Thermal Performance Enhancement of a Biomimetic Fish-Fin Latent Heat Storage Unit Using CNTs-COOH/Erythritol Composite Phase Change Material

Abstract Phase change energy storage is a key technology for mitigating the volatility and intermittency of renewable energy and plays an important role in improving the efficiency, stability, and reliability of energy systems. To enhance the thermal conductivity of erythritol (Ery), this study introduces carboxylated carbon nanotubes (CNTs-COOH) as a high-thermal-conductivity filler into the Ery matrix to prepare a composite phase change material (CPCM). Inspired by biomimetic principles, a biomimetic fish-fin latent heat storage structure was designed. A series of characterizations were conducted on the CPCM, and the effects of fin eccentricity (FE) and fin inclination angle on the thermal storage performance were investigated through numerical simulation. The results show that the CPCM with 3 wt % CNTs-COOH exhibits thermal conductivities of 0.531 and 0.433 W/(m·K) at 80 and 150 °C, respectively, representing increases of 14% and 20% compared with pure Ery. CNTs-COOH effectively inhibit nanoparticle aggregation. Eccentric fins alleviate the slow heat transfer issue at the bottom of the thermal storage unit and improve phase change material (PCM) temperature uniformity. The configuration with FE = 5 mm exhibits the best thermal performance, reducing the complete melting time by 22% compared with FE = 0 mm and increasing both heat storage capacity and heat storage power by 2.4%. The effect of fin angle on the melting process follows a trend of “initially slow and subsequently rapid”. At 2160 s, compared with the 45° configuration, the 90° and 130° configurations significantly enhance convective heat transfer. Among them, the 130° configuration increases heat storage capacity by 2.93% and reduces the complete melting time by 10%.