DOI: 10.11648/j.ijfmts.20261203.13 ISSN: 2469-8113

Design Optimization and Performance Evaluation of a Cascade Refrigeration System for Ultra-Low Temperature Applications

Ronit Bk
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This study presents the design and performance analysis of a cascade refrigeration system aimed at achieving ultra-low temperatures of -80°C, essential for vaccine storage and cryogenic applications. Cascade refrigeration systems are widely used for such applications because they reduce compressor work and improve overall efficiency compared to single-stage systems, particularly when a large temperature lift is required. The system analyzed in this study utilizes R-134a in the upper-temperature circuit and investigates the performance of four candidate refrigerants — R-13, R-23, R-170, and R-290 — in the lower-temperature circuit. Thermodynamic simulations were conducted using Engineering Equation Solver (EES) to determine the coefficient of performance (COP) of each circuit and the overall system, along with the corresponding refrigerant mass flow rates, under a fixed set of operating conditions. The results show that R-23 yields the highest overall COP of 1.816, outperforming R-13 (1.538), R-170 (1.704), and R-290 (1.695), owing to its superior lower-circuit COP of 5.758. A parametric study further examined the effect of evaporator temperature and ambient temperature on system performance, showing that overall COP declines as the evaporator temperature is lowered from -20°C to -50°C, while the lower-circuit COP improves over the same range. Heat transfer analysis highlights the significance of insulation properties, with an estimated cooling load of 72 kW for a 1 m³ chamber at an ambient temperature of 40°C, based on a polyurethane foam insulation layer of 0.25 m thickness. The findings emphasize the critical role of refrigerant selection in enhancing efficiency and operational stability, contributing to sustainable and energy-efficient refrigeration solutions for ultra-low-temperature storage applications such as vaccine preservation.

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