紊流場中微粒沉澱速度受熱泳與電場效應之影響

Thermophoretic and Electrical Force Effects on Turbulent Particle Deposition

蔡怡泰(Yi-Tai Tsai)

指導教授 ： 邱明志

國立虎尾科技大學/工程學院/車輛工程系碩士班/碩士(2012年)

摘要

本文研究目的在於探討懸浮微粒在非等溫紊流場中，主要沉降機制分析，將微粒淨通量分為擴散通量與對流通量；因近壁面濃度梯度產生的布朗擴散與壁面溫度梯度產生的熱泳效應視為擴散通量；近壁面粒子脈衝速度梯度(Turbophoresis)，電泳效應的影響視為對流通量，分別將這些影響因素依子層近似模式(Sublayer Approach Model)表示成適當的數學形式後加到粒子的連續方程式和動量方程式，然後再對方程式求得傳遞機制平均值，結果得到 預測曲線與實驗趨勢相當吻合，並且得到以下結論；
1. ：微粒主要是受到分子擴散性的影響，沉澱速度隨微粒尺寸增大
而減小。
2. ：主要是受到速度梯度(Turbophoresis)的影響，沉澱速度隨微
粒尺寸增大而上升。
3. ：微粒慣性力逐漸可抵抗紊流流體的衝擊動量，並主導最終沉澱
過程，使得沉澱速度隨微粒尺寸增大而減少。
4. 若流場中同時存在電場與非等溫場，相較於冷熱表面的影響，電場的出現對微粒沉澱速度的影響是最大的。

關鍵字

黏滯子層模式 ； 熱泳效應 ； 場充電 ； 擴散充電 ； 沉澱速度

並列摘要

The particle flux is divided into the diffusion flux on liquidity; Brownian diffusion near the wall concentration gradient and the wall temperature gradient generated by the thermophoretic effect as the diffusion flux; near wall particle pulse speed gradient (Turbophoresis,) electrophoresiseffect as on liquidity, These factors were in accordance with sub-layer approximation model (Sublayer Approach Model) into the appropriate mathematical form added to the particle continuity equation and momentum equation, then the equation to obtain the average of the transmission mechanism, These factors were in accordance with sublayer approximation model (Sublayer Approach Model) into the appropriate mathematical form added to the particle continuity equation and momentum equation, then the equation to obtain the average of the transmission mechanism, Results predicted curves are in good agreement with experimental trends, and the following conclusions
1. ：Particles by the influence of molecular diffusion, deposition velocity of the particle size decreases.
2. ：Mainly due to the influence of the velocity gradient, while the rise in the deposition rate increases with particle size.
3. ：Particle inertia force progressively resistant to the impact of turbulent fluid momentum, and led the final sedimentation process, the deposition rate increases with the particle size is reduced.
4. If the flow field at the same time the electric field and non-isothermal field compared to the impact of hot and cold surface, the electric field on the particle settling velocity is the largest.

並列關鍵字

Sublayer approach model ； Thermophoretic effect ； field charging ； Diffusion charging ； Deposition velocity

參考文獻

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