Pipe flow calculators
Calculator Description
Venturi tube calculator can be used for calculating of actual flow rate through Venturi tube used as flow meter, for measured pressure drop in the tube and can also be used for Venturi tube sizing.

Calculate:
 Flow rate for known Venturi size and pressure difference
 Flow velocity in the Venturi inlet and throat
 Discharge coefficient for compressible flow
 Gas expansion coefficient for compressible flow

Input:
 Pressure difference at inlet and throat of Venturi tube
 Venturi inlet and throat diameter
 Density
 Viscosity
Calculator Features
 Conversion between volumetric and weight flow rate
 Calculation of Reynolds number included
 Applicable for noncompressible liquids and compressible perfect gases
 Pressure ratio p_{2}/p_{1} must be equal or greater than 0.75
 For singlephase fluid, subsonic, nonpulsating flow
 ISO 5167 based calculation
Venturi tube is used as flow meter in piping system and where Venturi effect is required. Due to the change in diameter from inlet to throat mean velocity is changing while weight flow rate remains constant.
As total pressure remains mainly constant, part of static pressure is transformed into dynamic pressure from inlet to throat and pressure drop is created. This is called Venturi effect. Measuring static pressure on the inlet and on the throat  pressure drop, with this calculator, flow rate can be calculated, based on the energy conservation law and Bernoulli theorem.
For calculation of flow rate through Venturi tube in this calculator coefficient of discharge is calculated, as well as values of Reynolds number and mean velocity on the inlet and the throat of Venturi tube.
Calculator can also be used for Venturi effect analysis which is exploited in many appliances like Venturi vacuum pump, gas burners, wine aerator, aspirators, grills etc. Limiting factor for Venturi effect is when flow reaches chocked flow and mean velocity is close to local speed of sound.
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 Venturi tube with an "as cast" convergent section:
 100 mm < D < 800 mm
 0.3 < β < 0.75
 2x10^{5} < Re_{D} < 2x10^{6}
Limits of use for Venturi tube with a rough welded sheet iron convergent section:
 200 mm < D < 1200 mm
 0.4 < β < 0.7
 2x10^{5} < Re_{D} < 2x10^{6}
Limits of use for Venturi tube with machined convergent section:
 50 mm < D < 250 mm
 0.4 < β < 0.75
 2x10^{5} < Re_{D} < 1x10^{6}
Please tell me what do you think about this calculator
Q: Calculate flow rate of air flowing through Venturi tube with bigger diameter of 200 mm and throat diameter of 100 mm, at 288 K. Measured pressures in front and in the throat of Venturi tube is 104000 Pa and 101325 Pa.
A: Calculation setup:
Flowing fluid: gas
Input one from following two:
p_{2}  absolute pressure in Venturi throat
T  temperature
ni  kinematic viscosity
Enter values:
D_{1} = 200 mm
D_{2} = 100 mm
p_{1} = 104000 Pa (absolute)
p_{2} = 101325 Pa (absolute)
ni = 13.4 mm^{2}/s
T = 288 K
R = 287 J/kgK
kappa = 1.4
select Venturi type  welded tube
Q: Calculate flow rate of water flowing through Venturi tube with bigger diameter of 200 mm and throat diameter of 100 mm. Measured pressures in front and in the throat of Venturi tube is 108000 Pa and 100000 Pa.
A: Calculation setup:
Calculate for: liquid
Input one from following two:
p_{2}  absolute pressure in Venturi throat
ni  kinematic viscosity
Enter values:
D_{1} = 200 mm
D_{2} = 100 mm
p_{1} = 108000 Pa (absolute)
p_{2} = 100000 Pa (absolute)
ni = 1.006 mm^{2}/s
rho = 1000 kg/m^{3}
select Venturi type  welded tube
Q: Calculate flow rate of water flowing through Venturi tube with bigger diameter of 150 mm and throat diameter of 100 mm. Measured pressures in front and in the throat of Venturi tube is 108000 Pa and 100000 Pa. Venturi tube is machined.
A: Calculation setup:
Calculate for: liquid
Input one from following two:
p_{2}  absolute pressure after the orifice
ni  kinematic viscosity
Enter values:
D_{1} = 150 mm
D_{2} = 100 mm
p_{1} = 108000 Pa (absolute)
p_{2} = 100000 Pa (absolute)
ni = 1.006 mm^{2}/s
rho = 1000 kg/m^{3}
select Venturi type  machined tube
Equation used for flow through Venturi tube calculation:
Read more about used theory on flow in valves and fittings page.
If you experience problems with calculator start try to find answers on instructions page.
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