Energy influence of the internal heat exchangers placement in a cascade refrigeration plant. A theoretical and experimental analysis

Abstract

This paper deals with the analysis of the internal heat exchanger (IHX) impact on the energy performance of a cascade refrigeration plant (CRS) made up of two vapor compression cycles. Three IHX locations have been considered, the first one in the high temperature cycle (HTC), the second one in the low temperature cycle (LTC), and the third one thermally connecting the suction line of the LTC with the liquid line of the HTC. Additionally, five refrigerant pairs R134a/R744, R290/R744, R1270/R134a, R600a/R744, and R1234ze(E)/R744 and three different heatsink temperatures: 293 K, 303 K and 313 K have been considered. The experimental results, obtained in a CRS experimental facility, are contrasted with those obtained from a theoretical model. While theoretical results predict that the IHXs have mainly negative or neglecting effects on the energy performance of the CRS, the experimental ones results show that regardless of location and operating conditions, the activation of an IHX generally improves the COP, up to 5.6 % as a maximum improvement.