Re: CO2 reactor

Karl Schoeler wrote:
> Subject: Trapa natans, Ludwigia inclinata, and Egeria najas
> Ludwigia inclinata reminds me of washed out Rotala Macranda.

Hmmm... my various Ludwigia species all have relatively thicker
leaves than R. macranda except for L. arcuata which has small
leaves to begin with. As well, they all have an olive to brown
color (esp in strong light w. enough Fe) so I wonder if this
washed out appearance will continue if the plant grows under
optimum conditions? Does it have new growth and how does it 
look? Do the leaves have the characteristic pointed tips of
the other (amphibious) Ludwigia species? Perhaps we can work
out something so I can get a cutting or two across the Canadian

> Subject: CO2 tanks and fire extinguishers

CO2 and welding gas suppliers will not fill an uncertified
CO2 bottle (at least here in Canada and I presume in the US).
But then again, aren't CO2 extinguishers certified? You couldn't
modify the valves & adapters without re-certifying I expect.

KB Koh wrote:
> Subject: Re: Another CO2 Reactor Design
> Good idea Steve. However I think you'll need to refine it a bit. This 
> "meta-stable equilibrium point" is not highly desirable as CO2 from 
> yeast is not pure and these other gasses tend not to dissolve. They get 
> collected in the cone if this condition is reach. You'll need an outlet 
> for them somewhere along the cone.

Yes, that troubled me too. A small hole added close to the equilibrium
point would bleed off any excess accumulation without allowing many
stray bubbles to escape. I'd determine the location experimentally
since it would vary according to flow rate and the other dimensions
of the apparatus. Good reason to use a transparent material like PVC.

                                               <-- CO2
                                             ||    _______
                                 Venturi---->||   [-------]==]
                       /=================----++---/       | |]=+
    1/2" PVC tube---->/ . <-o  <-o  <-o  <-o              | |
                     / . ./==============---------\       | |
                     | o  |          Powerhead---->|      | |
  Max flow velocity--->|. |                        [______] |
  Small hole-------->;.V .\                             [ ]
                    /.O. O \<---- Inverted Cone Reactor [ ]
     Entrained     / ./.\ . \                           [_]
     CO2 bubbles--->O .. o . \
                 /.././. \.\ .\     .
                /  . o  .  o . \    .
 Diffuser vanes-->/ ./ . .\. \. \   .
              /./ ./. /.\.\ \..\.\  .
              .  .   . ||     \\  . .
  Flow direction------>||   .  \\<----Min flow velocity
             .   . .  \||/.  . \||/
               .  .  . \/  .  . \/

> From my experience, you should not shutoff the powerhead while the yeast 
> bottle is connected. Due to the venturi effect, the pressure in CO2 tube 
> is lower, turning off powerhead would initially let water get into the 
> tube before the CO2 pressure from the bottle building up again.

Yes I find the same thing too so after experimentation, I crack the
cap on the yeast bottle and then shut off the powerhead. However, it
also doesn't take much back pressure at the outlet of the powerhead
before you can get a positive pressure at the venturi relative to
ambient. Of course the pressure at the venturi is still lower than
the pressure at the outlet. The problem is with sufficient air bubbles
entrained in the water stream, there would be a significant difference
in hydraulic pressure inside and outside the top of diffuser. This is the
same effect that makes an UGF lift tube pump water when you bubble air
through it. The small bleeder hole will tend to equalize that pressure 
difference but there is a Bernoulli (venturi) effect here too. I can't be 
sure whether the pressure at the venturi will be positive or negative but
which ever will determine whether to shut off the pump first or crack
the yeast bottle cap seal. As well a bleeder hole would prevent an
accumulation of air which could airlock the powerhead pump.

Thank you for the design refinement KB.