Control valve plays an important role in the process industry by controlling different process parameter.
It is an important step to choose the correct type of control valve based on application. so, based on an application we want to choose the control valve with less energy dissipation.
Turbulence occurs in the form of a like control valve is in the middle of operation means in between fully open or fully closed, due to that energy will dissipate.
How in electrical circuit resistor play a role by reducing the amount of electron flow and energy dissipates in the form of heat, same in the case of a control valve it dissipates energy in the form of turbulence.
In many engineering publications, it is noted that size a valve such that it operates between 20% to 80% at a maximum flow rate.
So, a correct sized control valve increase plant availability reduced maintenance and increase profit.
As you can see in the above images of two different valve type produce turbulent which cause valve performance to degrade and increase the uneven cost. To choose correct cv is a must.
While sizing the control valve most important factor to be considered is to calculate the flow coefficient.
In simple, a valve cv is defined as the number of a gallon per minute at 60-degree Fahrenheit that will pass through a valve with a pressure drop of 1 psi.
For example, a valve with 20 GPM / PSI passes 20 GPM of flow with a pressure drop of 1 psi.