rel humidity

8/9/2019 Rel Humidity

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Temperature

- t -

(oC)

Density

- -

(kg/m3)

Specific Weight

- -

(N/m3)

-40 1.514 14.85

-20 1.395 13.68

0 1.293 12.6

5 1.269 12.45

10 1.24 12.23

15 1.225 12.01

20 1.204 11.81

25 1.184 11.61

30 1.165 11.43

40 1.12 11.05

50 1.109 10.88

60 1.060 10.400 1.029 10.09

80 0.9996 9.803

90 0.921 9.533

100 0.9461 9.28

200 0.461 .31

300 0.6159 6.040

400 0.5243 5.142

500 0.4565 4.4

Relative humidity
http://www.engineeringtoolbox.com/temperature-d_291.htmlhttp://www.engineeringtoolbox.com/density-specific-weight-gravity-d_290.htmlhttp://www.engineeringtoolbox.com/density-specific-weight-gravity-d_290.htmlhttp://www.engineeringtoolbox.com/temperature-d_291.htmlhttp://www.engineeringtoolbox.com/density-specific-weight-gravity-d_290.htmlhttp://www.engineeringtoolbox.com/density-specific-weight-gravity-d_290.html


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!r"m Wi#ipe$ia% the free encyc&"pe$ia

'ump t"( na)igati"n%search

This artic&e is written like apersonal reflection or essayrather than an

encyclopedic description of the subject. *&ease he&p impr")e it+y re,riting it

in an encyc&"pe$ic sty&e. (September 2012)
http://en.wikipedia.org/wiki/Relative_humidity#mw-headhttp://en.wikipedia.org/wiki/Relative_humidity#mw-headhttp://en.wikipedia.org/wiki/Relative_humidity#p-searchhttp://en.wikipedia.org/wiki/Wikipedia:What_Wikipedia_is_not#PUBLISHERhttp://en.wikipedia.org/wiki/Wikipedia:What_Wikipedia_is_not#PUBLISHERhttp://en.wikipedia.org/w/index.php?title=Relative_humidity&action=edithttp://en.wikipedia.org/wiki/Wikipedia:Encyclopedic_stylehttp://en.wikipedia.org/wiki/File:Relative_Humidity.pnghttp://en.wikipedia.org/wiki/Relative_humidity#mw-headhttp://en.wikipedia.org/wiki/Relative_humidity#p-searchhttp://en.wikipedia.org/wiki/Wikipedia:What_Wikipedia_is_not#PUBLISHERhttp://en.wikipedia.org/w/index.php?title=Relative_humidity&action=edithttp://en.wikipedia.org/wiki/Wikipedia:Encyclopedic_style


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4/12

The re&ati)e humi$ity "f an air-,ater miture is $efine$ as the rati" "f thepartia&

pressure"f ,ater )ap"r 72 in the miture t" the saturate$ )ap"r pressure"f

,ater at a prescri+e$ temperature.

e&ati)e humi$ity is n"rma&&y epresse$ as a percentage an$ is ca&cu&ate$ +y using thef"&&",ing euati"n(:1;

Measurement

The humi$ity "f an air-,ater )ap"r miture is $etermine$ thr"ugh the use "f

psychr"metric charts if +"th the$ry +u&+ temperatureT an$ the ,et +u&+

temperatureTw "f the miture are #n",n. These uantities are rea$i&y estimate$ +yusing a s&ingpsychr"meter.

There are se)era& empirica& c"rre&ati"ns that can +e use$ t" estimate the saturate$

)ap"r pressure "f ,ater )ap"r as a functi"n "f temperature. The nt"ine euati"nis

am"ng the &east c"mp&e "f these f"rmu&as% ha)ing "n&y three parameters % % an$

. ther c"rre&ati"ns% such as the th"se presente$ +y


5/12

Significance

Climate control

&imate c"ntr"& refers t" the c"ntr"& "f temperature an$ re&ati)e humi$ity f"r humanc"mf"rt% hea&th an$ safety% an$ f"r the technica& reuirements "f machines an$

pr"cesses% in +ui&$ings% )ehic&es an$ "ther enc&"se$ spaces.

Comfort

7umans are sensiti)e t" humi$ air +ecause the human +"$y uses e)ap"rati)e c""&ing

as the primary mechanism t" regu&ate temperature. Bn$er humi$ c"n$iti"ns% the rate

at ,hich perspirati"n e)ap"rates "n the s#in is &",er than it ,"u&$ +e un$er ari$

c"n$iti"ns. ecause humans percei)e the rate o& %eat tran'&erfr"m the +"$y rather

than temperature itse&f%:5;,e fee& ,armer at a gi)en temperature ,hen the re&ati)e

humi$ity is high than ,hen it is &",.

!"r eamp&e% if the air temperature is 24 > 5 >! an$ the re&ati)e humi$ity is @er"

percent% then the air temperature fee&s &i#e 21 > 69 >!.:6;Af the re&ati)e humi$ity is

100 percent at the same air temperature% then it fee&s &i#e 2 > 80 >!. :6;An "ther

,"r$s% if the air is 24 > 5 >! an$ c"ntains saturate$ ,ater )ap"r% then the human

+"$y c""&s itse&f at the same rate as it ,"u&$ if it ,ere 2 > 80 >! an$ $ry.:6;The

heat in$ean$ the humi$eare in$ees that ref&ect the c"m+ine$ effect "f

temperature an$ humi$ity "n the c""&ing effect "f the atm"sphere "n the human +"$y.

uildings

!"r c&imate c"ntr"& in +ui&$ings using 7systems% the #ey is t" maintain the

re&ati)e humi$ity at a c"mf"rta+&e range C &", en"ugh t" +e c"mf"rta+&e +ut high

en"ugh t" a)"i$ pr"+&ems ass"ciate$ ,ith )ery $ry air.

When the temperature is high an$ the re&ati)e humi$ity is &",% e)ap"rati"n "f ,ater is

rapi$ s"i& $ries% ,et c&"thes hung "n a &ine "r rac# $ry uic#&y% an$ perspirati"n

rea$i&y e)ap"rates fr"m the s#in. W""$en furniture can shrin#% causing the paint that

c")ers these surfaces t" fracture.

When the temperature is high an$ the re&ati)e humi$ity is high% e)ap"rati"n "f ,ateris s&",. When re&ati)e humi$ity appr"aches 100 percent% c"n$ensati"n can "ccur "n

surfaces% &ea$ing t" pr"+&ems ,ith m"&$% c"rr"si"n% $ecay% an$ "ther m"isture-re&ate$

$eteri"rati"n.

ertain pr"$ucti"n an$ technica& pr"cesses an$ treatments in fact"ries% &a+"rat"ries%

h"spita&s% an$ "ther faci&ities reuire specific re&ati)e humi$ity &e)e&s t" +e maintaine$

using humi$ifiers% $ehumi$ifiersan$ ass"ciate$ c"ntr"& systems.

!ehicles

e&ati)e humi$ity% a&s" ca&&e$ %#midit$ ratiois c&assifie$ in three ,ays(
http://en.wikipedia.org/wiki/Relative_humidity#cite_note-4http://en.wikipedia.org/wiki/Relative_humidity#cite_note-hswref-5http://en.wikipedia.org/wiki/Relative_humidity#cite_note-hswref-5http://en.wikipedia.org/wiki/Relative_humidity#cite_note-hswref-5http://en.wikipedia.org/wiki/Relative_humidity#cite_note-hswref-5http://en.wikipedia.org/wiki/Heat_indexhttp://en.wikipedia.org/wiki/Humidexhttp://en.wikipedia.org/wiki/HVAChttp://en.wikipedia.org/wiki/Dehumidifierhttp://en.wikipedia.org/wiki/Relative_humidity#cite_note-4http://en.wikipedia.org/wiki/Relative_humidity#cite_note-hswref-5http://en.wikipedia.org/wiki/Relative_humidity#cite_note-hswref-5http://en.wikipedia.org/wiki/Relative_humidity#cite_note-hswref-5http://en.wikipedia.org/wiki/Heat_indexhttp://en.wikipedia.org/wiki/Humidexhttp://en.wikipedia.org/wiki/HVAChttp://en.wikipedia.org/wiki/Dehumidifier


6/12

1. "n the +asis "f pressure partia& pressure "f )ap"r in air E pressure "f saturate$

air

2. "n the +asis "f mass mass "f )ap"ur present in air E mass "f $ry air

3. "n the +asis "f $ensity $ensity "f the )ap"ur present in air E $ensity "f $ry air

&& three in a specific )"&ume "f the m"ist air at a sing&e gi)en temperature. The same+asic princip&es as in +ui&$ings% a+")e% app&y. An a$$iti"n there may +e safety

c"nsi$erati"ns. !"r instance% high humi$ity insi$e a )ehic&ecan &ea$ t" pr"+&ems "f

c"n$ensati"n% such as misting "f ,in$shie&$san$ sh"rting"f e&ectrica& c"mp"nents.

An sea&e$ )ehic&es an$pressure )esse&ssuch as pressuri@e$ air&iners%su+mersi+&esan$

spacecraft% these c"nsi$erati"ns may +e critica& t" safety% an$ c"mp&e en)ir"nmenta&

c"ntr"& systemsinc&u$ing euipment t" maintainpressureare nee$e$. ir&iners

"perate ,ith &", interna& re&ati)e humi$ity% "ften un$er 10=% especia&&y "n &"ng

f&ights. The &", humi$ity is a c"nseuence "f $ra,ing in the )ery c"&$ air ,ith a &",

a+s"&ute humi$ity%,hich is f"un$ at air&iner cruising a&titu$es. Su+seuent ,arming

"f this air &",ers its re&ati)e humi$ity. This causes $isc"mf"rt such as s"re eyes% $rys#in% an$ $rying "ut "f muc"sa% +ut humi$ifiers are n"t emp&"ye$ t" raise it t"

c"mf"rta+&e mi$-range &e)e&s +ecause the )"&ume "f ,ater reuire$ t" +e carrie$ "n

+"ar$ can +e a significant ,eight pena&ty. s air&iners $escen$ fr"m c"&$er a&titu$es

int" ,armer air perhaps e)en f&ying thr"ugh c&"u$s a fe, th"usan$ feet a+")e the

gr"un$% the am+ient re&ati)e humi$ity can increase $ramatica&&y. S"me "f this m"ist

air is usua&&y $ra,n int" the pressuri@e$ aircraft ca+in an$ int" "ther n"n-pressuri@e$

areas "f the aircraft an$ c"n$enses "n the c"&$ aircraft s#in. Fiui$ ,ater can usua&&y

+e seen running a&"ng the aircraft s#in% +"th "n the insi$e an$ "utsi$e "f the ca+in.

ecause "f the $rastic changes in re&ati)e humi$ity insi$e the )ehic&e% c"mp"nents

must +e ua&ifie$ t" "perate in th"se en)ir"nments. The rec"mmen$e$ en)ir"nmenta&

ua&ificati"ns f"r m"st c"mmercia& aircraft c"mp"nents is &iste$ in T D-160.

"viation

"&$ humi$ air can pr")"#e the f"rmati"n "f ice% ,hich is a $anger t" aircraft as it

affects the ,ing pr"fi&e an$ increases ,eight. ar+urete$ engines ha)e a further

$anger "f ice f"rming insi$e thecar+uret"r. )iati"n ,eather rep"rts /TGs

theref"re inc&u$e an in$icati"n "f re&ati)e humi$ity% usua&&y in the f"rm "f the $e,

p"int.

An a$$iti"n% air ,ith higher humi$ity is &ess $ense% pr")i$ing &",er &ift an$ &",erpr"pe&&er "r tur+ine efficiency this is s"me,hat "ffset +y $ecrease$ $rag. *i&"ts must

ta#e humi$ity int" acc"unt ,hen ca&cu&ating ta#e"ff $istances +ecause high humi$ity

,i&& reuire &"nger run,ays an$ ,i&& $ecrease the c&im+ gra$ient.

Pressure dependence

The re&ati)e humi$ity "f an air-,ater system is $epen$ent n"t "n&y "n the temperature

+ut a&s" "n the a+s"&ute pressure "f the system "f interest. This $epen$ence is

$em"nstrate$ +y c"nsi$ering the air-,ater system sh",n +e&",. The system is c&"se$

i.e.% n" matter enters "r &ea)es the system.
http://en.wikipedia.org/wiki/Vehiclehttp://en.wikipedia.org/wiki/Windshieldhttp://en.wikipedia.org/wiki/Short_circuithttp://en.wikipedia.org/wiki/Pressure_vesselhttp://en.wikipedia.org/wiki/Pressure_vesselhttp://en.wikipedia.org/wiki/Airlinerhttp://en.wikipedia.org/wiki/Submersiblehttp://en.wikipedia.org/wiki/Submersiblehttp://en.wikipedia.org/wiki/Spacecrafthttp://en.wikipedia.org/wiki/Environmental_control_systemhttp://en.wikipedia.org/wiki/Environmental_control_systemhttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Humidity#Absolute_humidityhttp://en.wikipedia.org/wiki/Humidity#Absolute_humidityhttp://en.wikipedia.org/wiki/Mucosahttp://en.wikipedia.org/wiki/Carburetorhttp://en.wikipedia.org/wiki/Carburetorhttp://en.wikipedia.org/wiki/METARhttp://en.wikipedia.org/wiki/METARhttp://en.wikipedia.org/wiki/Dew_pointhttp://en.wikipedia.org/wiki/Dew_pointhttp://en.wikipedia.org/wiki/Vehiclehttp://en.wikipedia.org/wiki/Windshieldhttp://en.wikipedia.org/wiki/Short_circuithttp://en.wikipedia.org/wiki/Pressure_vesselhttp://en.wikipedia.org/wiki/Airlinerhttp://en.wikipedia.org/wiki/Submersiblehttp://en.wikipedia.org/wiki/Spacecrafthttp://en.wikipedia.org/wiki/Environmental_control_systemhttp://en.wikipedia.org/wiki/Environmental_control_systemhttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Humidity#Absolute_humidityhttp://en.wikipedia.org/wiki/Mucosahttp://en.wikipedia.org/wiki/Carburetorhttp://en.wikipedia.org/wiki/METARhttp://en.wikipedia.org/wiki/Dew_pointhttp://en.wikipedia.org/wiki/Dew_point


7/12

Af the system at State is is"+arica&&y heate$ heating ,ith n" change in system

pressure then the re&ati)e humi$ity "f the system $ecreases +ecause the saturate$

)ap"r pressure "f ,ater increases ,ith increasing temperature. This is sh",n in State.

Af the system at State is is"therma&&y c"mpresse$ c"mpresse$ ,ith n" change in

system temperature then the re&ati)e humi$ity "f the system increases +ecause the

partia& pressure "f ,ater in the system increases ,ith increasing system pressure. This

is sh",n in State .

Theref"re a change in re&ati)e humi$ity can +e ep&aine$ +y a change in system

temperature% a change in the a+s"&ute pressure "f the system% "r change in +"th "f

these system pr"perties.
http://en.wikipedia.org/wiki/File:Changes_in_Relative_Humidity.png


8/12

#nhancement factor

The enhancement fact"r is $efine$ as the rati" "f the saturate$ )ap"r pressure "f

,ater in m"ist air t" the saturate$ )ap"r pressure "f pure ,ater.

The enhancement fact"r is eua& t" unity f"r i$ea& gas systems. 7",e)er% in rea&

systems the interacti"n effects +et,een gas m"&ecu&es resu&t in a sma&& increase "f the

saturati"n )ap"r pressure "f ,ater in air re&ati)e t" saturate$ )ap"r pressure "f pure

,ater )ap"r. Theref"re% the enhancement fact"r is n"rma&&y s&ight&y greater than unity

f"r rea& systems.

The enhancement fact"r is c"mm"n&y use$ t" c"rrect the saturate$ )ap"r pressure "f,ater )ap"r ,hen empirica& re&ati"nships% such as th"se $e)e&"pe$ +y We&er%


9/12

gas in this c"ntet is referre$ t" as saturate$ ,hen the )ap"r pressure "f ,ater in the

air is at the eui&i+rium )ap"r pressure f"r ,ater )ap"r at the temperature "f the gas

an$ ,ater )ap"r miture &iui$ ,ater an$ ice% at the appr"priate temperature ,i&&

fai& t" &"se mass thr"ugh e)ap"rati"n ,hen ep"se$ t" saturate$ air. At may a&s"

c"rresp"n$ t" the p"ssi+i&ity "f $e,"r f"gf"rming% ,ithin a space that &ac#s

temperature $ifferences am"ng its p"rti"ns% f"r instance in resp"nse t" $ecreasing

temperature. !"g c"nsists "f )ery minute $r"p&ets "f &iui$% primari&y he&$ a&"ft +y

is"static m"ti"n in "ther ,"r$s% the $r"p&ets fa&& thr"ugh the air at termina& )e&"city%

+ut as they are )ery sma&&% this termina& )e&"city is )ery sma&& t""% s" it $"esnGt &""# t"

us &i#e they are fa&&ing% an$ they seem t" +e he&$ a&"ft.

The statement that re&ati)e humi$ity 7= can ne)er +e a+")e 100=% ,hi&e a fair&y

g""$ gui$e% is n"t a+s"&ute&y accurate% ,ith"ut a m"re s"phisticate$ $efiniti"n "f

humi$ity than the "ne gi)en here. n argua+&e ecepti"n is the Wi&s"n c&"u$ cham+er%

,hich uses% in nuc&ear physics eperiments% an etreme&y +rief state "f

Hsupersaturati"nH t" acc"mp&ish its functi"n.

!"r a gi)en $e,p"intan$ its c"rresp"n$inga+s"&ute humi$ity% the re&ati)e humi$ity

,i&& change in)erse&y% a&+eit n"n&inear&y% ,ith the temperature. This is +ecause the

partia& pressure "f ,ater increases ,ith temperature I the "perati)e princip&e +ehin$

e)erything fr"m hair $ryerst" $ehumi$ifiers.
http://en.wikipedia.org/wiki/Dewhttp://en.wikipedia.org/wiki/Dewhttp://en.wikipedia.org/wiki/Foghttp://en.wikipedia.org/wiki/Foghttp://en.wikipedia.org/wiki/Wilson_cloud_chamberhttp://en.wikipedia.org/wiki/Supersaturationhttp://en.wikipedia.org/wiki/Dewpointhttp://en.wikipedia.org/wiki/Dewpointhttp://en.wikipedia.org/wiki/Absolute_humidityhttp://en.wikipedia.org/wiki/Absolute_humidityhttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Hair_dryerhttp://en.wikipedia.org/wiki/Hair_dryerhttp://en.wikipedia.org/wiki/Dehumidifierhttp://en.wikipedia.org/wiki/Dehumidifierhttp://en.wikipedia.org/wiki/File:Relative_Humidity.pnghttp://en.wikipedia.org/wiki/Dewhttp://en.wikipedia.org/wiki/Foghttp://en.wikipedia.org/wiki/Wilson_cloud_chamberhttp://en.wikipedia.org/wiki/Supersaturationhttp://en.wikipedia.org/wiki/Dewpointhttp://en.wikipedia.org/wiki/Absolute_humidityhttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Hair_dryerhttp://en.wikipedia.org/wiki/Dehumidifier


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*hysica& uantities
http://en.wikipedia.org/wiki/Category:Physical_quantitieshttp://en.wikipedia.org/wiki/Category:Physical_quantities

rel humidity

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