Examination of the performance effects of refrigerants in a multistage refrigeration cycle using advanced exergy analysis

Abstract

A two-stage vapor compression refrigeration system was investigated using advanced-exergy-based analysis, which examines the effects of each component and their interactions with each other for system development. The advanced-exergy-based analysis guides how much improvement can be made on the parts of the system, examining exergy destruction in the form of endogenous/exogenous and avoidable/unavoidable parts. In addition, a parametric study was conducted and the performances of different refrigerants were evaluated to analyze the system under various operating conditions. The highest exergy destruction arises as 8.1 kW for R227ea. The total compressor works decrease 0.667 kW by changing the refrigerant from R227ea to R142b. R152a shows a preferable performance along with environmentally friendly characteristics. The condenser has the most critical improvement potential with 0.869 kW, and it accounts for 31% of the total irreversibility. It is followed by the evaporator 0.734 kW (26.2%). All exergy destruction in the evaporator falls into endogenous-part. The irreversibility of the evaporator is directly related to inner inefficiency. Coefficient of performance decreases by 40% for a condenser temperature variation from 30 to 50 degrees C. An increment in the evaporator temperature from - 15 to 0 degrees C increases coefficient of performance by 49.95%. The avoidable exergy-destruction rate can be minimized by 24.89% for that temperature variation.