Numerical studies on the effect of delta-shaped obstacles' spacing on the heat transfer and pressure drop in v-corrugated channel of solar air heater

From numerical studies in a v-corrugated duct, it is found that backflow between obstacles and high velocity in the gap between obstacles and absorber plate causes the flow became more turbulent and enhanced the convection heat transfer between the air and the absorber plate. Obstacles placed in a small spacing will increase Nusselt number (convection heat transfer) and friction factor (pressure drop). The Nusselt number enhanced from 27.2 when no obstacle used to 94.2 when obstacles inserted with S/H = 0.5. The Nusselt enhanced 3.46 times. The friction factor will increase from 0.0316 at no obstacle to 0.628 at ratio S/H = 0.5. The friction factor increased 19.9 times. Efficiency, Nusselt number, and friction factor are decreasing as ratio S/H is increasing. When ratio S/H used is 1 instead of 0.5, Nusselt number enhancement decreased only 1.13%, but friction factor decreased 15.1%. So, sacrificing a small amount of Nusselt number but reducing a significant friction factor is advantageous. The optimal spacing ratio S/H of delta-shaped obstacles inserted in a v-corrugated SAH is one. In other words, the optimal spacing of obstacle equals to its height.