本文應用微分轉換法模擬47 nm- Al2O3/water奈米流體的流動與熱傳現象，將奈米流體視為單相。此外，透過熱力學第二定律的角度，探討熱力系統中的不可逆性，藉由熵增最小化的概念分析奈米流體在熱流元件設計上能源利用的效率。本文主要研究垂直通道間考慮黏性耗散之混合對流，並探討在流場中加入磁場效應所造成的影響。
關於奈米流體在垂直通道間考慮黏性耗散之混合對流的熱傳表現與熵增，所模擬的混合對流無因次參數範圍為100≦Ξ≦500，而布林克曼數範圍為0.005≦Br≦0.08。在改變無因次參數的大小下，由模擬得到的結果顯示奈米流體在高溫壁面的局部紐賽數高於純水，且隨著濃度增加而提高。但在 較高時，奈米流體在低溫壁面的局部紐賽數反而小於純水。在熵增方面，奈米流體的平均熵增數小於純水。此外，發現使用不同奈米流體物性模型所得到的數值結果差異甚為明顯。
接著，探討在流場中加入磁場效應對奈米流體的熱傳表現與熵增造成的影響。在磁流體力學流(magnetohydrodynamic flow)的研究裡，必須在動量方程式中考慮勞侖茲力，而在流體能量方程式中考慮因電磁場引起的焦耳熱。本文所模擬的哈特曼數較低(Hm=2)，由模擬得到的結果顯示在磁場效應的影響下，奈米流體在高溫壁面的局部紐賽數提高，且隨著濃度增加而上升。然而在 較高時，奈米流體在低溫壁面的局部紐賽數反而變小，且隨著濃度增加而下降。在熵增方面，在流場中加入磁場效應則造成奈米流體的平均熵增數下降。

This thesis applies the differential transformation method (D.T.M) to simulate the flow and heat transfer features of 47 nm- Al2O3/water nanofluids using single-phase approach. Besides, it probes into the irreversibility of the thermodynamic system based on the second-law analysis, also using the concept of Entropy Generation Minimization (EGM) to investigate the energy efficiency of the designs of devices with nanofluids. This study mainly analyzes mixed convection flow in a parallel-plate vertical channel with viscous dissipation effects; moreover, investigates the influence of flow with magnetic fields.
For the thermal performance and entropy generation of nanofluids within a mixed convection flow with viscous dissipation effects in a vertical channel, the simulations are conducted at different mixed-convection dimensionless parameter (100≦Ξ≦500) and Brinkman number (0.005≦Br≦0.08). The results which are presented for various values of dimensionless parameters show the local Nusselt number at the hot wall with the use of nanofluids is higher than the use of water and increases with the raise of particle volume concentration. However, the local Nusselt number at the cool wall with the use of nanofluids is lower than the use of water when the Brinkman number is higher. When it comes to entropy generation, the average entropy generation number of nanofluids is lower than the average entropy generation number of water. Furthermore, using different models associated with the physical properties of a nanofluid reveals great deviations of computed results.
Further the influence on the thermal performance and entropy generation of nanofluids by the effect of magnetic fields is investigated. In the study of the magnetohydrodynamic (MHD) flow, the transverse momentum balance equation has to take into account the Lorentz force and the energy balance equation has to take into account Joule heating. Simulations are conducted at low Hartmann number(Hm=2). After the simulation, the results show that under the influence of magnetic fields, the local Nusselt number at the hot wall of nanofluids is higher and increases with the raise of particle volume concentration. However, the local Nusselt number at the cool wall of nanofluids is lower and decreases with the raise of particle volume concentration when Brinkman number is higher. When it comes to entropy generation, the average entropy generation number of nanofluids is lower with magnetic fields.

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