Numerical Investigation of Thermal - Hydraulic Performance of a Solar Air Heater Duct with Transverse W-Shaped Rib Turbulators

Abstract

One of the effective methods that can be employed to enhance the performance of the solar thermal air heater is texturing of the absorber surface using the rib roughness. The alteration facilitates the heat transfer by the generation of turbulence and surface area increases. To analyze the thermal performance of an optimized surface roughness solar-powered air heater, the article provides a 2D numerical model of an air heater. A solar air heater (SAH) duct with W-shaped transverse ribs on an absorber plate made of two opposing right-triangular ribs are studied in this current work concerning the thermo-fluid behavior. Notable results are the Nusselt number (Nu), the friction factor (f ), the thermo-hydraulic performance parameter (THPP) and distributions of fluid properties. In the computational analysis, various roughness and flow conditions are investigated, i.e. the Reynolds number (Re =6,000-18,000), non-dimensional pitch (P/e =7.14-17.86) with non-dimensional height (e/D =0.042) remaining constant. The optimum value of THPP was achieved with the suggested rib arrangement at P/e=10.71 and Re=6000. The ribbed surface has significant improvements in thermal performance, where the values of Nu have improved by 228% of smooth ducts. However, this enhancement is coupled with increased hydraulic resistance especially in the region of P/e=7.14 and Re=18,000 where the friction factor rises to 4.18 times the amount of smooth ducts.