CFD based Analysis of a Solar Air Heater having Isosceles Right Triangle Rib Roughness on the Absorber Plate

Abstract

In the present work the study of heat transfer and friction characteristics in rectangular duct of a solar air heater having isosceles right triangle rib shape on the absorber plate by using CFD (Computational Fluid Dynamics) The roughness has been placed in such way that the hypotenuse faces against the flow direction. The design parameters chosen for study are Reynolds number, roughness height and roughness pitch. The turbulence model used in CFD solutions is Renormalization group (RNG) k-ε. The roughness height (e) is chosen as 0.5mm, 1.0mm and 1.5mm at roughness pitch (P) of 5mm, 10mm, 15mm and 20mm. The relative roughness Pitch (P/e=3.33-40) and relative roughness height (e/D= 0.015-0.045) is taken. The effect of transverse wedge shape on heat transfer and friction factor was investigate covering the range of roughness parameter having Reynolds no varies from 3000 to 18000. ANSYS FLUENT is used to simulate turbulent airflow in artificial roughened solar air heater. Five different turbulence models is tested on the quality of obtained results .The RNG k-ɛ model yield better result for two dimensional flow through conventional solar air heaters. Thermo-hydraulic performance is also calculated. Correlations for the Nusselt number and friction factor have been developed.