Towards Time-Scale Matched Composites: System-Level Modeling of Organic and Metallic Phase-Change Material Composites Using a Two-Temperature Model

This work presents a two-temperature model (TTM) designed to understand the thermal response of time-scale matched, phase-change PureTemp29-gallium composites. Since explicit, subscale thermal modeling of the aforementioned composites is computationally expensive, a system-level alternative capable of accurately capturing the full range of dynamic responses of PureTemp29 and gallium - the TTM - is discussed. In the TTM, each element is designed to simultaneously track temperatures of gallium and PureTemp29. The derived parameters - K, the coupling coefficient which depends on subscale composite structure and material, and k_eff, the effective thermal conductivity - are tuned using a fitting algorithm, resulting in the convergence of the TTM's thermal response to that of the explicit model. The derived parameters are found to be boundary-condition independent, i.e., varying the heat-flux has negligible impact on K and k_eff. From large-scale parametric sweeps and stepwise regression, two empirical correlations between the derived parameters and four subscale material parameters are developed. These correlations will be refined to develop a full material model for time-scale matched phase-change composites.