Analyzing the influence of bump‐shaped roughness elements on the thermal performance and hydraulic characteristics of equilateral triangular solar air heaters

Abstract Conventional solar air heaters give poor performance due to poor convective heat transfer from the absorber plate, and artificial roughness is an alternate method of enhancing convective heat transfer through the Solar Air Heaters (SAH). This study proposes the new improved solar air heater having hemispherical‐shaped bumps as artificial roughness on the absorber plate with a triangular cross‐sectional flow passage for enhancing its performance. The roughness is arranged in a rectangular pattern depending on the roughness parameters, that is, bump‐height ratio (varies from 0.02 to 0.04), longitudinal pitch ratio (varies from 4 to 16), and transverse pitch ratio (varies from 6 to 14), and different configurations of these roughness parameters were simulated numerically using ANSYS Fluent software. Results of the simulation were validated with experimental results, which showed a maximum error of 6.5%. The secondary flow associated with the roughness improves the local turbulence that leads to better heat transfer with higher pressure loss in comparison to the conventional. The proposed design increases thermal augmentation by 2.48 times at the expense of 3.39 times higher friction factor at a bump‐height ratio of 0.04, a longitudinal pitch ratio of 10, and a transverse pitch ratio of 10.