Numerical investigation on combined natural convection and radiation heat losses in one side open cylindrical cavity with constant heat flux

In the case of considering conduction heat loss through the insulation, a 3D numerical investigation of the combined natural convection and radiation heat losses in one side open cylindrical cavity with constant heat flux has been carried out. Numerical procedure is validated by our latest experimental measurements. Visualization results, i.e., temperature and velocity contours, velocity vector field are provided. The effects of tilt angle, aperture ratio, heat flux as well as surface emissivity on the convection heat loss Nusselt number and radiation heat loss Nusselt number have been quantitatively analyzed. Results show that natural convection heat loss Nusselt number is more sensitive to tilt angle and aperture size, except when the tilt angle is 90° (the opening facing vertically downward), at this point no matter how other parameters change, natural convection heat loss Nusselt number always fluctuates in a small value. While radiation heat loss Nusselt number increases with the increase of all the impact parameters to some extent. The radiation heat transfer weakens the natural convection in the cavity. When the total heat flux is constant, the percentages of three modes of heat losses show different variations with related parameters. In addition, separate empirical Nusselt number correlations for natural convection heat loss and radiation heat loss based on a large set of numerical data for a given range of parameters of practical interest have been proposed.