Numerical Analysis of Flat Plate Solar Air Heater with Transverse Notched Rib Turbulators for Heat Transfer Enhancement

Solar air heaters are widely used for drying and space heating applications and usually have flat absorber plate for solar energy collection which makes it simple in construction and hence requires little maintenance. However, they generally exhibit low thermal performance owing to high thermal losses from the absorber plate and poor heat carrying capacity of air, which is the working fluid. Hence, there is a dire need to develop an efficient flat plate solar air heater. In this paper a two dimensional numerical analysis is conducted to evaluate the effect of notched ribs on the heat transfer augmentation of solar air heater. The design parameters that influence the performance of collector in the presence of ribs are the longitudinal pitch, geometry and dimensions of the ribs. The relative roughness pitch of is varied as 8, 10, 12 and 14 and the rib height is fixed at 1.4mm. The analysis is carried out at a constant heat flux input of 1000W/m2 for different Reynolds number conditions ranging from 8000 to 24000. The maximum increase in the Nusselt number was found to be about 1.88 times as compared to the smooth duct. The increase in thermal enhancement factor which indicates the thermohydraulic performance of the collector in the presence of ribs is found to be in the range of 1.27–1.45