AMCA International Technical Seminar 2009 System Effects Presented

AMCA International Technical Seminar 2009 System Effects Presented by: Joe Brooks, AMCA International, Inc.

The Air Movement and Control Association International (AMCA), has met the standards and requirements of the Registered Continuing Education Providers Program. Credit earned on completion of this program will be reported to the RCEPP. A certificate of completion will be issued to each participant. As such, it does not include content that may be deemed or construed to be an approval or endorsement by NCEES or RCEPP. System Effects, Slide 2

Learning Objectives l Describe system resistance of components l Know how a fan interacts with the system l Define System Effect and System Effect Factor (SEF) l Know how to avoid system effect factors System Effects, Slide 3

Two Components of System Design l Calculate flow resistance losses for each component in the system l Select and position fan to avoid system effect loss è If loss cannot be avoided, estimate loss and select fan for higher pressure System Effects, Slide 4

Ductwork Example System Effect Controlled by Inlet and Outlet Conditions System Resistance System Effects, Slide 5

Causes of Non-Performing Systems l System resistance miscalculated. l Fan not properly selected. l Defective fan (or fan rating). l There is a system effect loss. System Effects, Slide 6

Fan Manufacturer’s Responsibility l Provide accurate fan performance ratings. l Provide a fan built within tolerance so that it is capable of meeting its rating. System Effects, Slide 7

What is System Effect? l A factor used to correct for system induced installation effects. l The difference in performance between a fan tested in the laboratory and one tested in a real installation. System Effects, Slide 8

Inlet Connections ASHRAE Guidelines System Effects, Slide 9

Outlet Connections ASHRAE Guidelines System Effects, Slide 10

Outlet Connections ASHRAE Guidelines System Effects, Slide 11

What is Missing? l Only guidelines to avoid losses. l No way to quantify losses. System Effects, Slide 12

AMCA Publication 201 -02 l The bible of system effects l Generated from ASHRAE funded research System Effects, Slide 13

Credibility Gap l Are system effects just fudge factors that the fan manufacturers made up? l System effect video. System Effects, Slide 14

Definition of System Effect l Fan ratings are established using AMCA 210 test codes that are close to ideal conditions. l Fans in actual systems are often less than ideal. l The difference in performance for the same fan tested in both conditions is the “System Effect”. System Effects, Slide 15

Purpose of Discussion l Aimed primarily at the fan system designer There are two goals: l Avoid poor fan system configurations l When optimum conditions cannot be met, use the “system effect” factors to estimate any losses during system design. System Effects, Slide 16

Why System Effect is Important l May have to accept deficient performance, or. . . è Speed up the fan (if possible) è May require more energy to meet performance è May exceed motor horsepower limit l Many cause excessive noise l Many cause excessive vibration System Effects, Slide 17

Normal System Performance 1 Calculated duct system curve Fan curve Design volume System Effects, Slide 18

Deficient Performance With System Effect System effect at actual flow volume l Operating point is at point 3 è Operating point is not on fan curve! 4 1 3 Calculated duct system with no allowance for system effect Original fan curve Design volume Deficient volume System Effects, Slide 19

Correcting For System Effect System effect at actual flow volume 2 Actual duct system with system effect Calculated duct system with no allowance for system effect System effect loss at design volume 4 1 3 New fan curve Original fan curve Design volume Deficient volume System Effects, Slide 20

With System Effects Added: l The fan will be selected for the higher pressure (no need to speed up). l The motor will be selected to include the anticipated loss. System Effects, Slide 21

What are the Causes of the Losses? l Inlet losses are caused by: è Unequal loading of the fan blades (eccentric flow). è Improper fan blade attack angle. è Turbulence which disrupts the flow. l Outlet losses are caused by: è Loss of conversion of local high velocity into pressure. System Effects, Slide 22

Inlet vs. Outlet Losses l Inlet induced losses tend to be higher than outlet losses. l Losses induced on the inlet can often exceed 20%. l Losses as high as 50% have been reported. System Effects, Slide 23

Good Flow Conditions for a Fan: l Straight uniform flow directed only in the axial direction--on the fan inlet l For Ducted fans - a straight length of outlet ductwork System Effects, Slide 24

AMCA Publication 210 -07 Defines standard methods of testing fans for rating purposes System Effects, Slide 26

How are the Losses Quantified? l AMCA 201 publishes data for a variety of configurations l Most identify a “Loss Curve” which is based on the configuration and identified by a letter è Most also need the air velocity as a parameter. System Effects, Slide 27

System Effect Curves Curve T Add 0. 55 to Static Pressure 4000 FPM System Effects, Slide 28

Outlet System Effects l In addition to the flow velocity, may need to know: è effective duct length è blast area System Effects, Slide 29

System Effect Curves for Outlet Ducts Axial Fans System Effects, Slide 30

Fan Outlet Velocity Profile - Centrifugal System Effects, Slide 31

System Effect Curves for Outlet Ducts Centrifugal Fans System Effects, Slide 32

Outlet Duct Elbows - Centrifugal Fans WORSE BAD System Effects, Slide 33

S. E. Curves for Outlet Elbows on Centrif. System Effects, Slide 34

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S. E. Curves for Outlet Elbows - Axial System Effects, Slide 36

S. E. Curves for Inlet Elbows - Axial System Effects, Slide 37

Percentage of Unobstructed Inlet Area System Effects, Slide 38

Fans and Plenum – Two Losses Distance L / (Inlet Dia. ) gives one loss Loss factors given for 0. 3 to 0. 75 clearance Keep inlet centerline on centerline of unit Note: Spacing for two fans is important No loss factors given System Effects, Slide 39

Elbows Change the Velocity Profile Fan inlet here will create a system effect loss for any type of fan System Effects, Slide 40

Right Angle Turns At Fan Inlet with 3 -piece elbow Inlet with rectangular inlet Duct (POOR) Inlet with special designed inlet box All methods will induce some system effect loss. Some methods are better than others System Effects, Slide 41

System Effect - Round Inlet Ducts System Effect Curves R/D No 2 D Duct -- N 5 D Du ct P R-S No 2 D Duct 0. 5 O Q 0. 75 Q 1. 0 S R/D No 2 D Duct 5 D Duct 0. 5 P-Q R-S T-U 0. 75 Q-R S U R S-T U-V 1. 0 R S-T U-V 2. 0 R-S T U-V 3. 0 S T-U V 3. 0 S-T U V- D Length of Duct 5 D Duct System Effect Curves D Length of Duct R R R 2 piece mitered round section 3 piece mitered round section 4 or more piece mitered round section System Effects, Slide 42

Forced Inlet Vortex (Inlet Spin or Swirl) Pre-Rotating Inlet Swirl Counter-Rotating Inlet Swirl System Effects, Slide 43

Corrections for Inlet Spin System Effects, Slide 44

Normalized Pressure-Volume Curve Note that this is similar to a variable system effect. A new curve is generated at each vane setting System Effects, Slide 46

Pressure Drop Multipliers for Volume Control Dampers on a Fan Outlet System Effects, Slide 47

Measured Inlet Sound Power Vaneaxial Fan System Effect Blade Pass - 135 Hz System Effects, Slide 48

System Effect Factors are Real l When designing your fan/system, do everything possible to avoid a “system effect” for efficient use of energy l When conditions leading to system effect cannot be avoided, add the calculated loss to the fan pressure requirement at the system design stage. System Effects, Slide 49

Thumb Rules l Minimum of 2 -1/2 Duct Diameters on Outlet, l Minimum 3 to 5 Duct Diameters on Inlet, and l Avoid Inlet Swirl System Effects, Slide 50

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Questions? System Effects, Slide 59

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