Heat Transfer Enhancement in Solar Air Heaters Using Porous Ribs

Solar air heaters (SAHs) suffer from inherently low thermal efficiency due to poor convective heat transfer between the absorber plate and airflow. This study numerically investigates a novel passive enhancement technique: integrating periodically placed porous ribs on the absorber plate. A comprehensive computational fluid dynamics (CFD) analysis was conducted using ANSYS Fluent to model turbulent flow (Reynolds number range: 3000 ? Re ? 12000) and heat transfer within a rectangular SAH duct. The finite volume method (FVM) solved the governing equations, employing the validated RNG k-? turbulence model and the Darcy-Brinkman-Forchheimer model for the porous rib regions. The primary objectives were to quantify the impact of porous ribs on heat transfer and fluid flow characteristics compared to both smooth ducts and conventional solid ribs, and to optimize key geometric parameters: relative rib height (e/D), relative rib pitch (P/e), and rib porosity. Results demonstrate that porous ribs significantly enhance thermal performance.

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