2012 

GEC Ghani Workshop 3/23/2012

Important!
This session is approved for 0.2 IACET or 1.5 PDH. 
Many states accept this for Professional Continuing Education. 
To qualify for credit you must:
 Be sure your badge was scanned when you entered the workshop

 Stay for the entire session

 Participate in Question and Answer sessions

 Fill out the Evaluation Form and hand it to the proctor as you leave
out t e a uat o o a d a d t to t e p octo as you ea e

If you are registered in Florida, New York, or North Carolina, you must also
sign the sheets in the back at the end of the session.  Please print your name,
include your registration number, and sign the sheet. 

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2012 GEC Ghani Workshop 3/23/2012

Review of Practices in the District Cooling 
R i f P ti i th Di t i t C li
Systems and Pumping Schemes to Manage the 
Impact on Energy – Burj Khalifa Case Study
Ahmed Abdul Ganhi
Chairman
Allied Consultants
Cairo, Egypt

Learning Objectives
1. Understand distribution systems reliability
2. Determine
Determine distribution system energy running 
distribution system energy running
cost
3. Understand new Middle East techniques in 
District cooling

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United Arab Emirates

Dubai

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2012 GEC Ghani Workshop 3/23/2012

Burj Khalifa

Burj Khalifa

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Burj Khalifa

Burj Khalifa

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2012 GEC Ghani Workshop 3/23/2012

Master Plan
DCP‐1
ASHRAE check Figure 215 Sq.ft/TR DCP
DCP 4
Connected Load 45,700 TR 1
Diversity Factor 94 %
DCP 4
DCP‐4
Plant load 43,000 TR
ASHRAE check Figure 215 Sq.ft/TR
Connected Load 59,500 TR
Diversity Factor 67 %
DCP‐3
ASHRAE check Figure Plant load 40,000 TR
215 Sq.ft/TR
Connected Load 80,700 TR
DCP‐2
Diversity Factor 74 %
g
ASHRAE check Figure 215 Sq.ft/TR
215 Sq.ft/TR
Plant load 60,000 TR Connected load 51,300 TR
Diversity Factor 68 %
DCP Plant load 35,000 TR
3
DCP
2

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Master Plan
DCP
DCP 4
1

DCP
3
DCP
2

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2012 GEC Ghani Workshop 3/23/2012

Interface with Building
Direct Connection  Indirect Connection 

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Direct Connection
Advantages Disadvantages
• More economical no • Building design pressure 
HE (~ 100 $/T exchanger +  should be same as the DCS 
accessories). which could add cost to the
which could add cost to the 
• No water treatment at user  end user.
side. • Cross contamination that 
• Reduced ETS space could affect both systems.
(xxxxxxx Sq. ft /TR). • Building specific water 
• Increased ΔT thus reduced  treatment may not be met 
distribution system capital  as treatment at central 
cost. plant.
• Reduced equipment 
R d d i • Plant & network design 
l kd
maintenance and potential  pressure might be affected 
shutdowns for HE cleaning. by end user. 

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2012 GEC Ghani Workshop 3/23/2012

Direct Connection
• Decision taken

• ETS
ETS for all users except for Mall (direct connection) 
for all users except for Mall (direct connection)
owned by the Energy Provider.

• Burj indirect due to static impact.

• Pipes
‐ Pre insulated with HDPE Jackets
‐ Leak detectors

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Pumping Scheme
Primary–Secondary

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2012 GEC Ghani Workshop 3/23/2012

Pumping Scheme
Primary–Distributed Secondary

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Case Study
Primary–Secondary vs. Primary‐Distributed Secondary

1) Primary Secondary

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2012 GEC Ghani Workshop 3/23/2012

Case Study

2) Distributed Secondary

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Pressure Gradient Diagram
1) Primary-Secondary System – Pressure Gradient

PRESSURE GRADIENT
PRIMARY-SECONDARY SYSTEM

200.000
MAX PRESSURE:
83 4 PSI
83.4
175.000

150.000
SYSTEM HEAD (ft)

125.000

100.000 Supply Line

Return Line

75.000

50.000

25.000

0.000
A

K
C

H
1

G
F

EX
J
t0

-2
-0

-
-
VB
-

-
-

-
-
in

--H
ot
VB

ot
ot

ot

ot

ot
ot

ot

ot
ot
Po

Pl
Pl
Pl

Pl

Pl

Pl
Pl

Pl

Pl
Pl

---
K-

STATIONS

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2012 GEC Ghani Workshop 3/23/2012

Pressure Gradient Diagram
2) Primary-Distributed Secondary – Pressure Gradient
PRESSURE GRADIENT
PRIMARY-DISTRIBUTED SYSTEM
200.000

175.000
MAX PRESSURE:
49.5 PSI
150.000
SYSTEM HEAD (ft)

125.000

Supply Line
100.000
Return Line
Pressure at Each Station
75.000

50.000

25.000

0.000
S

K
C

H
G

J
1

F
-2
P-

-0

-
-
VB
-

-
-

-
-

ot
VB
-P

ot
ot

ot

ot

ot
ot

ot

ot
ot

Pl
Pl
Pl

Pl

Pl

Pl
Pl

Pl

Pl
Pl
t0
in

STATIONS
Po

‐ Observe Pump Head       ‐ Max System Pressure

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Energy Curve of Both
YEARLY POWER CONSUMPTION
PRIMARY-DISTRIBUTED VERSUS PRIMARY SECONDARY

800000.00

700000.00

600000.00
POWER CONSUMPTION (KW)

500000.00

Primary Secondary
400000.00
Distributed Secondary

300000.00

200000 00
200000.00
P

100000.00

0.00
1 2 3 4 5 6 7 8 9 10 11 12
MONTHS

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2012 GEC Ghani Workshop 3/23/2012

Energy Saving Table
System Primary  Secondary  Primary Distributed Secondary 
Months           (KW) (KW)
January 114830.54 55911.45
February 145975 33
145975.33 71075 98
71075.98
March 306453.67 149213.53
April 359681.81 175130.52
May 494584.78 240815.33
June 629377.48 306446.44
July 666851.04 324692.46
August 659807.36 321262.87
September 543639.12 264700.08
October 404525.63 196965.16
November 248761.68 121123.06
December 155666.54 75794.67

TOTAL (MW) 4730.15 2303.13

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Advantages of Selected Pumping Scheme
• No ΔP control valve required. Distributed pumps handle 
the pressure variations.
• Chilled water can be obtained from any plant.

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2012 GEC Ghani Workshop 3/23/2012

Advantages of Selected Pumping Scheme
Any supply temperature could be achieved by direct 
mixing as return pressure higher than supply

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DCP Configuration

DCP‐2  Convention Plant  Capacity 35,000 TR

DCP‐1  Ice Storage  Capacity 40,000 TR

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DCP ‐ 2
What are chillers arrangement configurations?
1) Parallel Arrangement

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DCP ‐ 2

2) In-Series Arrangement
• Series chillers have better 
kw/ton
kw/ton. 

• Single path chiller with 
lower ΔP across evaporator.

• Both chillers in‐series have 
higher primary pump head
higher primary pump head.

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What Happens if Secondary is not
Matching Primary?
Fig-1: Series Arrangement

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What Happens if Secondary is not
Matching Primary?
Fig-2: Parallel Arrangement

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Load Profile has to be Analyzed
Loading % in each arrangement should be computed

LOADING PERCENTAGE COMPARISON

100.00

90.00

80.00
ADING PERCENTAGE

70.00

60.00

50.00

40.00
LOA

30.00

20.00

10.00

0.00
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300
HOURS

Series Arrangement Parallel Arrangement

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Load Profile has to be Analyzed
Hour by hour energy needs to be computed
Fig-1 Inseries Arrangement

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2012 GEC Ghani Workshop 3/23/2012

Load Profile has to be Analyzed
Fig-1 Parallel Arrangement

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Buffer Tank (TES)
May Improve the chiller KW/ton as the chillers will be 
loaded at all their best efficiency time, but no space

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2012 GEC Ghani Workshop 3/23/2012

Buffer Tank (TES)
Advantages
• Reduced compressor lift.

Disadvantages
• Increased chilled water pump head (two in‐series evaporators). 
• Increased condenser pump head (two in‐series condensers).
• Increased bypassed energy through decoupler.

Conclusion
• Analyze series/parallel arrangement with load profile and chiller 
loading percentage include pumping energy in primary and
loading percentage include pumping energy in primary and 
condenser circuits.
• Net results. 
• Shows saving if chiller staging is properly watched.

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Chiller Arrangement of DCP‐2

• Series‐counter flow configuration

• Number of chillers  original design = (2 x 2500) x 7 modules

• Number of chillers used (2 x 1250) x 14 modules

• Increased number of chillers staging

• Reduced wastage of energy through decouple

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2012 GEC Ghani Workshop 3/23/2012

Cooling Tower Types
Counter Flow Cross Flow

Induced draft counter-flow tower Induced draft cross-flow tower

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Advantages of Counter Flow
• Easier to maintain as water basin not restricted by wet deck.
• Less  space  needed  because  of  increased  efficiency  and  lack  of 
plenum space required for cross flow towers
plenum space required for cross flow towers.
• Longer  service  life  as  deck  supported  from  structural  supports 
underneath. No sagging as cross flow.
• Wet  deck  is  encased  on  all  sides  with  no  impact  from  direct 
prevailing wind.
• No  hot  water  basin  on  top  of  tower,  so  less  and  easy 
maintenance achieved.
• Taller in height that mean less prone to recirculation effect.
Taller in height that mean less prone to recirculation effect
• When towers are laid side by side, towers still accessible.
• Less pumping energy as no spray nozzles pressure.

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2012 GEC Ghani Workshop 3/23/2012

Orientation with Wind Direction
Wind
Vw
Disch
arge Vd
Plume

Vp

Effect of wind velocity and discharge Recirculation potential in a forced draft

velocity on plume behavior cooling tower

Comparative recirculation potential of round and

rectangular towers

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Orientation with Wind Direction

Proper orientation of towers in a prevailing longitudinal wind (requires

relative minimal tower size adjustment to compensate for recirculation and
interference effects)

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2012 GEC Ghani Workshop 3/23/2012

For Wet Coolers

where:
Humidity is expressed in absolute units of moisture 
content, for example, grains of moisture per pound of air.
content for example grains of moisture per pound of air

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For Wet Coolers
• Recirculation impacts design wet bulb temp
• CFD Modeling
‐ Conducted to validate tower performance at prevailing    wind 
speed.d
• Capacity
‐ Heat rejection
‐ Chiller motor cooling
‐ Safety
‐ Design wet bulb temp. considering recirculation
• Pump NPSH
‐ NPSHA > NPSH
NPSHR
Hs + Ha ‐ Hf ‐ Hv > NPSHR
‐ Found safe
‐ Other tools to overcome NPSH issues

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2012 GEC Ghani Workshop 3/23/2012

For Wet Coolers

• Sand storm & development construction 
activity dust
y
‐ Cooling tower dirt removal
• Sweeper systems
• Side stream filtration

• Ozone
• Issues & concerns of ozone
f
• Corrosion of steel parts (chiller marine box)

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Other Points Considered
• Network air venting & dirt removal

p p p
• Impact of air on pump 

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Other Points Considered
Gas venting (oxygen + nitrogen)

• Source 
‐ Air dissolved in make up water: used up by the initial corrosion.

‐ Air trapped in the system after initial filling: proper air venting

• Large bore vent to pass air bubble Surface tension breaker

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Other Points Considered

Diffusion: Expansion Tanks

Expansion tank with a bag Expansion tank with a membrane

• Air ingress due to negative pressure: expansion tank 
pressure should be maintained.

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2012 GEC Ghani Workshop 3/23/2012

Other Points Considered
• Air vents (1.64 ft/s)

• Air & dirt separators
Ai & di

Water speed versus removal time – ascending flow

(3.28 ft/s)

(2.46 ft/s)
(1.64 ft/s)

Water speed versus removal time – horizontal pipe

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Other Points Considered

Baffle Separator

Centrifugal Separator

Wire Mesh Separator

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2012 GEC Ghani Workshop 3/23/2012

Plant Configuration

Plant Arch Configuration

• Plant foot print 200 x 200 ft (60 x 60 mt)

• Chillers foot print 0.75 Sq. ft/T (0.07 Sq.m/T)

• Heat rejection required area 0.43 Sq.ft/T (0.04 Sq.m/T)

• Electrical work required area  0.54 Sq.ft/T (0.05 Sq.m/T)
Electrical work required area 0 54 Sq ft/T (0 05 Sq m/T)

• Pumps require area 0.32 Sq. ft/T (0.03 Sq.m/T)

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Plant Configuration

Basement: Pumps + water tank
Height 7 mt

Ground: Chiller Hall + Electrical + Expansion
Height 9 mt
Crane

Mezzanine: Offices + Control Room
Isolation from structure via vibration matt.

Roof: Cooling Tower

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DCP‐2 Plant Section

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DCP‐2 Photo

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District Cooling Plant‐1
• First large size district plant with Ice storage

p y
• Capacity   43000 TR

• Foot print  200 x 200 ft (60 x 60 m)

• Piles completed with no basement 

• Challenges
‐ Foot print not adequate for heat rejection equipment 
Foot print not adequate for heat rejection equipment
(200 x 200 ft)
‐ No basement available 
‐ No space for chillers at ground floor

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District Cooling Plant‐1
• Mall design Temp differs from Burj
‐ ΔT 16oF ( 8.8oC)
Supply 42oF(5.5oC)
‐ Supply 42

• Temp Challenge due to 5 stages with cascaded ETS

56oF

37oF

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District Cooling Plant‐1
Solution

• Thermal storage 
‐ No sufficient land for chilled storage 0.3 ‐ 0 6 m3/Thr
No sufficient land for chilled storage 0 3 ‐ 0.6 m
o
‐ Low temp below 39.4 F so chilled storage not possible
due to density change.

• Ice storage technique 0.07‐ 0.08 m3/Thr

• Tank on ground and up to 1st floor 

• As tank occupied the ground, chillers moved to 1st floor 

• Electric platform elevator 40 T on capacity (4.5 M US $)

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District Cooling Plant‐1
• Condenser pump on 1st floor

• NPSHA not sufficient 
not sufficient

• Proposed NPSH diffuser

• CT on roof elevated by 2 mt
f l db 2

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District Cooling Plant‐1

• Low Supply Temp Chillers

• Load achieved through:‐
‐ Low temp chillers as base load to operate at 
37oF (20,000 TR ).
‐ Glycol chillers to produce ice and operate at 
peak load via glycol heat exchangers (15,000 
TR).
)
‐ Heat exchangers between tank water and 
chilled water (7,000 TR ).

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District Cooling Plant‐1
Ice Storage
Discharging Mode

Glycol Chillers
Ice Storage Glycol Chillers
Chilling Mode

Base Load Chillers

The Peak Day Load Profile

External Melt Ice-On-Coil 57

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Flow Diagram

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DCP‐1 Plant Section

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DCP‐1 Plant Section
Challenges
• Dirt impact on glycol chiller tube heat 
transfer Manual cleaning is required
transfer.  Manual cleaning is required 
to maintain capacity.

• Automatic tube cleaning was used 
with brushes + diverting valve + 
controller to clean tubes 4 times /Day.

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DCP‐1 Plant Section

ATB System Valve
Automatically reverses flow 
for 30 sec every six hours

ATB System Control

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DCP‐1 Plant Section

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DCP‐1 Plant Section

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2012 GEC Ghani Workshop 3/23/2012

REMEMBER TO FILL OUT AND TURN IN THE EVALUATION FORM
Reminder:  If you are registered in Florida, New York, or North Carolina, 
you must also sign the sheets in the back at the end of the session.  Please 
print your name, include your registration number, and sign the sheet. 

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