How to determine aerator CFM

[bmlkidd]

I have a need to create an aeration tube in the bottom of a large storage tank. I plan on using 2" PVC pipe with a series of holes. I will construct a hexagonal shape with the PVC and place it in the bottom of the tank. I want to use an air compressor with a plate rating of 140CFM to aerate the liquid, at about 7PSI. My question is, is there any calculation I can use to determine:
1. Number and size of holes
2. Ensure the pressure is sufficient around the entire hexagon
3. Determine if 2" is the correct PVC pipe size to use?

Thanks,

 

[BigInch]

What's in the storage tank? If its water, you need to take the water height in the tank x 0.43 psi/ft, so with 7 psi, if the water is over 16 ft high, your air won't go out of the pipe at all. It might be better if you feed the ring from at least 2 or even 4 places with piping from the compressor, otherwise most of the air might be lost in the first 1/4 of the ring.

Look for the air flow tables at

http://www.engineeringtoolbox.com

That will get you close enough for pipe sizing, because actually your air will not be arriving at the end of the pipe. Its all gone by then, which is why I think its better to keep the lengths short by feeding from multiple points. In fact I would think it would be better to forget a ring and feed 4 "T" assemablies from the center of the tank (the bottom of that "T"). If you feed the ring from one end, it will be hard to get uniform air distribution around such a long ring.

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[btrueblood]

Some more advice, from the "been there, done that" school of fluid mechanics. Don't put the holes on the "top" of your headers, put them on the bottom. That way, the air will displace the water out of your headers, and you have some chance of getting uniform distribution. The other way, you have fairly chaotic startup conditions, with two-phase or slug flow occurring in most of the manifold, possibly continuing on "forever", as the water in the ends of the manifold never clears.