Thermodynamical analysis of an auto cascade cooling cycle in a refrigerator

In this study, a new auto-cascade refrigerating cycle is proposed. Two separate evaporation temperatures can be obtained by a single compressor, the vapor phase of the working fluid from the refrigerant evaporator is separated and condensed again, and sent to the low-pressure freezer evaporator. R290/R600a, which is a zeotropic mixture as a cycle fluid, is used as a working fluid, and the thermodynamic properties of the mixture were determined using the REFPROP database. The variation of cycle performance and total cooling capacity are investigated in terms of the refrigeration loads and the mixture ratio. With the use of the auto-cascade cycle, it was observed that the compressor suction pressure increased, the compression pressure ratio decreased and the total cooling capacity increased. When the refrigerant load reached 64% of the total cooling load, the increase in efficiency coefficient was around 29.5% and the increase in total cooling capacity was around 41.1%. The results show that by using auto-cascade refrigeration systems, two different temperatures can be achieved and cycle performance and total cooling capacity can be increased.