FINALS Flashcards
Study of the properties of mixture of air and water vapor
Psychometry
Mixture of air and water vapor
Atmospheric air
Atmospheric air with all the water vapor (and contaminants) removed
Dry air
Binary (two-component) mixture of dry air and water vapor
Moist air
a state of neutral equilibrium between moist air and the condensed water phase (liquid or
solid
measure of the capacity of air to absorb moisture
Relative humidity, %
the ratio of the mole fraction of water vapor xw in moist air to the mole fraction of water
vapor xws in saturated air at the same temperature and pressure
Relative humidity, %
the moisture content or mixing ratio of a given moist air sample
Humidity ratio W
ratio of the mass of water vapor to the mass of dry air in a given air-vapor mixture
Humidity ratio W
Eq of humidity ratio
…
the temperature of the air as measured by an ordinary dry bulb thermometer, or by using
some other temperature sensing device
Dry-bulb temperature Tdb -
the temperature at which water (liquid or solid), by evaporating into moist air at dry
bulb temperature Tdb and humidity ratio W, can bring air to saturation adiabatically at the
same temperature t* while total pressure p is constant
Thermodynamic wet-bulb temperature t*
Unique property of a given moist air sample independent of
measurement techniques
Thermodynamic wet-bulb temperature t*
approximated, dependent on other factors: distilled water, air movement, shield, cotton/cloth used
Psychrometric wet-bulb temperature Twb
equilibrium temp reached when the wet bulb is placed in an
airstream and water evaporates
Psychrometric wet-bulb temperature Twb
difference between dry-bulb and wet-bulb temperatures
Wet-bulb depression
depends on the degree of “dryness or wetness” of the air
Wet-bulb depression
the temperature of moist air saturated at pressure p, with the same humidity ratio W
as that of the given sample of moist air
Dew-point temperature Td
the temperature at which the vapor in the air begins to condense
Dew-point temperature Td
can be obtained by cooling the air-vapor mixture under constant pressure
Dew-point temperature Td
the sum of the individual partial enthalpies of the components (air and water
Enthalpy of air-vapor mixture
specific volume v of a moist air mixture
v = V/Ma = V/(28.966na)
Graphical representation of the thermodynamic properties of moist air
Psychrometric Chart
straight, not precisely parallel to each other, and inclined slightly from the vertical
position
Dry-bulb temperature lines
25.
oblique and in a slightly different direction from enthalpy lines not precisely parallel to
enthalpy line
Thermodynamic wet-bulb temperature lines
26.
straight but are not precisely parallel to each other
Specific volume lines
30.
When moist air is heated or cooled without a gain or loss of moisture
Sensible heating
When moist air is cooled without a gain or loss of moisture
Sensible cooling
Water vapor is added to moist air
Humidification
Water vapor is absorbed from the moist air
. Dehumidification
occurs when moist air is cooled to a temperature below its initial
Moisture condensation
Cooling and Dehumidificatio
tendency for moisture to permeate through the wall due to pressure difference until
pressure equalizes
Moisture transmission
Material used to install on, or near, the warm or humid Side of an enclosed structure.
Vapor barriers
a high-quality non-combustible bonded Rockwool with a vertical fiber structure, w/c
ensures a high insulation value, excellent fire resistance and
Mineral fiber
water repellent - free of (H)CFCs
- fully recyclable solution for wall and ceiling applications in hygienic chill and ambient
environments where internal temperatures
Rockwool -
Polyisocyanurate (PIR)
- the most efficient insulating materials available
