How to Achieve High Delta T Eric M. Moe IDEA International Conference

How to Achieve High Delta T
(∆T) at Peak and Part Load
Eric M. Moe
IDEA International Conference
Abu Dhabi, UAE
January 2007
42/55 Plant (13°∆T Design)
80
OATwb
70
Temperature (deg F)
Low Delta T
(∆T) is a Common
and Expensive
District Cooling
Problem
90
60
50
40
30
- lost plant capacity
20
- added complexity
- wasted energy
- poor control
10
0
CHWST - Primary
CHWST - Secondary
Delta T - Primary
Delta T - Secondary
Low ∆T Limits Capacity / Wastes Energy
12000
Rated Tons of Running Chillers
10000
More (or larger)
equipment required to
serve the loads
8000
Cooling (Tons)
Low ∆T means fewer
ton-hrs/gallon and
sq-ft/installed ton
6000
Chillers
Pumps
Fans
Pipes
TES
4000
2000
Actual Cooling Load
0
$$$$
$$$$
$$$$
$$$$
$$$$
Pressure Independent Control
is Fundamentally Different
Applied at Coils and Heat Exchangers
•
•
•
Simple direct connect
Direct connect w/ booster pump and bypass
Indirect w/ heat exchanger
5 psid
5 psid
T
FM
FM
Control distribution pumps to minimum
differential pressure, not supply or return
FM
Optimizes Cooling Coil Heat Transfer
ARI Cooling Coil
100%
90%
% Cooling Load
DeltaPValves
Minimum Acceptable
Coil Performance
Design Delta T
80%
70%
60%
50%
40%
30%
Conventional
20%
10%
0%
0%
20%
40%
% Flow
•
•
•
optimizes cooling coil heat transfer
eliminates effect of pressure changes
sized by flow rate alone
60%
80%
100%
Prevents / Addresses Low ∆T
Delivers Systemwide Benefits
100
90
Exelon Thermal
Midway Airport
Temp (deg F)
80
70
Outside Air
60
CHW Return
50
CHW Supply
40
Delta T
30
20
10
0
Time on August 1, 2002
• ∆T > 18°F design (avoid penalties)
• Minimum installed plant capacity
• Uncommonly high efficiency
• No terminal pumps, crossovers
• No balancing valves
Why Strive for High ∆T?
Heat and cool more space with less
energy, equipment, complexity and cost.
For more information about pressure independent
control as well as applications support, please contact:
Eric M. Moe
425-483-1297
ericm@flowcontrol.com
www.flowcontrol.com