AIR HUMIDIFICATION

Technical, health and energy aspects

Luigi NaliniLisbon, October 20th, 2016

IN CASE OF INTEREST, THE SLIDES SHOWN TODAY MAY BE REQUESTED AT THE FOLLOWING 

E‐MAIL ADDRESS:

media.relations@carel.com

LIFE ON EARTH DEPENDS ON WATER

ALL KNOWN LIFE FORMS DEPEND ON THE PRESENCE OF WATER THAT MAKES POSSIBLETHE METABOLIC PROCESSES.

MANY OTHER SUBSTANCES AND PRODUCTS, BOTH ORGANIC AND INORGANIC,CONTAIN WATER THAT AFFECTS HEAVILY THEIR PHYSICAL, CHEMICAL ANDDIMENSIONAL PROPERTIES.

THE CONTENT OF WATER IN BODIES OR MATERIALS IS THE RESULT OF A BALANCEBETWEEN INTAKE AND LOSS AMONG THE BODIES THEMSELVES AND WHATSURROUNDS THEM, INCLUDING THE ATMOSPHERE.

ON A PLANETARY SCALE THIS BALANCE IS MAINLY DETERMINED BY THEHYDROLOGICAL CYCLE THAT CAUSES THE CONTINUOUS CHANGE OF STATE ANDMOVEMENT OF WATER ON THE SURFACE OF THE EARTH AND ABOVE IT.

THE HYDROLOGICAL CYCLE

THE PROVISION OF WATER NECESSARY FOR THE EXISTENCE OF LIFE AND THECONSERVATION OF SUBSTANCES OR BODIES ON EARTH HAPPENS THANKS TO THEATMOSPHERE THAT ABSORBS THE VAPOR ORIGINATED FROM THE LIQUID MASSES ANDPROMOTES THE GENERATION OF CLOUDS WHICH THEN FALL UNDER LIQUID OR SOLIDFORM TO THE GROUND.

THE DISTRIBUTION OF RAINWATER THROUGH THE RIVERS AND THE SOIL INFILTRATION, ISTHE MAIN SOURCE OF HYDRATATION OF THE PLANT KINGDOM AND THUS OF ALL LIVINGSPECIES, HOWEVER A SUBSTANTIAL PART OF WATER STANDS IN THE ATMOSPHERE IN THEFORM OF VAPOR, SPREADING ITS MOLECULES THROUGH THE AIR.

THE CONTENT OF WATER VAPOR MOLECULES IN THE AIR IS DEFINED HUMIDITY.ANY AIR CONTAININGWATER VAPOR MOLECULES IS CALLED HUMID AIR.

THE CIRCULATION AND THE DISTRIBUTION OF WATER WITHIN THE HYDROLOGICAL CYCLE ARE MADE POSSIBLE BY THE TWO MAJOR TRANSFORMATIONS: EVAPORATION (PASSAGE FROM LIQUID STATE TO VAPOR STATE); CONDENSATION (FROM VAPOR STATE TO LIQUID STATE).

THE PASSAGE FROM ICE/SNOW INTO WATER AND VICE VERSA PLAYS AN IMPORTANTROLE BUT NOT IMMEDIATELY TIED WITH THE HYDRATATION OF THE EARTH

ACCORDING TO THE MOLECULAR KINETIC THEORY, AS ANY ELEMENT WATER ASSUMESTHE SOLID, LIQUID, GASEOUS STATE IN FUNCTION OF THE INTERNAL ENERGY OF ITSMOLECULES , WHICH OCCURS AS VIBRATIONAL, ROTATIONAL, TRANSLATIONAL MOTIONAND RECIPROCAL COLLISIONS.

TEMPERATURE IS A MEASURE OF THE AVERAGE INTERNAL ENERGY AND THEREFORETHE HIGHER THE TEMPERATURE, THE GREATER THE INTERNAL ENERGY OF THE WATERMOLECULES.IN LIQUID WATER THE INTERNAL ENERGY OFMOLECULES IS NOT HIGH ENOUGH TO BREAK THERECIPROCAL ATTRACTION: UNLIKE SOLID ICE, INWHICH MOLECULES MOVE AROUND THEIR FIXEDPOSITION, LIQUID WATER HAS A DEFINED VOLUMEBUT NO CONSISTENCY AND THUS, DUE TO GRAVITYOR CAPILLARITY, TAKES THE SHAPE OF ITSCONTAINER.

THE THREE PHYSICAL STATES OF WATER

UPON A SUFFICIENT ENERGY INPUT – UNDER HEAT FORM – THE MOLECULES OFLIQUID WATER INCREASE THEIR AVERAGE INTERNAL ENERGY; PART OF THEM REACHAN ENERGY LEVEL SUFFICIENT TO ENTER IN THE EVAPORATION PROCESS,OVERCOMING THE ATTRACTIVE FORCES OF THE BULK OF THE LIQUID, PASSING TOTHE GASEOUS STATE AND SPREADING IN THE AVAILABLE SPACE AROUND.

ON THE CONTRARY, IF THE MOLECULES OFWATER CONTAINED IN THE AIR TRANFER SOMEHEAT (FOR EXAMPLE COMING IN CONTACT WITHA COLD SURFACE), THEIR INTERNAL ENERGY MAYBECOME INSUFFICIENT TO ENABLE THEM TOREMAIN AT THE GASEOUS STATE: IN THIS CASETAKES PLACE THE CONDENSATION PROCESS INWHICH THE VAPOR TURNS INTO LIQUID.

EVAPORATION AND CONDENSATION OF WATER

THE AVERAGE KINETIC ENERGY OF VAPOR MOLECULESDETERMINES DIRECTLY THE MACROSCOPIC PRESSURE THEYEXERT OVER THE ADJACENT BODIES, IN PROPORTION TO THENUMBER AND THE FORCE OF THE COLLISIONS.AS WELL AS THE INTERNAL ENERGY, ALSO VAPOR PRESSUREDEPENDS JUST ON TEMPERATURE.

ENTERING INTO THE ATMOSPHERE THE VAPOR MOLECULES MUST «COMPETE» WITHTHE PRESSURE EXERTED BY THE OTHER GASES: INFACT, ACCORDING TO THE GAS LAWS,THE INDIVIDUAL PRESSURE OF ANY GAS (CALLED ALSO PARTIAL PRESSURE) IN THEMIXTURE IS PROPORTIONAL TO ITS VOLUMETRIC FRACTION.

THE DIAGRAM SHOWS THE PRESSUREEXERTED BY THE VAPOR MOLECULES vsTEMPERATURE JUST AT THE SURFACE OFLIQUID WATER (i.e.: 3170 Pa @ 25°C).THE SURFACE VAPOR PRESSURE, SINCE INEQUILIBRIUM BETWEEN LIQUID AND VAPOR,IS THE MAXIMUM POSSIBLE AT THATTEMPERATURE AND THEREFORE IS DEFINEDSATURATION PRESSURE PVS. 0 5 10 15 20 25 30 35 40 45 50

14000

12000

10000

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6000

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0

temperature ‐ °CVapo

rpressure ‐P

a

SATURATION PRESSURE VPS OF WATER vs TEMPERATURE

3170

WATER VAPOR PRESSURE

THE NUMBER OF MOLECULES OF WATERCONTAINED IN THE AIR IS PROPORTIONAL TOTHE PARTIAL PRESSURE THEY EXERT.THE MAXIMUM QUANTITY IS GOT WHEN THEVAPOR PARTIAL PRESSURE EQUALS THESATURATION PRESSURE VPS; IN THIS CASE,THE AIR IS SAID SATURATEDWITH VAPOR.

kPa20,5 76,6 0,97 3,17 0,07 101,322,6% 74% 1,33% 1,97% 0,11% 100%weightPROPORTION OF ATMOSPHERE MAIN COMPONENTS WITH WATER VAPOR AT SATURATION WHEN TEMPERATURE = 25°C

BUT, DIFFERENTLY FROM PERMANENT GASES(N2, O2, AR) WHOSE PERCENTAGE IS STABLE,WATER VAPOR CONCENTRATION VARIESWITH GEOGRAFIC LOCATION, TEMPERATUREAND WEATHER: IF THE CONTENT OF VAPORIN THE AIR IS NOT ENOUGH FOR SATURATION,THE VAPOR PRESSURE PV IS ALSO LOWERTHAN THE SATURATED PRESSURE PVS.

THE RATIO BETWEEN THE ACTUAL PRESSUREAND THE SATURATED PRESSURE IS DEFINEDRELATIVE HUMIDITY RH:

RH = PV / PVS          [%]

VAPOR PRESSURE OF WATER vs TEMPERATURE AND RH

0

1000

2000

3000

4000

5000

6000

0 5 10 15 20 25 30 35 40

temperature ‐ °C

Vapo

rpressure ‐P

a

25

PVS = 3170

PV = 1270

VAPOR PRESSURE DEFICIT

ATMOSPHERIC PRESSURE (101,325 Pa)

ATMOSPHERIC RELATIVE HUMIDITY

SOME “MISTERIOUS” STAINS OF MOLD INTHE CORNERS OF A HOUSE ARE GENERALLYCAUSED DURING COLD SEASONS JUST BYTHE MIGRATION OF VAPOR FROM THEKITCHEN OR FROM THE BATHROOM WHEREIT IS GENERATED TO THE COLDER SPOTSWHERE IT CONDENSES.

THE ATMOSPHERIC AIR IS A FUNDAMENTALVEHICLE FOR THE TRANSPORTATION OF

ACCORDING TO DALTON’S LAW EVERY GAS IN A MIXTURE BEHAVES INDEPENDENTLYOF THE OTHER ONES AS IT WAS ALONE AT ITS OWN PARTIAL PRESSURE.FOR THIS REASON IF TWO CONTIGUOUS AREAS HAVE AN UNEQUAL MOISTURECONTENT, DUE TO THE PARTIAL PRESSURE DIFFERENCE THE VAPOR WILL PASS FROMTHE SPACE WITH THE HIGHER MOISTURE CONTENT TO THE OTHER.

WATER VAPOR MIGRATES THROUGH THE ATMOSPHERE

MOISTURE AND FOR THE WATER BALANCE OF LIVING BEINGS AND BODIES ORMATERIALS – ORGANIC AND INORGANIC – WHOSE PROPERTIES ARE INFLUENCED BYTHEIR WATER CONTENT NOT ONLY WITHIN CLOSED ENVIRONMENTS BUT ALSO IN INVAST OUTDOOR SPACES AS IN DESERTIC AREAS WHERE RAINS ARE VERY RARE

THE TRANSFER OF MOISTUREWILL CONTINUE UNTIL THETWO PRESSURES WILLEQUALIZE; DUE TO THE HUGEDISPARITY IN MASS, THE FINALVAPOR PRESSURE IN THE ROOMWILL BECOME VERY SIMILAR TOTHE EXTERNAL ONE, UNLESSTHERE IS AN INDOOR PROCESSOF HUMIDITY CONTROL.0 5 10 15 20 25 30 35 40

25

20

15

10

5

0

DRY BULB TEMPERATURE ‐ °C

ABS. HUMIDITY ‐g

V/kg

A

VAPO

R PA

RTIAL PR

ESSU

RE ‐KP

A

1

2

3

0

0,49

2,5

1,5

3,5

2,5315,9

3,0

24

Win

Wout

Sin Sout

22

VAPOR MIGRATES FROM INDOOR TO OUTDOOR AND VICEVERSAIF THERE IS A DIFFERENCE IN PARTIAL PRESSURES, THE MIGRATION OF VAPOR TAKESPLACE ALSO FROM AN ENCLOSED SPACE TO THE OUTDOOR AIR OR VICEVERSATHROUGH CRACKS – OFTEN UNNOTICED – ON BUILDING WALLS, DOORS, WINDOWS.

HOWEVER IF THE TEMPERATURE OF THE TWO AMBIENTS ARE DIFFERENT, ALSORELATIVE HUMIDITIES WILL BE AFFECTED.

AS SHOWN IN THE ABOVE DIAGRAM, THE INDOOR RELATIVE HUMIDITY WILLNORMALLY BE DRIVEN TO HIGH VALUES IN SUMMER AND TO LOW ONES IN WINTER:BEYOND ACCEPTABLE LIMITS A CLIMATIC CONTROL SYSTEM BECOMES NECESSARY

STRATUM CORNEUM

STRATUM GRANULOSUM

STRATUM SPINOSUM

WATER

WATER

TRASPIRATION OF ANIMAL EPIDERMIS TRANSPIRATION OF WOODTRASPIRATION OF VEGETAL CELLS

THE WATER CONTAINED IN ANY BODY OR MATERIAL HAS A SURFACE VAPOR PRESSUREEQUAL TO THE SATURATION VALUE PVS AT ITS TEMPERATURE.

IF THE SURROUNDING AIR HAS A LOWER VAPOR PRESSURE, AN EVAPORATION OFWATER FROM THE BODY OR MATERIAL INTO THE AIR WILL START.

ON THE OPPOSITE, THE PRESSURE DIFFERENCE WILL CAUSE THE TRANSFER OF VAPORFROM THE AIR INTO THE BODIES OR MATERIALS THAT ABSORB IT.

THE BELOW DRAWINGS SHOW THE «TRANSPIRATION» OF SOME ORGANIC MATTERS

VAPOR MIGRATES FROM BODIES TO AIR AND VICEVERSA

DRY BULB TEMPERATURE ‐ °C

VAPO

R PA

RTIAL PR

ESSU

RE ‐KP

A

1

2

3

2,5

1,5

3,5

20 25 30 35 40

25

20

15

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5

ABS. HUMIDITY ‐g

V/kg

A

CAUTION: HEAT CRAMPS AND HEAT EXHAUSTION POSSIBILE 

DANGER: HEAT CRAMPS AND HEAT EXHAUSTION LIKELYPROBABLE HEAT STROKE

DUE TO METABOLISM, HUMAN BODY GENERATES HEATTHAT, IN ORDER TO KEEP THE INTERNAL TEMPERATUREAT 36‐37°C, MUST BE NECESSARILY RELEASED: OURPERCEPTION OF "HOT" OR "COLD" IS CAUSED BY THECAPABILITY TO TRANSFER THE METABOLIC HEAT RATEMORE THAN BY ENVIRONMENTAL CONDITIONS.AS AMBIENT TEMPERATURE RAISES, THE HEATTRANSFERRED BY CONVECTION OR RADIATIONDECREASES AND OUR BODY SPONTANEOUSLY SWEATS

HUMAN BODY PERCEIVES INDIRECTLY HIGH RELATIVE HUMIDITY

UPON AN INCREASE OF HUMIDITY,SWEATING GROWS CREATING ASENSE OF UNEASE WITH NO BENEFIT.

BEYOND CERTAIN TEMPERATURE/HUMIDITY LIMITSTHE METABOLIC HEAT CANNOT BE RELEASED,CAUSING A SEVERE RISK OF A "HEAT STROKE" ANDEVEN PUTTING AT RISK THE SURVIVAL.

SO TO IMPROVE THE HEAT DISSIPATION THROUGHEVAPORATION.

BEING NOT EQUIPPED WITH SENSORY RECEPTORS SUITABLE TO FEEL DIRECTLY THEMOISTURE CONTENT OF THE AIR ‐ WHICH, IN ADDITION, IS FULLY TRANSPARENT ‐HUMAN BODY IS LESS SENSITIVE TO LOW RELATIVE HUMIDITY.

LOW HUMIDITY IS MOSTLY PERCEIVED ONLY FOR ITS SIDE EFFECTS THAT, ALTHOUGHPOSSIBLY UNNOTICED IN THE SHORT TERM, COULD BE OBSERVED AFTER A CERTAINPERIOD OF TIME; HOWEVER THE CONSEQUENCES CAN BE UNPLEASANT AND OFTENHARMFUL ECONOMICALLY, TECHNICALLY AND PATHOLOGICALLY.

LET US FOCUS ON THE EFFECTS OF LOW ENVIRONMENTAL RELATIVE HUMIDITY, ON THE RECOMMENDED MINIMUM LIMITS IN THE VARIOUS AMBIENTS AND CIRCUMSTANCES AND ON THE DEVICES USED TO FACE IT.  

LIMITED SENSIBILITY OF HUMAN BODY TO LOW RELATIVE HUMIDITY

normal nasalmucosa

irritated nasalmucosa

OVER TIME, EXPOSURE TO LOW HUMIDITY CAN DRY OUTTHE MUCUS MEMBRANES LOCATED IN THE NOSE ANDTHROUGH THE RESPIRATORY TRACT, WHICH ARE ANATURAL BARRIER TO INFECTION: BECOMING DRY, THEYLOSE THEIR ELASTICITY AND CRACK GIVING A DIRECT PATHFOR GERMS AND BACTERIA TO ENTER THE BLOODSTREAM.

MOREOVER, DRY AIR DRAWS MOISTURE OUTOF THE SKIN CAUSING SMALL CRACKS ON ITSSURFACE AND PROVIDING AN ENTRYWAY FORPOTENTIAL DANGEROUS PATHOGENS.

(GUGGENBICHLER ET AL., 2007) CARRIED OUTEXPERIMENTAL AND CLINICAL STUDIES ANDCONCLUDED THAT FOR A GOOD MECHANICALCLEARANCE OF THE AIRWAYS A HUMIDITY OFAT LEAST 30% ( BETTER 45%) IS REQUIRED.

EFFECT OF LOW HUMIDITY IN HEALTH AND WELLNESS

germs

Rough, cracked, pertiallyinflamed skindue to damagedbarrier

corneal layerlipids (fats)

spinouslayer

basal layer

ONE OF THE FIRST COMPLAINTS STATED BY PERSONS EXPOSED TO PROLONGED DRY AIRIS THE IRRITATION OF THE EYES ARISING IN CASE OF A BREAKDOWN OF THE TEAR FILM.LOW HUMIDITY IS ONE OF THE REASONS PEOPLE MAY BECOME SICK.

THIS IS IMPORTANT PARTICULARLY FOR ESPECIALLY EXPOSED PERSONS SUCH ASPEOPLE IN HOSPITALS AND NURSING HOMES.

EFFECT OF LOW HUMIDITY ON WOOD AND PAPERMANY SUBSTANCES AND PRODUCTS CONTAIN WATER THATAFFECTS THEIR PHYSICAL AND DIMENSIONAL PROPERTIES.

THE LENGTH OF WOOD TANGENTIAL FIBRES INCREASES APPROX0,04% PER %RH THUS, IF RH VARIES FROM 40% TO 50%, AWOODEN BOARD OF 500 mm LENGHTENS OF 2 mm.A RAPID CHANGE OF THE WATER CONTENT – AS OCCURS WHEN

water con

tent ‐% weight

10% 30% 50% 70% 90%0

5

10

15

20

25

air relative humidity @ 20°C

WOOD

PAPER

THE AIR HUMIDITY IS FAR FROM THE BALANCE WITH THE WOOD ‐ IMPLIES DIMENSIONALVARIATIONS WHICH CAN LEAD TO THE BOWING OF THE BOARDS UP TO GET A CRACKING.

THE CONTAINMENT OF THE AMBIENT RELATIVE HUMIDITY BETWEEN 35% AND 55% ISRECOMMENDED FOR ITS LOWER INFLUENCE ONWATER CONTENT IN THESE MATERIALS.

REGARDING PAPER, A CHANGE OF RELATIVE HUMIDITY OF 10%IMPLIES A DIMENSIONAL VARIATION BETWEEN 0.1% AND 0.2%: ONA A4 SHEET IT MEANS NOT LESS THAN ½ mm.IN ADDITION, IN A STACK OF PAPER OR IN A BOOK THE VARIATIONIN LENGTH TAKES PLACE INITIALLY IN THE PERIMETER PART, ANDONLY AFTER A LONGER TIME IN THE CORE, GIVING RISE TOFOLDING AND CORRUGATION OF THE SHEETS: THUS, BESIDES THEABSOLUTE VALUE, THE RELATIVE HUMIDITY STABILITY IS VERYIMPORTANT.

Pressroom = 75% RHPaper stack = 50% RH

Pressroom = 35% RHPaper stack = 50% RH

TIGHT EDGES

WAVY EDGES

GENERALLY A HUMIDITY LEVEL BETWEEN 40% AND 60% IS MOSTLY SUITABLE FORHUMAN COMFORT AND TECHNICAL PROCESSES (WITH SEVERAL EXCEPTIONS AS INTHE CONSERVATION OF MANY FOODS AND SUBSTANCES REQUIRING HIGHER VALUES).

HOWEVER AIR HUMIDIFICATION IS AN ENERGY CONSUMING PRACTICE BECAUSE THEEVAPORATION OF 1 kg OF WATER REQUIRES AN INPUT OF APPROX 0,72 kWh (THESAME REQUIRED TO RIDE BY BIKE 25 km IN ONE HOUR).

IN ANY APPLICATION THE MINIMUM RELATIVE HUMIDITY THRESHOLD SHOULD BE ACOMPROMISE BETWEEN THE ACTUAL NEEDS – PREVENTING MOISTURE DROPPINGBELOW POTENTIALLY HARMFUL LEVELS ‐ AND THE RELEVANT COST INCURRED.

THE MOST INFLUENTIAL CONSEQUENCES OF A LOW RELATIVE HUMIDITY ON OUR LIVESAND COMMON ACTIVITIES ARE:

1) THE ABSORPTION BY THE AIR OF THE WATER CONTAINED IN LIVING BEINGS ANDIN MATERIALS, PARTICULARLY THE ORGANIC ONES;

2) THE BUILD‐UP OF STATIC ELECTRICITY WITH A RESULTING "SHOCK" FOR INVOLVEDPEOPLE OR DAMAGES IN OBJECTS AND PRODUCTS.

MINIMUM RELATIVE HUMIDITY THRESHOLD IS A COMPROMISE

THE SENSITIVITY OF MATERIALS TO ENVIRONMENTAL HUMIDITY IS ONE OF THE MAINCAUSE OF DETERIORATION OF ARTWORKS MADE WITH HYGROSCOPIC MATERIALS.

DIMENSIONAL ALTERATIONS MAY GENERATE CRACKS IN WOODEN SCULPTURES AND INANTIQUE FURNITURE OR IN MANUSCRIPTS WITH LOSS OF ELASTICITY AND BRITTLENESS.

MATERIALS LIKE OIL, GESSOES, TEMPERA PAINTS HAVE A LOWER RESPONSE TO AIRRELATIVE HUMIDITY BRINGING TO CRAQUELURES IN PAINTINGS ON WOOD OR ONFRAMED CANVAS IN THE CASE OF WIDE CHANGES IN AMBIENT CONDITIONS.

ACCORDING TO THE GUIDELINES OF THE SMITHSONIAN MUSEUM CONSERVATIONINSTITUTE THE RELATIVE HUMIDITY FOR EXHIBITION AND STORAGE SPACES SHOULD BEINCLUDED BETWEEN 45% AND 55%, IN ANY CASE NOT LOWER THAN 37%.EVEN MORE IMPORTANT IS THAT HUMIDITY FLUCTUATIONS IN THE SHORT TERMSSHOULD NOT EXCEED A DEFINED TOLERANCE (TYPICALLY ± 5%).

EFFECT OF LOW HUMIDITY IN ART GALLERIES, MUSEUMS, LIBRARIES

“LA GIOCONDA” BY LEONARDO DA VINCIPAINTING ON POPLAR TABLE (LOUVRE)

FRENCH WOOD SCULPTURE (16TH CENTURY)

PAINTING ON CANVAS (19TH CENTURY)

EFFECT OF LOW HUMIDITY IN FOODSTUFF PRESERVATIONTEMPERATURE AND RELATIVE HUMIDITY ARE FUNDAMENTAL FACTORS FOR A PROPERFOOD CONSERVATION.

FRESH MEATS SHOULD BE STORED AT A TEMPERATURE NOT HIGHER THAN 2°CWITH ARELATIVE HUMIDITY AROUND 70%; A HIGHER HUMIDITY WOULD BE RISKY FOR AMICROORGANISMS GROWTH, BUT A LOWER ONE WOULD CAUSE A LOSS OF WEIGHT.

THE MATURATION OF RAW HAMS OR DRY SAUSAGES REQUIRES CONTROLLED AIRHUMIDITY, STARTING FROM 90–95% AND, AFTER A CERTAIN PERIOD, FINALIZING THEPROCESS AT 70–75% AT 6‐10°C.A LOWER RELATIVE HUMIDITY WOULD CAUSE A COSTLY LOSS OF WEIGHT: THE WATERCONTAINED IN A PATANEGRA HAMMAY COST MORE THAN 100 €/LITER !!

FRUITS AND VEGETABLES OPTIMAL STORAGE TEMPERATURE IS AROUND 2‐4°C WITHA HUMIDITY HIGHER THAN 90% (WITH EXCEPTIONS LIKE BANANAS, MELONS, CITRUS,PINEAPPLES AND OTHERS REQUIRING 10‐15°C AND A SLIGHTLY LOWER RH).

ALSO THE STABILITY OF THERMOHYGROMETRIC CONDITIONS IS VERY IMPORTANT: AFREQUENT FLUCTUATION EVEN OF FEW °C OR HUMIDITY PERCENT PROVOKES WATERASBORBING/DESORBING CYCLES FROM FOOD THROUGH CELL MEMBRANES WHICHCAUSES A SORT OF «FATIGUE» WITH A FASTER VISUAL AND QUALITY DETERIORATION.

EFFECT OF LOW HUMIDITY IN WINERY CELLARS 

THE HUMIDIFICATION OF THE WINE CELLAR IS CRUCIALBOTH DURING THE AGING OF WINE IN OAK BARRELSAND DURING STORAGE OF THE BOTTLES PLACEDHORIZONTALLY.

THE WINE WITHIN BOTTLES OR WITHIN BARRELS HAS AVAPOR PRESSURE EQUAL TO THE SATURATION VALUEHOWEVER THE CELLAR, ALTHOUGH AT THE SAMETEMPERATURE, IS NORMALLY FAR FROM 100% RELATIVEHUMIDITY: THUS, DUE TO PRESSURE DIFFERENCE,WATER VAPOR IS PUSHED TO ESCAPE THROUGH THEBOTTLE CORK OR THROUGH THE BARREL STAVES,PARTICUARLY IF THEY ARE NOT PERFECTLY TIGHT.

IN ORDER TO MINIMIZE THE RISK TO DEHYDRATE AND DRY THE CORKS OR TODESSICATE THE BARREL STAVES, IN WHICH CASE THE WINE WOULD EVAPORATE ANDLET AIR ENTER ALTERING THE ORGANOLEPTIC PROPERTIES AND THE STRUCTURE OFTHE WINE, IN A WINE CELLAR THE RELATIVE HUMIDITY SHOULD BE MAINTAINED AT75%‐80%.

EFFECT OF LOW HUMIDITY ON WATER‐BORNE PAINTINGCOATINGSTHE USE OF WATER‐BASED COATINGS IS INCREASING ‐ PARTICULARLY IN AUTOMOTIVE

AND AEROSPACE INDUSTRIES ‐ DUE TO LEGISLATION ON THE EMISSION OF VOC(VOLATILE ORGANIC COMPOUND) REPLACING MANY SOLVENT‐BASED COUNTERPARTS.HUMIDITY AND TEMPERATURE HAVE A SIGNIFICANT EFFECT ONHOW FAST WATER‐BORNE PAINT FLASHES OFF: THE WATER ISREMOVED FROM THE SURFACE OF THE PAINT VIAEVAPORATION, MIGRATING TO THE SURFACE UNTIL ALL OF ITHAS RISEN TO THE SURFACE AND EVAPORATED.THE TIME IN WHICH THE COATING IS DRY IS BASED ON THEAMOUNT OF WATER TO BE REMOVED AND THE EVAPORATIONRATE, DEPENDENT UPON THE VAPOR PRESSURE DIFFERENCEBETWEEN THE WATER IN THE COATING AND THE AIR HUMIDITYIN ADDITION TO AIR VELOCITY.THE FINAL QUALITY IS BASED ON THE THERMOHYGROMETRICCONTROL OF THE AIR RECIRCULATED IN THE SPRAY BOOTH ALLOVER THE YEAR, IRRESPECTIVE OF SEASONAL CONDITIONS.THE DESIGN RELATIVE HUMIDITY (50‐70%) DEPENDS ON THEPAINTING MATERIAL AND THE PROCESS; THE ACCURACYREQUIRED FOR HUMIDITY CONTROL IS AS LOW AS 2‐3%.

High humidity causes an excessivediluition of the enamel depositedonthe body and formation ofminuscule blister of liquid

Low humidity causes an earlyevaporation of the watercontained in the paints, sofluidity and covering capacitydecrease

STATIC ELECTRICITY IS USUALLY CAUSED WHEN CERTAIN MATERIALS ARE RUBBED AGAINSTEACH OTHER; IT IS ALSO CAUSED WHEN MATERIALS ARE PRESSED AGAINST EACH OTHERAND PULLED APART: THIS CHARGE MAY BE TRANSFERRED FROM THE MATERIAL TO NEXTGROUNDED OBJECT, CREATING AN ELECTROSTATIC DISCHARGE (ESD) WITH A SPARK.

BEYOND THE MATERIALS, THE AMOUNT OF CHARGE IS AFFECTED BY THE AREA OFCONTACT, THE SPEED OF SEPARATION AND RELATIVE HUMIDITY.IN DRY AIR, WHERE THE IMBALANCED CHARGES HAVENOWHERE TO GO, TYPICAL VOLTAGE LEVELS MAY EASILY ARRIVETO 30.000‐ 40.000 VOLTS.

TYPICAL ENERGY RELEASED BY A SPARK RARELY EXCEEDS 160 mJWHICH, WHILE WELL BELOW THE RISKY LIMIT OF 5 J, CAUSESANYWAY PHISICAL AND EMOTIONAL TROUBLES TO PEOPLE.

AN ESD WITH A VOLTAGE AS LOW AS 15‐30 V CAN CAUSE VERYOFTEN A DESTRUCTIVE DAMAGE TO AN INTEGRATED CIRCUIT.HOWEVER AIR WITH A RELATIVE HUMIDITY HIGHER THAN 30‐35% SERVES AS A NATURALCONDUCTOR THAT ALLOWS CHARGES TO LEAVE OBJECTS. MOLECULES OF WATER TOUCHTHE OBJECT AND ABSORB THE CHARGE AND, IN TURN, COME INTO CONTACT WITH OTHERMOLECULES OF VAPOR, CAUSING THE EXCESS CHARGES TO SPREAD AWAY.

EFFECT OF LOW HUMIDITY ON ELECTROSTATIC DISCHARGES (ESD)

EFFECT OF LOW HUMIDITY ON SEMICIRCULAR LIPOATROPHY (LS)

THE SEMICIRCULAR LIPOATROPHY IS A BENIGN AND REVERSIBLEDISORDER OF THE SUBCUTANEOUS FAT THAT IS OFTENMANIFESTED WITH A COLLAPSE IN THE ANTERIOR AND LATERALTHIGH SURFACE AND IN THE FOREARMS; USUALLY AFFECTINGFEMALE OFFICE WORKERS, IT MAY BE PRESENT BOTH IN ONEEXTREMITY (UNILATERAL) OR BOTH (BILATERAL) AND CAN BEACCOMPANIED BY ITCHING, CHANGES IN THE SENSITIVITY OFTHE AREA AND, LESS FREQUENTLY, BY DISCOMFORT AND PAIN.Environmental risks

Electronic devices

Conductive floor

Conductivedesks

95% of subjectsare women

Thighsand 

forearmsare the most

affected

72 cm:height of office desks matchingwith the level of affected areas

THIS DISEASE APPEARED IN EPIDEMIC FORM IN FEBRUARY 2007 IN BARCELONA, ANDSINCE THEN IN A GREATER NUMBER OF CASES IN DIFFERENT OFFICES IN THE COUNTRY.

DESPITE STILL FAIRLY UNKNOWN, LS HAS TO DO WITH THEPOSITION IN FRONT OF A DESK WITH UNGROUNDEDMETAL FRAMES, AND WITH A LOW RELATIVE HUMIDITYWHICH FAVORS ELECTROSTATIC DISCHARGES (ESD).IN OFFICES WHERE LS LESIONS HAVE BEEN IDENTIFIEDMAGNETIC FIELDS WERE ALWAYS SIGNIFICANTLY HIGHAND THE RELATIVE HUMIDITY WAS BELOW 30%‐35%.

IN ORDER TO PREVENT LS THE ENVIRONMENTALRELATIVE HUMIDITY SHOULD NOT BE LOWER THAN 35%

LS: depression on the thighs in the form of semi‐circular band 

COMFORT IN OCCUPIED SPACES INDUSTRIAL ENVIRONMENTSOFFICES, SHOP MALLS, THEATERS 30%‐35% (1) AUTOMOTIVE PAINTING BOOTH 50%‐70% ± 2%

HEALTH CARE FACILITIES CELLOFANE WRAPPING 45%CERAMIC FACTORIES  60%

CRITICAL & INTENSIVE CARE 30% ELECTRICAL PRODUCTS  40%NEWBORNE NURSERY ROOMS     30% GUM  45%RECOVERY ROOMS 30% (2) LEATHER WORKINGS  40%OPERATING ROOMS 30% (3) LENS GRINDING 80%

ART GALLERIES, MUSEUMS, LIBRARIES PAPER WORKING 45%PAINT 80%

ART GALLERIES, MUSEUMS 40% PHOTO STUDIOS  40%LIBRARIES 40% PHOTOGRAPHIC MATERIAL FACILITIES  30%

DATACOM FACILITIES PLYWOOD HOT PRESSING 60%PRINTING PLANTS  45%

DATA CENTERS 30%‐35% (4) SEMICONDUCTORS FACTORIES   35%‐40% ± 2%TELECOMMUNICATION FACILITIES 20% TEXTILE PLANTS – KNITTING 45%

CLEAN ROOMS ‐ LABORATORIES TOBACCO SOFTENING 85%TOBACCO CIGAR/CIGARETTE MAKING  55%

CLEAN ROOMS 40%‐50% ± 5% WOOD WORKING  45%LABORATORIES 35%‐50% FOODSTUFF CONSERVATION

HOTEL, MOTEL, DORMITORIES FRUITS 70%‐90%HOTEL, MOTEL 30% HAM ‐ SAUSAGES 75%DORMITORIES, JAILS 30% MEAT 70%

ANIMAL AND CROP FARMS TEA 65%TOBACCO 65%

ANIMALS 40‐50 40% VEGETABLES 90%ENVIRONMENTAL CONTROL FOR PLANTS 50% WINERIES >75%‐80%

1) ANSI/ASHRAE STANDARD 55‐2013 does not specify a minimum humidity level for thermal comfort. Non‐thermal comfort factors , such as skin drying, irritation of mucus membranes, dryness of the eyes,  and static electricity generation, may place limits on the acceptability of very low humidity environments.

2) ANSI/ASHRAE/ASHE 170‐2013 suggests no lower limits: see above.3) ANSI/ASHRAE/ASHE 170‐2013 suggests a limits of 20%; a higher value is advisable for older electronic equipment and for risk of gas explosion.due to sparks.4) Lower values (i.e.: 20%) are allowable for servers rooms; a limit of 30% is recommended for personnel health reasons.

RECOMMENDED MINIMUM RELATIVE HUMIDITY LIMITS

HUMIDIFICATION TECHNOLOGIES

TYPE OF HUMIDIFIERS

ISOTHERMAL HUMIDIFIERSTHE VAPOR GENERATION CAN BEOBTAINED BY PROVIDING EXTERNALENERGY THAT IS USED TO HEAT THEWATER TO BOILING TEMPERATUREAND THEN TO OBTAIN ITS CHANGEOF STATE.THE HOT STEAM PRODUCED ISDISPERSED IN THE AIR WHOSETEMPERATURE IS RAISED TO A SMALLEXTENT; FOR THIS REASON THEPROCESS IS CALLED ISOTHERMAL.THE HUMIDIFIERS OF THIS TYPE ARECOMMONLY ENERGIZED WITH ELECTRICITY AND THEREFORE HAVE AN OPERATING COSTWHICH OFTEN RESTRICTS THEIR APPLICATION TO LIMITED CAPACITIES.FOR HIGHER RATES ARE AVAILABLE EQUIPMENT BASED ON THE COMBUSTION OFMETHANE OR LPG.ISOTHERMAL HUMIDIFIERS ARE FAIRLY SIMPLE TO INSTALL, ENSURE THE HYGIENICPROPERTIES OF LIVE STEAM AND CAN BE USED BOTH FOR DIRECT DISTRIBUTION IN THEROOM OR IN DUCTED AIR HANDLING UNITS.

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DRY BULB TEMPERATURE ‐ °C

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3

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1,82

21,2

11,3

4,30,72

Isothermal humidifcation of air to bring the absolute humidity from 4,3 g/kg (@ 20°C ‐ 30% RH) to 11,3  g/kg (introduction of 7 g/kg of dry air)

1 Water fill valve 8 Cylinder full probe2 Flow restrictor 9 Electrode leads3 Filling pipe 10 Electrodes4 Cylinder fill pipe 11 Steam cylinder5 Overfill pipe 12 Bottom filter6 Conductivity probe 13 Drain valve or pump7 Fill cup

IT IS A SIMPLE AND LOW PRICED TYPE OF EQUIPMENT INWHICH TWO OR MORE METAL ELECTRODES CONNECTEDTO ELECTRICAL MAINS USE WATER AS A RESISTIVEELEMENT, HEATING IT UP TO BOILING POINT.

THE CAPACITY CONTROL IS GOT BY VARYING THE DEPTHOF IMMERSION OF THE ELECTRODES BY MEANS OF THEFILLING AND WATER DRAINAGE SOLENOID VALVES.

IMMERSED ELECTRODE HUMIDIFIERS SHOULD BE FEDWITH NORMAL DRINKING WATER: THE ONLY REQUIREDMAINTENANCE IS CLEANING OR REPLACEMENT OF THECYLINDER WHEN ELECTRODES ARE COVERED WITH LIME.

THEY ARE AVAILABLE IN A RANGE FROM 1 TO 130 KG/H.

IMMERSED ELECTRODE HUMIDIFIERS

STEAM CYLINDER

1 Antifoaming sensor 11 Drain tempering pipe2 Overfill diaphragm 12 Drain tempering valve3 Filling diaphragm 13 Filling valve4 Filling tank 14 Drain pump5 Conductivity probe 15 Antiadhesive film6 Equalizer pipe 16 Overtemperature PTC7 Fill cup 17 Heaters8 Filling pipe 18 Water temp. sensor9 Level sensor 19 Thermal insulation10 Overflow pipe

WITH THE ABILITY TO ELECTRONICALLY MODULATE THEPOWER OF THE HEATERS BY MEANS OF SOLID STATERELAYS, ADVANCED DEVICES ALLOW VERY HIGH LEVELSOF ACCURACY (± 1%) IN CONTROLLED HUMIDITY.

THEY CAN OPERATE WITH NORMAL TAP DRINKINGWATER HOWEVER THE USE OF DEMINERALIZED WATERREDUCES MAINTENANCE VIRTUALLY TO ZERO.

THE POWER RANGE ARRIVES UP TO 80 KG/H.

IMMERSED HEATER HUMIDIFIERS

THESE DEVICES INCLUDE RESISTIVE ELEMENTSWHICH ARE SUPPLIED WITH ELECTRICITY TOBOIL THE WATER THAT IS MAINTAINED AT ACONSTANT LEVEL IN A TANK.

HEATING ELEMENT

1 Water on‐off tap 13 Gas line2 Filling valve 14 Gas on‐off tap3 Antifoaming sensor 15 Gas burner(s)4 Steam outlets 16 Drain valve5 Boiler 17 Filter6 Flue gas 18 Drain pump7 Electrical panel 19 Drain network8 Gas temp. sensor 20 Conductivity meter9 Level sensor 21 Drain pipe10 Preheat sensor 22 Water line11 Heat exchanger(s) 23 Safety thermostat12 Air inlet 24 Bottom drain pipe

THE PRINCIPLE OF OPERATION OF THESE DEVICES, INWHICH NATURAL GAS OR LPG ARE BURNED INSIDEOF A STAINLESS STEEL HEAT EXCHANGER IMMERSEDIN THE WATER, IS SIMILAR TO THAT OF THEELECTRICAL HEATER ONES; STEAM PRODUCTION ISFINELY MODULATED BY ADJUSTING THE GAS SUPPLY.

THE MAIN ADVANTAGE STANDS IN THE LOWER COSTOF ENERGY SOURCE COMPARED WITH ELECTRICITY.

THEY CAN OPERATE BOILING DRINKABLE MAINSWATER OR DEMINERALISED WATER, IN THIS CASEDRASTICALLY REDUCING REGULAR MAINTENANCE.

THE AVAILABLE RANGE CAN REACH UP TO 360 KG/H.

GAS FIRED HUMIDIFIERS

HEAT EXCHANGER

ADIABATIC HUMIDIFIERSALTERNATIVELY, THE EVAPORATIONCAN TAKE PLACE IN ADIABATICMODE, i.e. WITHOUT THE NEED OFEXTERNAL ENERGY.

THE HEAT REQUIRED FOR THEEVAPORATION IS SUPPLIED FROMTHE AIR THAT IS BEING HUMIDIFIED,SO THAT IT GETS COLDERFOLLOWING AN ISENTALPIC LINELIKE THE BLUE ONE IN THEPSYCROMETRIC DIAGRAM.FOR THIS REASON, IN ORDER TOMAINTAIN THE FINAL TEMPERATUREAT THE DESIRED VALUE, IT IS OFTEN NECESSARY A PREHEAT PROCESS (RED LINE).

ADIABATIC HUMIDIFIERS PROVIDE A WIDE AREA OF   INTERFACE BETWEEN THE AIR ANDTHE LIQUID WATER, WHICH EVAPORATES SPONTANEOUSLY. THE MAIN ADVANTAGE OFTHE ADIABATIC HUMIDIFICATION STANDS IN THE ENERGY CONSUMPTION: THE ONLYPOWER REQUIRED BY THE EQUIPMENT IS THAT FOR ATOMIZING OR RECIRCULATING THEWATER ACCORDING TO THE TECHNOLOGY USED.

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VAPO

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A

1

2

3

0

0,5

2,5

1,5

3,5

1,82

38,1

11,3

4,30,72

PREHEAT PROCESS                ADIABATIC HUMIDIFICATION

Adiabatic humidifcation of air to bring the absolute humidity from 4,3 g/kg (@ 20°C ‐ 30% RH) to 11,3  g/kg (introduction of 7 g/kg of dry air)

IN THIS KIND OF ADIABATIC HUMIDIFIERSTHE AIR IS PASSED THROUGH MODULARPADS, I.E.: HONEYCOMB STRUCTURES OFRESIN‐IMPREGNATED CELLULOSE OR GLASSFIBER OFFERING A WIDE INTERFACE AREA.

THE PADS, PLACED VERTICALLY, ARE KEPTWET BY A WATER FLOW DRAWN FROM ABOTTOM TANK BY A PUMP ANDDISTRIBUTED ON THEIR UPPER EDGE.

WET MEDIA HUMIDIFIERS

ONLY PART OF THE WATER DISTRIBUTED ONTO THE PADS EVAPORATES WHEN THE REST ISRECIRCULATED; THE EVAPORATION PROCESS INCREASES THE CONCENTRATION OF SALTSWHICH MAY BUILD UP ON THE SURFACE, FORCING TO CLEAN OR REPLACE THE PADSWHEN CLOGGED; FURTHERMORE THEY SHOULD BE PERIODICALLY CONTROLLEDBECAUSE THE PRESENCE OF A WARM WATER RECIRCULATION POTENTIALLY PROMOTES ARISKY BACTERIAL GROWTH.

LAST BUT NOT LEAST, THE AIR SIDE PRESSURE DROP OF THE PADS REQUIRES ANADDITIONAL ENERGY CONSUMPTION EVEN WHEN NO HUMIDIFICATION IS REQUIRED.

THEIR USE, WIDESPREAD FOR THE LIMITED PRICE, SHOULD BE CAREFULLY EVALUATEDLOOKING ALSO AT THE OPERATING COSTS.

HIGH PRESSURE ATOMISING SYSTEMS

THESE DEVICES ARE EQUIPPED WITH A VOLUMETRIC PUMP WHICH PRESSURIZES THEWATER TO VALUES BETWEEN 70 AND 100 BAR AND DELIVERS IT TO SMALL NOZZLES THATPRODUCE A FINE MIST (DROPLETS OF 10‐15 MICRON) EASILY ABSORBED BY AIR STREAM(*).

(*) the surface offered by 1 liter of water atomized at 15 micron is as high as 400 square meters

THE DISTRIBUTION PIPING NETWORK THAT SUPPORTS AND SUPPLIES THE NOZZLES ISPOSITIONED IN AN AIR DUCT OR PLACED DIRECTLY INTO THE ENVIRONMENT TO HUMIDIFY.THESE DEVICES MAY REACH AN EXCELLENT LEVEL OF ACCURACY (± 2%) OF THE HUMIDITY INTHE CONTROLLED SPACE AND VERY HIGH CAPACITIES WITH A NEGLIGIBLE ELECTRICCONSUMPTION ABSORBED BY THE PUMP (<4 W PER LITER OF SPRAYED WATER).

THEY ARE HYGIENICALLY SAFE WITH NO BACTERIAL GROWTH BECAUSE THE QUANTITY OFNON ABSORBED WATER ‐ USUALLY VERY SMALL, IF ANY ‐ IS DRAINED OFF.THE USE OF DEMINERALISED OR SWEETENED WATER IS RECOMMENDED TO PREVENTCLOGGING OF THE NOZZLES.THESE ATOMISING SYSTEMS MAY REACH A CAPACITY OF MANY THOUSANDS OF KG/H

PUMPING STATION ATOMIZING NOZZLE NOZZLE RACK NOZZLE RACK IN AHU SECTION SUSPENDED TYPE

1 Air filter 9 Float level sensor2 Rear fans 10 Tank3 Atomised water 11 Driver4 Diffuser 12 Piezo transducer5 Atomisation chamber 13 Power supply6 Fill valve 14 Front fans7 Overflow pipe 15 Laminar air flow8 Drain valvce

ULTRASONIC HUMIDIFIERS PROVIDE AN EXTRA FINEATOMIZATION OF WATER (≈ 3 μm) BY MEANS OF THE HIGH‐FREQUENCY VIBRATION (CLOSE TO 1,7 MHZ) OF APIEZOELECTRIC ELEMENT OR MORE, IN PARALLEL.N.B.:  the surface offered by 1 liter of water atomized at 3 micron is 2000 square meters

BEST ULTRASONIC HUMIDIFIERS REACH EXCEPTIONALLEVELS OF PRECISION (± 1%) IN THE ENTIRE RANGE OFTHEIR RATED CAPACITY AND, THANKS TO THE HIGHEFFICIENCY OF ABSORPTION, THEY ARE SUITABLE FOR THEDISTRIBUTION OF THE PRODUCED MIST DIRECTLY INTO THEROOM AS WELL AS IN DUCTED SYSTEMS.DUE TO SIZE AND COST THEY ARE CONVENIENT FOR SMALLAND MEDIUM INSTALLATIONS (0,5 TO 15 kg/h).FOR ULTRASONIC HUMIDIFIERS THE USE OFDEMINERALISED WATER IS HIGHLY RECOMMENDED.

ULTRASONIC HUMIDIFIERS

STAND ALONE UNIT SMALL SIZE UNITDUCTED TYPE UNIT

VAPOR PRODUCTION< 2 kg/h 2‐20 kg/h 20‐100 kg/h > 100 kg/h

ISOTHERMAL HUMIDIFIERS

IMMERSED ELECTRODES HIGH ELECTRICAL ENERGY INPUT

IMMERSED HEATERS HIGH ELECTRICAL ENERGY INPUT

GAS FIRED TOO SMALL

ADIABATIC HUMIDIFIERS

HIGH PRESSURE ATOMISERS TOO SMALL

ULTRASONIC TOO LARGE TOO LARGE

WET MEDIA TOO SMALL TOO SMALL

HYGIENIC PROPERTIES

DISTRIBUTION SYSTEM

DIRECT IN ROOM DUCTED

ISOTHERMAL HUMIDIFIERS

IMMERSED ELECTRODES

IMMERSED HEATERS

GAS FIRED

ADIABATIC HUMIDIFIERS

HIGH PRESSURE ATOMISERS WITH NO RECIRCULATION

WITH DISTRIBUTED TERMINALS

ULTRASONIC IF EQUIPPED WITH AUTOMATIC DRAINAGE

WET MEDIA REGULAR INSPECTION REQUIRED NOT PRACTICAL

GENERAL SUITABILITY TABLE

MANY THANKS FOR YOUR ATTENTION

luigi.nalini@carel.com