| Summary: | 碩士 === 淡江大學 === 機械工程學系 === 85 === The present work is concerned with the numerical investigation
of gas flow in micro-channels with Knudsen numbers ranging from
0.02 to 0.16. The proposed model treats the flow as a continuum
but assumes a slip condition on the channel wall. The results of
the present study reveal some interesting features of micro-
channel flows. First, due to the extraordinarily small
dimensions, a large pressure is required to drive the flow.
Although the pressure gradient is large, the velocity remains
very small due to the high shear stress on the wall, in the
cases studied, the maximum u velocity is only 1.16 m/sec for a
pressure ratio of 2.701. Second, since the velocity is small,
the corresponding Reynolds number is also relatively small,
(0.012 - 0.089), for the flows simulated, they can be safely
assumed to be laminar. Third, the calculated pressure
distributions of nitrogen flows agree quite well with test data,
the Knudsen numbers of these flows, Kn = 0.055 at the channel
outlet which is the largest value in a channel, indicating
they are in the slip flow region. The calculated pressure
distribution of helium flow does not match test data, the
corresponding outlet Knudsen number is 0.160, indicating it is
in the transition flow region. Although more investigation
is needed before definite conclusions can be drawn, the results
of this study indicate that the slip model is able to predict
micro-channel flows in the slip flow region, but further study
is needed for flows in the transition flow region.
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