Improvement of Energy Efficiency by Cascade System with CO2 Refrigerant

Abstract

The condition for calculation and compressor efficiency was quoted from previous paper [1]. The system efficiency of cascade refrigeration system is shown by formula (1) to (5). The total rate AbstractGlobal warming is commonly issue in worldwide. From point of global warming point of view, alternate HFC refrigerant to natural refrigerant is one of the means to reduce global warming gas which is used to refrigeration system in food store such as supermarket and convenience store. Carbon dioxide (hereinafter CO 2 ) is one of the dominant candidates as low Global Warming Potential (hereinafter GWP) refrigerant. However CO 2 refrigerant has lower efficiency for refrigeration because of low critical temperature. Also CO 2 refrigerant has higher system pressure than HFC refrigerant. Therefore typical cascade refrigeration system is equipped HFC refrigerant in higher temperature cycle. This report indicate the potential of CO 2 -CO 2 cascade system even CO 2 refrigerant itself has lower efficiency than HFC refrigerant. And this report shows optimization of discharge pressure, suction pressure and internal heat exchanger are important to get better performance.Keywords: CO 2 ; Carbon dioxide; Coefficient of performance; Cascade