Numerical investigation of fluid flow and heat characteristics of a roughened solar air heater with novel V-shaped ribs

Solar air heaters convert clean solar energy into useable heat and thus have a wide range of applications. Computational fluid dynamics (CFD) can aid in the design and development of solar air heaters with optimized thermal efficiency. A detailed numerical study was conducted to investigate the fluid flow and heat transfer characteristics of a roughened solar air heater with novel V-shaped ribs having staggered elements. Three-dimensional steady-state numerical simulations were performed using the k- epsilon Re-Normalisation Group (RNG) turbulence model, and results were found to be in excellent agreement with experimental data. The effect of rib spacing was studied through varying the rib pitch to rib height ratio P:e = 6-14, for Reynolds numbers (Re) in the range of 4000-14 000. A significant enhancement in the rib-roughened solar air heater's thermal performance was observed. It was also established that an increment in P:e from 6 to 10 increases the Nusselt number (Nu) for all Re values investigated. About 72.6% Nu enhancement was predicted for P:e = 10 at Re = 12 000. It was further observed that an increment in P:e from 10 to 14 decreases the Nu for all values of Re considered.