This is a recommendable post @Hanuman
, as usual your great building skills and well documented. I admit, too often when I work on my tank I consider how @Hanuman
would do it
We’ve seen so many posts on many variation of bubble reactors in the past 20-30 years or so, I guess in the thousands, and yours is probably not the last. It’s not that dissolving CO2 in water is so difficult, or that it is a real technical challenge…
I think it’s probably bad forum etiquette to use your post only to promote an alternative, so I’ll make sure that I give some detailed replies on your post, even though I would never again consider building or optimising a bubble reactor. With lots of data and arguments I have had limited success gaining traction for the Horizontal Reactor on this forum, so it is probably foolish to expect that more scientific arguments and calculations will make any change … so YESSSS that’s exactly what I’ll do
Let’s start with a thought experiment. We take your bubble reactor, turn it 90 degrees into a horizontal position. This is then a Horizontal CO2 Reactor
, no bubbles anymore - will that make things better or worse?
So let's do some simplified estimations, not exact science but just enough to get a feeling and a sense why Horizontal CO2 Reactor works.
View attachment 205743
When the reactor is horizontal, upper half filled with CO2 and lower half with a flow of water, the surface area for CO2 absorption is 25.806 mm2. If we assume for a moment, if we're to have a vertical reactor, that our bubbles are 3 mm diameter, each bubble represents a 28 mm2 surface area for CO2 absorption to the water. So we calculate that we would need 913 bubbles to get to the same CO2 absorbing area as the horizontal reactor would do. When I took slow motion videos of my bubble reactor, it did not even come close to this number, as anyone may confirm in their reactors.
The objection to this simplified calculation may be that in reality we do not have all same size 3 mm bubbles, but some smaller and some bigger. If we would redo the above calculations, we find:
So for any mix if above bubbles sizes (if we feel that that’s closer to reality), we would need many hundreds of bubbles – much more than we can observe in our real life reactors. Therefore it is safe to assume that for any given pipe size, the horizontal reactor variant packs much more punch than the vertical bubble variant. I won’t duplicate the other advantages of this simplified reactor method, they can be found in the thread, but will mention some below.
Please do not take my remarks as addressed to you personally, because indeed you do not claim you ‘own’ the ideas from what you have posted, and just post your implementation for the benefit of others.
Copying your reactor makes sense for a similar size tank, water flow from pump, etcetera. I have never seen posts on any forum that prescribes what are the correct dimensions for any bubble reactor, as a function of the user’s setup This is probably also not possible, as there are too many unpredictable variables at play in a bubble reactor, so that it is really hard to make a reliable model for its operation and performance. The horizontal reactor is much simpler to understand and model, and that’s why I’ve posted an estimation how to calculate the correct dimensions for any tank size.
When we focus on what we want to achieve (no noise, 100% efficiency, no bubbles in tank), and follow the Optimisation procedure that I used in my AquaMedic reactor, we see why in my personal view a by pass is highly desirable.
I would personally never build a reactor without by pass, because you miss the optimization option and you get either bubbles escaping or noise if and when CO2 / water flows are not matched.
You said it
CO2 pressure will be at equilibrium with local water pressure, and therefore always very close to atmospheric pressure.
CO2 build up in the chamber is the main cause of water splashing and making noise. I would slowly increase the water flow at any given CO2 injection, using bypass valve, until this CO2 pocket disappears and the reactor is perfectly silent. If it appears that we then have bubbles escaping from the bottom, we learn that we have exceeded that maximum reactor capacity and it is better to reduce CO2 flow.
You are correct that a CO2 pocket in the top of the reactor also gives a reduction of flow in the system. It is worth mentioning (I did not before as I found the physics too confusing to mention) that the bubbles in a reactor will give a back pressure to the pump and reduce the flow to the tank. This is the same physics as airlift pump, and also explained in the youtube that I attach below. The Horizontal Reactor will not give any backpressure, as there are no bubbles pushing water against the flow and no CO2 pocket where we could create a noisy and energy wasting waterfall.
I believe the Niloc reactor is the best commercially available, but pricey, but still some room for improvement IMO, especially in the top where I worry a bit about noise.
For a Horizontal CO2 Reactor any plastic pipe from the local plumbing store will be good, transparent is just nice to have, as there is really no need to observe what’s going on inside.
I modified my AquaMedic reactor so that I could have automatic purging of any trapped air. I am mean enough to leave that as a little innovation puzzle, and am happy to share my solution in a PM
Horizontal CO2 Reactor also purges itself of trapped air, the valve is just an optional nice to have.
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Youtube videos to illustrate physics of backpressure in bubble reactor: