What should I enter for the "Discharge Coefficient (fully open)" for a surge anticipator valve?How can I calculate the discharge coefficient (Cv) of a SAV?
This would typically be obtained from the Surge Anticipator Valve manufacturer. If they don't provide it, you can calculate it based on the information that you do have.For example, for a 4 inch opening (area of 0.087266 ft^2) and assuming an orifice coefficient of 0.6. Here is the orifice equation re-written as:H = (Q/CA)^2/(2g)Let's pick a flow of 1.0 cfs, which results in a pressure head (H) of (1.0 / (0.6 * 0.087266))^2 / (64.34) = 5.67 ft.The following equation can be used to find the discharge coefficient:Cv = ((39.693 * d^4) / ( H / (V^2 / 2g)))^0.5.You can plug in the pressure head along with the same flow and corresponding velocity (using Q=VA) to derive the discharge coefficient:Cv = ((39.693 * (0.33333)^4) / (5.67 / (11.456^2 / 64.34)))^0.5 =0.41985 cfs/(ft H2O)^0.5
Modeling Reference - Surge Valves