Effects of curvature existence, adding of nanoparticles and changing the circular minichannel shape on behavior of two-phase laminar mixed convection of Ag/water nanofluid

Abstract

In the present research, heat transfer behavior and Ag/water two-phase laminar nanofluid flow as cooling fluid in volume fraction of nanoparticles 0–6 % and Reynolds numbers of 200–500 in a tube with curvature angle of 270° are simulated utilizing finite volume method. 3-D simulations of laminar mixed convection two-phase nanofluid flow considering Grashof numbers of 5,000, 50,000 and 100,000 are carried out numerically. The results of the present research indicate that adding solid nanoparticles causes periodic behavior with particular repeat length on the axial velocity profile and maximum and minimum values shift every 60°. Also, after the curvature angle of 30° because of fluid motion, centrifugal forces importance, fluid rotation, and hydrodynamic field, local friction factor increases considerably up to channel outlet. In all diagrams, the maximum friction factor is related to the Grashof number of 100,000, this value will have more significant augmentation by the increase of volume fraction. Due to better fluid mixing and increase of temperature line slop at Reynolds number of 500, heat transfer enhances at the regions of the bottom bend of the channel. Higher volume fractions of nanoparticles reinforce the heat transfer mechanism and heat absorption from the hot surface. In the regions where fluid is influenced by thermal boundary layer growth, entropy generation is augmented. This entropy generation is due to heat transfer. On the other hand, entropy generation is reduced in the regions where the effect of inlet fluid temperature is dominated.

Keywords

• Tube
• Mixed heat transfer
• Numerical study
• Nanofluid
• Entropy