• 作者： Chen, Yau-Ming; Wang, Kun-Chieh
• 中文摘要： 本文乃以有限差分法配合冪次律求解渦旋-傳輸及能量方程式來研究水平橢圓管自然對流之情形。實驗量測部分則採全像干涉術法。主要變數之變化範圍為10/sup 2/.ltoreq.Ra.ltoreq.10/sup 6/,0.25.ltoreq.AR.ltoreq.4, 0. degree..ltoreq..theta./sup */.ltoreq.90.degree.。結果發現局部紐賽爾數在橢圓管其中一端之轉折處先達極大值,然後再單調遞減至另一端之轉折處。平均紐賽爾數隨長短軸比、瑞萊數、或傾角之增加而增加。由於忽略曲率效應及邊界層假設在隨圓管上方流煙區之不適用性,邊界層解無法適當地描述中或低瑞萊數之熱傳情形。此外,理論計算與實驗量測結果比較相當吻合。文中並提出平均紐賽爾數隨長短軸比及瑞萊數變化之熱傳相關式。
• 英文摘要： Laminar natural convective heat transfer from a horizontal elliptic cylinder is studied by solving the transformed vorticity-transport and energy equations using a power-law, finite-difference scheme. The experiments are performed using the holographic interferometry. Results are obtained for 10/sup 2/.ltoreq.Ra.ltoreq.10/sup 6/, 0.25.ltoreq.AR.ltoreq.4, and 0.degree..ltoreq..theta./sup */.ltoreq. 90.degree.. It is found that the local Nusselt number generally attains its maximum at one turning end of the elliptic tube and monotonously decreases to the other. The mean Nusselt number increases with increasing axis ratio (AR), Rayleigh number (Ra), or inclination angle(.theta./sup */). Boundary-layer solutions do not adequately describe the flow and heat transfer at low or moderate values of Rayleigh number because of the ignorance of curvature effects and the breakdown of the boundary- layer assumptions in the plume region. Good agreement between the calculated and the measured results is achieved. Heat correlating equations are developed for the mean Nusselt number as a function of the axis ratio and the Rayleigh number.
• 中文關鍵字： 自然對流; 橢圓柱; 渦流; 輸送方程式; 熱傳遞
• 英文關鍵字： Natural Convection; Elliptic Cylinder; Vorticity; Transfer Equation; Heat Transfer