臺灣博碩士論文加值系統

　　本文分別探討一等溫傾斜板及具飽和多孔性介質等溫傾斜板之液態薄膜蒸發問題，以數值方法分析相關參數對熱質傳特性之影響。研究範圍包括下列幾個重點：

　　一、探討淋水於一傾斜等溫板，淋水量、空氣流量、傾斜角度等參數對熱流場之影響。數值分析於流動方向(x方向)的對流項用上游法(upstream difference method)來差分，y方向的對流項及擴散項則用中央差分法(central difference method)，所得到之差分式利用Box method方法求解。數值結果得到當淋水量小及傾斜角度小，則水薄膜厚度及介面速度的變化明顯，此時空氣－液體介面溫度、濕度均較高，截面蒸發量亦較大。當淋水量為空氣0.3%時，有淋水情況相對於乾流場能夠增加8%至22%的熱傳量，而數值與實驗誤差約為20%。

　　二、探討具飽和含水之多孔性介質等溫傾斜板熱流場，考慮非達西定律中之慣性效應(inertia effect)、邊界效應(boundary effect)。分析孔隙率e、多孔性介質厚度d、環境相對濕度f等相關參數對此機構熱質傳遞之影響。結果發現在低孔隙率、低薄膜厚度時有較高的介面溫度及濕度，平均紐賽數 及平均薛爾塢數 均較大，環境相對濕度較低之情況下會造成較高之 值及較低之 值。另外，熱質傳遞能力亦隨著路易斯數Le增加而增加。

Abstract
　Two main topics have been studied numerically in this thesis：First is to study the co-current liquid film evaporation along an inclined plate. The second is to evaluate the heat and mass enhancement of liquid film evaporation by covering a porous layer. The present investigations include：
　
　(1) For the liquid film evaporation along an inclined plate, the parametric analyses such as the inlet water flow rate, inlet air flow rate and the angle of inclination are examined in detail. For numerical analysis, the upstream scheme is used to model the convection term in flow direction (x direction), while the second-order central difference schemes are employed for the transverse convection and diffusion terms. The discretization equations are solved by the Box method. The numerical results show that the variations of liquid film thickness and liquid velocity are significant for lower inlet liquid mass flow rate and inclination angle. And the interfacial temperature and concentration are increased for such above situations. In addition, as the liquid mass flow rate is 0.3% of the air flow, the heat transfer enhancement is about to 8%~22%. Compared with the experimental results, the error of numerical results are within 20%

　(2) For the liquid film evaporation covered with a porous layer, the non-Darcy inertia and boundary effects are included. The corresponding parametric analyses on features such as gas inlet conditions (Reynolds number and ambient relative humidity f) and the structural properties of the porous material (porosity e and thickness of the porous layer d) on the performance of liquid film evaporation are examined in detail. The results show that both the average Nusselt and Sherwood numbers are increased with the decrease of e, d and f. In addition, as the Lewis number increases (Le>1), a larger heat transfer rate and mass flow rate are achieved.

目 錄
摘要 I
英文摘要 II
致謝 IV
目錄 V
表目錄 VII
圖目錄 VIII
符號說明 XII
1.1 研究目的及背景 1
1.2 文獻回顧 2
第二章 多孔性介質之簡介 8
2.1 達西定律 8
2.2 非達西定律 9
第三章 理論分析 15
3.1 有噴霧時濕盤管理論分析 15
3.2 傾斜板置入流體飽和多孔性介質理論分析 22
3.3 熱質傳係數之計算 27
第四章 數值方法 32
4.1 一般流體薄膜蒸發數值方法 32
4.2 具多孔性介質蒸發方法 35
第五章 結果與討論 40
5.1 一般流體薄膜蒸發數值結果 40
5.2 數值與實驗比較之結果 42
5.3 具多孔性介質薄膜蒸發數值結果 43
第六章 結論 73
參考文獻 75
自述 80

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