tinygiants
New member
Here is where I found the refference to Escobal and 13%.
http://www.hawkfish.org/snailman/skimmer101.htm
http://www.hawkfish.org/snailman/skimmer101.htm
5' Skimmer Build in Progress
- Thread starter tinygiants
- Start date
crazzyreefer
New member
the 13% rule is a proven theory of bubble conjoining, it is past this point that the air bubbles join one another to make larger bubbles, thus negating the fact that a fine or ultra fine stone is being used, now what is interesting the ones at aquatico say that a 50% ratio can be received if your using ultra fine stones, it goes against the rule, but rules may change due to the size and more importantly the rise rate of a bubble, the rise rate is the velocity, and I believe at higher velocities bubbles can merge easier, but this is my thinking, not published, escobales work is flawed, it is a work based on others, but without merit in all rules. some are correct, others are partially correct others are false. know the difference of a published work being correct and incorrect even though it was published... the world is not flat!
BeanAnimal
Premium Member
The problem with the ultrafine stones is the force required to drive them. Any gains in skimming efficiency will be negated by the size and cost of the pump required to drive them.
25 PSI is A LOT of pressure, as the stones are designed for connection to bottled gas and a regulator. A scuba tank holds about 80 cubic feet of air. So at 1 CFM it would drive the skimmer for about 80 minutes.
A typical 6 CFM @ 90 psi piston hobby compressor runs about $350. These have a 50% or less duty cycle rating. The compressor would likely exceed it's duty cycle faily quickly. It would cycle every 5-7 minutes to boost the tank from 90 back to 135 psi.
A 6 CFM 75% duty cycle rated unit would need to be purchased. Your looking at $600 or more.
The ultra fine diffusors will also clog rather quickly.
Tank size does not really matter in this scenario. A large tank spreads out cycle to make the on times longer as well as the off times. A small tank cycles on and off faster, but in the end does the same amount of work.
This brings us to blowers. There are rotary vane blowers that will provide 1.5 cfm at 25 PSI. You will spend $3000 or so on one and it will be as loud or louder than the piston compressor.
In a nutshell, there is no way to use the ultra fine stones for a skimmer unless you have more money that you know what to do with.
Bean
25 PSI is A LOT of pressure, as the stones are designed for connection to bottled gas and a regulator. A scuba tank holds about 80 cubic feet of air. So at 1 CFM it would drive the skimmer for about 80 minutes.
A typical 6 CFM @ 90 psi piston hobby compressor runs about $350. These have a 50% or less duty cycle rating. The compressor would likely exceed it's duty cycle faily quickly. It would cycle every 5-7 minutes to boost the tank from 90 back to 135 psi.
A 6 CFM 75% duty cycle rated unit would need to be purchased. Your looking at $600 or more.
The ultra fine diffusors will also clog rather quickly.
Tank size does not really matter in this scenario. A large tank spreads out cycle to make the on times longer as well as the off times. A small tank cycles on and off faster, but in the end does the same amount of work.
This brings us to blowers. There are rotary vane blowers that will provide 1.5 cfm at 25 PSI. You will spend $3000 or so on one and it will be as loud or louder than the piston compressor.
In a nutshell, there is no way to use the ultra fine stones for a skimmer unless you have more money that you know what to do with.
Bean
What I meant was that Escobal didn't reference the 13%, meaning he didn't say what source he used. In any case the percentage would be different depending on the nature of the air-water interface. This depends largely on the constituents that are in the air and water, and how much time has passed. In certain scenarios, bubbles can touch and not coalesce. Not only is this hard to quantify for our systems, but it changes with time. If it didn't, then we wouldn't be removing anything....
Found this with google: http://www.quickpure.com/
I emailed them yesterday but haven't had a response yet.
Any thoughts on the cone-shaped skimmer theory I had? It would make sense if bubbles could be made fine enough, but there wasn't enough output per stone area....
Who was it again that was using the super fine diffusers? Cheers,
G1
Found this with google: http://www.quickpure.com/
I emailed them yesterday but haven't had a response yet.
Any thoughts on the cone-shaped skimmer theory I had? It would make sense if bubbles could be made fine enough, but there wasn't enough output per stone area....
Who was it again that was using the super fine diffusers? Cheers,
G1
Here is a thougt from the past. Most skimming knowledge comes from waste water treatment. But other uses of gas bubbles for filtering materials is quite commom. In the aluminum industry, it is common practice to bubble gas through molten aluminum to remove entrapped particulate and gases. Bubble size and contact time were the prime measures of effectivness. The most efficent design I have seen was a spinning disk with a vertical shaft. Gas was forced down the shaft and exited at the center of the disk. The outside of the disk was shaped like a cog wheel and as the large bubbles tried to rise around the disk, they were sheared to very fine bubbles that then floated up through the metal and removed the impurities.
Might a spinning disk give the bubble size the skimmmer needs? You can adjust the bubble size by the tooth size in the disk and the RPM you spin it at. It would also be self cleaning and would have a long life as there is nothing to plug. You will need a motor to turn the shaft though.
I don't have time right now to experiment, but would be glad to help if others want to try this idea.
Might a spinning disk give the bubble size the skimmmer needs? You can adjust the bubble size by the tooth size in the disk and the RPM you spin it at. It would also be self cleaning and would have a long life as there is nothing to plug. You will need a motor to turn the shaft though.
I don't have time right now to experiment, but would be glad to help if others want to try this idea.
I just received the reply. 12x12'' diffuser is $100. Custom sizes are availlable, but the setup fee is very high. Other than that, they didn't answer my other questions. I'll post when I get this info, regarding bubble size at 60'' in artificial seawater. Oh yeah, recommended flow is 0.5SCFM, with a maximum of 2SCFM. Here is part of the pdf they sent me:
6. Maintain 3 psi at diffuser surface for 2 - 3 minutes. CAUTION : NEVER EXCEED 4 PSI
(111 INCHES OF WATER) DIFFUSER SURFACE PRESSURE DROP.
7. Adjust flow as required to between 0 and 2 SCFM. Recommended flow is 0.5 SCFM (30
SCFH or 14 L/Min.) or less.
Diffuser surface pressure drop is also known as Dynamic Wet Pressure (DWP)
DWP = SP - dPsub - dP0x - dPline
Where ;
SP = Air or oxygen supply pressure in inches of water ( psi x 27.68 = inches H2O ).
dPsub = Diffuser water depth in inches (top of diffuser to water surface).
dP0x = Orifice pressure drop in inches H2O from table enclosed.
dPline = Pressure drop between pressure gauge and diffuser orifice due to pipe line frictional loss
in inches of water.
For example: If the diffuser is 50 inches below the water surface, the orifice pressure drop is 5
inches of water, and the pressure drop in the line is 2 inches, then the gas supply pressure should
never exceed 111 +57 or 168 inches (6.1 PSI).
G1
6. Maintain 3 psi at diffuser surface for 2 - 3 minutes. CAUTION : NEVER EXCEED 4 PSI
(111 INCHES OF WATER) DIFFUSER SURFACE PRESSURE DROP.
7. Adjust flow as required to between 0 and 2 SCFM. Recommended flow is 0.5 SCFM (30
SCFH or 14 L/Min.) or less.
Diffuser surface pressure drop is also known as Dynamic Wet Pressure (DWP)
DWP = SP - dPsub - dP0x - dPline
Where ;
SP = Air or oxygen supply pressure in inches of water ( psi x 27.68 = inches H2O ).
dPsub = Diffuser water depth in inches (top of diffuser to water surface).
dP0x = Orifice pressure drop in inches H2O from table enclosed.
dPline = Pressure drop between pressure gauge and diffuser orifice due to pipe line frictional loss
in inches of water.
For example: If the diffuser is 50 inches below the water surface, the orifice pressure drop is 5
inches of water, and the pressure drop in the line is 2 inches, then the gas supply pressure should
never exceed 111 +57 or 168 inches (6.1 PSI).
G1
BeanAnimal
Premium Member
In essence that is what a needlewheel is.
In the context of putting it inside the skimmer body...What prevents a vortex from being created in the body? (don't know if this is good or bad)
Secondly, such a setup is a bit more complicated than it first appears. The disc would have to be sealed to the shaft to prevent the air from leaking around it. This requires a bearing of some sort that is reef safe and yet has a low friction coeficient. The next problem is sealing a high rpm shaft to motor connection. This brings us to mag drive. The mag drive motor would need to be at the bottom of the skimmer, so this causes us a headache in removing water without bubbles.
It is likely doable... but would take a lot of thought and innovation.
Bean
In the context of putting it inside the skimmer body...What prevents a vortex from being created in the body? (don't know if this is good or bad)
Secondly, such a setup is a bit more complicated than it first appears. The disc would have to be sealed to the shaft to prevent the air from leaking around it. This requires a bearing of some sort that is reef safe and yet has a low friction coeficient. The next problem is sealing a high rpm shaft to motor connection. This brings us to mag drive. The mag drive motor would need to be at the bottom of the skimmer, so this causes us a headache in removing water without bubbles.
It is likely doable... but would take a lot of thought and innovation.
Bean
Not quite the same thing, as it doesn't pump any liquid. Just shears big bubbles into little bubbles. The air flow rate is adjustable, the gear tooth spacing is adjustable, and the rpms are adjustable, all to provide a given bubble size.
On a needle wheel, the pumps impeller does shear bubbles. It also pumps water and doesn't do both as well as it could be done in my opinion.
On a needle wheel, the pumps impeller does shear bubbles. It also pumps water and doesn't do both as well as it could be done in my opinion.
BeanAnimal
Premium Member
How about a group order of custom diffusors for a 6" skimmer body, say a 5" dia 1" thick.
This would give 17 sq/in inches on top, 17 sq/in on bottom and about 15 sq/in around the edge for a total effective area of about 48 sq in.
I typical 3x1 stone has 14 sq in, with only 3 of that on top and 8 on the sides. So to get 48 inches of area you would need about 3.5 of them. This would equate to about 11 sq/in on top 25 or so on the sides, with another 11 on the bottom.
Thoughts?
This would give
This would give 17 sq/in inches on top, 17 sq/in on bottom and about 15 sq/in around the edge for a total effective area of about 48 sq in.
I typical 3x1 stone has 14 sq in, with only 3 of that on top and 8 on the sides. So to get 48 inches of area you would need about 3.5 of them. This would equate to about 11 sq/in on top 25 or so on the sides, with another 11 on the bottom.
Thoughts?
This would give
BeanAnimal
Premium Member
Same there really is no difference. As soon as you plop your disc into water, it then becomes a pump.
To test the theory all you need is a power head with most of the volute cut away... leave enough to keep the impellor centered. Place it face down over an air hose. The skimmer housing becomes the volute, and the water will begin to swirl.
Bean
To test the theory all you need is a power head with most of the volute cut away... leave enough to keep the impellor centered. Place it face down over an air hose. The skimmer housing becomes the volute, and the water will begin to swirl.
Bean
BeanAnimal
Premium Member
Lets also look the physics of this disc setup.
Lets say that we are using .5 cfm of air. The discs will have to be able to chop all of that air before it bubbles over it's edge. The disc will likely have to be fairly large and fast to keep up. I think you could do the math with RPM, bubble size and bubble vulme... but it's prolly not worht the trouble.
Bean
Lets say that we are using .5 cfm of air. The discs will have to be able to chop all of that air before it bubbles over it's edge. The disc will likely have to be fairly large and fast to keep up. I think you could do the math with RPM, bubble size and bubble vulme... but it's prolly not worht the trouble.
Bean
JC Pollman
Premium Member
Another problem: where does the water exit? Since only air gets past the whirling disk, I would guess you would have to have the exit above the disk?
BeanAnimal
Premium Member
If the disc may or may not prevent water from flowing past it. This would depend on the size and speed of the disc and the shape of the skimmer. Think of your blender.
Bean
Bean
did we ever find a local source for those 3m gringing disks? might be an interesting project anyway to try. just mount a power head with a needle wheel and no housing in a little box, bubble the bubbles up into it and let it dice without createing flow...
the bubbles themselves will pull water up with them.
itd be cheap and interesting to experiment with anyway.
the bubbles themselves will pull water up with them.
itd be cheap and interesting to experiment with anyway.
You need an impeller 4-6" in dia, not a powerhead impeller. Think of a CD with 1/4" notches cut out of the edge. Spin it at 100-500 rpm and bubble gas up beneath it. It will cause some water movement, but it may also provide very fine bubbles if that is what you are after. It did in the aluminum, but temperature, viscosity and a whole lot of differences exist. I just thought the idea may transfer and be a help.
so the disk is smooth except for the edges?
Id assume water would need a higher RPM, probably unacheivable in a thick material like liquid aluminum.
even so, probably doesnt need to be as large, theri probably mixing a much larger volume than we are.
I could try an ehiem with a disk... biggest water proof pump I have to play with.
Id assume water would need a higher RPM, probably unacheivable in a thick material like liquid aluminum.
even so, probably doesnt need to be as large, theri probably mixing a much larger volume than we are.
I could try an ehiem with a disk... biggest water proof pump I have to play with.
BeanAnimal
Premium Member
It is a neat idea, I just don't know that it will work in this type of scenario.
Figure a 6" dia disc at 500 RPM is 157 inches a second at the rim. A 1" diameter needlewheel at 3500 RPM is 183 inches a second at the rim. Not to far apart but I think the smaller needlewheel may do a better job.
Did you work with these units or help design them?
It may be worth looking into further, but more information on the actual designs would be needed to save trial and error learning.
Figure a 6" dia disc at 500 RPM is 157 inches a second at the rim. A 1" diameter needlewheel at 3500 RPM is 183 inches a second at the rim. Not to far apart but I think the smaller needlewheel may do a better job.
Did you work with these units or help design them?
It may be worth looking into further, but more information on the actual designs would be needed to save trial and error learning.
