Effective Efficiency Analysis of Artificially Roughed Solar Air Heater

The solar air heater is a very simple and economical device, but its thermal performance is quite poor. The thermal performance of a solar air heater can be enhanced by increasing the heat transfer between absorber plates and blowing air. Applying artificial roughness to the absorber plate is a unique method for improving the thermal performance of solar air heaters compared to other methods. In this study, diagonally chamfered cuboids were used as roughness elements to investigate the enhancement in the performance of a solar air heater. This roughness is achieved by attaching diagonally chamfered cuboids to the surface of the absorber plate. A thorough experimental investigation was carried out to examine how this roughness affects the perfor-mance of solar air heaters. The study considered several parameters, such as relative roughness pitch (RRP) (ranging from 5 to 8), cuboid arm length (ALC) (varying between 4 and 10 mm), and relative roughness height (RRH) (ranging from 0.44 to 0.077). To ensure turbulent flow during the experiment, the Reynolds number was kept within the range of 4250 to 18000, which is considered ideal for solar air heaters operating with a constant heat flux of 1000 W/m² on the absorber plate. An overall performance assessment of the artificially roughened solar air heater was conducted, taking into account the analysis of the Nusselt number and friction coefficient for both roughened and smooth absorber surfaces operating under similar flow conditions. The analysis reveals 2.48 times improvement in performance of the roughened configuration.