KvCvWerte

KvCvWerte is a term used in valve technology to refer to two related flow coefficients, Kv and Cv, that quantify a valve’s flow capacity. Kv is the metric flow coefficient and Cv is the US customary flow coefficient. They are used to describe how much fluid a valve will pass for a given pressure drop when the valve is fully open.

Kv is defined as the flow rate of water (at approximately 20 °C) through the valve, measured in cubic meters per hour (m3/h), with a pressure drop of 1 bar across the valve. Cv is the flow rate of water in US gallons per minute (gpm) with a pressure drop of 1 psi. Both coefficients are intended for incompressible liquids and are commonly applied in valve sizing and performance specifications.

The relationship between Kv and Cv is governed by the units. For the same valve and the same service, Q = K × sqrt(ΔP) applies, with Kv using ΔP in bar and Q in m3/h, while Cv uses ΔP in psi and Q in gpm. The standard conversion between them is approximately Kv ≈ 0.865 × Cv, or Cv ≈ 1.156 × Kv.

Usage and standards: Kv and Cv are widely used in valve sizing across Europe and North America, respectively. They appear on manufacturer datasheets and in engineering calculations for HVAC, process industries, and piping systems. Precise values depend on valve design, opening, fluid properties, temperature, and whether the valve is fully open.

Limitations: The simple formula assumes water near 20 °C and a fully open valve. For other liquids, gases, high pressure drops, or non-laminar flow, corrections or manufacturer data are necessary.