Numerical Investigation of Flow and Heat Transfer From a Rotating Sphere With Constant Angular Velocity Around Vertical Axis Floating in Stationary Fluid

Convective heat transfer for a rotating sphere around a vertical axis floating in stationary fluid is studied numerically using the model of volume of fluid (VOF). The effects of the immersion angle and rotating velocity on the streamlines, isotherm and volume fraction contours, mean and local Nusselt numbers, volumetric flow rate, and water film thickness are investigated for the angular rotational velocity, 1500 <= Omega <= 3500 and the immersion angle, 30 deg <= theta(i) <= 60 deg. The results show that the sphere's rotation causes the liquid to be sucked from the lower pole of the sphere, which is thrown out after stopping in the equator. Due to the strong jet flow in the equatorial zone, heat is transferred by forced convection, but diffusion is dominant for heat transfer in other zones. At low rotational velocities, the liquid film is thrown out of the equator in the form of large droplets, but as the rotational velocity increases, its shape changes to a jet. Also, it is found that there is a direct relation between the Reynolds number and mean Nusselt number at different immersion angles so that an average of 27.5 % increase for the mean Nusselt number is achieved by increasing the immersion angle from theta(i) = 30 deg to theta(i) = 60 deg. In addition, at a constant rotational velocity, the volumetric flow rate increases with increasing immersion angle.

Automated summary

The study found that the rotation of the sphere causes liquid to be sucked in from the lower pole and thrown out at the equator, with forced convection heat transfer occurring in the equatorial zone and diffusion dominating in other areas. As rotational velocity increases, the shape of the liquid film changes from droplets to a jet. There is a direct relationship between Reynolds number and mean Nusselt number at different immersion angles, with an average increase of 27.5% achieved by increasing the immersion angle from theta(i) = 30 deg to theta(i) = 60 deg. Additionally, at a constant rotational velocity, the volumetric flow rate increases with increasing immersion angle.