COMMERCIAL HVAC CHILLER EQUIPMENT Water-Cooled...

© 2013 Carrier Corporation

COMMERCIAL HVACCHILLER EQUIPMENT

Water-Cooled ChillersPRESENTED BY:

Omar RojasSales Engineer

Technical Development Program


MenuSection 1 Introduction

Section 2 Basic Refrigeration Cycle

Section 3 Chiller Components

Section 12 Summary

Section 4 Chiller Controls

Section 5 Screw Compressor Operational Details

Section 6 Centrifugal Compressor Operational Details

Section 7 Capacity Control Methods

Section 8 Refrigerant Related Topics

Section 9 Heat Transfer

Section 11 Selection Criteria

Section 10 Codes and Standards


SECTION 1

Introduction

WATER-COOLED CHILLERS


• Compare the advantages of water-cooledversus air-cooled chillers

• Identify and diagram the different componentsof a basic refrigeration cycle as it applies to awater-cooled chiller

• Compare and describe the differences amongscroll, reciprocating, centrifugal, and screwwater-cooled chillers and their applications

• Discuss the differences in construction ofwater-cooled chillers of various sizes

• Identify the codes and standardsthat apply to water-cooled chillers

• Understand the typical inputs requiredto select a water-cooled chiller

Section 1 – Introduction

Objectives


Dr. Willis H. Carrier

In the early 1900’s, centrifugal air compressorswere adopted for use in the air conditioning

industry.



Early Centrifugal Chiller



Smithsonian Institute

Carrier Centrifugal Chiller on Display



Evolution of Centrifugal Chillers



Water-Cooled vs. Air-Cooled Chillers



Water-cooled packaged chillers are availableup to about 3000 tons of capacity.

Typical Water-Cooled Chiller System

Water-CooledCondenser

Chiller

Cooling Tower

CondenserWater Pump



SECTION 2

Basic Refrigeration Cycle



Evaporator

Condenser

Compressor

WaterNozzles

PressureReducing

Device

95° F85° F

44° F54° F

LiquidLine

Hot GasDischarge Line

Suction Line


Section 2 – Basic Refrigeration Cycle


Pressure-Enthalpy DiagramRefrigeration Cycle

LIFT


Saturated Condensing

Saturated Suction

PRES

SUR

E

RE

Pc

Ps

ENTHALPY


Refrigeration Cycle with Subcooling

SUBCOOLING

ts

tc

hfc hgs

PRES

SUR

E

ENTHALPY

Pc

PsVgs

RE



Water-Cooled Condenser Subcooler

Subcooler “box”at the bottom ofthe condenser

Float valvemetering device

Orifices insubcooler

Condenser tubes

Condensershell



Refrigeration Cycle with Economizer2-Stage Centrifugal Shown

RE

Pc

Ps

hfchfe hgs hge h3

P2Pe

PRES

SUR

E

ENTHALPY



SECTION 3

Chiller Components



Brazed-Plate Evaporator

Section 3 – Chiller Components

Note: Brazed-plate heat exchangersare also used as condensers

Return water in54º F

Refrigerant out

Chilled water out44º F

Refrigerant in


Direct Expansion Evaporator

Water Out

Water In

• Refrigerant is in the tubes• Water is in the shell



Flooded Shell-and-Tube Evaporator

End Tube Sheet

Refrigerant Suction Flange

Waterbox Ring

Tubes penetratingend of tube sheet



Flooded Shell-and-Tube Evaporator

Tube Support Sheets

Water in tubes

Water Nozzles

Refrigerant Suction Outlet

Liquid refrigerant“floods” the shellaround the tubes.



Evaporator Refrigerant Path

Liquid Refrigerant from Condenser

Suction Gas toCompressor

WaterboxNozzles

Gaseous RefrigerantGaseous Refrigerant

Liquid RefrigerantLiquid Refrigerant

RefrigerantDistribution System



Space Elimination

Liquid RefrigerantDistribution Box

Free spacefor gaseousrefrigerant Tube

SupportSheets

Liquid refrigerant risesLiquid refrigerant risesto top-most tube level.



End Tube Support Sheet

Double Grooves


© 2013 Carrier CorporationSection 3 – Chiller Components

Parallel and Series Evaporators


End Tube Support Sheet

Waterbox RingFloat Valve

Chamber

Hot Gas InletSubcooler

Circuit

Large Chiller Shell-and-Tube Condenser



Float ValveChamber

Orifice

Hot Gas Inlet

Tubes

TubeSupport Sheets

Subcooler

Large Chiller Condenser Cutaway


LiquidOutlet


Condenser Refrigerant Path

Hot Refrigerant Vapor Inlet

Water

Liquid Refrigerant Outlet

Return toCooling Tower

FromCooling Tower



Compressors

Two Categories:

- Positive Displacement

- Dynamic Compression(Centrifugal)



Semi-HermeticCompressor

Reciprocating Compressor

Cylinder Head Terminal Box

Motor

Multi-CompressorReciprocating Chiller



Reciprocating Compressor



Scroll Compressor

HermeticShell

SuctionInlet

HermeticMotor

Hot GasDischarge

Electrical TerminalConnection

OrbitingScrolls

Pressure Relief



Scroll Compressor



Screw Compressor

Screw Compressor

Evaporator

Condenser

2-Circuit Screw Chiller



Double Rotor Screw Compressor



Centrifugal Compressor

Inlet GuideVanes

Transmission

Impeller

Guide VaneMotor

Refrigerant MotorCooling Line

MotorRotor


Hermetic Drive

Open Drive


Centrifugal Compressor Need Avifile



Hermetic Centrifugal CompressorRefrigerant Cooling Transmission

InletGuideVanes

Impeller

High SpeedShaft

HermeticHousing

Oil Filter

Electric MotorRotor

Low SpeedShaft

Oil Pump



Open Drive Centrifugal Compressor


Drive Shaft


Refrigerant Metering – Large Chiller

Float Valve Open

Hot Gas Inlet Condenser

CondenserTubes

LiquidRefrigerant


Liquid Outlet


Nozzle-in-Head Waterboxes

Nozzles

WaterboxAssembly

“Dished”Head Design



Marine Waterboxes

Nozzles

Hinged Water Box Covers

1 or 3-PassMarine

Waterbox

EVAPORATOR

CONDENSER

2-PassMarineWaterbox

Outlet

Inlet


Outlet


Purge Unit

Purge Unit

Negative PressureCentrifugal Chiller



Positive Pressure Chiller/Transfer Compressor



Storage Tank and Transfer UnitTank-MountedTransferCompressor

Refrigerant Storage Tank

This assembly is requiredwhen using a chiller designwhere in-chiller storage ofrefrigerant is not available.



Relief Valves

Rupture Disk Relief onNegative Pressure Centrifugal Chiller

Reseating Type Relief Valves onPositive Pressure Centrifugal Chiller



SECTION 4

Chiller Controls



Centrifugal Chiller Control Panel

RUNNING TEMP CONTROLLEAVING CHILLED WATER

06-07-04 11:48214 HOURS

CCN LOCAL RESET MENU

CHW IN55.1

CHW OUT

44.1EVAP REF

40.7CDW IN

85.0CDW OUT

95.0COND REF

98.1OIL PRESS

21.8OIL TEMP

132.9MTR AMPS

93

Section 4 – Chiller Controls

Unit-Mounted Control Panel

• Includes visual display/user interface

• Monitors and controls the chiller andauxiliary devices such as pumps

• Provides BAS communication functions


Chiller Starting Methods• Across-the-Line

• Auto Transformer*

• Primary Reactor*

• Part-Winding*

• Wye-Delta*

• Solid State*

• Variable Frequency Drive†


* Soft Start† Softest Start


Unit-Mounted Solid State Starter



VFD Starter for Unit-Mounting



Motor Starting Current Information


Starting MethodMotor Starting Current as a % of

Locked Rotor Current Full Load CurrentAcross-the-Line 100 600

Auto Transformer & Primary Reactor80%65%50%

806550

480390300

Part Winding 65 390

Wye-Delta 33 200

Solid-State 0 - 100 0 - 600

VFD 16.6 100


SECTION 5

Screw CompressorOperational Details



Screw Chiller Technology

Section 5 – Screw CompressorOperational Details

Large Screw Chiller Compressor

Transmission

Rotors


SECTION 6

Centrifugal CompressorOperational Details



FORCE

BALL

DIAMETER

GASMOLECULE

FORCE

LENGTH

STRING

Centrifugal Compressor Theory• Heavier the ball (molecular weight) = MORE FORCE• Longer the string (diameter) = MORE FORCE• Faster the ball rotates (rpm) = MORE FORCE

Section 6 – Centrifugal CompressorOperational Details


Centrifugal Compressor Theory



Centrifugal Principle



Centrifugal Head


VAP

OR

PS

HE

AD

–FE

ET

PD

Discharge (outlet)pressure

Suction(inlet) pressure

Head can be picturedas the height of a columnof refrigerant vapor which,due to its weight, producesthe same pressure as thatdeveloped across thecompressor.


To condense, refrigerantmust be warmer than theleaving condenser water.

SCT = 95F + 2F approach= 97F

To boil, refrigerant must becolder than the leaving

chilled water.SST = 44F – 2F approach

= 42F

44F

Lift is Based On Leaving …

Lift = SCT less SST Saturated temperatures aresurrogates for pressures

95F

44F

85F

54F

Lift


Lift

Lift 55°F

Sat. Condensing = 97° F

Sat. Suction = 42° F


PRES

SUR

E

ENTHALPY


Compressor Input kW ~Mass Flow X Lift

ChillerCoolingTower

Compressor/CycleEfficiency

CHILLER ENERGY (KW) ~ TONS X LIFT

Like pumps, chiller energy consumption is a function of mass flow anddifferential pressure.

Lift


Lift Reduction


Sat. Suction = 42° F


Lift = 35° F


Lift 55°F

PRES

SUR

E

ENTHALPY


Centrifugal Compressor MapH

ead

Fact

or

Flow Factor

Load lineplotted on

compressor map

StoneW

all


100%75%

50%25%


Centrifugal Compressor Stages


Single-Stage Design(one impeller)

EarlierMulti-Stage

Design


SECTION 7

Capacity Control Methods



Centrifugal Chiller Capacity Control - IGV

GuideVane

Motor

InletShroud

InletGuideVanes

Impeller

Section 7 – Capacity Control Methods


Capacity Control - IGV

InletGuideVanes

Closed



Centrifugal Compressor Efficiency Characteristics

Constant Speed Centrifugal

Open Vanes

50% Vanes

Efficiency90%

80%

70%

60%

25% Vanes

10% Vanes

Capacity (Tons)

Lift



Screw Capacity Control Methods

SLIDE VALVE METHODInfinite Capacity Control

PORT VALVE METHODStepped Capacity Control


Step ValvesSlide Valve


Affinity Laws for Centrifugal Loads


Flow ~ Speed

% rpm

%Fl

ow

Lift ~ Speed2

% rpm

%Pr

essu

re/H

ead

Power ~ Speed3

% rpm

%In

putP

ower


Constant Speed kW/ton VFD kW/ton

VFD Saves Energy

0.2800.3300.3800.4300.4800.5300.5800.6300.6800.7300.7800.8300.880

20% 30% 40% 50% 60% 70% 80% 90% 100%

Percent Full Load Tons

kW/t

on


Typical 500-Ton Centrifugal Chiller


Centrifugal Compressor Efficiency Characteristics

Lift

Capacity (Tons)

90%

100%

80%

100%90 %

70%60% SpeedEfficiency

Variable Speed CentrifugalNew operatingNew operatingcharacteristics

created byspeed reduction



SECTION 8

Refrigerant Related Topics



HCFC Phase Outs

1990 1995 2000 2005 2010 2015 2020 2025 2030

35 % ( 2010)10 % (2015)

0.5% (2020)

65% (1 Jan 2004)

CurrentMontrealProtocol

Production Cap

123No New R-123Equipment

Section 8 – Refrigerant Related Topics

No New R-22Equipment


Chiller Construction


Large R-134a chillersare constructed in accordance with

ASME Section VIII, Division I


Chiller Size Refrigerant Impact

HCFC22

HFC134a

HCFC123

HFC410A


Chiller size is affected byrefrigerant molecular size.


Exp

osur

eLi

mits

Safety

Allowable Exposure Limits

HFC-134a1000 ppm

HCFC 123

50 ppm


25 ppmAmmonia


Lower Toxicity Higher Toxicity

A3Propane

B3

B2Ammonia

A2R-142b, 152a

A1R-11, R-12, R-22,

R-114, R-500, R-134a

B1R-123, SO2

LowFlammability

HighFlammability

No FlamePropagation

Refrigerant Safety Groups


ASHRAE Standard 34


SECTION 9

Heat Transfer



Heat Transfer - Condenser

Section 9 – Heat Transfer

Refrigerant Temperature

Tem

pera

ture

“t"

t1

tRt2

tR

DtEnt

Dt Lvg

The refrigerant is changingfrom a gas to a liquid and isreleasing its latent heat ofcondensation


Heat Transfer - Evaporator


tRRefrigerant TemperatureTe

mpe

ratu

re“t" t1

DtEnt

tR

t2Dt

Lvg

The refrigerant is changingfrom a liquid to agas while absorbing itslatent heat of vaporization


Chiller Equation for Tons

24tgpmtons FD*=

24tgpmtons FD*=


gpm = Flow rate for evaporator or condenserDtF = Difference in fluid entering and leaving24 = Conversion to tons for fresh water


Heat Transfer

RMW

e

F

RRRRU

ttLog

tLMTD

LMTDAUq

F

Lvg

Ent

+++=

÷øö

çèæDD

D=

**=

/1


Overall Heat Transfer Exchanged

Log Mean Temperature Difference

Heat Transfer Coefficient


HEAT OFCONDENSATION

HEAT OFVAPORIZATION

t2

t2

t1t1

Saturated Suction Temperature (tR)


Saturated Condensing Temperature (tR)

Overall Heat Transfer

DtLvg

DtLvgDt

Ent

DtEnt


Typical Resistances to Heat Transfer - Baseline


HEAT TRANSFER RESISTANCES BETWEENFLUID IN THE TUBES AND THE REFRIGERANT

0.000469

0.000250

0.000029

0.000277

0.001025

RW

RF

RM

RR

RT

46%

24%

3%

27%

100%

Fluid Film

Fouling

Tube Material

Refrigerant Film

Total


0.000469

0.001000

0.000029

0.000277

0.001775

RW

RF

RM

RR

RT

26%

56%

2%

16%

100%

Resistances with Increase in Fouling


Fluid Film

Fouling

Tube Material

Refrigerant Film

Total


Fouling is the build-up of deposits on tube surfaces anddepends on the quality of water (i.e., dirty river, etc.)

• Expressed as a number(0.00025 or 0.0005 or 0.002)

• Minimal in evaporators– Closed piping circuit

• Greater in condensers

• ARI 0.00025 fouling factor– Basis of chiller ratings

for condensers– For evaporators 0.0001

• Lower water velocitiesresult in higherfouling rates

RefrigerantFilm RR

Metal RM

Water Film RW

Refrigerant

Fouling (Scaling Resistance) RF

Scale(Fouling) RF

Water in Tube

Resistant Layers

Water

Hea

tFlo

w



Resistances With Lower Water Velocity in Tubes


0.000985

0.000250

0.000029

0.000277

0.001541

RW

RF

RM

RR

RT

64%

16%

2%

18%

100%

Fluid Film(4 fps velocity)

© 2013 Carrier CorporationSection 9 – Heat Transfer

Resistances With Tube Material Change

0.000469

0.000250

0.000350

0.000277

0.001346

RW

RF

RM

RR

RT

35%

18%

26%

21%

100%

70 – 30 CuNiTube Material


Evaporator Tubing Materials Chart

Tubing Materials Chart

Application Tube Material Approximate Cost Multipliervs. Copper Tubes

Fresh Water Copper 1.0

Glycols Copper 1.0

Corrosive Water Cupro-Nickel 1.3

Special Process Stainless Steel 2 to 3

Sea Water Titanium or Cupro-Nickel 3 to 4



Shell-and-Tube Heat Exchanger Tubing


INTERNALLY ANDEXTERNALLY ENHANCED

Condenser TubingEvaporator Tubing


Pass Arrangements

One-Pass AREA = A

Two-PassAREA = A/2

Three-PassAREA = A/3

Low Pressure Drop,Low Rise

Medium Pressure Drop,Medium Rise

High Pressure Drop,High Rise



SECTION 10

Codes and Standards



ARI Weighting Factors

PercentChillerLoad

EnteringCondenser

TempPercent

Weighting

100 85 175 75 4250 65 4525 65 12

Section 10 – Codes and Standards

FOR IPLV CALCULATION


ASHRAE 90.1 and T24 Standard


*kW/TON =

3.516/COP

WATER CHILLING PACKAGES-MINIMUM EFFICIENCY REQUIREMENTS


ASHRAE 90.1 and T24 Standard


Adjustment Formula for Minimum Efficiency Standards

0.540

0.560

0.580

0.600

0.620

0.640

0.660

9 10 11 12 13 14 15

Condenser Delta T

IKW

/Ton

Req

uire

d


ASHRAE Standard 15

Run piping frompurge and rupture

disk to outside

Provide a mechanical room if theamount of refrigerant used

exceeds ASHRAE 15 table values

Install dedicated mechanicalroom ventilation fan

Eliminate any passagesallowing refrigerant to

escape into the building

Store refrigerant inapproved storage

vessels only

Restrict mechanicalroom access to

authorized personnel


Size relief linesper ASHRAE 15 Use a tight fitting

mechanical room door

Terminate discharge linesaway from air intakes

Install refrigerantleak detectorinterlocked toventilation fan

and alarm


SECTION 11

Selection Criteria



Centrifugal Chiller Input Screen 1

Section 11 – Selection Criteria


Centrifugal Chiller Input Screen 2

Section 11 – Selection Criteria


SECTION 12

Summary



Summary

Section 12 – Summary

• Compared the advantages of water-cooledversus air-cooled chillers

• Identified and diagrammed the differentcomponents of a basic refrigeration cycleas it applies to a water-cooled chiller

• Compared and described the differences amongscroll, reciprocating, centrifugal, and screwwater-cooled chillers and their applications

• Discussed the differences in constructionof water-cooled chillers of various sizes

• Identified the codes and standardsthat apply to water-cooled chillers

• Reviewed the typical inputs requiredto select a water-cooled chiller


Technical Development Program

Thank YouThis completes the presentation.

COMMERCIAL HVAC CHILLER EQUIPMENT Water-Cooled...

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