當流道的尺寸縮小且在相同的大氣環境下時, Knudsen number 將相對增加, 使得傳統的無滑移條件及理論分析不再適用, 造成流動進入滑移流動, 進而需討論流場中滑移流動行為, 並藉由巨觀的現象及微觀的行為來描述流場的流動變化。微流道通常是藉由微機電製程所製造的, 而表面粗糙度卻是影響切線動量係數的重要參數之一, 並研究氣體於其內所產生的滑移流現象, 但是若是在不同的表面粗糙度下, 必定會產生不同的結果, 但是表面粗糙度是在製程的過程當中必然會產生的結果, 故我們利用微機電製程在微流道內建構不同高度的柱子( 1μm, 2 μm and 3 μm), 使得主要的柱子是經由人為所控制的, 隨後再使用經過重新設計以避免漏電流產生的陽極鍵結系統對微流道晶片進行氣密封裝, 以利後續量測實驗的進行。本實驗所使用的為雙槽累積量測系統, 所量測的壓差對時間的變化, 即可求出質量流率。
本實驗結果顯示, 流道中柱子在高度為1μm的情形之下, 儘管面積變化, 但其單位質量並不隨紐森數改變, 代表TMAC 受到柱子影響改變, 其中氦氣因為受到局部紐森數1.6影響, 導致其動量交換不足, 使得TMAC 參數比空白流道來的低, 並且其質量流率受到面積減少影響其減少幅度不會正比於面積減少的量, 會略高於面積比; 當柱子高度越高, 面積越來越小結果導致單位質量流率隨著紐森數改變, 在紐森數其越小時越接近連體行為, 流道中柱子在高度為2μm的情形之下, 單位質量流率比略接近面積比; 流道中柱子在高度為3μm的情形之下質量流率減少幅度大於面積縮減的量。當紐森數越大時後會形成一定值, 其會與流道面積比有關。在相同出口紐森數, 當壓縮比越低其平均紐森數提高, 動量交換不完全使得質量傳輸現象越大, 導致單位質量流率會提高。

With rarefaction the flow behavior deviate from traditional Navior-Stokes
equations with no-slip boundary condition. In place of slip boundary with Navior-Stokes equation, it is used to calculate a flow under somewhat and moderately dilute conditions. Maxwellian slip conditions are applied which in turn refer to the tangential momentum accommodation coefficient (TMAC). The tangential momentum accommodation coefficient is affected by such as surface roughness and gas properties. In that the mechanisms of TMAC is not authentically certain, it intrigues us to investigate profoundly the flow in microchannels.
In this work, microchannels existing some artificial square(10 μm × 10 μm)
structures with height 1μm, 2 μm and 3 μm pretending surface roughness were
also constructed and hermetically sealed by the anodic bonding technology. The mass flow rate was measured by the dual-tank accumulation system,where the rate is related to time rate of differential pressure variation between two fixed volume tanks.
The results found that helium flow into microchannel existing square with 1μm
height decreases the TMAC because of large local Knudsen number. The mass
flow rate decrease slightly that compared to the microchannel without structures due to insufficient collision of molecular. Also, mass flow rate in channel existing square with 2 μm and 3 μm height is extremely affected by shrinking area while with increase of Knudsen number the normalized mass flow rate will enlarge because of insufficient molecular collision. At the same output Knudsen number and different compressibility, mass flow rate will influence by local pressure. Low compressibility decreases the possibility of molecular collision resulting enlarged normalized mass flow rate.

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