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Humid Air
Water vapor in air
Nitrogen78%
Oxygen 21%
Trace Glasses 1%Argon (A)Water vapor (H2O)Carbon dioxide (CO2)Neon (Ne)Helium (He)Krypton (Kr)Hydrogen (H)Ozone (O3)
Image by MIT OCW.
Humid Air
Water vapor in air saturation humidity (SH) (= max AH)moisture content (absolute humidity AH) = kgvapor / kgdry air
(partial) vapor pressure [Pa]relative humidity (RH)wet-and-dry bulb psychrometer GAZE
ETHER
Image by MIT OCW.
Humid Air
Water vapor in air saturation humidity (SH) (= max AH)moisture content (absolute humidity AH) = kgvapor / kgdry air
(partial) vapor pressure [Pa]relative humidity (RH) in [%]wet-and-dry bulb psychrometerenthalpy (H) in [kJ/kg] Sensible heat vs. Latent heat
specific volume
Humid Air
(kJ/kg)
P (kJ/k
g)
Abs
olut
e hu
mid
ity (g
/kg)
15
5
25
30
30
30 40506070
80
90
100
0.800
0.825
0.850
0.875
0.900
0.9250.950
(m 3/kg)110
120
130
28
100%
20
20
20
24
201612
8 40
0
0
0 0
0
10
10
10 10
10
20
20
30
30
40
40
40
50
5060
7080
90100
110 120 130
50
Saturat
ion lin
e
Dry bulb temperature ( C)o
Dry bulb temperature ( C)o
40%
20%
60%80%
Wet
bulb
tempe
rature
( C)
o
relative humidity RHwet bulb temperatureenthalpyspecific volume
Psychrometric chartabsolute humidity AH and saturation line
Image by MIT OCW.
Humid Air
Temperature Increase (Vapor to Liquid) or Decrease (Liquid Vapor)
P
Moi
stur
e re
mov
ed b
y so
rben
t or
a
dded
by
evap
orat
ion
Dew Point Temperature
Dew Point
Am
ount
of c
onde
nsat
ion
Hum
idity
Incr
ease
Lat
ent H
eat C
onte
nt In
crea
se
Total
Heat
(Enth
alpy)
BTU Per Pou
nd of
Dry
Air
Relative Humidity
Abs
olut
e H
umid
ity (H
umid
ity R
atio
)
Poun
ds o
f Moi
stur
e Pe
r Pou
nd o
f Dry
Air
Temperature oF
0%
20%
40%
15
25
30
35
45
50
.002
.004
.006
.008
.010
.012
.014
.016
.018
.020
.022
.024
.026
.028
Cooling Heating
40
20
100% 60
%
More Latent Heat
More Sensible Heat
Less Latent Heat
No Change in Total Heat
No Change in Total Heat
Less Sensible Heat
Dehumidificatio
n
35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
P
Psychrometric processesheating and coolingdew-point then condensation(de)humidification (adiabatic)enthalpy increase
Image by MIT OCW.
Feeling comfortable
0 1 2 3
Température de l'air
mpérature des surfaces
Courants d'air
Rayonnement solaire
Humidité de l'air
Pureté de l'air
Eclairage
Couleur
BruitsNoise
Color
Lighting
Air purity
Air humidity
Solar radiation
Drafts
Surfaces temperature
Air temperature
0 1 2 3
Température de l'air
mpérature des surfaces
Courants d'air
Rayonnement solaire
Humidité de l'air
Pureté de l'air
Eclairage
Couleur
BruitsNoise
Color
Lighting
Air purity
Air humidity
Solar radiation
Drafts
Surfaces temperature
Air temperature
Factors of thermal comfortAir temperature (sensitive to ΔT > 1°C)
180
160
140
120
100
80
60
40
20
10 12 14 16 18 20 22 24 26 28 30 32 34 360
Hea
t flu
x (W
)
Radiation
Conduction
Convection
Evaporation
Temperature (oC)
Image by MIT OCW.
Factors of thermal comfort
Air temperature
ΔT between air and building surfaces (MRT) (keep < 3°C)
Image by MIT OCW.
Direct Sunlight Glare
Direct Sunlight Thermal Discomfort
Radiant Energy Exchange
Cold Drafts
Factors of thermal comfortAir temperature
ΔT between air and building surfaces (MRT)
Air movement (keep < 1.5 m/s unless overheated)
Image by MIT OCW.
Factors of thermal comfort
Air temperature
ΔT between air and building surfaces (MRT)
Air movement
Relative humidity(30% to 65%)
Comfort zoneStandard Effective Temperature (SET)
SET isotherms on psychrometric chart
neutral temperature Tn = 17.6 + 0.31 x Tmonth (±2.5°C for comfort)
DBT ( C)o 5 10 15 20 25 30
30
25
20
15
10
5
35 40 45 50
70
65
75
80
85
AH
HOT ANDHUMID
HOT ANDDRY
DRY
COMFORTZONE
6055
5045
4035
COLD AND DRY
COLD ANDHUMID
100 %
Image by MIT OCW.
Comfort zoneStandard Effective Temperature (SET)
SET isotherms on psychrometric chartneutral temperature Tn = 17.6 + 0.31 x Tmonth (±2.5°C for comfort)comfort zone depends on climate
Darwin
Budapest-10
-10
0oC 10
10
20
20
30
30
40 50
0oC 10
10
20
20
30
30
40 50
g/kg
g/kg
0
0
15
11.5
108.5
g/kg
5
050403020
22.3 24.8 27.3 C
40%
30%
20%
10%
°
ET
·40
SET35
·
SET
·30ET
·25
ET
·20
Images by MIT OCW.
Comfort zoneStandard Effective Temperature (SET)
SET isotherms on psychrometric chartneutral temperature Tn = 17.6 + 0.31 x Tmonth (±2.5°C for comfort)comfort zone depends on climate
35
4550
40
Temperature oF35 40 45 50 55
55
60
60
65
65
70
70
75 80
80
85
85
90
75
95 100 105 110
Abs
olut
e H
umid
ity (H
umid
ity R
atio
)Po
unds
of M
oist
ure
Per P
ound
of D
ry A
ir
20%
40%
.002
.004
.006
.008
.010
.012
.014
.016
.018
.020
.022
.024
.026
.028
80%10
0%
WIN
TER
68 oF WET BULB64 oF WET BULB
Relative Humidity
0%
60%
SUM
MER
Image by MIT OCW.
Comfort zoneStandard Effective Temperature (SET)
SET isotherms on psychrometric chartneutral temperature Tn = 17.6 + 0.31 x Tmonth (±2.5°C for comfort)comfort zone depends on climateshift with MRT and air movement
35
4550
40
Temperature oF35 40 45 50 55
55
60
60
65
65
70
70
75 80
80
85
85
90 95 100 105 110
Abs
olut
e H
umid
ity (H
umid
ity R
atio
)Po
unds
of M
oist
ure
Per P
ound
of D
ry A
ir
20%
40%
.002
.004
.006
.008
.010
.012
.014
.016
.018
.020
.022
.024
.026
.028
80%10
0%
35
4550
40
60%
Temperature oF35 40 45 50 55
55
60
60
65
65
70
70
75 80
80
85
85
90 95 100 105 110
Abs
olut
e H
umid
ity (H
umid
ity R
atio
)
20%
40%
.002
.004
.006
.008
.010
.012
.014
.016
.018
.020
.022
.024
.026
.028
80%10
0%
Original Location
75 75
Original Location
Relative Humidity Relative Humidity
10% 10%
60%
Image by MIT OCW.