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Gas sampling probe design.

  1. Jun 7, 2013 #1
    I want to sample exhaust gas just behind a Catalyst. The problem being the gas varies across the area of the brick so a normal sample probe could read high or low.

    The general idea is to use a tube with holes in across the area of the brick, however I'm not sure what size to make the holes as too large and most of the flow will come from the nearest edge of the brick. Presumably the holes will need to get larger the further you go along the tube. But what size to make the holes I'm not sure how to calculate.

    I know the length of the sample probe area ~150mm and the flow of the sampling machine. ~0.2g/s Also I know the inside diameter of the probe ~6mm
  2. jcsd
  3. Jun 7, 2013 #2


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    Why is there a brick in your car? :confused:
  4. Jun 7, 2013 #3
    By brick I mean catalyst substrate.

    This sketch might clarify things;


    As you can see in order to get even flow I need bigger holes the the further along the probe, but my question is...how big?
    Last edited by a moderator: May 6, 2017
  5. Jun 11, 2013 #4


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    I'm sure that I don't understand this subject enough to help, but it seems to me that the best solution would be to have a disk instead of a tube, which matches the surface area of the catalyst and has evenly spaced equal size holes like a shower head. Would that work for you?
  6. Jun 12, 2013 #5
    I don't know enough science/physics/math to answer, and would be shocked that there is a specific equation that some how eludes you.

    How expensive are "probes"? Can you make your own holes, can you use multiple probes with only one hole and pull statistical data instead? Your situation sounds unique enough that you need to invent the solution. Yay perspiration! :smile:
  7. Jun 17, 2013 #6
    This is one of the topics that I can hardly understand >.<
    Last edited: Jun 17, 2013
  8. Jun 17, 2013 #7
    Ah I see, well hope you get to "play" your way to a solution, back to my point about it maybe being to unique to merely calculate an answer.

    lol opps it's not even your thread/
  9. Jun 18, 2013 #8
    How about using a probe with one hole and traversing across the exhaust pipe taking a reading at each point.
  10. Jun 26, 2013 #9
    email me at droog57@gmail.com
    The company I work for occasionally sells Gas Analysis equipment, and no, I'm not planning or trying to sell you anything, our Gas Analysis stuff is mostly for nuclear and chemical plants and costs a LOT, but I CAN put you in touch with some knowledgeable people that could probably help. I would give contacts here, but that would not be fair to them.
    Last edited: Jun 26, 2013
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