Radiative transfer in a sodium mist layer

The authors discuss calculation of natural convection heat transfer through the cover gas space by utilizing known heat transfer correlations on natural convection. Under reactor operating conditions, both the mass flux of sodium vapour and the mass fraction of sodium mist are small and the properties of the cover gas medium are treated as those of the inert gas. However, evaluation of radiative heat transfer through the cover gas space is difficult because knowledge of the radiative properties of sodium mist and time-consuming computations of the equation of transfer are required. There is little information about the radiative heat transfer through the cover gas space containing sodium mist. The present study aims at evaluating the total radiative heat flux at the cold boundary surface of the cover gas space containing sodium mist by exactly solving the spectral equation of transfer and examining the validities of some approximations, including the diffusion approximation to radiative heat flux. Throughout the present analyses the radiative properties of sodium mist required are evaluated rigorously by taking into account the dependence of the particle size distributions of sodium mist on temperature and the dependence of the complex refractive index of liquid sodium on both temperature and wavelength