Thursday 11 May 2023 20:52
Thermodynamic wet bulb temp • Associated with moisture content of air
(aka adiabatic saturation temp) • For moist air, a temp T* exists. @ which liquid water, if e
(T*): bring it to saturation @ that temp (T*) and total pressure
• Temp @ which water, by evaporating into air, can adiaba
saturation @ the same (water) temperature
Psychometric wet bulb temp • The diff btwn T* & Twb is the error:
(Twb):
Sling psychrometer use • To measure thermodynamic wet-bulb temp/adiabatic sa
• It directly measures the dry-bulb temp (T) and psychrom
( which approximates the thermodynamic wet-bulb temp
Dewpoint temp (Tdp): • Temp of saturated vapour at the same partial pressure a
moist air
(Temp @ which water vapour starts to condense in the a
becomes completely saturated,
Above this temp the moisture stays in the air)
Dry bulb temp (Tdb) • Ambient temperature of the air
(air temp) • Temp is indicated by a thermometer that is NOT affected
Wet bulb temp (Twb) • Measured using a thermometer with the bulb wrapped i
(adiabatic) • Lower than the dry bulb temp
• Always btwn the dry bulb temp & dew point
• Temp @ which water, by evaporating into the air, can ad
saturation @ the same (water) temp
Relative humidity (𝝓) Ratio of the mole fraction of water vapour (yv) to the mole
(yv,sat) in a saturated moist air sample at the same mixture
Humidity ratio (𝝎) Ratio of mass of water vapour to the mass of dry air
Thermodynamic wet bulb temp • Associated with moisture content of air
(aka adiabatic saturation temp) • For moist air, a temp T* exists. @ which liquid water, if e
(T*): bring it to saturation @ that temp (T*) and total pressure
• Temp @ which water, by evaporating into air, can adiaba
saturation @ the same (water) temperature
Psychometric wet bulb temp • The diff btwn T* & Twb is the error:
(Twb):
Sling psychrometer use • To measure thermodynamic wet-bulb temp/adiabatic sa
• It directly measures the dry-bulb temp (T) and psychrom
( which approximates the thermodynamic wet-bulb temp
Dewpoint temp (Tdp): • Temp of saturated vapour at the same partial pressure a
moist air
(Temp @ which water vapour starts to condense in the a
becomes completely saturated,
Above this temp the moisture stays in the air)
Dry bulb temp (Tdb) • Ambient temperature of the air
(air temp) • Temp is indicated by a thermometer that is NOT affected
Wet bulb temp (Twb) • Measured using a thermometer with the bulb wrapped i
(adiabatic) • Lower than the dry bulb temp
• Always btwn the dry bulb temp & dew point
• Temp @ which water, by evaporating into the air, can ad
saturation @ the same (water) temp
Relative humidity (𝝓) Ratio of the mole fraction of water vapour (yv) to the mole
(yv,sat) in a saturated moist air sample at the same mixture
Humidity ratio (𝝎) Ratio of mass of water vapour to the mass of dry air
