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COBEM 2021
26th International Congress of Mechanical Engineering
MULTI-BLOCK LATTICE BOLTZMANN METHOD APPLIED TO CONDUCTION IN TWO SOLIDS WITH LARGE DIFFERENCE BETWEEN THERMAL DIFFUSIVITIES
Submission Author:
Ivan Talão Martins , SP , Brazil
Co-Authors:
Ivan Talão Martins, Luben Cabezas Gómez
Presenter: Ivan Talão Martins
doi://10.26678/ABCM.COBEM2021.COB2021-0210
Abstract
Many real conjugate heat transfer problems involve materials with high differences between their thermal properties, principally treating of heat exchangers with small channels. In those devices, commonly there are solids (such as metals, with large thermal conductivity and diffusivity) and fluid regions (including water, that has small thermal diffusivity). Nonetheless, treating these problems with the conventional Lattice Boltzmann method (LBM) becomes a challenge. This is because even with the use of special treatment of the interfaces to guarantee the continuity of the heat flux and the temperature, there are still problems involving the simulation scales, which impact in the value of the relaxation times (tau) for both materials. Appropriate values of this parameter for the fluid regions lead to not appropriate values for the solid region, resulting in poor accuracy of the results. In order to solve this problem, it is proposed the LBM with the multi-block scheme, that allows a non-equal discretization of the whole domain. In this way, using different scales for each domain (solid and fluid), it is possible to adjust the tau to appropriate values in each region, obtaining a good accuracy. Thereby, two problems are studied in this work. The first is a benchmark problem that consists in the conjugate heat transfer between 2 solids, which can be reduced to 1D-problem. In this problem, it is shown the loss of accuracy with the increase of the difference between the thermal diffusivities of both solids. Subsequently, a problem closer to real situations in heat exchangers is studied, involving metallic (silicon) and static fluid (water) domains. Both problems are solved whit the conventional and multi-block LBM for comparing the obtained results. It is concluded that the multi-block scheme applied to LBM allows to study more complex conjugate heat transfer problems, involving large difference between the thermal properties of the materials, improving the accuracy and stability of the method.
Keywords
Lattice Boltzmann method, conjugate heat transfer problem, multi-block, heat diffusion problem
