Experimental Study on Glazing Impacts on Rectification Performance of Planar Thermal Diode Integrated Collector Storage Systems

Abstract

Thermal diodes are innovative tools to rectify the heat transfer mechanism in integrated collector storage (ICS) solar water heating (ICSSWH) systems and reduce ambient heat losses. This study analyzes an innovative planar thermal diode ICSSWH and aims to determine how the glazing affects the efficiency and dynamics of planar diodes. Furthermore, the robust ability of planar diodes to rectify the heat transfer mechanism is proven. Hence, an experimental setup was fabricated and analyzed outdoors during the day to observe the planar diode’s dynamics comprehensively. The obtained results illustrate the strong effects of glazing on the dynamics and diodicity of the planar diode. The stored water obtains the highest temperature of 64 °C in the glazed scenario and 50 °C in the unglazed one. Hence the glazing improves collection and retention efficiencies in which the collection efficiency reaches 52.81% and 35.56%, while the retention efficiency has peak values of 11.04% and 3.22% in the glazed and unglazed scenarios. The partial vacuum is another crucial factor that slightly affects the stored water temperature and efficiencies compared to the glazing strategy. Hence the glazing significantly reduces ambient heat losses in the planar diode as a robust thermal rectifier.