The Role of Internal Heat Exchanger in an R744 Vapor Compression System in the Air-conditioning Mode Under Various Conditions

This paper first presents a comprehensive review of the internal heat exchanger, followed by the discussion of experimental results of the role of an internal heat exchanger in an R744 air conditioning system. The effects of refrigerant charge amount on the performance of both basic and internal heat exchanger systems were investigated.

Also, the control equations of COP-maximizing high-side pressure were developed and used for both systems. The experimental data show up to 13.8% improvement in efficiency by introducing the internal heat exchanger. The different roles of IHX in sub- and transcritical modes and the reason for the difference are discussed in the paper.