×
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

Orifice sizing clarification

Orifice sizing clarification

Orifice sizing clarification

(OP)
I am new to orifice sizing.
I am verifying the data from our contractor who sized a flow orifice on a medium pressure (43 bar) steam line to a turbine.Following data is available.
Full range flow = 10000 kg/hr
Operating flow = 5000 kg/hr
Opt. temp = 371 C
Opt press = 43 kg/cm2
Density (Ro) = 15.26 kg/m3

Contractor has provided the following results:
Orifice dia = 72.77 mm
Press drop max = 113.5 in H2O
Press drop opt. = 28.37 in H2O
Reynolds no. = 494253
Discharge coeff = 0.6

I tried to validate the data by using eq. to back calculate the flow rate:
q = CA sq.root(2DP/Ro)
q = m3/s
A = m2
DP = bar
Ro = kg/m3
C=0.6
But the results are far from matching, it comes out 22.2 kg/hr. Please guide for the right equation or anything I am doing wrong, thanks.
 

RE: Orifice sizing clarification

The flow is steam, so you must use in the equation the expansion factor, Y, and also take into account that the discharge coefficient, C, depends of the ratio between orifice diameter and pipe internal diameter.
Look at the Crane Technical Paper No 410.
Regards.
casflo   

RE: Orifice sizing clarification

If you provide the pipe ID, others can double check the results. Order of magnitude the vendor results seem correct.

I prefer the equation in mass flow units, which is:
W = 0.0125217 K d^2 Y1 (Den1 hw)^0.5
W = kg/h
K = C/(1-Beta^4)^0.5
C = roughly 0.61
d = orifice bore, mm
Den1 = inlet density, kg/m3
hw = pres drop, mmH2O, at same tap location as C and Y
Y1 = gas expansion factor
   = 1 − (0.41 + 0.35 Beta^4) dP/P1/k for close-up taps
k = Cp/Cv

Cilliers
www.korf.co.uk
 

RE: Orifice sizing clarification

(OP)
Do I need to use expansion factor? As Press drop/Inlet press= 0.004, and this gives Y~1.
I've taken above equation from crane papers.
Pipe ID=6 in.
CJKRuger, can you cross check?
Regards,

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