Numerical Simulation of the Effects of Surface Roughness on Nucleation Site Density of Nanofluid Boiling

In this research, a numerical scheme for subcooled flow boiling with water based fluid in a channel with a hot spot was developed. The effect of nanoparticles was studied in the subcooled flow boiling. Alumina nanoparticles were used for the protection of nanofluid. The properties of nanofluid are assumed to be temperature independent. The mixture of nanofluid is studied by using Eluer–Eluer approach. In addition to considering the variable properties of temperature in this study, a model for the density of the nucleation site was used, which is the surface roughness and sedimentation rate of the nanoparticles. After verifying the model, the nanofluid boiling was modeled, using 4 roughnesses of 25, 50, 75, and 100 nm. Changes of bubble dynamics parameters were investigated in different heat fluxes and roughnesses. According to the results, it was found that with increasing surface roughness, the surface temperature drop and the density of the nucleation site density increased. Also, bubble departure diameter is increased and bubble detachment frequency is decreased by increasing surface roughness. Moreover, the results shows that bubble detachment diameter is increased by increasing the heat flux and bubble detachment waiting time.