This is about Psychrometry basics.

1. BY
AMULYA .Y

2. Definitions
 Psychrometrics: Psychrometrics is the science of moist
air properties and processes.
 Psycrometry: It is the study of properties of mixture of
air and water vapour.
 Air contains Nitrogen,Oxygen,Carbon dioxide and
small amount of some other gases.
 Atmospheric Air: Atmospheric air contains mixture of
air, water vapour and some dust particles.
 Dry air: Air with no water vapour.

3.  Moist Air: Contains mixture of air and water vapour.
 Saturated Air: If air contains maximum water vapour
then it is called saturated air.
 Moisture: The amount of water vapour present in air in
liquid phase.
 Humidity: The amount of water vapour present in air
in gaseous state.
 Hygrometer is the device used to measure humidity or
the amount of water vapour in the air.

4.  Dry bulb temperature: It is the temperature of moist
air measured using standard thermometer.
 Saturated vapour pressure: Saturated partial pressure
of water vapour at dry bulb temperature.
 Wet bulb temperature: It is the temperature recorded
when the bulb of thermometer is covered with wet
cloth.

5.  Relative Humidity: Relative humidity is the ratio of
amount of water vapour the air can hold to the total
amount of water vapour the air holds. It is denoted by
φ.
 φ=0 dry air
 φ= 1 saturated air
 Humidity ratio: The ratio of water vapour present in
1kg of dry air. It is represented by W.
 Vapour pressure: It is the pressure of water vapour
which would exert if it exists alone at same
temperature and volume of atmospheric air.

6.  Specific humidity: The amount of water vapour
present in dry air. Also called as humidity ratio.
 Dew point temperature: The temperature at which the
moist starts to condense. Also known as saturated
temperature.
 Enthalpy: It is the heat content of a system. Enthalpy
of moist air is sum of enthalpies of dry air and water
vapour. It is represented by h

7.  Adiabatic saturation temperature: The temperature at
which water gets evaporated and bring the air to
saturation at same temperature.
 Degree of saturation: The ratio of humidity ratio to the
humidity ratio of saturated mixture at same pressure
and temperature. It is denoted by µ.

8. Psychrometric chart
 Psychrometric chart is the graphical representation of
psychrometric processes such as physical and
thermodynamic properties of air and water vapour.
 These include dry bulb and wet bulb temperatures,
relative humidity,enthalpy,dew point temperature.

10. THANK YOU