Numerical simulation of constrained melting inside spherical capsule by lattice Boltzmann method
(2.State Key Laboratory of Coal Mine Safety Technology, CCTEG Shenyang Research Institute, Shenyang, Liaoning, China 110016)
【Abstract】Phase change materials (PCMs) are mainly used to provide high storage densities. The spherical geometry is one of the most interesting cases for heat storage applications. The present study used the lattice Boltzmann method (LBM) to investigate constrained melting process of PCMs in a spherical capsule, which can be useful for the study on phase change phenomenon of microencapsulated PCM slurry in the future. The phase interface is traced by updating the total enthalpy, while the moving interface is treated by the immersed moving boundary scheme. The computational results of the melting process of PCMs are analyzed at different scales. The numerical simulations at macro-scale are compared with the published experimental data, and the results clearly show that the thermal stratification is in the upper spherical capsule while the waviness phase front is at the bottom of the solid PCM. Quantitative analysis of the temperatures at nine points, eight points along the vertical axis and the other one near the inner shell, further indicates the existence of chaotic convective motion at the bottom of the spherical capsule. In addition, the effect of the natural convection on the melting process is reduced with the decrease of capsule sizes. When the diameter of capsule is less than 3 mm, the natural convection can be ignored.
【Keywords】 phase change; multiscale; numerical simulation; thermodynamics; lattice Boltzmann method;
(Translated by CAI TX)
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