Basic knowledge

In the previous article, we introduced why measuring differential pressure can calculate flow rate. This traditional differential pressure measurement method has large measurement errors and small range ratios. In addition, the irregularity of various fluid parameters in turbulent states makes it impossible to apply traditional differential pressure measurement methods in the field of precision measurement of small flow rates.

YIDU flowmeter also calculates flow rate by measuring differential pressure, but unlike traditional differential pressure methods, YIDU flowmeter measures differential pressure in laminar flow state.

What is laminar flow?

The flow state of fluids in pipelines can be roughly divided into two types: laminar flow state and turbulent flow state. Turbulence refers to the irregular turbulence that accompanies the flow of a fluid, while laminar flow is the opposite. The flow exhibits layered motion, with each particle moving smoothly in a straight line along a direction parallel to the pipe axis.

Measurement basis for laminar differential pressure and flow rate

We now know that there is a relationship between differential pressure and flow rate, but traditional differential pressure methods have a non-linear relationship between differential pressure and flow rate, which greatly increases the difficulty of flowmeter calibration and makes it difficult to improve accuracy. Has the relationship between differential pressure and flow rate been improved in laminar flow?

In 1838, French doctor Jean Baudrillard discovered through extensive experiments that when an incompressible viscous fluid moves in laminar flow along a horizontal circular tube, the flow rate it passes through is proportional to the differential pressure applied at both ends of the tube, proportional to the fourth power of the tube's radius, and inversely proportional to the tube's length. He published this result in 1842. German engineer Gotthard Hagen also independently obtained the same result in 1839. This is the famous Hagenbauer's law, which is also the basis for laminar differential pressure flow measurement.

Jean Baudrillard

Advantages of laminar differential pressure technology

Now that it is known that there is a linear relationship between differential pressure and flow rate, the flowmeter can be calibrated to very high accuracy. The next thing to do sounds very simple:

① Transforming gas from turbulent to laminar state;

② Measure the differential pressure between two points in the laminar flow section.

These two tasks require the two most essential components in laminar flow meters: laminar flow element and differential pressure sensor. Through continuous research and development iterations, the YIDU laminar flow meter has overcome nearly 30000 technical problems, achieving a maximum accuracy of 0.5% S.P. and a measurement response time of less than 10ms. It has also achieved excellent levels of repeatability and stability, but this is still far from reaching the technical limit of the laminar differential pressure principle.

Why do laminar differential pressure flow meters have disruptive advantages in various aspects compared to all other types of flow meters currently available? Follow YIDU, we will answer your questions in the next article!