Transcript Fan Peformance April 2008

Fan Performance
Mark Stevens
Director of Laboratory Services
AMCA International
The International Authority on Air System Components
Fan Testing for Air Performance
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AMCA Standard 210
Piezometer Ring
Fan Static Pressure
Nozzles
Fan Airflow
Test Fan
Auxiliary Fan
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AMCA 210 Test Results
800
2.5
700
2
500
1.5
400
1
300
200
0.5
100
0
0
0
2
4
6
8
Air Flow, Q
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10
12
Power, H
Pressure, P
600
Fan Laws for Speed Change
QC =
( )
( )
( )
NC
N
Q
Q, Fan Airflow Rate
P
P, Fan Pressure
H
H, Fan Power
2
PC =
NC
N
3
HC =
NC
N
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10% Speed Change
800
2.5
700
2
600
500
1.5
400
1
300
200
0.5
10% More Q
100
0
0
0
2
4
6
8
Air Flow, Q
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10
12
14
Power, H
Pressure, P
33% More H
AMCA Standards 500-D & -L
Test Damper
Piezometer Ring
Damper Pressure Drop
Nozzles
Damper Airflow
Auxiliary
Fan
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AMCA
Test Point
Results
Fan500-D
Operating
700
600
500
Pressure, P
Operating Point
400
300
200
100
0
0
2
4
6
8
Air Flow, Q
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10
12
Speed Change
800
700
600
New Operating Point
Pressure, P
500
New speed
Operating Point
400
300
200
100
0
0
2
4
6
Air Flow, Q
8
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10
12
14
Damper Opening
700
600
Pressure, P
500
Operating Point
400
New Operating Point
300
New System
200
100
0
0
2
4
6
8
Air Flow, Q
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10
12
System Effect
• Installed duct configuration does not
match tested duct configuration
• Detrimental effect on fan air performance
due to adverse flow conditions at the inlet
or outlet of a fan
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Installation Type D
Ducted Inlet / Ducted Outlet
Piezometer Ring
Fan Static Pressure
Nozzles
Fan Airflow
Test Fan
Auxiliary Fan
Plenum
Plenum
Installed Fan
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AMCA Catalog Ratings
• “Performance certified is for
installation type:
◦
◦
◦
◦
A: Free inlet, Free outlet”
B: Free inlet, Ducted outlet”
C: Ducted inlet, Free outlet”
D: Ducted inlet, Ducted outlet”
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System Effect
• Even when the tested duct
configuration matches the installed duct
configuration, improper duct design can
introduce adverse flow conditions
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Elbow Example
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Detailed Plenum Example
Plenum
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Detailed Plenum Example
• Centrifugal Fan
• Airflow Rate
Cutoff
◦ 14.4 m3/s
Blast Area
Outlet Area
• Blast Area/Outlet Area
◦ 0.6
• Velocity
◦ 14.4 m/s
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Detailed Plenum Example
E-F
duct friction at 5000CMH (Q)
E
contraction loss-plenum to duct
E
PS energy required to create velocity at E
D
PV loss (also PT loss) at D as result of air velocity decrease
747 Pa (duct design)
50 Pa (part of duct system)
125 Pa (part of duct system)
0 Pa
PS does not change from duct to plenum at D
C-D outlet duct on fan as tested
0 Pa
--------------------
REQUIRED Fan PS
922 Pa
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Detailed Plenum Example
D-E duct friction at 5000CMH (Q)
D
contraction loss-plenum to duct
D
PS energy required to create velocity at D
B-C SEF
747 Pa (duct design)
50 Pa (part of duct system)
125 Pa (part of duct system)
149 Pa
B-C PV loss (also PT loss) at C as result of air velocity decrease
0 Pa
PS does not change from duct to plenum at C
------------------
REQUIRED Fan PS
1071 Pa
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Detailed Plenum Example
Calculation of SEF of 149 Pa
From AMCA Publication 210
No
Duct
From Figure 8.3
12%
Effective
Duct
25%
Effective
Duct
50%
Effective
Duc t
100%
Effective
Duct
Outlet Duct
Blast Ar ea
Sys tem E ffe ct C urve
O utle t Area
100% Effective Duct Length
0 .4
P
R -S
U
W
--
0 .5
P
R -S
U
W
--
0 .6
R -S
S -T
U- V
W- X
--
0 .7
S
U
W -X
--
--
0 .8
T-U
VW
X
--
--
0 .9
W -W
W -X
--
--
--
1 .0
--
--
--
--
--
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Using line R from Figure 7.1
14.4 m/s
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Plenum Example from AMCA 201
Assuming:
• Use of the same fan for both systems
• Can attain both operating points with a
change in speed
• The increased in power consumption to
overcome System Effect is about 25%
◦ (1071/922)0.5 = 1.08 (Fan Law for pressure)
◦ 1.083 = 1.25 (Fan Law for Power)
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Ducted Fan
Fan as Tested
C-D duct friction
A
free inlet
B-C outlet with straight duct attached for 2 or more diam.
750 Pa (duct design)
0 Pa (no SEF)
0 Pa (no SEF)
--------------------
REQUIRED Fan PS
750 Pa
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Ducted Fan
Exhaust System
A
A-B
B
C
E
Entrance loss-sharp edge duct
Duct friction at 5000CMH
SEF 1 (Elbow at Inlet)
SEF 2 (Obstruction)
SEF 3 (Abrupt Discharge)
REQUIRED Fan Ps
100 Pa (duct design)
750 Pa (duct design)
150 Pa
50 Pa
150 Pa
------------------
1200 Pa
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Deficient Fan/System
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Speed Changes
• Before Increasing Speed
◦ Check with the manufacturer for max safe
operating speed
◦ Determine expected power increase
• Motor size
• Electric Service
◦ Expect more noise
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Rules of Thumb
• Minimum 2.5 duct diameters on Outlet
• Minimum 3 to 5 duct diameters on Inlet
• Avoid inlet swirl
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Recommendations
• Allow enough space in the building design
to allow for appropriate fan connections to
the system
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Recommendations
• Use allowances in the design calculations
when space or other factors dictate less
than optimum arrangement of the fan
outlet and inlet connections
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Recommendations
• Include adequate allowance for the effect
of all accessories and appurtenances on
the performance of the system and the fan
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Thank you
AMCA International, Inc.
30 W. University Drive
Arlington Heights, IL 60004
USA
Tel: +1 847 394 0150 Fax: +1 847 253 0088
www.amca.org
Mark Stevens - [email protected]
The International Authority on Air System Components