Venturi tube flow calculator

Description

p₁ - inlet pressure

Absolute pressure at the Venturi inlet

p₂ - throat pressure

Absolute pressure at the Venturi throat

Δp - pressure drop

Measured pressure difference

D₁ - inlet diameter

Venturi internal inlet diameter

D₂ - throat diameter

Venturi throat diameter

e - expansion factor

Coefficient used for compressible flow calculation

C - coefficient of discharge

Coefficient used for Venturi tube based on ISO 5167

R_eD - inlet Reynolds

Reynolds number calculated in front of the Venturi tube

R_ed - throat Reynolds

Reynolds number calculated at the Venturi tube throat

q₁ - volumetric flow rate

Fluid flow rate in terms of units of volume per unit of time on the inlet conditions

q - standard flow

Flow rate at standard conditions. Used only if the selected fluid is gas.

ṁ - mass flow rate

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

V₁ - upstream velocity

Flow velocity at the Venturi tube inlet where flow diameter is D₁

T₁ - upstream temperature

Fluid temperature for gas density calculation based on the ideal gas state equation

ρ₁ - upstream density

Fluid density at the Venturi inlet in terms of mass per unit of volume

R - gas constant

Gas constant in terms of energy per unit of mass and temperature, for gas density calculation using ideal gas state equation

κ - isentropic coefficient

Specific heat ratio

ν - kinematic viscosity

Result of fluid particles colliding to each other and moving at different velocities in terms of area per square unit of time

μ - dynamic viscosity

Result of fluid particles colliding to each other and moving at different velocities in terms of mass per square unit of distance and time

Calculation setup

Select Venturi tube type based on its manufacturing technology

Welded

Venturi tube manufactured by welding

Casted

Venturi tube manufactured by casting

Machined

Venturi tube manufactured by machining

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

p₂

pressure in the throat of the Venturi tube

Δp

measured pressure difference in front and in the throat of the Venturi tube

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

ν

kinematic viscosity

μ

dynamic viscosity

Select value to input. Available only if gas is selected. You should enter selected one. The other one will be calculated

T₁

upstream temperature.

ρ₁

upstream density.

Select fluid type

Gas

for compressible flow where ideal gas state equation is applicable

Liquid

for incompressible flow of liquids

Application of ISO 5167 constraints

ISO constraints

Deselect if you don't want to check if the Venturi tube and the flow conditions are within the limits of the ISO standard.

Why Use This Venturi Tube Calculator?

This Venturi tube calculator allows you to quickly and accurately determine the flow rate in a pipeline using a Venturi tube flow meter. By inputting just a few key values, you can calculate the actual flow rate based on the pressure difference caused by the contraction in the throat of the Venturi tube.

How Does the Venturi Tube Work?

When fluid flows through a Venturi tube, the narrowing at the throat increases velocity while maintaining a constant flow rate. This results in:

• ✅ Higher dynamic pressure due to increased velocity
• ✅ Lower static pressure due to conservation of total pressure

This static pressure drop can be easily measured before and at the throat of the Venturi tube, providing the key input needed for flow rate calculations.

Unlike other differential pressure flow meters like an orifice plate, the Venturi tube minimizes pressure loss, making it a preferred choice for accurate and energy-efficient flow measurement.

Additional Applications of the Venturi Effect

This calculator can also be used to analyze the Venturi effect, which is applied in various engineering devices, including:

• 🔹 Venturi vacuum pumps – Used in pneumatic systems
• 🔹 Gas burners – Enhancing fuel and air mixing
• 🔹 Wine aerators – Improving oxygenation for better flavor
• 🔹 Aspirators and grills – Creating airflow and suction

When Is This Calculator Suitable?

This tool is designed for subsonic, single-phase liquid or ideal gas flow. It provides reliable results for steady-state flow conditions where flow rate remains constant.

When Is This Calculator Not Applicable?

This calculator is not suitable for:

• ❌ Multiphase fluids (e.g., liquid-solid or liquid-gas mixtures)
• ❌ Non-ideal gases that deviate from the ideal gas law
• ❌ Pulsating or unsteady flows, where flow rate fluctuates over time
• ❌ Choked flow conditions, where velocity nears the speed of sound

What You Need to Perform the Calculation

To calculate the flow rate, you need to enter:

• 🔹 Venturi tube inlet and throat diameters
• 🔹 Fluid properties (density and viscosity)

For gas flow, you can enter:

• 🔹 Gas constant, pressure, and temperature (instead of density)
• 🔹 The calculator will determine the density using the ideal gas law

How Is the Calculation Performed?

This calculator follows the ISO 5167-4 standard, ensuring precision and reliability. However, accurate results are only guaranteed if the Venturi tube meets ISO requirements.

ISO 5167-4 Standard Conditions

For a perfect gas, the pressure ratio p₂/p₁ must be greater than 0.75.

As-cast Venturi tubes:
• 100 mm < D < 800 mm
• 0.3 < β < 0.75
• 200,000 < ReD < 2,000,000

Welded sheet iron Venturi tubes:
• 200 mm < D < 1200 mm
• 0.4 < β < 0.7
• 200,000 < ReD < 2,000,000

Machined Venturi tubes:
• 50 mm < D < 250 mm
• 0.4 < β < 0.75
• 200,000 < ReD < 1,000,000

(β = diameter ratio d/D)

What If Your Calculation Falls Outside These Limits?

If your Venturi tube or flow conditions do not meet ISO 5167-4 standards, the calculator will display a warning. You can still proceed with the calculation by choosing to ignore ISO constraints, but accuracy may be affected.

Use this Venturi tube calculator for precise, reliable, and efficient flow rate calculations in engineering applications! 🚀