Bioinspired hybrid tube-metal foam architectures for latent heat storage enhancement

Abstract

Latent heat storage units (LHSUs) often suffer from slow phase-change dynamics, limiting their applicability. Bionic LHSUs incorporating phase change materials (PCMs), initially inspired by the arterial structure of the human circulatory system, enhance performance by improving heat accessibility through fractal tube optimization; however, phase-change rates remain moderate. To advance this approach, the design is extended to also mimic the capillary network by incorporating metal foams to enhance local conduction paths, followed by a reassessment of gradient configurations and optimization strategies. Different conventional pore parameter distributions are analyzed using the enthalpy-porosity approach and a non-equilibrium energy model for porous media. A 91.8 % performance enhancement, one of the highest for high porosity LHSUs, is achieved with a uniform metal foam-PCM composite, reducing melting time from 3811 s to 314.2 s, with a heat storage rate density of 816 J∙kg^-1∙s^-1. Further analysis shows that traditional convection-based porosity gradients deteriorate the performance, and pore-density gradients impart negligible impact, prompting the development of a novel porosity gradient strategy. Response surface methodology identifies and validates an optimized central porosity gradient, yielding additional gains. Therefore, the metal foam–PCM hybrid bionic LHSU demonstrates unprecedentedly high charging performance, paving the way for commercial applications, while the novel porosity gradient approach offers a foundation for further research and system optimization.