磁性奈米流體於背向階梯渠道內對流熱傳之研究

Study on the convective heat transfer of magnetic nanofluids in a backward-facing step channel

陳冠良(Kuan-Liang Chen)

指導教授 ： 翁輝竹

中原大學/工學院/機械工程研究所/碩士(2020年)

https://doi.org/10.6840/cycu202000565

摘要

本論文完成磁性奈米流體在背向階梯渠道內熱流場及其特性之分析。主要目的在探討水基磁性奈米流體的粒子濃度、外部感應場強度，以及不同的壁面熱邊界條件對背向階梯渠道內對流熱傳之影響。首先，在數值模型驗證上，我們透過再接觸點位置、平均努塞爾數及網格獨立性測試之研究結果，確保了數值模型的可靠度與精確度。接著，我們分析了磁性奈米流體之物理材料性質，然後透過ANSYS-Fluent分析軟體中應用連續、動量及能量守恆方程式，結合邊界條件的設定，進行背向階梯渠道內對流熱傳之分析。
研究結果發現，在無外部感應場強度、固定雷諾數Re=400及相同熱通量的條件下，平均努賽爾數僅增強約0.4%。然而，在外部磁場強度探討中，當我們在粒子濃度φ=3.2%，考慮Re=100、200、300及400等四種不同雷諾數條件下，施加一外部感應場強度30 mT時，相較純水之流體，最大增強率分別為9%、11.7%、12%及11.5%。

關鍵字

磁性奈米流體 ； 背向階梯 ； 流體動力學 ； 對流熱傳

並列摘要

This thesis conducts an analysis of the thermal flow fields and their corresponding characteristics of the magnetic nanofluids in a backward-facing step channel. The main purpose is to investigate the effects of particle concentration and external magnetic induction strength as well as different wall thermal boundary conditions on convective heat transfer of water-based magnetic nanofluids in a backward-facing step channel under different Reynolds numbers. First, in the verification of the numerical model, we have ensured the reliability and accuracy of the numerical model through the research results of reattachment point position, the average Nusselt number, and the grid independence test. Next, we analyzed the physical material properties of the magnetic nanofluid, and then applied the continuity, momentum, and energy conservation equations through the setting of material property parameters in ANSYS-Fluent combined with the setting of the boundary conditions to analyze the convective heat transfer in a backward-facing step channel.
The results of the study showed that under the conditions of no external induction field strength, a fixed Reynolds number of 400 (Re=400), and the same heat flux, the average Nusselt number is only increased by about 0.4%. In the discussion of the external magnetic field strength, when an external induction field strength of 30 mT is applied under the particle conditions φ of 3.2%, and the Reynolds numbers of 100,200,300 and 400, the maximum enhancement rate can reach about 9%,11.7%,12%, and 11.5%, respectively, compared with the fluid of pure water.

並列關鍵字

Magnetic nanofluids ； Backward-facing step ； CFD ； Convective heat transfer

參考文獻

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