楔形流場中在磁場影響下氣膠傳輸機制之研究

A Study of Transport Mechanisms of Aerosol Particles under Magnetic Field on the Wedge Flows

郭政忠(Zheng-Zhong Kao)

指導教授 ： 蔡瑞益

中原大學/工學院/機械工程研究所/碩士(2004年)

https://doi.org/10.6840/cycu200400347

摘要

本文探討氣膠微粒在受到熱泳效應和磁場效應時，對於氣膠微粒在一楔形流場之微粒附著速度的影響。這兩種傳輸機制的交互作用，對微粒附著速度有相當重要性。氣流流場考慮不可壓縮、二維層流之楔形流場，其統御方程式包括動量、能量及濃度場方程式。數值方法用Box method與區塊消去法解其統御方程式，進而計算出氣膠微粒附著速度，微粒粒徑選擇為0.01~100。

同時考慮擴散效應、磁場效應和熱泳效應時，我們發現當微粒粒徑很小時(dp<0.1)，微粒附著速度是受到布朗擴散和熱泳機制影響。微粒粒徑愈小、Eckert number愈大，則微粒附著速度愈大。而磁場效應向下時使微粒往板塊吸附，因此磁場愈大微粒附著速度愈大；而磁場效應向上時反而讓微粒附著通量減少，因此磁場愈大微粒附著速度愈小。

關鍵字

熱泳效應 ； 楔形流 ； 微粒附著沉積率 ； 磁性流體

並列摘要

The study of aerosol particle deposition rate affected by thermophoresis and hydromagnetic flow effect onto a plane stagnation flow are reported. The interaction between these two transport mechanisms is expected to be very important for particle deposition rate. In this study, the air flow was modeled as incompressible two dimensional laminar wedge flow. The governing equations include conservation of mass, momentum, energy and concentration. Similarity analysis with the Box method and block elimination was used to determine these governing equations. We can obtain aerosol particle deposition velocity by solving these governing equations. Particle is selected in a range of 0.01~100.

As Brownian diffusion effect, hydromagnetic flow effect and thermophoresis effect are considered, we can find that particle deposition rates are controlled by Brownian diffusion effect and thermophoresis effect for ultra-small particle sizes(dp<0.1). Particle sizes will become smaller when Eckert number become larger. And the particle deposition rates will increase. When hydromagnetic flow effect direction is downward, the particle will be sucked onto the plate, so particle deposition rates will increase with the hydromagnetic flow magnitude. Oppositely, when the hydromagnetic flow effect direction is upward, the particle deposition flux will decease, so if the hydromagnetic flow become intensitive, particle deposition rate will turn into weaker.

並列關鍵字

thermophoresis ； hydromagnetic flow ； particle deposition rates ； wedge flow

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