Thermodynamic analysis of the effect of internal heat exchanger on the dual‐ejector transcritical CO 2 cycle for low‐temperature refrigeration

The use of CO2 as a refrigerant has become a trend in the development of the refrigeration industry. Refinement of new layout and improvement of cycle performance remains a major research direction, which coupling ejector and internal heat exchanger with the transcritical CO2 cycle is a popular method. In this paper, the issue of the effect of different positions of the internal heat exchanger on the dual-ejector transcritical CO2 refrigeration cycle is discussed. The dual-ejector cycle is evaluated both thermodynamically and economically by means of multi-parameter optimization, which is compared with conventional two-stage transcritical CO2 refrigeration cycle. The obtained results show that the COP of the dual-ejector transcritical CO2 refrigeration cycle is on average about 42% higher than that of the conventional two-stage transcritical CO2 refrigeration cycle. Adding internal heat exchanger at different locations cannot improve the performance of dual-ejector transcritical CO2 refrigeration cycle system in low-temperature refrigeration. In addition, the exergy and economic analysis shows that the dual-ejector transcritical CO2 refrigeration cycle has better exergy efficiency, and the increase of internal heat exchanger is an unfavorable exergy efficiency. The exergy destruction rate and the total cost of the dual-ejector system are on average 58% and 19% lower than that of the conventional cycle, respectively. At the same time, the addition of internal heat exchanger has very little impact on the total system cost.