Experimental investigation of diluted gas flowing through microchannels with square structures

• Main Authors: Shih-Pao Yang, 楊士葆
• Other Authors: Yu-Hsuan Su
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/72943461331406544864

碩士 === 國立臺灣科技大學 === 機械工程系 === 103 === 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.