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 discrete angled rib geometries has been analyzed using Computational Fluid Dynamics (CFD). The effect of this geometry on heat transfer and friction factor and performance enhancement was investigated covering the range of roughness parameters, P/e=8, e/D=0.043, d/W=0.25, g/e=1.0, α=60° and working parameters (Reynolds number, Re from 2,000 to 20,000). 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.
Keywords: CFD, Solar Air Heater Duct
Article published in International Journal of Thermal Technologies, Vol.3, No.2 (June- 2013)