PRIMARY COOLING SYSTEM

result in a distilled water supply temperature to the electronics of approximately 104°F. Type II (SW/DW, CW/DW) systems are used in installations that cannot accept a DW temperature higher than 90°F. Type III (CW/DW) systems are used in installations where the temperature range is critical. They require close regulation of the DW coolant to maintain temperatures between established limits. For example, the temperature limits might be 70°F and 76°F. As you can see, Type III systems are used where tighter control is required. Liquid cooling systems are composed of piping, valves, regulators, heat exchangers, strainers, circulating pumps, expansion tanks, gauges, and a demineralize. In some systems, there are specialized components to monitor cooling water to the electronic equipment. Let’s examine this in greater detail by discussing the operation of the three types of liquid cooling systems. Before doing so, however, let’s look at the systems in terms of primary and secondary systems. PRIMARY COOLING SYSTEM The cooling water for the primary cooling system is either seawater or chilled water. The seawater, obviously, is from the sea and the chilled water is from the ship’s air-conditioning plant. Figures 1-6,1-7, and 1-8 show the basic arrangements of systems using seawater and chilled water. In figure 1-6, seawater from a sea connection is pumped by a seawater circulating pump in one of the ship’s engineering spaces through a duplex strainer to remove all debris and then through the tubes of a heat exchanger. Finally, it is discharged back into the sea at an overboard discharge. The seawater system shown in figure 1-6 is a multiple-branch system. As such, it supplies a number of heat exchangers for electronic equipment. To regulate the proper amount of seawater to each cooling 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 firemain, as shown in figure 1-7. The seawater is Figure 1-7.—Type II liquid cooling system. 1-5