PERFORMANCE EVALUATION AND CONTROL OPTIMIZATION OF A CO_2 BOOSTER REFRIGERATION SYSTEM IN SUPERMARKET

摘要

An increasing number of CO_2 refrigeration systems are applied to supermarkets as a replacement of conventional R404A multiplex systems which suffer from high direct greenhouse gas emissions. The very good thermophysical and heat transfer properties of CO_2 can also potentially lead to energy savings and reduction of indirect greenhouse gas emissions. In this paper, the performance and optimisation of a 'booster' CO_2 refrigeration system are considered. The analysis is based on the simulation of the CO_2 refrigeration cycle in a supermarket application and comparison of its performance with that of the R404A cycle. The results indicate that the CO_2 refrigeration system using controls that optimize in real time the high-pressure side of the system and the transition temperature between subcritical and trascritical operation can lead to sizeable energy savings over the conventional R404A system.