CV is actually a flow coefficient which is really speaking to the capacity of the valve.
If the valve has a CV of 20 that really is saying we can pass 20 gallons per minute of water with one pound pressure drop.
I would like to introduce one web based application which will help you to calculate the flow coefficient or CV.
ValveSmart . You can access valvesmart from the following link . www.valvesmart.com
Enter the required details on the sheet and click on calculate button.