THE EFFECT OF INTERNAL HEAT EXCHANGER IN A REVERSIBLE CO2 SYSTEM UNDER VARIOUS OPERATING CONDITIONS

Abstract

The use of an internal heat exchanger (IHX) as a cycle improvement measure is very common with CO2 systems. However, a simple thermodynamic analysis is not able to fully indicate the advantages of IHX in a single-stage system. For this reason, in this paper, the effect of the internal heat exchanger on the reversible CO2 system, which can work in both air-conditioning and heating mode, was experimentally investigated. Experiments were performed under various conditions for both operating modes, with and without an internal heat exchanger. The results of the experiments showed that in the heating mode (heat pump) the coefficient of performance (COP) can be increased up to 10,5% by introducing the internal heat exchanger, while in the air-conditioning mode, the COP can be increased up to 13,8%. Also, it has been shown that this improvement provides safer system operation and less frost formation on the evaporator.