INT. COMM. HEAT MASS TRANSFER Vol. 18, pp. 11-17, 1991 ©Pergamon Press plc 0735-1933/91 $3.00 + .00 Printed intheUnited States A PHENOMENOLOGICAL DESCRIPTION OF THE PROGRESSION OF A FREEZING FRONT IN A SIAB. APPLICATION TO A NEW HEAT STORAGE MATERIAL. ABSTRACT G. GUIFFANT, P. FLAUD, L. ROYON LBHP CNRS URA 343 - Universit~ PARIS VII 2, Place Jussleu 75251 PARIS Cedex 05 (Communicated by J. Oosse) The restatement of a new material for the heat storage gave the opportunity to develop a phenomenological model, based on a heat balance approach, for the description of the progression of a freezing front in a slab. The method applies when the sample is submitted to initial and final temperatures different from the transition temperature. The theoretical results are in very good agreement with the experimental data. INTRODUCTION The aim of this note is to present some results obtained by using a phenomenologlcal model for the description of the progression of a freezing front in a slab of a material undergoing a phase change without an impor- tant modification of state. Practical problems involving a phase change are important in many in- dustrial processes. In particular the recovery of low level energy can be achieved, in some circumstances, by using heat pumps associated with a "cold stock". Such a stock needs to have the greatest possible value for the heat capacity and must ensure both a great thermal capacity and a great exchange area with the recovery fluid. The problem beelng set in this way could appear as simple but technical difficulties arise that affect stron- gly the efficiency of the process. A first promising type of solution is to emulsify the changing phase material in the recovery fluid ; in that case, instabilities can occur which lead to clotting and coalescence. A second type of solution makes use of fixed beds. In that case, the material is to be coated because of the solid-liquid transition. Then it is not possible to divide the material into sufficiently small pieces and the envelop acts as a supplementary heat resistance reducing the efficiency of the device (moreover, the coating is an important overcost for the device). II