Variation of Nusselt Number and Friction Factor in a Double Pass Solar Air Heater Having Discrete W-Shaped Ribs

This paper shows the effect and variations of artificial roughness mounted over a Double pass solar air heater in the form of discrete w-shaped ribs over the absorber plate. The experimental work was carried over a rectangular duct. The aspect ratio(W/H) of the duct was taken as 10. Various parameters were taken to see the variation and enhancement in Nusselt number and friction factor in comparison to the smooth plate. For the experimentation the relative roughness pitch (p/e) was taken between the range of 5 to 20. Range of Reynolds No. varies between 4500 to 12000. The relative roughness height (e/Dh) was taken as 0.044 with a single angle of attack (α) of 60˚.For the experimentation the relative gap width(g/e) was taken between 0.5 to 2.0. It has been observed from the experimentation that Nusselt number and friction factor characteristics is highest at p/e of 10 with the value of g/e being at 1.0. This paper presents the variation of various parameters like Nusselt No. and Friction factor with Reynold's no. at an angle of attack (α) of 60˚ in discrete w-shaped ribs placed over the absorber plate on both of its side keeping p/e ranging from 5-20 and g/e kept constant at 1. This paper also shows the variation of these parameters for p/e kept constant at 10 with relative gap width(g/e) ranges from 0.5-2.0