Pressure loss through perforated plate (air)

[xj25]

I found this topic in thread798-186885.

There are two references for online calculator/graphic data

Usig both I get:

online:
Flow medium: air / gaseous
Volume flow: 690 m³/h
Weight density: 1.2 kg/m³
Dynamic Viscosity: 15.11 10-6 kg/ms
Element of pipe: Perforated plate thin circular
Dimensions of element: Diameter of pipe D: 297 mm (equivalent area of 0,07m2)
Clear area in %: 47
Velocity of flow: 2.77 m/s
Reynolds number: 65255 Flow: turbulent
Resistance coefficient: 5.35
Pressure drop: 0.25 mbar (25Pa)

from given graph in pdf:
v_mean = 690m3/h / 0.033m2 (perforated area) = 5.8m/s = 1100fpm
47% open area
So about 0.25inches of water = 62Pa

another online option:

http://www.frigprim.x10.mx/online/PerfPlate.html

v_mean = 690m3/h / 0.033m2 = 5.8m/s
47% open area
gives about 60-70Pa (graph solution)

First online solver seems quite lower (25Pa against 60), it seems because it considers a velocity (2.8m/s) quite lower than simple mean velocity (5.8m/s)
¿any idea why?

Thanks for reading!

 

[rjw57]

Perhaps explained here...

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

 

[xj25]

Actually the data shown there is the same graph of the pdf (2º option given in first post)

I think that the first online calculator makes something with the input pressure (1bar, given), flow (690m3/h, given) and open area to calculate the velocity 2.77m2/s, but anyhow is very much lower than the other references, so probably or I misuse the calculator or it makes something wrong...

Regards

 

[hacksaw]

to sort that out don't you need to know more about the orifice design

 

[Latexman]

Suggest you find and try the classical correlation of P. L. SMITH, JR., and MATTHEW VAN WINKLE. The Chemical Engineers' Handbook says it is typically within +/- 5% accuracy. It's on page 5-37 of my 6th Edition. It is for non-beveled, sharp-edged holes.

Good luck,
Latexman

 

[xj25]

I could check Perry`s handbook 8th edition, but dindn´t find that reference. Just simple orifice or grid "screens"
Can be checked in other source? i.e. google books ?

 

[Latexman]

You can Google that, right? It's in my 5th Edition of Perry's on page 5-35. I'll look around tomorrow at the office. As a last resort, you can buy the original article online:

Buy It Here

Good luck,
Latexman

 

[Latexman]

The correlation was removed from Perry's before the 7th Ed. was published, so the 6th Ed. is the last Ed. that had it.

Coulson and Richardson's Chemical Engineering Volume 6 - Chemical Engineering Design (4th Edition) has a method. It's for a sieve plate column design with countercurrent vapor and liquid flow. You would only want the contribution of the dry plate pressure drop by the vapor. The method starts on page 576 and there is an example. The example's dry plate drop starts on page 582.

That's all I got.

Good luck,
Latexman

 

[psafety]

My Input,

REFERENCES: INDUSTRIAL PERFORATORS ASSOCIATION; TESTING BY BOYLE ENGINEERING LABORATORIES and MARKS' MECHANICAL ENGINEERS HANDBOOK

-psafety