An Experimental and Computational Investigation on Fluid Flow and Thermal Performance of a Rhombus Passage Solar Air Heater of Various Configurations

The experimental and numerical findings of fluid flow and thermal characteristics of rhombus passage solar air heater (SAH) over Reynolds number range 5000-28000 are reported in this article. In this comprehensive investigation, seven models of rhombus-ducts are obtained by modifying the sharp corners with arc-shaped corners. The models include: No curvature at duct corners; Curvature at top corner; bottom corner; left or right corner; both left and right corners; both top and bottom corners; all four corners. Out of these seven models, the best one is chosen, and is further investigated by including the roughness elements, such as dimples, rectangular ribs on the absorber plate of SAH. In these models with roughness elements (Model-8 and Model-9), the roughness parameters are varied, and further investigations are carried out. Three-dimensional computational simulations are performed by using the ANSYS Fluent. Also, experiments are conducted with a few SAH duct variants to validate the numerical results. To gain confidence in the results obtained, validation is done against the standard correlation and literature data. The influence of operating parameters on Nusselt number, friction factor, and air temperature at duct outlet is investigated. It is found that the model with all arc-shaped corners is the best out of Model-1 to Model-7. In addition, the rhombus duct Model-9 (with all corners possessing arcs and rectangular ribs of height 5 mm on the absorber plate, Pl/e = 10) is the greatest choice, showing an enrichment in bulk temperature of 127.5% compared to simple rhombus duct SAH.