Swedish DIY venturi

[defdac]

Peter Haack made these nice DIY venturis by heating plexi and PVC-tubing:
http://www.haack.se/venturi.html

This one is very stylish =)
http://www.haack.se/PICT0699.JPG-for-web-LARGE.jpg

I'm anxious to see how they will perform..

[VaughnH]

Should the CO2 be introduced at the throat, just before the throat, in the straight section before the throat, or does it matter? For that matter, I still don't see the theory behind why a venturi results in microbubbles of CO2. But, this is certainly a simple, elegant way to make a venturi, and a venturi that should not result in much of a head loss.

[Tom Barr]

Here's how a venturi works:

Venturi effect - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Venturi)

Regards,
Tom Barr

[Professor Myers]

A proper venturi is not as simple as a tapered pipe. There is a disproportionate difference in the angle of the taper IE: 90* input taper to 47* output to create a pressure differential to fascilitate the vacuum . This is merely an example as the taper is dependent on volume, and pressure.

Like wise there will also be a difference in the gas intake for Low pressure systems (Powerheads). IE: a quarter inch air intake might benefit from a .036" orifice on the leading edge of the air intake to compensate for lower static head pressure.

I'll provide a more specific example as time permits as I'm presently experimenting between proto-types designed specifically for use with powerheads, and Co2 induction. HTH. Prof M

For the record: The Mazzei Injectors are definitely worth the price, but are designed for high pressure sytems. Given their efficiency they still work splendidly for powerheads. Just not as well. A simple modification to the gas intake throat makes quite a difference, Though the machining is somewhat tedious.

[Tom Barr]

The smaller the sizing of the orifice entering the pressure differential will help.

This is due to volume of air vs the volume of CO2 we are adding.
For our applicastions, we are not adding air and lots of it, just a small amount of CO2.

We need a smaller pipe and higher pressure than most venturis. you can modify the orifice effectively using those rigid 3/16" OD tubing they sell at the LFS's.

Using heat/lighter etc, you can taper the tip so that only a tiny opening is present.

This will release smaller bubbles.

The other idea is to place a mister in the venturi lead in and have a loop that feeds water through the venturi section.

Not sure how to describe it yet.
Better make a drawing and post that.

Regards,
Tom Barr

[Professor Myers]

Yes the induction of Co2 as opposed to air is an entirely different matter as well. 1/4 " line is fine all the way up to the last orifice into the venturi. It allows you to offset the .036 opening to the leading edge. This increases the velocity of the gas flow when using power heads at a 150 to 180 gph flow rate. A very small augmentation to the gas flow produces a much finer mist, and allows you to maintain what precious little flow you have ( The flow rate is perfect for the reactor, but has a low static pressure as it relates to venturi performance).

I use this intake in a recombinant fashion to purge the reactor. Your original design was more than adequate for most systems. The short comings were always in the powerheads themselves. A longer reactor tube can handle the increased flow rate, but the escaping mist is actually a perk in my book. Now if you modify an internal duct within the reactor tube (Mixing Condenser) you can compress the stream for a more efficient exchange of gas, but it's really a mute point as the reactor is quite efficient already. Not many people push more than 180 bpm. :eek:

Venturi injection for Co2 is not really tricky, but it's considerably different than o2 or o3, and freshwater doesn't enjoy the same luxury of density as saltwater. Prof M

Your method of tapering the 3/16" pipette is much simpler I just have to figure out how to orient it within the venturi orifice ? A proud edge to the orifice would increase the vacumm energy !

[VaughnH]

Here's how a venturi works:

Venturi effect - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Venturi)

Regards,
Tom Barr
From the Wikipedia reference: "A venturi can also be used to mix a fluid with air. If a pump forces the fluid through a tube connected to a system consisting of a venturi to increase the water speed (the diameter decreases), a short piece of tube with a small hole in it, and last a venturi that decreases speed (so the pipe gets wider again), air will be sucked in through the small hole because of changes in pressure. At the end of the system, a mixture of fluid and air will appear."
Or, to paraphrase: A venturi works to mix fluid with air by working to mix fluid with air. That isn't an answer. My question is why does a venturi produce microbubbles of CO2 which is introduced where in the venturi? I know very well how a venturi is designed and how it works as a venturi, having designed several many years ago to measure flow rates of both air and water, but I don' t know why it works to make microbubbles of CO2, and not knowing why it works, means I have no idea how to make it work better or best or well enough, etc. In principle, the lower pressure at the venturi throat should result in big bubbles at that point, which become smaller bubbles when the pressure goes back up in the downstream part of the venturi. But, that wouldn't by itself produce micro bubbles. In fact if you introduced milimeter size bubbles in the approach pipiing to the venturi, the bubble size in the outlet tube from the venturi should be almost exactly the same, because the static pressure will be almost the same.

[VaughnH]

A proper venturi is not as simple as a tapered pipe. There is a disproportionate difference in the angle of the taper IE: 90* input taper to 47* output to create a pressure differential to fascilitate the vacuum . This is merely an example as the taper is dependent on volume, and pressure.

Like wise there will also be a difference in the gas intake for Low pressure systems (Powerheads). IE: a quarter inch air intake might benefit from a .036" orifice on the leading edge of the air intake to compensate for lower static head pressure.

I'll provide a more specific example as time permits as I'm presently experimenting between proto-types designed specifically for use with powerheads, and Co2 induction. HTH. Prof M

For the record: The Mazzei Injectors are definitely worth the price, but are designed for high pressure sytems. Given their efficiency they still work splendidly for powerheads. Just not as well. A simple modification to the gas intake throat makes quite a difference, Though the machining is somewhat tedious.

If you are using a venturi to measure a flow rate, and callibration is very difficult, then and only then is it critical to optimize the inlet and outlet forms for the venturi. That lets you use theory to determine the flow rate versus the pressure change from inlet to throat of the venturi. But, for any other use, a simple smooth transitiion from the inlet diameter to the throat diameter is just fine, and the exit transition from the throat to the outlet diameter only needs to be gradual enough to avoid flow separation, which would result in a big pressure drop across the whole venturi. So, for our purposes - to produce CO2 mist - all we need is a simple venturi with a smooth transition at both ends to and from the throat to avoid pressure losses.

But, how that produces CO2 mist remains a mystery to me.

[Professor Myers]

The Transition of the tapers are in fact critical to the performance. (Compressing, Drafting, Swirling and Re-expanding ) Either will provide a venturi Affect, but one will provide better (Sustained) performance. Due to the difference in the density of Co2 a smaller gas orifice is desirable, and this smaller mist is swirled into the impeller where it in turn cavitates to corrupt even smaller bubbles.

I'd be happy to provide a working model, and you can study it, and reduce your impression to an intellectual prose that suits your own taste. :rolleyes: Never the less it does work rather impressively. You designed flow models. I designed injectors. Did you want to calculate the flow or inject a gas ? :D

Here's a link to a splendid design.

Mazzei Injector Corp. - How a Mazzei Injector Works (http://www.mazzei.net/injector_info.htm)

The only augmentation necessary for our purposes is to decrease and offset the orifice to adapt it to Co2. Basically machining or fabicating a drop in port to increase the intake velocity of heavy gas.

Venturi injection is mainly attractive for maintenance purposes, increased flow, and faster saturation.

Mi Dos Centavos, Prof M

[Tom Barr]

As the gas is sucked into the vacuum of pressure differential, it is torn into smaller gas "apherons", their size are determined namely by the volume of gas being fed into the venturi through a small orifice and then the flow rips it further and prevents coalescing.

Think about tube of toothpaste and you cutting off pieces of the paste at a fast or slow rate.

The faster the rate it comes out, the larger the pieces.
The faster you cut, the smaller the pieces.

The slower the rate the gas comes out, the better the chopping the venturi effect will have.

Unlike the disc and other means to diffuse gas, this has positive pressure.
Addign gas to the suction side of a pump will also chop the larger bubbles veryb effectively, see the needle wheel skimmer from RedSea, they sell the pump and impeller as well, 15$ for the impeller, 70$ or something to powerhead.impeller together.

I'd like to see if I cannot use the impeller in other brands of power head.
That would chop the gas up well, then, recirculate it through a venturi.

An in line design can be done effectively.
I think I already have a veryu effective sump and in line Reactor design, but I'd like to focus on a venturi design that does not use a reactor tube at all.

Regards,
Tom Barr

[Professor Myers]

Seriously ??? I was playing with a venturi design using a mixing condenser prior to the reactor, and it relegated the reactor to a fairly useless state (Pretty much eliminated it) There was a slight affluent of micro bubbles, but not nearly enough to justify the reactor tube. IMHO just enough to compliment the plants.

The design required significant pressure. So I'm back tracking to the gas injection port to better accomodate Co2 at a lower flow rate suitable for powerhead applications.

It was easy to build an industrial model. The trick will be in accomodating lower head pressure suitable for smaller aquariums. Every design I've seen no matter how efficient has a feeble venturi, and the port was designed for O2. Drafting the intake prior to the impeller is only half right. Your diagram (90* Shear to the intake, and description of the tapered tubing is well on the right track, but a few accomodations for a proper venturi, and swirl might add 30 or 40% increase in volume, and saturation. I'll be sure and post plenty of diagrams right away so someone can relable it for production ! ;) LOL.

[VaughnH]

As the gas is sucked into the vacuum of pressure differential, it is torn into smaller gas "apherons", their size are determined namely by the volume of gas being fed into the venturi through a small orifice and then the flow rips it further and prevents coalescing.


Regards,
Tom Barr

I think my brain is finally wrapping itself around this better! It is the high speed of the water through the venturi throat that make it work so well? The rapidly flowing water rips the little CO2 bubbles apart as they squeeze out thru the orifice? That makes a lot of sense. Then as the flow slows downstream, the pressure rises, which shrinks the bubbles even more? If I have it right, the best location to inject the CO2 would be the venturi throat, where the velocity of the water is the highest. And the smaller the inlet orifice for the CO2, the smaller the entering CO2 bubble , making the shredded bubble the smallest.

Thanks for stimulating my mind with this!! Now I can visualize ways to use this effectively.

[Professor Myers]

Got It ! Using the tapered pipette the inlet doesn't have to be offset. I just have to decrease the diameter of the opposing pressure well to the same diameter of the pipette, and keep the inlett slightly proud of the throat.

The use of the needle wheel impeller is even better, producing a much finer cavitation, and the ceramic bearings are a huge perk !

For a 1/2" flow the mixing chamber should be appx. 4 " long. Maybe 5" tops.

If the swirling veins are in the venturi, and the affluent is compressed. The reactor is eliminated...:D

[Tom Barr]

But even with a reactor, there is a pressure drop like with this, it's just smaller and easier to make.

A nice venturi would be a good CO2 device though, it would get the disc out of the tank and do the same type of thing.

Reactors are designed to get the CO2 100% dissolved, disc sort of do that unless you blast the bubbles around.

Why have a disc and a filter doing this when a venturi in line with the filter can?

Regards,
Tom Barr

[Professor Myers]

For the time being I eliminated the tapered pipette, and am using capillary tubes to modify the gas intake. This allows me precise metering of the gas, and permits me to adjust the height of the leading edge within the throat to increase or decrease shear pressure across the intake. ;)

[Tom Barr]

Cap tubes can be used very simply, but be careful, such fine micro tubing can break if too much gas is added.
Regards,
Tom Barr

[Professor Myers]

I had to cut these to length with a 400,000 rpm disc ! :D Tweren't EZ !!! LOL. ;) But now they're "Custom Parts" :p

FTR they're sheethed by a 1/8" polypropylene bulkhead.

[peterhaack]

Any Pics of your project?:)

[Professor Myers]

Any Pics of your project?:)

None yet Peter, I'm working with multiple formats at the moment. It's unlikely I'd post pics to the web just yet, but I have a few friends in Sweden capable of the fabrication. Where are you at in Sweden ?

I can try to translate to Swedish if you like. It may not help with the description, but it's sure to provide some comedy relief ! :D

If you can tell me the diameter of the tubing I can calculate the tapers for you. Grtz. Prof M

[peterhaack]

If you mean my tubes i did ?

well the diameter inside of tube
1. is 21mm and in the middel(thin part of the tube) it 8mm

2. is 17mm and in the middel(thin part of the tube) is 6mm

Or you better translate in to swedish :D

Im located in the south part of sweden close to Malmoe.

[Professor Myers]

1. 55* input 15* output 7.9375 at the throat. 4.7625mm dia. X 1.5875 depth for the opposing pressure well, and 6.35 dia. on the gas intake. OOP !

1. 55* insatsen 15* produktionen 7.9375 på halsen. dia. X 1.5875 djup för den mitt emot tryck brunn , och dia. på det bensin intagen.

Metric ! WTH ? :gw

[peterhaack]

HAHA love the translation you are telling me to use Gasolin in the gas inlet haha..

well the diameter inside of tube
1. is 21mm and in the middel(thin part of the tube) it 8mm and the inlet for gas is a 6mmtubing with inside diameter on 4mm.

Lazy as i am i haven tested it yet but hmm maybe i should, ah well there comes another day tomorrow.


2. is 17mm and in the middel(thin part of the tube) is 6mm and same gas inlet.

Do you think that will work as a venturi and will it make small gasbubbles if it does maybe it will be a good ide to blow in to the reaktor, what do you think about that Proffesor M

[Professor Myers]

I guess any gas is as good as another ??? :p

My first impression was that your diameters were very Very Close ! The difference lies in controlling the tapers of the inlett, and output. This is nearly impossible to control by thermo forming pipe without a constricting mold to limit the expansion.

Secondly: For our purposes (Co2 Injection) we require a greater gas intake velocity, and a smaller orifice. The smooth transition of the stretched taper is actually an impediment. We require a sharp edge to the throat, and an increased pressure differential to chop up smaller bubbles of gas. (Carefully study the Mazzei Illustration) pay close attention to the offset diameter of the opposing pressure well. Mazzei Injector Corp. - How a Mazzei Injector Works (http://www.mazzei.net/injector_info.htm) This forces the stream to turn/cut across the intake port ripping the bubbles from the orifice. If the intake jet has a sharp proud edge it will punctuate the portion of gas more effectively, but there is a very fine point of adjustment before it actually impedes the flow, and decreases the liquid velocity. (This is why I used an 1/8 bulkhead to sleeve the capillary tube) it's threaded and has a nut on it to raise or lower the intake within the throat. I'm just lucky that it reinforced the tube or it likely would have burst as Tom pointed out ! ;^)

Combine this with a lower flow rate to sustain the reaction, and a significantly smaller volume of gas, and the task becomes a formidable challenge.

We can decrease and meter the gas intake, but we still require a significant shear force to tear the bubbles from the orifice.

The process is a vast contrast to O2 or O3 injection.

Last point of observation is that if you accomplish these goals a reactor is almost un-necessary. Tom's greater point being that we may not want to contain the reaction at all, but distribute the confluent to the tank creating a gaseous interface of Co2 through the micro bubbles, and the plants.

I've tested dissolved Co2 against misting, and those plants that enjoyed the introduction of Co2 micro bubbles thrived by comparrison. (Tom makes a Very Good Point) :cool:

So long as we are designing a more efficient diffusion we may as well finish the job, instead of resuscitating the aborted shortcomings of prior methods, and systems.

I DO understand that you're trying to refine a simple production process of fabrication, but don't lose sight of the larger picture. You may very well succeed, only to show up a day late, and a dollar short of the ultimate goal ! ;)

[peterhaack]

Well im not doing this thing to make moe, i did this thing becuse some were doing it so complicated with drilling and stuffing pipes with cement to drill exact holes, wich seems to have taken some time =O)

I did just take a simpel plastic tube and heated it up in the middel and the pulled voila 2min of hard work puh...and i did some diffrent sizes =O))

I did an experiment now in the evening and since we are using pressurerised gas( we really dont need the sucking) when the gas bobble came out it was sort of vaporised out of the venturii so they seem to work =O)) BUT when there were no bobble it was just shoting ......water =O)
If it will work in long term i dont know, but for 2min of work and some cheap plastic tubing it was easy.

[Professor Myers]

and I completly agree. It takes me 20 Min. to machine the parts from scratch, but given my hourly rate it's cheaper for me to source the Mazzei Injectors, and modify the gas intake. This becomes more critical for folks using yeast reactors, and only increases the efficiency of tanked gas. It also becomes increasingly important for low pressure "Powerhead" systems. Not everyone wants the expense of tanked Co2 or expensive pumps, and not everyone wants a reactor in their system. Yet the cost of an improved venturi is just slightly higher than a ceramic diffuser, and they have lower maintenance. Savvy ? ;)

Face it. Once you've shelled out for tanked gas a $25.00 injector becomes rather trivial bye comparrison. So If others can benefit from the same system without the expense, Good For Them ! :D

For the Record I'm retired. I don't make one red cent off of this The process has cost me time and money. That's why I won't post pics to the web. Many fine contributors of this forum have done that in the past only to have someone pirate the very design they provided the community for free. Put it into production, and sell it retail. The punch line gets even better when folks purchase the product, and come right back here for advice, only to gripe about a membership fee ??? Just Imagine The Irony ;^))))) BWAHhahahahhahahhahha.

[Sintei]

For those who wants to show off.. This is available in glass entirely!

VWR International (http://se.vwr.com/app/catalog/Product?article_number=181-9100)

[Professor Myers]

For those who wants to show off.. This is available in glass entirely!

VWR International (http://se.vwr.com/app/catalog/Product?article_number=181-9100)


Please let us know how it works out for Co2 injection in aquariums :D

[Sintei]

Sorry to say, but Im not going to test it right now. I just finished my external DIY-reactor and it works like a charm. ALGEA BE GONE! Since I used a "ADA style" diffusor (actually mine is better that ADA ;)) in it, it doubles as a misting device too, pumping out all the smallest bubbles straight to the tank. Leaving the bigger ones to dissolve inside the reactor.

[Professor Myers]

One of the advantages of the internet, and international forums is greater exposure to more markets, and technologies. The more the merrier ! We are in a position where many of the prevailing products have room for improvement. Sometimes you get lucky and arrive at a serendipitous blend that works out. Unfortunately that's the exception to the rule.

I'm looking for a simpler method of distribution that works for more people in general. The hobby shouldn't be limited to a privileged few, and Co2 is a key component to their continued success. Certain products are expensive, cumbersome, and maintenance prone. Human nature relegates those products to the weakest link in the chain. Grtz. Prof M ;)

[rusticitas]

I do so want to understand all of this... It seems fascinating. And a very interesting problem! Is there a Venturi 101 for Idiot Savants? ;-)

[Tom Barr]

Yes, do a google search on venturi gas injection.

In English:

Nice pics:

Venturi Injection vs Bubble Diffusers - venturi injection with ozone - bubble diffusers ozone (http://www.ozoneapplications.com/info/venturi_injection_vs_bubble_diffusers.htm)

Venturi effect - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Venturi_effect)

and

Mazzei Injector Corp. - How a Mazzei Injector Works (http://www.mazzei.net/injector_info.htm)

The good thing about them: no decrease in efficiency/no cleaning, this is not true for glass diffusers etc! They need cleaned and sit inside the tank(Except for the Cal labs model).

No moving parts, high flow and positive suction(no back pressure).
the other good thing, they reduce flow, but not very much compared to many other in line devices.

They are small.

Regards,
Tom Barr

[Dusko]

I am not sure really is there a need for inventing something that already exists, and can be bought here in Sweden for only 60 Swedish crowns. I use the Eheim Venturi diffuser and it works like a charm.

Here is the trick I use in my Juwel 180 liter tank;
http://www.imagestation.com/picture/sraid225/pfae3a8731dfca5500be8c839e47b0397/e9ca80b1.jpg

http://www.imagestation.com/picture/sraid225/pce5ebe242248264fc94545b032b61408/e9ca80c0.jpg


Hi peterhaack, I live in Malmo too. I work at Zoo Giganten (fiskavdelning). You can always drop by for a friendly pint :D

Kind regards, Dusko.

[Martin]

Tell me.

is this venturi design made so you attach it to your filter as with reactors etc.?

or is mi supposed to be connected to a powerhead?

[Dusko]

You should connect it to the powerheads out let, so water can jet into the Venturi.

Regards, Dusko.

[Anti-Pjerrot]

Sintei - i did the same thing with my glassdiffuser and my DIY reactor - works better than anything i evet tried (+10 diffent diffusers):

http://i44.photobucket.com/albums/f45/Anti-Pjerrot/PICT0112.jpg

I recomment anyone having a simple reaktor to try this method. I never seen pealing like this before...

[Tom Barr]

CAL Labs makes something like this out of glass, works very well for smaller systems like 160gph or less with no head flow loss.

Here's a link:

CAL AQUA LABS - CO2 Glassware (http://www.calaqualabs.com/Inline_diffusers.html)

Note, this method is based on the CO2 mist theory and these products and several DIY designs all came from the original hypothesis I proposed.

But many still do not believe the affect is real.
Rather than belief, I used an O2 meter, it's real alright, the details still need work and test, but the basics: does it work and does it make things easier to grow?

Definitely.

You may also use the CO2 mist method to determine if a particular species of plant is CO2 limited or not in the tank.

Simply blast the CO2 mist directly on the plant from a distance where the mist gently bathes/covers the plant with CO2 mist.

That, plus non limiting nutrients, you can generally grow anything and then vary the light as the independent variable.

Greg Fisk also did a similar thing as Anti P about a year ago after wondering about adding a venturi.

This disc approach is great for smaller systems IME and removes all the glass disc out of the tank where it gets covered by algae and also is just more stuff in the tank.

I bet we will see ADA make something like this later.

Regards,
Tom Barr


Regards,
Tom Barr

[Martin]

Sorry to say, but Im not going to test it right now. I just finished my external DIY-reactor and it works like a charm. ALGEA BE GONE! Since I used a "ADA style" diffusor (actually mine is better that ADA ;)) in it, it doubles as a misting device too, pumping out all the smallest bubbles straight to the tank. Leaving the bigger ones to dissolve inside the reactor.

Sintei, what's the point with the filter balls? The CO2 should be pushed down out of the reactor by the waterflow? or do the CO2 mist rise into the balls?

[Professor Myers]

CAL Labs makes something like this out of glass, works very well for smaller systems like 160gph or less with no head flow loss.

Here's a link:

CAL AQUA LABS - CO2 Glassware (http://www.calaqualabs.com/Inline_diffusers.html)

Note, this method is based on the CO2 mist theory and these products and several DIY designs all came from the original hypothesis I proposed.

But many still do not believe the affect is real.
Rather than belief, I used an O2 meter, it's real alright, the details still need work and test, but the basics: does it work and does it make things easier to grow?

Definitely.

You may also use the CO2 mist method to determine if a particular species of plant is CO2 limited or not in the tank.

Simply blast the CO2 mist directly on the plant from a distance where the mist gently bathes/covers the plant with CO2 mist.

That, plus non limiting nutrients, you can generally grow anything and then vary the light as the independent variable.

Greg Fisk also did a similar thing as Anti P about a year ago after wondering about adding a venturi.

This disc approach is great for smaller systems IME and removes all the glass disc out of the tank where it gets covered by algae and also is just more stuff in the tank.

I bet we will see ADA make something like this later.

Regards,
Tom Barr


Regards,
Tom Barr

The CAL inline diffusers are sweet little units, but we can't have alot of glassware lying about in this house W/ the Creamsicle Puma. :( That Crazy B@$tridge has got Racoon eyes when it comes to sparklies ! :eek: Bummer !

[peterhaack]

I am not sure really is there a need for inventing something that already exists, and can be bought here in Sweden for only 60 Swedish crowns. I use the Eheim Venturi diffuser and it works like a charm.

Here is the trick I use in my Juwel 180 liter tank;
http://www.imagestation.com/picture/sraid225/pfae3a8731dfca5500be8c839e47b0397/e9ca80b1.jpg

http://www.imagestation.com/picture/sraid225/pce5ebe242248264fc94545b032b61408/e9ca80c0.jpg


Hi peterhaack, I live in Malmo too. I work at Zoo Giganten (fiskavdelning). You can always drop by for a friendly pint :D

Kind regards, Dusko.

The thing with the homemade venturi was more that someone took alot of money to make em and all i did vas takinga asimpel piping and som heat made one in like hardly 1min and then a small drill di attach the pipng for gasthe rest its up to the pump you connct it til..

The diffusier you are using Dusko i used when i started with Yeast CO2 4 years ago and they work like a charm...

I dont live in malmoe but in a small town called Skanes Fagerhult so its a bit of road to get to you..

Love your tanks Dusko

/P