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| 題 名 | 浮力效應對於垂直管進口段之混合對流熱傳的影響 |
|---|---|
| 作 者 | 魏正琪; | 書刊名 | 技術學刊 |
| 卷 期 | 7:4 1992.12[民81.12] |
| 頁 次 | 頁381-386 |
| 分類號 | 440.137 |
| 關鍵詞 | 垂直; 段; 效應; 浮力; 混合; 對流; 管進; 熱傳; |
| 語 文 | 中文(Chinese) |
| 中文摘要 | 本文以數值解析流體在無限長垂直圓管內加熱流動,浮力效應對於速度及溫度分佈同時發展的影響。利用Galerkin有限單元法同時求解完全的守恆微分方程式,藉此研究混合對流在垂直管進口段的熱傳問題。文中針對管壁恆溫加熟的邊界條件下,空氣以穩態層流(Re=50)向上流動,不同的Gr/Re值對於速度分佈、溫度分佈、局部納塞數及進口管長的變化加以討論。研究結果顯示浮力效應將會扭曲流體的速度分佈,增加自然對流的強度,進而提高熱傳率;流體在X* =0.02~0.03,浮力效應的影響最為顯著p 將大幅降低軸向中心速度及增加局部納塞數。同時獲知當Gr/Re≦71,流體呈現逆流的情形。 |
| 英文摘要 | A numerical analysis for the heated fluid in an infinite vertical tube is conducted to study the buoyance effects on the simultaneously developing hydrodynamic and thermal field. The coupled governing equations for the problem of combined forced-free laminar convection in the entrance region of the tube have been solved by applying the Galerkin finite element method. In addition, the boundary condition is considered as constant wall temperature for the upflow of air inside the tube with Re = 50. A parametric investigation is used to study the effect of Gr/Re to the local Nusselt number, the entrance length, the velocity and temperature profiles. The results reveal that the buoyance highly distorts the velocity profile, especially at x* = 0.02 - 0.03 in which the centerline axial velocity dramatically decreases while the local Nusselt number increases. As a consequence, the natural convection and the rate of heat transfer are increasing. Reverse flow is also observed at Gr/Re≧71. |
本系統中英文摘要資訊取自各篇刊載內容。