# Bubbles per second to cc/min



## snafu (Oct 9, 2004)

depends on the bubble diameter, but for an 1/8" bubble it would be 1 to 5 cc/min. someone should double check my math...


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## rhodesengr (Nov 23, 2008)

well I thought of an easy way to measure my present flow rate. I can just put my output line into an inverted, water filled beaker. The gas will displace the water and I can see how much got pushed out in one minute. Instant cc/min measurement.


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## Hoppy (Dec 24, 2005)

With 1/8 inch diameter bubbles, one bubble is about .00086 cubic inches. For a flow of one bubble per second that it .00086 cubic inches per second, or .052 cubic inches per minute. One cubic inch is 16.39 cubic centimeters. So, one bubble per second is about .85 cc per minute. And, I don't think gas flow meters can register that low a flow rate.

You can consider this flow rate to be sccm, standard cubic centimeters per minute, since the gas is essentially at standard atmospheric pressure.


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## rhodesengr (Nov 23, 2008)

Cole Palmer has one that is 5.8 cc/min full scale so that might work.


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## ka NUK (Nov 29, 2008)

Hoppy said:


> With 1/8 inch diameter bubbles, one bubble is about .00086 cubic inches. For a flow of one bubble per second that it .00086 cubic inches per second, or .052 cubic inches per minute. One cubic inch is 16.39 cubic centimeters. So, one bubble per second is about .85 cc per minute. And, I don't think gas flow meters can register that low a flow rate.
> 
> You can consider this flow rate to be sccm, standard cubic centimeters per minute, since the gas is essentially at standard atmospheric pressure.


Nice illustration Hoppy :thumbsup:

That got me thinking about how quickly your CO2 actually evaporates out of the tank. I get about 0.75 cm^3/min out of my DIY yeast generator. This is diffused into about 76650 cm^3 of water volume in my case. This translates into a theoretical increase of almost 9 ppm every minute (if none is lost). I aim for about 20+ ppm ...the rest is lost to the atmosphere :eek5:
The calculation could also be used to determine the efficiency of your diffusion method.

It should be easy enough to use the bubble counter to get an accurate reading: If your bubble size is about 1/8" in diameter, multiply your bubble rate by 0.013 cm^3 to get a pretty accurate idea of what is going into your tank. How much actually _stays_ in your tank is another question:redface:

ka NUK


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## rhodesengr (Nov 23, 2008)

*Required CO2 to get to 20 ppm*

I dusted off my chemistry and physics books and calculated how much gas it would take to get to 20 ppm. So my tank is 36 gallons. This translates into 4.56e27 water molecules. 20 ppm requires 9.12e22 CO2 molecules. There are 2.51e18 CO2 molecules in 1cc at room temp and room pressure. So is takes an astounding 3630 cc's dissolved in 36 gallons of water to have 20ppm. This assumes no loss. I'll let someone else figure out how many 1/8" bubbles that is. But I found that I can inject about 10 cc/min without overloading my injector. At that rate and with no loss, it would take 6 hours to inject enough CO2 to reach 20ppm. I run my system "open-loop" which means I do not have a pH feedback to turn the gas on and off. I just inject at a steady rate and only while the lights are on. So based on this I should expect my CO2 to increase slowly during the light cycle but never reach the desired 20ppm.


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## ka NUK (Nov 29, 2008)

rhodesengr said:


> I dusted off my chemistry and physics books (...schnipp)


There you go (I didn't have to dust off the Physics text, as I use it daily :redface

One word of caution: Parts-per-million does not refer to the ratio in terms of molecules (moles). ppm is usually used to compare mass of one compound to another. For my calculations I used volume. This works great for water (1g = 1ml = 1 cm^3 @ sea level and 4 deg. C) but not so much for CO2 in a gaseous state. 

Your mileage may vary:icon_roll

ka NUK


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## Guerillah (Nov 3, 2008)

The company I work for makes mass flow controllers all the way down to .5 SCCM. Maybe I should take one home and try it out.


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## rhodesengr (Nov 23, 2008)

Mass Flow Controllers are great and can be combined with feeback for a closed loop but they are well out of the price range for what most people are willing to spend for an aquarium. Now if you can borrow a bunch from your company and disperse them to us for evaluation.....


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## Hoppy (Dec 24, 2005)

Just reverse engineer one, substitute a few cheaper Chinese versions of some of the parts, eliminate the unnecessary parts, reduce your profit margin to 5%, don't paint it, and you can afford to sell them to us for $50 each. Right? Ok, maybe you will have to have them assembled in Columbia or Ecuador, and shipped by horseback, but won't it be worth it to make such a contribution to the hobby?


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## Guerillah (Nov 3, 2008)

rhodesengr said:


> Mass Flow Controllers are great and can be combined with feeback for a closed loop but they are well out of the price range for what most people are willing to spend for an aquarium. Now if you can borrow a bunch from your company and disperse them to us for evaluation.....


Yea, they are more expensive than anyone would want to pay. It's over $1500 for a 0.5 SCCM controller, slighty less for a meter.


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