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Chiller Plant: Fundamentals & Optimization Julian R. de Bullet ASHRAE Distinguished Lecturer
[email protected]
Big Plant Layout 60,000 60 000 Tons 40/58 °F Chilled Water 80,000 USgpm Chilled Water 48” Dia. Pipe
93/103 °F Cond. Water 180,000 USgpm Cond. Water 54” Dia. Dia Pipe
Big Plant Layout Large Chilled Water Range Is a Must Using 18°F ∆T 48” Pipe - $500/ft 5000 ft = $2.5M 5800 hp @ 200’ head (It’s (It s Over 10 10,000 000 hp @ 10 10°F F ∆T)
Lower The Supply Water 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 Design Performance
140 120
80 60 40 20
Hours
23
21
19
17
15
13
11
9
7
5
3
0
1
Load d(Tons)
100
Full Load Vs. Annual Load Same Chiller, Base Loaded Accounting For Condenser Relief
0.6
0.5
0.55 kW/ton At AHRI Conditions 0.4 0.3
0.2
Chiller W/ VFD, Base Loaded 0.1 Accounting For Condenser Relief 0
Fully Loaded
W/C Centrifugal
W/C Centrifugal VFD
Full Load Vs. Annual Load Chiller 58%
Fans 24% Pumps 13%
Design Performance
Tower 5%
Chiller 33%
Fans 43%
Pumps 22%
Annual Energy Usage
Tower 2%
Full Load Vs. Annual Load Summary Full Load Or Daily Load 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 Summary
Water Cooled Is More Energy Efficient May Not Be More Cost Effective 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 52F Chilled Water R t Return
800 Ton Load 3 Way Valves
2400 Usgpm 95F
2400 Usgpm Chilled Water Pump 67 kW
2400 Usgpm Condenser Water Pump 33.5 kW
800 Ton Chiller 0.55 kW/ton
Cooling Tower 40 kW 85FSupply To Chiller
44F Chilled Water Supply
Parallel Chiller Design 800 Ton Load 54F Chilled Water R t Return 2400 Usgpm Chilled Water Pump 67 kW
2400 Usgpm 95F
Two 1200 Usgpm Condenser Water Pumps 16.8 kW Each
Two Cooling Towers 20 kW Each
85FSupply To Chiller
Two 400 Ton Chillers 0.55 kW/ton
44F Chilled Water Supply
Series Chiller Design 800 Ton Load 54F Chilled Water R t Return 2400 Usgpm 95F
Two Cooling Towers 20 kW Each
Two 1200 Usgpm Condenser Water Pumps 16.8 kW Each
2400 Usgpm Chilled Water Pump 67 kW
Two Nominal 400 Ton Chillers. Lag 1 Produces 440 Tons Lead 2 Produces 360 Tons
Lag Chiller
Lead Chiller
85FSupply To Chiller
44F Chilled Water Supply
Series-Counterflow Chiller Design 800 Ton Load
54F Chilled Water Return
2400 Usgpm 95F One Cooling Tower 40 kW Two Nominal 400 Ton Chillers. Chillers Chiller 1 Produces 440 Tons Chiller 2 Produces 360 Tons 2400 Usgpm Chilled Water Pump 67 kW
89F Supply To Lag Chiller
85FSupply To Lead Chiller
One 2400 Usgpm Condenser Water Pump 33.6 kW 44F Chilled Water Supply
Piping Diversity - 3 Way Valves Coil Bypass Line Flow Is Constant At Each Coil Delta T Changes With Load
CW Pump Sized For Connected Flow
44F Supply
Chiller
Chiller Sized For Peak Load
Coil 3 Way Valve
Two Way Valves Temperature Range Across Load Remains Constant. Flow Varies With Load
CW Pump Sized For Chiller Flow Rate At D Design i D Delta lt T
Chiller Sized For Peak Load
2 Way Valve
Standard Primary Loop Layout 51.5F Return Water To Chiller Two 400 Ton Chillers Each At 300 Tons (Balanced Load)
Chiller 1- On Two Primary Pumps Each At 960 gpm
51.5F 480 gpm Flow Through Decoupler
54F 44F
Building Load 600 Tons (50% Load)
Flow
Chiller 2- On 44F
Chiller 3- Off
Secondary Pump 1440 gpm
Variable Flow Vs. Constant Flow Summary 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 yp Line Used to Ensure Minimum Flow Through Chillers
VFD Primary Pump Apply Diversity to Flow Use 2 Way Valves Flow Meter
Automatic Isolating Valves
Variable Flow Vs. Constant Flow 500000 450000 400000
Pump Work Cut In Half
350000
kWh
300000 250000
Notice Pump Work Half Chiller Work!
200000 150000 100000 50000 0 Chillers Variable Primary y Flow
Pumps
Towers
2 Chiller Primary/Secondary y y Flow
Fans 2 Chiller Parallel Flow
Equipment - Performance Improve Chiller Full Load kW/Ton From 0.55 To 0.45 An 18% Improvement In Chiller Provides Only 7% Improvement In Operating Cost Chiller Price Goes Up Exponentially Run 1 2 3 4 5 6 7 8 9 10 11
Chiller kW/ton 0.55 0 54 0.54 0.53 0.52 0.51 0.5 0.49 0.48 0 47 0.47 0.46 0.45
Chiller ($/yr) 24,435 23 988 23,988 23,541 23,095 22,648 22,202 21,755 21,309 20 863 20,863 20,416 19,970
Pumps ($/yr) 15,209 15 207 15,207 15,206 15,204 15,202 15,201 15,199 15,197 15 196 15,196 15,194 15,192
Tower Fan ($/yr) 1,441 1 441 1,441 1,441 1,441 1,441 1,441 1,441 1,441 1 441 1,441 1,441 1,441
S.A. Fan ($/yr) 24,512 24 509 24,509 24,507 24,504 24,501 24,499 24,496 24,493 24 491 24,491 24,488 24,485
Total ($/yr) 65,597 65 145 65,145 64,695 64,244 63,792 63,343 62,891 62,440 61 991 61,991 61,539 61,088
ARI Standard 550/590-98
Know y your Standards!
99% Of All Operating p g Hours Are At Part Load
The New Industry ARI Standard -1998
Part Load Analysis y (IPLV) ( ) % Load
Old % Hrs
New % Hrs
100
17
1
75
39
42
50
33
45
25
11
12
Systems Solution
Various 500 Ton Chillers
.6
.505
IPLV
.5
.403
.4 4
.365 .337
.3 WSC
WDC
WSC w/VFD
Notes: WSC = Single Compressor Centrifugal Chiller p Centrifugal g Chiller WDC = Dual Compressor VFD = Variable Frequency Drive
WDC w/VFD
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 To Get Best Results Pa Partt Load Pe Performance fo mance Is Us Usually all Mo More e Important Impo tant Than Full Load Performance
Single vs. Dual Compressor Chillers 1.2 1
KW/Ton n
0.8 0.6 0.4 0.2 0 0
20
40
60
80
% Chiller Plant Load Two Single Chillers
Two Dual Chillers
100
Equipment Summary
Be Careful That High Performance Equipment 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. 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 20% Airflow Decrease 35% Static Decrease 49% Power Decrease
Don’t Lower Supply Water Temperature Just To Save 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 97°F 118.3 psig R-134a
Standard ARI Conditions θ1
54- 44F Chilled Water 85 - 95F Condenser Water
10F Range 2F Approaches In Heat Exchangers
θ2
HEAT OF CONDENSATION
E NS DE N CO LIFT (°F)
DT L UI F R
URE RAT E P EM
T2
95°F
85°F T1
54°F T1 CO O
θ1
55F Lift On Compressor
L ER
FLU ID
TEM P
ERAT U
RE
T2
HEAT OF VAPORIZATION
42°F 36.6 psig R-134a
SATURATED SUCTION TEMPERATURE {TR}
44°F
θ2
Range Vs. Supply Water Temperature Change To 14F Range Smaller Pumps, Pipes etc. etc
Maintain Supply Water Temperature LMTD Increases Improves Chiller Performance
Hurts Chilled Water Coil Performance Deeper Coils Required Increased Fan Static Pressure
Range Vs. Supply Water Temperature Maintain 14F Range L Lower S Supply l W Water Temperature To 42F 4% Increase In Compressor Lift Chiller Performance Suffers
Chilled Water Coil Performance Improves
Range Vs. Supply Water Temperature VAV Office Bldg In New York City Fixed Supply Water Temperature 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%)
Run 1 2 3 4 5 6 7 8
Chiller Chilled Water Capacity Perform Temp Range Tons KW/ton (°F) 400 0.546 10 400 0 546 0.546 12 400 0.547 14 400 0.547 16 400 0.543 18 400 0.543 20 400 0.543 22 400 0.543 24
Pump HP 38.5 32 1 32.1 27.5 24 21.4 19.2 17.5 16
Coil Fan Total APD Rows/fins TSP Motor size Power (in. w.c.) (in. w.c.) (HP) (HP) 0.62 5/10 3 94.8 426.1 0 66 0.66 5/11 3 04 3.04 96 420 9 420.9 0.7 6/10 3.08 97.3 417.6 0.79 6/12 3.15 99.5 416.3 0.87 8/9 3.25 102.7 415.3 0.94 8/11 3.32 104.9 415.3 1.1 10/10 3.48 109.9 418.6 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 Annual Energy Analysis System Peaks At 16F Range Run C.W. Range (°F) 1 10 2 12 3 14 4 16 5 18 6 20 7 22 8 24
Chiller ($/yr) 26,074 26,096 26,167 26 211 26,211 26,081 26,126 26,259 26,358
Pumps Tower Fan S.A. Fan ($/yr) ($/yr) ($/yr) 15,175 1,591 28,275 13,784 1,593 28,560 12,792 1,594 28,846 12 055 12,055 1 597 1,597 29 350 29,350 11,489 1,601 30,070 11,034 1,604 30,574 10,784 1,619 31,726 10,487 1,625 32,810
Total ($/yr) 71,115 70,033 69,399 69 213 69,213 69,241 69,338 70,388 71,280
Range Vs. Supply Water Temperature Switch To Constant Volume With Reheat Increase Chilled Water Range From 10 to 24F Annual Energy Analysis System Peaks At 14F Fan Penalty Outweighs Pump Savings
Run 1 2 3 4 5 6 7 8
C.W. Range ((°F) F) 10 12 14 16 18 20 22 24
Chiller ($/yr) 40,035 40,034 40,224 40,327 40,174 40,285 40 526 40,526 40,772
Pumps Tower Fan S.A. Fan ($/yr) ($/yr) ($/yr) 19,842 2,821 70,957 18,013 2,821 71,954 16,728 2,831 72,396 15,765 2,839 73,657 15,025 2,852 75,455 14,429 2,863 76,715 13 963 13,963 2 884 2,884 79 595 79,595 13,692 2,912 82,283
Total ($/yr) 133,655 132,822 132,179 132,588 133,506 134,292 137 193 137,193 139,659
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 1 2 3 3 4 5 6 7
C.W. Range C.W. S.T. (°F) (°F) 10 44 12 44 16 44 14 42 16 6 42 18 40 20 40 22 38
Not As Good As 16F Range And 44F SWT!
Chiller ($/yr) 26,074 26,096 26,211 27,733 27,779 , 9 29,371 29,351 30,365
Pumps Tower Fan S.A. Fan ($/yr) ($/yr) ($/yr) 15,175 1,591 28,275 13,784 1,593 28,560 12,055 1,597 29,350 12,790 1,593 28,573 12,039 ,039 1,593 ,593 28,570 8,5 0 11,462 1,594 28,584 11,002 1,596 28,872 10,623 1,596 28,881
Total ($/yr) 71,115 70,033 69,213 70,689 69,981 69,98 71,011 70,081 71,465
Condenser Water Range Increase Condenser Water Range From 10 To 15F Annual Energy Analysis System Peaks At 10 Range It Costs More To Operate A System At Higher Ranges
Run 1 2 3 4 5 6
Cond .W. Range (°F) 10 11 12 13 14 15
Chiller ($/ ) ($/yr) 26,074 27,084 27,517 28 094 28,094 28,527 29,057
Pumps Tower Fan S.A. Fan ($/ ) ($/yr) ($/ ) ($/yr) ($/ ) ($/yr) 15,175 1,591 28,275 14,562 1,592 28,283 14,049 1,592 28,286 13 616 13,616 1 592 1,592 28 290 28,290 13,245 1,592 28,293 12,923 1,593 28,297
Total ($/ ) ($/yr) 71,115 71,521 71,444 71 592 71,592 71,657 71,870
Condenser Water Relief
Optimizing Starter Selections Try Different Starters
Solid State Starters Have Different Size Breaks Than Wye Delta Starters Solid S lid S State S Starters Are A Now N Ch Cheaper In Most Cases - Try Both Ways Depending p g Upon p Size Breaks Try Unit Mounted And Free Standing Size Breaks Can Make Different Selections Appear Check VFD Sizing –Expensive At Very Bottom Of Amp Rating
Annual WB In Major US Cities 80.0 70.0 60.0 50.0 40.0 30.0
Strong Candidates For VFD Chillers
20.0 10.0
Los Angeles
Washington DC
Atlanta
Chicago
be r
ec em
be r D
ov em
N
r
ct ob er O
Se pt em be
Au gu st
Ju ly
Ju ne
ay M
Ap ril
ar ch M
Ja nu ar y Fe br ua ry
-
Miami
AVAILABILITY OF REFRIGERANT (Dupont & ICI Projections) M Tonnes (000) 300 250 200
HFC134a 150
HCFC22
HFC410A
100 50 0
HCFC123 1995
2000
2005
2010
Year
2015
2020
2025
2030
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