Heat transfer and flow behavior in solar thermal collector equipped with obstacles

Abstract

Solar energy, an inherently pure and abundant source of power, is integral to a myriad of daily activities. Among the various solar thermal systems, Solar Air Heaters (SAHs) are often esteemed for their economic viability and practical utility in heating spaces and drying the products.. However, sometimes the conventional SAHs are criticized for their poor performance and capability in heat transfer, making them not well organized in application. The introduction of a new method of improvement in the efficiency of heat transfer in SAHs using carefully designed obstacles with sharp corners is presented in this paper. The obstacles are conceptualized in a Triangular winglet configuration, type-based on the following: Type 1 (Single Triangular winglet), Type 2 (Dual Triangular winglet), Type 3 (Triple Triangular winglet), and Type 4 (Quadruple Triangular winglet). The setups' empirical configurations were processed for the SAH duct where the experiments were executed with a Reynolds number (Re) up to 2000 to 16,000. The obstacle parameters such as the relative transverse pitch (Pt/b), relative obstacle height (e/H), and the relative longitudinal pitch ratio (Pl/e) were clearly maintained at 4, 0.5, and 4, respectively. From the experiments, the Nusselt number was found to be significantly enhanced, up to 3.85 for the Type 3 obstacle configuration. The Thermohydraulic Performance Parameter (η) also showed a strong value for all obstacle configurations that eventually reaches a peak value of 2.29, hence presenting a comprehensive performance for heat transfer efficiency and hydraulic performance within the SAH system.