Use of Hybrid Roughness Elements for the Augmentation of Performance in Solar Air Heaters

The utilization of fossil fuels significantly exacerbates climate change, posing a considerable challenge in the quest for sustainable renewable energy sources essential for a better future. Solar radiation is regarded as a highly advantageous renewable energy resource due to its widespread availability and environmentally sustainable nature. To capture and utilize this energy, solar collectors are employed to transform solar radiation into thermal energy. Nevertheless, inefficient heat transfer can adversely affect their performance. This inefficiency is primarily attributed to the low heat transfer coefficient caused by the formation of a laminar sublayer over the surface, which hinders effective thermal contact between the heated surface and the fluid (air). Disrupting this laminar sublayer is critical for enhancing heat transfer. Artificial roughness is acknowledged as one of the most effective passive techniques for improving the performance of solar air heating systems. Various forms of roughness are applied to the underside of the absorber plate to disrupt the laminar sublayer and induce local turbulence, thereby enhancing heat transfer. While some studies have explored hybrid roughness elements, this research specifically investigates the combination of dimpled and multi-V-shaped gap roughness to evaluate heat transfer and friction characteristics. The findings demonstrate a substantial improvement in heat transfer, with the thermohydraulic performance parameter (TPP) also being assessed to gauge overall system efficiency.