Volume of air bubbles coming from sparger

[sasha121]

Hi all,
I'm scratching my head for a while now trying to figure this one out. I want to make an air sparger, but instead of using a tube of some sort with holes in it, I'd like to try something different. Imagine a funnel, 10 ft diameter, flipped up-side-down. The funnel is submerged in a vessel with say water at a depth of 30 ft. Air is fed through the middle from the top by a blower which gives a certain volume of air. In these conditions all the air will be bubbled at the edges of the funnel. But since I want the air to be dispersed evenly across the surface of the vessel, I make 1/2" holes in the walls of the funnel so air can bubble through at those points. How can I calculate the number of holes that I need? If I add say only 2, most of the air will still go at the edges of the funnel. If I drill 2000 holes, maybe only the 200 holes which are higher will release all the air and no air will be left to bubble at the edges of the funnel. The attached sketch might explain better what I mean.

Any ideas?

Thanks a bunch!

 

[TD2K]

I'm not even going to ask why

Assume you want to maintain the air/water level in the funnel about 1/2 way between where you are putting the holes and the bottom of the funnel. You can also use a 1/4 or any other dimension.

That will give you the pressure inside the funnel which is static head to that level. You know the pressure on the outside of your orifices which is also static head. You have an air flow and now have a dP, calculate the flow through a 1/2" orifice to your blower capacity to determine how many holes you need. I'd strongly suggest working in mass units rather than actual volumes.

That's the theoretical approach. Depending on the height between where you want to put the holes and the bottom of the funnel, how level you can make install the 10' dia funnel, I'd play around with some excess number of holes to see how comfortable I am with the approach, how critical it is to get good distribution and where the air might go if my numbers are wrong.

 

[ports394]

http://www.mcmaster.com/#exhaust-mufflers/=grybux

 

[bimr]

What you are trying to do is impossible. There is not enough area on the cone to fit enough holes.

The EDI MaxAir SS Coarse Bubble Diffusers in the link below have 22 holes 5/16" in diameter and 12 holes 1/8" diameter in the 24-Inch long diffuser. The diffuser will do 5 to 36 CFM with the 3/4" orifice.

https://usabluebook-onramp.com/docs/images/49.pdf