Numerical analysis of combined free convection and radiation heat transfer from an open hemispherical cavity

Abstract

The present work aims to numerical study the combined effect of free convection and surface radiation from an open hemispherical cavity and the estimation of cooling time using ANSYS-Fluent 15.0. This study warrants a significant novelty. Various parameters, such as Rayleigh numbers (in the range of $1.5\times {10}^3$ to $1.5\times {10}^7$), surface temperatures, and the radius of curvatures varied to elucidate the effect of these parameters on the heat transfer characteristics considering surface radiation. The temperature contours and velocity vectors are obtained pictorially to understand the thermo-fluid characteristics around the hemispherical surface better. For all cases, the radiative heat transfer rate is found to be higher than the convective heat transfer rate for a given condition. The estimation of cooling time is done using lumped system analysis, taking both convection and radiation into account. It is observed that the cooling time estimated with radiation is much lower than that without radiation (only convection). This signifies that the radiation effect should be considered for similar problems. Finally, for the open hemispherical cavity, a correlation for the Nusselt number is developed by incorporating the regression analysis of the available data.

Keywords:

• Cooling time
• emissivity
• hemispherical surface
• Rayleigh number
• surface radiation

Disclosure statement

The authors declared that there is no conflict of interest.

Data availability

Data will be made available on request.