Abstract The focus of this study is on the near-wall thermal interaction of micro-particles in a vertical turbulent channel flow. Three mechanisms for the heat transfer of solid particles and the wall, when the distance between the particles and wall is less than half of the particle's radius, have been considered. The first two mechanisms are the solid-solid (Qss) and the solid-fluid-solid (Qsfsc) heat transfer of wall-colliding particles. The time of collision and the contact area are calculated based on the elastic Hertzian contact equations. The third mechanism is the solid-fluid-solid (Qsfsp) heat transfer for particles that do not hit the wall but move closely parallel to the wall. Mathematical models for these three mechanisms are implemented into an Eulerian-Lagrangian direct numerical simulation (DNS) solver for a particle Stokes number of St = 192, and a constant particle mass loading of φm= 0.54. Comparing these three mechanisms, it is shown that the heat transfer rate via the third mechanism (Qsfsp) is significantly larger than the ones of the two other mechanisms (Qss, Qsfsc). This can be contributed to the fact that some of the near wall particles stay in the laminar sublayer for a large time interval and by moving parallel to the wall they have enough time to have direct thermal interaction with the wall. The overall heat transfer rate of particle-laden flow, however, is almost unaffected by the inclusion of these thermal interactions at this mass loading and particle Stokes number. The only effect of including these near-wall particle interactions is to slightly decrease the slope of the temperature profile, the convective heat transfer, and the fluid-particle temperature difference at the near wall region.

中文翻译：

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含颗粒湍流中固体颗粒的近壁传热

摘要 本研究的重点是垂直湍流通道流中微粒的近壁热相互作用。当颗粒与壁之间的距离小于颗粒半径的一半时，固体颗粒与壁之间的三种传热机制已被考虑。前两种机制是壁面碰撞颗粒的固-固 (Qss) 和固-流-固 (Qsfsc) 传热。根据弹性赫兹接触方程计算碰撞时间和接触面积。第三种机制是固体-流体-固体 (Qsfsp) 热传递，用于不撞击壁但与壁紧密平行移动的粒子。这三种机制的数学模型在 Eulerian-Lagrangian 直接数值模拟 (DNS) 求解器中实现，其中 Stokes 数为 St = 192，粒子质量载荷为 φm = 0.54。比较这三种机制，表明通过第三种机制（Qsfsp）的传热率明显大于其他两种机制（Qss，Qsfsc）。这可能是因为一些近壁粒子在层流亚层中停留很长的时间间隔，并且通过平行于壁移动，它们有足够的时间与壁直接热相互作用。然而，在这种质量负载和颗粒斯托克斯数下，包含这些热相互作用几乎不会影响载有颗粒的流动的整体传热速率。