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Chiller Plant:Chiller Plant:Fundamentals & Optimization

Julian R. de BulletASHRAE Distinguished Lecturerjulian@debullet.comjulian@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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