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://ww w.kele.com /archive/s olutions/S elValvesHy droSys.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?
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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
Q = 27.8 * ((95+15)/2.31)^0.5
Q = 27.8 * 47.6^0.5
Q = 27.8 * 6.90 = 191 gpm
BigInch
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