Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/18296
標題: 矩形空間內低溫水在飽和多孔性介質中之時變共軛熱傳分析
Transient Conjugate Natural Convection of Cold Water in Rectangular Enclosures Filled with a Saturated Porous Medium
作者: 金展慶
King, Chan-Ching
關鍵字: inversion papameter
最大密度參數
anisotropic
Nusselt number
Darcy Modified Rayleigh number
非等向性
紐塞數
達西修正雷里數
出版社: 應用數學系
摘要: 摘 要 本文係以SIMPLE數值方法來探 討具邊牆壁厚熱傳導之矩型封閉空間內充滿低溫水之等向性多孔性介質的 暫態對流熱傳問題(A模型)及研究低溫水在非等向性多孔性介質矩型限定 空間中的穩態自然對流問題(B模型)。A 、B兩模型中多孔性介質流場之數 學模式均採用達西(Darcy)模式來描述整個流場流動特性。低溫水的密度- 溫度關係式是引用Gebhart and Mollendorf [7] 的非線性關係式。 本文A模型主要探討高溫邊壁溫度 、固-液之熱傳導係數比KR、最大密度 參數R、邊牆厚度S、固-液之熱擴散係數比AW等參數對流場、溫度場及熱 傳量大小的影響。而B模型則研究最大密度參數R與多孔性介質中非等向性 滲透率比K*和熱擴散係數比AR對流場、溫度場及熱傳量大小的影響。 由數值計算結果顯示:密度-溫度之非線性關係因子對溫度場、流場以及 熱傳量有顯著的影響。邊牆的熱傳導會減少封閉空間內固-液左右兩邊的 溫度差及降低對流熱傳效應。固-液傳導係數比KR愈大,則其等溫線會完 全集中內流場,故根據多孔性介質的性質選擇固體邊壁材料是一重要考慮 因素。左壁面熱傳量之大小並不隨其壁面溫度值之增加而遞增,會存在一 最小熱傳量之高溫面溫度且其溫度值會隨熱傳導係數比的遞增而遞減。非 等向滲透比K*愈大將減少對流強度,非等向熱擴散係數比AR愈大也會減少 對流強度。
ABSTRACT This thesis presents a numerical solution based on SIMPLE algorithmof the transient conjugate natural convection heat transfer of cold waterin a rectangular enclosure filled with saturated porous medium andsurrounded with four solid wall. Two physical models are included :Model A is the study of conjugate natural convection heat transfer ofcold water in a rectangular enclosure filled with an isotropic porousmedium. Model B is the problem of steady thermal convection of coldwater in a rectangular enclosure filled with anisotropic porous medium.In both models, the density of cold water as a function temperature isbased on the Gebhart and Mollendorfs' nonlinear density-temperaturerelation [7]. The mathematical model for the interior flow adopts theDarcy Law to describe the overall flow field. In model A, we investigates the influences of the inversionparameter, the conductivity ratio of wall to flow, wall thickness,thermal diffusivity ratio of wall to fluid, and the inversion parameteron the fluid flow and heat transfer characteristics. While the effect ofthe inversion parameter, anisotropic permeability and the thermaldiffusivity ratio on the convective heat transfer are analyzed in themodel B. Numerical results indicate that the nonlinear density-temperaturefactor has a strong influence on the both temperature fields, flowfields, and heat transfers. Wall heat conduction can reduce thetemperature difference between walls in enclosure and the convectiveheat transfer rate. Therefore, it is an important factor to select aproper material of solid wall which depends very much on theproperties of porous medium. On the left exterior wall of theenclosure, high temperature region does not necessarily mean highheat transfer. Instead, there exists a minimum heat transfer region onthe high temperature of the surface. For the anisotropic porous media,the higher the anisotropic permeability, the weaker the intensity of theconvection. Also, the higher the thermal diffusivity ratio AR, thelower the distortion level of the temperature field.
URI: http://hdl.handle.net/11455/18296
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