CFD Analysis of the Thermal-Hydraulic Performance in a Fin Channel of a Solar Air Heater with Various Block Shapes

A solar air heater generates heated air using solar energy. This system has a relatively simple design, which reduces the initial cost and facilitates maintenance compared with other solar systems. However, its thermal conversion efficiency is limited by the poor thermal conductivity of air. Previous studies have improved thermal efficiency by enhancing either the heat transfer area or the heat transfer coefficient, but most have applied only one of these approaches. In this work, a novel solar air heater with longitudinal fins and blocks, designed to simultaneously enhance the heat transfer area and heat transfer coefficient, is investigated for various block shapes (rectangular, forward-chamfered, backward-chamfered, and triangular blocks) utilizing computational fluid dynamics. Compared to the smooth fin channel, heat transfer is enhanced by a maximum of 1.61 times with the backward-chamfered block, while the corresponding enhancement factors for the rectangular, forward-chamfered, and triangular blocks are 1.52, 1.46, and 1.54, respectively. The thermo-hydraulic performance parameter, which simultaneously evaluates heat transfer augmentation and frictional penalty, further indicates that the backward-chamfered block is most effective at Reynolds numbers below 6000, while the rectangular block performs best above 9000.