50684234 Centrifugal Water Chillers

A Trane Air Conditioning Clinic

Centrifugal Water Chillers

Air Conditioning Clinic TRG-TRC010-ENAir Conditioning Clinic TRG-TRC010-EN© American Standard Inc. 1999


ChilledWaterSystem


absorption centrifugal

helical-rotary



period one

Components


condencondenserser

compressorcompressor

controlcontrolpanelpanel

evaporatorevaporator

components of a

Centrifugal Water Chiller

starterstarter

motormotor


Compressor


Impeller

bladesblades


volutevolute

diffuserdiffuserpassagepassage

impeller impeller passagepassagess

Centrifugal Compressor


centrifugal compressor

Energy Conversionrefrigerarefrigerant enters nt enters diffuserdiffuser

path through path through compressorcompressor

velo

c ity

velo

c ity

stati

c st

ati

c pre

ssu

repre

ssu

re

refrigerantrefrigerant enters enters impellerimpeller

refrigeranrefrigerant enters t enters volutevolute


Multistage Compressor


Condenser

bafflebaffle

tubetubebundlebundle

liquid liquid refrigerarefrigerantnt

refrigerant refrigerant vaporvapor

coolincooling g

tower tower waterwater


totoevaporatorevaporator

orifice platesorifice plates

HH11

expansion device

Orifice Plates


expansion device

Orifice Plates

HH22

totoevaporatorevaporator

orifice platesorifice plates


2-stage chiller

Economizer

refrigerant refrigerant vapor to vapor to second stagesecond stageof of compressioncompression

liquid liquid refrigerant refrigerant to to evaporatorevaporator

orificeorificeliquid liquid refrigerant refrigerant from from condensercondenser


3-stage chiller

Economizer

liquid liquid refrigerant refrigerant to to evaporatorevaporator

orificeorifice

orificeorifice

refrigerant refrigerant vapor to vapor to second stagesecond stageof of compressioncompression

refrigerant refrigerant vapor to third vapor to third stagestageof of compressioncompression

liquid liquid refrigerant refrigerant from from condensercondenser


Evaporator

eliminatoeliminatorr

liquidliquiddistributdistributoror

orifice orifice systemsystem

liquid liquid refrigerantrefrigerant

tube bundletube bundle

chilled chilled water water returnreturn


Motor

impellersimpellers

impellerimpeller

motormotor

motormotorgear-drive

direct-drive

gearsgears


Hermetic Motor Cooling

statorstator

rotorrotor

draindrainliquidliquidrefrigerarefrigera

ntnt


Controls and Starter


starterstarter


Starters

remote-mounted

starterstarter

line line powerpower

control control power wiringpower wiring

unit-mounted

line line powerpower

control control power wiringpower wiring



period two

Refrigeration Cycle


2-stage centrifugal chiller

Refrigeration Cycle

condenscondenserer

evaporatevaporatoror

expansion expansion devicesdevices

economieconomizerzer

2-stage2-stagecomprescompres

sorsor


Pressure-Enthalpy (p-h) Chart

enthalpyenthalpy

subcooledsubcooledliquidliquid mixture mixture

of liquid of liquid and and vaporvapor

15.5 15.5 Btu/lbBtu/lb[201.0 [201.0 kJ/kg]kJ/kg]

pre

ssure

pre

ssure

superheatedsuperheatedvaporvapor

BA5 psia5 psia[0.034 [0.034

MPa]MPa]

92.4 92.4 Btu/lbBtu/lb[380.4 [380.4 kJ/kg]kJ/kg]



Refrigeration Cycle

11

2233

4466

77pre

ssu

repre

ssu

re

enthalpyenthalpy

evaporaevaporatortor

condenscondenserer

2-stage 2-stage compresscompressoror

expansiexpansion on devicesdevices88

99PPee

PPcc

PP11

55economizeconomizerer



Refrigeration Cycle

11

22pre

ssu

repre

ssu

re

enthalpyenthalpy


condenscondenserer

PPee

PPcc

PP11

C B A

66

77

99

55


economizeconomizerer

33

44expansiexpansion on devicesdevices

1010

88


pre

ssure

pre

ssure

temperaturetemperature

HCFC-HCFC-2222

HCFC-HCFC-123123atmospheatmosphe

ricricpressurepressure

Refrigerant Operating Pressures

HFC-HFC-134a134a


Low-Pressure Chillers

compressorcompressorsuction suction

elbowelbow



Purge System


Purge Operation

filtratiofiltration n canistercanister

refrigerrefrigerant ant

vapor vapor from from

condencondenserser

to to condensecondenserr

filter filter drierdrier

purge purge evaporaevapora

tor coiltor coil

purge purge tanktank to to

chiller chiller vent vent lineline



period three

Compressor Capacity Control


Inlet Vanes

inlet inlet vanesvanes impellerimpeller


Multistage Compressor

inlet vanes inlet vanes

impellers impellers


VVrrRR

VVtt

Impeller


Impeller Dynamics

diametediameterr

VVrr ∝ refrigerant flow refrigerant flow

raterate

VVt t ∝ rotational speed × rotational speed ×

diameterdiameter

rotatiorotational nal speedspeed

VVrrRR

VVtt

refrigerrefrigerant flow ant flow raterate


Compressor Unloading

VVrrRR

VVtt

VV

rrVVtt

full load part load

RR


VVrr

VVtt

Surge

VVr r < static < static

pressurepressure

RR


Compressor Map

2525

7575

1010 1414

6363

pre

ssu

re

pre

ssu

re

diffe

r en

cediffe

r en

ce

refrigerant flow refrigerant flow raterate

surgesurge

vane vane positionposition

(degrees)(degrees)

9090

3636

5151


Operating Pointpre

ssu

re

pre

ssu

re

diffe

r en

cediffe

r en

ce


operatioperatingngpointpoint


compressor map for a 2-Stage Compressor

2525

7575

1010 1414

6363

pre

ssu

re

pre

ssu

re

diffe

r en

cediffe

r en

ce


surgesurge 9090

3636

5151

operatioperatingngpointpoint


(degrees)(degrees)


compressor map for a 2-Stage Compressor

2525

7575

1010 1414

6363

pre

ssu

re

pre

ssu

re

diffe

r en

cediffe

r en

ce


surgesurge 9090

3636

5151

C B

A

unloading unloading lineline


Adjustable-Frequency Drivespow

er

pow

er

con

sum

pt i

on

con

sum

pt i

on

loadload

inlet vanes inlet vanes onlyonly

AFD + inlet AFD + inlet vanesvanes



period four

Maintenance Considerations


Maintenance Considerations

▲ Operating log

▲ Mechanical components

▲ Heat-transfer surfaces

▲ Fluid analysis


operating log

ASHRAE Guideline 3▲ Chilled water inlet and outlet

temperatures and pressures

▲ Chilled water flow

▲ Evaporator refrigerant temperature and pressures

▲ Evaporator approach temperature

▲ Condenser water inlet and outlet temperatures and pressures

▲ Condenser water flow

▲ Condenser refrigerant temperature and pressures

▲ Condenser approach temperature

▲ Oil pressures, temperature, and levels

▲ Addition of refrigerant

▲ Addition of oil

▲ Vibration levels


maintenance considerations

Mechanical Components

▲ Required maintenance◆ Compressor and motor: no maintenance required

◆ Controls: no maintenance or calibration required

▲ Recommended maintenance◆ Visually inspect overall unit

◆ Inspect safety controls and electrical components

◆ Tighten electrical connections

◆ Check for leaks


▲ Other design-specific requirements◆ Change oil when oil analysis dictates

◆ Replace oil filter periodically

◆ Replace filter drier periodically

◆ Clean oil strainers annually

◆ Check shaft alignment annually

◆ Check coupling annually

◆ Replace shaft seal every 2 to 4 years

◆ Compressor teardown inspection every 5 to 10 years


Mechanical Components



Heat Transfer Surfaces

▲ Recommended maintenance◆ Use a qualified water treatment

specialist

◆ Clean condenser tubes as needed

◆ Clean water-side strainers

◆ Test tubes every 3 years


Fluid Analysis

▲ Oil analysis◆ Conduct annual analysis to verify

system integrity

◆ Measure oil pressure drop to determine if filter needs changing

◆ Measure charge

▲ Refrigerant charge◆ Conduct analysis of refrigerant

◆ Inspect purge system


Oil Analysis

▲ Why perform regular oil analysis?◆ Helps reduce maintenance costs

◆ Detects problems without compressor disassembly

◆ Extends service life of oil charge

◆ Reduces environmental problems related to oil disposal

◆ Helps maintain compressor efficiency and reliability

◆ Helps lower refrigerant emissions



period five

Application Considerations


Condensing Temperature Control

2525

7575

1010 1414

6363

pre

ssu

re

pre

ssu

re

diffe

r en

cediffe

r en

ce


surgesurge 9090

3636

5151

B

AC


(degrees)(degrees)unloading unloading lineline


condensing temperature control

Cooling Tower Bypass

condensercondenser

bypassbypass

cooling towercooling tower

55°F55°F[13°[13°

C]C]

40°40°FF

[4°[4°C]C]

65°F65°F[18°C[18°C]]

divertindivertinggvalvevalve


evaporator water flow

Constant or Variable Flow

variablvariable- e- speed speed drivedrive

chilledchilledwater water pumppump

evaporatevaporatoror


variable evaporator water flow

Limitations

▲ Maintain minimum and maximum water flow rates through the chiller evaporator

▲ Rate at which the evaporator water flow changes must be kept below the corresponding limit to:◆ Maintain the chilled water set point control

◆ Keep the chiller on line

◆ Protect the chiller from damage


Short Evaporator-Water Loops

loadload




Short Evaporator-Water Loops

loadload



tanktank


Heat Recovery

heat-heat-recovery recovery

condensercondenser

coolincooling g

tower tower waterwater

standarstandard d

condenscondenserer


heat-recovery(dual) condenser

auxiliarycondenser

◆ No extra condenser

◆ Large base heating loads or continuous operation

◆ High hot water temperatures

◆ Controlled

◆ Chiller efficiency preserved

◆ Second, full-size condenser

◆ Large heating loads

◆ High hot water temperatures

◆ Controlled

◆ Degrades chiller efficiency

◆ Second, smaller size condenser

◆ Preheating loads

◆ Moderate hot water temperatures

◆ Uncontrolled

◆ Improves chiller efficiency

heat pump

Heat-Recovery Chiller Options


air-sideeconomizer

strainercycle

◆ Potential fouling limited to heat exchanger

◆ Requires additional heat exchanger, piping, valves, and controls

◆ Can operate simultaneously with chiller

◆ Most efficient

◆ Requires larger outdoor air, return, and exhaust duct systems

◆ Coldest water temperatures

◆ Potential fouling in chilled water loop

◆ Requires additional piping, valves, and controls

plate-and-frame heat exchanger

Free Cooling


free cooling

Refrigerant Migration

from from comprescompres

sorsor

to to comprescompres

sorsorevaporatevaporatoror

condenscondenserer


equipment certification standards

ARI Standard 550/590

▲ Purpose◆ Establish definitions, testing,

and rating requirements

▲ Scope◆ Factory designed and

prefabricated water chillers

◆ Vapor-compression refrigeration

◆ Air-cooled and water-cooled condensing


equipment certification standards

ARI Standard 550/590

▲ Standard rating conditions◆ Common system conditions for published ratings

◆ Fouling factor

▲ Integrated Part Load Value (IPLV)◆ Part-load efficiency rating

◆ Based on an “average” single-chiller installation

◆ Standard operating conditions



period six

Review


Review—Period 1

condencondenserser

compressorcompressor



starterstarter

motormotor


Review—Period 2

11

2233

4466

77pre

ssu

repre

ssu

re

enthalpyenthalpy


condenscondenserer


expansiexpansion on devicesdevices88

99PPee

PPcc

PP11

55economizeconomizerer


Review—Period 3

inlet vanes inlet vanes

impellers impellers


Review—Period 4

▲ Maintenance considerations◆ Operating log

◆ Mechanical components

◆ Heat-transfer surfaces

◆ Fluid analysis


Review—Period 5

▲ Application considerations ◆ Condensing temperature control

◆ Constant or variable evaporator-water flow

◆ Short evaporator-water loops

◆ Heat recovery

◆ Free cooling

◆ Equipment certification standards

50684234 Centrifugal Water Chillers

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