Azbil mF MVF Series, Руководство пользователя

Страница: 27 / 39

19
Therefore, mass flow rate can be measured starting from a minimum of 38m
3
/h
(normal).
2. Maximum measurable flow rate (volumetric flow rate (m
3
/h) and mass flow rate (m
3
/h (normal))
MVF flowmeters can measure velocity up to 30m/s.
The volumetric flow rate Qactual (m
3
/h) at velocity 30m/s is determined by
Qactual (m
3
/h) = S × V × 3600 = 516.
S: flow path cross-section of MVF080 (m
2
) = (78 × 10
–3
)
2
× π /4
V: velocity (m/s) = 30
The volumetric flow rate can be measured up to 516m
3
/h.
Next, we can calculate the mass flow rate at 0°C and one atmospheric pressure,
with temperature and pressure compensation, by
Mass flow rate can be measured up to 3765m
3
/h (normal).
3. Accuracy after temperature and pressure compensation
As an example, we will calculate the accuracy after temperature and pressure com-
pensation at 100m
3
/h and 150m
3
/h (normal), using the following formula:
Temperature and pressure sensor accuracy is as follows:
Temperature measurement accuracy: ±2% RD (absolute temperature base)
Pressure accuracy (% RD) = pressure measurement accuracy / (fluid pressure
(MPa) + 0.1013(MPa))
In this case, the pressure measurement accuracy is 1%FS in the 0 to 1MPa range.
In order to calculate the volumetric flow rate accuracy, Re is first calculated from
the mass flow rate (m
3
/h, normal).
The steps of the calculation are: mass flow rate
→
volumetric flow rate
→
velocity
→
Re.
Mass flow rate
→
volumetric flow rate calculation
Qactual (m
3
/h) = 100
×
((273+23) / (273+0)
×
(101.3 / (101.3 + 700)) = 13.7
Volumetric flow rate
→
Velocity calculation
Velocity V(m/s) = Qactual(m
3
/h) / S / 3600 = 13.7 / ((78
×
10
–3
)
2
× π
/4 / 3600 = 0.8
S: flow path cross-section of
MVF080
(m
2
) = (78
×
10
–3
)
2
× π
/4
Velocity
→
Re calculation
Re = (V
×
D)/
ν
= 0.8
×
78
×
10
–3
/ 1.883
×
10
–6
= 33139
V: velocity (m/s) = 0.8
D: internal diameter of the
MVF
body (m); for
MVF080
, D = 78mm
ν
: kinetic viscosity of fluid (m 2 /s)
For dry air, 23°C and 700kPa,
ν
= 1.883
×
10 –6 m 2 /s
Volumetric flow rate accuracy is checked by the Re value.
(%RD) =
Accuracy after
compensation
rate accuracy accuracy accuracy
( volumetric flow (%RD)
2
+ temperature (%RD)
2
+ pressure (%RD)
2
)
Qnormal (m
3
/h(normal)) = 516
×
((273+0)/(273+23))
×
((101.3+700)/101.3) = 3765
Amount of temperature
compensation Amount of pressure
compensation
Qnormal (m
3
/h(normal)) = 5.2
×
((273+0)/(273+23))
×
((101.3+700)/101.3) = 38
Amount of temperature
compensation Amount of pressure
compensation
Chapter 5. SPECIFICATIONS