Thermodynamic Effects of Subcooling and Superheat on a Cascade Cooling System

Abstract

This research presents laboratory results for a cascade refrigeration system CRS to determine the effects of superheating at 4°C on the system's performance rate. The results confirmation curves for the cooling room temperature, suction line pressure, expansion valve opening percentage, and superheat in the low-pressure cycle LPC, and suction line pressure in the high-pressure cycle HPC. The results of valve opening percentage and superheat in LPC when using R32, and the mixture of 90% R32 and 10% R600A by mass, were compared. Also this research proves that the amount of superheat has a significant impact on energy savings and resource sustainability. To avoid energy waste by refrigeration equipment, this research proves the great importance of knowing the optimal value of the superheat in the suction line to maintain the most important element in the refrigeration cycle, which is the compressor, as the entry of the refrigerant liquid into it is avoided for all stages of refrigeration, gradually to reach the required temperature. In the first experiment, the R407c curve decreases from a value of 3.07 bar to 2.83 bar. As for the second experiment in HPC, the suction line pressure shows the highest pressure in the curve for R407c when using the mixture at a value of 3.18 bar. The results confirm that superheat has a direct relationship to reducing the operating cost of CRS and reaching the required temperature in the cooling room in the shortest possible time, by controlling the percentage of opening of the electric valve. Therefore, we recommend focusing on more extensive research regarding the relationship between controlling the valve opening ratio and superheat before the refrigerant enters the compressor