Abstract This article aims to explore the effects of buoyancy force and thermal boundary condition on the mixed convection heat transfer performance of air in a horizontal microchannel. Three different heat flux models, including bottom wall heated, top wall heated (single wall heating – a novel heating approach compared to recent studies) and both walls heated, are analyzed at four different values of the Grashof number (Gr = 0, 100, 300, 600) using a lattice Boltzmann method (LBM). The slip velocity boundary condition is also applied to the bottom and top walls. It can be found that the buoyancy force changes the velocity distribution structure near the bottom wall and top wall, particularly at the inlet regions in all models, and a negative slip velocity is generated due to the backflow formed at a relatively large Grashof number and it strictly determines the local wall friction coefficient. Either the bottom wall or the top wall is heated. A vortex is found close to the top wall because the mixing position of the hot and cold fluids is in the vicinity of the top wall. This feature facilitates the heat transfer near the top wall and core flow zone. The thermal performance is most positive for the case when the top wall is heated due to the generation of an induced vortex and no influence of the vortex near the bottom wall.

中文翻译：

---

不同加热条件下微通道滑流与传热的LBM建模与分析

摘要 本文旨在探讨浮力和热边界条件对水平微通道中空气混合对流换热性能的影响。三种不同的热通量模型，包括底壁加热、顶壁加热（单壁加热 - 与最近的研究相比是一种新颖的加热方法）和双壁加热，在四个不同的 Grashof 数值（Gr = 0、100、 300, 600) 使用格子 Boltzmann 方法 (LBM)。滑动速度边界条件也适用于底壁和顶壁。可以发现，浮力改变了底壁和顶壁附近的速度分布结构，特别是在所有模型的入口区域，由于在较大的 Grashof 数下形成回流而产生负滑移速度，它严格确定了局部壁面摩擦系数。加热底壁或顶壁。因为冷热流体的混合位置在顶壁附近，所以在顶壁附近发现涡流。该特征促进了顶壁和核心流动区附近的热传递。当顶壁由于产生感应涡流而被加热而底壁附近的涡流没有影响时，热性能最积极。该特征促进了顶壁和核心流动区附近的热传递。当顶壁由于产生感应涡流而被加热而底壁附近的涡流没有影响时，热性能最积极。该特征促进了顶壁和核心流动区附近的热传递。当顶壁由于产生感应涡流而被加热而底壁附近的涡流没有影响时，热性能最积极。