EFFECTIVE EFFICIENCY ANALYSIS OF ARTIFICIALLY ROUGHED SOLAR AIR HEATER BY DIAGONALLY CHAMFERED CUBOID ARRAY

Abstract

The solar air heater (SAH) is a very simple and economical device, but its thermal performance is quite poor. Boosting the heat transfer between absorber plates and the airflow can improve the thermal performance of a solar air heater. 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 utilized as roughness elements to investigate the enhancement of the performance of a solar air heater. This roughness is achieved by attaching diagonally chamfered cuboids to the absorber surface. A thorough experimental investigation was carried out to examine how this roughness affects the performance of solar air heaters. The study considered several parameters, such as relative roughness pitch (RRP) (5 to 8), arm length of cuboid (ALC) (4 to 10 mm), and relative roughness height (RRH) (0.44 to 0.077). To ensure turbulent flow during the experiment, the Reynolds number was kept within the range of 4250 to 18,000, which is considered ideal for solar air heaters operating with a constant heat flux of 1000 W/m<sup>2</sup> on the absorber plate. An overall performance assessment of the artificially roughened solar air heater was conducted, which included analyzing the Nusselt number and friction factor for both roughened and smooth absorber surfaces operating under similar flow conditions. The maximum Nusselt number achieved was 3.68 times higher than that of the smooth absorber plate at Re = 4250, with roughness parameters RRP = 5, RRH = 0.077, and ALC = 10. The analysis also reveals a 2.48-fold improvement in the overall performance of the roughened configuration.