Thermal characteristics of a direct heat exchange system between granules with phase change material and air

The authors have proposed a system of direct heat exchange between granules including phase change material (PCM) and air. The PCM granules consist of granulated porous media with particle diameters of about 1-3 mm and paraffin wax. At first, column experiments are performed with a packed bed of PCM granules. Temperature variations in the PCM packed bed are measured. It is demonstrated that heat exchange flux between the PCM granules and air can be kept large and continuous during phase change. Secondly, a computer simulation model is made using an assumption that the temperature of the PCM granules is the same as that of passing air throughout the packed bed. It is found the phase change period calculated by the model is in agreement with the measured one. Finally, heat transfer coefficient during phase change and the time required for phase change to be completed in the system are discussed by a numerical analysis. (C) 2004 Elsevier Ltd. All rights reserved.