Analysis of the thermal performance of flat plate PCM heat exchangers for heating systems

This paper presents an analysis of the thermal performance of a paraffin (RT60) used as phase change material (PCM) in heat exchangers of a heating system, the operating temperatures of the water being around 80 degrees C at the supply and 30 degrees C at the return. The developed model takes into account the results of a CFD porosity model for the PCM phase change processes, but summarizes the knowledge of this model in useful polynomial equations. These equations, coupled with one-dimension equations (1D) for the aluminium capsule and for the water, were implemented in a custom-designed program. The hybrid CFD-1D model was applied to a module consisting of a flat plate (capsule filled with 30 and 10 mm thickness of PCM) bathed by water channels. The results were successfully compared with those obtained from a full CFD model, the computational time dropping from several weeks to a few seconds. The application to PCM heat exchangers of volume 0.8 x 0.6 x 0.6 m(3) according plates arrangements (horizontal and vertical), phase change processes (melting and solidification), PCM thicknesses and operating conditions Were studied. The horizontal arrangement is faster than the vertical, the melting time being almost half in the former. (C) 2017 Elsevier Ltd. All rights reserved.