Importance of Wet Bulb Temperature(WBT) in Cooling Tower
Wet bulb temperature(WBT) - Temperature measured by a wet
bulb thermometer. If the bulb of a thermometer is wetted by muslin and the
evaporation of moisture by a moving air with minimum velocity 5 mtr/sec, then
the temperature recorded by the thermometer by the thermometer is WBT.
A wet bulb temperature measurements taken within 1.5 m of
the air inlets of cooling tower and between 1.5 m and 2.0 m above the basin
elevation of the cooling tower.
Approach - Difference between cooling water return
temperature and the inlet wet bulb temperature of air. The minimum reasonable
possible approach temperature is 2 Degree C, however 4 Degree C to 6 Degree C
is more used by the industries.
The wet bulb temperature of the entering air has a very
important for the performance of cooling tower. A lower wet bulb temperature
produces a lower cooling water temperature.
For a given air wet bulb temperature, the cooling water
return temperature has a significant effect on size of cooling tower. To cool water
nearer to the wet bulb temperature of the air would require an extremely large
size cooling tower. If we try to design cooling tower nearer to the air wet
bulb temperature the tower size increases very speedily.
