- 學位論文
渠道流經粗糙凸塊內微粒附著沉積之研究
A Study of Particle Deposition onto Roughness Surface with ribs in the Channel Flow
摘要
本文目的在探討空氣在低雷諾數 紊流模式下，在平行粗糙渠道間之流場、溫度場及微粒附著沉積之應用。並利用計算流體力學套裝軟體PHOENICS來作數值模擬。在渠道間以二維穩定流場狀態來考慮，粗糙度是以凸出方塊來表示。制御方程式之建立包括連續、動量、能量及濃度方程式。在流場探討迴流區大小與粗糙高度和渠道寬度之比值(h/D)有關，另外也探討凸塊高度與摩擦因子之關係。溫度場則以固定熱通量為邊界條件。濃度場則以無因次微粒鬆弛時間與無因次沉降速度來探討。粗糙度的影響包括流場、溫度場及濃度場。主要結果如下：(1)凸塊後面迴流區域約為粗糙高度6倍，但與節距和凸塊高度之比值(p/h)無關，所以凸塊越大迴流區域越大。(2)凸塊越大壓力降越大，所以摩擦因子越大。(3)渠道溫度隨著粗糙凸塊高度增加而增加，而雷諾數越大溫度越小。(4)無因次微粒沉積速度隨著凸塊節距增加而減少。(5)在相同節距時，凸塊高度越大無因次微粒沉積速度越小。
並列摘要
The purpose of this study is to determine the air flow field, temperature field, and the particles deposition with the low Reynolds number turbulent flowing in a channel with roughness ribs. The PHOENICS CFD software package is used for calculation the physical model. The channel is decided in steady flow of two dimensions; by the way, the roughness also is decided on overhang of rib. The govern equations are include to continue equation, momentum equation, energy equation and concentration equation. In the flow field, the major objective is studying the recirculation region within channel and roughness height of ribs that they do have relate with ration (h/D) of channel width, In addition, it also study about relation between ribs height and friction factor. The temperature field is defined fix heat flux for boundary conditions, beside, the concentration filed is studying between relax time of deposition of non-dimensional particles and velocity of deposition of non-dimension. Roughness affected the flow field, temperature field and concentration field. The major results are follow as：(1) Recirculation region is about six times of roughness height after ribs, but the pitch is not relax with ratio (p/h) of ribs height, so, the bigger ribs, the larger recirculation region. (2) The bigger ribs, the larger the pressure drop and friction factor. (3) The channel temperature is increased with rib height, but the bigger Reynolds numbers, the smaller the temperature. (4) If the rib pitch is increase, the velocity of deposition of non-dimensional particles is lower. (5) As the same pitch, the higher rib, the smaller the velocity of deposition of non-dimensional particles.
參考文獻
延伸閱讀
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