Yoshitake GD-20R, Manual

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- 7 - ■ EPDT-023c ■
2
P
P
1
2

2
P
P
1
2
≦
4.2 Selection Formula for Nominal Size
When selecting the nominal diameter by calculation, use the formula to find the required Cv value
based on the usage conditions, and then select the nominal diameter with a Cv value that satisfies
that value (see Table 7).
Table 7
Nominal Size 15A 20A 25A 32A 40A 50A 65A 80A 100A 125A 150A
Cv value 2.5 2.7 4 8.5 11 14 23 32.5 48 75 108
≪
For Gas
≫
In case of In case of
( )
( )
2 1
V
P P P
G t 273
2940
Q
C
+ 
+
=
( )
1
V
P 2550
G t 273 Q
C
+
=
≪
For Liquid
≫
P
G V 365 . 0
C
V 
=
However, the maximum flow rate V should be 3 m/s or less (see Table 8).
Table 8
Nominal Size 15A 20A 25A 32A 40A 50A 65A 80A 100A 125A 150A
Flow rate at flow
velocity 3m/s
2.20 3.96 6.46 10.81 14.67 23.72 39.09 55.21 94.00 145.05 204.21
For liquids with viscosity, apply the following viscosity correction calculation formula.
Find the Max. Flow rate (V) when the viscosity is ignored.
G 365 . 0
P Cv
V

 
=
And find the viscosity index of Iv.
2
1
4
1
cst
V
V
G
P
M
72780
I





 
=
Find the value of K from the value of Iv, found through the above formula, with the viscosity
correction curve. The calculated Max. flow rate divided by the value of K is the corrected value.
Compensated Max. flow rate V'
＝
V / K
（
m 3 /h
）
Fig. 7
P
1
：
Inlet pressure {MPa
･
A}
P
2
：
Outlet pressure {MPa
･
A}
ΔP
：
P
1
- P
2
{MPa}
G
：
Specific gravity
(Gas : Specific gravity relative to air
Liquid : Specific gravity relative to water)
Q
：
Max. gas flow rate {m 3 /h}
（
Normal state
）
V
：
Max. liquid flow rate {m 3 /h}
t
：
Temperature {
℃
}
Cv
：
Cv value of the nominal size
V'
：
Corrected flow rate {m
3
/h}
Iv
：
Viscosity index
Mcst
：
Viscosity {cSt}