Design of Radially Variant Phase‐Change Material Composites. Issue 2 (25th September 2022) - Hoe, Alison
Abstract : Phase‐change materials (PCMs) and high‐conductivity elements can be combined to form highly compact and efficient composite heat sinks. However, the design challenge presented by thermal composites composed of PCMs and high‐conductivity elements remains unresolved. Herein, design guidelines are presented for radially varying cylindrical PCM composites. Numerical and analytical techniques are utilized to explore the utility and limits of optimal composite designs selecting for 1) temperature minimization, 2) specific effective heat capacity maximization, and 3) volumetric effective heat capacity maximization. Significant increases in each metric are observed when implementing radially variant designs in cylindrical geometries, especially for metrics of heat capacity. Furthermore, a hybrid approach to variant composite design is presented, allowing for the balancing of different design objectives. The utilization of a variable design under high heat flux (10 ± 1.4 W cm −2 ) and short melting periods (up to 50 s) is experimentally demonstrated, directly resulted in a 65% decrease in total system mass and a 200% increase in specific heat capacity while maintaining strong temperature dampening performance. In a second case study, a 23% decrease in mass is demonstrated while maintaining strong specific heat performance, emphasizing the broad utility of this approach. Abstract : Optimization of cylindrical phase‐change material composites with radially varying composition is completed analytically and the utility of this approach is demonstrated across the design space. Numerical simulations and machine learning techniques are used to verify the approach and resulting composition profiles. A hybrid design approach is also described and experimentally verified, allowing for the balancing of competing design objectives.