Chapter 1 Liquid Cooling Systems

CHAPTER 1 LIQUID COOLING SYSTEMS Liquid cooling systems are vital to the proper operation of shipboard electronic equipment. Because of their importance, these cooling systems must be reliable and readily available. Study the contents of this chapter carefully. The knowledge you acquire may one day help you prevent heat damage to a multimillion dollar piece of equipment and the loss of countless manhours being expended in its repair. Imagine how you would feel if the damage occurred because you had not checked a temperature gauge at a particular time because you were not aware of its purpose or existence. Knowledge of the equipment is one of the greatest safeguards that you can develop. Let us begin by discussing the methods for cooling electronic equipments and systems. ELECTRONIC EQUIPMENT COOLING METHODS Most electronic equipment generates sufficient heat so that some form of equipment cooling is required during normal operation. Heat is generated by various parts of the equipment because electrical energy is dissipated in the form of heat whenever current flows through a resistance. This heat must be removed to prevent a change in the equipment’s operating parameters and to prevent possible breakdown of electronic parts. This section on liquid cooling systems describes some of the more common methods of heat removal from electronic equipment. It provides the basic knowledge necessary for better understanding of the major components, operation, and maintenance of a typical cooling system. Our discussion will highlight four methods of cooling: convection, forced-air, air-to-air, and air-to-liquid. CONVECTION COOLING Cooling by the convection principle is shown in figure 1-1. As the heat of an equipment part warms the air in its vicinity, the warm air, being lighter, rises through the outlet openings. The cooler air is drawn in through the inlet openings to replace the warm air. This method is limited in its cooling effect because it relies Figure 1-1.-Convection cooling. upon the natural airflow and requires that the equipment enclosure be of open construction without air falters. To increase heat dissipation, a finned heat sink can be added to the heat-producing part, as shown in figure 1-2. The fins increase the effective surface area of the part, allowing more heat to be transferred to the air. For the maximum transfer of heat, the part must make contact with the heat sink. Silicone grease is usually applied between the heat source and heat sink for better thermotransfer. The heat sink must be kept free of any dirt or dust, which would act as an insulator. Figure 1-2.—Finned best sink. 1-1