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7. Measurement Principle
7.3 Influence by Gas Composition to be Measured
U
U
O
M
Figure 1
Changes in air velocity values
coefficient
viscosity
flow rate
U
diameter
d
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Hot-wire Anemometers indicate air velocity based on the amount of radiation heat
which is the heat quantity deprived from the sensor to fluid. Depending on the fluid
to be measured, the amount of radiation heat varies, and the air velocity reading, too,
will be affected. Since all of the Anemomaster are calibrated in air at the normal
temperature and pressure, the indicated value requires to be compensated when you
measure mixed gas. Therefore, you need to know the physical property value of the
mixed gas beforehand in order to compensate the air velocity of mixed gas.
Below Figure 2 shows how to obtain the heat quantity diffused by the forced
convention from a cylinder (sensor).
density
r
kinematic viscosity
coefficient
g
V
r
reynolds number
Ud
Re
r
Nu=A×B
Figure 2 Heat diffusion quantity due to forced convention from a cylinder
specific heat
C
p
thermometric
conductivity
a
cpr
prandtl number
3600
Pr
a
nusselt
number
amount of radiation heat
+51 960 810 089
thermal
conductivity
length
r
Q
N
T
T
u
a
40
ventas@lazodecontrol.com
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