Computational Fluid Dynamics Analysis Of Heat Transfer And Friction Characteristics In Solar Air Heater With Staggered Inclined Discrete Rib Roughness

Abstract

This research investigates the heat transfer and friction characteristics in a rectangular duct solar air heater with
staggered inclined discrete rib roughness on the absorber plate. The study employs Computational Fluid
Dynamics (CFD) to analyze the effect of relative roughness pitch (P/e) on thermal performance. A 3D CFD model
was developed using ANSYS Fluent 14.5 with the Renormalization-group (RNG) k-ε turbulence model.
Simulations were conducted for Reynolds numbers ranging from 2000 to 16000 with relative roughness pitch
values of 8, 9, 10, and 11. Results demonstrate that the thermal performance increases with Reynolds number, and
the optimal relative roughness pitch is P/e = 10, which yields the maximum Nusselt number enhancement of 2.58
times compared to smooth ducts. The maximum enhancement in friction factor is 3.86 times at the same pitch
value. The highest thermohydraulic performance parameter of 1.99 was achieved at a Reynolds number of 12000
with P/e = 10. These findings contribute valuable insights for designing more efficient solar air heaters with
artificial roughness elements