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TRG-TRC005-EN 9
period two
Condensers
notes
A cooling tower is a device commonly used to cool condensing water. In this
design, warm water is sprayed over the fill inside the cooling tower while a
propeller fan draws outdoor air upward through the fill. The movement of air
through the spray causes some of the water to evaporate, a process that cools
the remaining water. This cooled water then falls to the tower sump to be
returned to the condenser.
The final temperature of the water leaving the tower is determined, in part, by
the humidity of the outdoor air. If the outdoor air is dry, the final water
temperature can be considerably lower than the ambient dry-bulb temperature.
If the outdoor air is humid, however, the final temperature will be near the
ambient dry-bulb temperature.
While a cooling tower can reclaim much of the condensing water, it cannot
reclaim it all. The evaporation process uses up water to dissipate heat
contributed by the cooling load plus the heat of compression. In addition, as the
water evaporates, the dissolved minerals and water treatment chemicals
become concentrated in the sump. To prevent this solution from becoming
concentrated and possibly corrosive, water is periodically bled from the sump
and an equal amount of fresh water is added.
In the past, some water-cooled condensers used water from either a municipal
or a natural water supply as the condensing water. After rejecting the
condenser heat to this water, it was dumped into the sewer or back into the
body of water. Environmental and economic restrictions have made this
method uncommon.
Finally, a geothermal well system can be used to reject the heat from the
condenser by circulating the condensing water through a series of
underground pipes . This method takes advantage of the naturally-cool ground
temperatures.
Cooling Tower
sprays
sprays
from
from
condenser
condenser
to
to
condenser
condenser
sump
sump
propeller
propeller
fan
fan
outdoor
outdoor
air
air
85ºF
85ºF
[29ºC]
[29ºC]
95ºF
95ºF
[35ºC]
[35ºC]
fill
fill
Figure 14