What is the Coefficient of Flow (Cv) of Valves

The "Coefficient of Flow," often referred to as the "Flow Coefficient" or simply "Cv," is a measure of the efficiency of a valve in controlling fluid flow through a system. It is a dimensionless number that provides an indication of how much flow a valve can allow for a given pressure drop across the valve.


The flow coefficient (Cv) is typically defined based on the following formula:

Cv = Q / √(ΔP)



Cv: Flow coefficient (a constant specific to the valve)

Q: Flow rate (usually in gallons per minute, GPM, or cubic meters per hour, m³/h)

ΔP: Pressure drop across the valve (usually in pounds per square inch, PSI, or pascals, Pa)

In simpler terms, the Cv value represents the flow rate of water (or other fluid) that a valve can pass through while experiencing a pressure drop of 1 PSI (or 1 Pa) across the valve. A higher Cv value indicates that the valve can handle a larger flow rate for a given pressure drop, implying greater flow capacity.

Different types of valves (ball valves, globe valves, butterfly valves, etc.) will have different Cv values due to their unique designs and characteristics. Manufacturers provide Cv values to help engineers and users select the appropriate valve for a specific application to achieve the desired flow rate and pressure drop.

Keep in mind that while Cv is a useful parameter for comparing and selecting valves, it's important to consider other factors such as the fluid properties, valve type, materials, and system requirements when designing a fluid control system.

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