High power density thermal energy storage using additively manufactured heat exchangers and phase change material

Thermal energy storage using phase change materials (PCMs) is an effective way to store thermal energy. PCMs store thermal energy in the form of latent heat, a promising thermal management methodology for intermittent heat loads. Because the thermal conductivity of many PCMs is relatively low (~0.1 W/(m⋅K)), high-power thermal storage is possible only when the PCM is integrated with a high thermal conductivity matrix. Enabled by recent advances in metal additive manufacturing (AM), we develop an ultra-compact high-power PCM heat exchanger and demonstrate its performance. The thermal storage device absorbs heat from, or rejects heat to, a flowing liquid coolant. Numerical simulations of heat transfer and phase change within the PCM were used to predict the device performance and evaluate potential designs. AM enabled three-dimensional (3D) metal structures were designed to serve as a matrix that conducts heat into the PCM or as extended surfaces that enhance convection to the liquid coolant. The 3D metal structures reduce conduction thermal resistance by 17X and convection thermal resistance by 3X compared to conventional designs. We fabricated three devices made of an aluminum silicon alloy (AlSi10Mg) and tested these devices with paraffin (C_nH_2n+2) PCM. Measurements validated the simulations and showed a 4X improvement in power density (0.58 W/cm³) compared to conventional designs. This work demonstrates AM as a powerful technique for the development of PCM-based thermal storage systems and suggests design methods that aid the development of heat exchangers.