Heat transfer augmentation in solar thermal collectors using impinging air jets: A comprehensive review

Jet impingement has led to considerable augmentation in heat transfer characteristics of solar thermal collectors. The impinging air jets are characterized by different control factors where it becomes essential to study their dependence on performance defining criteria so as to arrive at the optimized impinging jet geometry which create one or combination of following conditions favorable for heat transfer with minimal friction losses inside the collector: (a) breaking laminar sub layer (b) increasing turbulent intensity (c) increasing heat transfer area, and (d) generating vortex or secondary flows. The present article examines the thermodynamic behavior of solar thermal collector, review the experimental investigations reported in the literature to study the dependence of control factors on heat transfer and friction characteristics and review the multi criteria decision making methods towards optimization of control factor combinations for an optimal design of the impinging jet solar thermal collector. This study provides a platform for scientists working in the same research field to design a better heat transfer enhancement contrivance in the form of jet control factors to improve the thermohydraulic performance by maximizing the energy output from the system.