On a summer day, one may reach for a glass of cool water from one’s refrigerator while sitting down inside one’s cool home. While this setting seems simple enough to the common consumer, the engineer sees specifically engineered cooling systems allowing such climate control. A cooling system consists of a device or devices used to lower the temperature of a defined region in space through some cooling process.
Currently, the most popular commercial cooling agent is the refrigerant. A refrigerant in its general sense is what makes a refrigerator cool foods, and it also makes air conditioners and other appliances perform their respective duties. A typical consumer based refrigerator lowers temperatures by modulating a gas compression-expansion cycle, to cool a refrigerant fluid which has been warmed by the contents of the refrigerator (i.e. the food inside).
Typical refrigerants used in refrigerators from the late 1800’s through 1929 included ammonia, methyl chloride, and sulfur dioxide, all of which are toxic. To mitigate the risks associated with toxic refrigerants, a collaboration by Frigidaire, General Motors, and DuPont netted the development of Freon (or R12), a chlorofluorocarbon. Freon is a non-flammable and non-toxic, but ozone-depleting gas1.
Because of the damaging effects of Freon to the ozone layer, there has been much interest in targeting other refrigerants. The popular refrigerant R134a (called Suva by DuPont) is currently used in most refrigerators, but American and international laws are beginning to phase out this refrigerant as well. The future seems ripe for new refrigeration technology.
Source: MIT
Author: Dr. Robert O’Handley
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