PhEn-602 - Information Services & Technologyarmenant/PhEn602-102/PhEn602-Spring09-Notes10.pdf ·...

PhEn 602 Spring 2009 1

PhEnPhEn--602602Pharmaceutical Facility DesignPharmaceutical Facility Design

J. ManfrediJ. ManfrediNotes #10Notes #10


MoistureMoisture

Methods of dehumidificationMethods of dehumidification

Limits of coolingLimits of cooling--based dehumidificationbased dehumidification

Desiccant dehumidificationDesiccant dehumidification

Types of desiccant driersTypes of desiccant driers

Application of desiccant dehumidificationApplication of desiccant dehumidification

Desiccant vs. refrigerant based Desiccant vs. refrigerant based dehumidification dehumidification –– How to decide? How to decide?


CoolingCooling--Based DehumidificationBased Dehumidification(Sensible Cooling and Dehumidification)(Sensible Cooling and Dehumidification)

70° F56 gr/lb

45° F44 gr/lb

Process airDehumidification

SensibleCooling

• Maximum moisture content is proportional to air temperature

• Cooling the air removes moisture by condensation


Direct Expansion CoolingDirect Expansion Cooling

RefrigerantExpansion Valve

Compressor Refrigerant Condenser

Liquid RefrigerantStorage

RefrigerantEvaporator

Refrigerant expandsinside the coil, removingheat from the air passing through the fins

Refrigerant is condensed backto a liquid, releasing its heatto the air passing through thecondenser coil

Compressor raises the pressureand temperature of the refrigerant gas


Chilled Water, Glycol & Brine CoolingChilled Water, Glycol & Brine Cooling

Refrigerant cools a heat transferliquid, which in turn circulatesthrough coils to cool the air

RefrigerantExpansion Valve

Compressor RefrigerantCondenser

LiquidRefrigerant

Storage

Refrigerant Evaporator(Chiller Barrel)


CoolCool--Reheat DehumidifierReheat Dehumidifier

Evaporator(Air Cooler)

Condenser(Air Heater)

Concept used in basement dehumidifiers•Cooling and dehumidifcation thru the evaporator•Sensible reheating thru the condenser


Desiccant DehumidificationDesiccant Dehumidification

With coolingWith cooling--based dehumidification, it is based dehumidification, it is possible to reach 45possible to reach 45°F°F dew point using chilled dew point using chilled water, and 40water, and 40°F°F dew point using refrigerant dew point using refrigerant (DX) coil.(DX) coil.Can achieve lower dew points (lower humidity Can achieve lower dew points (lower humidity ratios) with desiccant dehumidification than ratios) with desiccant dehumidification than coolingcooling--based dehumidification.based dehumidification.Theoretically, desiccant dehumidification runs Theoretically, desiccant dehumidification runs along a constant enthalpy line. In actuality, along a constant enthalpy line. In actuality, there is a slight rise in the enthalpy.there is a slight rise in the enthalpy.



LatentHeat

Conversion

Process airDehumidification



Moisture leaves the air stream due to difference Moisture leaves the air stream due to difference in vapor pressurein vapor pressure

Low vapor pressure at surface of desiccantLow vapor pressure at surface of desiccantVapor pressure of water in air is higher than at Vapor pressure of water in air is higher than at surface of desiccant surface of desiccant Moisture moves from the air stream to the desiccantMoisture moves from the air stream to the desiccantMost solid materials attract and hold moistureMost solid materials attract and hold moisture



Desiccants are unique Desiccants are unique –– they can hold 10they can hold 10--10,000 % their weight in water vapor.10,000 % their weight in water vapor.Desiccant vapor pressure (VP) varies with Desiccant vapor pressure (VP) varies with temperaturetemperatureAt high temp’s, VP is high, and the desiccant At high temp’s, VP is high, and the desiccant gives off vaporgives off vaporAt low temp’s, VP is lower and absorbs moistureAt low temp’s, VP is lower and absorbs moistureVapor moves from air to the desiccant and back Vapor moves from air to the desiccant and back again based on vapor pressure differencesagain based on vapor pressure differences



Process air:Process air: Air stream to be Air stream to be dehumidified is ultimately delivered to the dehumidified is ultimately delivered to the space. space. Reactivation air:Reactivation air: Air heated by thermal Air heated by thermal energy (e.g. steam, or electric coils) used energy (e.g. steam, or electric coils) used to raise the temperature of the desiccant to raise the temperature of the desiccant so that it liberates the moisture.so that it liberates the moisture.

Reactivation air regenerates the desiccantReactivation air regenerates the desiccant


Desiccant Dehumidification – the processDesiccant SorptionDesiccant Sorption


Desiccant Dehumidification – the processDesiccant ReactivationDesiccant Reactivation


Desiccant Dehumidification – the processDesiccant CoolingDesiccant Cooling


Packed Tower Desiccant DehumidifiersPacked Tower Desiccant Dehumidifiers

50° F

250° F

95° F

150° F

200° F

2

3

1

Desiccantheater

32Desorption

1 2

Sorption

1Cooling

3Desiccantcooler

Packedtower

Packedtower

Reactivation air in

Reactivation airout

ProcessAir Out

Process Air In

Mosture Content of the Desiccant


Packed Tower Packed Tower

Advantages & LimitationsAdvantages & LimitationsAdvantagesAdvantages

Very low dew points (Very low dew points (--40 to 40 to --100°F) obtained100°F) obtainedNo need for continuous reactivation in lowNo need for continuous reactivation in low--load load applicationsapplicationsProcess air can be pressurized without leakage Process air can be pressurized without leakage concernconcern

LimitationsLimitationsVery large for a given air flow comparativelyVery large for a given air flow comparatively


HoneyCombeHoneyCombe®® Desiccant DehumidifiersDesiccant Dehumidifiers

50° F

250° F

95° F

150° F

200° F

2

3

1

2 3

13

21

DesiccantHeater

Cooling

Sorption

Desorption



HoneyCombeHoneyCombe®® Dehumidifier ComponentsDehumidifier Components

ReactivationHeater

F

F

ReactivationFilter

ProcessDamper

ProcessFan

ReactivationFan

ReactivationDamper

ProcessFilter

DesiccantWheel

DesiccantDrive System

DesiccantAir Seals

ElectricalController


Rotary Rotary HorizHoriz. Bed Desiccant Dehumidifiers. Bed Desiccant Dehumidifiers

50° F

250° F

95° F

150° F

200° F

2

3

1

Horizontal rotatingdesiccant bed

32Desorption

1 2Sorption

1Cooling

3

Desiccantheater

Process AirEntering



Rotating Bed Advantages & LimitationsRotating Bed Advantages & Limitations

AdvantagesAdvantagesComparatively low first costComparatively low first costLow cost desiccant replacementLow cost desiccant replacement

DisadvantagesDisadvantagesRather large for a given air flowRather large for a given air flowParallel air flow rather than counter flowParallel air flow rather than counter flow

Required to prevent air leaksRequired to prevent air leaksUses twice as much energy as other typesUses twice as much energy as other types

Dew points below 0°F not normally practicalDew points below 0°F not normally practicalDesiccant settles & fractures, requiring replacementDesiccant settles & fractures, requiring replacementAir “channels” through the bed, reducing effective Air “channels” through the bed, reducing effective capacitycapacity


Multiple Vertical Bed Desiccant DehumidifiersMultiple Vertical Bed Desiccant Dehumidifiers

50° F

250° F

95° F

150° F

200° F

2

3

1

Multiplevertical beds

32Desorption

Desiccantheater

1Cooling

3

1 2Sorption

ProcessAir

Entering



Liquid Spray Desiccant DehumidifiersLiquid Spray Desiccant Dehumidifiers

Conditioner(Process Air)

Regenerator(Reactivation Air)Sorp tion

1 2

Cooling3 1

Cooling2 3

50° F

250° F

95° F

150° F

200° F

2

3

1



Liquid System Advantages & LimitationsLiquid System Advantages & Limitations

AdvantagesAdvantagesImmense capacity Immense capacity -- 1200 x desiccant weight in water1200 x desiccant weight in waterInternal cooling of desiccant is very energy efficientInternal cooling of desiccant is very energy efficientAir leaves at a constant, low temperatureAir leaves at a constant, low temperatureLiquid kills microbesLiquid kills microbesSingle regenerator with multiple conditioners saves first costSingle regenerator with multiple conditioners saves first costCan use lowCan use low--temperature reactivationtemperature reactivation

LimitationsLimitationsVery large, costly & complex to installVery large, costly & complex to installSensitive to maintenance & winter solidificationSensitive to maintenance & winter solidificationDew points below 15°F not normally practicalDew points below 15°F not normally practicalCorrosive desiccant can carry over into process airCorrosive desiccant can carry over into process airHigh cost of replacing desiccant solutionHigh cost of replacing desiccant solutionHighHigh--temperature reactivation energy must be reduced to a temperature reactivation energy must be reduced to a low temperaturelow temperature


HoneyCombeHoneyCombe®® Advantages & LimitationsAdvantages & Limitations

AdvantagesAdvantagesLowest dew point of all atmospheric pressure units (Lowest dew point of all atmospheric pressure units (--55°F)55°F)Lowest reactivation energy consumptionLowest reactivation energy consumptionMost reliable mechanicallyMost reliable mechanically——very low maintenancevery low maintenanceMost compact for a given air flowMost compact for a given air flowEffective across a broad range of conditions & applicationsEffective across a broad range of conditions & applicationsSeveral desiccant choices availableSeveral desiccant choices available

LimitationsLimitationsDesiccant wheel costs more than granular desiccantDesiccant wheel costs more than granular desiccantFirst cost sometimes greater than other typesFirst cost sometimes greater than other types


Comparing DehumidifiersComparing DehumidifiersBy Leaving Air Dew PointBy Leaving Air Dew Point

Air dewpoint delivered continuously ( °F )

-50 -40 -30 -20 -10 0 10 20 30 40 50 60-60

DXCooling

Chlled Water

Chilled Glycol/Brine

Liquid Spray

Packed Tower

Rotating Tray

Multiple Vertical Bed

HoneyCombe®


Cooling vs. Desiccant Cooling vs. Desiccant DehumidifiersDehumidifiers

Most economical when used in Most economical when used in combinationcombinationFactors favoring cooling based Factors favoring cooling based dehumidification:dehumidification:

Low electrical cost (below 5¢/kWH)Low electrical cost (below 5¢/kWH)Humidity control at high temperaturesHumidity control at high temperatures

Need for high relative humidity (e.g. fruit)Need for high relative humidity (e.g. fruit)


Benefits of DehumidificationBenefits of DehumidificationOperational Cost Operational Cost ReductionReduction

Interruption costsInterruption costsReRe--work costswork costsEnergy costsEnergy costsMaintenance costsMaintenance costs

Improved Product Improved Product ValueValue

Value of improved Value of improved market imagemarket imageReduced scrap rateReduced scrap rateImprovement in Improvement in propertiesproperties

Reduced Capital Reduced Capital CostsCosts

Reduced need for plant Reduced need for plant expansionexpansionReduced equipment Reduced equipment replacement costreplacement costReduced HVAC system Reduced HVAC system costcost

Operational Operational ResponseResponse

Avoid unscheduled Avoid unscheduled maintenancemaintenanceLess equipment requiredLess equipment requiredProduct value increased Product value increased by safe storage to meet by safe storage to meet peak demandpeak demand


Minimizing CostsMinimizing Costs

Minimizing Installed CostsMinimizing Installed CostsReduce moisture loadsReduce moisture loadsOptimize control levelsOptimize control levelsSpecify tolerances clearlySpecify tolerances clearlyCombine desiccant DH with cooling DHCombine desiccant DH with cooling DH

Minimizing Operating CostsMinimizing Operating CostsModulate reactivation in response to load Modulate reactivation in response to load changeschangesUse multiple systems for intermittentUse multiple systems for intermittent


Humidity Control Advantages Humidity Control Advantages

Corrosion PreventionCorrosion PreventionCondensation PreventionCondensation PreventionMold & Fungus PreventionMold & Fungus PreventionMoisture Regain PreventionMoisture Regain PreventionProduct DryingProduct DryingDry CoolingDry CoolingFood ProcessingFood ProcessingPharmaceutical ProcessingPharmaceutical Processing


Corrosion PreventionCorrosion PreventionMilitary StorageMilitary Storage

Reduces storage lossesReduces storage lossesCuts storage energy costCuts storage energy costAllows immediate equipment useAllows immediate equipment use

Lithium Battery MfgLithium Battery MfgEntire rooms at 70°F, 1% Entire rooms at 70°F, 1% rhrhVolume production now practicalVolume production now practical

Power Plant LayPower Plant Lay--upupSaves cost over nitrogenSaves cost over nitrogenReduces safety hazardsReduces safety hazardsRapid plant startRapid plant start--upup

Electronics StorageElectronics StorageMay improves MTBFMay improves MTBFMay reduce calibration frequencyMay reduce calibration frequencyMay improve reliabilityMay improve reliability


Condensation PreventionCondensation PreventionIce RinksIce Rinks

Prevents soft ice & puddlesPrevents soft ice & puddlesEliminates fogEliminates fogReduces refrigeration energyReduces refrigeration energy

Injection MoldingInjection MoldingPrevents mold sweatPrevents mold sweatCuts cycle time in halfCuts cycle time in halfLengthens mold lifeLengthens mold life

Water Treatment PlantWater Treatment PlantEliminates rustingEliminates rustingReduces painting requirementsReduces painting requirementsEliminates fungal growthEliminates fungal growth

Surface Prep & CoatingSurface Prep & CoatingCoating in any weatherCoating in any weatherNo need to coat in sectionsNo need to coat in sectionsImproves coating lifeImproves coating life


Mold & Fungus PreventionMold & Fungus PreventionArchival StorageArchival Storage

Protects organic materialsProtects organic materialsStabilizes wood artifactsStabilizes wood artifactsSaves color filmSaves color filmReduces storage energy costReduces storage energy cost

Seed StorageSeed StorageImproves GerminationImproves GerminationLengthens Storage LifeLengthens Storage LifeEliminates Eliminates AfaloxinAfaloxinImproves VigorImproves Vigor

Cargo ProtectionCargo ProtectionReduces transit lossesReduces transit lossesAvoids litigation expenseAvoids litigation expenseProtects ship structureProtects ship structure

BreweriesBreweriesImproves plant sanitationImproves plant sanitationEliminates fungal contaminationEliminates fungal contaminationImproves plant safetyImproves plant safety


Moisture Regain PreventionMoisture Regain PreventionCandy PackagingCandy Packaging

Eliminates sticking & pickingEliminates sticking & pickingReduces machine cloggingReduces machine cloggingReduces cleaning frequencyReduces cleaning frequency

Glass LaminatingGlass LaminatingReduces autoclave timeReduces autoclave timeEliminates bubbles in glassEliminates bubbles in glassSimplifies PVB filmSimplifies PVB film

Clean RoomsClean RoomsAllows nonAllows non--stop productionstop productionEliminates tablet press cloggingEliminates tablet press cloggingEliminates Eliminates photoresistphotoresist swellingswelling

Composite MfgComposite MfgSpeeds part curing timeSpeeds part curing timeEliminates vapor voidsEliminates vapor voidsExtends polyimide epoxy pot lifeExtends polyimide epoxy pot lifeImproves part strength & adhesionImproves part strength & adhesion


Product DryingProduct DryingCandy CoatingCandy Coating

Speeds production rateSpeeds production rateImproves surface finishImproves surface finishEliminates pickingEliminates picking

Plastic Resin DryingPlastic Resin DryingEliminates vapor bubblesEliminates vapor bubblesImproves part finishImproves part finishImproves part strengthImproves part strength

Investment CastingsInvestment CastingsEliminates solventsEliminates solventsSolventSolvent--speed drying ratesspeed drying ratesAvoids part deformationAvoids part deformation

Fish DryingFish DryingAvoids bacterial growthAvoids bacterial growthDries regardless of weatherDries regardless of weatherImproves product textureImproves product texture


Dry CoolingDry CoolingSupermarketsSupermarkets

Eliminates product frostEliminates product frostReduces annual energy costReduces annual energy costImproves customer comfortImproves customer comfort

Advanced HVAC SystemsAdvanced HVAC SystemsEliminates latent load at low costEliminates latent load at low costUses Uses cogencogen & waste heat& waste heatImproves refrigeration COPImproves refrigeration COP

Sick BuildingsSick BuildingsDesiccates Desiccates LegionellaLegionella bacteriabacteriaEliminates condensate scumEliminates condensate scumEliminates fungal growth in duct workEliminates fungal growth in duct work

Hotel & MotelsHotel & MotelsEliminates musty odorsEliminates musty odorsEliminates wall replacementEliminates wall replacementImproves sanitationImproves sanitation


Food ProcessingFood ProcessingCandy PackagingCandy Packaging

Avoids clogged equipmentAvoids clogged equipmentReduces cleaning frequencyReduces cleaning frequencyAllows fast wrapping with polypropyleneAllows fast wrapping with polypropylene

Spiral FreezersSpiral FreezersEliminates conveyor defrostEliminates conveyor defrostEliminates floor icingEliminates floor icingImproves refrigeration COPImproves refrigeration COP

LowLow--Temperature DryingTemperature DryingImproves product qualityImproves product qualityFast drying at low temperatureFast drying at low temperature

Candy Pan CoatingCandy Pan CoatingImproves surface finishImproves surface finishSpeeds waterSpeeds water--based dryingbased dryingEliminates picking & stickingEliminates picking & sticking

Spray Drying/Spray Drying/InstantizingInstantizingNo clogs in product collectorsNo clogs in product collectorsAllows smaller fluid bedsAllows smaller fluid bedsIncreases throughput of towersIncreases throughput of towers


Pharmaceutical ProcessingPharmaceutical ProcessingTabletingTableting PressesPresses

Eliminates moisture regainEliminates moisture regainAllows faster press speedAllows faster press speedAllows constant production Allows constant production raterate

LyophilizerLyophilizer RoomsRoomsPrevents moisture regainPrevents moisture regainAvoids need for glove Avoids need for glove boxesboxesImproves shelf lifeImproves shelf life

Spray DryingSpray DryingConsistent productionConsistent productionReduced size of fluid bedReduced size of fluid bedAllows lowAllows low--temp dryingtemp drying

Tablet CoatingTablet CoatingAllows reduction of Allows reduction of solventssolventsConsistent drying in all Consistent drying in all climates & seasonsclimates & seasons

Powder CompoundingPowder CompoundingEliminates moisture regainEliminates moisture regainSimplifies handlingSimplifies handlingImproves sanitationImproves sanitation

StorageStorageAllows low Allows low rhrh in cold in cold storagestoragePrevents cardboard regainPrevents cardboard regainExtends storage lifeExtends storage life


Calculating Moisture LoadsCalculating Moisture Loads

Choose the moisture control levelChoose the moisture control levelIdentify moisture load sourcesIdentify moisture load sourcesQuantify each load sourceQuantify each load sourceTotal the load & compare to the budgetTotal the load & compare to the budgetAdjust the calculation assumptions & Adjust the calculation assumptions & recalculaterecalculate

Key Point: The only “correct” moisture load calculation is the one made after all parties agree on all assumptions


The Importance of Design ConditionsThe Importance of Design Conditions

Room controlled at70° F @ 2% rh = 2.1 gr/lb

Surrounding spacecontrolled at

70° F @ 50% rh = 55 gr/lb

Weather condition90° F & 95gr/lb The Greater The

Moisture DifferentialThe Larger TheMoisture Load

(Just LikeTemperature)

95 gr/lb = .64"Hg

55 gr/lb = .37"Hg

2.1 gr/lb = .01"Hg

.63"HgVapor PressureDifferential

.27"Hg

.36"Hg


Choosing the Design ConditionsChoosing the Design Conditions

Inside Conditions Inside Conditions -- How Dry?How Dry?Dry enough to achieve the maximum economic benefit, and no Dry enough to achieve the maximum economic benefit, and no drierdrierHumidity control project is often the result of summer Humidity control project is often the result of summer problems. So,…what is the moisture condition during the problems. So,…what is the moisture condition during the winter when no problem exists?winter when no problem exists?When in doubt, test different conditions with a rental unitWhen in doubt, test different conditions with a rental unit

Weather Conditions Weather Conditions -- How Much Safety?How Much Safety?How many hours can you risk being out of control?How many hours can you risk being out of control?

1% of 2928 summer hours = 29 hours1% of 2928 summer hours = 29 hours2.5% of 2928 summer hours = 74 hours2.5% of 2928 summer hours = 74 hours

Extreme summer temperature usually does not coincide with Extreme summer temperature usually does not coincide with extreme moistureextreme moisture

ASHRAE weather data being revised to reflect that factASHRAE weather data being revised to reflect that fact


Estimating Weather Design MoistureEstimating Weather Design Moisture

1. 95°F db 2. 78°F wb

3. 80% rh

4. DesignMoisture137 gr/lb

Design Assumption:ASHRAE 1% Summer Design

95°F db,78°F wb

Dry bulb temperature (°F)


Moisture Load SourcesMoisture Load SourcesInternal LoadsInternal Loads

Vapor Permeation through walls, floor & ceilingVapor Permeation through walls, floor & ceilingEvaporation and respiration from peopleEvaporation and respiration from peopleDesorption from moist productsDesorption from moist productsEvaporation from wet surfacesEvaporation from wet surfacesVapor as a product of combustionVapor as a product of combustionHumid air infiltration through cracks, holes & Humid air infiltration through cracks, holes & door openingsdoor openings

External LoadsExternal LoadsVapor carried into the system by moist Vapor carried into the system by moist ventilation airventilation air


Vapor Permeation (The Smallest Load)Vapor Permeation (The Smallest Load)

Permeance (gr/hr)= P x A ∆VP( )Wp

Material permeance factor (gr/hr/sq.ft./inHg)Surface area of the material (sq.ft.)Difference in vapor pressure across the material (inHg)

0.364 inHgVapor PressureDifference

1.8 gr/lbequals

0.012 inHg

56 gr/lbequals

0.376 inHg

x


Moisture From Products & PackagingMoisture From Products & Packaging

Water vapor from products & packaging(lbs/hr)

Wpp = lbs / hr x (pw 2− pw1)

Equilibrium moisture content of material beforeentering the space (lbs/lb)

Total mass of material entering the roomevery hour (lbs/hr)

Equilibrium moisture content of material atthe control condition in the space (lbs/lb)

Relative Humidity

6%

12%

10 50 100


Batch Process LoadsBatch Process Loads

Time

Product load

Walls, floor& ceiling load

Time

Air relative humidity

Initial pull-down

Temporary equilibrium

Finalequilibrium

Walls, floor, ceiling

Batches ofmoist product

Building structure Building structure requires time to dry.requires time to dry.Product dries in Product dries in stages:stages:

Surface moisture Surface moisture --rapidrapidTemporary Temporary equilibrium equilibrium -- no no loadloadFinal drying Final drying -- low low loadload


Moisture From PeopleMoisture From People

Moisture load from respirationand perspiration (gr/hr)

Wn = (Pa x Fa) + ( Pb Fb) + (Pc F ) + (Pd Fd)Load for people at moderate work (gr/hrLoad for people at light work (gr/hr)Load for people standing (gr/hr)

Evaporation per person (gr/hr)

Number of people seatedLoad for people sitting (gr/hr)

30

40

50

60

70

80

90

100

1000 2000 3000 4000 5000 6000

Seated Standing

Light Work

Moderate Work

x x xc


Moisture From CombustionMoisture From Combustion

Gas firing rate (cu.ft./hr)

Wg=G x 650Moisture produced per cubic foot of gas burned (gr/hr)

Moisture load from gas combustion (gr/hr)


Moisture From Wet SurfacesMoisture From Wet Surfaces

Evaporation load from a wet surface (gr/hr)

= x −

Latent heat of vaporization at the water temperature(Btu/lb)

Grains of water vapor in a pound of water

Water vapor pressure in the air abovethe surface (in.Hg.)

Vapor pressure of air saturated atthe water temperature (in.Hg.)

Total surface area wetted (sq.ft.)

Latent heat transfer rate (Btu/hr/sq.ft./in.Hg.)

x x

Transverse flow (Ht)

Parallel flow (Hp)

Saturated air at the boundry layer


Air Leaks Through CracksAir Leaks Through Cracks

Moisture carried through cracksin an exterior wall (gr/hr)

Air leakage rate (cu.ft./hr/Ln.ft.)

Moisture outside the wall (gr/lb)

Moisture inside the wall (gr/lb)

Air density (lb/cu.ft.)Length of the opening (Linear ft.)Wi= Q d ( Mo − M i ) x Lxx

LessHumid

MoreHumid

PipePenetration


Typical Air Leak PathsTypical Air Leak PathsAir Handling SystemAir Handling System

Air duct jointsAir duct jointsAccess panels in air handling equipmentAccess panels in air handling equipmentVentilation louvers in doorsVentilation louvers in doorsUnused exhaust fans and backUnused exhaust fans and back--draft dampersdraft dampersWindow air conditionersWindow air conditioners

Room ConstructionRoom ConstructionWallWall--toto--ceiling, wallceiling, wall--toto--floor jointsfloor jointsCracks around doors; especially at the floorCracks around doors; especially at the floorOpen construction above suspended ceiling tilesOpen construction above suspended ceiling tilesWall penetrations for electrical boxes, conduits, Wall penetrations for electrical boxes, conduits, pipes & light fixturespipes & light fixturesVapor barrier plastic sheets, not joinedVapor barrier plastic sheets, not joined


Humid Air From Door OpeningsHumid Air From Door OpeningsRemember: pressure differences do not prevent moisture travelRemember: pressure differences do not prevent moisture travel

Morehumid

Lesshumid

Moisture load from air infiltratingthrough an opening (gr/hr)

Area of the opening (sq.ft.)

Density of the infiltrating air (lb/cu.ft.)

Minutes per hourAir velocity through the opening (ft/min)

Moisture inside the space (gr/lb)Moisture outside the space (gr/lb)

Wi =Ax d 60 Va (Mo−Mi)x x x


Humid Air From Airlock OpeningsHumid Air From Airlock Openings

Morehumid

Lesshumid

Moisture infiltration per airlock opening(gr/hr/opening)

Height, width and length of the airlock (cu.ft.)Density of air (lbs/cu.ft.)

Moisture level outside the room (gr/lb)Moisture level inside the room (gr/lb)

Wi = (h x l w) dMo

−M i

2x x x ( )


Humid Air Through Conveyor OpeningsHumid Air Through Conveyor Openings

Wi = V x A d 60 (Mo − M i)

Moisture carried by air througha conveyor opening (gr/hr)

Moisture inside the room (gr/lb)Moisture outside the room (gr/lb)Minutes per hourAir density (lb/cu.ft.)Conveyor opening area (sq.ft.)Conveyor velocity (ft/min)

x x x

Less Humid More Humid


Ducted OpeningsDucted Openings

Highvelocity

airstream

More humidLess humid LowPressure

Areas

LowPressure

Areas

Even with a high Even with a high exit velocity, exit velocity, moist air can moist air can infiltrate into a dry infiltrate into a dry roomroomTo minimize To minimize counterflowcounterflowinfiltration, move infiltration, move lowlow--pressure pressure areas away from areas away from the room by the room by ducting the ducting the openingsopenings


Humid Ventilation AirHumid Ventilation Air(The Largest Moisture Load)(The Largest Moisture Load)

Wm= Q x d 60 (Mo- Mi)

Moisture load from fresh air (gr/hr)

Sum of airflows necessary for ventilation,pressurization and exhaust air make-up

(cfm)

Air density (lb/cu.ft.)Minutes per hour

Moisture level inside the room (gr/lb)Moisture level of the fresh air (gr/lb)

x x

• ASHRAE Standard 62-1989 Defines recommended ventilation rates for commercial and residential spaces

• Industrial ventilation rates are not defined by ASHRAE because of varying contaminant levels in industrial process

• Assume ASHRAE Standard 62 as a minimum in the absence of industrial guidelines2

5

10

20

40

80

160

2000 3000 4000

Supermarket(15 cfm/person)

Hospital Patient Room(25 cfm/person)

1000Cubic Feet Per Minute Ventilation Air


The Humidity Variable In AirThe Humidity Variable In Air

Constituents of Air(Present in VARIABLE Concentrations)

78% Nitrogen 20.9% Oxygen1%

ArgonNeon

HeliumMethane

Constituents of AtmosphericAir (In STEADY Concentrations)

Water Vapor0 to 7%

OzoneSulfur Dioxide

Carbon DioxideNitrogen Dioxide

0 to 0.15%

Controlling the moisturecontent of air accountsfor a major portion ofthe $40 billionair conditioning market

KryptonHydrogenNitrous OxideXenon


Design ConditionsDesign Conditions

Elevation ________ft. above sea level—standard air density = ________lb/cu.ft.

Weather Extremes Internal ConditionsSummer Winter Room Building

Dry Bulb TemperatureDewpoint

Humidity RatioVapor pressure

GroundWater

102 18 67 70 8078 18 67 28 60

146 14 100 22 770.98 0.10 0.68 0.15 0.52

495 0.074


Vapor PermeationVapor Permeation

Wall 1Wall 2Wall 3Wall 4FloorCeiling

_________ x __________ x ( ___________ - ___________ ) = _____________ gr/hr

SurfaceArea

(sq.ft.)

PermeanceFactor

(gr/hr/sq.ft.)

LargerVapor Pressure

(in.hg)

SmallerVapor Pressure

(in.hg)

PermeationLoad

(gr/hr)

_________ x __________ x ( ___________ - ___________ ) = _____________ gr/hr_________ x __________ x ( ___________ - ___________ ) = _____________ gr/hr_________ x __________ x ( ___________ - ___________ ) = _____________ gr/hr_________ x __________ x ( ___________ - ___________ ) = _____________ gr/hr_________ x __________ x ( ___________ - ___________ ) = _____________ gr/hr

Total ___________________ gr/hr

400 0.025 0.520 0.15 4

400 0.025 0.520 0.15 4

600 0.025 0.980 0.15 13

600 0.025 0.520 0.15 6

2400 0.45 0.680 0.15 572

2400 0.45 0.520 0.15 400

999


Products & PackagingProducts & Packaging

Total ___________________ gr/hr

OriginalMoistureContent( lb/lb )

FinalMoistureContent( lb/lb )

_________ x ( ___________ - ___________ ) x 7000 = _____________ gr/hr

ItemEntry Rate

(lb/hr)Grains

Per Pound

MoistureLoad

(gr/hr)

Item 1

_________ x ( ___________ - ___________ ) x 7000 = _____________ gr/hrItem 2

_________ x ( ___________ - ___________ ) x 7000 = _____________ gr/hrItem 3

_________ x ( ___________ - ___________ ) x 7000 = _____________ gr/hrItem 4

15 0.13 0.06 7350

7350


PersonnelPersonnel

Moderate work

_________ x ___________ = _____________ gr/hr

NumberOf People

MoistureLoad

( gr/hr/person)

MoistureLoad

(gr/hr)

Seated_________ x ___________ = _____________ gr/hrStanding_________ x ___________ = _____________ gr/hrLight work

_________ x ___________ = _____________ gr/hrRoom visitors5 5500 27,5003 5500 16,500

44,000

_________ x ___________ = _____________ gr/hr

Total ___________________ gr/hr


Door & Airlock OpeningsDoor & Airlock Openings

_________ x __________ x _________ x _________ x ( ___________ - ___________ ) = _____________ gr/hr

AirflowVelocity

(fpm)

OpenArea

(sq.ft.)

AirDensity

(lb/cu.ft.)

TimeOpen

(min/hr)

Air MoistureOutside(gr/lb)

Moisture Load(gr/hr)

Air MoistureInside(gr/lb)

_________ x __________ x _________ x _________ x ( ___________ - ___________ ) = _____________ gr/hr

50 13.75 0.074 8 77 22 22,385

( _____ x _____ x _____ ) x _________ x ___________ x

Airlock Dimensions (ft)Height

AirDensity

(lb/cu.ft.)

OpeningFrequency

(openings/hr)

Air MoistureOutside(gr/lb)

Air MoistureInside(gr/lb)Length Width

( ___________ - ___________ ) = _____________ gr/hr

2_____________________________ ][8 8 8 0.074 4 146 22 9,396

Total ___________________ gr/hr31,781

• Door Openings

• Air Lock Openings


Conveyor OpeningConveyor Opening

Total ___________________ gr/hr

_________ x __________ x ( ___________ - ___________ ) x _________ x 60 = _____________ g

OpenArea

(sq.ft.)

Air EntryVelocity(fpm)

MoistureOutside(gr/lb)

MoistureInside(gr/lb)

Air Density(lb/cu.ft.)

Conveyor Openings


MinutesPer Hour

_________ x __________ x ( ___________ - ___________ ) x _________ x 60 = _____________ gOpen Doorways and Holes

• Wall Openings - No Load

Assume that the productconveyor opening will beequipped with a 2'-tunneland plastic strips.

Those details, combinedwith 150 fpm exit velocitywill eliminate infiltrationthrough the opening


Moisture In Fresh AirMoisture In Fresh Air(The Largest Load)(The Largest Load)


Net Fresh Airfor Personnel,

Exhaust Air MakeupAnd Room Pressurization

Fresh AirFlow Rate

(cfm)


MoistureControl Level

(gr/lb)Air Density(lb/cu.ft.)

MinutesPer Hour

_________ x ( ___________ - ___________ ) x _________ x 60 = ________________600 146 22 0.074 330,336


NoNo--Load ElementsLoad Elements

DH Handbook 5—26—5/6

• Open Gas Flame - No Load

• Wet Surfaces - No Load

• Exterior Walls - No Load

• Cracks - No Load

No open gas flamein the room

No wet surfacesin the room

Exterior wall isequipped withmetal foilvapor retarder

Room will besupplied withexcess air tominimize leakage

_________ x ___________ = _____________ g

Gas BurningRate

(cu.ft./hr)

WaterVapor Generation

(gr/cu.ft.)

MoistureLoad

(gr/hr)

Typical Value650 gr/cu.ft.

x 7000 = _____________ gr/hr

WettedSurface Area

(sq.ft.)

Latent HeatTransfer Rate

(Btu/sq.ft./in.hg.)

AirVapor Pressure

(in.hg.)

Water SurfaceVapor Pressure

(in.hg.)Grains Per

Pound

Latent Heat Of VaporizationAt The Water Temperature

(Btu/lb)

_________ x ____________ x ( ___________ - ___________ )

___________________][

MoistureLoad

(gr/hr)

_________ x __________ x ( ___________ - ___________ ) x _________ = ___________

SurfaceArea

(sq.ft.)

AirInfiltration Rate(cu.ft./hr/sq.ft.)




Wall 1Wall 2

Total ___________________ gr/h


_________ x __________ x ( ___________ - ___________ ) x _________ = ___________

_________ x __________ x ( ___________ - ___________ ) x _________ = ___________

CrackLength

(ft)

AirInfiltration Rate

(cu.ft./hr/ft.)




Door FramesWindows

Total ___________________ gr/h


_________ x __________ x ( ___________ - ___________ ) x _________ = ___________Ductwork _________ x __________ x ( ___________ - ___________ ) x _________ = ___________


The Load Summary The Load Summary –– Ventilation air (as in Ventilation air (as in pressurization air) often represents the biggest loadpressurization air) often represents the biggest load

____________________________________________________________________________________________________________

____________

____________

PermeationProducts

PersonnelGas Flame

Wet SurfacesExterior Walls

CracksDoor OpeningsWall OpeningsTotal Internal

Moisture Load

Fresh Air

9997350

0000

31,7810

84,130

330,336

44,000

Moisture in the ventilationair is almost three timeslarger than the rest of theloads combined


Dehumidifier PerformanceDehumidifier Performance

How dry is the air after it leaves the How dry is the air after it leaves the dehumidifier? ..... That will depend on:dehumidifier? ..... That will depend on:

Moisture content of the entering process airMoisture content of the entering process airTemperature of the entering process airTemperature of the entering process airVelocity of the process air through the desiccantVelocity of the process air through the desiccantTemperature of the entering reactivation airTemperature of the entering reactivation airAnd to a lesser extent:And to a lesser extent:

Moisture content of the reactivation airMoisture content of the reactivation airVelocity of the reactivation air through the desiccantVelocity of the reactivation air through the desiccantAmount of desiccant exposed to the airAmount of desiccant exposed to the air

Wheel rotational speed (Wheel rotational speed (egeg))SorptionSorption--desorption characteristics of the desiccantdesorption characteristics of the desiccant


Desiccant Wheel LifeDesiccant Wheel Life

Normal life: 3 Normal life: 3 -- 7 years (but 10 7 years (but 10 -- 15 15 years is not uncommon)years is not uncommon)Potential failure modes:Potential failure modes:

Desiccant attrition or deliquescenceDesiccant attrition or deliquescenceDesiccant deteriorationDesiccant deteriorationWheel face cloggingWheel face cloggingWheel face gougingWheel face gouging

To extend wheel life:To extend wheel life:Change or clean filters regularlyChange or clean filters regularlyCheck reactivation heaters & airflowCheck reactivation heaters & airflowCheck seal wearCheck seal wearCheck wheel drive belt & motorCheck wheel drive belt & motorCheck process air flowCheck process air flow


DeliquescenceDeliquescence

Definition:Definition: the process in which a soluble the process in which a soluble substance picks up water vapor from the substance picks up water vapor from the air to form a solution. In order for air to form a solution. In order for deliquescence to occur, the vapor deliquescence to occur, the vapor pressure of the water in the air must be pressure of the water in the air must be greater than the vapor pressure of the greater than the vapor pressure of the saturated solution. saturated solution.


Key Variables with HardwareKey Variables with Hardware

0 10 20 30 40 50 60

2

4

810

12

14

16

18

MoistureLeavingProcess

Process Air Moisture

6

ProcessAir Temperature

ReactivationAir Temperature

Process AirVelocity(Unit Size)

ReactivationHeater

Process AirLeaving

Process AirEntering

Reactivation


Utility SystemsUtility Systems

Clean UtilitiesClean UtilitiesCritical UtilitiesCritical UtilitiesGeneral UtilitiesGeneral UtilitiesSpecial UtilitiesSpecial Utilities


General UtilitiesGeneral Utilities

Plant SteamPlant SteamPlant Chilled Water &/or GlycolPlant Chilled Water &/or GlycolCompressed GassesCompressed GassesHVACHVACWaste Water TreatmentWaste Water TreatmentElectricElectricPlant Water & DrainsPlant Water & Drains


Clean UtilitiesClean Utilities

Water SystemsWater SystemsDeionizedDeionizedPurifiedPurifiedWFIWFI

Clean/Pure SteamClean/Pure SteamCleanClean--inin--place (CIP, SIP, WIP)place (CIP, SIP, WIP)HVACHVACPure GassesPure Gasses


CleanClean--inin--PlacePlace


CleanClean--inin--PlacePlace


Special UtilitiesSpecial Utilities

BiowasteBiowaste TreatmentTreatmentBioinactivationBioinactivation


Critical UtilitiesCritical Utilities

Can be some or all of clean utilities and Can be some or all of clean utilities and may also include other key utilitiesmay also include other key utilities


IsolatorsIsolators


IsolatorsIsolators


IsolatorsIsolators

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