G M Engineering
CV Flow Coefficients
|Data for Calculation of Flow
The coefficient of flow Cv expresses the rate of flow in gallons per minute at 60°F water with a pressure drop of 1 psig across the valve.The Cv coefficients for the various types and sizes shown in the tables, have been determined from actual flow tests.
Note: Kv is the metric equivalent of Cv.
KV = CV x 0.85
Where QL = Flow in U.S. gallons per minute.
Δ P = (P1–P2) Pressure drop in psi.
GL = Specific gravity of liquid (water = 1 at 60°F).
Where Qg = Volumetric flow of gas (SCFH).
Gg = Specific gravity of gas at standard conditions.
(air at atmosphere and 60°F = 1)
T = Absolute temperature of gas
(°F + 460).
Note: For gas, max. ΔP = 1⁄2 P1, and min.
P2 = 1⁄2 P1, and P1, P2 are absolute pressures (psia)
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