Investigation on the optimal control of gas cooler pressure for a CO2 refrigeration system with an internal heat exchanger

CO2 is one of good refrigerants considering the environmental and safe issues. However, its control is a much more complicated problem compared to the conventional refrigerants. Most of the previous studies have applied regressive approach to this problem, but it requires large amount of effort and cost. This study deals with issues on controlling CO2 refrigeration system and developing new control method. In this study, the performance characteristics of a CO2 refrigeration system were investigated considering refrigerant charge amount and a novel real-time control method proposed by Kim and Kim (2012) was validated. Through the validation, the real-time controller showed acceptable estimation performance even in case of insufficient refrigerant charge. In addition, a new concept of control analysis was devised considering gas cooler performance. This approach helps the comprehensive understanding of determination mechanism to achieve maximum coefficient of performance, which is applicable to develop a new control method.