How Differential Pressure Flow Meters Work
The differential pressure flowmeter is based on the throttling principle of fluid flow, and realizes flow measurement by using the pressure difference generated when the fluid flows through the throttling device. It is currently one of the most mature and commonly used methods for measuring flow in production. It is usually composed of a throttling device that can convert the measured flow into a differential pressure signal, a differential pressure gauge that can convert the differential pressure into a corresponding flow value, and a display instrument. In the unit combination instrument, the differential pressure signal generated by the throttling device is often converted into a corresponding standard signal (electric or gas) by a differential pressure transmitter for display, recording or control.
1 Application overview
Such as fluid: single phase, mixed phase, clean, dirty, viscous flow, etc.; working state: normal pressure, high pressure, vacuum, normal temperature, high temperature, low temperature, etc.; pipe diameter: from a few mm to several m; flow conditions : Subsonic, sonic, pulsating flow, etc. Its consumption in various industrial sectors accounts for about 50% to 60% of the total consumption of flowmeters (about one million units per year).
2 instrument verification
The verification of a pair of differential pressure flowmeters includes:
(1) Geometry test method
⑵ Coefficient Verification
KERNB Annubar flowmeter
For the geometric test method, see the introduction of the test regulations, which will not be repeated here.
The following is a brief introduction to the relevant calculation formulas and methods involved in the coefficient verification method
Two calculation formula
v=aA√2/j(p-q)
v--volume
j--liquid density
a--flow coefficient, related to flow channel size, pressure taking method and flow rate announcement
A--hole plate opening area
p-q--pressure difference
The formula for calculating the outflow coefficient C of the orifice plate (organized by the author)
The Reynolds number can be calculated according to relevant formulas, such as:
Common calculation formulas for Reynolds number eD R
9 The basic error limits of the sensor shall comply with the provisions in Table 8
Measurement accuracy: ±0.2% ±0.5% ±1.0%
Repeatability: ±0.2%
Sensor error requirements
The above information about verification is for the reference of users who have verification devices. If there is any violation of JJG640-1994
