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Training Session on EnergyTraining Session on Energy
EquipmentEquipment
Fans & BlowersFans & Blowers
Presentation from the
“Energy Efficiency Guide for Industry in Asia”
www.energyefficiencyasia.org
©© UNEP 2006UNEP 2006
ElectricalEquipment
Fans&Blowers
2
©© UNEP 2006UNEP 2006
Training Agenda: Fans & BlowersTraining Agenda: Fans & Blowers
Introduction
Types of fans and blowers
Assessment of fans and blowers
Energy efficiency opportunities
ElectricalEquipment
Fans&Blowers
3
IntroductionIntroductionElectricalEquipment
Fans&Blowers
©© UNEP 2006UNEP 2006
1. Fan components
2. System resistance
3. Fan curve
4. Operating point
5. Fan laws
4
IntroductionIntroduction
Fan Components
ElectricalEquipment
Fans&Blowers
Outlet
Diffusers
Baffles
Heat
Exchanger
Turning Vanes
(typically used on
short radius
elbows)
Variable Frequency
DriveMotor
Centrifugal
Fan
Inlet
Vanes
Filter
Belt Drive
Motor
Controller
©© UNEP 2006UNEP 2006
(US DOE, 1989)
Provide air for ventilation and
industrial processes that need air flow
5
IntroductionIntroduction
System Resistance
ElectricalEquipment
Fans&Blowers
©© UNEP 2006UNEP 2006
• Sum of static pressure losses in
system
• Configuration of ducts, pickups, elbows
• Pressure drop across equipment
• Increases with square of air volume
• Long narrow ducts, many bends: more
resistance
• Large ducts, few bends: less resistance
6
IntroductionIntroduction
System Resistance
ElectricalEquipment
Fans&Blowers
©© UNEP 2006UNEP 2006
System resistance curve for various
flows
(US DOE, 1989)
calculated
Actual with
system
resistance
7
IntroductionIntroduction
Fan Curve
ElectricalEquipment
Fans&Blowers
©© UNEP 2006UNEP 2006
Performance curve of fan under
specific conditions
• Fan volume
• System static
pressure
• Fan speed
• Brake
horsepower
(US DOE, 1989)
8
IntroductionIntroduction
Operating Point
ElectricalEquipment
Fans&Blowers
©© UNEP 2006UNEP 2006
Fan curve and system curve intersect
Flow Q1 at
pressure P1 and
fan speed N1
Move to flow Q2
by reducing fan
speed
Move to flow Q2
by closing damper
(increase system
resistance)
(BEE India, 2004)
9
IntroductionIntroduction
Fan Laws
ElectricalEquipment
Fans&Blowers
©© UNEP 2006UNEP 2006(BEE India, 2004)
10
©© UNEP 2006UNEP 2006
Training Agenda: Fans & BlowersTraining Agenda: Fans & Blowers
Introduction
Types of fans and blowers
Assessment of fans and blowers
Energy efficiency opportunities
ElectricalEquipment
Fans&Blowers
11
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
Types of fans
• Centrifugal
• Axial
Types of blowers
• Centrifugal
• Positive displacement
ElectricalEquipment
Fans&Blowers
12
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
• Rotating impeller increases air velocity
• Air speed is converted to pressure
• High pressures for harsh conditions
• High temperatures
• Moist/dirty air streams
• Material handling
• Categorized by blade shapes
• Radial
• Forward curved
• Backward inclined
Centrifugal Fans
ElectricalEquipment
Fans&Blowers
13
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
Centrifugal Fans – Radial fans
ElectricalEquipment
Fans&Blowers
• Advantages
• High pressure and temp
• Simple design
• High durability
• Efficiency up to 75%
• Large running clearances
• Disadvantages
• Suited for low/medium
airflow rates only
(Canadian Blower)
14
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
Centrifugal Fans – Forward curved
ElectricalEquipment
Fans&Blowers
•Advantages
• Large air volumes against
low pressure
• Relative small size
• Low noise level
•Disadvantages
• Not high pressure / harsh
service
• Difficult to adjust fan output
• Careful driver selection
• Low energy efficiency 55-65%
( Canadian Blower)
15
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
Centrifugal Fans - Backward-inclined
ElectricalEquipment
Fans&Blowers
• Advantages
• Operates with changing
static pressure
• Suited for high flow and
forced draft services
• Efficiency >85%
• Disadvantages
• Not suited for dirty airstreams
• Instability and erosion risk
( Canadian Blower)
16
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
• Work like airplane propeller:
• Blades create aerodynamic lift
• Air is pressurized
• Air moves along fan axis
• Popular with industry: compact, low
cost and light weight
• Applications
• Ventilation (requires reverse airflow)
• Exhausts (dust, smoke, steam)
Axial Fans
ElectricalEquipment
Fans&Blowers
17
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
Axial Fans – Propeller fans
ElectricalEquipment
Fans&Blowers
• Advantages
• High airflow at low pressure
• Little ductwork
• Inexpensive
• Suited for rooftop
ventilation
• Reverse flow
• Disadvantages
• Low energy efficiency
• Noisy
(Fan air Company)
18
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
Axial Fans – Tube axial fans
ElectricalEquipment
Fans&Blowers
(Canadian Blower)
• Advantages
• High pressures to overcome
duct losses
• Suited for medium-pressure,
high airflow rates
• Quick acceleration
• Space efficient
• Disadvantages
• Expensive
• Moderate noise
• Low energy efficiency 65%
19
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
Axial Fans – Vane axial fans
ElectricalEquipment
Fans&Blowers
(Canadian Blower)
• Advantages
• Suited for medium/high
pressures
• Quick acceleration
• Suited for direct motor shaft
connection
• Most energy efficient 85%
• Disadvantages
• Expensive
20
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
Blowers
ElectricalEquipment
Fans&Blowers
• Difference with fans
• Much higher pressures <1.20 kg/cm2
• Used to produce negative pressures for
industrial vacuum systems
• Types
• Centrifugal blower
• Positive displacement
21
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
Centrifugal Blowers
ElectricalEquipment
Fans&Blowers
• Gear-driven impeller
that accelerates air
• Single and multi-stage
blowers
• Operate at 0.35-0.70
kg/cm2 pressure
• Airflow drops if system
pressure rises
(Fan air Company)
22
©© UNEP 2006UNEP 2006
Types of Fans & BlowersTypes of Fans & Blowers
Positive Displacement Blowers
ElectricalEquipment
Fans&Blowers
• Rotors trap air and push it through
housing
• Constant air volume regardless of
system pressure
• Suited for applications prone to
clogging
• Turn slower than centrifugal blowers
• Belt-driven for speed changes
23
©© UNEP 2006UNEP 2006
Training Agenda: Fans & BlowersTraining Agenda: Fans & Blowers
Introduction
Types of fans and blowers
Assessment of fans and blowers
Energy efficiency opportunities
ElectricalEquipment
Fans&Blowers
24
©© UNEP 2006UNEP 2006
Assessment of fans and blowersAssessment of fans and blowers
• Fan efficiency:
• Ratio of the power conveyed to air stream
and power delivered by the motor to the fan
• Depends on type of fan and impeller
• Fan performance curve
• Graph of different pressures and
corresponding required power
• Supplier by manufacturers
Fan Efficiency and Performance
ElectricalEquipment
Fans&Blowers
25
©© UNEP 2005UNEP 2005
Assessment of fans and blowersAssessment of fans and blowers
Peak efficiency or Best Efficiency
Point (BEP)
ElectricalEquipment
Fans&Blowers
©© UNEP 2006UNEP 2006(BEE India, 2004)
Airfoil
Tubular
Forward
Efficiency
Flow rate
Backward
Radial
Airfoil
Tubular
Forward
Efficiency
Flow rate
Backward
Radial
Type of Fan
Peak
Efficiency
Range
Centrifugal fans:
Airfoil, Backward
curved/inclined
79-83
Modified radial 72-79
Radial 69-75
Pressure blower 58-68
Forward curved 60-65
Axial fans:
Vane axial 78-85
Tube axial 67-72
Propeller 45-50
26
©© UNEP 2006UNEP 2006
Assessment of fans and blowersAssessment of fans and blowers
Before calculating fan efficiency
• Measure operating parameters
• Air velocity, pressure head, air stream temp,
electrical motor input
• Ensure that
• Fan is operating at rated speed
• Operations are at stable condition
Methodology – fan efficiency
ElectricalEquipment
Fans&Blowers
27
©© UNEP 2006UNEP 2006
Assessment of fans and blowersAssessment of fans and blowers
Step 1: Calculate air/gas density
Step 2: Measure air velocity and
calculate average
Step 3: Calculate the volumetric
flow in the duct
Methodology – fan efficiency
ElectricalEquipment
Fans&Blowers
t = Temperature of air/gas
at site condition
Cp = Pitot tube constant,
0.85 (or) as given by the
manufacturer
∆p = Average differential
pressure
γ = Density of air or gas at
test condition
28
©© UNEP 2006UNEP 2006
Assessment of fans and blowersAssessment of fans and blowers
Step 4: Measure the power drive of the motor
Step 5: Calculate fan efficiency
• Fan mechanical efficiency
• Fan static efficiency
Methodology – fan efficiency
ElectricalEquipment
Fans&Blowers
29
©© UNEP 2006UNEP 2006
Assessment of fans and blowersAssessment of fans and blowers
• Non-availability of fan specification
data
• Difficulty in velocity measurement
• Improper calibration of instruments
• Variation of process parameters
during tests
Difficulties in Performance
Assessment
ElectricalEquipment
Fans&Blowers
30
©© UNEP 2006UNEP 2006
Training Agenda: Fans & BlowersTraining Agenda: Fans & Blowers
Introduction
Types of fans and blowers
Assessment of fans and blowers
Energy efficiency opportunities
ElectricalEquipment
Fans&Blowers
31
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
1. Choose the right fan
2. Reduce the system resistance
3. Operate close to BEP
4. Maintain fans regularly
5. Control the fan air flow
32
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
• Considerations for fan selection
• Noise
• Rotational speed
• Air stream characteristics
• Temperature range
• Variations in operating conditions
• Space constraints and system layout
• Purchase/operating costs and operating life
• “Systems approach” most important!
1. Choose the Right Fan
33
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
• Avoid buying oversized fans
• Do not operate at Best Efficiency Point
• Risk of unstable operation
• Excess flow energy
• High airflow noise
• Stress on fan and system
1. Choose the Right Fan
34
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
• Increased system resistance
reduces fan efficiency
2. Reduce the System Resistance
• Check periodically
• Check after system
modifications
• Reduce where
possible
(BEE India, 2004)
35
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
• Best Efficiency Point = maximum
efficiency
• Normally close to rated fan capacity
• Deviation from BEP results in
inefficiency and energy loss
3. Operate Close to BEP
36
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
• Periodic inspection of all system
components
• Bearing lubrication and replacement
• Belt tightening and replacement
• Motor repair or replacement
• Fan cleaning
4. Maintain Fans Regularly
37
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
a) Pulley change
b) Dampers
c) Inlet guide vanes
d) Variable pitch fans
e) Variable speed drives (VSD)
f) Multiple speed drive
g) Disc throttle
h) Operating fans in parallel
i) Operating fans in series
5. Control the Fan Air flow
38
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
a) Pulley change: reduce motor/drive
pulley size
• Advantages
• Permanent speed
decrease
• Real energy reduction
• Disadvantages
• Fan must handle capacity change
• Only applicable if V-belt system or motor
5. Control the Fan Air flow
(BEE India, 2004)
39
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
b) Dampers: reduce flow and increase
upstream pressure
• Advantages
• Inexpensive
• Easy to install
• Disadvantages
• Limited adjustment
• Reduce flow but not energy consumption
• Higher operating and maintenance costs
5. Control the Fan Air flow
40
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
c) Inlet guide vanes
• Create swirls in fan direction
• Reduce angle air and fan blades
• Lowering fan load, pressure, air flow
• Advantages
• Improve efficiency: reduced load and airflow
• Cost effective at 80-100% of full air flow
• Disadvantage
• Less efficient at <80% of full air flow
5. Control the Fan Air flow
41
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
d) Variable pitch fans: changes angle
incoming airflow and blades
• Advantages
• High efficiency at range of operating conditions
• No resonance problems
• No stall problems at different flows
• Disadvantages
• Applicable to axial fans only
• Risk of fouling problems
• Reduced efficiency at low loads
5. Control the Fan Air flow
42
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
e) Variable speed drives (VSDs): reduce
fan speed and air flow
• Two types
• Mechanical VSDs
• Electrical VSDs (including VFDs)
• Advantages
• Most improved and efficient speed control
• Speed adjustments over continuous range
• Disadvantage: high costs
5. Control the Fan Air flow
43
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
e) Variable frequency drives
• Change motor’s rotational speed by
adjusting electrical frequency of power
• Advantages
• Effective and easy flow control
• Improved efficiency over wide operating range
• Can be retrofitted to existing motors
• Compactness
• No fouling problems
• Reduced energy losses and costs
5. Control the Fan Air flow
44
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
f) Multiple speed drive
• Changes fan speed from one speed to
other speed
• Advantages
• Efficient control of flow
• Suitable if only 2 speeds required
• Disadvantages
• Need to jump from speed to speed
• High investment costs
5. Control the Fan Air flow
45
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
g) Disc throttle:
Sliding throttle that changes width of
impeller exposed to air stream
• Advantages
• Simple design
• Disadvantages
• Feasible in some applications only
5. Control the Fan Air flow
46
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
h) Operate more fans in parallel (instead
of one large fan)
• Advantages
• High efficiencies at varying demand
• Risk of downtime avoided
• Less expensive and better performance than
one large fan
• Can be equipped with other flow controls
• Disadvantages
• Only suited for low resistance system
5. Control the Fan Air flow
47
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
i) Operate fans in series
• Advantages
• Lower average duct pressure
• Less noise
• Lower structural / electrical support required
• Disadvantages
• Not suited for low resistance systems
5. Control the Fan Air flow
48
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
5. Controlling the Fan Air Flow
Comparing
Fans in
Parallel
and Series
(BEE India, 2004)
49
©© UNEP 2006UNEP 2006
Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment
Fans&Blowers
(BEE India, 2004)
5. Controlling the Fan Air Flow
Comparing
the impact of
different types
of flow control
on power use
50
Training Session on EnergyTraining Session on Energy
EquipmentEquipment
Fans & BlowersFans & Blowers
THANK YOUTHANK YOU
FOR YOUR ATTENTIONFOR YOUR ATTENTION
©© UNEP 2006UNEP 2006
ElectricalEquipment
Fans&Blowers

51
ElectricalEquipment/
FansandBlowers
© UNEP 2006© UNEP 2006
Disclaimer and ReferencesDisclaimer and References
• This PowerPoint training session was prepared as part of
the project “Greenhouse Gas Emission Reduction from
Industry in Asia and the Pacific” (GERIAP). While
reasonable efforts have been made to ensure that the
contents of this publication are factually correct and
properly referenced, UNEP does not accept responsibility
for the accuracy or completeness of the contents, and shall
not be liable for any loss or damage that may be occasioned
directly or indirectly through the use of, or reliance on, the
contents of this publication. © UNEP, 2006.
• The GERIAP project was funded by the Swedish
International Development Cooperation Agency (Sida)
• Full references are included in the textbook chapter that is
available on www.energyefficiencyasia.org

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energy efficient operation of Fans and blowers

  • 1. 1 Training Session on EnergyTraining Session on Energy EquipmentEquipment Fans & BlowersFans & Blowers Presentation from the “Energy Efficiency Guide for Industry in Asia” www.energyefficiencyasia.org ©© UNEP 2006UNEP 2006 ElectricalEquipment Fans&Blowers
  • 2. 2 ©© UNEP 2006UNEP 2006 Training Agenda: Fans & BlowersTraining Agenda: Fans & Blowers Introduction Types of fans and blowers Assessment of fans and blowers Energy efficiency opportunities ElectricalEquipment Fans&Blowers
  • 3. 3 IntroductionIntroductionElectricalEquipment Fans&Blowers ©© UNEP 2006UNEP 2006 1. Fan components 2. System resistance 3. Fan curve 4. Operating point 5. Fan laws
  • 4. 4 IntroductionIntroduction Fan Components ElectricalEquipment Fans&Blowers Outlet Diffusers Baffles Heat Exchanger Turning Vanes (typically used on short radius elbows) Variable Frequency DriveMotor Centrifugal Fan Inlet Vanes Filter Belt Drive Motor Controller ©© UNEP 2006UNEP 2006 (US DOE, 1989) Provide air for ventilation and industrial processes that need air flow
  • 5. 5 IntroductionIntroduction System Resistance ElectricalEquipment Fans&Blowers ©© UNEP 2006UNEP 2006 • Sum of static pressure losses in system • Configuration of ducts, pickups, elbows • Pressure drop across equipment • Increases with square of air volume • Long narrow ducts, many bends: more resistance • Large ducts, few bends: less resistance
  • 6. 6 IntroductionIntroduction System Resistance ElectricalEquipment Fans&Blowers ©© UNEP 2006UNEP 2006 System resistance curve for various flows (US DOE, 1989) calculated Actual with system resistance
  • 7. 7 IntroductionIntroduction Fan Curve ElectricalEquipment Fans&Blowers ©© UNEP 2006UNEP 2006 Performance curve of fan under specific conditions • Fan volume • System static pressure • Fan speed • Brake horsepower (US DOE, 1989)
  • 8. 8 IntroductionIntroduction Operating Point ElectricalEquipment Fans&Blowers ©© UNEP 2006UNEP 2006 Fan curve and system curve intersect Flow Q1 at pressure P1 and fan speed N1 Move to flow Q2 by reducing fan speed Move to flow Q2 by closing damper (increase system resistance) (BEE India, 2004)
  • 10. 10 ©© UNEP 2006UNEP 2006 Training Agenda: Fans & BlowersTraining Agenda: Fans & Blowers Introduction Types of fans and blowers Assessment of fans and blowers Energy efficiency opportunities ElectricalEquipment Fans&Blowers
  • 11. 11 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers Types of fans • Centrifugal • Axial Types of blowers • Centrifugal • Positive displacement ElectricalEquipment Fans&Blowers
  • 12. 12 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers • Rotating impeller increases air velocity • Air speed is converted to pressure • High pressures for harsh conditions • High temperatures • Moist/dirty air streams • Material handling • Categorized by blade shapes • Radial • Forward curved • Backward inclined Centrifugal Fans ElectricalEquipment Fans&Blowers
  • 13. 13 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers Centrifugal Fans – Radial fans ElectricalEquipment Fans&Blowers • Advantages • High pressure and temp • Simple design • High durability • Efficiency up to 75% • Large running clearances • Disadvantages • Suited for low/medium airflow rates only (Canadian Blower)
  • 14. 14 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers Centrifugal Fans – Forward curved ElectricalEquipment Fans&Blowers •Advantages • Large air volumes against low pressure • Relative small size • Low noise level •Disadvantages • Not high pressure / harsh service • Difficult to adjust fan output • Careful driver selection • Low energy efficiency 55-65% ( Canadian Blower)
  • 15. 15 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers Centrifugal Fans - Backward-inclined ElectricalEquipment Fans&Blowers • Advantages • Operates with changing static pressure • Suited for high flow and forced draft services • Efficiency >85% • Disadvantages • Not suited for dirty airstreams • Instability and erosion risk ( Canadian Blower)
  • 16. 16 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers • Work like airplane propeller: • Blades create aerodynamic lift • Air is pressurized • Air moves along fan axis • Popular with industry: compact, low cost and light weight • Applications • Ventilation (requires reverse airflow) • Exhausts (dust, smoke, steam) Axial Fans ElectricalEquipment Fans&Blowers
  • 17. 17 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers Axial Fans – Propeller fans ElectricalEquipment Fans&Blowers • Advantages • High airflow at low pressure • Little ductwork • Inexpensive • Suited for rooftop ventilation • Reverse flow • Disadvantages • Low energy efficiency • Noisy (Fan air Company)
  • 18. 18 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers Axial Fans – Tube axial fans ElectricalEquipment Fans&Blowers (Canadian Blower) • Advantages • High pressures to overcome duct losses • Suited for medium-pressure, high airflow rates • Quick acceleration • Space efficient • Disadvantages • Expensive • Moderate noise • Low energy efficiency 65%
  • 19. 19 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers Axial Fans – Vane axial fans ElectricalEquipment Fans&Blowers (Canadian Blower) • Advantages • Suited for medium/high pressures • Quick acceleration • Suited for direct motor shaft connection • Most energy efficient 85% • Disadvantages • Expensive
  • 20. 20 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers Blowers ElectricalEquipment Fans&Blowers • Difference with fans • Much higher pressures <1.20 kg/cm2 • Used to produce negative pressures for industrial vacuum systems • Types • Centrifugal blower • Positive displacement
  • 21. 21 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers Centrifugal Blowers ElectricalEquipment Fans&Blowers • Gear-driven impeller that accelerates air • Single and multi-stage blowers • Operate at 0.35-0.70 kg/cm2 pressure • Airflow drops if system pressure rises (Fan air Company)
  • 22. 22 ©© UNEP 2006UNEP 2006 Types of Fans & BlowersTypes of Fans & Blowers Positive Displacement Blowers ElectricalEquipment Fans&Blowers • Rotors trap air and push it through housing • Constant air volume regardless of system pressure • Suited for applications prone to clogging • Turn slower than centrifugal blowers • Belt-driven for speed changes
  • 23. 23 ©© UNEP 2006UNEP 2006 Training Agenda: Fans & BlowersTraining Agenda: Fans & Blowers Introduction Types of fans and blowers Assessment of fans and blowers Energy efficiency opportunities ElectricalEquipment Fans&Blowers
  • 24. 24 ©© UNEP 2006UNEP 2006 Assessment of fans and blowersAssessment of fans and blowers • Fan efficiency: • Ratio of the power conveyed to air stream and power delivered by the motor to the fan • Depends on type of fan and impeller • Fan performance curve • Graph of different pressures and corresponding required power • Supplier by manufacturers Fan Efficiency and Performance ElectricalEquipment Fans&Blowers
  • 25. 25 ©© UNEP 2005UNEP 2005 Assessment of fans and blowersAssessment of fans and blowers Peak efficiency or Best Efficiency Point (BEP) ElectricalEquipment Fans&Blowers ©© UNEP 2006UNEP 2006(BEE India, 2004) Airfoil Tubular Forward Efficiency Flow rate Backward Radial Airfoil Tubular Forward Efficiency Flow rate Backward Radial Type of Fan Peak Efficiency Range Centrifugal fans: Airfoil, Backward curved/inclined 79-83 Modified radial 72-79 Radial 69-75 Pressure blower 58-68 Forward curved 60-65 Axial fans: Vane axial 78-85 Tube axial 67-72 Propeller 45-50
  • 26. 26 ©© UNEP 2006UNEP 2006 Assessment of fans and blowersAssessment of fans and blowers Before calculating fan efficiency • Measure operating parameters • Air velocity, pressure head, air stream temp, electrical motor input • Ensure that • Fan is operating at rated speed • Operations are at stable condition Methodology – fan efficiency ElectricalEquipment Fans&Blowers
  • 27. 27 ©© UNEP 2006UNEP 2006 Assessment of fans and blowersAssessment of fans and blowers Step 1: Calculate air/gas density Step 2: Measure air velocity and calculate average Step 3: Calculate the volumetric flow in the duct Methodology – fan efficiency ElectricalEquipment Fans&Blowers t = Temperature of air/gas at site condition Cp = Pitot tube constant, 0.85 (or) as given by the manufacturer ∆p = Average differential pressure γ = Density of air or gas at test condition
  • 28. 28 ©© UNEP 2006UNEP 2006 Assessment of fans and blowersAssessment of fans and blowers Step 4: Measure the power drive of the motor Step 5: Calculate fan efficiency • Fan mechanical efficiency • Fan static efficiency Methodology – fan efficiency ElectricalEquipment Fans&Blowers
  • 29. 29 ©© UNEP 2006UNEP 2006 Assessment of fans and blowersAssessment of fans and blowers • Non-availability of fan specification data • Difficulty in velocity measurement • Improper calibration of instruments • Variation of process parameters during tests Difficulties in Performance Assessment ElectricalEquipment Fans&Blowers
  • 30. 30 ©© UNEP 2006UNEP 2006 Training Agenda: Fans & BlowersTraining Agenda: Fans & Blowers Introduction Types of fans and blowers Assessment of fans and blowers Energy efficiency opportunities ElectricalEquipment Fans&Blowers
  • 31. 31 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers 1. Choose the right fan 2. Reduce the system resistance 3. Operate close to BEP 4. Maintain fans regularly 5. Control the fan air flow
  • 32. 32 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers • Considerations for fan selection • Noise • Rotational speed • Air stream characteristics • Temperature range • Variations in operating conditions • Space constraints and system layout • Purchase/operating costs and operating life • “Systems approach” most important! 1. Choose the Right Fan
  • 33. 33 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers • Avoid buying oversized fans • Do not operate at Best Efficiency Point • Risk of unstable operation • Excess flow energy • High airflow noise • Stress on fan and system 1. Choose the Right Fan
  • 34. 34 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers • Increased system resistance reduces fan efficiency 2. Reduce the System Resistance • Check periodically • Check after system modifications • Reduce where possible (BEE India, 2004)
  • 35. 35 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers • Best Efficiency Point = maximum efficiency • Normally close to rated fan capacity • Deviation from BEP results in inefficiency and energy loss 3. Operate Close to BEP
  • 36. 36 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers • Periodic inspection of all system components • Bearing lubrication and replacement • Belt tightening and replacement • Motor repair or replacement • Fan cleaning 4. Maintain Fans Regularly
  • 37. 37 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers a) Pulley change b) Dampers c) Inlet guide vanes d) Variable pitch fans e) Variable speed drives (VSD) f) Multiple speed drive g) Disc throttle h) Operating fans in parallel i) Operating fans in series 5. Control the Fan Air flow
  • 38. 38 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers a) Pulley change: reduce motor/drive pulley size • Advantages • Permanent speed decrease • Real energy reduction • Disadvantages • Fan must handle capacity change • Only applicable if V-belt system or motor 5. Control the Fan Air flow (BEE India, 2004)
  • 39. 39 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers b) Dampers: reduce flow and increase upstream pressure • Advantages • Inexpensive • Easy to install • Disadvantages • Limited adjustment • Reduce flow but not energy consumption • Higher operating and maintenance costs 5. Control the Fan Air flow
  • 40. 40 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers c) Inlet guide vanes • Create swirls in fan direction • Reduce angle air and fan blades • Lowering fan load, pressure, air flow • Advantages • Improve efficiency: reduced load and airflow • Cost effective at 80-100% of full air flow • Disadvantage • Less efficient at <80% of full air flow 5. Control the Fan Air flow
  • 41. 41 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers d) Variable pitch fans: changes angle incoming airflow and blades • Advantages • High efficiency at range of operating conditions • No resonance problems • No stall problems at different flows • Disadvantages • Applicable to axial fans only • Risk of fouling problems • Reduced efficiency at low loads 5. Control the Fan Air flow
  • 42. 42 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers e) Variable speed drives (VSDs): reduce fan speed and air flow • Two types • Mechanical VSDs • Electrical VSDs (including VFDs) • Advantages • Most improved and efficient speed control • Speed adjustments over continuous range • Disadvantage: high costs 5. Control the Fan Air flow
  • 43. 43 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers e) Variable frequency drives • Change motor’s rotational speed by adjusting electrical frequency of power • Advantages • Effective and easy flow control • Improved efficiency over wide operating range • Can be retrofitted to existing motors • Compactness • No fouling problems • Reduced energy losses and costs 5. Control the Fan Air flow
  • 44. 44 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers f) Multiple speed drive • Changes fan speed from one speed to other speed • Advantages • Efficient control of flow • Suitable if only 2 speeds required • Disadvantages • Need to jump from speed to speed • High investment costs 5. Control the Fan Air flow
  • 45. 45 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers g) Disc throttle: Sliding throttle that changes width of impeller exposed to air stream • Advantages • Simple design • Disadvantages • Feasible in some applications only 5. Control the Fan Air flow
  • 46. 46 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers h) Operate more fans in parallel (instead of one large fan) • Advantages • High efficiencies at varying demand • Risk of downtime avoided • Less expensive and better performance than one large fan • Can be equipped with other flow controls • Disadvantages • Only suited for low resistance system 5. Control the Fan Air flow
  • 47. 47 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers i) Operate fans in series • Advantages • Lower average duct pressure • Less noise • Lower structural / electrical support required • Disadvantages • Not suited for low resistance systems 5. Control the Fan Air flow
  • 48. 48 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers 5. Controlling the Fan Air Flow Comparing Fans in Parallel and Series (BEE India, 2004)
  • 49. 49 ©© UNEP 2006UNEP 2006 Energy Efficiency OpportunitiesEnergy Efficiency OpportunitiesElectricalEquipment Fans&Blowers (BEE India, 2004) 5. Controlling the Fan Air Flow Comparing the impact of different types of flow control on power use
  • 50. 50 Training Session on EnergyTraining Session on Energy EquipmentEquipment Fans & BlowersFans & Blowers THANK YOUTHANK YOU FOR YOUR ATTENTIONFOR YOUR ATTENTION ©© UNEP 2006UNEP 2006 ElectricalEquipment Fans&Blowers 
  • 51. 51 ElectricalEquipment/ FansandBlowers © UNEP 2006© UNEP 2006 Disclaimer and ReferencesDisclaimer and References • This PowerPoint training session was prepared as part of the project “Greenhouse Gas Emission Reduction from Industry in Asia and the Pacific” (GERIAP). While reasonable efforts have been made to ensure that the contents of this publication are factually correct and properly referenced, UNEP does not accept responsibility for the accuracy or completeness of the contents, and shall not be liable for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the contents of this publication. © UNEP, 2006. • The GERIAP project was funded by the Swedish International Development Cooperation Agency (Sida) • Full references are included in the textbook chapter that is available on www.energyefficiencyasia.org

Editor's Notes

  1. TO THE TRAINER This PowerPoint presentation can be used to train people about the basics of fans and blowers. The information on the slides is the minimum information that should be explained. The trainer notes for each slide provide more detailed information, but it is up to the trainer to decide if and how much of this information is presented also. Additional materials that can be used for the training session are available on www.energyefficiencyasia.org under “Energy Equipment” and include: Textbook chapter on this energy equipment that forms the basis of this PowerPoint presentation but has more detailed information Quiz – ten multiple choice questions that trainees can answer after the training session Workshop exercise – a practical calculation related to this equipment Option checklist – a list of the most important options to improve energy efficiency of this equipment Company case studies – participants of past courses have given the feedback that they would like to hear about options implemented at companies for each energy equipment. More than 200 examples are available from 44 companies in the cement, steel, chemicals, ceramics and pulp &amp; paper sectors
  2. We will first explain the fan components and go through some important theory about system and fan characteristics
  3. Most manufacturing plants use fans and blowers for ventilation and for industrial processes that need an air flow. Fan systems are essential to keep manufacturing processes working Fans and blowers are differentiated by the method used to move the air, and by the system pressure they must operate against. A typical fan system consists consist of a fan, an electric motor, a drive system, ducts or piping, flow control devices, and air conditioning equipment (filters, cooling coils, heat exchangers, etc.)
  4. The term “system resistance” is used when referring to the static pressure. The system resistance is the sum of static pressure losses in the system. The system resistance is a function of the configuration of ducts, pickups, elbows and the pressure drops across equipment, for example bag filter or cyclone. The system resistance varies with the square of the volume of air flowing through the system. For a given volume of air, the fan in a system with narrow ducts and multiple short radius elbows is going to have to work harder to overcome a greater system resistance than it would in a system with larger ducts and a minimum number of long radius turns.
  5. To determine what volume the fan will produce, it is therefore necessary to know the system resistance characteristics. In existing systems, the system resistance can be measured. In systems that have been designed, but not built, the system resistance must be calculated. Typically a system resistance curve (see Figure) is generated with for various flow rates on the x-axis and the associated resistance on the y-axis. The calculated or expected system curve in this figure has higher flow rates for a given flow rate than the actual system curve. This is due to the system resistance.
  6. Fan characteristics can be represented in form of fan curve(s). The fan curve is a performance curve for the particular fan under a specific set of conditions, usually including: fan volume, system static pressure, fan speed, and brake horsepower required to drive the fan under the stated conditions.
  7. This system curve can then be plotted on the fan curve to show the fan&amp;apos;s actual operating point at &amp;quot;A&amp;quot; where the two curves (N1 and SC1) intersect. The fan&amp;apos;s actual operating point on this curve will depend on the system resistance. In this figure, the fan’s operating point at “A” is flow (Q1) against pressure (P1). Two methods can be used to reduce air flow from Q1 to Q2: (Click once) The first method is to restrict the air flow by partially closing a damper in the system. This action causes a new system performance curve (SC2) where the required pressure is greater for any given air flow. The fan will now operate at &amp;quot;B&amp;quot; to provide the reduced air flow Q2 against higher pressure P2. (Click once) The second method to reduce air flow is by reducing the speed from N1 to N2, keeping the damper fully open. The fan would operate at &amp;quot;C&amp;quot; to provide the same Q2 air flow, but at a lower pressure P3. Thus, reducing the fan speed is a much more efficient method to decrease airflow since less power is required.
  8. The relationship between the fan speed on one hand, and the air flow, pressure and power requirements is described by fan laws. (Click once) The speed is directly correlated with the air flow. For example, if the speed is increased by 10%, then the air flow also increases by 10% (Click once) When the speed is increased then the pressure SP increases much more, as shown in the graph and formula. For example, a 10% speed increase results in a 21% pressure increase (Click once) When the speed is increased then the power kW increases most, as shown in the graph and formula. For example, if the speed is increased by 10%, then the power requirement increases by 33%
  9. This section briefly describes about different types of fans and blowers.
  10. There exist two main fan types. Centrifugal fans used a rotating impeller to move the air stream. Axial fans move the air stream along the axis of the fan. The centrifugal blower and the positive displacement blower are two main types of blowers. These are described next.
  11. Centrifugal fans increase the speed of an air stream with a rotating impeller. The speed increases as the reaches the ends of the blades and is then converted to pressure. These fans are able to produce high pressures, which makes them suitable for harsh operating conditions, such as systems with high temperatures, moist or dirty air streams, and material handling. Centrifugal fans are categorized by their blade shapes.
  12. Radial fans, with flat blades Advantages: Suitable for high static pressures (up to 1400 mmWC) and high temperatures Simple design allows custom build units for special applications Can operate at low air flows without vibration problems High durability Efficiencies up to 75% Have large running clearances, which is useful for airborne-solids (dust, wood chips and metal scraps) handling services Disadvantages: Only suitable for low-medium airflow rates
  13. Forward curved fans, with forward curved blades Advantages: Can move large air volumes against relatively low pressure Relative small size Low noise level (due to low speed) and well suited for residential heating, ventilation, and air conditioning (HVAC) applications Disadvantages: Only suitable for clean service applications but not for high pressure and harsh services Fan output is difficult to adjust accurately Driver must be selected carefully to avoid motor overload because power curve increases steadily with airflow Relatively low energy efficiency (55-65%)
  14. Backward inclined fan, with blades that tilt away from the direction of rotation: flat, curved, and airfoil Advantages: Can operate with changing static pressure (as this does not overload the motor) Suitable when system behavior at high air flow is uncertain Suitable for forced-draft services Flat bladed fans are more robust Curved blades fans are more efficient (exceeding 85%) Thin air-foil blades fans are most efficient Disadvantages: Not suitable for dirty air streams (as fan shape promotes accumulation of dust) Airfoil blades fans are less stable because of staff as they rely on the lift created by each blade Thin airfoil blades fans subject to erosion
  15. Axial fans move an air stream along the axis of the fan. The way these fans work can be compared to a propeller on an airplane: the fan blades generate an aerodynamic lift that pressurizes the air. They are popular with industry because they are inexpensive, compact and light. Although the fans are typically designed to generate flow in one direction, they can operate in the reverse direction too. This characteristic is useful when a space may require contaminated air to be exhausted or fresh air to be supplied. Axial fans are frequently used in exhaust applications where airborne particulate size is small, such as dust streams, smoke, and steam. Axial fans are also useful in ventilation applications that require the ability to generate reverse airflow.
  16. Propeller fan (Figure 11) Advantages: Generate high airflow rates at low pressures Not combined with extensive ductwork (because the generate little pressure) Inexpensive because of their simple construction Achieve maximum efficiency, near-free delivery, and are often used in rooftop ventilation applications Can generate flow in reverse direction, which is helpful in ventilation applications Disadvantages: Relative low energy efficiency Comparatively noisy
  17. Tube-axial fan, essentially a propeller fan placed inside a cylinder (Figure 12) Advantages: Higher pressures and better operating efficiencies than propeller fans Suited for medium-pressure, high airflow rate applications, e.g. ducted HVAC installations Can quickly accelerate to rated speed (because of their low rotating mass) and generate flow in reverse direction, which is useful in many ventilation applications Create sufficient pressure to overcome duct losses and are relatively space efficient, which is useful for exhaust applications Disadvantages: Relatively expensive Moderate airflow noise Relatively low energy efficiency (65%)
  18. Vane-axial fan (Figure 13) Advantages: Suited for medium- to high-pressure applications (up to 500 mmWC), such as induced draft service for a boiler exhaust Can quickly accelerate to rated speech (because of their low rotating mass) and generate flow in reverse directions, which is useful in many ventilation applications Suited for direct connection to motor shafts Most energy efficient (up to 85% if equipped with airfoil fans and small clearances) Disadvantages: Relatively expensive compared to propeller fans
  19. Blowers can achieve much higher pressures than fans, as high as 1.20 kg/cm2. They are also used to produce negative pressures for industrial vacuum systems. The centrifugal blower and the positive displacement blower are two main types of blowers, which are described next
  20. Centrifugal blowers look more like centrifugal pumps than fans. The impeller is typically gear-driven and rotates as fast as 15,000 rpm. In multi-stage blowers, air is accelerated as it passes through each impeller. In single-stage blower, air does not take many turns, and hence it is more efficient. Centrifugal blowers typically operate against pressures of 0.35 to 0.70 kg/cm2, but can achieve higher pressures. One characteristic is that airflow tends to drop drastically as system pressure increases, which can be a disadvantage in material conveying systems that depend on a steady air volume. Because of this, they are most often used in applications that are not prone to clogging.
  21. Positive Displacement Positive displacement blowers have rotors, which &amp;quot;trap&amp;quot; air and push it through housing. These blowers provide a constant volume of air even if the system pressure varies. They are especially suitable for applications prone to clogging, since they can produce enough pressure (typically up to 1.25 kg/cm2) to blow clogged materials free. They turn much slower than centrifugal blowers (e.g. 3,600 rpm) and are often belt driven to facilitate speed changes.
  22. Fan efficiency is the ratio between the power transferred to the air stream and the power delivered by the motor to the fan. The power of the airflow is the product of the pressure and the flow, corrected for unit consistency. The fan efficiency depends on the type of fan and impeller. (Click once) We already discussed the fan performance curve earlier: a graph that shows the different pressures developed by the fan and the corresponding required power. The manufacturers normally provide these fan performance curves. Understanding this relationship is essential to designing, sourcing, and operating a fan system and is the key to optimum fan selection.
  23. As the flow rate increases, the efficiency increases to certain height (“peak efficiency”) and then decreases with further increasing flow rate. (Point at the peak of one of the curves) The peak efficiency is also called the Best Efficiency Point (BEP) The peak efficiency ranges for different types of centrifugal and axial fans are given in the Table.
  24. Before the fan efficiency can be calculated, a number of operating parameters must be measured, including air velocity, pressure head, temperature of air stream on the fan side and electrical motor kW input. In order to obtain correct operating figures it should be ensured that: Fan and its associated components are operating properly at its rated speed Operations are at stable condition i.e. steady temperature, densities, system resistance etc.
  25. The calculation of fan efficiency is explained in 5 steps. (Click once) Step 1. The first step is to calculate the air or gas density using the given equation (Click once) Step 2. The air velocity can be measured with a pitot tube and a manometer, or a flow sensor (differential pressure instrument), or an accurate anemometer. Calculate the average air velocity by taking number of velocity pressure readings across the cross-section of the duct using the given equation, where Cp is the pitot tube constant of 0.85 or as given by the manufacturer, and p is the average differential pressure. (Click once) Step 3. Take the duct diameter (or the circumference from which the diameter can be estimated). Next, calculate the volume of air/gas in the duct by using the given formula
  26. Step 4. The power of the drive motor (kW) can be measured by a load analyzer. This kW multiplied by motor efficiency gives the shaft power to the fan. (Click once) Step 5. Now the fan’s mechanical and static efficiencies can be calculated using these equations
  27. In practice certain difficulties have to be faced when assessing the fan and blower performance, some of which are explained below: Non-availability of fan specification data: Fan specification data (see Worksheet 1) are essential to assess the fan performance. Most of the industries do not keep these data systematically or have none of these data available at all. In these cases, the percentage of fan loading with respect to flow or pressure can not be estimated satisfactorily. Fan specification data should be collected from the original equipment manufacturer (OEM) and kept on record. Difficulty in velocity measurement: Actual velocity measurement becomes a difficult task in fan performance assessment. In most cases the location of duct makes it difficult to take measurements and in other cases it becomes impossible to traverse the duct in both directions. If this is the case, then the velocity pressure can be measured in the center of the duct and corrected by multiplying it with a factor 0.9. Improper calibration of the pitot tube, manometer, anemometer &amp; measuring instruments: All instruments and other power measuring instruments should be calibrated correctly to avoid an incorrect assessment of fans and blowers. Assessment should not be carried out by applying correction factors to compensate for this. Variation of process parameters during tests: If there is a large variation of process parameters measured during test periods, then the performance assessment becomes unreliable.
  28. There are five main areas for energy conservation for fans which we will discuss on the next slides.
  29. Important considerations when selecting a fan are: Noise Rotational speed Air stream characteristics Temperature range Variations in operating conditions Space constraints and system layout Purchase costs, operating costs (determined by efficiency and maintenance), and operating life But as a general rule it is important to know that to effectively improve the performance of fan systems, designers and operators must understand how other system components function as well. The “systems approach” requires knowing the interaction between fans, the equipment that supports fan operation, and the components that are served by fans. The use of a “systems approach” in the fan selection process will result in a quieter, more efficient, and more reliable system.
  30. A common problem is that companies purchase oversized fans for their service requirements. They will not operate at their best efficiency point (BEP) and in extreme cases these fans may operate in an unstable manner because of the point of operation on the fan airflow-pressure curve. Oversized fans generate excess flow energy, resulting in high airflow noise and increased stress on the fan and the system. Consequently, oversized fans not only cost more to purchase and to operate, they create avoidable system performance problems. Possible solutions include, amongst other replacing the fan, replacing the motor, or introducing a variable speed drive motor.
  31. The system resistance curve and the fan curve were explained earlier. The fan operates at a point where the system resistance curve and the fan curve intersects. The system resistance has a major role in determining the performance and efficiency of a fan. In the figure, if the system resistance is increased then the operating point moves from A to B. The result is that the air flow of the fan reduces, and thus the fan efficiency. The system resistance changes Marginally by the formation of the coatings / erosion of the lining in the ducts Drastically, in some cases, due to the change of equipment, duct modifications Hence, the system resistance has to be periodically checked, more so when modifications are introduced and action taken accordingly to reduce the system resistance, for efficient operation of the fan.
  32. It is earlier described that the fan efficiency increases as the flow increases to certain point and thereafter it decreases. The point at which maximum efficiency is obtained is called the peak efficiency or “Best Efficiency Point” (BEP). Normally it is closer to the rated capacity of the fan at a particular designed speed and system resistance. Deviation from the BEP will result in increased loss and inefficiency.
  33. Regular maintenance of fans is important to maintain their performance levels. Maintenance activities include: Periodic inspection of all system components Bearing lubrication and replacement Belt tightening and replacement Motor repair or replacement Fan cleaning
  34. Pulley change: reduces the motor / drive pulley size (Click once) Advantages: Permanent speed decrease Real energy reduction (Explain the figure: a 2 inch reduction in pulley, from 8 inch to 6 inch, results in 12 kW savings) Disadvantages: Fan must be able to handle capacity change Fan must be driven by V-belt system or motor
  35. Dampers: reduce the amount of flow and increases the upstream pressure, which reduces fan output (Click once) Advantages: Inexpensive Easy to install Disadvantages: Provide a limited amount of adjustment Reduce the flow but not the energy consumption Higher operating and maintenance costs
  36. Inlet Guide vanes: Inlet guide vanes: create swirls in the fan direction thereby lessening the angle between incoming air and fan blades, and thus lowering fan load, pressure and airflow (Click once) Advantages: Improve fan efficiency because both fan load and delivered airflow are reduced Cost effective at airflows between 80-100% of full flow Disadvantages: Less efficient at airflows lower than 80% of full flow
  37. Variable-pitch fans Change the angle between incoming airflow and the blade by tilting the fan blades, thereby reducing both the motor load and airflow (Click once) Advantages: Can keep fan efficiency high over a range of operating conditions. Avoid resonance problems as normal operating speed is maintained Can operate from a no-flow to a full-flow condition without stall problems Disadvantages: Applicable to some axial fan types only Fouling problems if contaminants accumulate in the mechanical actuator that controls the blades Operating at low loads for long periods reduces the power factor and motor efficiency, thus loosing efficiency advantages and risking low power factor charge from the utility
  38. Variable Speed Drive (VSD): reducing the speed of the fan to meet reduced flow requirements Mechanical VSDs: hydraulic clutches, fluid couplings, and adjustable belts and pulleys Electrical VSDs: eddy current clutches, wound-rotor motor controllers, and variable frequency drives (VFDs: change motor’s rotational speed by adjusting electrical frequency of power supplied) (Click once) Advantages: Most improved and efficient flow control Allow fan speed adjustments over a continuous range Disadvantages: Mechanical VSDs have fouling problems Investment costs can be a barrier
  39. Variable frequency drives (VFDs) VFDs are the most commonly used type of electrical VSD used Change motor’s rotational speed by adjusting electrical frequency of power supplied (Click once) Advantages for VFDs specifically: Effective and easy flow control Improve fan operating efficiency over a wide range of operating conditions Can be retrofitted to existing motors Compactness No fouling problems Reduce energy losses and costs by lowering overall system flow
  40. Multiple speed drive (Click once) Advantages Efficient control of flow Suitable if only two fixed speeds are required Disadvantages Need to jump from speed to speed Investment costs can be a barrier
  41. Disc throttle: a sliding throttle that changes the width of the impeller that is exposed to the air stream (Click once) Advantages: Simple design Disadvantages: Feasible in some applications only
  42. Operate fans in parallel: two or more fans in parallel instead of one large one (Click once) Advantages: High efficiencies across wide variations in system demand Redundancy to mitigate the risk of downtime because of failure or unexpected maintenance Two smaller fans are less expensive and offer better performance than one relatively large one Can be equipped with other flow controls to increase flexibility and reliability Disadvantages: Should only be used when the fans can operate in a low resistance almost in a free delivery condition
  43. Operate fans in series: using multiple fans in a push-pull arrangement (Click once) Advantages: Lower average duct pressure Lower noise generation Lower structural and electrical support requirements Suited for systems with long ducts, large pressure drops across system components, or high resistances Disadvantages: Not suited for low resistance systems
  44. This figure compares the fan curves of fans in series in fans in parallel (Click once) The fan curve of two fans in series starts high but drops rapidly. At the point where the fan curve meets the High Resistance System curve, i.e. the operating point, the flow is much higher than that of a single fan. In other words, the efficiency gain is significant. But at the operating point in a Low Resistance System, the flow is low and practically the same as that of a single fan. This is why fans in series are not suited for low resistance systems (Click once) For fans in parallel we see exactly the opposite. The fan curve of two fans in parallel does not start high but drops much slower. In a High Resistance System the operating point is only slightly higher than that of a single fan. In other words, the efficiency gain in a High Resistance System is minimal. But in a Low Resistance System the operating point of two fans in parallel is relatively high. This is why fans in parallel are suited for low resistance systems.
  45. This figure shows how some types of flow control are more effective in reducing power consumption than others. For example, let’s compare the use of outlet vanes and speed control (Click once) Outlet vanes reduce the flow of air but not the fan speed, and therefore not the power consumption. At a 50% of full air flow, the power consumption is still close to 100% of full load power. (Click once) Speed control with VSDs reduces the flow by reducing the speed and therefore the power consumption. At a 50% of full air flow, the power consumption has reduced to about 25% of full load power.