GE PanaFlow MV80, Руководство пользователя

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Chapter 1. Introduction
4 PanaFlow™ MV80 & MV82 User’s Manual
1.3.3 Flow Velocity Range
To ensure trouble-free operation, vortex flowmeters must be correctly sized so that the flow velocity range through the
meter lies within the measurable velocity range (with acceptable pressure drop) and the linear range.
The measurable range is defined by the minimum and maximum velocity using Table 1 below.
The pressure drop for series MV82 insertion meters is negligible. The pressure drop for series MV80 in-line meters is
defined as:
Δ
P = .00024
ρ
V
2
English units (
Δ
P in psi,
ρ
in lb/ft
3
, V in ft/sec)
Δ
P = .000011
ρ
V
2
Metric units (
Δ
P in bar,
ρ
in kg/m
3
, V in m/sec)
The linear range is defined by the Reynolds number. The Reynolds number is the ratio of the inertial forces to the
viscous forces in a flowing fluid and is defined as:
Where,
Re
= Reynolds Number
ρ
= mass density of the fluid being measured
V = v
elocity of the fluid being measured
D = i
nternal diameter of the flow channel
μ
= viscosity of the fluid being measured
The Strouhal number is the other dimensionless number that quantifies the vortex phenomenon. The Strouhal number
is defined as:
Where,
St
= Strouhal Number
f
= frequency of vortex shedding
d = s
hedder bar width
V = f
luid velocity
Table 1: Measurable Ranges
Parameter Gas Liquid Units for
ρ
V
min
1 ft/s
English
ρ
(lb/ft
3
)
V
max
300 ft/s 30 ft/s
V
min
0.3 m/s
Metric
ρ
(kg/m
3
)
V
max
91 m/s 9.1 m/s
25ft/s
ρ
---------------
37m/s
ρ
----------------
Re
ρ VD
μ
----------
=
St
fd
V
----- =