Thermo-exergy performance analysis of an evacuated tube solar air heating system with phase change material storage

Abstract

This study systematically investigates the performance of a solar-assisted heating system integrated with latent heat storage (LHS) using paraffin wax as a phase change material (PCM) and evacuated tube solar collectors. The system is designed for agricultural drying applications, using air as the heat transfer fluid (HTF) and vertical fins to enhance heat transfer within the storage unit. Experimental measurements were conducted by using calibrated thermocouples, anemometers, and an Arduino-based data acquisition system that measure temperature variations throughout the experimental setup. The results demonstrate that increasing the HTF flow rate substantially enhances the thermal output and efficiency of the system, with a peak efficiency of 32% achieved at 39.6 m/s. In comparison with the system without the LHS, the PCM integrated system effectively stabilizes the outlet air temperature and reduces thermal loss, thus making it better for continuous drying operations. This study provides a new insight into dynamic nature of mass flow rate and phase transition behavior of paraffin, demonstrating that a variation in mass flow rate significantly affects the paraffin’s melting and solidification kinetics, which directly governs paraffin’s thermal effectiveness. The system maintained consistent outlet air temperatures for drying applications both during day-time and off-day time operations, confirming the systems capability for extended drying cycles. This work advances current knowledge by experimental integration of evacuated tube collectors and LHS systems and proves that their synergic application is very efficient for agricultural drying and for any other thermal applications.