IMPROVEMENT ON THE MODELING OF FILM BOILING ON SPHERES

An analytical model for stable film boiling heat transfer from a spher e is derived following the classical approach of Frederking and Clark but using spherical coordinates instead. The improvement shows more cl early than the previous work that the Nusselt number should approach t he value of 2 instead of zero, as the Rayleigh number goes to zero. Fu rthermore, by consideration of two limits on the liquid-vapor interfac e boundary conditions based on Bromley's suggestion, the coefficient C -1 is shown to lie in the range 0.586 to 0.828, in the correlation Nu= C-1[Ra/Ja](1/4)+2. This supports the value of 0.67 as proposed by Dhir and Lienhard. (C) 1997 Elsevier Science Ltd.