A parametric study on energy, exergy and exergoeconomic assessments of a modified auto-cascade refrigeration cycle supported by a dual evaporator refrigerator

Abstract

This paper presents an evaluation of the energetic, exergetic, and exergoeconomic performances of a modified auto-cascade refrigeration (MACR) cycle integrated with a dual evaporator refrigerator (DER) to determine optimum operating conditions. DER facilitates a reduction in the compression ratio, allowing the low-boiling-point component to release more heat before entering the evaporator. In this study, the R170/R290 refrigerant mixture, which has a low global warming potential but an explosion risk, was used. The main purpose of this study is to eliminate the risk of explosion by reducing the compressor discharge temperature and at the same time to enhance the overall cycle performance. To achieve this, DER is used instead of air-cooled coils, which have limited cooling performance. Despite an ambient temperature of 35°C, the MACR cycle achieved a remarkable 51.29 % reduction in compressor discharge temperature when the separator inlet temperature was reduced to 10°C by the DER. It also results in a 72.73% reduction in compression work rate and a significant 137.02% increase in cooling effect compared to the conventional auto-cascade refrigeration cycle. Furthermore, the MACR cycle exhibits notable improvements in total exergy destruction rate and exergy destruction cost rate with a 75.23% and a 76.07% reduction, respectively. Simultaneously, the exergy efficiency and the exergoeconomic factor increased by 266.67% and 179.15%, respectively. The MACR cycle achieves optimum energy and exergy performance with a 60% R170 mass fraction and 0.50 vapor quality, resulting in 1.429kW compression work rate, a COP of 0.70, and an exergy efficiency of 26.66 %. The optimum exergoeconomic performance is achieved with a 40% R170 mass fraction and 0.50 vapor quality.