How much is the pressure drop across the valve.
How great flow passing the valve.
The density of the liquid passing through the valve. In the original case, the liquid is assumed to be water.
KV = Water flow in m3/h at a pressure drop across the open valve of 1 bar (100 kPa).
Kvs = The selected valve Kv value at fully open valve. Typically a 30% safety margin to the calculated Kv value.
Difference between Kv and kvs
Many people confuse Kvs and Kv. Simple stated, it is a Kv-value component has the value and KV-value is the value that the component is expected to have operating case.
CV-value is the American equivalent to KV value. CV-value is defined as the water flow in U.S. gallons over a fully open valve with a pressure of 1 psi.