Performance evaluation of vapour compression cascade refrigeration system for storing blood plasma

Abstract

A cascade refrigeration system consists of two cycles to get the greatest possible refrigeration effect for applications requiring extremely low temperatures. The experimental examination of the cascade refrigeration system utilized for quickly freezing and storing blood products, notably plasma, was the main emphasis of this paper. This system is able to manage and apply cold storage for plasma at temperatures as low as -35oC. R410A (low temperature cycle) and R404A (high temperature cycle) are the working fluids in this system respectively, and their selection was based on their reasonable boiling point differences and rapid freezing times. These working fluids have very little ozone depletion and global warming potential, and they are non-toxic to the environment. This system performance evaluation determines the cascade refrigeration system's parameters ranging effects of variation in evaporator temperature, condenser temperature and temperature difference in cascade condenser. As the evaporator temperature increases from – 35oC to -70C at interval of 7oC, the suction pressure increased from 0.22 MPa to 0.64 MPa. The decrease in compressor discharge temperature of 30oC to 26oC resulted to decrease in discharge pressure ranging 1.62 to 1.49MPa in the high temperature cycle at constant condenser temperature of 40 0C. At varying heat exchanger temperature, all parameters reduced with exception of discharge temperature in both cycles and evaporator heat. A substantial increase in the coefficient of performance of comparable systems was found to be 3.04 (LTC) and 7.7 (HTC). At the high temperature cycle condenser, there was a total heat rejection of 6228 kJ, which could then be recycled for heating.