The seawater system shown in figure 2-1 is a
multiple-branch system. As such, it supplies a number
of heat exchangers for other electronic equipment. To
regulate the proper amount of seawater to each cool-
ing system, an orifice plate is installed in the line
between each heat exchanger and the duplex strainer.
The heat exchangers are referred to as seawater-to-
distilled-water heat exchangers.
Another means of providing seawater is through
the ship’s fire main, as shown in figure 2-2. The sea-
water is taken from the fire main through a duplex
strainer and a flow regulator (orifice plate) to and
through the heat exchanger. It is then discharged
overboard. The connection to the fire main is perma-
nent.
The ship’s fire pump, not shown in figure 2-3, is
used to pump seawater into the fire main. The fire
pump is similar in design to the previously mentioned
seawater circulating pump, except it has a much larger
capacity.
Another means of obtaining seawater as a primary
coolant for types I and II liquid-cooling systems is by
an emergency connection, which is used if the normal
seawater supply is lost. The connection is usually by
means of a 1 1/2-inch fire hose. The emergency supply
comes from an alternate portion of the ship’s fire main
or a portable pump rigged by the ship’s damage con-
trol party. The portable emergency hose is normally
stored in the liquid-coolant machinery room.
In types II and III liquid-cooling systems, chilled
water is taken from the supply main of the air-
conditioning, chilled-water systems. The chilled water
is used as a backup source of cooling water for the
primary cooling system shown in figure 2-2, and as a
normal and backup source for the system shown in
figure 2-3. The chilled water flows through the tubes
of the heat exchanger (chilled water to distilled
water), a flow regulator, and back to the chilled-water
system. A temperature-regulating valve at the inlet of
the heat exchanger regulates the flow of chilled water
through the heat exchanger to maintain the required
water temperature in the secondary system (distilled
water).
The ship’s air-conditioning, chilled-water circu-
lating pump is used to pump the chilled water through
the heat exchanger. The chilled-water system is a
closed-loop water system because the water is recir-
culated. The system must be kept tight and free from
leaks to ensure satisfactory operation.
SECONDARY LIQUID-COOLING SYSTEM
The secondary liquid-cooling system transfers
heat from the electronic equipment being cooled to
the primary cooling system. The coolant normally
used in the secondary system is distilled water, which
is ultrapure and is maintained in that state by a de-
mineralize. In some secondary systems, ethylene
glycol is added to the water to prevent freezing when
the system is exposed to freezing weather.
The secondary liquid-cooling system is usually
comprised of a distilled-water circulating pump, a
compression or gravity-feed expansion tank, the elec-
tronic equipment being cooled, a demineralizer, a
temperature-control valve, the monitoring equipment
with its associated alarms, and the heat exchanger,
which is shared with the primary system. The second-
ary system is a closed-loop water system, as compared
to the seawater system, which is a one-pass, or
open-loop, system.
LIQUID-COOLING SYSTEM
CONFIGURATIONS
The U.S. Navy uses three basic configurations of
liquid-cooling systems, and you could be involved
with all three of them, depending on the number and
types of electronic equipment to be cooled. The speci-
fications for the type of system installed on your
equipment will depend on the operational require-
ments of the equipment. Some electronic equipments
require very close regulation of the temperature of the
distilled water, whereas others do not.
2-4
