Performance Investigation of a Solar Air Heater Artificially Roughened with Joukowski Airfoil Ribs

Abstract

This paper investigates a solar air heater's thermohydraulic and thermogeometric performances with an artificially roughened absorber plate with Joukowski airfoil ribs. The rib height and shape have a bearing on the overall performance of the air heater. Joukowski airfoil ribs of different sizes are generated from a circular rib of a radius of 1mm using conformal mapping. Simulations are performed for the turbulent flow of air through the roughened duct in the Reynolds number (Re) range of 4000 = Re = 15000 using ANSYS Fluent version 2020. The renormalization group kinetic energy-turbulence dissipation rate (RNG κ-ε) model with enhanced wall treatment (EWT) has been employed to model the turbulent flow. The grid refinement study is performed to optimize the mesh size and estimate the numerical solution error. The proposed rib design is tested for both headwind and tailwind flow arrangements. The tailwind performance is better for smaller-size Joukowski ribs. However, the medium and large-size Joukowski ribs perform better in headwind configurations. At low Re, heat transfer is more dominant than friction leading to higher thermohydraulic performance, whereas, at high Re, the reverse trend is observed.