Volume 58

Simulation study of R123/R134a an auto-cascade refrigeration system for high heat sink temperatures Shuo Feng, Hainan Zhang, Sujun Dong, Zanjun Gao

Abstract

To achieve large temperature range refrigeration under high sink temperatures, this paper proposes an auto-cascade refrigeration (ACR) system using R123/R134a as the mixed refrigerant and conducts simulation studies. Based on Aspen Plus simulation model, the performance optimization of the auto-cascade refrigeration system under both high heat sink temperature and low heat sink temperature are investigated. Under high heat sink temperature, system performance is evaluated across R134a mass fractions of 0.24-0.34, revealing optimal COP values at 0.28-0.29 mass fraction. The evaporator-condenser analysis demonstrates that increasing heat transfer area beyond 1.32 m² yields diminishing returns in energy efficiency improvement. For low heat sink temperature, simulation results show an inverse relationship between R134a mass fraction (0.25-0.33) and system COP, with higher fractions increasing post-condensation stream dryness. Notably, when the heat sink temperature decreases from high to low, switching to single-stage vapor compression mode by closing valve VAL1 results in significantly enhanced COP compared to auto-cascade operation, demonstrating the system’s operational flexibility.

Keywords Large temperature range; Auto-cascade refrigeration; Simulation; Performance optimization