Effect of roughness parameters on performance of solar air heater having artificial wavy roughness using CFD

Abstract

The current study used Ansys FLUENT software to perform a computational fluid dynamics analysis of a solar air heater with artificial wavy roughness. Roughness elements were studied for twelve wavy surface configurations with rib heights (e) of 0.7 mm, 1 mm, and 1.4 mm and pitch (p) of 10, 15, 20, and 25 mm. A 2D computational domain is modelled and the involved differential equations are solved using a finite volume method. To solve the transport equations for turbulent flow and energy dissipation rate, the RNG k-ε turbulence model with enhanced wall function is employed. For a uniform heat flow of 1000 W/m2, the effect of roughness parameter on Nusselt number, friction factor, and thermo-hydraulic performance parameter (THPP) is investigated. On the basis of the THPP, the best geometric parameter values are found in the Reynolds Number (Re) range of 3800–18,000. At Re of 12,000, the optimal THPP is 1.96, which corresponds to a rib height of 0.7 mm and a pitch of 15 mm.