Heat transfer of power-law fluids with variable thermal conductivity on a horizontal rough surface
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摘要: 根據泰勒展開式,推導了變熱導率的冪律流體沿水平波面上的邊界層方程.假設熱傳導系數是依賴于溫度梯度的冪律函數,構建了變熱導率的能量方程模型.引入一系列變換,將原始波面轉換為偏微分方程組,并用Keller-box方法進行數值求解.討論了某些參數如波幅與波長的比值、冪律指數以及廣義普朗特數對壁面摩擦和流體傳熱的影響. 壁面的摩擦系數和局部Nusselt數,在靠近零點的地方會有劇烈震蕩,沿軸向會呈現波形分布狀態,隨著波長比率的增大而減小,且會隨著振幅的增大,壁面摩擦系數也會震蕩加劇. 隨著冪率指數的增加,局部Nusselt數呈現遞減的分布狀態.
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關鍵詞:
Abstract: According to Taylor expansion, boundary layer equations for the power-law fluids with variable thermal conductivity along a horizontal wavy surface are reduced in detail.The energy equation with variable thermal conductivity is constructed, where heat conduction coefficient is power-law function dependent on temperature gradient. A series of transformations are introduced to transform the original wavy surface to a system of partial differential equations, which is solved numerically by the Keller-box method. The effects of the wavy amplitude-wavelength ratio, power-law indexand generalized Prandtl numberon the local friction coefficient and heat transfer coefficient are discussed. The local Nusselt number and the friction coefficient will vary like wave-shape periodically though there is a sudden change near the zero point. Furthermore, both of them will decrease with increasing wavelength ratio. With the increasing magnitude, the oscillation also will increase. With the increasing power-law index, the local Nusselt number will decrease. -

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