Velocity field measurement and heat transfer characteristics of the melting process under constant heat flux

• Published in: International journal of heat and mass transfer 2024-08, Vol.228, p.125636, Article 125636
• Main Authors: Li, Boyu, Selvakumar, R．Deepak, Alkaabi, Ahmed K., Wu, Jian
• Format: Article
• Language: English
• Subjects: Constant heat flux; Finite-volume method; Melting process; Velocity field measurement
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2024.125636

•A visual melting experiment device for velocity fields was established.•A numerical model considered conjugate heat transfer was developed.•The flow and heat transfer characteristics were discussed under the heat fluxes.•A 74 % reduction in the melting time was achieved at the 3000 W m−2 condition. Thermal energy storage based on phase change materials plays a crucial role in achieving net-zero carbon emissions and recovering waste thermal energy. However, the accurate experimental velocity fields and the simulation with the conjugate heat transfer are inadequate for the constant heat flux condition. Herein, a transparent melting experiment platform is established under constant heat flux and convection cooling with constant temperature. Non-invasive measurement technology is employed to calculate the velocity field of the liquid phase. A numerical model considered conjugate heat transfer is developed via the finite volume method, demonstrating good agreement against the experimental data. The findings indicate that experiments obtain reliable data for the numerical model. The melting process consists of three distinct stages: conduction-dominated, convection-dominated, and post-region, with a sharp decrease, increase, and gradual decrease in the Nusselt number, respectively. Stronger convective heat transfer coefficients rise when heating vertically. Moreover, the hot wall remains at the equilibrium temperature when input power is equal to the absorbed energy under the discussed heating conditions. Increasing the heat flux from 1000 to 3000 W m−2 results in a temperature rise to 57.3 ºC at the heating wall and a 74 % reduction in the complete melting time. This study contributes to the understanding of the melting process through combined experimental and simulation approaches under constant heat flux boundary conditions.