Multi-scale composite models for the effective thermal conductivity of PCM-concrete

Encapsulated phase change materials (PCMs) were used in concrete to improve thermal properties of the concrete, called PCM-concrete. This paper presents the predictions of the effective thermal conductivity of PCM-concrete using different composite models, such as the parallel, the series models, Maxwell model and Generalized Self-Consistent (GSC) model. Multi-phase, multi-scale internal structural models were developed and combined with GSC model to predict the effective thermal conductivity of PCM-concrete. It was found that the configuration of the internal structure for the PCM phase is very important. The PCM phase needs to be considered as a matrix (a thin shell), which can effectively block the heat flow and thus reduce the thermal conductivity of PCM-concrete. The GSC model with the suggested internal structure model can predict the effective thermal conductivity of PCM-concrete. The prediction agreed with test data quite well, and the prediction is within the upper and lower bounds.