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Re: [APD] Re: Bubbles? -- or - Some hard topics not adding up!
You know, I think I just need a refresher geometry class, UGH! Volume
isn't increasing by 2Pi :-( The circumference does! I'll do some quick
math. r is the old radius, R is the new radius (R=2r). So, if
v=Pi*r^2, and R=2r, then dv=Pi*4! HAH, that means a 1.5" pipe has
~12.57 times more volume then a 0.75" pipe of the same length. Now I'm
really starting to think this thing will work ;-) Man, someone stop me
if I'm wrong!
-Dave T. (mumbling to himself, 'a^2+b^2=c^2, garblegarblegarble')
On 2/4/2004, "David Terrell" <Dave at terrellclan_com> wrote:
>Cool, two things:
>1: I said a 3/4" nylon tube to a 1.5" PVC was a 2x growth in volume,
>that's just false. Just a 2x growth in diameter, and thus a 2xPi growth
>in volume, being more then 6 times growth! For a second I was going to
>try to figure out the flow rate through the tubes and PVC, but it's been
>too long and I'll definately miss something, but I would almost want to
>assume 1/6'th water flow rate (velocity) through the reactor then the
>nylon tube to achieve the same result of 500g/hr. There's no way for me
>to even begin guessing at how fast it really is, how much pressure is
>exerted on a bubble of size X, and the resulting direction of said
>bubble :-( I'll just have to find out tonight when I get to fiddle some
>2: I agree, the tap _should_ be acting as a venturi, why it doesn't?
>Your guess is as good as mine. It's a flat pipe. I'll just move it and
>stop asking questions. Originally I used it on an earlier reactor
>design in which the flow was desired. As you can imagine, the reactor I
>built had far too small flow rate and esentially did nothing :-( The
>good 'ol stickin it near the impeller did well, until I became
>disatisfied with my CO2 ppm and usage.
>Ok, three points ;-) My tank continues to produce bubbles, interestingly
>my money wort is producing some on the bottom side of the leaves thus I
>suspect O2 production. Some stem plants that had a trim recently are
>still showing damag and shoving off small streams of bubbles, looks like
>a stream in a beer/soda bottle! Out of curiosity I think I'll do some
>readings tonight to find out what made them so happy.
>Four, you say? Ok ;-) I took a reading recently of GH in my tank. To
>my surprise and fear, it read 30! I thought it couldn't be right and
>redid the test, yet again it was 30! 'Uh oh' I thought, as I quickly
>went to the tap to test source water...2 degrees! WOW, what in the H*LL
>could be causing my GH to rise so sharply? KH, btw, was 2 and pH 7. I
>have laterite substrate, 'normal' freshwater aquatic plants, 2-3mm
>gravel and the wet/dry setup I showed earlier in the thread. I dose
>text book pmdd 2-3x/wk and don't use any sort of buffers...think I could
>*knock knock* on my water soon!
>On 2/4/2004, "S. Hieber" <shieber at yahoo_com> wrote:
>>Stab # 3 at the first question:
>>If there are no other devices inbetween the irrigatin tap
>>and the reactor, the pressure should be the same at the
>>current location and at the reactor.
>>If the tap extends into a length of the water tube/pipe
>>coming off the pump utput, and is *not* angled (even
>>slightly) so that it is pointed towards the water flow,
>>then it should act more like a venturi and tend to suck gas
>>in from the CO2 tube rather than push water up the CO2
>>tube. If you can't get a venturi effect, close off the tap
>>and move the CO2 connection to the reactor where the
>>increase in the water line diameter should reduce the water
>>line pressure relative to the CO2 line pressure.
>>If you increase the CO2 out put pressure, that should
>>prevent water going up the CO2 line. The water pressure is
>>likely not very high; few aquarium pumps develop more than
>>a few psi unless you have the output constricted (for
>>example with a ball valve) and the CO2 is between the
>>constriction and the pump. Even constricted, most aquarium
>>pumps develop only a few psi.
>>Question # 2:
>>The bubbles *will* trap and tend to collect at the top but
>>only up to point. The water will flow through the CO2 at
>>the top of the reactor and down and out the reactor. If the
>>water flow is too strong, then it might carry out small CO2
>>bubbles with it -- in which case put the reactor on a
>>Teed-off line from the main line so that it gets a lower
>>flow or use a larger diameter reactor.
>>If the water flow is too low or the CO2 rate too high, the
>>CO2 will collect in the reactor faster than it can be
>>absorbed, eventually filling the reactor with gas and
>>leaking out the bottom opening of the reactor, which is a
>>waste. In that case, increase the water flow or decrease
>>the CO2 output. If decreasing the CO2 doesn't yield a high
>>enough CO2 level in the aquarium water or a higher flow
>>blows out CO2 bubbles, then use a larger diameter reactor
>>to support the higher water flow.
>>You might need to go back and forth a bit to get a useful
>>balance, but the set shouldn't be very sensitive to the
>>amount of water flow and you'll be able to control CO2
>>levels by adjusting the CO2 flow rate. If the set up is
>>very sensitive to the water flow rate, and you have to keep
>>fidling with the CO2 rate and water flow rate to get a
>>stable reactor and CO2 levels, then use a larger diameter
>>NOte that these suggestions are "IF/thens". I think you
>>can probably get where you want to go with the reactor you
>>have, inverted so water enters the top, with a few
>>adjustments to flow rates.
>>2 examples on hand:
>>I have a 3" x about 12" reactor on a 1/2" water line
>>flowing about 200 gph. That can maintain 15-30 ppm in a 150
>>I have a 2" reactor, about 12" on 3/8" water line flowing
>>about 50 gph -- that works on a 30g. It might even work on
>>the 150g, with higher flow rates but I never tried it.
>>--- David Terrell <Dave at terrellclan_com> wrote:
>>> Actually, let me rephrase to clear this up, this being
>>> the third time
>>> someone misunderstood my problem I guess it was just
>>> clearer in my head.
>>> The airline from my CO2 tank comes out of the needle
>>> valve, through a
>>> check valve then down the line to the intake for the
>>> reactor (but not
>>> _at_ the reactor). Now, I didn't drill a hole in the
>>> specifically for the airline. I had an irrigation tap in
>>> the output
>>> line from the pump (nylon return tube). I put the
>>> airline on that
>>> tap...so when the pump is on water is forced up the
>>> airline. There is a
>>> check valve after the needle valve (you can see it on the
>>> left in the
>>> reactor picture) so I wasn't nervous about it returning
>>> to the tank and
>>> causing problems. However, it seems I won't get a
>>> regular flow when the
>>> airline has to build pressure to go back to the pump
>>> The question is/was: How can I reduce the backpressure
>>> of water on the
>>> airline from the pump return to the CO2 tank?
>>> My next question is, if I turn over the flow through the
>>> reactor (so it's
>>> closer to the proper design ;-) are the bubbles really
>>> going to flow
>>> upwards/trap? I have a 750g/hr. pump, rated at this head
>>> it flows
>>> ~500g/hr. I don't know fluid dynamics so this is a big
>>> problem! The
>>> pump return is a 3/4" nylon tub that goes to some
>>> adapting fittings of
>>> PVC pipe, which eventually reaches 1-1/2" PVC, so a 2x
>>> growth in volume.
>>> Will the flow be slow enough to allow the bubbles to
>>> rise/trap in the
>>> ractor chamber?
>>- - - - - - - -
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>>Nov 2004 -- Baltimore
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