Experimental Investigations on Thermo-hydraulic Performance due to Flow- Attack- Angle in Multiple V-ribs with Gap in a Rectangular Duct of Solar Air Heaters

Abstract

An experimental investigation was carried out to study the effect of artificial roughness, in the form of multi v-shaped ribs with gap on one heated wall of a rectangular solar air heater duct, on heat transfer (Nusselt number) and friction loss (friction factor). The artificially roughened duct had a width to height ratio (W/H) of 12, relative roughness width ratio (W/w) of 6, relative roughness pitch (P/e) of 10, relative roughness height (e/D) of 0.0433, relative gap width (g/e) of 1.0, relative gap distance (Gd/Lv) of 0.69, while the angle of attack (α) was varied from 30° to 75°. The heat transfer and friction characteristics of the duct were compared with those of a smooth duct under similar experimental conditions. It was found that there was a significant effect on the Nusselt number and friction factor when the angle of attack was changed.