本研究以數值模擬之方式，來探討在強制對流條件下，固定加熱面積，奈米流體流經不同高寬比微流道熱沉孔對其熱傳特性（流道壁面溫度、熱通量、紐賽數）之影響，採用的奈米流體為 與純水之混合物。本研究主要控制的數值模擬參數為體積濃度及高寬比。目的在找出散熱效益較佳之微流道幾何尺寸。
數值模擬結果顯示，在相同之流道尺寸下，以奈米流體取代純水，由於熱傳導係數之上升，可降低流道前段流道壁面之溫度，造成更多之熱量傳至流體，並增強熱對流效應。但同時會造成黏滯力上升，導致流道壓降相較於純水，會呈現上升的情況。
在固定流道寬度，改變不同高寬比之流道尺寸下，當增加高寬比時，由於改善流道截面積縮減程度，因而使得流道壓降下降，質量流率增加，並有效地降低流道壁面與加熱面之最大溫度，如此使得整體熱阻值下降，提高散熱效益。
最後，當流道個數、流道寬度、高寬比增加時，將使質量流率增加，流體可帶走更多的熱量並有效地降低整體熱阻值。

In this study, under forced convection and with fixed heating area, the heat transfer characteristics (channel temperature, heat flux, and Nusselt number) for nano-fluids with different concentrations used in different aspect ratios micro-channel heat sink are investigated. The examined nanofluid is and the control variables for numerical simulation are volume concentration and aspect ratio. The goal of this study is to find the optimal size of micro-channel heat sink with the best heat transfer performance.
The results show that in the same channel size, nanofluids which have higher thermal conductivity than water can reduce the channel wall temperature near the inlet, increase the heat flux to fluid, and enhance convection. However, the increase of volume concentration will also raise the viscous force and cause larger pressure drop.
With fixed channel width, to increase the channel aspect ratios can improve the effect of channel contraction and result in the decrease in pressure drop, the increase in mass flow rate, and the effective decrease in channel wall temperature and maximum temperature of heated surface as well. The overall thermal resistance will therefore decrease and better cooling performance can be achieved.
In addition, the mass flow rate will increase with the increasing of the number of channel, channel width, and aspect ratio. Fluids can carry more heat and the overall thermal resistance will therefore pronouncedly decrease.

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