Heat Transfer and Fluid Dynamics Study in Solar Air Heater Employing Impinging Circular Air Jet Array for Effective Jet Stability

This experimental and numerical investigation is intended to increase heat transfer, reduce pumping power, and present important guidelines on the use of confined submerged air jet impingement in solar air heater designs that employ an array of circular air jets for high thermohydraulic performance. In order to increase thermohydraulic performance, a novel approach is adopted, i.e., by improving jet stability and consequently jet deflection that gives origination to four solar air heater designs for this investigation. The obtained numerical results revealed that thermohydraulic performance improves significantly by stabilizing the air jet array, which means lowering the jet deflection. The thermohydraulic performance of design-I is high compared to design-II, design-III, and design-IV, both at equal mass flow rate and Reynolds number. Moreover, design-I presents 20%, 33%, and 52% relative improvement in deviation angle of the jet core compared to design-II, design-III, and design-IV, respectively, at a minimum mass flow rate of 0.01 kg/s and Reynolds number of $Re=2000,$ respectively. In addition, correlations to define heat transfer and fluid dynamics characteristics are established. An important guideline upon the use of solar air heater with jet impingement is that a solar air heater of short length and height (jet and plate spacing), and large width should be used for high thermohydraulic performance.