Thermal Performance Analysis of a Novel U-Tube Evacuated Tube Solar Collector

Solar water heating (SWH) systems are the most common application of renewable energy technology that converts solar radiation into useful energy for domestic/industrial activities. The novelty of this study is the design of a new SWH that combines the heat transfer and storage both in a single unit. The selected type of collector for this purpose is an evacuated tube solar collector (ETC). The new design of the ETC has been developed by applying a U-tube inside the collector which contains the heat transfer fluid (HTF). The HTF flows into an external heat exchanger that transfers heat to the water. The implementation of sugar alcohol namely Erythritol (C4H10O4) as the HTF for moderate operating temperature applications was investigated. Moreover, the utilization of solid-liquid phase change material, Tritriacontane paraffin (C33H68), inside the ETC, allows direct heat storage on the system and delayed release of heat. A computational fluid dynamics (CFD) modeling of a single U-tube ETC is performed using ANSYS Fluent in stagnation (on-demand) operation. A 3D model of the ETC is developed and the appropriate boundary conditions are applied. Moreover, the thermal performance comparison of U-tube vs heat pipe ETC has been done. The results from this study shows the maximum fin temperature difference of 46°C of U-tube ETC compared with heat pipe ETC.