• 作者： Chen, S.L.
• 中文摘要： 本篇的主要目的在於建立一數學模式, 以預測自由流下之層狀冷凝膜形成表面波時, 對冷凝熱傳之影響。為了避免數學上之困難, 本文假設波形為局部平行流, 表面波之數學模式可由動量平衡而得。藉著線性穩定分析與逼近法解波形表面方程式, 可得出臨界薄膜雷諾數與最易受擾動之波形頻率的封閉形式解, 由線性穩定分析的結果, 經由非線性波形分析可預測出表面波之波形, 因而可求出表面波形之平均時間冷凝薄膜厚度。當與平滑薄膜比較時, 表面波形之存在使冷凝熱傳的增加是因為平均時間冷凝薄膜厚度由於流體對流運動的影響而降低。此預測的結果與一般文獻中實驗數據的結果相符合, 而且可說明紐塞解與實驗數據之誤差。
• 英文摘要： The purpose of this work is to develop a model for predicting the effect of interfacial waviness on laminar film condensation. To avoid mathematical difficulties, local parallel-flow is assumed over the entire wave. A differential equation is obtained for the description of the interfacial surface. The frequency of the most amplified wave is determined from linear stability analyses by asymptotically solving the interface equation, which in turn is applied to obtain the time-averaged film thickness of the finite- amplitude waves. The enhancement of condensation heat transfer due to waviness is a direct consequence of the decrease in the time-averaged film thickness (compared to that of a smooth film) by convective motion of liquid. Predictions are shown to be consistent with available experimental data, and to satisfactorily account for the deviation of the data from the classical Nusselt theory.
• 中文關鍵字： 薄膜冷凝; 界面波動; 穩定分析; 層流; 熱傳遞
• 英文關鍵字： Film Condensation; Interfacial Waviness; Stability Analyses; Laminar; Heat Transfer