本研究的目的是以實驗的方法探討微噴流流場結構，以及熱晶片上之微噴流衝擊冷卻〈impingement cooling〉熱傳行為分析，並分別與理論值及巨觀下的情形作比較。粗糙面的製作是利用TMAH對矽之非等向性濕蝕刻加工方式製作，對矽基材蝕刻出高度150μm以及兩種不同肋節距。有關於粗糙面上微衝擊冷卻方面的資料也是相當少的，所以粗操面的製作是替接下來一系列的實驗預先作準備。
　　實驗是以雷諾數(Reynold number)介於16～640之間的自然噴流，衝擊光滑熱晶片，平板至噴嘴距離Z/B介於4～1600之間。吾人以熱晶片上的溫度感測器量測停滯點(stagnation point)及側向下游的溫度分布，並以此來計算局部的熱傳係數，吾人將探討其中之熱傳變化，以及微噴嘴衝擊在熱晶片上的熱傳特性。在流場結構量測方面，則以熱線測速儀，針對其不同的下游位置分別量測中心流速分佈、側向流速分佈以及紊流強度分佈的情形。
　　實驗結果發現微噴流在剪流層不穩定性的擾動太小而無足夠能量生成大尺度渦流結構，並且其層流結構的邊界層上產生相當大的速度梯度，這樣的速度梯度並未消耗噴流的動能，反倒是這些動能集中在噴流中心，使得中心的流速都來的比相似解的估算都要來的大。此外，在微噴流衝擊冷卻方面，發現其停滯點之最高熱傳係數值會受出口雷諾數的影響呈現反比的關係，且產生在壁面與噴嘴出口距離為數百倍至數十倍噴嘴寬度的位置。經研究發現該位置與微噴流之崩潰點位置相近，並且經由統計回歸分析所得的關係式為(Z/B)max = 24209/Re，其中L為紊流崩潰長度。最後，本研究藉由無因次參數(Re、X/B、Z/B及L/B)的引入，很成功的將停滯點、局部點及平均熱傳係數建立經驗關係式，可供微機電系統或CPU散熱設計的參考。

　　Experiments are performed to study the structure of a free micro-jet flow and micro-jet impingement cooling heat transfer over a thermal chip. In the current work, the thermal chip made was flat. The rib-roughened thermal chip was also made by etching the Si(100) wafer with TMAH. However, due to limitation of current thesis, the impingement cooling experiments over a rib-roughened wall were not made, but are ready for further studies.
　　For the micro-jet impingement cooling experiments, the local Nussult numbers distribution along the thermal chip were measured for the Reynolds number varying from 16 to 640, and the nozzle-to-spacings ratio from 4 to 1600. In addition, different size of nozzles, i.e. 50μm, 100μm, 200μm were used to assure different structures of micro-jet impinging on the wall. The effect of micro-jet impingement cooling study different width of nozzles. It is found that the location for the occurrence of maximum stagnation point Nusselt number decreases with increasing Reynolds number. This is attributed to the decrease of the breakdown length of the micro jet. The maximum stagnation point Nusselt number is expected to occur at the location where jet breaks down. A correlation of the location for the maximum stagnation point Nusselt number in terms of Reynolds numbers can be obtained as (Z/B)max = 24209/Re.
　　For the free micro-jet flow experiments, both flow visualization and velocity distribution measurements using hot wire anemometer were made. There are no coherence structures of vortex formation in the shear layer as appeared in the large-scale jet. It appears that even with large gradient of velocity in the shear layer, the most unstable wave in the shear layer is too weak to have enough energy to roll up into ring vortices for the micro-scale jet. However, the micro-jet has more enough energy in direction of centerline. So, the centerline velocity of micro-jet are highly more then similarity solution.
　　An attempt was first made to correlate the stagnation point Nusselt number in terms of relevant nondimensional parameters such as the Reynolds number and Z/B. This is done by first normalizing Z/B by dividing Z/B with L/B, i.e. Z/L. The correlation results show that all the stagnation point Nusselt numbers at the same Reynolds number can collapse approximately into a single curve, and these correlations are very successful. Similar kinds of correlations have also been obtained for both the average Nusselt number and the local Nusselt number.

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