Water hydraulics
Liquid flow through a Kv valve
- where
- volume flow (m³/h; the calculator shows L/min)
- valve flow coefficient (m³/h at 1 bar)
- valve pressure difference (bar)
- liquid specific gravity to water
Explain this equation
Works out the flow through a valve with a known Kv and pressure drop. Use it to estimate flow when you can measure the drop across a valve.
Kv is the valve's published coefficient, the m³/h of water it passes at 1 bar drop. Δp is the drop across it in bar. SG is the liquid's specific gravity compared with water.
Flow rises with the square root of pressure drop, so quadrupling the drop only doubles the flow. Heavier liquids flow less for the same drop. The calculator shows L/min.
Sense check: Kv 2 at 0.1 bar passes about 0.63 m³/h, roughly 10.5 L/min. At 0.4 bar it doubles to about 21 L/min.
Watch out: liquid only, and the Kv must match the actual valve setting.
Enter your values to see the result.
Good to know
Single-phase liquid model.
Sources
Results are arithmetic only. Worked examples are not recommended design settings. This library does not provide automatic gas pipe selection, live gas tightness tests, purging procedures, combustion acceptance limits, installation approval or commissioning certification. Manufacturer data and the applicable current method remain essential.