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Proceedings of Symposium on Energy Engineering in the 21st Century (SEE2000) Volume I-IV

ISBN Print: 1-56700-132-7



A new tube-cutting method that was proven feasible by experimental results is adapted to measure the pressure and Mach number distribution along a microtube. Experiments and computation were also performed concerning the average Fanning friction factor of five microtubes with diameter ranging from 80.0 to 166.6 µm. It is found that the pressure distribution in a microtube became nonlinear at higher Mach number and the product of measured average Fanning friction factor Cfa and the Reynolds number Re is higher than 16 predicted by Moody chart for laminar flow. Numerical results show that the gas compressibility leads to a variation of the velocity profile, which results in a larger velocity gradient at the tube inner wall surface and consequently a larger friction coefficient. The transition from laminar to turbulence in microtubes occurs at Re ~ 2300, which is consistent with the results in macro tubes.
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