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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Household electrical appliances. Refrigerators and freezers. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Household Appliances Refrigerators in the list of home electrical equipment are at number two. The main feature of the classification of refrigerators is the principle of cold generation. Depending on this, all refrigerators are divided into absorption and compression. Absorption refrigerators, the principle of operation of which is based on the physical property of an aqueous solution of a refrigerant (ammonia) to absorb a large amount of heat during evaporation, have excellent consumer characteristics: they are quite easy to repair and extremely reliable in operation; they work almost silently. Their only drawback is their high energy consumption: the annual electricity demand of an absorption refrigerator is about 1400 kWh (for comparison: a compression refrigerator consumes only about 400 kWh during the same period). The disadvantage, although the only one, is quite significant; that is why this type of refrigerator is not widely used. The cooling circuit in compression-type refrigerators (Fig. 87) is a closed system filled with refrigerant.
The components of the cooling system are: a motor-compressor, an evaporator, a condenser, a control valve and pipelines by which these elements are connected to each other. In refrigerators of compression type, two types of compressors are used: with an external casing suspension and with a compressor suspension inside the casing - next to the motor. The cooling system operates as follows: the motor-compressor draws refrigerant vapor from the evaporator, as a result, low pressure is created in the evaporator. In the compressor, the refrigerant vapors are compressed and fed into the condenser, where, as they cool, they turn into a liquid, which again enters the evaporator and again turns into vapor in it. The entire heat exchange process of the cooling system takes place directly in the evaporator and condenser: turning into vapor, the refrigerant absorbs heat through the surface of the evaporator (which is located in the freezer of the refrigerator), and turning into a liquid, gives off excess heat through the surface of the condenser (which is located outside the refrigerator, on its back panel). The evaporator and condenser are interconnected by a control valve; it has a small flow area, which does not lead to pressure equalization and allows you to always keep a rarefied pressure in the evaporator, and increased pressure in the condenser. The compressor is driven by an electric motor, which is the consumer of electricity. The breakdown of the refrigerator causes the housewives not just a feeling of discomfort, the question arises of preserving perishable products: it’s good if it’s winter outside and you can save them on the balcony; and if it's summer outside and even the heat is 35 ° C? That's when you need maximum efficiency in fixing problems. Of course, the device of a refrigerator is quite complicated, not every malfunction can be fixed at home (for example, to repair a cooling system, not only extensive special knowledge, not only certain skills, but also very specific devices are needed that are hardly available to a home master). If the breakdown touched the electrical economy, then here you can try to cope on your own. The first thing to check in a broken refrigerator is the serviceability of the wiring: if the light bulb is on when the door of the refrigerator connected to the mains is open, then the wiring is intact. If the light does not light up, you need to check the serviceability of the cord and plug connection (both plugs and sockets); how to do this - has been said more than once. The next part of the refrigerator that is tested (with a good cord and plug connection) is the start-up relay. Check the reliability of the connection of wires with the terminals of the relay and the temperature controller and the connection between the feed-through contacts and the sockets of the relay. Then they check the relay itself - they call it with a tester; often it is the culprit of the malfunction. Next on the list is checking the thermostat: turn it on and off several times. If a characteristic click is heard when the thermostat is turned on, then the thermostat is normal. If there is no click, then this means that the thermostat is faulty; it should be replaced. If the refrigerator is working properly, but the light does not light up when the door is open, maybe. light bulb burned out. To replace it, compress the horizontal walls of the ceiling in the back and disengage it from the walls of the cabinet, replace the light bulb and install the ceiling in place. If the situation is exactly the opposite: the light bulb is on even when the refrigerator door is closed, then the switch button spring has most likely weakened. It is unlikely that it will be possible to replace the spring on your own (for this you will have to remove the inner lining of the cabinet, which can violate its tightness), so you can use this advice: cut a small circle 1 mm thick, 15-20 mm in diameter from plastic (textolite, copolymer, etc.) and stick it on the door panel opposite the switch button with universal glue. If the electric motor hums, but does not start (the thermal relay is activated), then the voltage in the electrical network may be lowered by more than 15% relative to the nominal value. It is necessary to turn off the refrigerator and check the voltage in the network with a voltmeter, and if it is really less than permissible, you should refrain from using the refrigerator. In fact, the stability of the voltage in the network affects the correct operation and life of the refrigerator to a large extent, therefore, if the voltage in the network jumps a lot, it is necessary to use a voltage stabilizer to connect the refrigerator, without waiting until the refrigerator starts to malfunction. A metallic knock when turning on, off and running the compressor, accompanied by cabinet vibration, is not the norm for a working refrigerator - this indicates that the pipes of the cooling system touch the cabinet. To eliminate this drawback, it is necessary to turn the refrigerator with the back wall and examine the panel; having found the place where the tube touches, you need to carefully bend it. Sometimes knocking can be caused by a completely different reason - strong rocking of the compressor casing. Repair consists in tightening (or loosening) the bolts on the suspension springs or in laying gaskets under the supports. Sometimes the cause of knocking is not a malfunction, but a loosening of the capacitor mounting screws or a foreign object that has fallen behind the back panel, behind the capacitor or behind the motor-compressor. A refrigerator delivers a lot of trouble, the evaporator of which quickly freezes up, and it often turns on (which leads to wasteful energy consumption). As a rule, the reason for this is a violation of the tightness of the door. Restore tightness will help adjust the hinges of the door, and you can check the quality of tightness using a strip of thick paper. It is placed between the door seal and the cabinet itself anywhere along the perimeter, close the door and try to pull out the strip: if the paper is clamped tightly, then the tightness is restored (it is preferable to check the entire perimeter of the seal). Damage to the paint layer on the cabinet and refrigerator door can lead to corrosion of the metal from which they are made, therefore, if scratches are found on the outer surface of the refrigerator, they should be eliminated in a timely manner. With a shallow scratch, when the metal of the case is not visible, it is simply painted over with white enamel. If the depth of the scratch reaches the metal, then it must first be cleaned with an emery cloth, degreased with a swab dipped in acetone, dry the surface thoroughly and only then apply a layer of white enamel (if necessary, after it has completely dried, another layer can be applied). You can significantly extend the life of the refrigerator, if you strictly follow all the recommendations for the operation and care of it. What are they? Firstly, the refrigerator is not recommended to be placed in close proximity to heat sources (stoves, stoves, heaters, etc.). In addition, it is advisable to choose a shaded place for it - this will reduce the flow of heat into the refrigerator and reduce energy consumption. And in order for the rear panel to be available for free air circulation (which prevents the engine from overheating), the distance between the wall and the rear panel must be at least 3-4 cm. Secondly, it is necessary to ensure the complete stability of the refrigerator when installing it; this can be achieved with the help of adjusting feet screwed into the rear and front heels. The adjustment should be made in such a way that the cabinet has a slight (no more than 1°) deviation from the vertical towards the rear wall; in this case, the refrigerator door will close with a slight push. Thirdly, it is recommended to turn on and off the refrigerator only with the thermostat knob; therefore, before plugging the cord into a power outlet, make sure that the temperature control knob is set to the "off" position. When checking the operability of the refrigerator, it can be forced to turn on again no earlier than 5 minutes after it is turned off (if you do not withstand this time, the refrigerator will not turn on - the thermal relay will work). Fourthly, when a snow coat of more than 5 mm is formed on the evaporator, it is necessary to turn off the freezer (freezer). With proper operation of the refrigerator and normal tightness, defrosting is carried out once every 2-3 weeks. The refrigerator is turned off (setting the thermostat knob to the "Off" position), and for faster defrosting, the refrigerator and freezer doors are left open. There are several ways to speed up this process: place a vessel with hot water in the freezer, direct warm air from a vacuum cleaner or hair dryer into it, in the summer, use a stream of air from a fan, etc. But it is forbidden to use sharp metal objects to remove frost: there is a possibility of damage to the walls of the evaporator, this will render it unusable, and a complete replacement of the evaporator will be required. After the snow cover has thawed, the inner surfaces of the evaporator and the refrigerator are wiped with a soft cloth moistened with slightly soapy water or soda solution (water should not get behind the inner lining of the cabinet and the door), dried and ventilated for 30-40 minutes. Before loading the freezer after it has been thawed, it is necessary to cover its bottom with a plastic bag, and also place portions of perishable products in the bags; otherwise, the products may freeze to the bottom of the freezer, which will make it difficult to remove them from there, and if excessive force is applied, microcracks may appear in the walls of the evaporator. Household refrigerators and freezers are produced in more than 60 countries around the world. The leading companies in this area are the firms of the USA, Japan, Germany, Italy and England. They are also pioneers in the development and implementation of the latest designs and improvements that define the world level of household refrigeration. In many developed countries, the market for household refrigerators has reached saturation and new models of refrigerators are purchased exclusively to replace or expand the old fleet. The incentive to buy new models is their technical improvement, high automation, low energy consumption, comfort, ease of use. Almost all leading foreign firms focus on the production of compression models, and only a few firms specialize in the production of absorption refrigerators, and their modern models are not inferior to compression models in terms of basic consumer characteristics. An insignificant part of the total production volume is made up of thermoelectric refrigerators, which are used in air, road and water transport. Thermoelectric refrigerators are manufactured by Kolatron Corp, Vogel Commercial Refrigerator, etc. Some models of refrigerators from these companies can operate in both cooling and heating mode, which is an important factor in certain areas. An analysis of the assortment structure of household refrigeration equipment supplied to the market shows that manufacturers take into account the most diverse social groups of consumers. For example, depending on the quantitative composition of the family, the consumer can choose a model with the desired (in practice - any) volume. Families with individual and regional nutritional needs are provided with models with different combinations of functional zones and temperature regimes for food storage. Depending on the degree of automation and comfort, the models (differentiated, of course, by price) are addressed to families with different budgets. If you are looking to decorate your home interior to your liking, then you can easily select models of various sizes and designs that are built into a kitchen furniture set or interlocked with kitchen equipment. Freezers, two- and three-chamber refrigerators of various sizes are widely represented on the market today. American, Japanese and Western European firms produce models with a volume of up to 700 liters or more, with four or even five chambers, each having several functional zones with different temperature conditions for storing products. Two-chamber refrigerators with a vertical arrangement of chambers have become more widespread. The refrigerator-freezer combination is considered to be more suited to the needs of city dwellers, since the limited space of kitchens (the average kitchen area, for example, in England is 7,5 mXNUMX) does not allow the use of free-standing "cupboard" refrigerators and freezers. Combination "refrigerator-freezers" of vertical design have thus become competitors of "cabinet" type freezers, especially with the advent of models with a single compressor, which has significantly reduced their price. The limited kitchen space made us appreciate the Japanese design and layout options for three- and four-chamber models (the lower chamber is designed to store fresh vegetables and fruits), which have become an alternative to American-style three- and four-chamber models, in which the chambers are located side by side. Firms offer models with a different ratio of volumes of refrigerators and freezers. So, in two-chamber refrigerators, the capacity of low-temperature and freezers is 20-30%, and in combined refrigerators-freezers - up to 50% of the total volume. From year to year, the comfort of new models increases and consumer characteristics improve - stable maintenance of optimal temperature conditions (i.e., improved food safety), significant energy savings, and increased reliability and safety of operation. Comfort features include: 1) automatic system for defrosting and removal of melt water outside the cabinet; 2) non-freezing system (No frost), which prevents the formation of frost on the products and the walls of the freezer; 3) automatic system for maintaining optimal temperature conditions; 4) automatic systems that inform the consumer about an emergency change in temperature conditions (light or sound alarm); 5) devices that maintain the optimal temperature regime during an emergency power outage; 6) automatic ice generators; 7) systems for dispensing ice or chilled beverages without opening the refrigerator door; 8) addition of a refrigerator with a microwave oven, a tape recorder, etc.; 9) the possibility of choosing or replacing the decor of the front outer panel, etc. In the household refrigeration market, you can find models designed for operation as part of kitchen equipment - integrated or built-in. Some firms supply the market with new refrigeration units, which are the development of design and layout options for various kitchen equipment. For example, the firm "Vedette" has released a combined appliance "stove-refrigerator". Its upper plane consists of two gas burners and two electric burners, below it there is a retractable working plane for processing products. And in the lower part there is a refrigerator with a capacity of 170 liters without a low-temperature compartment with a semi-automatic defrosting system. The company "Privileg" has long been advertising a model of a single-chamber refrigerator with a useful volume of 128 liters, interlocked with a sink and an electric stove ("mini-kitchen"). An important indicator of the refrigerator class is the shelf life of products. At present, the production of models with a temperature in the low-temperature compartment of -6 ° C has practically ceased, manufacturers have switched to the production of models with a temperature of -18 ° C, which allows you to store frozen food for up to 10-12 months. Following the American and Dutch firms, Japanese and Western European manufacturers have improved the functional properties of refrigerators by creating separate chambers (compartments) with different temperature conditions, increasing the shelf life of the corresponding range of products. There were separate chambers for storing vegetables and fruits at a temperature of 7-12 ° C. In such chambers with a tightly closed door, with moderate cooling, up to 88% of vitamin C is preserved in the products, while in the usual compartment of the refrigerating chamber - only about 44%. Increasingly, as part of multi-chamber models, separate chambers with temperatures from 0 to -2–3 ° C for storing fresh meat and fish appear. Sometimes, instead of a separate chamber, a compartment in a common refrigerating chamber is used for this purpose, and the optimum temperature in it is maintained using special dampers that regulate the flow of cold air. In some models of Japanese refrigerators, the refrigerator compartment has compartments for accelerated cooling of products (wine, juice, etc.) before use (Quick chilling). Technological progress in the development of refrigeration technology has led to an increase in the level of automation based on the use of electronic control circuits, thyristor technology and the introduction of program control. Automation not only improves functional performance, expands the range of functions performed, but also increases the reliability of products, allows you to program processes, conduct self-diagnosis of faults. The automatic defrosting system has long ceased to be an accessory of high-comfort refrigerators; it is already an integral part of the design of ordinary models. In addition to the USA, where the share of models with automatic defrosting is almost 100%, their production has grown significantly in Japan, Germany, Italy, England and other countries. Today, all leading companies in Japan and Western Europe produce refrigeration equipment with an electronic control system that controls and regulates temperature conditions in functional areas, controls the mode of freezing products, provides a quick diagnostic check of all functions of the device, saves electricity, etc. The diagnostic system checks the unit power supply, temperature conditions in the chambers, the defrosting system, the operation of the ice maker and the control system. One of the decisive requirements of the buyer was the reduction of energy consumption, which determined the strategy of manufacturing companies when choosing priority areas for improving products. Today, manufactured products are supplied with special passports indicating the efficiency and average energy consumption, which gives the buyer the opportunity to compare models from different companies in terms of annual operating costs. Over the past 15-20 years, the energy consumption of household refrigerators has been reduced on average in Japan by 70%, in Germany - by 50%. By 2010, the average annual rate of reduction in the specific energy consumption of household refrigeration equipment by Western European firms will be 3,1%. In the US, this rate is higher, as American refrigerators are less economical than Western European ones. The energy efficiency of household refrigeration equipment is achieved by improving the characteristics of the motor-compressor and the quality of thermal insulation, improving the refrigeration unit, and using automation and electronics. Japanese and Western European firms use rotary compressors instead of reciprocating compressors, which allows, along with a reduction in energy consumption (more than 230 times for refrigerators with a capacity of 2 liters), to increase the useful volume of the refrigeration chamber by an average of 12 liters, increase reliability, reduce the weight of the refrigerator and noise. (The rotary compressor is 64% smaller than conventional compressor and 35% lighter.) In the production of refrigeration equipment, especially freezers, there is a tendency to increase the thickness of thermal insulation and search for new thermal insulation materials. Firms in Germany, Denmark and other countries have increased the thickness of the heat-insulating layer in freezers up to 70-100 mm, which ensured a reduction in electricity consumption by 40-50% compared to previously produced models. At the same time, the operating time of the compressor has significantly decreased, therefore, the duration of its service has increased. The Japanese company Hitachi, as a result of the use of rotary compressors, as well as improved thermal insulation, has reduced energy consumption by more than half. Firms in the US and Western Europe are successfully working towards saving cold during an emergency power outage. Thus, the presence of 100 mm thick thermal insulation in freezers ensures the duration of storage of frozen products during a power outage for almost 3 days. This raises the temperature to -9 °C, which is considered optimal for short-term storage of frozen food. Almost all freezers produced abroad, as well as most two-compartment refrigerators (especially combined refrigerator-freezer models) have an accelerated freezing mode for fresh food at a temperature of -24 to -30 ° C. The productivity of these models for freezing is 1-0,1 kg / day per 0,25 liter of volume. Freezers are equipped with special trays for quick freezing of small products - berries, mushrooms, etc. Speaking about the automation of the control of operating modes, it is necessary to note the accessibility and information content of the controls. Most of them are located on special panels, highlighted in color, contrasting with the background of the panel, equipped with informative graphics - inscriptions or pictograms that decipher their functional purpose. Much attention is paid to information about the range and shelf life of products in freezers. Pictograms indicating meat, sausages, vegetables, berries, etc., with the corresponding shelf life, are located on the inside of the door. In all models of freezers on the front panel of containers with frozen food there are special indicators about the assortment of each container. Careful ergonomic study of the designs made it convenient to load and remove products. In some models of refrigerators, the chamber for vegetables and fruits is made in the form of a retractable container, and in the SR311MV refrigerators of the Japanese company Sanio, the chamber moves out by rotation. In the Siemens model KS2744, the refrigerator compartment shelves can rotate around an axis and slide out of the compartment. The design improves visibility and facilitates product access. Models with double-sided opening of the door, cantilever mounting of shelves and the possibility of their re-hanging have become the norm. In Japanese models, shelves are often used that are transformable in area, which allows you to more tightly place products of various sizes, shapes and sizes. At present, instead of the usual method of dissipating heat from the back of the refrigerator, the so-called "internal" method of dissipation is used. In this design, the coil is removed from the rear wall, and the heating tubes of the condenser are placed along the inner side walls of the device. The absence of tube vibration reduces compressor noise and improves hygiene. Along with the growth of the technical level of modern refrigerators and freezers, the level of artistic design development and production performance of products continues to rise. When forming complexes of kitchen equipment, in which the refrigerator is an integral part, the design of the refrigerator is decided in stylistic unity with other kitchen equipment. The refrigerator receives dimensions, shape, color and finish that correspond to the design concept of the design of all kitchen equipment, loses the external features inherent in it as a separate independent object. Artistic and design solutions of the best foreign models are rational and concise. High expressiveness of the form is achieved due to the careful plastic elaboration of individual elements, the clarity of compositional solutions, the use of original color and graphic solutions. The modern style in the design of refrigerators is a strict and at the same time decorative finish, a variety of colors. Laconic graphics perform both an identifying role (name of a product, company, brand name), as well as a functional one (information inscriptions, plates, pictographic symbols) and a decorative one (designing the interior of a model, equipment elements, etc.). Along with the traditional white color, blue, pink, olive, light green and beige tones are used in the exterior. Often, the finish imitates the texture of natural materials of wood, leather, textiles. The main structural material of refrigerators is steel with a protective and decorative coating of colored acrylic enamels. Steel is used both in combination with plastic spraying, and in the form of a corrugated textured surface. The use of aluminum for the manufacture of interior chambers and decorative panels, shelves, and handles has expanded significantly. The textured aluminum used for the interior of refrigerators does not corrode and is easy to clean. In the design of refrigerators, individual types of plastics or their combinations are increasingly used: polystyrene, styrene copolymers (transparent, smoky, colored), ABS plastic, which has high mechanical characteristics, thermal and chemical resistance, as well as manufacturability. Author: Korshevr N.G.
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