EFFECT OF ARTIFICIAL ROUGHNESS ON HEAT TRANSFER AND FRICTION FACTOR CHARACTERISTICS IN RECTANGULAR DUCT OF A DOUBLE PASS SOLAR AIR HEATER

An experimental study has been carried out to see the effect of transverse ribs attached to the absorber plate of a Double pass solar air heater on the Heat transfer and Friction factor characteristics in a rectangular Duct. The aspect ratio of the Duct (W/H) is 10. The range of Reynolds number varies from 4900 to 12000. The relative roughness pitch (p/e) is between 5-20 and fixed relative roughness height (e/Dh) 0.044 and fixed angle of attack ( �) 90°. It has been observed that maximum heat transfer and friction factor occur at relative roughness pitch (p/e) of 10 and enhancement in the heat transfer is 1.6times of the smooth plate.