147
8. SYSTEM DESIGN GUIDE
HEAT SOURCE
WR2
MEE15K036
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 exchanger,
closed type cooling tower, and air-cooled type cooling
tower. However, as the quality control of circulation water
is essential when units are installed in decentralized 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 circulation
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
deteriorated 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 possibly 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 capacity of all CITY
MULTI units as this system has a wide operating water temperature range.
It is determined in accordance with the value obtained by adding the maximum cooling load of an actual building, 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 × (ƩQw + 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 × (1 + 0.3)
= 3,900 kcal/h = 15,500 BTU/h
Qc + 3,412 × (ƩQw + Pw)
15,500
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