Valves

Liquid Control Valve Kv and Choking

Enter values in the stated units. Example inputs are provided to help you explore the method.

Results

Your results will appear here after calculation. Changing an input clears the previous result.

For turbulent liquid flow with no attached fittings correction: ΔP = P1 − P2; FF = 0.96 − 0.28√(Pv/Pc); ΔPchoked = FL²(P1 − FF Pv). All pressures must be absolute and use the same units.
Use ΔPeffective = min(ΔP, ΔPchoked). Convert Q from m³/s to m³/h and ΔPeffective from Pa to bar. Kv = Q(m³/h)√[(ρ/1000)/(ΔPeffective in bar)]. Kv is a flow coefficient referenced to water and 1 bar, not the actual service flow.
Assumes turbulent service, liquid at the inlet and piping geometry factor FP = 1. No Reynolds/viscosity correction, attached reducers, staged trim, gas, steam or inlet two-phase sizing is implemented.
FL must match manufacturer data for the candidate valve, trim and travel. Defaults are teaching assumptions, not a selected valve or verified fluid-property state. Repeat at minimum, normal and maximum operating cases.
Below the choking limit does not establish cavitation-free operation. Outlet pressure below vapor pressure indicates flashing; damage and noise are not predicted. Assess pressure recovery, materials and service limits with manufacturer data.
Kv alone does not determine nominal valve size, opening, rangeability, actuator capability or control stability. The comparison ignoring choking must not replace the limiting-pressure result.