Cv to Kv converter
Convert valve flow coefficients between Cv and Kv, the American and European ratings for the same valve.
That's 2.3× as open as a small control valve, while a domestic ball valve is 1.3× higher. At a one-bar drop that passes about 166.7 liters a minute of water.
What it means
How much passes through?
Flow coefficients are for water. Gas, steam and viscous liquids need their own sizing equations, and choked flow caps the answer entirely.
Every unit
Your coefficient in every unit
Learn
Three things worth knowing
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Cv = 1.156 × Kv
Or Kv = 0.865 × Cv. The factor is just gallons against cubic meters and psi against bar, rolled into one number.
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Sizing without the physics
Rather than model the turbulence inside a valve, engineers measure one flow at one pressure drop and scale everything else from it. Flow follows the square root of the pressure drop.
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Cv is not a maximum
It is the flow at a one-unit pressure drop. At four times the drop you get twice the flow, not four times, because flow goes with the square root.
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Popular flow coefficient conversions
Background
About Cv and Kv
A valve’s flow coefficient says how much it passes at a fixed pressure drop. Cv is US gallons a minute of water at one psi; Kv is cubic meters an hour at one bar. The same valve carries both numbers on its datasheet.