Cooling Towers for District Cooling Towers for District Cooling Cooling

Georges Hoeterickx Georges Hoeterickx

Evapco EuropeEvapco Europe

Cooling Towers for District Cooling Cooling Towers for District Cooling Design considerations Design considerations

ApproachApproach : :

Difference between cooling tower water outlet Difference between cooling tower water outlet temp. and design entering wb temp.temp. and design entering wb temp.

Design considerations Design considerations Cooling tower size versus approachCooling tower size versus approach

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Approach ° F

Design considerations Design considerations

Minimum approachMinimum approach

CTI Certification under STD-201CTI Certification under STD-201

Certification is limited to thermal operating Certification is limited to thermal operating conditions….. and a cooling approach of conditions….. and a cooling approach of 2.8°C (5°F) or greater….2.8°C (5°F) or greater….

Cooling Towers forCooling Towers for District Cooling District Cooling

Cooling tower rangeCooling tower range

RangeRange : :

Difference between cooling tower water Difference between cooling tower water

inlet and cooling tower outlet temperature. inlet and cooling tower outlet temperature.

Design considerationsDesign considerations

CoolingCooling tower size versus range tower size versus range

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80% 90% 100% 110% 120% 130% 140% 150%

Range

C.T

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ize

Cooling Towers for District Cooling Cooling Towers for District Cooling

Design considerations Design considerations

Avoid recirculationAvoid recirculation : :

Bypass of warm discharge air into the cooling Bypass of warm discharge air into the cooling tower air inlet will cause capacity losses. tower air inlet will cause capacity losses.

Design considerations Design considerations

Avoid recirculationAvoid recirculation

Top of cooling tower should be at least level Top of cooling tower should be at least level with enclosure.with enclosure.

Design considerations Design considerations

Avoid recirculationAvoid recirculation

Fan discharge velocity : min. 1200 fpm Fan discharge velocity : min. 1200 fpm (6 m/sec). (6 m/sec).

Downward velocity : max. 600 fpmDownward velocity : max. 600 fpm

(3 m/sec).(3 m/sec).

Design considerations – two side Design considerations – two side air inlet air inlet

Avoid recirculationAvoid recirculation

Limit downward velocity - two side air inlet unitsLimit downward velocity - two side air inlet units

Design considerations – single air Design considerations – single air inlet inlet

Avoid recirculationAvoid recirculation

Limit downward velocity - single air inlet unitsLimit downward velocity - single air inlet units

Cooling Towers for District Cooling Cooling Towers for District Cooling Fan motors Fan motors

High efficiencyHigh efficiency 50° C Rise50° C Rise Space heatersSpace heaters

(avoid condensation) (avoid condensation) VFD compatibleVFD compatible

(insulated end shields)(insulated end shields)

Cooling Towers for District Cooling Cooling Towers for District Cooling Fan MotorsFan Motors

Use of VFD’s for fan motorsUse of VFD’s for fan motors : :

Allow to control air flow through the cooling Allow to control air flow through the cooling towertower

Safe Fan KWSafe Fan KW

Design considerations Design considerations VFD’s for fan motors VFD’s for fan motors

Energy saving ? Energy saving ?

Condenser water temp 1°FCondenser water temp 1°F

Chiller efficiency 3%Chiller efficiency 3%

Cooling tower kW = ~ 5 %Cooling tower kW = ~ 5 %

Chiller kW. Chiller kW.

Design considerations Design considerations VFD’s for fan motorsVFD’s for fan motors

Water consumption : Water consumption : Air flow Water consumption Air flow Water consumption

Plume formation :Plume formation : Air flow Plume formation tendency Air flow Plume formation tendency

Noise control @ night Noise control @ night Fan @ half speed : – 9 dBA fan noiseFan @ half speed : – 9 dBA fan noise

(60% capacity) (60% capacity)

Design considerations Design considerations

VFD’s for fan motorsVFD’s for fan motors

Min. RPM for gear Min. RPM for gear

(motor speed (motor speed ≥≥ 450 RPM) 450 RPM)

Gear with mechanical oil pump for proper Gear with mechanical oil pump for proper lubricationlubrication

Cooling Towers for District Cooling Cooling Towers for District Cooling

Cooling Tower BasinCooling Tower Basin : :

Hold circulating water of the tower. Hold circulating water of the tower.

Design considerations Cooling Tower Design considerations Cooling Tower Basin Basin

Common basinCommon basin

+ Easier basin and cooling tower construction.+ Easier basin and cooling tower construction. + No need for equalizing connection+ No need for equalizing connection

- Maintenance – sump cleaning- Maintenance – sump cleaning

Design considerations Cooling Tower Design considerations Cooling Tower Basin Basin

Individual Basin per Cell Individual Basin per Cell

+ Easier for maintance (water)+ Easier for maintance (water)

- Need equalizing between basins.- Need equalizing between basins.

- More costly construction- More costly construction

Design considerations Water Design considerations Water Outlets Outlets

Design considerations Cooling Tower Design considerations Cooling Tower Bassin Bassin

Sound mats to reduce water noiseSound mats to reduce water noise Noise reduction functionNoise reduction function number of layersnumber of layers distance mats – water in basin !distance mats – water in basin !

Sound mats will obstruct basin access : Sound mats will obstruct basin access : maintenance !maintenance !

Cost distribution main itemsCost distribution main items

Fan

Gear & Motor

Fill

Structure

Louvers

DE

Water Dis.

Fan Stack

Other

Cooling Tower StructureCooling Tower Structure

Typical requirementsTypical requirements: :

Cooling Towers for District CoolingCooling Towers for District CoolingFRP StructureFRP Structure

Reputable manufacturers have their Reputable manufacturers have their components third party tested percomponents third party tested per

ASTM E 84 for strength values and ASTM E 84 for strength values and flamabilityflamability

Ask if these evidences are part of contract Ask if these evidences are part of contract submittals ! submittals !

FRP StructureFRP Structure

Boron Free Advantex glass assuresa longer life of the structure

FRP StructureFRP StructureObtain the specified qualityObtain the specified quality

FRP StructureFRP Structure

UV protectionUV protection

UV degradation and moisture penetration UV degradation and moisture penetration will have influence life time of an FRP will have influence life time of an FRP cooling towercooling tower

The UV rays will cause the decomposition of The UV rays will cause the decomposition of the polymers holding the fibre glass togetherthe polymers holding the fibre glass together

FRP structureFRP structure

UV protectionUV protection

Surface veil material of non woven polyester Surface veil material of non woven polyester fabric to prevent fiber blow outfabric to prevent fiber blow out

Surface veil creates a resin rich surface area Surface veil creates a resin rich surface area to provide enhanced UV protectionto provide enhanced UV protection

One mil thickness of surface veil =One mil thickness of surface veil = 2 – 3 years life time2 – 3 years life time

STRUCTURAL RESIN 55-25%GLASS 45-75%WOVEN ROVEN ANDCONTINUOUS GLASS250 MILS OR MORE

CORROSION BARRIERRESIN 60-70 %GLASS 30-40%MAT OR CLOTH40-60 MILS

EXTERNAL LINERRESIN RICH 80-90%GLASS 10-20% 15-20 MILSSURFACING VEIL TYPE C10-20 MIL THICKNESS

FRP structureFRP structureUV protectionUV protection

FRP structure FRP structure UV protectionUV protection

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5 10 15 20 25 30Years

Midde East Climate

European Climate

Useful life of UV projected componentsUseful life of UV projected components

FRP structure FRP structure UV protectionUV protection

How to verify UV protection qualityHow to verify UV protection quality ? ?

Have samples of different weight veil Have samples of different weight veil material for comparison.material for comparison.

Variation in the visibility of the ContiniousVariation in the visibility of the Continious

Filament Mat. Filament Mat.

FRP StructureFRP StructureFire retardancyFire retardancy

Fire resistance and damage control of the Fire resistance and damage control of the

FRP structure. FRP structure.

FRP structure FRP structure Fire retardancyFire retardancy

Design with high quality, heat resistant / fire Design with high quality, heat resistant / fire retardant resin systems, Class 1 typeretardant resin systems, Class 1 type

Specify self extinguishingSpecify self extinguishing

High glass content = minimum burn rateHigh glass content = minimum burn rate

Obtain the required qualityObtain the required qualityFRP structure FRP structure

Major part of the cooling tower cost Major part of the cooling tower cost Most critical item for the cooling tower life Most critical item for the cooling tower life

time !time !

How to obtain the required quality ? How to obtain the required quality ?

Obtain the required qualityObtain the required qualityFRP structureFRP structure

1. Demand cooling tower supplier names the FRP 1. Demand cooling tower supplier names the FRP source and ask delivery certificates from the source and ask delivery certificates from the FRP manufacturer.FRP manufacturer.

2. Reserve the right to inspect before delivery to 2. Reserve the right to inspect before delivery to verify Quality Process Map is complied with. verify Quality Process Map is complied with.

Obtain the required qualityObtain the required qualityFRP structureFRP structure

1. Demand cooling tower supplier names the FRP 1. Demand cooling tower supplier names the FRP source and ask delivery certificates from the source and ask delivery certificates from the FRP manufacturer.FRP manufacturer.

2. Reserve the right to inspect before delivery to 2. Reserve the right to inspect before delivery to verify Quality Process Map is complied with. verify Quality Process Map is complied with.

Obtain the required qualityObtain the required qualityFRP structureFRP structure

1. Demand cooling tower supplier names the FRP 1. Demand cooling tower supplier names the FRP source and ask delivery certificates from the source and ask delivery certificates from the FRP manufacturer.FRP manufacturer.

2. Reserve the right to inspect before delivery to 2. Reserve the right to inspect before delivery to verify Quality Process Map is complied with. verify Quality Process Map is complied with.

Cooling tower fansCooling tower fans

Obtain the best quality Obtain the best quality

FansFans

Fans are selected for a given airflow and Fans are selected for a given airflow and static pressure static pressure

Fan design parameters : Fan design parameters : diameter – speed – nbr and shape of blades – diameter – speed – nbr and shape of blades –

blade width blade width Fan design parameters influence :Fan design parameters influence : cost – power consumption – noise cost – power consumption – noise

Cooling tower fans Cooling tower fans

Noise definition Noise definition

Specify sound pressure Specify sound pressure

in dB(A) measured 1,5 meter in dB(A) measured 1,5 meter

above fan discharge above fan discharge

(per CTI std ATC – 128)(per CTI std ATC – 128)

Cooling tower fansCooling tower fansNoise Noise

Cooling tower fansCooling tower fans

ComparisonComparison - - 2000 ton tower - 196 m³/ sec @ 160 Pa 2000 ton tower - 196 m³/ sec @ 160 Pa pressure drop pressure drop

FanFandia dia

NbrNbrBladesBlades Rpm Rpm

TipTipspeed speed

SoundSoundPowerPower

Fan shaftFan shaftPower Power Fan Fan

ftft       m/secm/sec dB(A)dB(A) kW kW US $ US $

1414 66270.270.

88 60.560.5 100.3100.3 59.359.3 21002100

1616 77193.193.

99 49.549.5 95.695.6 53.253.2 36003600

1818 55186.186.

88 54.254.2 9999 464613501350

00

18 *18 * 44 137137 4040 86.386.3 54.954.945004500

00

Cooling tower fansCooling tower fansFan power vs cost Fan power vs cost – 2000 ton tower – 196 m³/sec @ 160 – 2000 ton tower – 196 m³/sec @ 160 Pa Pa pressure droppressure drop

Fan dia Fan dia Tower price Tower price Fan Power Fan Power

ftft %% kWkW

1414   - - - - 

1616 + 1, 25 %+ 1, 25 % - 11 % - 11 %

1818 +8 % +8 % - 22 % - 22 %

Cooling tower fansCooling tower fansComparison - Comparison - 5000 ton tower - 375 m³/ sec @ 160 Pa 5000 ton tower - 375 m³/ sec @ 160 Pa pressure droppressure drop

FanFandia dia

Nbr Nbr BladeBlade

ss Rpm Rpm Tip Tip speed speed

SoundSoundPowerPower

Fan Fan shafshaf

ttPower Power Fan Fan

ftft       m/secm/sec dB(A)dB(A) kW kW US $ US $

2222 66 226226 44.244.2 106.3106.3 106.3106.3 95009500

2626 99104.104.

88 43.543.5 97.997.9 87.187.126002600

00

2626 66 89.789.7 37.237.2 90.690.6 104.2104.260006000

00

2828 66 82.682.6 36.936.9 9090 102.3102.365006500

00

Cooling tower fansCooling tower fansFan power – noise vs cost - Fan power – noise vs cost - 5000 ton tower – 5000 ton tower – 375 m³/ sec @ 160 Pa pressure drop375 m³/ sec @ 160 Pa pressure drop

FanFandia dia

TowerTowerprice price

PowePower r

SoundSoundPower Power

ftft %% kWkW dB (A)dB (A)

2222       106.3106.3

2626 + 7 %+ 7 % - 18 - 18

% % 97.997.9

2626 20%20% -2%-2% 90.690.6

2828 + 22% + 22% -4%-4% 9090

Obtain the required quality Obtain the required quality Fan stacksFan stacks

Fan stacks Fan stacks

Material Material Height : 7– 10 ft - …Height : 7– 10 ft - …

Material : Class 1 – flame spread rating 25Material : Class 1 – flame spread rating 25 (Class II and Class III = Cheaper !)(Class II and Class III = Cheaper !)

UV resistance (gelcoat 20 mil).UV resistance (gelcoat 20 mil).

Access door or removable panel Access door or removable panel

Assembly hardware SST Assembly hardware SST

Fan stacksFan stacks

Make sure fan deck floor opening matches Make sure fan deck floor opening matches fan cylinderfan cylinder

Smooth air inletSmooth air inlet

Fan tip clearance : 0,5% fan diaFan tip clearance : 0,5% fan dia

Obtain the required qualityObtain the required qualityAir inlet louvers Air inlet louvers

Water stays in… Sunlight stays out!

Air inlet louvers Air inlet louvers

Single pass FRP Blade louversSingle pass FRP Blade louvers

Waterdroplets tend to splash out when fans Waterdroplets tend to splash out when fans are shut off. are shut off.

Sunlight still enters the cooling tower basin !Sunlight still enters the cooling tower basin !

Air inlet louversAir inlet louvers

Two pass PVC air inlet louversTwo pass PVC air inlet louvers

Minimise splash-out Minimise splash-out

Direct sunlight is blocked from the water Direct sunlight is blocked from the water inside the tower and reducing the potential inside the tower and reducing the potential for algae formation ! for algae formation !

Minimum pressure drop Minimum pressure drop

Two Pass Air inlet louversTwo Pass Air inlet louvers

Typical two pass air inlet louvers Typical two pass air inlet louvers

Obtain the required quality Obtain the required quality Drift eliminatorsDrift eliminators

Obtain the required quality Obtain the required quality

Drift eliminatorsDrift eliminators

Drift rates : 0,01 to 0,0005 % of tower flow Drift rates : 0,01 to 0,0005 % of tower flow raterate

Drift rate function of type DE, air velocity, Drift rate function of type DE, air velocity, water loading and spray nozzle types, …water loading and spray nozzle types, …

Drift eliminators Drift eliminators Quality Quality

Drift rate dependends on: Drift rate dependends on:

Waterloading Waterloading Air velocity Air velocity Spray nozzle arrangement Spray nozzle arrangement

Drift eliminators Drift eliminators

Efficiency comparisonEfficiency comparison

Drift eliminators Drift eliminators Efficiency confirmationEfficiency confirmation

Ask your cooling tower supplier names Ask your cooling tower supplier names manufacturer of DEmanufacturer of DE

Demand independent test certifications Demand independent test certifications according to accepted standardsaccording to accepted standards

Air passes through area with minimum resistanceAir passes through area with minimum resistance

Air bypass reduces cooling effectAir bypass reduces cooling effect Water loss because of higher air velocityWater loss because of higher air velocity

Drift eliminators Drift eliminators Execution on siteExecution on site

Drift lossesDrift losses

Design considerations : air sealsDesign considerations : air seals

Cooling Towers FillCooling Towers FillObtain the right qualityObtain the right quality

PerformancePerformance

Cooling Tower FillCooling Tower Fill

Film Fill Design ConsiderationsFilm Fill Design Considerations

Cooling Tower FillCooling Tower Fill

Vertically Offset Flute PVC Film Fill

Cooling Tower FillCooling Tower Fill

Vertically Fluted PVC Film Fill

Cooling Tower FillCooling Tower Fill

PVCPVC Fill spacing: min 19 mmFill spacing: min 19 mm Fill thickness: 10 – 20 nils before formationFill thickness: 10 – 20 nils before formation Flamability (ASTM E84 – max 5)Flamability (ASTM E84 – max 5) Designed to accomodate operational and Designed to accomodate operational and

specified Live loadspecified Live load

Cooling Tower FillCooling Tower Fill

Cooling Towers for District CoolingCooling Towers for District Cooling

Cooling Towers for District CoolingCooling Towers for District Cooling

Obtain the specified and correct Obtain the specified and correct

quality level !quality level !

Thank youThank you

Georges HoeterickxGeorges Hoeterickx