YOKOGAWA VY Series - Calculation Formulas

<3. Maintenance>
18
IM 01F07A01-02EN
3.7 Calculation Formulas
(1) Flow rate calculation
The ow rate is calculated based on the following formulas, where N is the count number of
generated vortices.
a)Instantaneousowrate(actualowrateunit)(RATE)
RATE = N×1 /∆t×ε
f
×ε
e
×ε
r
×1 / KT×U
k
×U
TM
KT = KM×U
KT
/ {1+Et (T
f
-15)×10
-5
}
b)Instantaneousowrate(%)(RATE(%))
RATE (%) = RATE×1 / F
S
×100
c) Totalized value (TOTAL)
TOTAL = TOTAL+∆TOTAL
∆TOTAL = RATE×∆t×1 / T
R
×1 / U
TM
d) Pulse output frequency (PULSE FREQ)
• For scaled pulse:
PULSE FREQ = RATE×1 / P
R
×1 / U
TM
• For unscaled pulse (no unit calculation):
PULSE FREQ = N×1 /∆t×1 / P
R
e) Flow velocity (V)
V = N×1 /∆t×1 / KT×U
KT
×4 / {π×D
2
}
f) Reynolds number (Re)
Re = V×D×ρ
f
×1 /μ×1000
N: Number of input pulses (pulse)
∆t: Time corresponding to N (sec)
ε
f
: Instrument error correction coe󰀩cient
ε
e
: Compressible uid expansion correction coe󰀩cient
ε
r
: Reynolds correction coe󰀩cient
KT: K factor for operating temperature (p/l)
KM: K factor at 15°C (p/l)
Et: Expansion coe󰀩cient
U
KT
: K factor unit conversion coe󰀩cient
U
k
: Flow rate unit conversion coe󰀩cient (Read "(2) Flow rate unit conversion coe󰀩cient (Uk)"
below.)
U
TM
: Time unit conversion coe󰀩cient (example: /m (min) = 60)
P
R
: Pulse rate
T
f
: Temperature at operating conditions (°C)
F
S
: Flow rate span
T
R
: Total rate
D: Inner diameter of vortex owmeter sensor section (mm)
μ: Viscosity coe󰀩cient (mPa·s)
ρ
f
: Density at operating conditions (kg/m
3
)