Hybrid numerical evaluation of thermo-hydraulic and exergetic behaviour in solar air heaters with advanced arc rib architectures
摘要
Enhancing the heat transfer efficiency of solar air heaters (SAHs) remains a critical challenge in renewable energy applications due to the inherently poor convective characteristics of air. Improving the absorber plate design through optimized roughness geometry is therefore essential for achieving higher energy conversion efficiency. Despite numerous studies on conventional rib geometries, limited attention has been paid to the comparative thermo-hydraulic behaviour of fixed and variable arc rib configurations under identical boundary conditions. This study numerically investigates the thermal and fluid flow performance of SAHs equipped with three arc rib geometries: Fixed Arc Rib (FAR), Fixed Arc Rib with Diameter variation (FARD), and Variable Arc Rib (VAR) over two duct lengths (1 m and 2 m). Simulations were performed using the RNG k–ε turbulence model under a uniform heat flux of 1000 W m−2 and Reynolds numbers ranging from 3000 to 21000. The results reveal that the VAR(1 m) configuration achieves the highest thermal efficiency (93.2%) and exergy efficiency (2.65), while FARD(1 m) exhibits the best thermo-hydraulic performance parameter (THPP ≈ 6.1). Velocity contour analysis further confirms enhanced mixing and turbulence intensity for variable rib geometries. The findings offer practical design guidance for developing compact and energy-efficient solar air heaters suitable for sustainable heat recovery systems.