Control valve calculator

Description

q - volumetric flow rate

Fluid flow rate in terms of units of volume per unit of time

ṁ - mass flow rate

Fluid flow rate in terms of units of mass per unit of time

V - velocity

Flow velocity in terms of units of distance per unit of time

D - internal diameter

Internal circular pipe diameter

Cv - flow coefficient

In imperial units - gpm

Kv - flow coefficient

In metric units - m³/h

p - pressure

Fluid pressure at the start of the pipe for gas density calculation based on the ideal gas state equation

ρ - fluid density

Mass per unit of volume

Calculation setup

Select value to calculate. You should enter not selected one.

q/ṁ

Calculate flow rate

Δp

Calculate pressure drop

Cv/Kv

Calculate flow coefficient

Select value to input. You should enter selected one. The other one will be calculated

q

volumetric flow rate

ṁ

mass flow rate

Select value to input. You should enter selected one. The other one will be calculated.

Cv

flow coefficient in imperial units - gpm

Kv

flow coefficient in metric units - m³/h

Select value to input. You should enter selected one. The other one will be calculated.

v

flow velocity

D

internal pipe diameter

When Should You Use This Control Valve Calculator?

This control valve calculator helps you determine the required flow coefficient (Cv/Kv) based on the flow rate and pressure drop, ensuring you select the right valve size for your system.

How Does This Calculator Work?

Control valve manufacturers determine the Cv/Kv flow coefficient experimentally, and these values are listed in technical specifications. The Cv/Kv coefficient represents the flow rate of water in gallons per minute (gpm) [or cubic meters per hour (m³/h)] with a pressure drop of 1 psi [or 1 bar].

With this calculator, you can:

• ✅ Calculate the maximum flow rate through a control valve for a given pressure drop and Cv/Kv coefficient.
• ✅ Compare control valves from different manufacturers to assess performance and efficiency for the same nominal size.

When Is This Calculator Not Applicable?

Calculation Methodology

The calculator determines the Cv/Kv flow coefficient using the power-law relationship between pressure drop (Δp) and flow rate (q) for fully turbulent flow:

$q=\mathrm{Cv}\times \sqrt{\frac{\mathrm{\Delta p}}{S}}$

Where:
• q = Flow rate
• Cv = Flow coefficient
• Δp = Pressure drop
• S = Specific gravity (relative density)
This control valve calculator is an essential tool for engineers, HVAC professionals, and fluid system designers looking to size and compare valves effectively.