Experimental analysis for augmentation of heat transfer in multiple discrete V-patterns combined with staggered ribs solar air heater

An experimental study has been carried out for enhancement of heat transfer, friction factor and thermo-hydraulic performance of a solar air heater artificially roughened in the form of multiple discrete V-patterns combined with staggered rib roughness as turbulence promoter. The range of parameters for this study has been decided from practical considerations of the system and operating conditions. Geometrical parameters of roughness are the value of relative roughness pitch (P/e) 12, value of relative roughness height (e/Dh) 0.045, value of angle of attack of flow (α) 60°, value of relative staggered rib position (p′/P) 0.65, value of relative gap width (g/e) 1, value of relative staggered rib length (w/e) 2-5.5 and value of number of gaps on each side of V-rib (Ng) 4. The air flow rate corresponds to Reynolds number of 3000-12 000. The Nusselt number and friction factor are maximum for relative staggered rib length of 3.5 and 2 respectively. Maximum enhancement in Nusselt number and friction factor is 2.27 and 4.28 times that of smooth duct respectively. Also correlations are developed for heat transfer and friction factor.