16 UMFLUXUS_G6V4-2EN, 2011-03-29
FLUXUS G60x 3 Measurement Principle
= k
Re
.
k
a
.
Δt/(2
.
t
fl
)
.
A
with
With the fluid mechanics correction factor k
Re
, the measured average value of the flow
velocity along the measuring path is converted into the average value of the flow velocity
across the cross-sectional pipe area. In case of an undisturbed flow profile, the fluid me-
chanics correction factor only depends on the Reynolds number and the roughness of
the inner pipe wall. The fluid mechanics correction factor is recalculated for each new
measurement.
The acoustic calibration factor k
a
is calculated, according to the law of refraction, from
the sound velocity inside the transducer and the angle with which the sound beam is
transmitted into the pipe wall and then into the medium: k
a
= c
α
/sin α = c
β
/sin β = c
γ
/sin γ
(see Fig. 3.2). The acoustic calibration factor is constant for each transducer.
-
volumetric flow rate
k
Re
- fluid mechanics correction factor
A - cross-sectional pipe area
k
a
- acoustic calibration factor
Δt - transit time difference
t
fl
- transit time in the medium
transducer
flow direction of the medium
signal in the flow direction
signal against
the flow direction
pipe wall
α
β
γ
c
α
c
α
c
γ
c
β
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