Experimental investigation of heat transfer augmentation due to obstacles mounted in solar air heater duct

In this paper, six different shape obstacles, namely, Isosceles trapezoid (Type 1), Triangular with curve apex (Type 2), Rectangular with chamfered edges (Type 3), Rectangular with curve edges (Type 4), Triangular with curve corner at bottom (Type 5) and Triangular shape (Type 6) have been tested in inline and staggered fashions in solar air heater (SAH) duct. This work aims to investigate the effect of obstacle shape on heat transfer and friction characteristics. All experiments have been carried out at eight different values of Reynolds number ranging from 2000 to 16000 and fixed value of heat flux of 1000 W/m². As results, Nusselt number and friction factor characteristics have been presented and discussed. The maximum enhancement in Nusselt number and friction factor are observed in case isosceles trapezoid obstacles (Type 1) and rectangular with curve edges obstacles (Type 4) when mounted in staggered fashion, respectively and their respective average enhancement factor in Nusselt number and friction factor are observed as 2.95 and 4.37. Also, thermo-hydraulic performance parameter (η) of all obstacles in both arrangement have been evaluated and found to be average maximum values 1.88 in case of isosceles trapezoid obstacles (Type 1) in staggered manner.