Experimental Investigation of a Two-Stage Cascade Refrigeration System using different Capillary Combinations

A cascade system integrates two vapor compression cycles connected through an intermediate heat exchanger, enabling effective heat transfer between the stages while minimizing exergy losses. This paper presents the experimental analysis of a two-stage cascade refrigeration system using R134a and R32 as refrigerants in the low and high temperature cycles, respectively. The objective is to achieve ultra-low temperature refrigeration with enhanced energy efficiency and reduced environmental impact. In this study, two different capillary tube combinations of different diameters were employed to evaluate and compare the performance of cascade system. The cascade system's performance was tested under varying ambient temperatures. In our present experimental work, performance evaluation of cascade system was carried out by measuring key parameters such as coefficient of performance, refrigeration capacity, compressor input work and heat rejection rate. The results showed that maximum actual refrigeration capacity of 0.991 kW and heat rejection rate of 5.496 kW was achieved at an ambient temperature of 32°C. At this condition, the system also exhibited the lowest compressor work of 1.238 kW with minimum temperature attained as -24°C. The experimental results indicate that the cascade system offers superior thermodynamic efficiency compared to conventional single-stage systems, particularly at lower temperature ranges. R134a/R32 refrigerant combination proved to be a viable and environmentally friendly option, making the system suitable for applications like biomedical storage, cryogenics and low-temperature industrial processes.