Conference Year



refrigerant to refrigerant heat exchanger, CO2 refrigerant cycle, evaporating performance, heat transfer


The performance of CO2 cycle is worse than that of HFC refrigerants since the working pressure of CO2 cycle is higher than that of HFC refrigerants which suffers higher compression and expansion losses. To enhance the cycle performance similar extent to HFC refrigerants, refrigerant to refrigerant heat exchangers need to be applied as one of the many components equipped. Specifically, when such a heat exchanger is used as an economizer, which works between high temperature refrigerant after the gas cooler and low temperature refrigerant by reducing to the intermediate pressure, it is confirmed from the visualization that the refrigerant flow in low temperature side is observed as a vapor-liquid dispersed flow. In such a condition, the evaporating performance is low since the liquid flows in the vapor core. In this study, aiming at weight saving and compactness, a newly designed aluminum double-tube heat exchanger in which surrounding multi-ports form instead of outside annulus is used. Spiral fins are applied in the inside tube to aim for attaching liquid refrigerant flowing in vapor core to the inside tube wall. The local heat transfer coefficient is experimentally measured in a single tube and it is confirmed that this new type heat exchanger can enhance heat transfer performance.