臺灣博碩士論文加值系統

本文以非達西( Non-Darcy)效應, 考慮對流項, 邊界效應項, 慣性效應
項, 可變孔隙率及熱逸散效應項(Thermal dispersion)對兩垂直平板間充
滿多孔性介質之穩態混合對流從進口區( Entrance region)到完全發展
區 (Fully developed region)為本文所要討論之範圍. 所用之參數包含
葛雷斯荷夫數 Gr (Grashof number) , 普朗特數 Pr (Prandtl number),
顆粒直徑比值 γ = d/H ( Dimensionless particle diameter) 及熱傳
導比值 λ=kf/ks( Thermal conductivity ratio) 為流體之熱傳導係數
與多孔性介質之固體部份的熱傳導係數的比. 至於數值方法則採用三次樣
線定制法 ( Cubic spline collocation methed) .結果顯示, 由於加入
非達西效應之變孔隙率和熱逸散效應的關係, 使的流場在近壁面處之速度
場與沒有考慮變孔隙率及熱逸散效應之速度場有明顯的差別. 但是近壁面
區乃熱傳中相當重要的區域, 所以在熱傳上也有很大的差異. 隨著葛雷斯
荷夫數 (Gr) , 普朗特數 (Pr) , 顆粒直徑比值 (γ) 增加, 則局部熱
傳係數遞增. 流體之熱傳導係數與多孔性介質之固體部份的熱傳導係數的
比 (λ) 增加, 則局部熱傳係數遞增. 變化顆粒直徑比值時, 顆粒直徑比
值越大在壁面處之局部最大速度由進口區到完全發展區有較大之變化幅
度, 而在流場為完全發展流時, 顆粒直徑比值越大則由變孔隙散率所產生
之渠道效應越不明顯.

Non-Darcian effects, including convection, boundary, inertia
, variable porosity and thermal dispersion effects, on
mixed in a vertical channel filled with porous media are
examined from the entrance region to fully developed
region. the governing parameters to be discussed
inclue the grashof number Gr, Prandtl number Pr,
dimensionless particle diameterγ = d/H, and thermal
conductivity ratio of the fluid to the solid of the
porous matrix λ = kf/ks. The coupled nonlinear partial
diffrerential equation are solved by the cubic spline
collocation method. Numerical results indicate that the
local heat transfer rate increases as the Grashof
number Gr, Prandtl number Pr and dimensionless
particle diameter γ increase. When the conductivity
ratio of fluid to the solid of the porous matrix
increases λ , the local heat transfer increase. For
fully developed flow, as the dimensionless particle
diameter increases the wall channelling effect result
from the variable porosity decreasee.