Perforated plate pressure drop calculations?

[brazilianjj]

I'm trying to figure out how to calculate the pressure drop of a perforated plate!
Could you provide me with assistance or information?

My current project is the design of a biotrickling scrubber. It is essentially a biological scrubber using lava rock with nutrient rich solution to degrade foul air (predominantly hydrogen sulfide).

The tower I'm designing is about 22 feet in diameter and the lava rock packing is 12 feet high. The flow rate is approximately 20,000 scfm. In order to insure that the foul air is distributed evenly across the bottom of the lava rock packing, I'm planning to install a perforated pvc plate beneath the lava rock packing. The rule of thumb to create an even air distribution is to create a 1inch w.c. pressure drop across the perforated plate. This would in effect create a back pressure.

Do you know what formula I could use to calculate the pressure drop? The surface area of the plate is fixed, but I'll have to vary the number and diameter of the holes on the plate.

 

[prex]

The book by I.E Idel'cik - Memento des pertes de charge - Eyrolles Paris has many formulae for various cases around you situation: their use is fairly complex. I don't know if an english version exists.
Also Perry's Chemical Engineers Handbook has a formula for the flow of gases through perforated plates.
If you can have acces to a basic book on pressure losses in pipes you can treat your case as a single diaphragm in a pipe, taking the hole size equal to the actual size of one hole, and the pipe section equal to the total area of perforated plate divided by the number of holes (of course the flow rate is scaled down in the same way).

prex
motori@xcalcsREMOVE.com

http://www.xcalcs.com

Online tools for structural design

 

[drgeers]

I had a similar project. Look up the Industrial Perferators Association on-line. They have a lot of information and charts for pressure drops.