本文主要以數值模擬研究具自由液面液體衝擊噴流冷卻之流場與熱傳特性。文中選用狹長型噴口垂直衝擊於一平板來進行模擬，且工作流體為水。紊流統御方程式是以控制體積法為基礎，配合冪次法則有限差分法與著名的k-ε紊流模式及其相關之牆函數來求解與描述紊流結構。
數值計算採用以下參數，雷諾數Red(11000≦Red≦17000)、無因次衝擊高度H/do(3≦H/do≦12)、無因次噴嘴寬度B/do(1≦B/do≦2)以及熱通量(140kW/m2≦q’’≦280 kW/m2)，並將本文中所採用的理論模式與文獻中已發表的實驗數據作數值預測值的驗證。在此研究範圍中，無因次衝擊高度H/do=3~12的局部水力直徑紐塞數Nud 最大值均產生在停滯點，並沿其平板兩側逐漸減小，另外當增加無因次噴口寬度B/do時會增加局部紐賽數Nud之最大值。當雷諾數固定時，增加無因次噴口寬度B/do，並將無因次高度調整在H/do=6.17~12，也會使得平均紐塞數Nu增加。
此外，將模擬結果與文獻中可用實驗數據做仔細的驗證後，再利用反應曲面法(response surface methodology)和基因演算法(genetic algorithm method)來對入口幾何形狀以及衝擊高度作最佳化。對於本物理模型而言，其最佳化設計的結果是在H/do=7.86和B/do=2 。

In this study, the fluid flow and heat transfer characteristics of a free surface liquid jet impingement cooling have been investigated numerically. The slot jet nozzle impinging normally on a flat plate are employed and the impinging coolant is water. The turbulent governing equations are solved by a control-volume-based finite-difference method with power-law scheme and the well-know turbulence model and its associate wall function to describe the turbulent structure.
Numerical computations have been conducted with variations of jet exit Reynolds numberRed(11000≦Red≦17000), dimensionless jet-to-surface distanceH/do(3≦H/do≦12), dimensionless jet widthB/do(1≦B/do≦2) and the heat flux(140kW/m2≦q’’≦280 kW/m2). The theoretical model developed is validated by comparing the numerical predictions with available experimental data in the literature. In these studied ranges, the variations of local Nusselt numbers by hydraulic diameter Nud of the dimensionless jet-to-surface distance H/do=3~12 along the flat plate decrease monotonically from its maximum value at the stagnation point. Moreover, the maximum value of (Nud) increases with the increase in the jet width B/do . As the Reynolds number fixes, the value of average Nusselt (NU) increases when jet width B/do increases and jet-to-surface distance is .

In addition, the shape of the inlet area and jet-to-surface distance are optimized by using response surface methodology (RSM) and genetic algorithm (GA) method after solutions are carefully validated with available experimental results in the literature. Based on the optimal results, the optimum condition is in H/do=7.86 and B/do=2 for this physical model

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