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Rahul Baro
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- TL;DR Summary
- Why Flow coefficient doesn't have any unit ?
Flow coefficient in valves doesn't have any units. why?
in what cases it does not have any unit?Lnewqban said:It can have units, if you want: (gallons / minute) * sqrt (1/p.s.i.)
Please, see:
https://en.wikipedia.org/wiki/Flow_coefficient
okay! i understood the idea.. thanks alot!Lnewqban said:In practical terms, the coefficient is expressed only as a number.
For example, the manufacturer of a valve tells an engineer that he offers two valves, one with Cv=20 and another one with Cv=10.
Those numbers by themselves, help the engineer select the valve that best fits its system and/or control modulation.
The first valve is able to carry 20 US gallons per minute for a pressure drop of 1 p.s.i., while the second valve, for the same pressure drop, will carry 10 US gallons per minute.
To expand/generalize, by definition a coefficient is a unitless multiplication factor, like a percentage. For example, a friction coefficient is a percentage/fraction of normal force "converted" to friction. Similarly, a flow coefficient is a fraction of velocity pressure lost in a valve or other device. The way we often use it in IP units, I think it is a bastardization that includes some rolled-up constants.Lnewqban said:In practical terms, the coefficient is expressed only as a number.
okay! thank you so much for the help :)russ_watters said:To expand/generalize, by definition a coefficient is a unitless multiplication factor, like a percentage. For example, a friction coefficient is a percentage/fraction of normal force "converted" to friction. Similarly, a flow coefficient is a fraction of velocity pressure lost in a valve or other device. The way we often use it in IP units, I think it is a bastardization that includes some rolled-up constants.
So usually if you see units, it's for clarification; eg, N/N (friction).
The Flow Coefficient Cv is a measure of the efficiency of a valve or other flow control device in terms of its ability to allow fluid to pass through. It is important because it helps engineers and scientists to determine the optimal size and type of valve for a particular application, ensuring efficient flow and preventing waste or damage to equipment.
Yes, the Flow Coefficient Cv does have units. It is typically measured in gallons per minute (GPM) or cubic feet per minute (CFM) in the United States, and in liters per minute (LPM) or cubic meters per hour (m³/h) in other countries. However, it is important to note that the units may vary depending on the specific industry or application.
The Flow Coefficient Cv is calculated by dividing the flow rate (in units of volume per unit of time) by the square root of the pressure drop across the valve or flow control device. This calculation is based on the Bernoulli's principle, which states that the total energy of a fluid flowing through a pipe remains constant.
No, the Flow Coefficient Cv is specifically designed for use with valves and other flow control devices that have a linear relationship between flow rate and pressure drop. It cannot be used for devices that have a non-linear relationship, such as flow restrictors or variable speed pumps.
No, the Flow Coefficient Cv is not a constant value. It can vary depending on factors such as the type of fluid being used, the temperature and pressure of the fluid, and the specific design and size of the valve or flow control device. It is important to consult manufacturer's data or perform calculations to determine the appropriate Cv value for a given application.