Flow Rate from Kv

The flow rate through a valve with a known Kv coefficient is calculated as: Q = Kv × √(ΔP ÷ SG), where Q is the resulting flow in m³/h, ΔP is the pressure differential across the valve in bar, and SG is the specific gravity of the fluid. This calculation predicts the actual operating flow through an installed valve at a given pressure differential. It is useful for verifying that a selected valve will pass the required flow under the available pressure conditions in the hydronic circuit. Flow through a valve varies with the square root of the pressure drop, meaning doubling the pressure drop increases flow by only about 41%. In practice, the available pressure across a control valve changes as other valves in the system open and close, which is why proper valve sizing and authority are important for maintaining stable flow control throughout the operating range.