Control valve calculator

calculation of flow coefficient - Cv or Kv

online since 2007

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Action
Calculation setup
Flow rates and velocity
Coefficients and pressure drop
Fluid properties

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Description

q - volumetric flow rate
Fluid flow rate in terms of units of volume per unit of time
ṁ - mass flow rate
Fluid flow rate in terms of units of mass per unit of time
V - velocity
Flow velocity in terms of units of distance per unit of time
D - internal diameter
Internal circular pipe diameter
Cv - flow coefficient
In imperial units - gpm
Kv - flow coefficient
In metric units - m3/h
p - pressure
Fluid pressure at the start of the pipe for gas density calculation based on the ideal gas state equation
ρ - fluid density
Mass per unit of volume

Calculation setup

Select value to calculate. You should enter not selected one.
q/ṁ
Calculate flow rate
Δp
Calculate pressure drop
Cv/Kv
Calculate flow coefficient
Select value to input. You should enter selected one. The other one will be calculated
q
volumetric flow rate
mass flow rate
Select value to input. You should enter selected one. The other one will be calculated.
Cv
flow coefficient in imperial units - gpm
Kv
flow coefficient in metric units - m3/h
Select value to input. You should enter selected one. The other one will be calculated.
v
flow velocity
D
internal pipe diameter

When is this calculator suitable?

To select a size of a control valve, you should calculate the required flow coefficient Cv/Kv for the flow rate and pressure drop.

For a specific control valve, flow coefficient Cv/Kv is determined experimentally by control valve manufacturers, and you can found it in manufacturers technical specifications.

They express coefficient Cv/Kv as the flow rate of water in g.p.m. [m3/h] for a pressure drop of 1 psi [1 bar] across a flow passage [flow coefficient: Cv-imperial, Kv-metric]. You can use the calculator to calculate maximum flow rate through control valve for given pressure drop and known flow coefficient of control valve Cv. With maximum flow rate calculated, you can compare control valves from different manufacturers for their efficiency for the same nominal size.

Control valve calculator is suitable for turbulent flow of liquids.

When is this calculator not relevant?

Flashing, cavitation, and chocked flow may reduce the control valve capacity. That calculation is not in this version of control valve calculator.

How is the calculation executed?

The calculator is calculating flow coefficient Cv/Kv using the relationship between pressure drop and flow rate in the control valve which is for complete turbulent flow following power law where flow coefficient Cv/Kv is the proportional constant:

where is:

q - flow rate
Cv - flow coefficient
Δp - pressure drop
S - specific gravity (relative density)

Available in download version

save/open multiple results
export to word and excel
print results
custom fluid properties
K factor for fittings, resistance coefficient
pipe surface roughness selection
select between gauge and absolute pressure
compressible isothermal flow
dry air isothermal flow
gas offtake flow
natural gas flow

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