Humid Air
Water vapor in air
Nitrogen 78% Oxygen 21% Trace Glasses 1% Argon (A) Water vapor (H2O)
Carbon dioxide (CO2)
Neon (Ne) Helium (He) Krypton (Kr) Hydrogen (H)
Ozone (O3)
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
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 psychrometer
enthalpy (H) in [kJ/kg]
Sensible heat vs. Latent heat
Humid Air
(kJ/kg) P (kJ/kg) Absolut e hu m idi ty (g/kg) 15 5 25 30 30 30 40 50 60 70 80 90 100 0.800 0.8 25 0.8 50 0.8 75 0.900 0.925 0.9 50 (m 3/kg) 110 120 130 28 100% 20 20 20 24 20 16 12 8 4 0 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 Saturation lineDry bulb temperature ( C)o
Dry bulb temperature ( C)o
40% 20% 60% 80% Wet bulb temperatur e( o C) relative humidity RH
wet bulb temperature
enthalpy
specific volume
Psychrometric chart
absolute humidity AH and saturation line
Humid Air
Temperature Increase (Vapor to Liquid) or Decrease (Liquid Vapor)
P M oi st ur e re m ov ed b y so rb en t o r a dd ed b y ev ap or at io n
Dew Point Temperature Dew Point A m ou nt o f c on de ns at io n H um id ity In cr ea se L at en t H ea t C on te nt In cr ea se Total Heat (Enth alpy) BTU Per P ound of D ry Ai r Relative Humidity A bs ol ut e H um id ity (H um id ity R at io ) Po un ds o f M oi st ur e Pe r P ou nd o f D ry A ir TemperatureoF 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 Dehum idificatio
n
35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
P
Psychrometric processes
heating and cooling
dew-point then condensation
(de)humidification (adiabatic)
enthalpy increase
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 Bruits Noise 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 Bruits Noise Color Lighting Air purity Air humidity Solar radiation Drafts Surfaces temperature Air temperature
Factors of thermal comfort
Air 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 36 0
Heat flux (W) Radiation
Conduction Convection Evaporation
Temperature (oC)
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
Factors of thermal comfort
Air temperature
ΔT between air and building surfaces (MRT)
Air movement
(keep < 1.5 m/s unless overheated)
Factors of thermal comfort
Air temperature
ΔT between air and building surfaces (MRT)
Air movement
Relative humidity
Comfort zone
Standard 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 AND HUMID HOT AND DRY DRY COMFORT ZONE 60 55 50 45 40 35 COLD AND DRY COLD AND HUMID 100 %
Comfort zone
Standard Effective Temperature (SET)
SET isotherms on psychrometric chart
neutral 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 10 8.5 g/kg 5 0 50 40 30 20 22.3 24.8 27.3 C 40% 30% 20% 10% ° ET ·40 SET 35· SET ·30 ET ·25 ET ·20
Comfort zone
Standard Effective Temperature (SET)
SET isotherms on psychrometric chart
neutral temperature Tn = 17.6 + 0.31 x Tmonth (±2.5°C for comfort)
comfort zone depends on climate
35 45 50 40 Temperature oF 35 40 45 50 55 55 60 60 65 65 70 70 75 80 80 85 85 90 75 95 100 105 110
Absolute Humidity (Humidity Ratio)
Pounds of Moisture Per Pound of Dry
Air 20% 40% .002 .004 .006 .008 .010 .012 .014 .016 .018 .020 .022 .024 .026 .028 80% 100% WINTER 68 oF WET BULB 64o F WET BU LB Relative Humidity 0% 60% SUMMER
Comfort zone
Standard Effective Temperature (SET)
SET isotherms on psychrometric chart
neutral temperature Tn = 17.6 + 0.31 x Tmonth (±2.5°C for comfort)
comfort zone depends on climate
shift with MRT and air movement
35 45 50 40 Temperature oF 35 40 45 50 55 55 60 60 65 65 70 70 75 80 80 85 85 90 95 100 105 110
Absolute Humidity (Humidity Ratio) Pounds of Moisture Per Pound of Dry
Air 20% 40% .002 .004 .006 .008 .010 .012 .014 .016 .018 .020 .022 .024 .026 .028 80% 100% 35 45 50 40 60% Temperature oF 35 40 45 50 55 55 60 60 65 65 70 70 75 80 80 85 85 90 95 100 105 110
Absolute Humidity (Humidity Ratio)
20% 40% .002 .004 .006 .008 .010 .012 .014 .016 .018 .020 .022 .024 .026 .028 80% 100% Original Location 75 75 Original Location
Relative Humidity Relative Humidity
10% 10%
60%
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