## Control valve flow coefficient Cv and Kv |

Item | Data |
---|---|

Formula |
The flow through a valve can be calculated thanks to the
pressure drop through the valve and a coefficient Kv which
represents the number of m3/h of water that goes through the
valve at 15c and with a pressure drop of 1 bar. Manufacturers may specified the coefficient Cv instead of Kv for their valve. Cv is the number of US gallons that goes through the valve at 60F and with a pressure drop of 1 psi. It is actually possible to Kv and Cv and have the expression in the right unit for the calculation of interest. Cv=1.156Kv Note that these formula are only valid with Newtonian liquids. |

Nomenclature |
Q_{v}=Flow rate (m3/h)C _{v}=valve flow coefficient (GPM)K _{v}=valve flow coefficient (m3/hΔP=Pressure drop accross the valve (bar) d _{15}_{t}=density of the liquid referred to
water at 15 degrees (-) |

Usual values |
In order to have a good control, the design of the control valve should be such that it represents around 1/3 of the total pressure drop of the line. The valve must also be designed to work at flows corresponding to 50 to 80 percent of the Cv of the valve. |

Other relations |
The flow through the valve can be directly expressed with Cv
in US units With ΔP in Psi, Q _{v}in GPM, C_{v}in GPM |

Source |
- |