Author Topic: Refrigerator  (Read 540 times)

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Offline david

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« on: January 03, 2011, 02:48:44 PM »
Prior to the development of artificial refrigeration techniques during the 1800s, people utilized a variety of means to chill and preserve foodstuffs. For centuries, ice served as the principal refrigerant. Ironically, the ancient Indians and Egyptians pioneered an ice-making technique that served as the conceptual basis for the first "modern" refrigerators developed during the nineteenth century: evaporation. The relatively quick evaporation of a liquid creates an expanding volume of gas. As water vapor rises, its kinetic energy increases dramatically, in part because the warm vapor is drawing in energy from its surroundings, which are cooled by this process. The Indians and Egyptians took advantage of this phenomenon by placing wide, shallow bowls filled with water outside during the cool nights. As some water quickly evaporated, the remaining water cooled, forming ice. With this method, it was possible to create sizeable chunks of ice that could then be used to cool food.

Using a more primitive means of procuring ice, the ancient Chinese simply transported it from the mountains to cool their food; later, the Greeks and Romans adopted this practice. To preserve the ice itself, people stored it in pits or caves insulated with straw and wood, by which means they could maintain a supply of ice for months. In industrialized nations, ice served as the primary method of chilling food through the nineteenth century, when people inserted blocks of ice in insulated cabinets alongside the food they wished to store. Even today, in many developing nations ice remains the sole available refrigerant.

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