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Humid Air. Water vapor in air. Trace Glasses 1% Argon (A) Water vapor (H 2

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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)

(2)

Humid Air



Water vapor in air

ƒ saturation humidity (SH) (= max AH)

ƒ moisture content (absolute humidity AH) = kgvapor / kgdry air

ƒ (partial) vapor pressure [Pa]

ƒ relative humidity (RH)

ƒ wet-and-dry bulb psychrometer GAZE

ETHER

(3)

Humid Air



Water vapor in air

ƒ saturation humidity (SH) (= max AH)

ƒ moisture content (absolute humidity AH) = kgvapor / kgdry air

ƒ (partial) vapor pressure [Pa]

ƒ relative humidity (RH) in [%]

ƒ wet-and-dry bulb psychrometer

ƒ enthalpy (H) in [kJ/kg]

­ Sensible heat vs. Latent heat

(4)

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 line

Dry bulb temperature ( C)o

Dry bulb temperature ( C)o

40% 20% 60% 80% Wet bulb temperatur e( o C) ƒ relative humidity RH

ƒ wet bulb temperature

ƒ enthalpy

ƒ specific volume



Psychrometric chart

ƒ absolute humidity AH and saturation line

(5)

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

ƒ heating and cooling

ƒ dew-point then condensation

ƒ (de)humidification (adiabatic)

ƒ enthalpy increase

(6)

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

(7)

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)

(8)

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

(9)

Factors of thermal comfort



Air temperature



ΔT between air and building surfaces (MRT)



Air movement

(keep < 1.5 m/s unless overheated)

(10)

Factors of thermal comfort



Air temperature



ΔT between air and building surfaces (MRT)



Air movement



Relative humidity

(11)

Comfort zone



Standard Effective Temperature (SET)

ƒ SET isotherms on psychrometric chart

ƒ 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 %

(12)

Comfort zone



Standard Effective Temperature (SET)

ƒ SET isotherms on psychrometric chart

ƒ neutral temperature Tn = 17.6 + 0.31 x Tmonth (±2.5°C for comfort)

ƒ 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

(13)

Comfort zone



Standard Effective Temperature (SET)

ƒ SET isotherms on psychrometric chart

ƒ neutral temperature Tn = 17.6 + 0.31 x Tmonth (±2.5°C for comfort)

ƒ 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

(14)

Comfort zone



Standard Effective Temperature (SET)

ƒ SET isotherms on psychrometric chart

ƒ neutral temperature Tn = 17.6 + 0.31 x Tmonth (±2.5°C for comfort)

ƒ comfort zone depends on climate

ƒ 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%

(15)

Humid Air, Thermal Comfort



Reading assignment from Textbook:

ƒ “Introduction to Architectural Science” by Szokolay: § 1.1.3 +

§ 1.2



Additional readings relevant to lecture topics:

ƒ "How Buildings Work" by Allen: Chap 7 + pp. 58 - 60 in Chap 8

References

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