×
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

Flow Through Irregular Orifices

Flow Through Irregular Orifices

Flow Through Irregular Orifices

(OP)
I need to estimate compressible fluid flow through an irregular orifice (i.e., a thin, circular ring or gap as opposed to a circular hole).  I would think that an upper bound would be provided by modeling my flow area as a circular hole with an equivalent flow area to my "gap" area.  However, I need a more accurate estimate...a conservative upper bound will not help me much.  Does anyone have any correlations for this sort of orifice/flow path or know where to point me to?  If it helps, the pressure drop across the orifice will be on the order of 10 to 25 psi.

Thanks!

RE: Flow Through Irregular Orifices

Dony, Orifices come in four flavors, annular, concentric, eccentric, segmental. I think you're looking for the annular flavor. Check in Perry's Chemical Engineer's Handbook.

Hope this helps.
saxon

RE: Flow Through Irregular Orifices

There was a long discussion on this a few months ago when someone was trying to calculate the flow through an annular area.  You might want to try a keyword search.

RE: Flow Through Irregular Orifices

such calculations are usually performed on the basis of the wetted perimeter of the orifice. the flow equations work fine in gap type flows.

RE: Flow Through Irregular Orifices

(OP)
Hacksaw,

When you say the "wetted perimeter of the orifice," do you mean I need to choose a standard "hole" orifice with an equal perimeter and run the flow equations?

I could calculate the annular diameter...or is that what you meant?

There was some discussion in a MechE forum that I found (and I believe that you participated in).  The result of that discussion..for incompressible flow...was that an article by Lenkei could provide some insight.  Are you familiar with that article, and if so, would it provide insight for compressible fluid flow?

RE: Flow Through Irregular Orifices

(OP)
I think that it would also be helpful to redefine the problem just a bit.  Instead of a traditional annular flow, I am faced with to cylinders sitting on top of each other, separated by about .7 inches.  The cylinders are about 3 feet in diameter.  The flow is going up through the cyliders, but then it can also escape out of the "gap".  It, in many ways, is more similar to flow through a slit or rectangle cut into a piece of plate than it is like flow through an annulus.  But, perhaps, the two can be calculated similarly.

RE: Flow Through Irregular Orifices

Two issues. Irregular orifices can be dealt with on the basis of an hydraulic radius (i.e. an effective flow area) regardless of the shape. This is approximate.

As far as the flow through your 0.7" slot, you know the area and you either know the pressure drop or you can estimate the fluid velocity. Either way you can come up with a flow estimate. Exact, hardly, but by the same token not to bad.

you are describing a common estimate made in civil hydraulics in regard to storm intercept leakage and or inflows. it is do able

RE: Flow Through Irregular Orifices

(OP)
Estimating the velocity is quite tricky, no?  I am dealing with compressible fluid flow.  I could assume sonic velocity as a bounding case.  But, now I have that velocity through a very large slot area.  If I were to find the hydraulic radius of the slot (ratio of flow area to perimeter), then I get a much smaller diameter - and corresponding area.  Sonic velocity through each of these flow areas (full slot area and area of a circle with radius equal to the hydraulic radius of the slot) would result in very different volumetric flow rates.  Are you recommending calculating the area from the hydraulic radius?  Do I worry about discharge coefficients?

Thanks again for the discussion.

RE: Flow Through Irregular Orifices

if you know the area, and you acknowledge that the flow is compressible, then knowing the static pressure you will be able to ascertain if sonic flow conditions are achieved and thus the fluid velocity.

this is not rocket science, just estimate it and be done with it

RE: Flow Through Irregular Orifices

use "ISO 5167" guide

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