TYPE I LIQUID-COOLING SYSTEM
The type I liquid-cooling system is a seawater/
distilled-water (SW/DW) heat exchanger with an SW/
DW heat exchanger standby. This system is used for
electronic system installations that can be operated
satisfactorily with seawater temperature as high as
95°F, which should result in a distilled-water supply
temperature to the electronics of approximately
104°F. Refer to figure 2-1 as you study this section.
Starting with the distilled-water pumps, distilled
water under pressure flows to the temperature-regu-
lating valve. The temperature-regulating valve is in-
stalled to partially bypass distilled water around the
seawater-to-distilled-water heat exchanger so that a
constant water temperature can be supplied to the
electronic equipment. As the temperature in the dis-
tilled water increases, more water is directed to the
heat exchanger and less to the bypass line, thus main-
taining the output water temperature constant.
The standby heat exchanger is usually of the same
design and is used when the on-line heat exchanger is
inoperable or is undergoing maintenance. The size of
the heat exchanger is designed to handle the full
cooling load of the electronic equipment plus a 20-
percent margin. From the heat exchanger, the water
then goes through various monitoring devices, which
check the water temperature and flow.
The water temperature and flow depend on the re-
quirements of the electronic equipment being cooled.
After the water moves through the equipment, it is
drawn back to the pump on the suction side; thus, a
continuous flow of coolant is maintained in a closed-
loop system.
An expansion tank in the distilled-water system
compensates for changes in the coolant volume and
provides a source of makeup water in the event of a
secondary system leak. When the expansion tank is
located above the highest point in the secondary
system and vented to the atmosphere, it is called a
gravity tank. If it is below the highest point in the
secondary cooling system, it is called a conpression
tank because it requires an air charge on the tank for
proper operation.
The demineralizer is designed to remove dissolved
metals, carbon dioxide, and oxygen. In addition, a
submicron filter (less than one-millionth of a meter)
is installed at the output of the demineralizer to pre-
vent the carry-over of chemicals into the system and
to remove existing solids.
TYPE II LIQUID-COOLING SYSTEM
The type II liquid-cooling system is an SW/DW
heat exchanger with a chilled-water/distilled-water
(CW/DW) heat exchanger standby. This system is
used in installations that cannot accept a DW tempera-
ture higher than 90°F. Refer to figure 2-2 as you
study this section.
The secondary cooling system of the type II
liquid-cooling system is similar to that of the type I
secondary liquid-cooling system and uses many of the
same components—the major difference is in the
operation of the CW/DW heat exchanger. The second-
ary coolant is in series with the SW/DW heat ex-
changer and automatically supplements the cooling
operation when the SW/D Wheat exchanger is unable
to lower the temperature of the distilled water to the
normal operating temperature.
The CW/DW temperature-regulating valve allows
more chilled water to flow into the primary cooling
system to the CW/DW heat exchanger. This causes
the temperature in the secondary system to go down.
Normally, this action occurs only if high seawater
temperatures are encountered in tropical waters. The
CW/DW heat exchanger is also used in an SW/DW
heat exchanger malfunction.
TYPE III LIQUID-COOLING SYSTEM
The type III liquid-cooling system is a CW/DW
heat exchanger with a CW/DW heat exchanger stand-
by, and is used in installations where the temperature
range is critical. It requires close regulation of the DW
coolant to maintain temperatures between established
limits. For example, the temperature limits might be
between 70°F and 76°F. This system is used where
tighter control is required. Refer to figure 2-3 as you
study this section.
2-5
