Abstract

The thermodynamic performance of ultra-low-temperature vapor-compression cascade refrigeration systems (CRS) using low-global warming potential (GWP) refrigerants was systematically investigated through experimental measurements and steady-state simulation. The study evaluated various refrigerant combinations in the high-temperature circuit (HTC: R513A, R515B, R466A) and low-temperature circuit (LTC: R472A, R1150), focusing on the influence of evaporator and condenser temperatures on system efficiency, compressor work, and mass flow rates. Results show that system COP decreases with increasing condenser temperature, from 2.86 at 80 °C to 2.34 at 130 °C, due to higher HTC condensing pressures, elevated interstage temperatures, and increased total compression work. Conversely, increasing the evaporator temperature from −100 °C to −55 °C enhances LTC cooling capacity and reduces LTC compressor work, while slightly increasing HTC work, thereby improving overall system COP. Among the tested refrigerant pairs, R515B-R472A consistently achieved the highest COP (simulation: 2.86–2.73; experimental: 1.67–1.14) and lowest total compressor work (simulation: 3.50–3.61 kW; experimental: 1.62–2.00 kW), attributed to R472A's high latent heat and temperature glide, which improve cascade heat-exchanger matching, and R515B's moderate HTC discharge pressures. System energy consumption was also strongly affected by storage conditions, with low-load operation reducing LTC and HTC compressor work substantially. Simulation predictions closely captured experimental trends, with COP overestimated by 5–12% due to idealized assumptions, yet providing a reliable tool for parametric analysis and design optimization. The study demonstrates that optimal refrigerant pairing and precise thermal management can enhance CRS energy efficiency by up to 18% while minimizing environmental impact.

Key Points