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Part 1, Refrigeration
 

1
GENERAL INTRODUCTION
 
A. PURPOSES AND NEED
 
1A1. General. In many respects, the United States Submarine Service is the most exacting of all the services in our armed forces. The physical requirements for its personnel are of necessity rigid. In order to maintain these high physical standards, and for other reasons, it is necessary that working and living conditions aboard submarines be the best possible. The food must be not only the finest, but it must be preserved in the best way. Agreeable living conditions and wholesome food go a long way toward maintaining the health and morale of the entire personnel at peak levels.

1A2. Preservation of food. Certain kinds of food, such as meat and dairy products, deteriorate rapidly at ordinary temperatures. They can be preserved only at low temperatures. Refrigeration prevents, or at least retards, the formation of molds and the growth of bacteria and other microorganisms that cause the spoilage of stored food. Obviously, the length of time that a submarine can remain at sea is controlled to some extent by the length of time that perishable foods necessary

  for normal diet can be preserved by means of proper refrigeration.

1A3. Palatability of foods and beverages at low temperatures. It is not sufficient that foods be nutritious and in good condition to be fully enjoyed. They must also be palatable. Some foods and beverages are more palatable when consumed in a chilled condition. Tepid drinking water supplies the human body with needed moisture equally as well as cold water, but it is hardly refreshing in hot weather. Who can enjoy the sticky sweetness of melted ice cream? Refrigeration thus increases the enjoyment of certain foods.

1A4. Air-conditioning and ventilation. Of as great importance as the foods a sailor eats is the air he breathes. The air on board ship, as well as the foods, often needs to be cooled. Moreover, during long dives, the air in submarines is used over and over again, and therefore requires proper conditioning.

1A5. Protection of equipment. Too much moisture in the air may interfere with the proper operation of electrical equipment. It is therefore necessary to prevent moisture from condensing on such equipment.

 
B. COLDNESS AND HEAT DEFINED
 
1B1. Coldness and heat are relative terms. Strictly speaking, coldness is not a distinct condition separate from hotness. The two terms are purely relative, without exact meanings. They merely express temperature conditions with reference to a standard. This standard usually is the temperature of the human body, which is normally 98.6 degrees Fahrenheit. If a person picks up a piece of ice, he says the ice is cold; he means that its temperature is lower than the temperature of his hand. If he drinks a cup of coffee, he says the coffee is hot; he means merely that its temperature is higher than that of his mouth. Nevertheless, the ice is warmer than liquid   air, for example, and the coffee is cooler than boiling water.

In discussing matters pertaining to refrigeration and air-conditioning, often it is preferable to use the expression cooling, rather than the awkward expression removing heat. After all, refrigeration and air-conditioning deal with the maintenance of conditions best suited to the health and comfort of the human body, and are concerned with temperatures that human beings refer to in ordinary usage as cool and hot. In this manual, when cooling is used, it is understood that the operation actually consists of removing heat.

 
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