Investigation of heat transfer enhancement in impinging jet-dimpled-protruded solar air heaters

Solar energy is a source of renewable energy and is considered a clean, convenient,sustainable, safe, abundant, and economical source. Solar Air Heaters (SAHs) are oneof the applications of solar energy. SAH has a wide variety of applications but has lowthermal efficiency. This low thermal efficiency is due to the low thermal capacity ofthe air, and the poor process of heat transfer between the absorbing plate channel andair.With the aim to improve thermal efficiencies, the novel dimple/protrusion surfaceshave been incorporated onto the 307 × 212 mm aluminum absorbing plate. A 3 × 3array of 5 mm impinging jets is used to further decrease the temperature of the plate.A set of five different plate configurations, i.e., smooth, dimpled, dimpled-protruded,protruded-dimpled, and protruded configurations are simulated by using the experimentallyvalidated Computational Fluid Dynamics (CFD) model. The values of heattransfer enhancement, pressure drop, and Thermal Performance Factor were evaluatedfrom the CFD study. The protruded plate is selected as the best plate configuration,based on the Thermal Performance Factor. An overall improvement of 33.5% is observedin the current research work, as compared to the smooth configuration. Hencepromising is the augmentation.