Analysis of heat transfer and fluid flow in different shaped roughness elements on the absorber plate solar air heater duct

An artificial roughness on the heat transfer surface in the form of projections mainly creates turbulence near the wall or breaks the laminar sub-layer and thus enhances the heat transfer coefficient. In the present work the performance of a solar air heater duct provided with artificial roughness in the form of thin circular wire in V-shaped, Multi v-shaped ribs and Multi v-shaped ribs with gap geometries has been analyzed using CFD. The effect of these geometries on heat transfer and friction factor and performance enhancement was investigated covering the range of roughness parameters V-shaped, Multi v-shaped ribs, Multi v-shaped ribs with gap and working parameters. Different turbulent models have been used for the analysis heat transfer and friction factor and their results are compared with Dittus-Boelter Empirical relationship for smooth surface. Renormalization k-epsilon model based results have been found in good agreement and accordingly this model is used to predict heat transfer and friction factor in the duct.