Refrigerators

116. Principles of Refrigeration. Refrigerators (Fig. 56) are designed to prevent the rapid spoiling of food by keeping it too cool for the rapid growth of bacteria. They vary considerably in their efficiency, according to their construction and to the way in which they are managed. To preserve food and to save ice, the housewife must understand her refrigerator, and she must choose a good one. There is as much difference in the efficiency with which housewives manage their refrigerators as there are differences in refrigerators.

A series of experiments were conducted with a number of different makes of refrigerators. When the outside temperature was between 80 and 90 degrees Fahrenheit, and when the refrigerators were kept full of ice, it was found that the temperatures in different refrigerators varied between 45 and 60 degrees Fahrenheit. When the refrigerators were only partly full of ice, their temperatures rose several degrees.

The refrigerators which held a temperature of 45 degrees when filled with ice, or with 100 pounds, used 25 pounds of ice each in three days, while in the same three days, the ones which could maintain only a temperature as low as 65 degrees, used 50 pounds each. The warmer the inside of a refrigerator, the faster the ice melts.

In general, a refrigerator which maintains a low temperature is cheapest to operate. The refrigerator should be kept full of ice exposed so that it comes in contact with the air circulating within the refrigerator. The refrigerator which does not hold a low temperature will not only use more ice, but be less efficient in keeping food.

117. The Construction of Refrigerators. The construction of a refrigerator should be such that it may be kept clean. There should be no cracks and corners to catch dirt and make breeding places for molds and bacteria.

118. Lining Refrigerators. The best linings for refrigerators are porcelain, porcelain enamel, or glass for the more expensive ones, and galvanized iron or zinc for the less expensive ones. The shelves are usually made of heavy wire or of bent metal. The latter should be constructed so that they can be thoroly cleaned.

119. Insulation of Refrigerators. The more complete the insulation of a refrigerator, the more efficient it will be. Different kinds of material, as well as dead-air spaces, are used for this purpose. The top, as well as the bottom, must be insulated. Materials which are likely to crack or settle down and leave uninsulated spaces should not be used. Because sawdust settles, it is not satisfactory. There are felts, papers and other materials which are good. If the refrigerator is not water-tight and the insulating material absorbs water, it will lose its efficiency for insulation.

120. Circulation in Refrigerators. The better the circulation in a refrigerator, the more efficient it will be. The air in the refrigerator must be free to circulate over the ice. As it cools, it should drop to the bottom of the ice box. When it warms, it will rise and be displaced by fresh falling cold air. It should be free to rise to the top of the refrigerator and from there pass into the ice chamber and over the ice to be cooled again (Fig. 57). When the ice always melts unevenly and in the same relative place—that is, more on the side or bottom—it indicates poor circulation in the refrigerator.

121. Drip from Melting Ice. There should be a pan under the ice to catch the drip from the melting ice, and a drip pipe to carry it out of the refrigerator (Fig. 57). If the drip pipe passes into a pan set under the refrigerator, the pan should be emptied so that it will not overflow. The water in the pan should not be allowed to become stagnant.

If this pipe passes to a drain, it should not be attached to the drain, but drip into it. The small amount of fresh air passing up the drip pipe from the room is advantageous. Because some air does flow thru here, the drip pipe and the drain pipe must be clean and free from gases and odors.

The drip pipe should be straight and free from places in which dirt may collect. It must be removable, so that it can be cleaned. The doors of the refrigerator must shut so tightly that frost or dew will not form about their edges on a hot day.

122. Arrangement of Food in the Ice Box. Ice boxes are usually cooler at the bottom than at the top. Do not put food in the ice chamber because this necessitates opening the door and wastes ice. Do not put papers or flat boxes on the shelves which will interfere with the circulation of air in the refrigerator.

123. Filling and Care of the Ice Box. The housewife must open the doors of the ice box as seldom as possible, and close them quickly. Do not cut off the circulation of air from the ice by wrapping it in a blanket or newspapers. It cannot do its work then. The ice box is kept cold by the gradual melting of the ice. The ice melts fastest as the temperature of the ice box rises. Covering the ice may keep it from melting, but it will also allow the refrigerator to get warm, and so, whatever is gained in saving ice at first, will be lost at the higher temperature and in cooling the box again. Steady melting does the most good.

The shelves and drain pipe should be removable, and these and the refrigerator should be washed and thoroly scalded once in every two weeks.

There is a saving in planning to open the refrigerator as little as possible. The filling of the ice box with a large piece of ice two or three times a week, rather than with a small piece every day, is more economical.