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How to model H2 flow through microchannels?

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Old   December 14, 2005, 19:34
Default How to model H2 flow through microchannels?
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Hi all, I want to model H2 flow through a microchannel. I am feeding the channel at 25 psi and exit is at atmospheric. There are several bends. I would like to model this flow. Should I use the Euler equation or the compressible Navier Stokes? Which one gives a better predictions? i calculated the velocity using an experiment measuing the volumetric flow rate, the average velocity seems to be 60 cm/s, which is well below the Ma number of 1320 m/s in hydrogen. thanks,

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Old   December 14, 2005, 21:58
Default Re: How to model H2 flow through microchannels?
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Maybe you can consider the DSMC method and you can get code from Bird`s book.
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Old   December 15, 2005, 10:11
Default Re: How to model H2 flow through microchannels?
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I don't know how small (or large) a microchannel is.

Do you have a continuum flow? Is the mean free path a sizable fraction of the diameter (width, height)?

The Knudsen number, K = mfp/dia, should be small (< 0.1) to use the continuum (Navier-Stokes) model.

This stuff is coming off the top of my head, and I'm sure folks with more experience will correct or refine as needed.
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Old   December 15, 2005, 12:47
Default Re: How to model H2 flow through microchannels?
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If your knudsen number is less than 10^-3 use a continuum model and if the knudsen number is in the range 10^-3 - 0.1 use a continuum model with slip boundary conditions

u_s=u_wall+du/dn)wall If Kn> 0.1 you can still consider slip flow model upto a Kn of 4-5 and beyond that use DSMC as mentioned by dusky.

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