems is optimized employing the method of genetic algorithm with the optimization variables of subcooling degree, discharge pressure and intermediate pressure. Meanwhile, the baseline, single-stage DMS and R404A refrigeration systems are compared with the multi-stage DMS systems. Results indicate that the coefficient of performance of the three-stage DMS system is 1.12–28.84% higher than the baseline system at the ambient temperature of 0–40 °C, and it also operates at the lowest discharge pressure. Furthermore, a switch parallel compression is added to get high energy efficiency in different ambient temperature ranges, which is compared with the R404A refrigeration system that is one of the extensively used in Chinese supermarkets. The annual performance factor of the three-stage DMS system combined with a switch parallel compression is 10.92% and 7.62% higher than the R404A refrigeration system and baseline system in Haikou, respectively. Consequently, a carbon dioxide booster refrigeration system integrated with a multi-stage DMS system can achieve a prominent performance especially for a three-stage DMS system, which can overcome the drawback of the lower efficiency of the baseline system in hot and warm regions. A multi-stage DMS system is a promising solution for commercial supermarket refrigeration and socially sustainable development.