The critical heat transfer characteristics of an insulated or compound sphere considering heat radiation

Critical heat transfer from an insulated or compound sphere happen in ambient air with natural convection. Thus, heat radiation in such a situation must be considered because natural convection has only a small effect. It is found that the critical heat transfer characteristics considering heat radiation are very different from those neglecting heat radiation. The conventional critical heat transfer characteristics neglecting heat radiation only depend on sphere size, external convection heat transfer coefficient, and insulation conductivity. In addition to the above parameters, the critical heat transfer characteristics considering heat radiation are also related to the surface emissivities of the sphere and the insulation, the surrounding temperature, and the internal convection heat transfer coefficient.