A Review on Augmentation in Thermal Performance of Solar Air Heater

Abstract

Low thermal efficiency is the remarkable drawback of solar air heaters. They have remarkable importance for low temperature applications. In a solar air heater due to formation of laminar sublayer between absorber plate and the flowing air convection coefficient of heat transfer is small. The laminar sublayer form on the absorber plate can be braked by applying the rib roughness of distinct shape and sizes due to which turbulence in the flowing air increases tremendously due to which friction factor increases between absorber plate and flowing air, resulting in increment in the convection coefficient of heat transfer and pressure drop. Design considerations of solar air heater, rib roughness geometries, fluid flow conditions and their effect on the turbulence, absorber plate temperature, convection coefficient of heat transfer and other thermo-hydraulic augmentation parameters have been minutely discussed. In this review, ongoing research and development on thermo-physical properties of solar air heater and effect of distinct roughness’s over absorber plate on heat transfer augmentation is summarized and to provide viewpoint for future research and development.