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首页> 外文期刊>Journal of Aerosol Science >Effect of thermophoresis and its mathematical models on the transport and deposition of aerosol particles in natural convective flow on vertical and horizontal plates
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Effect of thermophoresis and its mathematical models on the transport and deposition of aerosol particles in natural convective flow on vertical and horizontal plates

机译：热泳及其数学模型对垂直平板和水平平板上自然对流中气溶胶颗粒传输和沉积的影响

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摘要

An analysis is performed to study aerosol particle transport and deposition onto an isothermal horizontal or vertical plate due to the combined effects of laminar natural convectioa Brownian diffusion and thermophoresis. Four configurations are considered: flow above a heated horizontal plate, flow beneath a cold horizontal plate, flow due to a heated vertical plate and that due to a cold vertical plate. Nano- to micro-sized particles (particle diameter in the range 1 nm to 5 μm) in air are considered. It is found that the deposition velocity decreases with an increase in particle diameter d_p (Le. an increase in particle Schmidt number Sc), and increases with a decrease in the value of non-dimensional temperature difference AT (from positive to negative values). For a downward-facing cold horizontal plate or cooled vertical plate, the thermal drift of particles assists Brownian diffusion which enhances deposition velocity. For an upward facing heated horizontal plate or heated vertical plate, the thermal drift away from the surface decreases the overall deposition velocity which decreases drastically above a certain particle size. It is shown that the thermal drift may enhance the deposition rate by several orders of magnitude under certain circumstances. The profound role of using different expressions for the thermophoretic force coefficient (k) is assessed. It is found that the deposition velocity calculated using the expression for k suggested by Talbot et al. (1980) is always higher than the values predicted by employing the expression proposed by Beresnev and Chernyak (1995).
机译：由于层流自然对流布朗扩散和热泳的共同作用，进行了一项分析研究气溶胶颗粒在等温水平或垂直板上的运输和沉积。考虑了四种配置：在加热的水平板上流，在水平的冷板上流，由于加热的垂直板和因垂直的冷板而产生的流。考虑了空气中的纳米级至微米级颗粒（粒径在1 nm至5μm范围内）。已经发现，沉积速度随着粒径d_p的增加而降低（例如，粒子施密特数Sc的增加），并且随着无量纲温度差AT的值减小（从正值到负值）而增加。对于朝下的冷水平板或冷却的垂直板，颗粒的热漂移有助于布朗扩散，从而提高了沉积速度。对于面朝上的加热的水平板或加热的垂直板，远离表面的热漂移会降低总沉积速度，总沉积速度会在一定粒径以上急剧降低。结果表明，在某些情况下，热漂移可能会使沉积速率提高几个数量级。评估了对热泳力系数（k）使用不同表达式的深刻作用。发现使用塔尔伯特（Talbot）等人建议的k的表达式计算的沉积速度。 （1980）总是高于采用Beresnev和Chernyak（1995）提出的表达式所预测的值。

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