Thermodynamic analysis on a modified auto-cascade refrigeration cycle with a self-recuperator

This paper proposes a modified auto-cascade refrigeration cycle (MARC) with a self-recuperator. The introduced self-recuperator and associated expansion valve effectively increases the refrigerant enriched with more low-boiling component in the evaporator. This case could improve the cycle performance by further choosing appropriate design-dependent cycle parameters. The energy and exergy analysis methods are used to compare and evaluate the performance of MARC with conventional auto-cascade refrigeration cycle (CARC). The simu-lation results show that under all given working conditions, the COP and exergy efficiency of MARC are superior to those of CARC. Among R290/R170 and R600a/R1150, R600a/R1150 is much better refrigerant mixture. Under a typical working condition, the COP of MARC using R600a/R1150 is 68.17% higher than that using R290/R170. The performance improvement of MARC is more obvious when R600a/R1150 is used. Under the typical working condition, the COP of MARC is increased by 6.24% and 24.17% using R290/R170 and R600a/ R1150, respectively. When initial mass fraction of R1150 is about 0.6, the two cycles have maximum COP and exergy efficiency, and the maximum COP of MARC is 24.26% higher than that of CARC. In addition, the increase in the two-phase flow vapor quality at the condenser outlet can improve the COP, but reduce the refrigeration capacity. The COP of MARC increases by 37.56% when the quality increases from 0.4 to 0.6. It is also found for MARC that COP and refrigeration capacity are positively correlated with intermediate pressure.