PhEn 602 Spring 2009 1
PhEnPhEn--602602Pharmaceutical Facility DesignPharmaceutical Facility Design
J. ManfrediJ. ManfrediNotes #10Notes #10
PhEn 602 Spring 2009 2
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?
PhEn 602 Spring 2009 3
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
PhEn 602 Spring 2009 4
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
PhEn 602 Spring 2009 5
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)
PhEn 602 Spring 2009 6
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
PhEn 602 Spring 2009 7
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.
PhEn 602 Spring 2009 8
Desiccant DehumidificationDesiccant Dehumidification
LatentHeat
Conversion
Process airDehumidification
PhEn 602 Spring 2009 9
Desiccant DehumidificationDesiccant Dehumidification
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
PhEn 602 Spring 2009 10
Desiccant DehumidificationDesiccant Dehumidification
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
PhEn 602 Spring 2009 11
Desiccant DehumidificationDesiccant Dehumidification
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
PhEn 602 Spring 2009 12
Desiccant Dehumidification – the processDesiccant SorptionDesiccant Sorption
PhEn 602 Spring 2009 13
Desiccant Dehumidification – the processDesiccant ReactivationDesiccant Reactivation
PhEn 602 Spring 2009 14
Desiccant Dehumidification – the processDesiccant CoolingDesiccant Cooling
PhEn 602 Spring 2009 15
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
PhEn 602 Spring 2009 16
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
PhEn 602 Spring 2009 17
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
Mosture Content of the Desiccant
PhEn 602 Spring 2009 18
HoneyCombeHoneyCombe®® Dehumidifier ComponentsDehumidifier Components
ReactivationHeater
F
F
ReactivationFilter
ProcessDamper
ProcessFan
ReactivationFan
ReactivationDamper
ProcessFilter
DesiccantWheel
DesiccantDrive System
DesiccantAir Seals
ElectricalController
PhEn 602 Spring 2009 19
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
Mosture Content of the Desiccant
PhEn 602 Spring 2009 20
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
PhEn 602 Spring 2009 21
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
Mosture Content of the Desiccant
PhEn 602 Spring 2009 22
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
Mosture Content of the Desiccant
PhEn 602 Spring 2009 23
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
PhEn 602 Spring 2009 24
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
PhEn 602 Spring 2009 25
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®
PhEn 602 Spring 2009 26
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)
PhEn 602 Spring 2009 27
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
PhEn 602 Spring 2009 28
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
PhEn 602 Spring 2009 29
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
PhEn 602 Spring 2009 30
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
PhEn 602 Spring 2009 31
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
PhEn 602 Spring 2009 32
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
PhEn 602 Spring 2009 33
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
PhEn 602 Spring 2009 34
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
PhEn 602 Spring 2009 35
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
PhEn 602 Spring 2009 36
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
PhEn 602 Spring 2009 37
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
PhEn 602 Spring 2009 38
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
PhEn 602 Spring 2009 39
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
PhEn 602 Spring 2009 40
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
PhEn 602 Spring 2009 41
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)
PhEn 602 Spring 2009 42
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
PhEn 602 Spring 2009 43
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
PhEn 602 Spring 2009 44
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
PhEn 602 Spring 2009 45
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
PhEn 602 Spring 2009 46
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
PhEn 602 Spring 2009 47
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)
PhEn 602 Spring 2009 48
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
PhEn 602 Spring 2009 49
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
PhEn 602 Spring 2009 50
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
PhEn 602 Spring 2009 51
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
PhEn 602 Spring 2009 52
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 ( )
PhEn 602 Spring 2009 53
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
PhEn 602 Spring 2009 54
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
PhEn 602 Spring 2009 55
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
PhEn 602 Spring 2009 56
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
PhEn 602 Spring 2009 57
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
PhEn 602 Spring 2009 58
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
PhEn 602 Spring 2009 59
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
PhEn 602 Spring 2009 60
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
PhEn 602 Spring 2009 61
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
PhEn 602 Spring 2009 62
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
Moisture Load(gr/hr)
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
PhEn 602 Spring 2009 63
Moisture In Fresh AirMoisture In Fresh Air(The Largest Load)(The Largest Load)
Moisture Load(gr/hr)
Net Fresh Airfor Personnel,
Exhaust Air MakeupAnd Room Pressurization
Fresh AirFlow Rate
(cfm)
MoistureOutside(gr/lb)
MoistureControl Level
(gr/lb)Air Density(lb/cu.ft.)
MinutesPer Hour
_________ x ( ___________ - ___________ ) x _________ x 60 = ________________600 146 22 0.074 330,336
PhEn 602 Spring 2009 64
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.)
MoistureOutside(gr/lb)
MoistureInside(gr/lb)
Air Density(lb/cu.ft.)
Wall 1Wall 2
Total ___________________ gr/h
Moisture Load(gr/hr)
_________ x __________ x ( ___________ - ___________ ) x _________ = ___________
_________ x __________ x ( ___________ - ___________ ) x _________ = ___________
CrackLength
(ft)
AirInfiltration Rate
(cu.ft./hr/ft.)
MoistureOutside(gr/lb)
MoistureInside(gr/lb)
Air Density(lb/cu.ft.)
Door FramesWindows
Total ___________________ gr/h
Moisture Load(gr/hr)
_________ x __________ x ( ___________ - ___________ ) x _________ = ___________Ductwork _________ x __________ x ( ___________ - ___________ ) x _________ = ___________
PhEn 602 Spring 2009 65
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
PhEn 602 Spring 2009 66
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
PhEn 602 Spring 2009 67
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
PhEn 602 Spring 2009 68
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.
PhEn 602 Spring 2009 69
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
PhEn 602 Spring 2009 70
Utility SystemsUtility Systems
Clean UtilitiesClean UtilitiesCritical UtilitiesCritical UtilitiesGeneral UtilitiesGeneral UtilitiesSpecial UtilitiesSpecial Utilities
PhEn 602 Spring 2009 71
General UtilitiesGeneral Utilities
Plant SteamPlant SteamPlant Chilled Water &/or GlycolPlant Chilled Water &/or GlycolCompressed GassesCompressed GassesHVACHVACWaste Water TreatmentWaste Water TreatmentElectricElectricPlant Water & DrainsPlant Water & Drains
PhEn 602 Spring 2009 72
Clean UtilitiesClean Utilities
Water SystemsWater SystemsDeionizedDeionizedPurifiedPurifiedWFIWFI
Clean/Pure SteamClean/Pure SteamCleanClean--inin--place (CIP, SIP, WIP)place (CIP, SIP, WIP)HVACHVACPure GassesPure Gasses
PhEn 602 Spring 2009 73
CleanClean--inin--PlacePlace
PhEn 602 Spring 2009 74
CleanClean--inin--PlacePlace
PhEn 602 Spring 2009 75
Special UtilitiesSpecial Utilities
BiowasteBiowaste TreatmentTreatmentBioinactivationBioinactivation
PhEn 602 Spring 2009 76
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
PhEn 602 Spring 2009 77
IsolatorsIsolators
PhEn 602 Spring 2009 78
IsolatorsIsolators
PhEn 602 Spring 2009 79
IsolatorsIsolators
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