Within a refrigeration system, the inside of the refrigerator is known as the cold-air reservoir, while the area surrounding the outside of the refrigerator is the hot-air reservoir. A refrigerator works by sucking the heat out of the cold-air reservoir and dumping it in the hot reservoir. The work to do this process is supplied by an electricity-powered compressor that is connected to a wall outlet. The efficiency of a refrigeration system can be estimated with a ratio known as the coefficient of performance, or COP. The COP is given by the benefit divided by the cost, or
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