Numerical simulation of heat transfer performance and convective vortex evolution in a phase change thermal storage device with dispersed heat sources

A numerical model based on the enthalpy method for solidification/melting that incorporates liquid-phase convection was established for a shell-and-tube phase-change thermal energy storage device with dispersed heat sources. This model optimized the heat source structure and simulated the phase change process, thermal storage performance, and evolution and effects of convection-induced vortices. To overcome the limitations of melting blind spots in traditional inner-tube heat sources, a dispersed heating approach was introduced to optimize the heat source distribution on the inner and outer tubes without changing the heat exchange area. The optimal heat source model demonstrated superior heat transfer performance, featuring an inner-tube top heat source and three uniformly distributed outer-tube bottom heat sources at a dispersion angle of 60°. It reduced the complete melting time by 70.88% compared to the inner-tube heat source alone and by 51.99% compared to the outer-tube bottom heat source. The dispersed heat sources effectively utilized the natural convection benefits at the upper inner side and enhanced the heat transfer at the lower sections to address the melting blind spots of the central heat source, thereby improving the uniformity of the process. The enhancement in heat transfer within the dispersed heat source model is primarily due to the optimized heat source distribution, which facilitates a more dispersed and uniform vortex evolution during the phase change. This promotes the development of the liquid-solid interface and reduces the mutual interference in convection vortex expansion. Hence, the internal heat transfer rate and thermal storage capacity of the system are improved.