2 - 397
7. SYSTEM DESIGN GUIDE
DATA G10
HEAT SOURCE UNITS
WY
2) Cooling tower
a) Types of cooling tower
Types of cooling towers
The cooling towers presently used include the open
type cooling tower, open type cooling tower + heat ex-
changer, closed type cooling tower, and air-cooled type
cooling tower. However, as the quality control of circula-
tion water is essential when units are installed in decen-
tralized state inside a building, the closed type cooling
tower is generally employed in such case.
Although the circulation water will not be contaminated
by atmospheric air, it is recommended to periodically
blow water inside the system and replenish fresh water
instead.
In a district where the coil may be frozen in the winter, it
is necessary to apply antifreeze solution to the circula-
tion water, or take freeze protection measures such as
to automatically discharge water inside the cooling coil
at the stopping of the pump.
When the open type cooling tower is used, be sure to
install a water quality control device in addition to the
freeze protection measures, as the water may be deter-
iorated by atmospheric contaminants entered into the
cooling tower and dissolved into the circulation water.
b) Calculation method of cooling tower capacity
All units of the water heat source CITY MULTI may pos-
sibly be in cooling operation temporarily (at pulling
down) in the summer, however, it is not necessary to
determine the capacity according to the total cooling ca-
pacity of all CITY MULTI units as this system has a
wide operating water temperature range (10~45°C)
[50~113°F].
It is determined in accordance with the value obtained
by adding the maximum cooling load of an actual build-
ing, the input heat equivalent value of all CITY MULTI
units, and the cooling load of the circulating pumps.
Please check for the values of the cooling water volume
and circulation water volume.
Closed type
Air-cooled type
Cooling tower capacity = (Refrigeration ton)
Qc
:
Maximum cooling load under actual state
(kcal/h)
Qw
:
Total input of water heat source CITY MULTI at simultaneous operation under
maximum state
(kW)
Pw
:
Shaft power of circulation pumps
(kW)
Qc + 860 x (
S
Qw + Pw)
3,900
Cooling tower capacity = (Refrigeration ton)
Qc
:
Maximum cooling load under actual state
(BTU/h)
Qw
:
Total input of water heat source CITY MULTI at simultaneous operation under
maximum state
(kW)
Pw
:
Shaft power of circulation pumps
(kW)
*
1 Refrigerant ton of cooling tower capacity
»
US refrigerant ton x (1+0.3)
= 3,900 kcal/h = 15,500 BTU/h
Qc + 3,412 x (
S
Qw + Pw)
15,500
