There are millions of domestic and small commercial refrigerators in the world today, and each year millions more are manufactured. In the UK in 1998 there were 1.47 cold appliances per household, and this is expected to increase to 1.54 by 2010 [1]. The basic technology for the refrigerator circuits was developed in the 1930's [2]. The circuit consists of an evaporator, compressor, condenser and a capillary tube. Essentially, the circuit is a single tube connecting the inlet and outlet of the compressor; part of the tube is in an insulated box (the evaporator) and part is in the surrounding environment (the condenser). The length of tube connecting the condenser to the evaporator is of small diameter (the capillary tube, diameter in the order of 1mm). Most refrigerators have the added refinement of part of the capillary tube being in close contact with the suction tube. Development of the basic technology has concentrated on reducing the cost of production and of adding consumer functionality to the refrigerator (frost free, ice maker etc). The amount of energy used by a single refrigerator is perceived by most consumers to be small, so reducing energy consumption has not been a high priority for development. That has now changed. During the 1990s, governments have been taking action to reduce the energy consumption of domestic and commercial refrigerators and freezers. Refrigerators run continuously and therefore consume a large proportion of the total electrical consumption. In the UK, cold appliances consumed 17% of the total household electrical consumption in 1997, 17,488GWh. The UK has set a target to reduce this to 12,784GWh by 2010. Government action starts with requiring labelling the unit with its energy consumption and then uses a mix of incentives or probations to reduce the overall energy consumption. Manufactures have responded by concentrating development on reducing the energy consumption of their refrigerators, without loosing any of the functionality. The developments either reduce the refrigeration load or improve the efficiency of its removal.
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