A numerical model is presented for the solution of the solidification problem of a phase-change material (PCM) in the annular region around a convectively cooled cylinder. An existing formulation, using the interface immobilization technique and the finite volume method, is applied and extended for the phase-change problem coupled with heat transfer in the tube wad and fluid. The predicted values are compared with available numerical and experimental results with good agreement. Some aspects of the model are discussed such as the discretization schemes for the pseudoconvective terms that arise from the formulation and the evaluation of Nusselt number in the fluid.36195114