airflow - perforated steel 2

[jbthiel]

Can anybody help me predict the pressure drop/airflow through a perforated steel plate? My application is ~6000cfm with an opening of ~4000in2 with ~58% open area. I would like to calculate the effect of changing the % open area or opening size.

 

[TD2K]

I'd estimate it based on reduction in area will increase the pressure drop by approximately the square of the change. For example, if you reduce the area by 10%, the dP should increase by about 21%. If you need to estimate the dP through the sheet, I'd estimate the number of holes you have, the flow rate through each hole and then calculate the dP as an orifice.

 

[dvd]

The Industrial Perforators Association has some information which you may find useful at:

http://www.iperf.org/pressure.htm

 

[ChasBean1]

Good link by dvd, but we're off-scale low for your application. TD2K is right. Decrease open area by a factor of two, pressure goes up by four. Decrease area by a factor of three, pressure goes up by nine.

ASHRAE has a pretty reliable and user-friendly equation to work with for air:

Q = 2,610 * A * dP^.5

Q = flow in cfm
A = net open (or orifice) area in square feet
dP = pressure difference driving (or resulting from) flow, in inches of water

 

[Rich2001]

Something I learned the hardway, while deigning and testing Biological Safety Cabinets. [red]Any bow, no matter how slight, will significantly affect the air flow, changing by as much as 30%. [/red]

 

[jbthiel]

Thanks for the help.

 

[ahhai]

Hi chasbean1,

appreciate if you be more specific on the equation,

Q = 2,610 * A * dP^.5

Q = flow in cfm
A = net open (or orifice) area in square feet
dP = pressure difference driving (or resulting from) flow, in inches of water

i need to size the perforated floor board enough air circulation for the server rack.

thanks.