the international authority on air system components fan performance mark stevens director of...

The International Authority on Air System Components

Fan Performance

Mark StevensDirector of Laboratory Services

AMCA International


Fan Testing for Air Performance


Test Fan

AMCA Standard 210

Auxiliary Fan

NozzlesFan Airflow

Piezometer Ring Fan Static Pressure


AMCA 210 Test Results

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12

Air Flow, Q

Pre

ssu

re,

P

0

0.5

1

1.5

2

2.5

Po

wer, H


Fan Laws for Speed Change

QC = NC N ( )Q Q, Fan Airflow Rate

2

PC = NC N ( )P P, Fan Pressure

H, Fan PowerHC = NC N ( )H

3


10% Speed Change

33% More H

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14

Air Flow, Q

Pre

ss

ure

, P

0

0.5

1

1.5

2

2.5

Po

we

r, H

10% More Q


AMCA Standards 500-D & -L

Test Damper

Auxiliary Fan

NozzlesDamper Airflow

Piezometer Ring Damper Pressure Drop


Fan Operating Point

Operating Point

0

100

200

300

400

500

600

700

0 2 4 6 8 10 12

Air Flow, Q

Pre

ss

ure

, P

AMCA 500-D Test Results


Speed Change

New Operating Point

New speed

0

100

200

300

400

500

600

700

800

0 2 4 6 8 10 12 14

Air Flow, Q

Pre

ss

ure

, P Operating Point


Damper Opening

New System

New Operating Point

0

100

200

300

400

500

600

700

0 2 4 6 8 10 12

Air Flow, Q

Pre

ssu

re, P

Operating Point


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


Test Fan

Installation Type DDucted Inlet / Ducted Outlet

Auxiliary Fan

NozzlesFan Airflow

Piezometer Ring Fan Static Pressure

Installed Fan

PlenumPlenum


AMCA Catalog Ratings

• “Performance certified is forinstallation type:

◦ A: Free inlet, Free outlet”◦ B: Free inlet, Ducted outlet”◦ C: Ducted inlet, Free outlet”◦ D: Ducted inlet, Ducted outlet”


System Effect

• Even when the tested duct configuration matches the installed duct configuration, improper duct design can introduce adverse flow conditions


Elbow Example


Detailed Plenum Example

Plenum



• Centrifugal Fan

• Airflow Rate◦ 14.4 m3/s

• Blast Area/Outlet Area◦ 0.6

• Velocity◦ 14.4 m/s

Blast Area

Cutoff

Outlet Area



E-F duct friction at 5000CMH (Q) 747 Pa (duct design)

E contraction loss-plenum to duct 50 Pa (part of duct system)

E PS energy required to create velocity at E 125 Pa (part of duct system)

D PV loss (also PT loss) at D as result of air velocity decrease 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



D-E duct friction at 5000CMH (Q) 747 Pa (duct design)

D contraction loss-plenum to duct 50 Pa (part of duct system)

D PS energy required to create velocity at D 125 Pa (part of duct system)

B-C SEF 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

------------------




Outlet Duct

100% Effective Duct Length

Calculation of SEF of 149 Pa

From AMCA Publication 210

From Figure 8.3t

Blast Area

NoDuct

12%Effective

Duct

25%Effective

Duct

50%Effective

Duc

100%Effective

Duct

U W --

Sys tem Effe ct C urve

U W --

U- V W- X --

W -X -- --

X -- --

-- -- --

0 .4

O utle t Area

0 .5

0 .6

0 .7

0 .8

0 .9

1 .0 -- -- --

P R -S

P R -S

R -S S-T

S U

T-U VW

W -W W -X

-- --


14.4 m/s

Using line R from Figure 7.1


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)


Ducted FanFan as Tested

C-D duct friction 750 Pa (duct design)

A free inlet 0 Pa (no SEF)

B-C outlet with straight duct attached for 2 or more diam. 0 Pa (no SEF)

--------------------



Ducted FanExhaust System

A Entrance loss-sharp edge duct 100 Pa (duct design)

A-B Duct friction at 5000CMH 750 Pa (duct design)

B SEF 1 (Elbow at Inlet) 150 Pa

C SEF 2 (Obstruction) 50 Pa

E SEF 3 (Abrupt Discharge) 150 Pa

------------------

REQUIRED Fan Ps 1200 Pa


Deficient Fan/System


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


Rules of Thumb

• Minimum 2.5 duct diameters on Outlet

• Minimum 3 to 5 duct diameters on Inlet

• Avoid inlet swirl


Recommendations

• Allow enough space in the building design to allow for appropriate fan connections to the system


Recommendations

• Use allowances in the design calculations when space or other factors dictate less than optimum arrangement of the fan outlet and inlet connections


Recommendations

• Include adequate allowance for the effect of all accessories and appurtenances on the performance of the system and the fan


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 fan performance mark stevens director of...

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