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Internal reactor pressure & bubbles per sec

Discussion in 'General Plant Topics' started by growitnow, Feb 14, 2010.

  1. growitnow

    growitnow Lifetime Charter Member
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    Hello,

    90gallon tank, with AM1000 reactor, SUMO Premier regulator with bubble counter. AM1000 reactor shell is clear and this reactor has a long CO2 output tube inside the reactor, so you can see and count CO2 bubbles being released into the reactor itself. I am setting up reactor and have never used one before.

    I see there is a big difference in the bps when counting bubbles in the bubble counter, versus, counting bps released into the reactor itself. This is what is puzzling me. Below is my observation of bubble rate at the bubble counter versus at the reactor.

    Test 1 (attempting to get about 2 bps at bubble counter):
    113 bpm (1.9 bps) in bubble counter = 60 bpm (1 bps) actually released into reactor
    outcome = drop checker stays blue

    Test 2 (after adjusting bubble rate to get about 2 bps released into reactor):
    165bpm (2.75 bps) in bubble counter = 112 bpm (1.9 bps) actually released into reactor
    outcome = drop checker now turns green

    Test 3:
    without changing bubble rate, I then turned off pump to reactor
    outcome = 165bpm (2.75 bps) in bubble counter = 165 bpm actually released into reactor

    There is a BIG loss of bps when counted at the reactor compared to bps at bubble counter. This could be due to CO2 leak, or because internal reactor pressure limits CO2 release into the reactor. Or something else?

    So, a few questions:

    1) Is this "loss of bubbles" at the reactor compared to at the bubble counter normal, or do I have a problem?
    (strangely, the difference in actual [HASHTAG]#bubbles[/HASHTAG] in each test1 and test2 = 53 bubbles)

    2) If the difference was due to internal reactor pressure when the pump is on, wouldn't CO2 gas pressure equalize the difference? (so that bps at bubble counter should be 'pretty close' to bps actually released into reactor)

    3) If the difference was due to a CO2 leak, that leak should still be present with the pump shut off, yet there is NO bubble loss at the reactor when the pump is shut off. So how can it be a leak?

    Any observations, experience, or suggestions would be appreciated. What do I do next?
    Thanks!


    fyi - I have 2 check valves on the CO2 line; a brass one near the regulator, and a plastic Dennerle near the reactor. At present, the CO2 bleed line is closed (will recycle later, right now trying to figure this out)
     
  2. nipat

    nipat Guru Class Expert

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    Hi,

    I'm not sure.

    By common sense it should. But is the bubble size in the reactor the same as the one
    in the bubble counter when the pump is on? The current in the reactor might cause
    bigger bubble by prolonging time before a bubble detaches from the tube
    (sounds strange though, it's just a guess:p).

    When the pump is off there might be not enough pressure to make a leak.
     
    #2 nipat, Feb 14, 2010
    Last edited by a moderator: Feb 14, 2010
  3. Left C

    Left C Lifetime Members
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    As mentioned above, the bubble sizes can be different between all the various types of CO2 equipment that release them in a liquid. Let's look at two different sizes of bubbles and their volume.

    The volume of the bubble varies by the cube of its diameter. This means that a small change in the bubble's diameter makes a large change in the volume of the bubble. Let's calculate this difference.

    This is the formula for the volume of sphere: (4 ÷ 3) ¶ (d ÷ 2) ^3.

    Let's calculate the volume of two CO2 bubbles. We’ll use 3 mm and 6 mm for the diameter of the CO2 bubbles for this example. These are realistic examples that we may actually see. Then ¶ = 3.14.

    3 mm diameter bubble
    (4 ÷ 3) ¶ (d ÷ 2) ^3
    = (4 ÷ 3) x 3.14 x (1.5 mm x 1.5 mm x 1.5 mm)
    = 14.13 cubic millimeters

    6 mm diameter bubble
    (4 ÷ 3) ¶ (d ÷ 2) ^3
    = (4 ÷ 3) x 3.14 x (3 mm x 3 mm x 3 mm)
    = 113.04 cubic millimeters


    Then 113.04 cubic millimeters ÷ 14.13 cubic millimeters = 8 times

    This means that when the bubble’s diameter is twice as large, the volume increases by 8 times.
     
  4. shoggoth43

    shoggoth43 Lifetime Charter Member
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    Take a look at the tubing going to the reactor. What is it made out of? Silicone tubing will supposedly lose 6% CO2 per foot.

    I'm guessing that if you got it from SuMo then you got tubing from them, which should eliminate that possibility. The other likely culprit is the difference in diameters. If you look in the reactor you probably used 1/8" clear airline/tubing. The bubble counter has a smaller opening going into the unit. That fact alone will require more bubbles per second in the bubble counter compared to the reactor.

    Also note that the reactor is a turbulent environment which may cause some odd behavior. CO2 is not really going to diffuse at all in the bubble counter since it should already be saturated, but it start doing this the moment it hits the tank water in the reactor. WAG ---> Given this, it's possible a portion of your bubbles never even survives long enough to show up as a larger bubble (
     
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