CFD Analysis of Solar Air Heater Duct Having Broken Arc Shaped Ribs Combined with Staggered Rib Piece on Absorber Plate

The use of artificial roughness on the underside of the absorber plate is an effective and economic way to improve the thermal performance of a solar air heater. Several experimental investigations, involving different types of roughness elements, have been carried out to improve the heat transfer from the absorber plate to air flowing in solar air heaters. In this paper the CFD analysis on heat transfer and friction in rectangular ducts roughened with broken arc-rib with stagger piece has been presented. The rib roughness has relative gap position (W/W) was varied from 0.33 to 0.80 and other parameter are constant. The effects of relative gap position on Nusselt number, friction factor and thermo-hydraulic performance parameter have been discussed and results compared with smooth duct and continuous arc rib roughened duct under similar conditions. The rough ribs were efficient enough to transfer the desired heat, but they are not economical and are very complex in design and construction. Whereas, the Circular ribs with different relative gap width gives more area of contact. So, there is enough time to transfer the heat from the ribs to the passing air which touches the ribs and the heat transfer takes place efficiently. It is found that the maximum heat transfer and friction characteristic at a relative gap position of 0.65.