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Process industry environmental protection scheme(differential pressure1)
Feb 25, 2020

1.1 introduction to differential pressure flow

Differential pressure flow measurement (differential pressure flow) is one of the most common techniques to measure the flow in closed pipes.

There are many reasons why differential pressure flow technology is widely used.

Modern differential pressure flowmeter

This technology is based on the well-known physical laws, especially the laws of hydrodynamics and mass transfer;

The long use history also promotes the development of manufacture and use standard of differential pressure flowmeter;

The manufacturer provides a wide selection of general and special instruments and installation options;

Differential pressure flow technology can achieve high accuracy and repeatability.

1.2 history of differential pressure flow

Flow measurements originated thousands of years ago, when Egyptians began to make a rough forecast of the harvest based on the relative height of the Nile spring flood. Later, the Romans designed ditches to provide drinking water for the city, so it became important to monitor the demand for stable flow. The operator uses the flow through the orifice or the obstruction well to measure the flow roughly. The marks on the wall of the fluid medium and the flow intensity through the orifice give a rough flow measurement. Newton discovered the law of gravitation in 1687, which made physicists and mathematicians put forward the theory of motion and force, and finally promoted the development of quantitative flow.

Bernoulli principle

Daniel Bernoulli is a Swiss mathematician who studies fluid mechanics. His work focuses on the conservation of energy and achieves a key breakthrough in the development of flow measurement technology for the first time. He discovered Bernoulli's principle, which states that the sum of energy in the flow must remain constant regardless of the conditions. This means that the sum of static energy (pressure), kinetic energy (velocity) and potential energy (altitude) upstream and downstream are equal, especially differential pressure flow.

Reynolds number

Osborn Renault is not a physicist, but a force scientist. The most famous is his research on the fluid flow in the pipe, more specifically, the flow conversion conditions between laminar flow and turbulent flow. Reynolds number is the numerical quantification of the ratio of inertial force to viscous force. In short, Reynolds number describes the flow characteristics of the fluid. Reynolds number is a key concept in the design of flowmeter, which can be used as a constraint for the application scope of flowmeter.

1.3 pressure

What is stress? Pressure is the amount of force acting on a specified area.

When the force increases or the area decreases, the pressure increases;

When the force decreases or the area increases, the pressure decreases;

Measuring the pressure helps to prevent the equipment from being damaged due to excessive pressure;

Measuring the pressure helps to prevent accidental pressure or pressure release, resulting in personal injury.

Why pressure measurement?


Process efficiency

Cost saving

Measurement of other process variables

More accurate multi parameter flowmeter for process measurement

Safety: pressure measurement helps to prevent overpressure on pipes, tanks, valves, flanges and other equipment, minimize the possibility of equipment damage, control liquid level and flow, and help prevent accidental pressure or pressure release and personal injury.

Process efficiency: in most cases, the highest productivity occurs when the pressure (and other process variables) remains at a specific value or within a small range.

Cost savings: pressure or vacuum equipment, such as pumps and compressors, consumes a lot of energy. Energy cost savings can be reduced through pressure optimization.