Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/2480
標題: 各種孔數三維撞擊噴射流流場之熱傳數值模擬與分析
Three-Dimensional Numerical Simulation and Analysis of Heat Transfer by the Multiple Impinging Jet
作者: 王建中
Wang, chien chung
關鍵字: jet;噴嘴;reynold number;impinging;fountain effect;雷諾數;噴射衝擊;噴泉效益
出版社: 機械工程學系
摘要: 
摘 要
本文利用計算流體力學套裝軟體FLOTHERM對單孔、雙孔、三孔噴射衝擊於散熱板之熱傳做數值模擬分析。流場為三維並假設不可壓縮流。紊流統御方程式以控制體積法配合有限差分法來離散差分方程式。紊流模式採用Lam & Bremhorst之 雙方程式。數值計算方面採用交錯式體系(Staggered Grid System)混合體系(Hybrid Scheme)及SIMPLEST求解程序來解速度、壓力、溫度。本文研究主要的參數為噴嘴數(N) ,噴嘴孔徑(d),雷諾數(Re), 高度孔徑比(h/d), 孔距孔徑比(s/d)等,並分析它們對流場之速度溫度與熱傳的影響。本文所分析之單孔噴射撞擊的噴嘴孔徑為d=1.5, 3, 4.5, 6mm,高度孔徑比h/d=4,6,8 , Re=8200,10820, 13149。其中散熱不鏽鋼板厚度為1 mm ,底下為固定熱源板熱通量為1500W/㎡ ,噴嘴長度固定L=3mm。在雙孔噴射撞擊流流場中,固定噴嘴孔徑d=3mm ,高度孔徑比 h/d=4,雷諾數Re=10820,而孔距孔徑比變數為s/d=4,6,8。在三孔噴射撞擊流中,三孔排列分為一直線及三角形兩種型式,同時固定噴嘴孔徑d=3mm ,高度孔徑比 h/d=4 ,雷諾數Re=10820,而孔距孔徑比變數為 s/d= 4,6,8。
本文模擬所得結果為單孔噴射撞擊於固定雷諾數時,孔徑尺寸愈小熱傳效果愈佳。在相同孔徑尺寸d及高度孔徑比(h/d)條件下,雷諾數愈大熱傳效果愈佳。另外當固定孔徑尺寸d及雷諾數條件下,高度孔徑比(h/d)值愈較小熱傳愈佳。多孔噴射撞擊在相同孔徑尺寸d、高度孔徑比(h/d)及雷諾數條件下,孔距/孔徑比(s/d)影響熱傳效果,當孔距/孔徑比(s/d)愈小,流場相互干擾造成噴泉效應使得熱傳效果愈差,當孔距/孔徑比 s/d>8干擾不明顯,流場漸恢復單孔噴射衝擊趨勢。本文研究結果可提供業者在設計固體表面冷卻上做參考。
關鍵字:噴嘴,噴射衝擊,雷諾數,噴泉效應

Abstract
In this study, a computational fluid dynamics (CFD) code of FLOTHERM was used to simulate the heat transfer of the three-dimension single /multiple jet impinging on the heat flux flat plate. The turbulent governing equations were solved by a control -volume-based in finite difference method . The turbulent structure was described with well known Lam & Bremhorst k-e two-equation model .The turbulence model was Staggered Grid System and Hybrid Scheme . The SIMPLEST algorithm was adopted to solve the governing equations of velocity, pressure and temperature . The parameters of this study were jet number (N), jet diameter (d), Reynolds number(Re), ratio of jet height to diameter (h/d), ratio of jet spacing to diameter of (s/d).
The simulated parameters of single jet were different jet diameter (d=1.5, 3, 4.5, 6mm), Reynolds number (Re=8200, 10820, 13149) and ratio of jet height to diameter (h/d=4, 6, 8) . The thickness of stainless heating plate was 1mm. The flux of heating plate was fixed at 1500 kw/㎡, The jet length was fixed L=3mm. The simulated parameters of two jets impinging were different ratio of jet spacing to diameter (s/d=4, 6, 8) by fixed (d=3mm, Re=10820, h/d=4).Three impinging jets had two geometry array type such as in one line and in triangular . The simulated parameter was fix (d=3mm, Re=10820, h/d=4) and different ratio of jet spacing to jet diameter were (s/d=4, 6, 8).
The result of single impinging was the smaller jet diameter the better heat transfer when fixed (Re=10820, h/d=4) . The bigger Reynolds number had the better heat transfer when fixed(d=3mm, h/d=4).The smaller ratio of jet height to diameter (h/d) had the better heat transfer when fixed (d=3mm, Re=10820) . The result of multiple jets impinging was when fixed (d=3mm, Re=10820, h/d=4) the smaller ratio of space diameter (s/d) had the fountain effect and influenced the heat transfer. The result could be afforded to the designation of solid material surface cooling.
Keywords: jet, impinging flow, fountain effect
URI: http://hdl.handle.net/11455/2480
Appears in Collections:機械工程學系所

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