Flow measuring method and device
Flow measuring method and device for measuring the velocity of a single-phase or multi-phase flow. The method includes calculating the flow velocity U only by measuring consecutive values of pressure p, temperature T and momentum D, and then calculating the change in pressure Δp, change in temperature ΔT and change in momentum ΔD. The device includes a probe with a housing having electronic components connected to different sensors in the probe. The probe has a long, hollow momentum tube, fastened by its first end to the housing and a hollow, cylindrical sensor tube, located inside the momentum tube fastened by its first end to the first end of the momentum tube. The sensor tube includes plate capacitors located on the outside of the second end, and is thereby able to measure the conductance between the momentum tube and the plate capacitors on the sensing tube. The probe has a pressure sensor and a temperature sensor.
1 . Flow measuring method for the measurement of velocity in a single-phase or multi-phase flow, such as a multi-phase flow in a process pipe or similar, characterized in measuring two consecutive values of pressure p, temperature T and momentum D, then to calculate the change in pressure Δp, change in temperature ΔT and change in momentum ΔD, where the method further comprises the steps of calculating the velocity U after the following formula:
ΔD=−½U 2 Δp (5)
where Δp is expressed as
Δ
p
=
-
R
mix
T
p
2
Δ
p
+
R
mix
p
Δ
T
(
2
)
where R mix is the universal gas constant.
2 . Method according to claim 1 , characterized in that the method further comprises the step of measuring the pressure p, the temperature T and the momentum D in the proximity of each other in the process pipe.
3 . Method according to claim 1 , characterized in that the method further comprises the step of measuring the pressure p, the temperature T and the momentum D at the same time.
4 . A flow measuring device for measuring different parameters in a single-phase or multi-phase flow in a process pipe or process tank or similar, where a probe ( 1 ) comprises a housing ( 2 ) in a first end ( 1 A) and sensors in a second end (lb), where the housing ( 2 ) comprises a flange ( 21 ) able to be fastened to a pipe nipple in the process pipe or the process tank, and where the housing ( 2 ) preferably comprises electronic components connected to the different sensors in the probe ( 1 ) to perform the measurements and then to calibrate and transfer the measured results to a central monitoring unit, where the probe ( 1 ) further comprises a long, hollow momentum tube ( 3 ) fastened by its first end ( 3 A) to the housing ( 2 ), where the second end ( 3 B) of the momentum tube ( 3 ) is inserted into the process pipe or process tank, and where the probe ( 1 ) further comprises a hollow cylindrical sensor tube ( 4 ) located inside the momentum tube ( 3 ) and fastened by a first end ( 4 A) thereof to the first end ( 3 A) of the momentum tube ( 3 ), where the sensor tube ( 4 ) comprises plate capacitors (CA 1 , CA 2 , CA 3 , CA 4 ) located on the outside of the second end ( 4 B), thereby being able to measure the conductance between the momentum tube ( 3 ) and the plate capacitors (CA 1 , CA 2 , CA 3 , CA 4 ) on the sensing tube ( 4 ), characterized in that the probe comprises a pressure sensor, a temperature sensor and a momentum sensor.
5 . Probe according to claim 4 , characterized in that the pressure sensor and the temperature sensor are encapsulated in, or inserted in, a pressure and temperature unit located in the second end ( 3 B) of the momentum tube ( 3 ).
6 . Probe according to claim 4 , characterized in that the probe in its second end further comprises an erosion sensor ( 5 ) known per se.
7 . Probe according to claim 6 , characterized in that the erosion sensor comprises a pressure and temperature unit ( 7 ).