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Chiller Plant:Chiller Plant:Fundamentals & Optimization
Julian R. de BulletASHRAE Distinguished [email protected]@debullet.com
Big Plant Layout
60 000 Tons 60,000 Tons
40/58 °F Chilled Water
80,000 USgpm Chilled 80,000 USgpm Chilled Water 48” Dia. Pipe
93/103 °F Cond. Water
180,000 USgpm Cond. Water 54” Dia Pipe 54” Dia. Pipe
Big Plant Layout
Large Chilled Water Range Is a MustIs a Must
Using 18°F ∆T 48” Pipe - $500/ft 5000 ft = $2.5M 5800 hp @ 200’ head (It’s Over 10 000 hp @ 10°F (It s Over 10,000 hp @ 10 F ∆T)
Lower The Supply Water Temperature To Balance Temperature To Balance LMTD No Pump Or Pipe Savings
From Lower SWT Fan Savings
Full Load Vs. Annual Load
Peak Month Cooling Load Profile Chiller DesignPerformance
120
140Performance
80
100
d(To
ns)
20
40
60
Load
0
20
1 3 5 7 9 11 13 15 17 19 21 23
Hours
Full Load Vs. Annual Load
0.6
Same Chiller, Base LoadedAccounting For Condenser
Relief
0.4
0.50.55 kW/ton At AHRI
Conditions
0.2
0.3
0
0.1Chiller W/ VFD, Base LoadedAccounting For Condenser
Relief0
Fully Loaded W/C Centrifugal W/C Centrifugal VFD
Full Load Vs. Annual LoadFull Load Vs. Annual Load
ChillerChiller58%
TowerFans24%
Design Performance
Tower5%
24%Pumps
13% Chiller33%Fans
43%
Tower
Annual Energy Usage
Pumps22%
2%
Full Load Vs. Annual Load
SummarySummary
Full Load Or Daily Load Profiles Are A Poor Profiles Are A Poor Indicator Of Overall System Performance
There Is No Substitute For Annual Energy Analysis
Crunching the numbers
Air Cooled vs. Water Cooled
Avoid Tower, Pump And Piping
No Water Cost For Tower
Higher kW Than Water Cooled Chillers
Compressor Work Tracks Drybulb Not Wetbulb Very Good NPLVs
Excellent Choice For Schools With Reduced Summer Hours
Air Cooled Vs. Water Cooled
SummarySummary
Water Cooled Is More Energy Efficient Water Cooled Is More Energy Efficient
May Not Be More Cost Effective
Water And Maintenance Costs Water And Maintenance Costs
May Not Have Acceptable Life Cycle Analysis
Single Vs. Parallel Vs. Series
All Constant Flow Systems
All Have Same Total Pump Power
Single Chiller Design
800 Ton Load3 Way Valves52F Chilled Water
R t
2400 Usgpm 95F
Return
Cooling Tower40 kW
2400 Usgpm ChilledWater Pump
67 kW
2400 Usgpm Condenser Water Pump
33.5 kW
85FSupply To Chiller
44F Chilled WaterSupply800 Ton Chiller
0.55 kW/ton
Parallel Chiller Design
54F Chilled WaterR t
800 Ton Load
Return
2400 Usgpm ChilledWater Pump
67 kW
2400 Usgpm 95F
Two Cooling Towers20 kW Each
Two 1200 UsgpmCondenser Water Pumps
16.8 kW Each
85FSupply To Chiller
44F Chilled WaterSupplyTwo 400 Ton Chillers
0.55 kW/ton
Series Chiller Design
54F Chilled WaterR t
800 Ton Load
2400 Usgpm 95F
Return
Two Cooling Towers20 kW Each
Two Nominal 400 Ton Chillers. Two 1200 Usgpm
Condenser Water Pumps 16.8 kW Each 85FSupply
To Chiller
Lag 1 Produces 440 TonsLead 2 Produces 360 Tons
Lead ChillerLag Chiller2400 Usgpm Chilled
Water Pump
44F Chilled WaterSupply
Water Pump67 kW
Series-Counterflow Chiller Design
800 Ton Load54F Chilled WaterReturn
2400 Usgpm 95F
Two Nominal 400 Ton Chillers
One Cooling Tower40 kW
One 2400 Usgpm
Two Nominal 400 Ton Chillers. Chiller 1 Produces 440 TonsChiller 2 Produces 360 Tons
2400 Usgpm ChilledWater Pump
85FSupply To Lead Chiller
89F Supply Condenser Water Pump 33.6 kW
Water Pump67 kW
44F Chilled WaterSupply
89F Supply To Lag Chiller
Piping Diversity - 3 Way Valves
Flow Is Constant At Each Coil
Coil BypassLine
Delta T Changes With Load
CW Pump Sized For Connected FlowConnected Flow
44F Supply
3 Way Valve
ChillerCoil
Chiller Sized For Peak Load
Two Way Valves
Temperature Range Across Load Remains Constant.Load Remains Constant.Flow Varies With Load
CW Pump Sized For Chiller Flow RateAt D i D lt TAt Design Delta T
2 Way Valve
Chiller Sized For Peak Load
2 Way Valve
Standard Primary Loop Layout
Building Load600 Tons
(50% Load)480 gpm Flow ThroughTwo 400 Ton Chillers
51.5F Return WaterTo Chiller
44F
54F51.5F
DecouplerEach At 300 Tons(Balanced Load)
FlowChiller 1- On
Two Primary PumpsEach At 960 gpm
Chiller 2- On
44F
Secondary Pump1440 gpm
Chiller 3- Off
44F
1440 gpm
Variable Flow Vs. Constant FlowSummarySummary
Variable Flow Required For Systems Over 10 HP (6.4.3.1)( ) Modulate Down To 50%
Exceptions Where Minimum Flow Is
Less Than Flow Required By Equipment And < 75HP
Variable Primary Flow Design
Bypass LineypUsed to Ensure Minimum
Flow Through Chillers
VFD Primary Pump
Apply Diversity to FlowUse 2 Way Valves
Flow Meter
Automatic Isolating Valves
Variable Flow Vs. Constant Flow
400000
450000
500000
300000
350000
400000 Pump Work Cut In Half
200000
250000
kWh
Notice Pump WorkHalf Chiller Work!
50000
100000
150000
0Chillers Pumps Towers Fans
Variable Primary Flow 2 Chiller Primary/Secondary Flow 2 Chiller Parallel Flowy y y
Equipment - Performance
Improve Chiller Full Load kW/Ton From 0.55 To 0.45
An 18% Improvement In Chiller Provides Only An 18% Improvement In Chiller Provides Only 7% Improvement In Operating Cost
Chiller Price Goes Up Exponentially
Run Chiller Chiller Pumps Tower Fan S.A. Fan TotalkW/ton ($/yr) ($/yr) ($/yr) ($/yr) ($/yr)
1 0.55 24,435 15,209 1,441 24,512 65,5972 0 54 23 988 15 207 1 441 24 509 65 1452 0.54 23,988 15,207 1,441 24,509 65,1453 0.53 23,541 15,206 1,441 24,507 64,6954 0.52 23,095 15,204 1,441 24,504 64,2445 0.51 22,648 15,202 1,441 24,501 63,7926 0.5 22,202 15,201 1,441 24,499 63,3437 0.49 21,755 15,199 1,441 24,496 62,8918 0.48 21,309 15,197 1,441 24,493 62,4409 0 47 20 863 15 196 1 441 24 491 61 9919 0.47 20,863 15,196 1,441 24,491 61,99110 0.46 20,416 15,194 1,441 24,488 61,53911 0.45 19,970 15,192 1,441 24,485 61,088
ARI Standard 550/590-98
Know your Standards!y
99% Of All 99% Of All Operating Hours Are p gAt Part Load
The New Industry ARI Standard -1998
Part Load Analysis (IPLV)y ( )
% Load Old % Hrs New % Hrs100 17 1100 17 175 39 4250 33 4525 11 12
Systems SolutionSystems Solution
Various 500 Ton Chillers
.6
.5.505
4 .403
IPLV
.4
.365.337
.3WSC WDC WDC w/VFDWSC w/VFD
Notes: WSC = Single Compressor Centrifugal ChillerWDC = Dual Compressor Centrifugal Chillerp gVFD = Variable Frequency Drive
Analyze your design!
Equipment - Properties
Different Chillers Operate Differently VFD Chillers Need Condenser Relief
Duals Are Most Efficient At 50% Load
Absorption And Gas Driven Chillers Operate On a different Fuel
System Must Take Advantage OF Chiller Properties System Must Take Advantage OF Chiller Properties To Get Best Results
Pa t Load Pe fo mance Is Us all Mo e Impo tant Part Load Performance Is Usually More Important Than Full Load Performance
Single vs. Dual Compressor Chillers
1.2
0.8
1
n
0.4
0.6
KW
/Ton
0
0.2
0 20 40 60 80 100
% Chiller Plant LoadTwo Single Chillers Two Dual Chillers
EquipmentSummarySummary
Be Careful That High Performance Equipment Can Pay For ItselfEquipment Can Pay For Itself Ask For A Couple Of Selections And Some
Budget Pricing
Understand And Take Advantage Of Chillers Operating Properties
Range Vs. Supply Water Temperature
Flow (Usgpm) = Load (tons) x 24 / Temp. Range (F)
Increasing Range Reduces Flow Reduces Pipe, Pump And Motor Size
Pump Power (hp) = Flow (Usgpm)x Head (ft) / 3960 x Eff Pump Power (hp) = Flow (Usgpm)x Head (ft) / 3960 x Eff.
Reducing Flow Reduces Pump Work
This Is A Good Goal
It Will Affect Every Part Of the Chilled Water System Everything Must Be Considered
Range Vs. Supply Water Temperature Fan Work Savings For Small Changes (2 to 4°F)
Don’t Save Enough To Offset Chiller Penalty
Especially For VAV Especially For VAV 20% Airflow Decrease
35% Static Decrease
49% Power Decrease
Don’t Lower Supply Water Temperature Just To Save FanworkSave Fanwork
Don’t Lower To Ensure Design Water Temperature Will Be Available At Coil If You Assume Water Will Be 2°F Warmer At Coil
Then You Assume 20% Of Chiller Capacity Lost To Heat Gain!
Range Vs. Supply Water Temperature
Standard ARI HEAT OF
97°F118.3 psig
R-134a
θ2
Conditions 54- 44F Chilled Water
85 - 95F Condenser CONDENSER FLUID TEMPERATURE
CONDENSATION 95°F
θ1
T2
85 95F Condenser Water
10F Range
C
C
LIFT(°F)
T1
T154°F
85°F
2F Approaches In Heat Exchangers
55F Lift On
COOLER FLUID TEMPERATURE
HEAT OFVAPORIZATION
44°Fθ1 T2
CompressorSATURATED SUCTION TEMPERATURE {T }R
VAPORIZATION
42°F36.6 psigR-134a
θ2
Range Vs. Supply Water Temperature
Change To 14F Range Smaller Pumps, Pipes
etcetc. Maintain Supply Water
Temperature LMTD Increases LMTD Increases
Improves Chiller Performance
Hurts Chilled Water Coil Performance Deeper Coils Required Increased Fan Static
PressurePressure
Range Vs. Supply Water Temperature
Maintain 14F Range
L S l W Lower Supply Water Temperature To 42F
4% Increase In Compressor Lift Chiller Performance
Suffers
Chilled Water Coil Performance ImprovesImproves
Range Vs. Supply Water Temperature VAV Office Bldg In New York City Fixed Supply Water Temperature Design Conditions Design Conditions Increase Chilled Water Range From 10 To 24F Fan Motor Goes From 94.8 HP To 114.7 HP (21%) Pump Goes From 38.5 HP to 16 HP (58%)
Chiller Chilled Water Coil Fan TotalRun Capacity Perform Temp Range Pump APD Rows/fins TSP Motor size Power
Tons KW/ton (°F) HP (in. w.c.) (in. w.c.) (HP) (HP)1 400 0.546 10 38.5 0.62 5/10 3 94.8 426.12 400 0 546 12 32 1 0 66 5/11 3 04 96 420 92 400 0.546 12 32.1 0.66 5/11 3.04 96 420.93 400 0.547 14 27.5 0.7 6/10 3.08 97.3 417.64 400 0.547 16 24 0.79 6/12 3.15 99.5 416.35 400 0.543 18 21.4 0.87 8/9 3.25 102.7 415.36 400 0.543 20 19.2 0.94 8/11 3.32 104.9 415.36 400 0.543 20 19.2 0.94 8/11 3.32 104.9 415.37 400 0.543 22 17.5 1.1 10/10 3.48 109.9 418.68 400 0.543 24 16 1.25 12/10 3.63 114.7 421.9
Range Vs. Supply Water Temperature
Fixed Supply Water Temperature
Increase Chilled Water Range From 10 to 24F Increase Chilled Water Range From 10 to 24F
Annual Energy Analysis
System Peaks At 16F Range
Run C.W. Range Chiller Pumps Tower Fan S.A. Fan Total(°F) ($/yr) ($/yr) ($/yr) ($/yr) ($/yr)
1 10 26,074 15,175 1,591 28,275 71,1152 12 26,096 13,784 1,593 28,560 70,0333 14 26,167 12,792 1,594 28,846 69,3994 16 26 211 12 055 1 597 29 350 69 2134 16 26,211 12,055 1,597 29,350 69,2135 18 26,081 11,489 1,601 30,070 69,2416 20 26,126 11,034 1,604 30,574 69,3387 22 26,259 10,784 1,619 31,726 70,3888 24 26,358 10,487 1,625 32,810 71,280
Range Vs. Supply Water Temperature Switch To Constant Volume With Reheat Increase Chilled Water Range From 10 to 24F Annual Energy Analysis Annual Energy Analysis System Peaks At 14F
Fan Penalty Outweighs Pump Savings
Run C.W. Range Chiller Pumps Tower Fan S.A. Fan Total(°F) ($/yr) ($/yr) ($/yr) ($/yr) ($/yr)( F) ($/yr) ($/yr) ($/yr) ($/yr) ($/yr)
1 10 40,035 19,842 2,821 70,957 133,6552 12 40,034 18,013 2,821 71,954 132,8223 14 40,224 16,728 2,831 72,396 132,1794 16 40,327 15,765 2,839 73,657 132,5885 18 40,174 15,025 2,852 75,455 133,5066 20 40,285 14,429 2,863 76,715 134,2927 22 40 526 13 963 2 884 79 595 137 1937 22 40,526 13,963 2,884 79,595 137,1938 24 40,772 13,692 2,912 82,283 139,659
Range Vs. Supply Water Temperature
Declining Supply Water Temperature (44 To 38F) Increase Chilled Water Range From 10 To 24F Annual Energy Analysis System Peaks At 16F Range And 42F SWT
Run C.W. Range C.W. S.T. Chiller Pumps Tower Fan S.A. Fan Total(°F) (°F) ($/yr) ($/yr) ($/yr) ($/yr) ($/yr)
1 10 44 26,074 15,175 1,591 28,275 71,115 Not As Good As 16F Range And 44F SWT!2 12 44 26,096 13,784 1,593 28,560 70,0333 16 44 26,211 12,055 1,597 29,350 69,2133 14 42 27,733 12,790 1,593 28,573 70,6894 16 42 27,779 12,039 1,593 28,570 69,9816 , 9 ,039 ,593 8,5 0 69,985 18 40 29,371 11,462 1,594 28,584 71,0116 20 40 29,351 11,002 1,596 28,872 70,0817 22 38 30,365 10,623 1,596 28,881 71,465
Condenser Water Range
Increase Condenser Water Range From 10 To 15F Annual Energy Analysis Annual Energy Analysis System Peaks At 10 Range It Costs More To Operate A System At Higher Ranges
Run Cond .W. Range Chiller Pumps Tower Fan S.A. Fan Total(°F) ($/ ) ($/ ) ($/ ) ($/ ) ($/ )(°F) ($/yr) ($/yr) ($/yr) ($/yr) ($/yr)
1 10 26,074 15,175 1,591 28,275 71,1152 11 27,084 14,562 1,592 28,283 71,5213 12 27,517 14,049 1,592 28,286 71,4444 13 28 094 13 616 1 592 28 290 71 5924 13 28,094 13,616 1,592 28,290 71,5925 14 28,527 13,245 1,592 28,293 71,6576 15 29,057 12,923 1,593 28,297 71,870
Condenser Water Relief
Optimizing Starter Selections
Try Different Starters
Solid State Starters Have Different Size Breaks Than Wye Delta Starters
S lid S S A N Ch Solid State Starters Are Now Cheaper In Most Cases - Try Both Ways Depending Upon Size Breaksp g p
Try Unit Mounted And Free Standing -Size Breaks Can Make Different Selections Appear
Check VFD Sizing –Expensive At Very Bottom Of Amp RatingBottom Of Amp Rating
Annual WB In Major US Cities
60.0
70.0
80.0
30.0
40.0
50.0
-
10.0
20.0 Strong Candidates ForVFD Chillers
Janu
aryFeb
ruary
March
April
May
June July
Augus
tSep
tembe
rOcto
ber
Novem
ber
Decem
ber
Los Angeles Washington DC Atlanta Chicago Miami
AVAILABILITY OF REFRIGERANT(Dupont & ICI Projections)
M Tonnes (000)M Tonnes (000)
300
250
200
150HFC134aHFC134a
150
100
HCFC22HCFC22 HFC410AHFC410A
50
0
HCFC123HCFC123
0
Year
1995 2000 2005 2010 2015 2020 2025 2030
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