Study on Collection and Retention Efficiencies of a New Integrated Collector Storage Solar Water Heating System Using a Planar Thermal Diode: An Experimental Study

Thermal diodes are a novel method to rectify the heat transfer mechanism, and this technique helps reduce heat losses in solar thermal collectors. The current study introduced a new planar thermal diode integrated collector storage (ICS) solar water heating system to analyze the effectiveness of the newly introduced thermal diode in reducing heat losses. This thermal diode ICS system utilizes water as phase change materials to transfer heat through evaporation and condensation. Three scenarios were considered to assess the dynamics of the thermal diode ICS: atmospheric-pressure and depressurized thermal diodes, P partial = 0, -0.2, -0.4 bar. The water temperature reached 40 o C, 46 o C, and 42 o C in P partial = 0, -0.2, and − 0.4 bar, respectively. The heat gain coefficients are 38.61, 40.65, and 39.26 W/K, while the heat loss coefficients are 9.56, 5.16, and 7.03 W/K in P partial = 0, -0.2, and − 0.4 bar, respectively. The optimum heat collection and retention efficiencies are 45.3% and 33.5% in P partial = -0.2 bar. Hence, there is an optimum partial pressure to achieve the best performance, equal to -0.2 bar. The acquired results illustrate the robustness of the planar thermal diode in reducing heat losses and rectifying the heat transfer mechanism.