×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Air flow through a 2" orifice

Air flow through a 2" orifice

Air flow through a 2" orifice

(OP)
Hi,

I need to calculate the air flow through a 2" wall penetration between 2 rooms based on pressure difference of up to 1" of water. I am assuming that the penetration can be modeled as 2" round edge orifice. Crane Tech paper 410 provides the necessary equation for calculating the air flow for compressible and incompressible fluids.

My question is do I need to include the expansion factor Y and assume compressible flow or not.

Any help would be appreciated

Thanks
 

RE: Air flow through a 2" orifice

the expansion factor approaches unity for differential pressure << abs. pressure, so yes

RE: Air flow through a 2" orifice

for 1" water differential (0.036 psi) air does not need to be assumed as compressible, unless one room's pressure is almost a complete vacuum.

If you had rooms with absolute pressures approximately  atmospheric, expansion would only be (14.7 + 0.036)/14.7 that's only 1.002 x the volume in the lower pressure room.
 

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

RE: Air flow through a 2" orifice

The old equation for calculating leak rate across rooms is 2910xAxdP1/2, where A is area of opening in sq.ft and dP is differential pressure in inches WG. I still use this equation for design flow balancing in HVAC Systems.

You can use incompressible fluid flow equation, as suggested by BigInch. The best method to assess the leakage is Blower-Door Test.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources