×
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

Question on a Control Valve Selection Article

Question on a Control Valve Selection Article

Question on a Control Valve Selection Article

(OP)
For those who have a few minutes and don't mind reading an article, I have a question that I can't get past.  The article is on selecting control valves for variable flow hydronic systems.  I have sent an email to the author and hope to hear back.  In case I don't, I would appriciate an explaination from someone.  The article can be found here:

http://www.kele.com/archive/solutions/SelValvesHydroSys.pdf

My specific questions are as follows:

On the bottom left of page 2, the Cv of the branch is calculated to be 27.8 for a flow of 100 GPM and a branch DP of 30’.  But this is for the entire branch, so the actual control valve will have a Cv of 39.2 (100/(15/2.31)^1/2), correct?

If that’s true, then I am confused by the next statement that a 95’ drop across the valve will result in a max flow of 191 gpm.  With a Cv of 39.2 and a DP of 95’, flow should be 251 GPM.

What am I missing here?

RE: Question on a Control Valve Selection Article

Using Cv = 27.8 and 95 ft head drop across the valve PLUS 15 ft drop head in the branch,

Q = 27.8 * ((95+15)/2.31)^0.5
Q = 27.8 * 47.6^0.5
Q = 27.8 * 6.90 = 191 gpm

BigInchworm-born in the trenches.
http://virtualpipeline.spaces.msn.com

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