Abstract This paper discusses the numerical simulation of the thermal behavior of steady-state water flows within parallel tubes in a plane solar collector. The CFD modeling technique, which is based on the finite volume method, has been implemented with the SIMPLE algorithm. The governing equations of the flow are those of Navier-Stokes, coupled with the energy conservation equation, and solved by using the computer software FLUENT. The profiles of water temperature are analyzed for different mass flow rates. A considerable increase in the heat transfer between the absorber wall and the tubes was observed at the low velocity of water flows. The lower mass flow rate allowed a longer residence time of fluid, and the slower mass flow yielded an increased outlet temperature.

In the present study, a CFD characterization of the flow generated by curved-blade impellers in a cylindrical unbaffled vessel was carried out. The tank diameter was 300 mm, with a flat bottom. The liquid height was equal to the vessel diameter. The fluids simulated have a shear thinning behavior. Analyses concern the effect of the impeller speed, the fluid rheology and the number of impeller blades on the induced flow patterns and the power consumption. The predictions were compared with literature data and a satisfactory agreement was found.