热科学学报（英文版）2009，Vol.18Issue(4)：353-357,5.DOI:10.1007/s11630-009-0353-5
The Entrance Effect on Gases Flow Characteristics in Micro-tube
The Entrance Effect on Gases Flow Characteristics in Micro-tube
摘要
Abstract
Entrance region may have important effect on gases flow characteristics in micro-channels. It's concluded in the available papers that the entrance effect causes significant difference. An experimental system of single-phase gas flow characteristics in microchannels was set up. Flow characteristics of nitrogen in PEEK polymer micro-tube (hydraulic diameter is 5531am) was studied experimentally. According to the data of nitrogen flow in the mi-cro-tube with the length ranging from 0.1m tol.524m, it is shown that the friction constant becomes higher when the tube becomes shorter. By using pipe cutting methods, it's confirmed that entrance effect is one of the key fac-tors that cause friction constant higher than conventional theory. It's found that friction constant of fully devel-oped flow is lower than the value predicted by conventional theory in turbulent region. The result indicates that the flow transition occurs at Reynolds number ranging from 1600-2000. The phenomenon of obvious early transi-tion is not found.关键词
microchannel/ the length of entrance region/ entrance effect/ constant friction/ method of cutting tubeKey words
microchannel/ the length of entrance region/ entrance effect/ constant friction/ method of cutting tube分类
数理科学引用本文复制引用
Chengwen Li,Li Jia,Tiantian Zhang..The Entrance Effect on Gases Flow Characteristics in Micro-tube[J].热科学学报（英文版）,2009,18(4):353-357,5.基金项目
This investigation is supported by the National Natural Science Foundation of China (No.50776006),"863"plan (No.2006AA05Z228),and Technological Innovation Fund of Excellent Doctoral Candidate of Beijing Jiaotong University (No.48013). （No.50776006）
