I would like to know if there is a way to calculate the Cv of two series mounted valves ( Globe Valve ) in combination. They are the same type of valve.
Would there be a different calculation for two different types of valves?
From a long time ago I can remember the following equation:
(1/Cv,total)^2 = (1/Cv,valve1)^2 + (1/Cv,valve2)^2
It's analagous to resistors in series. Cv is conductance, so resistance is inversely related to conductance.  And the math gets a little more fun because the resistance is proportional to Q^2
2 identical valves in series would have an effective net Cv of 0.707 (or 1/sqrt 2)  times the Cv of either.  

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