ASHRAE Standards for Cooling Towers

8/3/2019 ASHRAE Standards for Cooling Towers

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John Lane Evapco, Inc.John Lane Evapco, Inc.

Sustainability andSustainability and

Evaporative CoolingEvaporative Cooling


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ASHRAE GreenGuide definesSustainable Engineering as:

Providing for the needs of thepresent without detracting from the

ability to fulfill the needs of thefuture.

ItIts The Right Thing To Do!!!s The Right Thing To Do!!!

ASHRAE is t he eng in eer ing eng in e th a t d r i v es su st a i n ab i l i t y .


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Green Building ChoicesGreen Building Choices

Involve compromises among: Environmental goals.

Energy conservation.

Raw material conservation.

Innovative treatment and controlmethods.

Cost.


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Condenser ChoicesCondenser Choices Air CoolingAir Cooling

Economically viable onEconomically viable onsmall systems.small systems.

Uses no water onUses no water on--site.site.

Higher condensingHigher condensing

temperaturetemperature lesslessenergy efficient.energy efficient.

Typically more fans andTypically more fans and

motorsmotors mechanicalmechanical

maintenance may bemaintenance may be

higher.higher.

Water CoolingWater Cooling

Only choice on largeOnly choice on largesystems.systems.

Lower condensingLower condensing

temperaturetemperature moremore

energy efficient.energy efficient. Water use at facilityWater use at facility

offset by less water useoffset by less water use

at power plant.at power plant.

Requires treatment ofRequires treatment of

recirculated water.recirculated water.


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Lower Condensing TemperatureLower Condensing Temperature

Yields BIG Energy SavingsYields BIG Energy Savings


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Water Use at Building Offset byWater Use at Building Offset by

Reduction at Utility PlantReduction at Utility Plant

AirAir--Cooled @ 1.49Cooled @ 1.49

kWh/tonkWh/ton

Total kWh =Total kWh = 1,072,800

Utility water usage @Utility water usage @2 gal /kWh =2 gal /kWh =

2,145,6002,145,600

WaterWater--Cooled @ 0.94Cooled @ 0.94

kWh/tonkWh/ton

Total kWh =Total kWh = 676,800

Utility water usage @Utility water usage @2 gal/kWh =2 gal/kWh =

1,353,6001,353,600

Evaporation at 80%Evaporation at 80%

latent =latent = 1,036,8001,036,800 Total water usage =Total water usage =

2,390,4002,390,400

400-ton at 1,800 hr/yr equivalent full load


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Significant COSignificant CO22 ReductionsReductions

Using waterUsing water--cooling on one 400cooling on one 400--

ton system saveston system saves396,000 kWh per year.per year.

US average generation is 1.55US average generation is 1.55

pounds COpounds CO22/kWh/kWh

Annual reductions ofAnnual reductions of

307 tons CO2.


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Cooling TowersCooling Towers

Primary GoalPrimary Goal remove heat fromremove heat from

water under specific conditions.water under specific conditions.

Secondary GoalSecondary Goal perform in anperform in an

energy efficient, water efficient, andenergy efficient, water efficient, andenvironmentally sound manner.environmentally sound manner.

Two general types of towersTwo general types of towers CounterflowCounterflow andand CrossflowCrossflow


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CrossCross--flow Schematicflow Schematic

Hot waterdeck

Inlet airslats


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CrossCross--flow Cooling Towerflow Cooling Tower


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CrossCross--flow Cooling Towerflow Cooling Tower


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CounterCounter--flow Schematicflow Schematic

DriftEliminator

Inlet AirLouvers

Fill

Spray Header


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CounterCounter--flow Towerflow Tower


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CrossCross--flowflowCombinationCombination

Fill & Drift EliminatorFill & Drift Eliminator


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CrossCross--flowflow CombinationCombination

Air Inlet, Fill & Drift EliminatorAir Inlet, Fill & Drift Eliminator


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CounterCounter--flowflow FillFill


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CounterCounter--flowflowDrift EliminatorDrift Eliminator


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Cooling Towers Conserve WaterCooling Towers Conserve Water

Cold water 1,184 gpm

Evaporation 12 gpm

Warm water 1,200 gpm

Blowdown 4 gpm

Air 90,000 CFM


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Traditional Water TreatmentTraditional Water Treatment

BiocidesBiocides

OxidizingOxidizing chlorine or brominechlorine or bromine

NonNon--oxidizingoxidizing

Corrosion InhibitorsCorrosion Inhibitors Scale InhibitorsScale Inhibitors


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Potential Release PathwaysPotential Release Pathways DriftDrift tower water dropletstower water droplets

entrained in cooling air.entrained in cooling air. Blowout/splashoutBlowout/splashout wind carriedwind carried

tower water.tower water.

Spills and LeaksSpills and Leaks Blowdown or BleedBlowdown or Bleed intentionalintentional

discharge of tower water.discharge of tower water.

Chemical releases and emissionsChemical releases and emissions

NoiseNoise particularly fan noise.particularly fan noise.


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DriftDrift Entrainment of waterEntrainment of water

droplets in air.droplets in air. Contains all theContains all the

chemicals and bacteriachemicals and bacteria

in the tower water.in the tower water.

Described as a % ofDescribed as a % ofrecirculating waterrecirculating water

flow.flow.

Ranges from 0.02% toRanges from 0.02% to0.001%.0.001%.

1,0301,0300.001%0.001%

5,1805,1800.005%0.005%

20,72020,7200.02%0.02%

Total DriftTotal Drift

Gal/yrGal/yr

Drift RateDrift Rate

400-ton Tower

1,800 hours


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Excessive DriftExcessive Drift


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Legionella Transmission

Microbial Associations

NutrientsBiocidesSystem Cleanliness

Temp., pH,

NutrientsMicrobial Associations

Temp., Humidity,Droplet Production

Factors

Environmental

2

Amplification

1

Survival inReservoir (Nature)

3Dissemination

(Aerosolization)

Events

6

Multiply inHuman

Phagocytes

7Diagnosis ofLegionnaires

Disease

5

Susceptible HostExposure

Events

Clinical

Virulence

SymptomsLab Tests

Surveillance

Age

DiseaseImmunodeficiency

Factors

4Transmission

HumidityDroplet Size

Distance

Risk

Minimization(Prevention)


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AWTAWTLegionellaLegionellaTransmissionTransmission


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Basin Splashout and SpillsBasin Splashout and Spills

Strong cross windsStrong cross winds

Slat inlet air louvers with no fan loadSlat inlet air louvers with no fan load Clogged nozzles in hotClogged nozzles in hot--water basinwater basin

Flooding at shutdownFlooding at shutdown Improperly designed equalizersImproperly designed equalizers

Old or damaged equipmentOld or damaged equipment

Uncontrolled Discharges


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Gravity Flow WaterGravity Flow Water

Distribution SystemDistribution System

If nozzles clog, basin will overflow.If nozzles clog, basin will overflow.

With slat inlet louvers water can splash outWith slat inlet louvers water can splash outunder nounder no--fan conditions.fan conditions.


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Spills and SplashoutSpills and Splashout -- CounterflowCounterflow

No Overflowwith SprayHeaders

Water inside

louvers


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Overflow at ShutdownOverflow at Shutdown


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LeaksLeaks


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BlowdownBlowdown Intentional discharge of water.Intentional discharge of water.

Contains all the residual chemicalsContains all the residual chemicals

and microbes in the tower.and microbes in the tower.

Usually discharged to the sewerUsually discharged to the sewertreatment systems (POTW).treatment systems (POTW).

POTW discharges to rivers orPOTW discharges to rivers orgeneratesgenerates sludgessludges that are recycled.that are recycled.


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Where Do the Chemicals Go?Where Do the Chemicals Go?


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Poor Condenser Water Piping & PracticePoor Condenser Water Piping & Practice

Dead LegsDead Legs

Infrequent useInfrequent use

loopsloops Plate andPlate and

Frame HeatFrame HeatExchangersExchangers

Chiller LeadChiller Lead--LagLag

ProtocolProtocol


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Poor Equalizer Piping =Poor Equalizer Piping =

Harsher BiocidesHarsher Biocides

Nocleanout

BottomConnection

Low-flow

Legs


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Algae GrowthAlgae GrowthHarsher BiocidesHarsher Biocides

Sunlight intobasin promotesalgae growth


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Sound Reduction TechnologySound Reduction TechnologySound Reduction Technology

Alternate FansAlternate Fans5 feet above the fan5 feet above the fan

99--1515 dB(AdB(A) Reduction) Reduction


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Choices in Evaporative CoolingChoices in Evaporative Cooling

GreenGreenbiocides e.g. hydrogen peroxide, ozonebiocides e.g. hydrogen peroxide, ozoneor nonor non--chemical techniques.chemical techniques.

GreenGreencorrosion inhibitors instead of zinc andcorrosion inhibitors instead of zinc andmolybdenates.molybdenates.

High efficiency drift eliminators.High efficiency drift eliminators.

Keep sunlight off of basin and minimizeKeep sunlight off of basin and minimizedeaddeadlegslegs..

Low sound fans.Low sound fans.

Good maintenance practices.Good maintenance practices.


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Water Treatment GoalsWater Treatment Goals Control Biological GrowthControl Biological Growth

Control Scale FormationControl Scale Formation

Minimize CorrosionMinimize Corrosion

Reasonable CostReasonable Cost

Minimize Environmental, Health andMinimize Environmental, Health and

Safety ImpactSafety Impact

These goals are being achievedwith some non-chemical methods.


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Physical Water TreatmentPhysical Water Treatment

Ashrae issued a research report onAshrae issued a research report onscale control in 2002.scale control in 2002.

Ashrae is developing a researchAshrae is developing a researchprogram to investigate biologicalprogram to investigate biologicalcontrol.control.

A variety of technologies areA variety of technologies arecommercially availablecommercially available somesome

eliminate all chemical additions.eliminate all chemical additions. Blowdown may be used for irrigation.Blowdown may be used for irrigation.


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PulsedPulsed--Power Water TreatmentPower Water Treatment The most successful physical waterThe most successful physical water

treatment technologytreatment technology Low power requirementLow power requirement

Continuous water treatment of 100%Continuous water treatment of 100%of the circulating waterof the circulating water


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Pulsed PowerPulsed Power

FDA Approved for Pasteurization.FDA Approved for Pasteurization.

Independent StudiesIndependent Studies

Sacramento Municipal UtilitySacramento Municipal Utility

District AlcoaDistrict Alcoa on performanceon performancein thein the field.field.

Several thousand successfulSeveral thousand successfulinstallations in the U.S.installations in the U.S.


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PulsedPulsed--Power Water TreatmentPower Water Treatment

Corrosion

Solve all Three Critical Challenges

of Treating Water Cooled Systems-Without Chemicals:

Scale Biological


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Result:Result:

Without Pulsed-Power With Pulsed-Power

Controls ScalingControls Scaling

Precipitation occurs on the seedsPrecipitation occurs on the seeds

not on heat transfer surfaces suchnot on heat transfer surfaces suchas chillers or condenser tubes.as chillers or condenser tubes.


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Powder Formation Instead of Scale

Biological ControlBiological Control - ElectroporationElectroporation


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Pulsed Electric Fields CreateHoles in Cell Walls

Biological ControlBiological Control -- ElectroporationElectroporation

FDA Approved Method ofCold Pasteurization

B C S


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Growing particlesagglomeratebacteria and

other smallparticles.

Biological ControlBiological ControlSedimentationSedimentation

C i C lC i C t l


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Eliminates acids for scalecontrol.

Eliminates oxidizing biocides

(chlorine, bromine).

Corrosion ControlCorrosion Control

Elimination of ChemicalsElimination of Chemicals


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Operation CharacteristicsOperation Characteristics

Operates at benign pH of 8.0to 9.0.

Operates at saturation ofcalcium carbonate.

Eliminates microbial influencedcorrosion (MIC).

P i W t T t tP i W t T t t


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Fluid cooler maintainsR&D cold room.

Cooler operated withchemical treatment @ 2cycles.

Heavy scale formed on

tubes, basin, and louvers.

Biological activitymeasured between

10,000 and 100,000CFU/ml.

Previous Water TreatmentPrevious Water Treatment

P l d P T t t


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Pulsed- PowerStarted

Biological Results

0

10,000

20,000

30,000

40,000

50,000

8/18/0

5

8/25/0

5

9/1/0

5

9/8/0

5

9/15/0

5

9/22/0

5

9/29/0

5

10/6/0

5

10/13/0

10/20/0

5

10/27/0 11

/3/0

5

11/10/0

Date

HPC

CFU/m

l

.

Reduced blowdown by

over 50%. Biological growth 1%

of previous levels.

Basin scalecompletely removedafter 2 months.

After 1 year tubes are

starting to de-scaleand biological controlcontinues.

Pulsed-Power Treatment


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SummarySummary Evaporation is the most energyEvaporation is the most energy

efficient form of cooling.efficient form of cooling.

Systems with reduced noise, driftSystems with reduced noise, driftand spill potential are available.and spill potential are available.

Good maintenance and operationalGood maintenance and operationalpractices are essential.practices are essential.

The environmental impact of waterThe environmental impact of watertreatment should be considered.treatment should be considered.

Documents

ASHRAE Standards for Cooling Towers