Effective efficiency assessment of a solar air heater having baffles spaced with different successive ratios

Abstract

The baffle in the air collector duct increases heat transfer, while also significantly increasing the pressure loss penalty. Pressure loss reduction can be achieved using the unequal baffle pitch which is proposed in this study. In the current paper, a numerical investigation of an air collector duct with inclined baffles is presented. Inclined baffles spaced with successive ratio (r) from 1 to 1.4 and Reynolds number (Re) of air from 2370 to 13250 were varied to evaluate Nusselt number, friction factor and effective efficiency of the collector. 2D numerical simulations with the standard k-ε turbulence model were performed to clarify the flow mechanism through baffles. The results show that pressure loss in case of r > 1 significantly reduces compared to that of r = 1. Therefore, the maximum effective efficiency of the baffled collector duct with successive ratios from 1 to 1.3 is the same and equals to 0.6. It is better to install dense baffles near the inlet than dense baffles near the outlet because many baffles concentrated on the inlet create high turbulence in the rest of the air collector duct.