An investigation of phase change problems. A: Melting of a semi-transparent medium including radiation effects. B: Transient freezing of turbulent flow inside tubes

The effects are studied of radiation on the melting rate of an absorbing, emitting, scattering, semi-transparent, homogeneous medium having a geometry in the form of a semi-infinite region, hollow cylinder and hollow sphere. The boundaries are assumed to absorb, emit and reflect radiation. The problem of phase change for the semi-infinite medium is solved by the zeroth order analysis of the generalized integram transform technique; the problems of hollow cylinder and hollow sphere are solved by the regular perturbation technique. The radiation effects are included by the application of the P sub 1 approximation of the spherical harmonics method. The transient freezing of liquids in unsteady turbulent flow inside circular tubes is investigated. The profile of the liquid-solid interface and the local transient heat flux are determined as a function of time at different locations along the tube for different values of the system parameters.