| Resumo : |
Thermal energy storage (TES) systems are essential for enhancing energy efficiency and sustainability, particularly in applications requiring passive or intermittent thermal regulation. Phase Change Materials (PCMs) are highly effective in this context due to their large latent heat capacity; however, their inherently low thermal conductivity limits the overall heat transfer rate. This study investigates the melting behavior of a high-Prandtl number PCM (lauric acid) using the enthalpy-porosity method, modeling the flow as incompressible, Newtonian, laminar, and transient, with temperature-dependent thermophysical properties and buoyancy effects for increased fidelity. In the first stage, three symmetric aluminum-finned heat sink configurations with fin lengths ranging from 0.02 to 0.04 m were evaluated. The results showed that the fins significantly enhanced heat transfer by generating multiple thermal boundary layers; however, excessive fin density suppressed natural convection, ultimately reducing long-term thermal storage capacity. Among the tested geometries, the configuration with balanced fin spacing achieved the highest melting performance, outperforming the least efficient case by up to 33% in terms of stored thermal energy and 31% in terms of melted mass. A correlation relating the fin volume fraction, Fourier number, and Nusselt number was also developed. In the second stage, a surrogate-based optimization was conducted. A response surface model (RSM) was trained using the CFD dataset to represent the relationship between the fin length and thermal performance metrics. A Multi-Objective Genetic Algorithm (MOGA) was then applied to maximize the heat transfer indicators (liquid fraction and Nusselt number) while minimizing the geometric constraints (volume fraction). The optimization converged on an asymmetric fin configuration that improved the Performance Evaluation Criterion (Z) by 0.15%, increased the Nusselt number by 0.23%, and reduced the heat sink volume by 3.2%, albeit with a 4.6% reduction in the liquid fraction at the evaluation time. Overall, the results highlight the critical interplay between conduction, natural convection, and fin geometry in the thermal management of PCMs. They also demonstrated the effectiveness of surrogate-based optimization in identifying compact, high-performance heat sink designs for latent heat storage applications. |