CFD simulation of thermal hydraulic performance of rectangular solar air heater with combination of boot rib roughness

Abstract

This paper expresses a comparison between the results of the boot and reverse boot shape roughness applied in a solar air heater. The results are found with the help of CFD simulations for different shapes of boot shaped ribs on solar air heater. The combined roughness of boot and reverse boot shape is analyzed for different parameters of geometry to increase the thermal performance of the solar air heater which are relative pitch roughness, P/eb = 7–12, angle of attack, θ = 30°, 40°, 50°, 60°, pitch of the ribs, p = 15.4–26.4 mm, the height of ribs, eb = 2.2 mm, with variations in Reynolds number, Re, ranging from 2000 to 18,000. The RNG k-ε model is used for the CFD simulation. The results shows that the increase in heat transfer rate as a result of applying the combined boot and reverse boot shape roughness in solar air heater is about 2.54 times that of conventional solar air heater, for P/eb = 11, θ = 50° and Re = 18,000. The maximum thermal hydraulic performance factor of 2.6 is achieved for combined roughness with P/eb = 11, θ = 50°, and Re = 2000.