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  • ELSEVIER

    Int J. ReJrig. Vol. 19, No. 1, pp. 61 69, 1996 Copyright c t~ 1996. Published by Elsevier Science Ltd and IIR

    Printed in Great Britain. All rights reserved 0140-7007(95)00069-0 0140-7007/96/$15.00 + .00

    ]REV IEW PAPER]

    Domestic refrigerators: recent developments

    R. Radermacher and K. Kim* Center for Environmental Energy Engineering, University of Maryland, College Park,

    MD 20742, USA

    The refrigerator/freezer is one of the most important and the biggest energy-consuming home appliances. There are several literature references that discuss the historical development of refrigeration I~ lg. Most of them, however, consider historical highlights up to several decades ago. This paper summarizes recent developments in the field of domestic household refrigerators based on a survey of publications and patents. (Keywords: Refrigerator; domestic review; refrigerants, cycles, charge optimization)

    R6frig6rateurs domestiques: mises au point r6centes Le r~frig&ateur-cong~lateur domestique est I'une des applications domestiques les plus importantes et les plus consommatrices d'Onergie. Plusieurs publications (voir bibliographie 1 14) {tudient l'histoire du Jroid. La plupart d'entre elles font remonter les grands moments historiques it plusieurs d~cennies. L'article r{sume h,s mises au point rdcentes dans le domaine des rOfrig~rateurs domestiques bas~s sur l'ktude des publications et des marques. (Mots-cl~s: ???; ????)

    In the beginning

    From William Cullen of the University of Glasgow, Scotland, who was recorded as the first person to demonstrate the man-made production of cold when he evaporated ether in 1748, to Jacob Perkins who developed the first practical refrigeration machine using a vapour compression cycle in London with ether as the refrigerant in 1834, the refrigeration industry developed steadily. When electricity became generally available, William F. Singer of New York, patented the earliest automatic electric unit for small-size refrigerating systems in 189715 .

    As electric-generating capacity grew and as homes were beginning to be wired for its use, household refrigerators became more popular and began replac- ing the common window and standing iceboxes. The interest and demand for household refrigerators was aided by the design and development of fractional horsepower motors, which were used in refrigerators. These units began being produced in large numbers in the early 1920s and have become a necessity for all.

    Isko was probably the first reasonably successful air- cooled unit. Fred W. Wolf designed and marketed a household system called DOMELRE, a contraction of Domestic __Electric Refrigerator. The Wolf system was marketed by Mechanical Refrigerator Company and later by Isko until absorbed by Frigidaire in 1922. But the most important technical contributions were made

    * Present address: Living Systems R&D Center, Samsung Electronics Co. Ltd, 416 Maetan-3Dong, Suwon 442-742, Korea

    by General Electric and the Kelvinator. General Electric had begun to manufacture the Audiffren machine in 191116 and in February of 1918, Kelvinator sold its first refrigerator 17. One of the first practical automatic controls was the thermostatic switch developed by Copeland for the first Kelvinators ~8. The sealed unit, which eliminated the belt, was introduced in 1925 by General Electric 16"1s.

    Advances in materials and design

    As plastics and techniques in working plastics, and new insulating materials, were developed, the small domestic refrigerator became highly sophisticated in design and construction, and the ratio of useful storage capacity to total volume increased.

    A great impetus to refrigerator design was provided by the introduction of the halogen refrigerants with which non-ferrous metals could be employed. The fluorocarbon refrigerants were announced by Midgley and Henne in

    a9 1930 and the introduction ofdichlorodifluoromethane (R12) as a commercial refrigerant in 1931. From the late 1920s, an extremely small bore was considered to reduce the pressure of sulphur dioxide (R764). With the introduction of the physically safe, oil-soluble, halo- genated hydrocarbons as workin~ fluids, the application

    20 1 of capillary tubes increased '~. Before that time clogging of the capillary tube posed a challenge and usually an expansion valve was used. The introduction of R12 removed an important obstacle to complete acceptance of domestic mechanical refrigeration, for earlier manufacturers have been compelled to depend on refrigerants such as sulphur dioxide (R764), methyl

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  • 62 R. Radermacher and K. Kim

    chloride (R40), and methyl formate (R611) and dichloro- methane (R30). All of these fluids are toxic.

    During the 1930s the domestic refrigerator was standardized. The hermetic compressor became the norm, and with its adoption, rotary compressors began to substitute the older reciprocating compressor tech- nology. Expansion valves were replaced by capillary tubes. The refrigerators, all self-contained, were built of steel and were well insulated. Finally, the mechanism was placed at the bottom of the unit.

    A more important development was the two-temper- ature refrigerator, which was introduced about 1939 and began to come into its own in the post-war period. As its name implied, it consisted of two separate compartments like the current refrigerator/freezer unit 22.

    Between the 1950s and 1960s, domestic refrigerators changed considerably from the early designs. Multiple compartments had made them more complex. Designs had been refined to meet exacting customer demands. Acceptance levels had been raised considerably 23. In 1944 almost 70% of American homes that had refrigerators were equipped with 'mechanicals '24 and in 1958 94% of households owned refrigerators in the U.S. 25.

    Environmental concerns

    In 1974, Rowland and Molina 26 advanced the hypothesis that antrhopogenic emission of certain chlorinated and bromate compounds, particularly chlorofluorocarbons (CFCs) and hydrochlorocarbons (HCFCs), could accumulate in the stratosphere and substantially deplete the ozone layer that shields the earth from cancer- causing ultraviolet-B solar radiation. Within a few years the issue had moved onto the public policy agenda, and the U.S. Congress in 1978 banned the use of CFCs as aerosol propellants, which accounted for the majority of total CFC emissions in the U.S. at the time 27. Since the ozone layer depletion is a global problem, an inter- national treaty to regulate the production and trade of the ozone-depleting substances, the Montreal Protocol, was signed by 24 nations and the European Com- munity "28'29. It required the U.S. and other signatories to reduce production of CFCs to 50% of 1986 levels by 1998, and placed no restrictions on the production of HCFCs. Refrigerator/freezers were one of the major technologies dependent on R12 as a refrigerant.

    Besides contributing to the destruction of strato- spheric ozone, the Antarctic ozone hole and significant ozone reductions in the Arctic, CFCs have been implicated as a major anthropogenic cause of global warming. As refrigerants are lost through leaks, equip- ment maintenance and retirement, they disperse throughout the atmosphere and act as greenhouse gases and contribute to global warming. In addition to the accumulation of CFCs in the atmosphere, the carbon dioxide emissions associated with energy used to operate refrigeration equipment, such as the domestic refrigera- tor, reflect the greenhouse warming effect. Almost all this energy results from the combustion of fossil fuels and creates emissions of CO2. Carbon dioxide is the largest contributor to global warming 3. Since refrigerators consume about 2.9 1011 kWh of primary energy, or 12% of the total residential energy budget annually, substantial improvements in domestic refrigerator/

    freezer efficiency extended over the 15- to 20-year life of this" appliance would significantly~l benefit national goals for environmental progress .

    Test results with new refrigerants

    While new refrigerants were being developed and tested in response to the environmental challenges, one possible solution that was proposed for alterantive refrigerants focused on using zeotropic refrigerant mixtures, whose components were environmentally safe and their characteristics as drop-in refrigerants appeared to be promising.

    From the 1960s numerous publications throughout the world explored the use of refrigerant mixtures primarily with two objectives in mind: (1) achieving a low evaporator temperature with a moderate pressure ratio during single-stage compression and (2) conserving energy when the refrigeration duty consists of cooling a fluid stream through a large temperature range 32 37.

    However, the refrigerant most commonly considered as the future substitute for CFC12 in domestic equip- ment was HFC 134a. Many calculations based on simple Rankine cycle models, however, have concluded that HFC134a is less energy efficient than CFC123s. These claims were confirmed by experimental results which showed efficiencies for HFC134a which were 4-10% less than those for CFC1239'4.

    In order to overcome difficulties of pure alternative refrigerants, a number of binary and ternary mixtures were suggested 34'41 43. Among the proposed fluids was also a mixture of R22 and R142b, with the latter being a flammable component. At this time, a mixture contain- ing R22 was still acceptable and had the advantage of being compatible with the familiar alkylbenzene lubri- cant. Moreover, since the percentage of a flammable component was relatively low, the flammability problem would be eliminated. These mixtures had 'drop-in' characteristics for use as a substitute in exis

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