172-65639M-01 (EF200) 13 Apr 2018
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6. Technical Data
6.1 Technical Data at a Glance
6.1.1 Application
The measuring system is used to measure the flow of saturated steam,
superheated steam, gases and liquids. The variables volume flow and
temperature are measured directly. From these values, the device can used
stored data on the density and enthalpy to calculate and output the mass flow
and heat flow for example.
6.1.2 Function and System Design
Measuring Principle
Vortex flow measurement on the principle of the Karman
vortex street.
Measuring System
The measuring system consists of a transmitter and a
sensor.
Two versions are available:
•
Compact version: Transmitter and sensor form a single
mechanical unit.
•
Remote version: Sensor is mounted separate from the
transmitter.
6.1.3 Input
Measured Variable
•
Volumetric flow (volume flow)
→
is proportional to the
frequency of vortex shedding after the bluff body.
•
Temperature
→
can be output directly and is used to
calculate the mass flow for example.
The following variables can be output via internal
calculation:
Corrected volume flow, mass flow, calculated
saturated steam pressure, energy flow, heat flow
difference, specific volume, degree of superheat.
Measuring Range
The measuring range depends on the fluid and the pipe
diameter.
Start of Measuring Range:
Depends on the density and the Reynolds number
(Re
min
= 5,000, Re
linear
= 20 000). The Reynolds number is
dimensionless and indicates the ratio of a fluid’s inertial
forces to its viscous forces. It is used to characterize the
flow. The Reynolds number is calculated as follows:
Re =
4
∙ 𝑄
[
𝑚
3
𝑠
⁄
]
∙ 𝜌
[
𝑘𝑘 𝑚
3
⁄
]
𝜋 ∙ 𝑑𝑑
[
𝑚
]
∙ 𝜇
[
𝑃𝑃 ∙ 𝑠
]
Re = Reynolds number
Q = volume flow
di = pipe inner diameter
𝜇
= viscosity
𝜌
= density
15 - 300 mm
→
𝜐
𝑚𝑚𝑚
=
6
�𝜌
[
𝑘𝑘
/
𝑚
3
]
[
𝑚
/
𝑠
]
Full Scale Value:
•
Gas, steam: v
max
= 75 m/s (DN 15: v
max
= 46 m/s)
•
Liquids: v
max
= 9 m/s
