Energy and exergy analysis of a solar-thermal air collector design utilizing a novel jet impingement technique: an experimental study

Jet impingement technology for solar-thermal applications has gained much recognition during recent years due to its enhanced heat transfer and flow characteristics. However, for improving and for getting reliable estimate of its performance for practical implication of this design, jet impingement technique needs to be innovated and its comprehensive energy and exergy performance need to be underscored in the open sun. The present study investigates the energy and exergy performance of a solar-thermal air collector (STAC) utilizing a novel tapered-nozzle-array air-jet impinging arrangement under open sun tropical conditions. A detailed experimental investigation is conducted on the STAC design. Its performance is analysed in terms of temperature-rise parameter, thermal efficiency, and exergy efficiency, considering variations in solar radiation, ambient air temperature, and air flow rate. The results show significant improvements in overall heat transfer characteristics with higher solar radiation intensity and air flow rate. The maximum thermal efficiency of 81.48% and exergy efficiency of 23.63% are achieved at peak solar radiation intensity. The study identifies the absorption of solar radiation by the absorber surface as the major contributor to exergy destruction, accounting for 47-64% of the total losses. Also, non-dimensional parameters such as Nusselt number with a maximum value of 191.71, and thermal enhancement factor, with a maximum value of 3.04, clearly demonstrate enhanced performance compared to conventional smooth duct arrangements. Comparison of the performance results with existing literature suggests that the present design may be considered prolific for overall performance enhancement in STAC designs.