Predictive Correlation for Optimum Phase Change Material Thermal Energy Storage

Abstract Organic phase change material and high thermal conductivity filler composites are effective in thermal energy storage, but their performance can be highly dependent on the volume fraction of the phase change material/filler. In these composites, energy density (energy storage capacity of the composite) can be enhanced by increasing the phase change material volume fraction; in contrast, power density (rate at which the energy is accessed) can be improved by increasing the filler volume fraction. However, both of these characteristics cannot be increased simultaneously; therefore, the optimal volume fraction is crucial for maximizing the composite's thermal performance, i.e., achieving the optimal balance of energy and power density in the composite thermal buffer. This paper proposes a relationship for the optimal phase change material volume fraction as a function of operating boundary conditions, geometric configuration, and cutoff temperature during the melting process. The proposed correlation provides a practical tool for designing and optimizing organic phase change material - filler composites for certain thermal applications, thereby reducing reliance on computationally intensive simulations or experimental trials.