Performance Enhancement of Refrigeration Systems Using Heat Pipe Subcoolers: An Experimental Investigation

This study investigates the performance enhancement of R134a vapor compression refrigeration systems through externally integrated heat pipe subcoolers (HPSCs). It addresses the growing demand for energy-efficient refrigeration by applying a passive subcooling technique that requires no internal system modifications. Four HPSC modules, each comprising three heat pipes and two heat sinks, were installed in series between the condenser outlet and the capillary tube. Experiments conducted at evaporator temperatures of 36°C and 42°C evaluated their effects on cooling capacity, power consumption, and coefficient of performance (COP). The results show that cooling capacity improved by 21%–37% at 36°C and 0.4%–32% at 42°C. At the optimal configuration using four HPSC modules, power consumption changed by only 0.077% at 36°C and 0.171% at 42°C. The normalized COP values increased to 1.38 and 1.32 at 36°C and 42°C, respectively, confirming the effectiveness of passive subcooling in enhancing system efficiency. Unlike previous approaches that required internal modifications or electrical power input, this study offers a simple, passive external retrofit solution suitable for practical subcooling applications without compromising system integrity.