7-7
IM 01F06A00-01E
7. MAINTENANCE
(3) Mass Flow calculation
a)
Steam
In case of saturated steam, mass flow rate is calculated
from density values to temperature measured by using
saturated steam table.
In case of superheat steam, mass flow rate is calculated
from density values to temperature measured by using
steam table. In order to measure superheat steam, it is
necessary to make constant pressure value. A pressure
values which is entered in parameter is used.
M =
ρ
ft
· Q
f
..........................................................................................................
(7.14.1)
b)
Gas
In case of gas, Volumetric flow rate at standard
condition is calculated, so Pressure-Temperature
correction is carried out. It is necessary to make
constant pressure value. A Pressure values at opera-
tional condition, temperature and pressure value at
standard condition which is entered in parameter is used.
Q
n
= Q
f
· –– · –––––––––– · –– ............................ (7.14.2)
c)
Liquid
In case of liquid, mass flow late is calculated from
which used to calculate the secondary function for the
density value to the temperature. A density value which
indicated by the order sheet is used.
M = Q
f
·
ρ
n
· {1 + a
1
(T
ft
– T
n
) · 10
-2
+ a
2
(T
ft
– T
n
)
2
· 10
-6
}
........................................................................ (7.14.3)
[Supplement]
M = Q
f
·
ρ
f
= Q
f
·
ρ
n
· {1 + a
1
(T
f
– T
n
)
×
10
-2
+ a
2
(T
f
– T
n
)
2
×
10
-6
}
Where,
∆
T
f
= T
f
– T
n
Density compensation formula;
ρ
f
=
ρ
n
{1 + a
1
·
∆
T
f
×
10
-2
+ a
2
∆
T
f
2
×
10
-6
}
ρ
1
: Density at T
1
ρ
2
: Density at T
2
k
1
=
ρ
1
/
ρ
n
k
2
=
ρ
2
/
ρ
n
∆
T
1
= T
1
– T
n
∆
T
2
= T
1
– T
n
Then a
1
and a
2
can be calculated from formulas below,
a
1
= {(k
1
– 1) ·
∆
T
2
2
– (k
2
– 1) ·
∆
T
1
2
} /
{(
∆
T
1
·
∆
T
2
2
–
∆
T
2
·
∆
T
1
2
)
×
10
-2
}
a
2
= {(k
1
– 1) ·
∆
T
2
– (k
2
– 1) ·
∆
T
1
} /
{(
∆
T
1
2
·
∆
T
2
–
∆
T
2
2
·
∆
T
1
)
· 10
-6
}
Where
M :
Mass flow
Q
n
:
Volumetric flow rate at Standard condition
Q
f
:
Volumetric flow rate at oprtating condition
T
n
:
Temperature at operating condition (
°
C), (
°
F)
T
f
:
Temperature at standard condition (
°
C), (
°
F)
T
ft
:
Measured temperature value (
°
C), (
°
F)
P
f
:
Pressure at operating condition (kPa abs), (psi)
P
n
:
Pressure at standard condition (kpa abs), (psi)
K :
Deviation factor
ρ
ft
:
Density calculated by temperature value
ρ
n
:
Density at Standard condition (kg/m
3
), (lb/cf)
ρ
f
:
Density at operating condition
U
ρ
f
:
Density unit conversion factor
U
k(kg)
, U
k(Nm
3
)
, U
k(m
3
)
: Flow unit conversion factor
a
1
:
1st temperature coefficient
a
2
:
2nd temperature coefficient
Example: conversion factor in kg.
kg : U
kkg
=1
ton : U
kkg
=0.001
P
f
T
n
+ 273.15
1
P
n
T
fT
+ 273.15 K
