Enter the flow rate, pressure drop and fluid specific gravity to find the required flow coefficient for a liquid valve. Results in both Cv (US) and Kv (metric).
Liquid, turbulent, non-choked flow. For gas/steam, flashing or choked service, use the full ISA/IEC 60534 sizing equations.
For liquid (turbulent, non-choked) service, Cv = Q x sqrt(SG / dP), where Q is flow in US GPM, dP is pressure drop in psi, and SG is specific gravity. The result is the flow coefficient: the GPM of water at 60 deg F that passes through the valve at 1 psi drop.
Cv is the US/imperial flow coefficient (GPM at 1 psi); Kv is the metric flow coefficient (m3/h at 1 bar). They convert directly: Kv = 0.865 x Cv, or Cv = 1.156 x Kv.
Cv quantifies a valve's flow capacity: a higher Cv passes more flow for the same pressure drop. It is used to size valves so they deliver the required flow without excessive pressure loss.