Fans And Blowers

Training Session on Energy Equipment E i t

Fans & Blowers Presentation from the “Energy Efficiency Guide for Industry in Asia” www.energyefficiencyasia.org

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Training Agenda: Fans & Blowers Introduction Types of fans and blowers Assessment of fans and blowers Energy gy efficiency y opportunities pp

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Introduction

1. Fan components p 2. System resistance 3. Fan curve 4 Operating point 4. 5. Fan laws

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Introduction Fan Components Provide air for ventilation and industrial processes that need air flow Turning Vanes (typically used on short radius elbows) Outlet Diffusers

Baffles Filter

Heat Exchanger

Inlet Vanes Motor Controller

(US DOE, 1989)

Centrifugal Belt Drive Fan

Variable Frequency Motor Drive

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Introduction S stem Resistance System • Sum of static pressure losses in system • Configuration of ducts ducts, pickups pickups, elbows • Pressure drop across equipment

• Increases with square of air volume • Long narrow ducts ducts, many bends: more resistance ducts, few bends: less resistance • Large ducts 6 © UNEP 2006

Introduction S stem Resistance System System resistance curve for various flows Actual with system resistance calculated

(US DOE, 1989)

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Introduction Fan Curve C r e Performance curve of fan under specific conditions • Fan volume • System static pressure • Fan speed • Brake horsepower (US DOE, 1989)

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Introduction Operating Point Fan curve and system curve intersect Flow Q1 at pressure P1 and fan speed N1

Move to flow Q2 by closing l i damper d (increase system resistance)) (BEE India, 2004)

Move to flow Q2 by reducing fan speed 9 © UNEP 2006

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Introduction Fan Laws La s

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(BEE India, 2004)

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Training Agenda: Fans & Blowers Introduction Types of fans and blowers Assessment of fans and blowers Energy gy efficiency y opportunities pp

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Types of Fans & Blowers

Types of fans • Centrifugal • Axial A i l Types of blowers • Centrifugal • Positive displacement 24 © UNEP 2006

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Types of Fans & Blowers Centrif gal Fans Centrifugal • Rotating g impeller p increases air velocity y • 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

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Types of Fans & Blowers C t if Centrifugal l Fans F – Radial R di l fans f • 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)

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Types of Fans & Blowers Centrif gal Fans – Forward Centrifugal For ard c curved r ed • Advantages • Large air volumes against low pressure • Relative R l ti small ll size i • Low noise level

• Disadvantages • Not high pressure / harsh service • Difficult to adjust fan output • Careful C f l driver di selection l ti • Low energy efficiency 55-65%

(C Canadian di Bl Blower))

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Types of Fans & Blowers C t if Centrifugal l Fans F - Backward-inclined B k d i li d • 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)

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Types of Fans & Blowers A ial Fans Axial • Work like airplane propeller: • Blades create aerodynamic lift • Air is pressurized • Air moves along fan axis

• Popular with industry: compact, compact low cost and light weight • Applications • Ventilation (requires reverse airflow) • Exhausts (dust, smoke, steam) 35 © UNEP 2006

Types of Fans & Blowers A i l Fans Axial F – Propeller P ll fans f • Advantages • High airflow at low pressure • Little ductwork • Inexpensive • Suited for rooftop ventilation • Reverse flow

• Disadvantages • Low Lo energy energ efficienc efficiency • Noisy

(Fan air Company) 36 © UNEP 2006

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Types of Fans & Blowers A i l Fans Axial F – Tube T b axial i l fans f • Advantages g • 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%

(Canadian Blower) 38 © UNEP 2006

Types of Fans & Blowers Axial Fans – Vane axial fans • Advantages • Suited for medium/high g pressures • Quick acceleration • Suited for direct motor shaft connection • Most energy efficient 85%

• Disadvantages • Expensive

(C (Canadian di Bl Blower)) 39 © UNEP 2006

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Types of Fans & Blowers Blowers • Difference with fans • Much higher pressures <1.20 kg/cm2 • Used to produce negative pressures for industrial vacuum systems y

• Types • Centrifugal blower • Positive displacement 43 © UNEP 2006

Types of Fans & Blowers C t if Centrifugal l Blowers Bl • Gear Gear-driven driven impeller that accelerates air • Single and multi-stage blowers • Operate at 0.35-0.70 kg/cm2 pressure • Airflow drops p if system y pressure rises

(Fan air Company)

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Types of Fans & Blowers Positive Displacement 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

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Training Agenda: Fans & Blowers Introduction Types of fans and blowers Assessment of fans and blowers Energy gy efficiency y opportunities pp

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Assessment of fans and blowers F Efficiency Fan Effi i and d Performance P f • 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 51 © UNEP 2006

Assessment of fans and blowers Peak efficienc efficiency or Best Efficienc Efficiency Point (BEP) Airfoil

Efficiency

Backward

Type of Fan

Peak Efficiency Range

Centrifugal fans:

Radial

Tubular

Airfoil, Backward curved/inclined

79-83

Modified radial

72-79

Radial

69-75

Pressure blower

58-68

Forward curved

60-65

Axial fans:

Forward

Flow rate

Vane axial

78-85

Tube axial

67-72

Propeller

45-50

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(BEE India, 2004)

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Assessment of fans and blowers Methodolog – fan efficiency Methodology efficienc Before calculating fan efficiency • Measure operating parameters • Air velocity, pressure head, air stream temp, electrical motor input

• Ensure that • Fan F is i operating ti att rated t d speed d • Operations are at stable condition 53 © UNEP 2006

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Forced Draft Operation

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Suction Draft Operation

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Assessment of fans and blowers M th d l Methodology – fan f efficiency ffi i Step p 1: Calculate air/gas g density y t = Temperature of air/gas at site condition

C = Pitot Cp Pit t tube t b constant, t t

Step 2: Measure air velocity and calculate average

0.85 (or) as given by the manufacturer

p = Average differential pressure

γ = Density of air or gas at test condition

Step 3: Calculate the volumetric flow in the duct 62 © UNEP 2006

Assessment of fans and blowers M th d l Methodology – fan f efficiency ffi i Step 4: Measure the power drive of the motor Step 5: Calculate fan efficiency •

Fan mechanical efficiency

•

Fan static efficiency 63 © UNEP 2006

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Assessment of fans and blowers Difficulties in Performance ssess e t Assessment • Non-availability of fan specification data • Difficulty in velocity measurement • Improper calibration of instruments • Variation of process parameters during tests 69 © UNEP 2006

Training Agenda: Fans & Blowers Introduction Types of fans and blowers Assessment of fans and blowers Energy gy efficiency y opportunities pp

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Energy Efficiency Opportunities

1 Choose the right fan 1. 2. Reduce the system resistance 3. Operate close to BEP 4. Maintain fans regularly 5 Control the fan air flow 5.

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Energy Efficiency Opportunities 1. Choose the Right Fan • Considerations for fan selection • • • • • • •

Noise Rotational speed Air stream characteristics Temperature range Variations in operating conditions p constraints and system y layout y Space Purchase/operating costs and operating life

• “Systems Systems approach” approach most important! 72 © UNEP 2006

Energy Efficiency Opportunities 1. Choose the Right Fan • Avoid buying oversized fans • Do not operate p at Best Efficiency y Point • Risk of unstable operation • Excess flow energy • High airflow noise • Stress on fan and system

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Energy Efficiency Opportunities 2. Reduce the System Resistance • IIncreased d system t resistance i t reduces fan efficiency • Check periodically • Check after system modifications • Reduce where possible (BEE India, 2004)

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Energy Efficiency Opportunities 3. Operate Close to BEP • Best Efficiency Point = maximum efficiency • Normally close to rated fan capacity • Deviation from BEP results in inefficiency and energy loss

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Energy Efficiency Opportunities 4. Maintain Fans Regularly • Periodic inspection of all system components • Bearing lubrication and replacement • Belt tightening and replacement • Motor repair or replacement • Fan cleaning 76 © UNEP 2006

Energy Efficiency Opportunities 5 Control the Fan Air flo 5. flow a)) b) c) d) e) f)) g) h) i)

Pulley y change g Dampers Inlet guide vanes Variable pitch fans Variable speed drives (VSD) Multiple p speed p drive Disc throttle Operating fans in parallel Operating fans in series

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Energy Efficiency Opportunities 5 Control the Fan Air flo 5. flow a)) Pulley y change: g reduce motor/drive pulley size • Advantages • Permanent speed decrease • Real energy reduction

• Disadvantages Di d t

((BEE India, 2004))

• Fan must handle capacity change • Only O l applicable li bl if V-belt V b lt system t or motor t 78 © UNEP 2006

Energy Efficiency Opportunities 5 Control the Fan Air flo 5. flow b)) Dampers: p 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 79 © UNEP 2006

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Energy Efficiency Opportunities 5 Control the Fan Air flo 5. flow c)) Inlet guide g 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 80 100% of full air flow • Cost effective at 80-100%

• Disadvantage • Less efficient at <80% of full air flow 83 © UNEP 2006

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Energy Efficiency Opportunities 5 Control the Fan Air flo 5. flow d)) Variable p pitch fans: changes g angle g 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

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Energy Efficiency Opportunities 5 Control the Fan Air flo 5. flow e)) Variable speed p 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

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Energy Efficiency Opportunities 5 Control the Fan Air flo 5. flow e)) Variable frequency q y drives • Change motor’s rotational speed by adjusting electrical frequency of power • Advantages g • • • • • •

Effective and easy flow control Improved efficiency over wide operating range Can be retrofitted to existing motors Compactness No fouling problems 94 Reduced energy losses and costs © UNEP 2006

Energy Efficiency Opportunities 5 Control the Fan Air flo 5. flow f)) Multiple p speed p drive • Changes fan speed from one speed to other speed • Advantages g • Efficient control of flow • Suitable if only 2 speeds required

• Disadvantages • Need to jump from speed to speed • High investment costs

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Energy Efficiency Opportunities 5 Control the Fan Air flo 5. flow g) Disc throttle: Sliding throttle that changes width of impeller exposed to air stream • Advantages g • Simple design

• Disadvantages • Feasible in some applications only 103 © UNEP 2006

Energy Efficiency Opportunities 5 Control the Fan Air flo 5. flow h)) Operate p more fans in parallel p (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

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Energy Efficiency Opportunities 5 Control the Fan Air flo 5. flow i) Operate fans in series • Advantages g • Lower average duct pressure • Less noise • Lower structural / electrical support required

• Disadvantages • Not suited for low resistance systems 107 © UNEP 2006

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Energy Efficiency Opportunities 5 Controlling the Fan Air Flow 5. Flo Comparing Fans in Parallel and Series

(BEE India, 2004)

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Energy Efficiency Opportunities 5 Controlling the Fan Air Flow 5. Flo Comparing the impact of different types of flow control on power use

(BEE India, 2004)

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Training Session on Energy Equipment E i t

Fans & Blowers THANK YOU FOR YOUR ATTENTION

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Disclaimer and References • Thi This PowerPoint P P i t training t i i session i was preparedd as partt off the project “Greenhouse Gas Emission Reduction from Industryy in Asia and the Pacific” f (GERIAP). ( ) While reasonable efforts have been made to ensure that the contents of this publication are factually correct and properly referenced, 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 129 available on www.energyefficiencyasia.org © UNEP 2006