This paper presents the results of a numerical study validated by experimental measurements on the solidification of PCM along a horizontal tube by using the boundary immobilization technique. The two dimensional model (r,z) of the phase change problem is formulated based on the energy equation and the Landau transform which transforms the moving irregular interfaces to fixed parallel interfaces. The finite volume method is used to discretize the system of equations and the associated boundary and initial conditions. A computer program was elaborated and the time and space grids were optimized to make the numerical solution insensitive to the grid size. The model was validated against experimental and numerical results available in the literature and good agreement was found. Additional results were obtained and the numerical predictions were found to agree well with the new measurements showing that the immobilization technique is adequate to handle phase change problems. (c) 2013 Elsevier Masson SAS. All rights reserved.75184193