Mechanical and thermal evaluation of different types of PCM-concrete composite panels

Using the mass of a building as a heat storage system can reduce the demand on the heating and cooling systems of the building. Concrete combines a high specific heat capacity with a thermal conductivity that is appropriate... [ view full abstract ]

Using the mass of a building as a heat storage system can reduce the demand on the heating and cooling systems of the building. Concrete combines a high specific heat capacity with a thermal conductivity that is appropriate for the diurnal heating and cooling cycle of buildings. The heat storage capacity of concrete can be enhanced by adding phase change materials which provide a high latent heat storage capacity. Research was carried out to investigate different methods of combining concrete and phase change materials to form PCM/concrete composite panels. In the first method microencapsulated paraffin was added to fresh concrete during the mixing process. In the second method butyl stearate was vacuum impregnated into lightweight aggregate which was then included in the concrete mix design. In the third method a layer of render containing microencapsulated paraffin was plastered onto the surface of a concrete panel. The primary aim of the study was to determine which method is the most effective way at improving the thermal mass characteristics of a concrete panel.
The study observed the rate at which the different panels absorbed and emitted heat, and how the heat flux varied throughout the depth of the panel. The panels were heated in a controlled environment provided by a specifically designed light box in which radiation was used as the heat transfer mechanism. Surface and internal temperatures of the panels were recorded during heating and cooling periods. The data recorded, together with the determined densities and thermal conductivities, were used to determine the influence that the method of incorporating a phase change material, had on the effectiveness of the PCM to improve the thermal mass characteristics of the concrete panel.
The study highlighted the complexity of thermal behaviour of PCM/concrete composites. The panels containing PCM displayed significantly greater thermal storage capacity despite having reduced thermal conductivity and density. The study concluded that the panel containing lightweight aggregate/PCM composite is more effective at providing additional thermal storage particularly within the first 100mm depth of an element of a structure.