An Experimental Analysis of Cycling Losses in Domestic Refrigerator-Freezers

This report identifies and quantifies the cycling losses in a domestic refrigerator-freezer. During cycling operation the refrigerator was found to operate between 5 and 25% less efficient then the corresponding quasisteady machine. The cycling refrigerator operates with an evaporator capacity between 3 and 17% less than the quasi-steady refrigerator, while at the same time requiring between 1 and 9% more power to operate. This refrigerator performance degradation was attributed to several factors, the most important being the refrigerant migration and the thermal mass of the evaporator and compressor. During the off-cycle refrigerant migrates from the condenser to the evaporator as the system pressures equalize. The off-cycle migration increases the temperature of the evaporator and necessitates refrigerant redistribution during the on-cycle, and thereby tends to reduce system performance. The increased power requirements, traced to the compressor, result from slight differences in system pressure and the reduced compressor efficiency due to a cool compressor. With the cycling losses identified, several possible refrigerator design changes were suggested. It appears that a refrigerator equipped with a reciprocating compressor, solenoid valves to isolate the condenser, and no accumulator should operate in a nearly quasi-steady manner. In addition using the condenser fan to accelerate charge redistribution was investigated. However, since the experimental refrigerator was equipped with an accumulator which held up some charge manipulating the condenser fan showed little payoff.Air Conditioning and Refrigeration Center Project 3