Air-Cooled Chillers

Copyright © Carrier Corp. 2005

COMMERCIAL HVACCHILLER EQUIPMENT

Air-Cooled Chillers

PRESENTED BY:

Omar Rojas

SalesEngineer

Technical Development Program


Section 1 IntroductionSection 2 Basic Refrigeration CycleSection 3 Air-Cooled Chiller ComponentsSection 4 Chiller ControlsSection 5 Air-Cooled Chiller ConfigurationsSection 6 Application TopicsSection 7 Options and AccessoriesSection 8 Codes and Standards

Section 9 Summary

Menu


SECTION 1

Introduction

AIR-COOLED CHILLERS


Objectives

• List the various types and tonnages ofair-cooled chillers and theiroperational characteristics

• Describe the correct applications forair-cooled chillers

• Identify the available options and accessories

Section 1 – Introduction


Air-Cooled Chiller Package

Packaged Unit

=


Air-CooledCondenser

Evaporator(cooler) Barrel

Compressor(s)

ExpansionDevice


Design Air Inlet Temperature 95° F

Air Rise 15° F

Leaving Difference* 15° F

Refrigerant Condensing Temperature 125° F

* Difference betweencondensing temperatureand leaving air

125° FCondensingTemperature

Air-Cooled Condensing Temperature



Air-Cooled Chiller Advantages– Lower installed cost– Quicker availability– No cooling tower or condenser

pumps required– Less maintenance– No mechanical room required

Water-Cooled Chiller Advantages– Higher efficiency– Custom selections in larger sizes– Large tonnage capabilities– Indoor chiller location– Longer life

Air-Cooled vs. Water-Cooled Chillers



Cooling Tower

CondenserWater Pump

Water-Cooled Chiller System Requirements

Condenser Water Pipingand Chemical Treatment

Water-Cooled ChillerWater-Cooled Chiller



Condenser Water Pipingand Chemical Treatment

Cooling Tower

CondenserWater Pump

Air-Cooled Chiller System Requirements

Water-Cooled ChillerWater-Cooled Chiller

Air-CooledChiller

Air-CooledChiller



SECTION 2

Basic Refrigeration Cycle

AIR-COOLED CHILLERS


Air-Cooled Refrigeration Cycle

*Flooded cooler, which has water in the tubes, is also used

Section 2 – Basic Refrigeration Cycle

WaterOutlet

WaterInlet

Water in Shell

Air-CooledCondenser

Compressor(s)• Scroll• Reciprocating• Screw

Evaporator

Thermal or ElectronicExpansion Device

Filter Drier

Condensed (liquid)Refrigerant

Heat Rejection to Atmosphere

Suction Line

Hot GasDischargeLine

Water-in-Shell


SECTION 3

Air-Cooled Chiller Components

AIR-COOLED CHILLERS


Air-Cooled Chiller Components• Cooler / Evaporator

– Refrigerant to water– Removes heat from chilled water loop

• Condenser– Refrigerant to air– Rejects heat to atmosphere

• Compressor– Transfers heat to condenser– Reciprocating, scroll, screw and centrifugal types

• Expansion Device– Maintains high-to-low side pressure differential– Provides proper superheat of the gas

to the compressor

Section 3 – Air-Cooled Chiller Components


Three Types of Evaporators

DX Shell-and-Tube

FloodedShell-and-Tube

Brazed-Plate



Brazed-Plate Evaporator

Return water in 54° FRefrigerant out

Chilled water out 44° FRefrigerant inNote: Brazed-Plate Heat Exchangers

are also used as condensers



Direct Expansion Shell-and-Tube Evaporator

Water is in the shell

Internal bafflingdistributes waterover the tubes

Refrigerantflows throughthe tubes

Water ConnectionFlange



Flooded Shell-and-Tube Evaporator


Refrigerant floodsthe tubes

Suction tocompressor inlet

Refrigerantvapor

Water in tubes

Refrigerant inthe shell

44° F

54° FChilled water out

Return water in


Flooded Shell-and-Tube Pass Arrangements

One-Pass AREA = A

Two-Pass AREA = A/2

Three-Pass AREA = A/3

Low Pressure Drop,Low Rise

Medium Pressure Drop,Medium Rise

High Pressure Drop,High Rise



Condenser

Air-Cooled Chiller

Vertical DischargePropeller Fans

Aerodynamically designedcondenser fan deck



Four types of compressors used in air-cooled chillers:– Reciprocating (obsolete)– Scroll– Screw– Centrifugal

Compressor Types



Horizontally Mounted TXV

SuperheatSensing Bulb


Mixed Phase toEvaporator

Liquid Line


EXV Expansion Device

Mixed Phase toMixed Phase toEvaporator

Stepper MotorStepper Motor

Liquid LinesLiquid Lines



SECTION 4

Chiller Controls

AIR-COOLED CHILLERS


Chiller Controls and StartersStarter Types

• Across-the-Line (full voltage)• Part-Winding (soft start)• Wye-Delta (soft start)• VFD (soft start)

Capacity Control

Energy Management• Chilled-Water Reset• Demand Limit

Section 4 – Chiller Controls


Control Panel

A060ALARM - @ 09:34 10-FEB-99COOLER LEAVING FLUIDTHERMISTR FAILURE7

Hand-held


Equipment-mounted


Starter Summary Information

StartingMethod

Motor StartingCurrent as a % of

Locked RotorCurrent

Full LoadCurrent

Across-the-Line 100 600

Part Wind 65 390

Wye-Delta 33 200



Capacity Control-Cycling CompressorsMultiple Scroll Chiller Design



Capacity Control Hot Gas BypassAir-CooledCondenser

Evaporator (cooler) Barrel

Compressor

Hot GasSolenoid Valve

DischargeBypassValve

• Protects system inlow-load conditions

• Active at minimumstep of cooling only



Capacity Control Slide-Valve and VFD’s


SECTION 5

Air-Cooled Chiller Configurations

AIR-COOLED CHILLERS


Packaged Single Piece ConfigurationGround or Roof-Mounted Chiller

Evaporator

Electricaland Controls

Air Inlet toCondenser Coil

CondenserFans

Multiple ScrollCompressors

Section 5 – Air-Cooled Chiller Configurations


Remote Cooler BarrelConsult manufacturer’srecommendations for maximumseparation distance.

Outdoor packagedair-cooled chillerwith cooler removed

Field-installedrefrigerant piping

Liquid Line

Suction Line


WaterOutlet

WaterInlet

DX Evaporator

Outdoors

Indoors


Outdoor Air-Cooled Condensers(1) Per Compressor Circuit

Condenserless Split-System Chiller

Outdoors

IndoorsHot Gas

Hot Gas Liquid

Liquid

IndoorCondenserless Chiller



Condenserless Chiller

• Roof does not need to support the compressor(s)

• Lower electrical costs because the compressor iscloser to the indoor electrical panel

• More options for noise control

• Reduced freeze-up potential

Benefits of Condenserless Chiller Configurations



Indoor Chiller & Indoor Air-Cooled Condenser


Hot Gas

Liquid

Indoor CondenserlessChiller

Indoor Centrifugal FanAir-Cooled Condenser

Ducted inlet

Ducted Outlet


Indoor Chiller - Evaporative Condenser

Liquid

Hot Gas

Cold WaterBasin

Air In

Warm Air Out

Coil

Air In

Air Inlet Louvers

Spray PumpWet Deck Surface

Indoor Condenserless Chiller



Work Session – Part 1

Work Session

AIR-COOLED CHILLERS

Work Session

1. What are the four major components to the air-cooled chiller refrigeration cycle?____________________________________________________________________________________________________________________________________________________________________

2. List the three types of compressors used in air-cooled chillers.___________________________________________________________________________________________________________________________

3. List the three types of coolers or evaporators used in air-cooled chillers.


SECTION 6

Application Topics

AIR-COOLED CHILLERS


Application Topics• Typical operating limits• Effects of ambient air temperature• Effects of leaving chilled-water temperature• Variable flow minimum and maximum flow rates• Freeze protection methods• Refrigerants used in air-cooled chillers• Chiller sizing• Minimum chilled-water system volume• Parallel and series chillers• Clearances and installation

Section 6 – Application Topics


Typical Operating Limits

• Minimum Outdoor Temperature-20° F(Standard unit 0° to 32° F)

• Maximum Outdoor Temperature125° F

• Minimum Leaving FluidTemperature 15° F(Standard unit 40° F)

• Maximum Leaving FluidTemperature 60° to 70° F

• Maximum Return WaterTemperature 85° F

Check with manufacturer for unit specifics



Effects of Ambient Air Temperature

EnteringAir °F Tons kW/Ton % Change

Capacity% ChangeEfficiency

75° F 112.1 0.952 +15 +20

85° F 105.5 1.069 +8 +11

95° F 97.5 1.208 – –

105° F 89.5 1.384 -8 -15

115° F 81.2 1.621 -17 -35

125° F 73.1 1.923 -25 -60

Typical Air-Cooled Chiller Full Load



Leaving Chilled WaterTemperature °F

kW /Ton

% ChangeEfficiency

per °F

% ChangeEfficiencyFrom 44° F

44 1.237 – –43 1.253 -1.1 -1.142 1.266 -1.0 -2.241 1.280 -1.1 -3.540 1.295 -1.2 -4.6

Typical Air-Cooled Chiller at 95° F Ambient

Effects of Leaving Chilled Water Temperature



Variable Flow Minimum and Maximum Flow Rates

For variable flow, the maximum rate of changeper minute is 10% of the design flow rate.

• Flooded Cooler– Minimum flow is the gpm that corresponds to

3.0 fps water velocity in the tubes– Maximum flow results in an approximate 5° F DT in cooler– Maximum flow is approximately 5 gpm/ton

• DX Cooler– Minimum flow is the gpm that corresponds to

1.0 fps water velocity in the shell– Maximum flow results in an approximate 5° F DT in cooler– Maximum flow is approximately 5 gpm/ton



Freeze Protection Methods

• Drain the chiller loop

• Use cooler heater

• Circulate the water continuously

• Use antifreeze solution

• Combinations of the above



Freeze Damage

Burst Coil

Cracked Housing



Evaporator Barrel Heater

• Refrigerant in tubes

• Water (glycol) in shell

• Heater cable wrapped aroundthe shell

• Factory or field-installed



Freeze vs. Burst ProtectionPropylene Glycol

ProtectionTemperature (°F)

For FREEZEprotection

** % by weight

For BURSTprotection

** % by weight

+20 18 12

+10 29 20

0 35 25

-10 41 29

-20 45 30

-30 48 32

-40 52 34

**Confirm with the local glycol supplier



New refrigerants not scheduled for phase-out:

Refrigerants

R-22 phase-out:• 2010 new equipment• 2020 service

R – 410A Puron™R – 407C

R - 134a



Chiller Sizing

• Do not oversize beyond 15%

• If future expansion, add a second chiller in parallel

• Use two small chillers versus one large chillerwhenever possible



Minimum Chilled-Water System Volume

• 3 gallons per ton of chiller fornormal air-conditioning duty

• 6 to 10 gallons per ton of chillerfor process duty or low ambientunit operation

• Mount tank on return line to chiller

Volume tank may be necessary

Suggested volumetank designs



44° F64° F 54° F

Series – (Typically greater than 18° F drop)

54° F

44° F

44° F

44° F

Parallel – (Typically 18° F drop or less)


Parallel and Series Chillers


Clearances


Unobstructed height isrequired for air dischargeabove fan deck

Approximately6 ft air inlet space

Approximately 6 ftminimum spacerequired for air inlet

Consult manufacturer’sliterature for exact

requirements

Require access toelectrical paneldoor swing


Multiple Unit Separation

10 ft Minimum

Consult manufacturer’s literature for exact requirements


6 ft Minimum


SECTION 7

Options and Accessories

AIR-COOLED CHILLERS


Options and Accessories

• Low ambient operation

• Low chilled-water temperature

• Condenser coil corrosion protection

• Hydronics package

Section 7 – Options and Accessories


Low Ambient OperationControl Section of Multi-Fan Air-Cooled Chiller

Fan Speed Controllers

required for operationFan speed control

required for operationto -20° F ambient



Low Chilled Water Temperature

Brine Duty• From 40° F to 34° F leaving brine

requires field reset of chiller controls

• From 34° F to 15° F leaving brinerequires factory modification to chiller



Chiller Coil Corrosion Protection

Standard Coil(majority of applications)

Plate fin coil options:• Pre-Coated Aluminum Fins

(moderate coastal protection)

• All Copper Coils(best coastal protection)

• Electro-Coated Aluminum Fins(best coastal and industrial protection)



Copper-Fin CoilsCopper tube/copper fin coils are used for

corrosion resistance in coastal areas.



Hydronics Packages

Brazed-PlateEvaporator

Strainer

Water Inlet

Water Outlet

Balancing Valve

Flow Switch

ExpansionTank

Water Pump

Air Vent

PressureGauges


Base Supportwith Heater

(Volume tank not shown)


Pump in Hydronics Package


Pump assemblyfactory-supplied foran air-cooled chiller


Expansion Tank in Hydronics Package

The change inwater systemvolume is about1% for chilled-water systems



SECTION 8

Codes and Standards

AIR-COOLED CHILLERS


Codes and Standards

Section 8 – Codes and Standards


Codes and Standards• ARI

Air Conditioning and Refrigeration Institute– Chiller performance certification– Random testing of manufactured units for verification– ARI 550/590-98

• Latest standard for electric chillers

• ASHRAEAmerican Society of Heating, Refrigerating

and Air-Conditioning Engineers– ASHRAE 90.1

• Chiller minimum efficiency requirements– ASHRAE 15

• Safety of installations using refrigerants

• ASMEAmerican Society of Mechanical Engineers

– Pressure vessel specifications



ARI Terms• Definitions

– EER: Measurement of a chiller’s efficiencyat full load capacity

– IPLV: Calculation of a chiller’s efficiency inaddition to full load using weightedaverages at various part load points

• ARI Conditions for Air-Cooled Chillers– Leaving chilled-water = 44° F– Chilled-water flow rate = 2.4 gpm/ton– Cooler fouling factor = 0.0001 hr °F ft²/Btu– Entering air temperature = 95° F



ASHRAE Standard 15Locate reliefLocate reliefoutlets for

safe venting

Run floor drainsRun floor drainsper local code

Locate inlet ventsLocate inlet ventsaway from exhaust

outlets per code

Restrict mechanicalRestrict mechanicalroom access

SizeSizepressure

relief linesper

ASHRAE

Install tight fittingInstall tight fittingmechanical room

door

Secure chillerSecure chillerdrain valves

Minimize lowMinimize lowareas where

refrigerant mightcollect



EquipmentType

SizeCategory

MinimumEfficiency

kW/Ton

Air-cooledwith

condenser

< 150 tons> 150 tons

9.562 EER /12.5 IPLV9.562 EER /12.75 IPLV

Air-cooledwithout

condenserAll

Must be ratedwith matchingcondensers andcomply withsame efficiencyrequirements.

Current Title 24 Minimum EfficienciesAir-Cooled Chillers



Current Title 24

New central cooling plants and coolingplant expansions will be limited on the useof air-cooled chillers. For both the limit is300 tons per plant.


Current Title 24Exceptions:1. Where the water quality at the building site

fails to meet manufacturer’s specifications forthe use of water-cooled chillers.

2. Chillers that are used to charge thermalenergy storage (TES) system with a designtemperature of less than 40°F.

3. Air cooled chillers with minimum efficienciesapproved by the Energy Commission pursuantto §10-109(d).


SECTION 9

Selection Criteria

AIR-COOLED CHILLERS


SECTION 9

Summary

AIR-COOLED CHILLERS


Summary

• Listed the various types and tonnagesof air-cooled chillers and theiroperational characteristics

• Described the correct applications forair-cooled chillers

• Identified the availableoptions and accessories

Section 10 – Summary


Work Session – Part 2

Work Session

AIR-COOLED CHILLERS

Work Session

1. What are the four major components to the air-cooled chiller refrigeration cycle?____________________________________________________________________________________________________________________________________________________________________

2. List the three types of compressors used in air-cooled chillers.___________________________________________________________________________________________________________________________

3. List the three types of coolers or evaporators used in air-cooled chillers.


Technical Development Program

Thank YouThis completes the presentation.

TDP-622 Air-Cooled ChillersArtwork from Symbol Library used by permission ofSoftware Toolboxwww.softwaretoolbox.com/symbols

Air-Cooled Chillers

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