Firstly projecting a line horizontally to the right from our point, we can read off from the Y axis that the air has a moisture content of 0.0078 kg/kg i.e. there is 0.0078 kg of water vapour in every 1.0 kg of dry air.
Drawing a line through our point parallel to the lines of specific volume allows us to determine that the specific volume of the air is 0.844 m3/kg (nearly half way between 0.84 and 0.85). This tells us that every kg of air has a volume of 0.844 m3. Specific volume is 1/density so the density of the air can be found by taking the reciprocal of the specific volume.
Density = 1/specific volume,
In our example: Density = 1/0.844 = 1.184 kg/ m3.
Drawing a line parallel to the wet bulb lines through our point will give the Wet Bulb (wb) temperature. In our example this is between the 14.0C and 15.0C lines and is approximately 14.7C wb.
Temperature db = 21.0 C
Humidity = 50% RH
Moisture Content = 0.0078 kg/kg
Specific Volume = 0.844 m3/kg
Temperature wb = 14.7 C
Specific enthalpy = 41.0 kJ/kg
The next post will look at what happens when the air is heated.