Dehumidification:

When a moist air steam is cooled at constant mixture pressure to a temperature below its dew point temperature, some condensation of water vapour would occur. Refer to fugure 36.4 for understanding the process.

Figure 36.4

Dehumidification of air-water vapour mixture can be achieved by cooling the mixture below its dew point temperature (path i-A-B) allowing some water to condense, and then heating the mixture (path B-f) to the desired temperature.

Dehumidification and Cooling

For cooling the mixture, the mixture can be made to pass over the cooling coils through which a cold refrigerant is circulated (Figure 36.5)..

In some commercial air-conditioning plants, chilled water (below the dew point temperature of the mixture) is sprayed into the air to be dehumidified. Then the air leaves with less humidity at the temperature of the chilled water. Next the air is heated to the desired temperature (figure36.6)

Figure 36.6

These two cooling and heating processes constitute an air conditioning plant.