Process Engineering Division – Instrumentation and Automation Section – Daily Question – Question from 2020-09-11

Throttling-based flow measurement is achieved based on Bernoulli’s principle. Bernoulli’s principle is essentially the principle of energy conservation in fluid flow; that is, when a pipe is filled with a fluid (a homogeneous medium), as the fluid passes through a throttling element, its kinetic energy increases while its static pressure energy decreases. By measuring the pressure difference between the flow before and at the throttling point, it is possible to determine the flow rate (velocity).

A throttling element is installed within the pipe; as the fluid flows through this element, its flow rate decreases, which results in a pressure difference across the element. For a throttling element of specific shape and size, at a particular measurement point and with straight pipes before and after it, as well as for fluid with certain properties under other given conditions, the pressure difference across the throttling element changes with the flow rate, and there is a definite relationship between the two. Therefore, the flow rate can be measured by measuring the differential pressure. Standard throttling devices are only suitable for measuring the flow rate of single-phase, homogeneous fluids in pipes with circular cross-sections, and it is required that the fluid fill the entire pipe ； No phase change or impurity precipitation occurs within a certain distance before and after the throttling element ； The flow velocity is less than the speed of sound, so the flow is non-pulsating ； Before flowing through the throttle element, the fluid stream must be parallel to the pipeline axis, with no rotational flow allowed. The display instrument of a throttling pressure-drop flow meter is a differential pressure gauge, whose scale is marked with flow values based on the relationship between the measured flow rate and the differential pressure.

Throttling-based flow measurement is achieved based on Bernoulli’s principle. Bernoulli’s principle is essentially the principle of energy conservation in fluid flow; that is, when a pipe is filled with a fluid (a homogeneous medium), as the fluid passes through a throttling element, its kinetic energy increases while its static pressure energy decreases. By measuring the pressure difference between the flow before and at the throttling point, it is possible to determine the flow rate (velocity).

Throttling-based flow measurement is achieved based on Bernoulli’s principle. Bernoulli’s principle is essentially the principle of energy conservation in fluid flow; that is, when a pipe is filled with a fluid (a homogeneous medium), as the fluid passes through a throttling element, its kinetic energy increases while its static pressure energy decreases. By measuring the pressure difference between the flow before and at the throttling point, it is possible to determine the flow rate (velocity).

Throttling-based flow measurement is achieved based on Bernoulli’s principle. Bernoulli’s principle is essentially the principle of energy conservation in fluid flow; that is, when a pipe is filled with a fluid (a homogeneous medium), as the fluid passes through a throttling element, its kinetic energy increases while its static pressure energy decreases. By measuring the pressure difference between the flow before and at the throttling point, it is possible to determine the flow rate (velocity).

Throttling-based flow measurement is achieved based on Bernoulli’s principle. Bernoulli’s principle is essentially the principle of energy conservation in fluid flow; that is, when a pipe is filled with a fluid (a homogeneous medium), as the fluid passes through a throttling element, its kinetic energy increases while its static pressure energy decreases. By measuring the pressure difference between the flow before and at the throttling point, it is possible to determine the flow rate (velocity).

The throttling method for measuring flow rate is based on the law of conservation of energy and the law of continuity of fluid flow. When fluid filling a pipe passes through a throttling device, a local constriction forms at that point, resulting in an increase in flow velocity and a decrease in static pressure. A pressure difference is created before and after the throttling device; the greater the flow rate, the larger the pressure difference. Under certain conditions, the square of the flow rate is proportional to the pressure difference.

Throttling-based flow measurement is achieved based on Bernoulli’s principle. Bernoulli’s principle is essentially the principle of energy conservation in fluid flow; that is, when a pipe is filled with a fluid (a homogeneous medium), as the fluid passes through a throttling element, its kinetic energy increases while its static pressure energy decreases. By measuring the pressure difference between the flow before and at the throttling point, it is possible to determine the flow rate (velocity).

Throttling-based flow measurement is achieved based on Bernoulli’s principle. Bernoulli’s principle is essentially the principle of energy conservation in fluid flow; that is, when a pipe is filled with a fluid (a homogeneous medium), as the fluid passes through a throttling element, its kinetic energy increases while its static pressure energy decreases. By measuring the pressure difference between the flow before and at the throttling point, it is possible to determine the flow rate (velocity).