Flow rate to fast?

[scottward]

I have a feeling that the flow rate through my AM1000 might be slightly too fast. As I have slightly upped the bubble rate, there are bubbles coming out of the return.

This question obviously isn't specific to an AM1000, it could also apply to any of the DIY external reactors as well.

I do have it set up in 'dual venturi' mode, but the bubbles coming out of the reurn aren't the chopped up mist style bubbles.

I was thinking that perhaps an easy way to solve this would be if I shut down the venturi loop? The extra backpressure created might be what I need to slow down the water flow enough to keep the CO2 in the reactor?

My bubble rate is only about 10 - 12 bps at the moment, and I think I will eventually need to crank it up even more.

My tank is 100 gallons.

Scott.

 

[jonny_ftm]

How can you count 10-12 bps ??? Or you mean bpm?

Maybe try shutting down the venturi and see.

 

[scottward]

If I concentrate on the 'rythymn' of the bubbles, I can count about 10 bubbles per second, but any faster and it really becomes too fast.

Try it....you can *just* count to 10 in the space of 1 second, just watch the second hand on a clock.

Scott.

 

[Tom Barr]

Try taking the AM100 apart and splitting the bubble tube into 2 or more so you cut the rate by 1/2, simply add a Tee at the end.

I think much over 5-8 bps is the capacity.
I use 2 AM 1000's on a 350 Gal, they have trouble keeping up.


Regards,
Tom Barr

 

[scottward]

Hi Tom,

I don't quite understand how splitting the CO2 'straw' inside the reactor would help... it would still be the same amount of CO2 going in, and wouldn't a single stream of larger bubbles help?

The manufacturer states that this unit is good for up to 500 gallons; my tank is only 100 gallons so the unit should *easily* be able to provide CO2 levels for a tank this size, and at typical bubble rates.

Have I been 'had', or is it simply a flow-rate issue?

I have taps on the return from the AM1000. If I close off these taps this will have an effect on the flow rate; would this be ok? I have a dedicated circulation powerhead in my tank, so, closing the taps slightly shouldn't have a significant affect on water circulation given the seperate powerhead for this.

Scott.

 

[scottward]

Yeah, I'm thinking, even if I only put 1 bubble per second through the unit, if the water flow through it was too fast, that bubble would end up coming out the return line too. If I then proceed to add more bubbles per second to it, this of course just means more bubbles coming out the return line.

Conversely, if the water flow is too slow, the incoming gas won't be dissolved at a high enough rate and the gas will then start to build up at the top of the reactor (if I did not have the dual venturi modification in place).

I guess the 'optimal' water flow rate through such a unit is the fastest rate whereby a single bubble cannot be physically pushed through the unit.

Once this phsicaly limitation is met, increasing the bubble rate should have very little to do with the amount of gas that comes through the return line; rather, it would have everything to do with how much gas builds up at the top.

The rate that the gas dissolves would also then be in relation to, I guess, water temperature? So, in summer when the water is warmer, I would expect to see more gas building up at the top of the reactor as the solubility of the gas is lower in the warmer water.

Ok, so let me try to summarise that with an example, and let's say I can 'throttle' the flow rate through the AM1000 (or other external reactor):
- I turn on the water flow and select a 'mid-range' flow rate.
- I feed in a single bubble per second flow rate and observe
- If the bubbles are, after being chopped up a bit of couse, being forced down and out the return line, this means the water flow is too fast - back it off a bit.
- If the bubbles are not coming out the return line, increase the flow rate until they are, and then back off a bit
- So, at this point, the bubble rate is just slow enough to keep the bubbles in the reactor; any increase in the flow rate and the bubbles will start escaping out the return line.
- If I now continously, but gradually, increase the bubble rate, I would expect that eventually the gas will start to build up at the top of the reactor.
- How much gas builds up in the top of the reactor will now be based on the solubility of the gas given the water temperature (and maybe some other water related solubility factors).
- This built up gas can of course be burped out using the dual-venturi method, which would mist the bubbles back into the unit and these would understandly, given their very low buyoncy, make it out the return line (that's the idea of course).

So, even if the bubble rate was 200bps, I still shouldn't see any bubbles coming out the return line if the flow rate isn't execessive - just a lot of gas build up in the top of the reactor? Correct?

Just trying to understand this - it wasn't cheap, so I need to make sure I know how to work it properly! ;-)

Scott.

 

[scottward]

That should read:

So, at this point, the *flow* rate is just slow enough to keep the bubbles in the reactor