Pipe flow calculators

Nozzle and Venturi nozzle calculator


Calculator Description

Nozzles and Venturi nozzles are devices that are inserted in circular cross-section conduit to create pressure difference of static pressure. Based on that pressure difference, flow rate of flowing fluid can be calculated.

  • Calculate:

    • Volumetric or weight Flow rate
    • Flow velocity in the nozzle inlet and throat
    • Discharge coefficient for compressible flow
    • Gas expansion coefficient for compressible flow
    • Reynolds numbers
  • Input:

    • Pressure difference at inlet and throat of nozzle
    • Nozzle inlet and throat diameter
    • Fluid density
    • Fluid viscosity

Calculator Features

  • Conversion between volumetric and weight flow rate
  • Calculation of Reynolds number included
  • Applicable for non-compressible liquids and compressible perfect gases
  • Pressure ratio p2/p1 must be equal or greater than 0.75
  • For single-phase fluid, subsonic, non-pulsating flow
  • ISO 5167 based calculation
  • Long radius, regular and Venturi nozzle types

Three types of nozzles are covered in calculator: ISA 1932 nozzle, long radius nozzle and Venturi nozzle. All three types differ from each other based on its shape. All nozzles have radius shaped convergent inlet with cylindrical throat and Venturi nozzle also has divergent part as outlet.

Calculation of gas flow with higher pressure drop and flow close or equal to choked flow conditions gas discharge calculator should be used.

Limits of use for nozzles are:

  • 50 mm < D < 500 mm
  • 0.3 < β < 0.8
  • 7x104 < ReD < 107 for 0.3 < β < 0.44
  • 2x104 < ReD < 107 for 0.44 < β < 0.80

Limits of use for long radius nozzles are:

  • 50 mm < D < 630 mm
  • 0.2 < β < 0.8
  • 104 < ReD < 107

Limits of use for Venturi nozzles are:

  • 65 mm < D < 500 mm
  • 0.316 < β < 0.775
  • 1.5x105 < ReD < 2x106

Values for coefficient of discharge or flow coefficient (C or Cd) can be calculated based on applicable standards like ISO 5167 or similar ASME standards.


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If you would like to use the calculator, but actually can't see the blue CALCULATOR button in the upper left part of the page than please read instructions.

Q: Calculate flow rate of air flowing through nozzle with pipe diameter of 200 mm and nozzle throat diameter of 100 mm, at 288 K. Measured pressures in front and in the throat of nozzle are 104000 Pa and 101325 Pa.

A: Calculation setup:
Flowing fluid: gas
Input one from following two:
p2 - absolute pressure after the orifice
T - temperature
ni - kinematic viscosity
Enter values:
D1 = 200 mm
D2 = 100 mm
p1 = 104000 Pa (absolute)
p2 = 101325 Pa (absolute)
ni = 13.4 mm2/s
T = 288 K
R = 287 J/kgK
kappa = 1.4
select nozzle type - nozzle

Q: Calculate flow rate of water flowing through nozzle with pipe diameter of 200 mm and throat diameter of 150 mm. Measured pressure in front of nozzle is 1015 mbar and pressure drop in nozzle is 5 mbar.

A: Calculation setup:
Calculate for: liquid
Input one from following two:
p1 - p2 - pressure drop
T - temperature
ni - kinematic viscosity
Enter values:
D1 = 200 mm
D2 = 150 mm
p1 = 1015 mbar (absolute)
p1 - p2 = 5 mbar (absolute)
ni = 1.006 mm2/s
rho = 1000 kg/m3
select nozzle type - nozzle

Q: Calculate flow rate of water flowing through nozzle to open atmosphere from 25 mm pipe pressurized with 1.5 bar absolute pressure. Nozzle diameter is 3 mm.

A: Calculation setup:
Calculate for: liquid
Input one from following two:
p2 - absolute pressure after the orifice
ni - kinematic viscosity
Enter values:
D1 = 25 mm
D2 = 3 mm
p1 = 1.5 bar (absolute)
p2 = 101325 Pa (absolute)
ni = 1.006 mm2/s
rho = 1000 kg/m3
select nozzle type - nozzle

Equation used for flow through nozzle calculation:

Read more about used theory on flow in valves and fittings page.

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