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Diffusion rate

  1. Apr 1, 2009 #1


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    I have a long, 24" diameter verticle pipe. There is a flow of gas through this pipe in which pure helium enters at the top and exits at the bottom where it exits to atmosphere. In this case, there must be a gradient of gasses with helium at the top and air at the bottom and a mixture between the two due to diffusion.

    My question is, what flow of helium is needed to keep this gradient constant? In other words, I want to maintain pure helium at some upper point in the pipe - so how can I determine the flow of helium needed to keep the air out?

    I know it has to do with Fick's law but I've never had to do a calculation like this one. Any thoughts?
  2. jcsd
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