PARAMETRIC CFD STUDY OF SOLAR AIR HEATER HAVING ALTERNATED UPPER AND BOTTOM ABSORBER PLATES IN TURBULENT FLOW

Abstract

This work presents a computational fluid dynamics (CFD) investigation of a solar air heater (SAH) that features alternating upper and bottom absorber plates to evaluate its thermal behavior and turbulent flow characteristics. Generally, the SAH exhibits low heat transfer characteristics and poor thermal efficiency in turbulent flow. The use of alternating upper and bottom absorber plates facing the turbulent flow would improve heat transfer by producing recirculation zones mainly over these heated plates. The computational fluid dynamics software program, ANSYS Fluent 15.0, along with the renormalization-group (RNG) <i>k-ε</i> turbulence model, was utilized in this analysis to solve the transport equations for turbulent kinetic energy and dissipation rate. The analysis encompassed several geometric and operating parameters, including the relative absorber plate length <i>L<sub>p</sub>/h</i> ranging from 4.375 to 140, the relative absorber plate height <i>h/H</i> ranging from 0.03 to 0.12, and the Reynolds number varying between 3800 and 18,000. The impact of these parameters on heat transfer improvement factors, including the heat transfer amelioration ratio (HTAR), friction loss amelioration ratio (FLAR), and thermohydraulic efficiency factor (THEF), was studied. The optimum computed THEF value was found to be 2.18 for <i>L<sub>p</sub>/h</i> = 4.375, <i>h/H</i> = 0.12, and Re = 3800.