Coupled effects of shell geometry and heater eccentricity on n-eicosane melting: An enthalpy-based lattice Boltzmann study

This study investigates the coupled effects of shell geometry and heater eccentricity on the melting of n-eicosane in shell-and-tube systems, which is important for thermal energy storage applications. Three shell geometries (elliptical, circular, and square) and three heater eccentricity arrays are considered. An enthalpy-based two-relaxation-time lattice Boltzmann model is employed. Three interfacial schemes (PSM, VLB, and PBB) are first assessed using a benchmark square-cavity melting problem, and PSM is selected for its superior accuracy. The results show that melting is initially conduction-dominated and gradually transitions to a convection-dominated regime as the liquid layer develops. The coupled influence of geometry and eccentricity significantly alters flow structures and heat transfer characteristics. Among all cases, the elliptical shell with a 5 mm eccentricity achieves the best performance, reducing the total melting time by up to 56.4% compared with the circular shell with a 0 mm eccentricity. Eccentric configurations prolong the convection-dominated stage, increase Nusselt numbers, and enhance heat transfer. Meanwhile, the energy storage process is dominated by latent heat under the present conditions. Overall, natural convection governs the melting dynamics, while conduction remains non-negligible. This work provides a quantitative demonstration of the coupled role of shell geometry and heater eccentricity, offering a simple and effective strategy to optimize phase change heat transfer.