Bao Fubing, Hao Hanbo, Yin Zhaoqin, Tu Chengxu
Institute of Fluid Measurement and Simulation, China Jiliang University, Hangzhou 310018, China.
Micromachines (Basel). 2021 Jan 1;12(1):47. doi: 10.3390/mi12010047.
Nanoparticle deposition in microchannel devices inducing contaminant clogging is a serious barrier to the application of micro-electro-mechanical systems (MEMS). For micro-scale gas flow fields with a high Knudsen number () in the microchannel, gas rarefaction and velocity slip cannot be ignored. Furthermore, the mechanism of nanoparticle transport and deposition in the microchannel is extremely complex. In this study, the compressible gas model and a second-order slip boundary condition have been applied to the Burnett equations to solve the flow field issue in a microchannel. Drag, Brownian, and thermophoretic forces are concerned in the motion equations of particles. A series of numerical simulations for various particle sizes, flow rates, and temperature gradients have been performed. Some important features such as reasons, efficiencies, and locations of particle deposition have been explored. The results indicate that the particle deposition efficiency varies more or less under the actions of forces such as Brownian force, thermophoretic force, and drag force. Nevertheless, different forces lead to different particle motions and deposition processes. Brownian or thermophoretic force causes particles to move closer to the wall or further away from it. The drag force influence of slip boundary conditions and gas rarefaction changes the particles' residential time in the channel. In order to find a way to decrease particle deposition on the microchannel surface, the deposition locations of different sizes of particles have been analyzed in detail under the action of thermophoretic force.
纳米颗粒在微通道装置中沉积导致污染物堵塞是微机电系统（MEMS）应用的严重障碍。对于微通道中具有高克努森数（）的微尺度气体流场，气体稀薄化和速度滑移不可忽视。此外，纳米颗粒在微通道中的输运和沉积机制极其复杂。在本研究中，可压缩气体模型和二阶滑移边界条件已应用于伯内特方程，以解决微通道中的流场问题。颗粒运动方程中考虑了曳力、布朗力和热泳力。针对各种颗粒尺寸、流速和温度梯度进行了一系列数值模拟。探索了颗粒沉积的一些重要特征，如原因、效率和位置。结果表明，在布朗力、热泳力和曳力等作用下，颗粒沉积效率或多或少会有所变化。然而，不同的力导致不同的颗粒运动和沉积过程。布朗力或热泳力会使颗粒靠近壁面或远离壁面移动。滑移边界条件和气体稀薄化的曳力影响改变了颗粒在通道中的停留时间。为了找到减少颗粒在微通道表面沉积的方法，详细分析了在热泳力作用下不同尺寸颗粒的沉积位置。
