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.

Humid Air, Thermal Comfort

Reading assignment from Textbook:“Introduction to Architectural Science” by Szokolay: § 1.1.3 + § 1.2

Additional readings relevant to lecture topics:"How Buildings Work" by Allen: Chap 7 + pp. 58 - 60 in Chap 8

"Heating Cooling Lighting" by Lechner: Chap 4