Fujitsu UTZ-BD025B, Техническое руководство

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- (01-34) -
[2] Conversion from Rectangular Duct to Circular Duct
Long
Sid
e
De
Equivalent
Diameter
Short Side Fig. 7-4

How to use Fig. 7-4
Example: A rectangular duct measuring 40 x 200
corresponds to a circular duct having a diameter of 90.
1) To determine the intersection (A) of
the short side (40) and the long side
(200).
2) Next, to determine the line (B) going
through the intersection (A), and
determine the intersection (D) with
the diagonal line (C).
The figure (D) indicates the corresponding
diameter, which is 90 in this case.
[3] Local Pressure Loss in Duct
1) Local loss coefficient (also referred to as “local resistance
coefficient”)
At bends or portions where cross sections change, losses
different in nature from those in straight potions will occur
due to eddy currents, etc. These pressure losses in places
other than straight portions can be expressed by the
following formula.
Where, : Local Loss Coefficient
V: Wind Velocity .......................................... [m/s]
* This is the velocity of the upper part of the local
area excluding the merging point.
Pv: Dynamic Pressure ................................... [Pa]
2) Calculation of pressure loss at a local area in a duct Example:
Consider a case in which the duct bends as follows.
A round bend with the circular
cross section
[Conditions] R/d = 1.5 V = 5.0 (m/s)
From Table 7-1, = 0.15
From the above, P = (Local Loss Coefficient) x Pv (Dynamic
Pressure) = 0.15 x 15 = 2.25 [Pa]
The right side in Table 7-1 indicates the value of the local
pressure loss in this particular part converted to a duct
diameter. ( : Case in which PVC pipe is used)
<Set at 0.018>
le:Straight pipe corresponding length of the local resistance ... [m]
d: Straight pipe diameter ...[m]
: Local loss coefficient : Duct friction resistance coefficient
Long
Sid
e
Short Side
Table 7-1
No. Name
Graphic
Depiction
Conditions
Loss
Coefficient
Length
Corresponding
to PVC Pipe
H/W R/d
1
A round bend
with the circular
cross section
0.5 0.71 39d
0.75 0.33 18d
1.0 0.22 12d
1.5 0.15 8d
2.0 0.13 7d
2
A square bend
with the circular
cross section
0.5
1.2 67d
3
A round bend
with rectangular
cross section
0.5 1.30 72d
0.75 0.52 29d
1.0 0.25 14d
1.5 0.20 11d
1
0.5 1.20 67d
0.75 0.44 24d
1.0 0.21 12d
1.5 0.17 9d

CALCULATION IN SIMPLIFIED
METHOD

A case in which a model is selected, based on straight
pipe corresponding length and airflow quantity A model is
selected, based on the following conditions.
Required ventilation quantity: 120 [m
3
/h] Duct system: Fig.
7-5 (60Hz)
(Example Problem)
Ceiling-Mounted
Ventilation Fan
Duct Diameter:
100mm
Material: Galvanized
Steel Pipe
( = 0.02)
Fig. 7-5
(Case in which the galvanized steel pipe of = 0.02 is used)
Pipe Hood Bent Cap
Type
Product
Number
Duct
Diameter
Straight Pipe
Corresponding Length
Type
Product
Number
Duct
Diameter
Straight Pipe
Corresponding Length
Stainless Steel
(Rectangular)
FY-WKX042 ø100mm 5m
Stainless Steel
FY-VCX042 ø100mm 2m
FY-WKX062 ø150mm 12m FY-VCX062 ø150mm 4m
Stainless Steel
(Round)
FY-MCX042 ø100mm 9m
Stainless Steel
(Accompanied by
an insect net)
FY-VNX042 ø100mm 5m
FY-MCX062 ø150mm 13m FY- VNX062 ø150mm 7m
Stainless Steel
(Accompanied by
a fire damper)
FY-MCXA042 ø100mm 12m
Stainless Steel
(Accompanied by
a fire damper)
FY-VCXA043
BL
ø100mm 8m
FY- MCXA062 ø150mm 13m
FY-VCXA063
BL
ø150mm 7m
Aluminum (Round)
FY-MCA042 ø100mm 9m
Aluminum
FY-VCA042 ø100mm 2m
FY-MCA062 ø150mm 13m FY-VCA062 ø150mm 3m
Aluminum
(Accompanied by
an insect net)
FY-MNA042 ø100mm 15m
(R/d = 1.0) Elbow
ø100mm 2m
FY-MNA062 ø150mm 32m ø150mm 3m
Table 7-2

Table 7-2 is used to convert
the resistance at each
component of the duct to
the straight pipe length.
Table 7-3

Static Pressure - Quantity Characteristic Curve

To select an appropriate model.
Case in which a model satisfying
the straight pipe corresponding
length: 19 [m] and the airflow
quantity of 130 [m
3
/h]
A perpendicular line is dropped
from the intersection (A) made
by the resistance curve of the 19
[m]-pipe and the static pressure
- quantity characteristic curve to
determine the point (B), and the
model to be selected should satisfy
the value at the point, that is, 130
[m 3 /h].
Piping
Portion
Length of Corresponding Straight
Pipe (Diameter: 100mm)
I 0.5m
II 2m
III 0.5m
IV 2m
V 5m
VI 9m
Total 19m
Pi
pe
R
es
is
ta
nc
e
Curv
e
Airflow Quantity (m
3
/h)