Enhancement of heat transfer coefficient using Diamond shaped roughness on the absorber plate of solar air heater

Solar collector (Air heater) has low thermal efficiency due to the low thermal conductivity between Air and absorber plate. So there is a need to enhance the thermal conductivity between air and absorber plate. This leads higher temperature to absorber plate and hence maximum thermal losses occurs to environment .It can be made possible by creating artificial roughness on absorber plate .There are number of parameters which can enhance the thermal conductivity such as relative roughness pitch (P/e), Reynolds no. (Re) and angle of attack ().Experimental investigation has been carried out to study heat transfer enhancement by using diamond shape as a rib on absorber plate. Electric heater is used to heat the plate in indoor experiment. Absorber plate heated with the Electric heater while three walls insulated with thermocol sheet. The relative roughness pitch (p/e) varies between 10-25 mm, the relative roughness height (e/Dh) = 0.023, Rib height (e) = 1mm, Duct aspect ratio (W/H) = 8, rate of air flow corresponds to Reynolds no.(Re) ranging from 3000-14000.Finally comparison of the heat transfer from both smooth and roughened plate under the same condition of air flow is made.