奈米流體通過多孔性介質方柱之熱流場分析

Analysis of Thermo-Fluid Flows of Nanofluids past a Porous Square Cylinder

鄭元誌(Yuan-Jhih Cheng)

指導教授 ： 朱存權

國立虎尾科技大學/工程學院/車輛工程系碩士班/碩士(2016年)

摘要

本研究利用計算流體力學方法為工具進行數值模擬，探討奈米流體通過多孔性方柱之二維暫態熱流場分析。在多孔性介質區域方程式採用暫態的Darcy-Brinkman-Forchheimer模式描述，進行連續方程式、動量方程式及能量方程式的求解。研究參數包括流體流入速度、奈米流體體積分率及多孔性介質的孔隙率、滲透率等，以瞭解各參數對奈米流體流經多孔性方柱的流場、溫度分布及升力係數、阻力係數之影響。研究結果顯示，在升力係數方面由模擬數據得知，隨奈米流體體積分率增加時，則升力係數的振幅變化將會增加。而阻力係數方面，則奈米流體體積分率增加時，阻力係數亦會隨之增加。但在本研究所探討參數範圍內，阻力係數相對於升力係數振幅值皆顯較小。有關對熱傳遞的探討，隨著奈米流體體積分率增加時，加熱面的平均紐塞數隨之增加，可增加散熱效益。綜合觀察，奈米流體體積分率及多孔性方柱孔隙的同時考量，對於流場與熱傳的影響基於存在兩者的互相作用關係，要達到改變流動、熱傳的目的，則必須兩者數值做適當的配合才得以達到預期效果。

關鍵字

奈米流體 ； 多孔性介質 ； 對流熱傳 ； 計算流體力學

並列摘要

In this study, the use of computational fluid dynamics method explores a 2-dimension transient thermo-fluid flow fields of nanofluids past a porous square cylinder. Continuity equation, momentum equation and energy equation were solved based on the porous area described by Darcy-Brinkman-Forchheimer model.The physical parameters studied include inlet velocity, nanofluid volume fraction and porosity and permeability of porous media to understand their effects on the flow fields, temperature distributions and lift coefficient, drag coefficient. Results show that as the fluid fraction increases, the amplitude of lift coefficient increases also. In terms of drag coefficient result, the drag coefficient increases with the increase of nanofluid volume fraction. Compared with lift coefficient amplitude, the drag coefficient values are relatively small in the ranges of parameters studied in here. In observing the heat transfer results, the averaged Nusselt numbers on the heating surface present an increase trend as the increase of nanofluid volume fraction. It means the nanofluid can enhance heat transfer rate. Involving nanofluid and porous medium both factors in a study, where the interaction of both factors exists, both factors should be properly adjusted to improve the flow field and heat transfer efficiency.

並列關鍵字

Nanofluid ； Porous media ； convective heat transfer ； Computational fluid dynamics

參考文獻

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