Day 3: Fans and Pumps

Fans & Pumps
ADNAN JOUNI

RCREEE EnERgy Audit
in Building
tunis, 1st – 5th JunE
2010

1

Contents

1 General Introduction
2 Fans & Blowers
3 Pumps & Pumping systems

2

General Introduction

Pumps and fans are probably
the devices the most frequently
used in our life
Both are necessary to move
material and energy

3

General Introduction
In building sector their usage is
essential to secure comfort and
welfare
Energy saving concerns 2 levels:
• The device itself
• The removed energy or material

4

Fans & Blowers

Equipment Specific Ratio Pressure rise (mmWg)

Comparison Fans up to 1.11 1136
Blowers 1.11to 1.20 1136 –2066 5

Contents
Introduction
Types of fans and blowers
Energy audit of Fans

6

Introduction
What are Fan systems?
Any device that produces a current of air by the
movement of broad surfaces can be called a fan

Fans are similar in many respects to pumps.
 Both are turbo machines that transfer energy to a
flowing fluid.
It is easy to distinguish between fans and pumps:
pumps handle liquids; fans handle gasses.
Broadly speaking, the function of a fan is to propel,
displace, or move air or gas.
7

Introduction

Fan components
System resistance
Fan curve
Operating point
Fan laws

8

Introduction
Fan Network Components
Turning Vanes
(typically used on
short radius
elbows)
Outlet
Diffusers

Heat
Exchanger
Baffles

Filter Inlet
Vanes
Motor
Controller

Variable Frequency
Drive
Centrifugal Fan
Belt Drive Motor
9

Introduction
System Resistance:
• Sum of static pressure losses in system
• Increases with square of flow rate

Actual with
system
resistance

calculated

10

Introduction
Fan Curves

11

Introduction
Operating Point
Fan curve and system curve intersection
Move to flow Q2
by closing Flow Q1 at
damper (increase pressure P1 and
system fan speed N1
resistance)

Move to flow Q2
by reducing fan
speed
12

Introduction
Fan Laws
Minimizing Energy through Fan selection
Fan Affinity Laws

Pre.

13

Contents

Introduction

Energy Audit of Fans

14

Types of Fans & Blowers
Peak Efficiency
Type of Fan Range

Types of fans Centrifugal fans:

Airfoil, Backward 79-83
• Centrifugal curved/inclined

Modified radial 72-79

• Axial Radial 69-75

Pressure blower 58-68

Forward curved 60-65

Types of blowers Axial fans:

Vane axial 78-85
• Centrifugal Tube axial 67-72

Propeller 45-50
• Positive displacement
15


Centrifugal Fans

• Advantages
• High pressure and temp
• Simple design
• High durability
• Efficiency up to 75%
• Large running
clearances
• Disadvantages
• Suited for low/medium
airflow rates only 16

Types of Centrifugal Fans

17

Example of Centrifugal Fans
Backward-inclined
• 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
18


Axial Fans
• Work like airplane propeller:
• Blades create aerodynamic lift
• Air is pressurized
• Air moves along fan axis

• Popular : compact, low cost and light weight
• Applications
• Ventilation (requires reverse airflow)
• Exhausts (dust, smoke, steam)
19


Example of Axial Fans – Tube axial fans
• Advantages
• Pressures to overcome duct
losses
• Suited for medium-pressure,
high airflow rates
• Quick acceleration

• Disadvantages
• Expensive
• Moderate noise
• Low energy efficiency 65%
20


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

Contents

Introduction


22

Introduction
Example for the distribution of
cost over the life cycle of fans
Fans are the
main consumer Maintenance
Capital
(5%)
for auxiliary 8%)
Systems
In Most situations
the potential of
Energy Saving is
Energy
more than 30% (87%)
23


Steps Involved
Data collection
Observations and Analysis
Exploration for energy
conservation measures
Report preparation

24

Data Collection
Collect detailed design specification & operating
parameters: Make, Type, Model, Fluid characteristics,
Rated Flow, Inlet pressure, Efficiency, motor
characteristics, Regulation systems,
Collect Details of the fans and ducting system:
 Collect the schematic diagram / network of the ducting system
 Collect Performance characteristics of all fans
 Compile design, previous best and last energy audit values with
respect to fans and draft system
 If the fans are operated in parallel then it is advised to collect the
performance curve for the parallel operation
 Air quality and pressure equipments at the users as per the design
requirements
25

Instruments Required
Power Analyzer: Used for measuring electrical parameters such
as kW, kVA, pf, V, A and Hz
Temperature Indicator & Probe
Stroboscope: To measure the speed of the driven equipment
and motor
Sling hygrometer or digital hygrometer
Anemometer, Pitot tubes
On line instruments – (calibrated)
Digital Manometer of suitable range and appropriate probes for
measurement of pressure head and velocity head.
Additional pressure gauges with appropriate range of
measurement and calibrated before audit.
26

Measurements & observations to be made

Energy consumption pattern of fans
Motor electrical parameters (kW, kVA, Pf, A, V, Hz,)
of fans
Fan operating parameters to be
measured/monitored for each Fan are:
1. Discharge flow rate
2. Pressure (suction & discharge)

27

Measurements & observations to be made
3. Damper position / guide vane position/ VSD Setting
4. Temperature of fluid handled
5. Load variation
6. Fan operating hours and operating schedule
7. Pressure drop in the system
8. Pressure drop and temperature variation across the
equipment
9. Fan /Motor speed

Oxygen content, flow, temperature and pressure
measurement across in exhaust gas path
28

Energy consumption pattern
If the plant is monitoring the energy consumption, it
is suggested to record the data and monitor the daily
and monthly consumption pattern. (Collect data for 12
months)
 Work out the total consumption of fans to arrive at
percentage to the total consumption of the auxiliary
consumption
 If the energy meters are not installed to fans,
instantaneous measurements can be carried out,
based on the loading pattern daily consumption can
be worked out.
29

Fan Operating Efficiency Evaluation
The parameters to be studied in detailed are:
 Air /gas rates of fans / main ducts
 Static pressure and dynamic pressure and total
pressure
 Power consumption of fan (for estimating the
operating efficiency of the fans)
 Monitor present flow control system and frequency of
control valve operation if any (for application of variable
speed drives)

30

Fans Performance assessment
• Static pressure
– Potential energy put into the system by the fan
• Velocity pressure
– Pressure arising from air flowing through the duct.
This is used to calculate velocity
• Total pressure
– Static pressure + velocity pressure
– Total pressure remains constant unlike static and
velocity pressure

31

Fan static kW = Q in m3/ s x static pr. developed by fan in mmwc
102
Fan static kW x 100
Fan static efficiency % =
Input kW to motor x ηm
Fan mechanical Efficiency % = Fan total kW x 100
Input kW to motor x ηm
Parameter Details Unit
Q Air flow rate m3/ s
Static pressure Difference between discharge & suction pressure mmwc
Fan static/ total kW Static / total power consumption of the fan kW
Input kW to motor Measured power consumption of the motor kW
ηm Efficiency of the motor at operating load
Total pressure Difference between discharge & suction pressure mmwc
34

273 X 1.293
Corrected air density, γ =
273 + Air temperature in 0 C

Cp x √2 x 9.81 x Diff. velocity pr. in mmwc x γ
Velocity in m / s =
γ
Cp Pitot tube constant 0.85 or as given
by manufacturer
γ Density of air or gas at test condition Kg / m3

Volumetric flow (Q), m3/s = Velocity, m/s x Area, m2
35

Fan Performance Analysis
Compare the actual values with the design / performance test values if
any deviation is found, list the factors with the details and
suggestions to over come.
 The investigations for abnormality are to be carried out for
problems.
 Enlist scope of improvement with extensive physical checks /
observations.
 Based on the actual operating parameters, enlist recommendations
for action to be taken for improvement, if applicable such as-
Replacement of fans, Impeller replacement, VFD application.
Cost analysis with savings potential for taking improvement
measures.

36


Recirculation

Damper
100
P
IGV
o 75 Inlet Guide Vanes
w
e 50
r
VFD
25 Variable Frequency Drive

Ideal

25 50 75 100
Flow 37


System characteristics and Fan curves Impact of speed reduction
38


Visual survey of insulation & the ducting system:

 Insulation status (measure the surface temperature with the
aid of surface thermocouple / infrared pyrometer or by using
thermal imaging cameras)
 Bends and ducting status
 Physical condition of insulation
 Identification of locations where action is required to
improve the insulation (provide with detailed techno-
economics)
 Improvement options for ducting systems if any
39

Exploration of Energy Conservation Opportunities
Improvement of systems and drives:
 Use of energy efficient fans
 Change of impeller with energy efficient impeller
 Correcting inaccuracies of the fan sizing
 Use of high efficiency motors
 Fan speed reduction by pulley diameter modifications for optimization
 Option of two speed motors or variable speed drives for variable duty
conditions
 High Performance Lubricants: The low temperature fluidity and high
temperature stability of high performance lubricants can increase energy
efficiency by reducing frictional losses
 Use of energy efficient transmission systems (Use of latest energy
40
efficient transmission belts)

Exploration of Energy Conservation Opportunities
Improvement in operations:
 Minimizing excess air level in combustion systems to reduce fan
load.
 Minimizing air in-leaks in hot or cold flue gas path to reduce fan
load
 Minimizing system resistance and pressure drops
 improvements in duct system / Insulation aspects
Measures to up keep the performance
After the identification of energy conservation measures, detailed
techno-economic evaluation has to be carried out

41

Case Study
A fan is used to draw air through a bag filter.
􀂃 Flow rate is 90 m3/s at a static pressure of 80 mm water column
(WC)
􀂃 65 mm WC is the static pressure across the bag filter
􀂃 Motor power drawn is 120 kW
􀂃 Motor efficiency is 86%
􀂃 Impeller diameter is 70 mm
􀂃 RPM is 1000

After consultation we decided to replace the bag filter with an
electrostatic precipitator (ESP).
􀂃 Static pressure across the ESP is 20 mm WC
􀂃 Flow rate increased by 20%
􀂃 The flow rate can be brought back to 90 m3/s by two options: (a)
Impeller trimming and (b) Reduced pulley diameter to reduce the RPM 42

Case Study

We must Calculate the following:
1. Fan static efficiency before installation of the ESP
2. The new impeller diameter if the impeller is
trimmed, that would result in a reduction in fan
efficiency of 5%
3. The new RPM that would result in a fan
efficiency of 60%
4. Which of the two options is more energy efficient

43

Case Study
1. Fan static efficiency before installation of the ESP
Power input at fan shaft = 120 x 0.86 = 103.2 kW
Fan efficiency = 90 x 80/(102 x 103.2) = 68 %
2 New impeller diameter if the impeller is trimmed
New fan static efficiency = 68% - 5% = 63%
New static = 80 – 65 + 20 = 35 mm WC
New flow rate Q = 90 m3/s x 1.2 = 108 m3/s
Static pressure at a flow of 90 m3/s with ESP installed
Q1 / Q2 = (H1/H2)2 result H2 = 32 mm
Power required at the fan shaft
Fan static efficiency: 0.63 = (90 x 32) / (102 x power)
Power developed at fan shaft = 44.8 kW
New impeller diameter (D2) 44
(D1 / D2) = (kW1 / kW2) 1/ 3 result D2 = 53 mm

Case Study
3. Calculate the new RPM that would result in a fan efficiency
of 60%
Power required at fan shaft
0.60 = 90 x 32 / 102 x Power required at fan shaft
Power required at fan shaft = 47 kW
New RPM (N2): (N1 / N2) = (kW1 / kW2) 1/ 3
N2 = 769 RPM
4. Determine which of the two options is more energy efficient
Power required by impeller trimming = 44.8 kW
Power required by reducing RPM = 47 kW
Therefore impeller trimming is the more energy efficient option.

45

Contents

Introduction
Type of pumps
Energy Audit of Pumps

47

Introduction

What are Pumping Systems
• 20% of world’s electrical energy demand
• Used for
• Domestic, commercial, industrial and agricultural
services
• Municipal water and wastewater services

48

Introduction

Objective of pumping system

• Transfer liquid
from source to
destination
• Circulate liquid
around a system

49

Introduction

• Main pump components
• Pumps
• Prime movers: electric motors, diesel engines,
air system
• Piping to carry fluid
• Valves to control flow in system
• Other fittings, control, instrumentation
• End-use equipment
• Heat exchangers, tanks, hydraulic machines 50

Introduction
Pumping System Characteristics
• Head
• Resistance of the system
• Two types: static and friction
• Static head
• Difference in height between
source and destination
• Independent of flow
• Static head at certain pressure

Head (m) = Pressure (Pa)
1000xSpecific gravity
51

Introduction

In most cases:
Total head = Static head + friction head

• Friction head
• Resistance in pipe and fittings System
curve
• Depends on size, pipes, pipe System
fittings, flow rate, nature of liquid head Friction
head
• Proportional to square of flow
rate Static head

Flow
52

Introduction
Pump performance curve
Relationship between head and
Pump operating point flow

Pump performance
curve
• Duty point: rate of
flow at certain head Pump
operating
• Pump operating Head System point
curve
point: intersection
of pump curve and Static
system curve head

Flow
53

Introduction
Pump suction performance
• Cavitation or vaporization: bubbles inside pump
• If vapor bubbles collapse
• Erosion of vane surfaces
• Increased noise and vibration
• Choking of impeller passages
• Net Positive Suction Head (NPSH)
• NPSH Available: how much pump suction
exceeds liquid vapor pressure
• NPSH Required: pump suction needed to avoid
cavitation 54

Introduction

Pumping System Characteristic curves

55

Introduction

Pumps in parallel: Curves

56

Contents: Pumps

Introduction

Type of pumps

57

Type of Pumps

Pump Classification
Classified by operating principle

Pumps

Others (e.g. Positive
Dynamic Impulse, Buoyancy) Displacement

Centrifugal Special effect Rotary Reciprocating

Internal External Slide
Lobe
gear gear vane 58

Type of Pumps

Positive Displacement Pumps
• For each pump revolution
• Fixed amount of liquid taken from one end
• Positively discharged at other end

• If pipe blocked
• Pressure rises
• Can damage pump

• Used for pumping fluids other than
water 59

Type of Pumps

Dynamic pumps
• Mode of operation
• Rotating impeller converts kinetic energy into
pressure or velocity to pump the fluid

• Two types
• Centrifugal pumps: pumping water in
industry – 75% of pumps installed
• Special effect pumps: specialized conditions

60

Type of Pumps
Centrifugal Pumps

How do they work?

• Liquid forced into impeller
• Vanes pass kinetic energy
to liquid: liquid rotates and
leaves impeller
• Volute casing converts
kinetic energy into
pressure energy 61

Type of Pumps

Centrifugal Pumps

Impeller

• Main rotating part that provides centrifugal
acceleration to the fluid
• Number of impellers = number of pump stages
• Impeller classification: direction of flow, suction
type and shape/mechanical construction

Shaft
• Transfers torque from motor to impeller during
pump start up and operation
62

Contents: Pumps

Introduction
Type of pumps


64

Introduction

Example for the distribution
of cost over the life cycle of a Maintenance
Capital
water-based pump system. (5%)
10%)

In Most
situations the
potential of
Energy Saving is Energy
more than 30% (85%)
65


Steps Involved
Data collection
Observations and Analysis
Exploration for energy
conservation measures
Report preparation

66

Data Collection
Collect detailed design specification & operating
parameters: Make, Type, Model, Fluid
characteristics, Rated Flow, Inlet pressure,
Efficiency, motor characteristics, Regulation
systems
Collect the above information for all pumps in the
water circuit
Collect the Performance Characteristics curves of
all pumps
67

Data Collection
Compile design, previous best and last energy audit values
of the pumping system being audited
 If the pumps are operated in parallel, then it is advised to
collect the performance curves for the parallel operation of the
pumps
 Schematic diagram of Water pumping network (which
depict the source, pumps in operation & stand by, line sizes
and users)
 Water and pressure equipments at the users as per the
design requirements
 Brief description of the system, in which pumps are used 68

Instruments Required
 Power Analyzer: Used for measuring electrical
parameters such as kW, kVA, pf, V, A and Hz
 Temperature Indicator & Probe
 Pressure Gauge: To measure operating pressure and
pressure drop in the system
 Stroboscope: To measure the speed of the driven
equipment and motor
 Ultra sonic flow meter or online flow meter
 The above instruments can be used in addition to the
calibrated online / plant instruments 69

Parameters to be measured
 Energy consumption pattern of pumps (daily / monthly
/yearly consumption)
 Motor electrical parameters (kW, kVA, Pf, A, V, Hz) for
individual pumps
 Pump operating parameters to be monitored for each pump
Discharge Flow, Head (suction & discharge), Valve position,
Temperature, Load variation, Simultaneous power
parameters of pumps, Pumps operating hours and operating
schedule, Pressure drop in the system (between discharge
and user point), Pressure drop and temperatures across the
users (heat exchangers, condensers, etc), Pump /Motor
speed, Actual discharge pressure and required / prevailing
pressure at the user end, User area pressure of operation and 70

Observations & Measurements
 Operating efficiency and performance evaluation of pumps
 Flow distribution
 System Details: Detailed interactions (plant personnel) have to
be carried out to get familiarization for system detail and
operational details. The brief system should be briefed in the
report
 Energy consumption Pattern: If the plant is monitoring the
energy consumption, it is suggested to record the data and
monitor the daily and monthly consumption pattern
 Collect the past energy consumption data (month wise for at
least 12 months, daily consumption for about a week for different
seasons, daily Consumption during the audit period)
71

Efficiency & Performance Evaluation of the Pumps

Performance parameters for water pumps

72

Performance parameters for water pumps contd..

73


Pump hydraulic power can be calculated by the formula:
Q x Total Head, (hd – hs) x ρ x g
Hydraulic kW =
1000
Q Water flow rate m3/s
Total head Difference between discharge head, hd & suction head, hs m
ρ Density of water or fluid being pumped Kg/m3
g Acceleration due to gravity m2/s

Hydraulic power
Pump efficiency, ηPump =
Pump shaft power

Pump shaft power = Hydraulic power x η Motor 74


75

Energy Conservation Opportunities
 Compare the actual values with the design / performance test values if
any deviation is found, list the factors with the details and suggestions to
over come.
 Compare the specific energy consumption with the best achievable
value (considering the different alternatives). Investigations to be carried
out for problematic areas..
 Enlist scope of improvement with extensive physical checks /
observations. Based on the actual operating parameters, enlist
recommendations for action to be taken for improvement, if applicable
such as:
 Replacement of pumps
 Impeller replacement
 Impeller trimming
 Variable speed drive application, etc
76

Avoiding Over sizing of Pump
Pump Curve at
Const. Speed Pump Efficiency 77%

70 m Partially B Oversize Pump
82%
closed valve
A
50 m
Full open valve
42 m
System Curves C Required Pump
Head
Meters
Static Operating Points
Head
300 500
Flow (m3/hr) 77


Avoiding Over sizing of Pump by impeller
trimming 28.6 kW

14.8 kW

78

Provision of variable speed drive

79

 Improvement of systems and drives.
 Use of energy efficient pumps
 Replacement of inefficient pumps
 Trimming of impellers
 Correcting inaccuracies of the Pump sizing
 Use of high efficiency motors
 Integration of variable speed drives into pumps
 High Performance Lubricants: lubricants can increase energy efficiency
by reducing frictional losses.
 Booster pump application
 Centralization/ decentralization
 Categorizing according to the pressure requirement
80

Case Study
In a commercial Building a clear water Pump has:

Parameter Design Operating
Flow Q (m³/h) 800 550

Head H (m WC) 55 24
(after delivery valve)
Power P (kW) 160 124

RPM 1485 1485
Water flow rate varies from 500 m³/h to 700 m³/h.
Pump flow rate has been reduced by partially 81
closing the delivery valve. Motor efficiency is

Case Study

1. Calculate the operating efficiency
2. Explain what would be the best option
to obtain the required flow rate
variation
3. Calculate the power savings if the
options suggested under question 2
would reduce the flow rate of the
pump is 550 m³/h
82

Case Study
SOLUTION
1. Calculate the operating efficiency
Efficiency of the pump = (550 x 24 x 9.81) / (3600 x
124 x 0.93)
= 0.3867 = 38.67%
2. Explain what would be the best solution
The pump is operating at a poor efficiency of
38.67% due to throttling of the flow. Since the pump
discharge requirement varies from 500 m³/h to 700
m³/h, the ideal option would be to operate with a
variable speed drive (VSD).
83

Case Study

3. Calculate the power savings
According to affinity laws:
􀂃 Relationship Q and RPM: Q1/Q2 = N1/N2
􀂃 Relationship H and RPM: H1/H2 = (N1/N2)2
􀂃 Relationship P and RPM: P1/P2 = (N1/N2)3
For a flow rate Q1 = 550 m³/h, the reduced speed
of pump (N1 in RPM) would be: N1 = 1021 RPM
Power would be P1 = 52 kW
Power saving = 124 kW - 52 kW = 72 kW

84

Good Practices
GP1:
•A waste-fuelled heating plant fed two networks
which supply an industrial area and a residential
area.
•An analysis of the pumps used to supply
networks showed that the pumps were all run
continuously at high power, although the
pumping power required was often very low.
85

Good Practices

System optimisation measures:
Complete separation of the pumps from the mains supply
when they are switched off
Replacement of existing pumps with smaller, highly
efficient pumps
Use of variable speed drive for operation at adjustable
speeds
Installation of high efficiency motors
Installation of the new pumps and variable speed drive
86


Good Practices

Energy savings and efficiency
parameters
•Electricity savings: 64 % or 325,000 kWh p.a.
•Cost savings: € 32,500 p.a.
•Investment: € 67,000
•Payback period: 2.1 years
•Return on investment: 48 %
87


Good Practices
GP2:
•A combined heat and power plant provides a district
(houses, hospitals, welfare and handicapped facilities,
commercial kitchen and a laundry ) heat via a district
heating network.
•The energy audit focused on the optimization of the
main district heating pumps in the power supply centre.
The analysis showed considerable potential to optimize
the pump control system, which until now has been
regulated by hand.
88


Good Practices

Systems optimisation measures:
•Hydraulic alignment of the district heating network
•Installation of a proportional control system for the
pumps
•Use of variable speed drive for operation at
adjustable speeds
•Replacement of the two network pumps
•Use of high efficiency motors
89


Good Practices

Energy savings and efficiency
parameters
•Electricity savings: 39 % or 129,000 kWh p.a.
•Cost savings: € 14,100 p.a.
•Investment: € 41,700
•Payback period: 3 years
•Return on investment: 31 %
90

THANK YOU
FOR
YOUR ATTENTION

91

Day 3: Fans and Pumps

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Editor's Notes