Thermohydraulic performance of solar air heater with staggered multiple V-shaped ribs on the absorber plate

Fluid flow and heat transfer in a solar air heater roughened with staggered multiple V-shaped ribs on the absorber plate were investigated numerically. Three dimensional simulations were performed for different rib geometries with varying stagger distance; rib height, pitch, and attack angle; and Reynolds number. Staggered multiple V-shaped ribs provide better heat transfer than the corresponding inline arrangement, with maximum enhancement 26% and 18% for average Nusselt number and thermohydraulic performance factor, respectively. Streamwise primary vortex with inter-rib subsidiary vortex is still the basic flow structure for the staggered ribs, similar to the inline case. The gap flow induces two competing effects on heat transfer, enhancing heat transfer efficiency maximally at the optimum stagger distance. Maximum thermohydraulic performance factor for the staggered ribs was 2.43 in the range of parameters studied.