CFD Based Analysis On Effect of Heat Transfer and Pressure Drop On Solar Air Heater

Abstract

- Solar air heaters (SAHs) are attractive for low-and moderate-temperature thermal applications, but conventional smooth absorber plates provide limited heat transfer because of the viscous sub-layer near the heated surface. The present work investigates the thermo-hydraulic performance of a rectangular solar air heater using V+arc and Multiple V+arc artificial roughness geometries. Three-dimensional CFD simulations were performed in ANSYS Fluent 2024 R1 using the SST k –ω turbulence model for Reynolds numbers from 3000 to 11,000 under a uniform heat flux of 1000 W/m². The computational duct has a width of 100 mm, height of 20 mm, test length of 600 mm, roughness pitch of 20 mm, roughness height of 2 mm, and aspect ratio of 5. Experimental measurements were also conducted using an aluminium absorber plate, PT-100 temperature sensors, an anemometer, pyranometer, data logger and U-tube manometer. The Multiple V+arc configuration produced the highest heat-transfer enhancement, with Nusselt number increasing from 37.67 at Re = 3000 to 108.93 at Re = 11,000, approximately 2.9 – 3.1 times the smooth-plate baseline. The friction factor increased because of flow separation and secondary vortices, with values of approximately 0.030 – 0.027 for Multiple V+arc. The maximum thermo-hydraulic performance parameter of 2.057 was obtained at Re = 7000. Smooth-plate experimental results showed close agreement with the Dittus – Boelter and Blasius correlations, and the CFD results showed good agreement with experiment. The study demonstrates that Multiple V+arc roughness can substantially improve heat transfer while maintaining a favorable overall thermo-hydraulic performance