Valves are sized based on the volumetric flow passing through them. The most important characteristic of a valve is its kvs value. Since this value is determined with water at a temperature of 5…30 °C and a differential pressure Δp of 100 kPa (1 bar), additional influencing factors must be taken into consideration if the properties of the medium passing through the valve are different.
The following properties of a medium affect valve sizing:
The density ρ and the specific heat capacity c have a direct impact on the volumetric flow, which transfers the required amount of heat or cooling energy
The kinematic viscosity ν influences the flow conditions (laminar or turbulent) in the valve and thus the differential pressure Δp at a given volumetric flow V