Thermofluidic Analysis Around an Isothermally Heated Rotating Sphere

Abstract

A numerical analysis is performed on mixed convection around a heated sphere immersed in air within the laminar regime. Various relevant influencing parameters, namely, Rayleigh number $\left( {10^{2} \le Ra \le 10^{6} } \right)$, Reynolds number $\left( {0 \le Re_{D} \le 300} \right)$, and diameter ratio $\left( {2 \le D^{*} \le 5} \right)$ are employed to characterize the study thoroughly. A comprehensive comparison of thermal and flow field is elucidated for both stationary and rotating sphere by employing thermal plumes. A greater radial deflection is obtained for higher $Re_{D}$ and lower Ra. A continuous growth of heat removal is observed with the rise of strength of swirling speed of sphere for a particular value of Ra and $D^{*}$. Also, a monotonic growth of heat transfer rate is also observed with rise of diameter ratio. However, Nusselt number is predicted to be lower with rise of $D^{*}$ for a fixed $Re_{D}$ and Ra. Lastly, we have also employed velocity vectors to understand the fluidic behaviour around the stationary and rotating sphere. A strong radial deviation is observed at the higher $Re_{D} = 300$ at lower Ra than higher Ra.