Enhancing the Thermal Performance of a Triangular-Tube Solar Air Heater through Geometric Modifications

The thermal performance of a solar air heater featuring triangular tubes with an impingement-return flow is highly dependent on its geometric design. This study extends prior numerical analysis by systematically evaluating the impact of specific geometrical parameters on the collector's efficiency. A comprehensive stationary ۳D model, employing the finite element method (COMSOL Multiphysics), is utilized to simulate conjugate heat transfer, turbulent forced and free convection airflows using the RNG κ-ε model, and heat exchange by surface radiation. The governing parameters under scrutiny are the ratio of the inlet to total cross-sectional area and the vertex angle (which is a function of the height-to-base ratio) of the triangular ducts, whose total cross-sectional area is kept constant. For the studied test cases, numerical findings revealed that decreasing the area ratio from ۲/۳ to ۱/۳ improves thermal efficiency by ۱۳%, while decreasing the vertex angle from ۱۰۰° to ۵۰° improves it by ۱۴%. Under a solar irradiance of ۸۰۰ W/m² and an air mass flow rate of ۰.۰۲۵ kg/s, the proposed triangular-tube heater demonstrated superior performance, achieving a thermal efficiency of ۸۶%. This compares to ۷۴% for an equivalent circular tube and ۴۶% for the conventional flat-plate collectors.

کلیدواژه ها:

Area Ratio ، Solar air heater ، Thermal efficiency ، Triangular ، vertex angle