The Differential Pressure Flow Measuring Principle (Orifice-Nozzle-Venturi)

Flow Measurement in Piping Systems

Overview of Fluid Transport

• Various substances, including solvents, chemicals, oil, gas, and steam, are transported daily through piping systems.

• The fluids have diverse properties requiring different measurement principles for accurate flow assessment.

Historical Context of Flow Measurement

• Daniel Bernoulli discovered the relationship between pressure and fluid speed over 300 years ago.

• Giovanni Battista Venturi built the first flowmeter for closed pipes in 1797, known as the "Venturi tube."

Differential Pressure Flow Measurement

• Differential pressure flowmeters utilize an artificial restriction (e.g., orifice plate) within a measuring tube to assess flow.

• Two holes in the pipe wall connect to a differential pressure sensor that measures pressure differences before and after the restriction.

Mechanics of Flow Measurement

• When fluid flows through the orifice plate, its velocity increases while static pressure decreases due to fluid mechanics laws.

• The resulting pressure difference correlates directly with flow velocity and mass/volume flow rates.

Applications and Design Considerations

• Orifice plates are widely used but may lead to excessive pressure loss or component abrasion from solids in fluids.