Purpose and types of refrigerators, ways to obtain cold. Theoretical aspects of classification and characteristics of the range of household refrigerators
Usually a refrigerator- This industrial enterprise(or its workshop), in the premises of which, with the help of a refrigeration unit, certain modes necessary for the processing and storage of perishable products are maintained. The refrigerator consists of a technological building and a compressor workshop with an attached equipment department.
Refrigerators are classified depending on their purpose, type of stored products, capacity and number of floors. Depending on their purpose, refrigerators are divided into the following main ones: procurement, production, forwarding, distribution, transshipment, trade and household. In addition, refrigerators are divided into stationary and transport. Refrigeration is divided into rail, sea, river and road.
Procurement refrigerators are intended for procurement of products in rural areas or directly on plantations. They have high-capacity refrigeration units; The storage capacity of such refrigerators is less than the capacity of the chambers. Pre-cooling stations, mostly mobile, also belong to the procurement category.
Industrial refrigerators are part of food enterprises: meat and poultry plants, dairy and canning plants. Almost all manufactured products are refrigerated, so industrial refrigerators equipped with powerful devices for cooling and freezing.
Forwarding refrigerators provide cargo operations on rail, water and air lines.
Distribution (multi-purpose, basic) refrigerators are designed to uniformly supply cities and industrial centers with seasonal food throughout the year, as well as to create a reserve supply of food. These refrigerators are characterized by large storage capacity and low performance of cooling and freezing devices. In the event that distribution refrigerators have production workshops (packing oil, solid carbon dioxide, semi-finished products, culinary), such enterprises are called refrigeration plants.
Transfer refrigerators designed for temporary storage of products when transferring them from one part of the refrigeration chain to another. These refrigerators are characterized by a large load area. To carry out external cargo operations, special cargo platforms for road and rail transport are installed on the two longitudinal sides of the refrigerator.
Trading is used for short-term storage of products in retail chains, restaurants, canteens (). These refrigerators are small in capacity. The water chamber can store several different types of food.
Household refrigerators serve for short-term storage of food at home and for producing small amounts of ice. They are the last link in a continuous cold chain. The above classification of refrigerators is conditional. Depending on the range of stored goods, there are universal and specialized refrigerators.
In universal refrigerators They store mixed cargo (meat, fish, fruits, canned food, etc.), in specialized ones they store the same type. Depending on the capacity, refrigerators are conventionally classified into large, medium and small. Large refrigerators have a capacity of over 3000 tons (these include universal, distribution, and specialized refrigerators). The capacity of medium-sized refrigerators ranges from 1000 to 3000 tons (they can be universal or specialized). The capacity of small refrigerators does not exceed 1000 tons. Depending on the number of floors, there are single-deck and multi-deck refrigerators.
By design, refrigerators are classified as industrial buildings. Their characteristic feature is that the cameras support low temperatures at high . Changes in temperature and relative temperature cause a gradual weakening of the structure of building and insulating materials. Materials for refrigerator structures are selected taking into account the capital of the building. The building capital of refrigerators is divided into four classes: Class I includes buildings with a service life of over 100 years, Class II - from 50 to 100 years, Class III - from 25 to 50 years, Class IV - from 5 to 25 years.
The capital class is taken depending on the capacity of the refrigerator. Refrigerators with a capacity of 701 tons or more belong to class II, from 250 to 700 tons to class III, and up to 250 tons to class IV. With capital construction of refrigerator buildings corresponding to classes II and III, frame structures are made of reinforced concrete.
Comparative characteristics of the range of cotton and linen fabrics and directions of its development
Assortment of cotton and linen fabrics
All fabrics are divided depending on the raw materials used: cotton (cotton), linen, silk, wool.
Cotton fabrics differ varied design as a result of the use of various weaves and types of finishing, also good hygienic properties, wear resistance, lightness, beautiful appearance. Most of the fabrics are made from pure cotton, the rest using chemical fibers.
Classification:
Depending on the structure of the yarn: combed, carded, carded-combed, carded-hardware;
By production method: multi-colored and melange;
By the nature of the finish: harsh, bleached, plain-dyed, printed;
By groups: calico, calico, linen, satin, dress, clothing, lining, teak, pile, shawl, blanket;
By purpose:
1) linen fabrics (calico, calico, special fabric);
2) dress and shirt fabrics (chintz, calico, satin);
3) dress fabric: summer subgroup (chio fabric - chio san), demi-season (spark), winter (flannel, flannel);
4) pile fabrics (corduroy, velvet);
5) lining fabrics;
6) suit and coat;
7) towels, furniture and decorative fabrics and piece goods (handkerchiefs and head scarves).
Cotton fabrics are mainly made from yarn of various thicknesses, various weaves, but mostly plain.
Quality requirements: cotton, linen, wool fabrics There are 1 and 2 grades, silk - 1,2,3 grades
Placed on counters. The distance from the floor is at least 20 cm.
Linen fabrics have unique hygienic properties: they quickly absorb and release moisture, are vapor and breathable, and thermally conductive. Linen fabrics are indispensable for sewing summer clothes; they have high wear resistance and wash well. The disadvantage of linen fabrics is their high creaseability.
Classification:
Ingredients: flaxseed and semi-linseed;
By weave: plain, satin, finely patterned, large patterned;
By finishing: harsh, bleached, boiled, multi-colored, melange;
By purpose: linen, costume and dress, furniture and decorative, edging, linen, piece goods;
By width: canvases, narrow, wide canvases;
By groups: (16 groups):
1) linen (linen and canvas)
2) suit and dress fabrics (linen and semi-linen fabrics)
3) furniture and decorative (curtain, furniture, mattress, terrace fabrics)
4) fabrics special purpose(board, cover, harsh rough, mattress)
5) piece goods (tablecloths, napkins, bedspreads, towels)
Napkins are:
White (36x36, 62x62), tea (32x32), table (80x80)
Household refrigerators: classification, modern range of compression refrigerators
The most widespread classification of refrigerators is based on the method of “obtaining cold”:
Compression refrigerators and freezers;
Absorption-diffusion refrigerators;
Thermoelectric refrigerators.
Compression refrigerators are the most widely used. In these refrigerators, heat is taken from the internal chamber when the working substance (refrigerant) boils in the evaporator. Freons were previously used as working substances, which have now been replaced by other hydrocarbons.
Absorption-diffusion refrigerators use ammonia as a refrigerant and water, which serves as an absorbent. Heat is also taken from the refrigerator chamber when the refrigerant boils in the evaporator.
Thermoelectric refrigerators do not have a refrigerant; their operation is based on the use of the Peltier effect, which consists in the fact that when passing a constant electric current Through a thermoelement made of two series-connected (soldered) materials with different thermoelectromotive forces, heat is released at one of its contacts (junction), and heat is absorbed at the second. The cold junctions of the thermopile are placed in the refrigerating chamber, and the hot junctions are placed outside the chamber.
In the marking of domestic refrigerators, the type is indicated in the following way:
K - compression;
A - absorption-diffusion;
TE - thermoelectric.
Refrigerators, according to the current standard, can be classified according to a number of other characteristics, the main ones being purpose, installation method, number of chambers, temperature in the low-temperature compartment, complexity group, etc.
According to their purpose, all devices for storing food by cooling or freezing methods are divided into:
Refrigerators - devices for storing chilled products;
Freezers - devices for storing frozen foods;
Refrigerators-freezers are devices for storing chilled and frozen food products (from two-chamber refrigerators they differ large size low-temperature chamber - from 40 l, with two independent refrigeration units).
Refrigerators are classified according to installation method:
"Ш" - floor-standing in the form of a cabinet;
"C" - floor-standing in the form of a table;
"N" - built-in;
"B" - block-built;
"side-by-side" - cameras are placed parallel in a vertical plane.
According to the number of cooled chambers, refrigerators are: 1; 2 (D); 3 (T) and multi-chamber (M).
Based on the temperature in the low-temperature compartment, refrigerators are divided into 6°C intervals from -6 to -24°C (and below), every 6 degrees is usually designated by one snowflake. In the labeling of refrigerator-freezers with a temperature
in the NTK - 24°C, one large snowflake and three small ones are introduced, i.e. in normal storage mode the temperature in them is -18°C, and in freezing mode - 24°C.
Refrigerators can also be classified according to their climatic design (by their ability to operate at maximum temperatures environment):
SN, N - not higher than 32°C;
ST - not higher than 38°C;
T - not higher than 43°C;
Freezers:
N - not higher than 32°C;
T - no higher than 43°C. The chambers included in refrigerators can also be divided into types:
Chambers for storing vegetables and fruits - have high humidity;
Refrigerated chambers for storing chilled products;
Low temperature chamber (LTC) - for storing frozen food products;
MK - freezer;
Universal camera - a general purpose camera.
According to the degree of comfort, refrigerators are distinguished between standard and superior comfort. Deluxe refrigerators must have a device for automatic or semi-automatic defrosting of the evaporator, and in addition, one or more devices that increase ease of use:
A device for maintaining a certain humidity in the refrigerating chamber or part thereof;
A device for cooling drinks and dispensing them without opening the door;
Alarm about operating modes;
Device for forced automatic closing of doors when they are opened by 10°;
Door opening angle limiter;
Ensuring the rearrangement of shelves with a height interval of no more than 50 mm or extending the shelf to a distance of at least 50% of its depth while maintaining the horizontal position of the shelf;
Possibility of re-hanging the door.
The standard also provides for other comfort elements.
Depending on the functions they perform, refrigeration appliances are divided into complexity groups from 0 to 5. Group zero is assigned to the most complex models, and 5 to the least complex.
Compression refrigerators account for about 90% of the refrigerator market. The principle of operation of a refrigeration compression machine is as follows: when the refrigerator is turned on, the compressor starts working, refrigerant vapor (freon) flows from the evaporator into the compressor cylinder, where it is compressed by a piston. Compressed and superheated vapors are supplied under pressure to the condenser.
In the Condenser, the refrigerant vapors are cooled by the ambient air, condensed - they turn into a liquid state. Liquid refrigerant flows through the capillary tube into the evaporator, and the refrigerant pressure drops. In the evaporator, liquid refrigerant boils at low pressure, turns into steam and absorbs heat from the refrigeration chamber. The vaporized refrigerant again enters the compressor and the cycle repeats. The thermostat maintains the set temperature. During operation, the evaporator is covered with a “snow coat”. If the frost layer is more than 5 mm, this leads to greater energy consumption and heating of the low-temperature compartment.
Parameters of compression refrigerators. Electrical parameters determine the quality of the functional properties of refrigerators. Total internal volume (measured in dm3 and l) - the volume limited by the internal walls of the refrigerator at closed door and removed removable elements. The total volume of refrigerators according to the standard is from 60 to 500 dm3.
Volume freezer shows how much frozen food can be stored in the freezer compartment.
Functional properties include total energy consumption. For the consumer, this indicator has great importance, since the refrigerator operates 24 hours a day.
In Europe, since 1995, refrigerator manufacturers have been required to indicate annual electricity consumption on a special information sticker. For clarity, each energy consumption class is highlighted in color and designated by letters - from A to G: A, B, C - very economical; D - intermediate; E, F, G - with high and very high power consumption. Electricity consumption classes:
A 266-351 kW/year;
B 379-427 kW/year;
From 415-516 kW/year.
The ergonomic properties of refrigerators are determined by ease of use, degree of comfort, the strength of shelves, pallets, dimensions, occupied floor space, light and sound alarm.
The aesthetic properties of a refrigerator are color scheme, proportionality of the forms of the refrigeration cabinet, location of the chambers, expressiveness of brand marks.
The refrigeration unit must be safe in fire, sanitary (noise and vibration levels), electrical and mechanical terms.
Range of compression refrigerators. Compression refrigerators come in single, double and multi-chamber types. Such refrigerators are produced as combination refrigerators, such as “refrigerator-freezers”. The range of refrigerators available for sale includes a large number of models of different designs, different manufacturers: Atlant (Belarus), Electrolux (Sweden), Arston (Italy), Stinol, Nord, etc. Refrigerator markings: name, symbol model, serial number, type and amount of refrigerant, refrigeration chamber volume, production date.
The operation of refrigerators is based on the artificial removal of heat from internal space into the environment.
I. By the method of heat transfer from the refrigerator to the environment. Household refrigerators are divided into:
Compression (K);
Absorption-diffusion (A);
Thermoelectric (TE);
Magnetic (M).
In compression and absorption-diffusion refrigerators, heat from the refrigerator cabinet is removed into the environment using a special working substance - refrigerant (in compression refrigerators - freon gas , in absorption-diffusion - a solution of ammonia with hydrogen), which, as it circulates through closed system refrigeration unit changes its state of aggregation, changing from liquid to gaseous and back to liquid.
The process of transition from a liquid to a gaseous state (the process of evaporation or boiling) takes place inside the refrigerator and is accompanied by the absorption of heat.
In compression refrigerators, the movement of the refrigerant (freon - 12, less often freon - 22, another name is freon - 12, 22) is caused by the operation of an electric motor and a compressor (a complex unit designed to compress and increase the temperature of refrigerant vapors).
The refrigerant under pressure caused by the operation of the electric motor enters the compressor, where it is compressed and heated. The heated vapor enters the condenser, the temperature of which is lower than the temperature of the refrigerant. In the condenser, due to the temperature difference, condensation occurs (steam into liquid). The refrigerant then enters the evaporator through a narrow capillary tube. Since the evaporator channels are much larger than the diameter of the capillary tube, a pressure drop and boiling of the refrigerant occur in it. Turning into vapor, the refrigerant absorbs heat in the refrigerator compartment and the temperature decreases. Then the vaporous freon is sucked from the evaporator by the compressor and the whole cycle is repeated. The condenser is cooled by ambient air.
The design of the refrigerating chamber of compression refrigerators allows you to create different temperature conditions in individual places. In a regular refrigerator compartment the temperature is maintained from +2 to + 10 o C, in some types -0 o C, in the freezer compartment from -6 to -24 o C (quick freezing), in the low-temperature compartment pre-frozen products are stored.
[ Foreign-made compression refrigerators may have additional temperature compartments (“wine cellar”, ice maker, etc.). ]
Defrosting of refrigerators can be carried out in the usual way or using special systems (No-Frost, Frost-Free, etc.).
Appliances with the No-Frost system defrost automatically due to the fact that air is distributed throughout the refrigerator using special fans. However, this system creates:
1) increased level noise and constant air circulation;
2) dries food.
In refrigerators with a “crying” evaporator, the latter is located in the refrigerator compartment. When the compressor is running, freezing occurs, and when it stops, thawing occurs due to the heat generated by the products. Moisture is removed through special channels.
Refrigerators with the Frost-Free system use both a “crying” evaporator and a No-Frost system.
Range of compression refrigerators:
1) domestic – Stinol-205 (107;110) – Novolipetsk Iron and Steel Works; Atlant – 355-0 (151-01); Nord – 233 (226; 234) – Belarus and Ukraine.
2) foreign – Bosch KGS 3202; Siemens KGE 3501; Indesit GC 2322 W; Ariston - 216; Sharp RFSJ-55; Samsung SR-V-43.
In contrast to compression refrigerators, absorption-diffusion refrigerators do not have an electric motor with a compressor, so the device operates silently. The movement of the refrigerant (a solution of ammonia with hydrogen) is carried out due to heating (electric, gas, etc.).
Cooling of the chamber is achieved, as in compression refrigerators, by absorbing heat from it by boiling liquid ammonia in the evaporator.
The freezer compartment of such refrigerators maintains a temperature of about -5 o C.
Absorption refrigerators are small in size, operate silently, consume a small amount of electricity, and are relatively cheap.
The range is represented by devices domestic production(Hoarfrost, Morozko), as well as foreign companies - Whirpool, Electrolux, etc.
The production of cold in thermoelectric refrigerators is based on the Peltier effect, and refrigerators also do not have a refrigerant. The Peltier effect is that when direct current through dissimilar semiconductors (i.e. materials with different conductivity - exp: selenium with bismuth, tellurium with antimony) a temperature difference is created at the places of their junctions (connections); one semiconductor is heated (it is located outside the refrigerator), and the other is cooled by the same amount (it is located inside the refrigerator).
The temperature inside the refrigerator is up to +5 o C.
Thermoelectric refrigerators consume a lot of electricity and have a high price. They are used primarily as car refrigerators.
Assortment: Chaika, Voronezh, Krokha, etc.
II. According to climatic version:
1) (up to 40 o C) refrigerators for temperate climates (U);
2) (up to 45 o C) for tropical (T).
III. By number of refrigeration chambers:
Single chamber;
Two-chamber;
Three-chamber;
Multi-chamber.
IV. By temperature conditions in the low temperature compartment:
1) up to -6 o C;
2) from -6 to -12 o C;
3) from -12 to -18 o C;
4) from -18 to -24 o C.
V. At the installation location:
1) floor-standing in the form of a cabinet (W);
2) floor in the form of a table (C);
3) built-in desktop (H);
4) block-built (B);
5) portable.
VI. By difficulty group – from 0 to 5.
VII. By comfort level:
1) refrigerators with ordinary comfort;
2) with increased comfort (automatic defrosting; automatic door closing (if not closed at an angle of up to 10 o), light indication of the operating mode, device for cooling and dispensing drinks, computer control and monitoring system, clock-timer, sound alarm open door and etc.).
VIII. According to the internal volume of the chamber:
In the marking of refrigerators, the total volume in liters is indicated by numbers separated by a fraction, the numerator is the total volume, the denominator is the volume of the low-temperature mode.
IX. Based on materials of manufacture: metal, plastic, etc.
X. By the nature of the coating and finishing.
XI. By model: model number – two digits, modification number – a digit separated by a hyphen).
Refrigerator markings contain:
1) brand – Stinol;
2) difficulty group (0-5);
3) model serial number (two digits);
4) serial number of the modification (digit separated by a hyphen);
5) type of refrigeration device (compression);
6) number of cameras;
7) total volume;
8) nature of installation (floor-standing in the form of a cabinet);
9) standard number;
10) temperature in the lower temperature compartment.
In foreign models of refrigerators, the level of energy consumption is indicated, which is reflected in the letters: A, B and C - very economical, D - economical, E, F and G - with high energy consumption.
Classification of household refrigerators
Modern household refrigerators and freezers are complex Appliances working in specific conditions - in residential (kitchen) premises, therefore they are subject to high requirements: operation in automatic mode; minimum noise level; high level of reliability; complete safety of operation; perhaps small dimensions with a certain useful capacity, low cost and low operating costs.
According to the type of refrigeration machine, household refrigerators are compressor (cooled by a compressor refrigeration machine), absorption (cooled by an absorption refrigeration machine) and semiconductor (cooled by semiconductor batteries), and freezers - compressor and absorption.
Compressor refrigerators make up a significant share in the range of household refrigeration equipment - over 90%.
Based on the installation method, refrigerators are divided into floor-standing, wall-mounted and built-in.
Floor-standing refrigerators, installed on the floor of a room, are the most widespread type of refrigerators both in our country and abroad. Among them are models made in the form of a table; their height is the same as kitchen tables- 850 mm, and on top there is a made of special type plastic serving surface for placing kitchen utensils and products. Wall-mounted refrigerators, suspended from the wall of the room, do not take up floor space, which is important for small apartments
Built-in refrigerators are devices that are part of the design of a furniture block and are enclosed in a common shell with it. The block can be a kitchen or living room, such as a sideboard and a bar.
According to climatic design, refrigerators are divided into products of versions U and T. The first refrigerators are intended for use in areas with a temperate climate, i.e. in an area where the average of the annual absolute maximum air temperatures does not exceed 40 ° C, and the average of the minimums is below - 45 ° C. Products of execution U, used in residential premises, must provide the required parameters at an ambient temperature of 10 to 35 ° C GOST 16317-70 “Household Electric Refrigerators” provides for a narrower range of climatic factors: 16-32° C. Typically, for products of execution U, the upper limit value is taken to be 40° C.
Refrigerators of the T version are used in areas with a tropical climate, which include the Near and Middle East, India, Indonesia, Vietnam, a significant part of Africa and Latin America, Cuba, the southeastern and far western United States and several other areas. In Russia, tropical-style refrigerators are manufactured for export to these countries. For products of design T, used in residential premises, the maximum and operating values of ambient temperatures are the same: from 10 to 45°C; Established by the International Organization for Standardization (ISO) and CMEA temperature Range from 18 to 43°C. Tropical-style refrigerators are subject to increased requirements regarding the materials used, protective coatings, grounding, cabinet sealing and automation partings.
Based on functionality, refrigerators are distinguished for storing fresh food and fresh and frozen food. Appliances for storing fresh food do not have a low-temperature compartment. They are produced in small quantities in some countries. The possibility of storing frozen products is ensured only if the temperature in the low-temperature compartment is maintained no higher than - 6°C; The lower the temperature in the compartment, the longer the shelf life.
In accordance with international and domestic standards, it is customary to divide refrigerators into three categories: for short-term (several days) storage of frozen food - a temperature not higher than - 6 ° C; for medium-term storage (up to two weeks) - temperature no higher than - 12°C; for long-term storage (up to three months) - temperature no higher than - 18°C. Refrigerators are marked accordingly with one, two or three stars. Models with two and three stars are called two-temperature. In the USA, Canada and Australia, star marking is not used. According to the standards of these countries, two-temperature refrigerators must provide a temperature in the low-temperature compartment no higher than - 15 ° C.
By design, two-temperature refrigerators are single-chamber, double-chamber and multi-chamber. In two-chamber rooms there is a heat-insulating partition between the low-temperature and positive compartments; Each compartment is equipped with a separate door. Multi-chamber refrigerators have several (at least three) chambers with separate doors for storing various products.
Air circulation in the chambers can be carried out naturally or with the help of a fan, or in combination: in a low-temperature chamber by forced means, and in a positive chamber by natural means.
Refrigerators with natural air circulation in the chamber may have one ( conventional design) or two evaporators (design with a “crying” evaporator).
In models with natural air circulation, the low-temperature chamber is located at the top; in refrigerators with forced circulation it can also be placed at the bottom or next to the positive side.
Refrigerators also differ in the method of defrosting the evaporator: they use manual defrosting, semi-automatic and automatic (partially or completely). In the first method, the consumer himself determines the moment of the beginning and end of the process, and also manually removes melt water. With semi-automatic - the consumer determines only the beginning of defrosting, the end of the process is automatic; melt water is removed manually or automatically through the drainage system. Defrosting is automatic if the process is controlled and melt water is removed without the participation of the consumer.
Partially automatic defrosting is the automatic defrosting of one of the two cooling surfaces. For example, the positive compartment evaporator is defrosted automatically every cycle, while the low temperature compartment evaporator is defrosted manually every few months. Fully automatic defrosting is the automatic defrosting of all cooling surfaces.
The defrosting process can be fully automated only in refrigerators with forced air circulation; in other designs the use automatic system defrosting (due to its frequent operation) would lead to spoilage of frozen food.
Three methods are used to heat the evaporator during defrosting: with ambient air; hot freon steam supplied by the compressor to the evaporator, bypassing the condenser; electric heater. When defrosting manually, natural heating with ambient air is used, when defrosting semi-automatically and partially automatically, all three types of heating are used. Natural heating of the evaporator in the case of partially automatic defrosting occurs during the non-operating part of each cycle. With fully automatic defrosting, intensive heating of the evaporator with hot freon steam or an electric heater is used.
The adopted cooling system, i.e. the presence of one or two evaporators, natural or forced air circulation, largely determines the operational and design features refrigerators. Therefore, later in this chapter we will consider (as the main types) refrigerators with one evaporator, including two-temperature refrigerators, refrigerators with two evaporators, as well as refrigerators with forced air circulation.
According to GOST 16317-87, household refrigerators are divided according to the method of obtaining cold into:
compression (K); absorption (A);
by installation method:
floor-standing cabinet type (W); apole table type (C);
by number of cameras on:
single-chamber; two-chamber (D); three-chamber (T).
Two chamber refrigerators have a heat-insulating partition between the LTO and the plus compartment.
Based on their ability to operate at maximum ambient temperatures, refrigerators are divided into classes:
UHL - not higher than 32 0 C;
T - not higher than 43 0 C.
The chambers of refrigeration appliances are divided into:
chamber for storing fresh vegetables and fruits;
refrigeration chamber for cooling and storing chilled products;
low-temperature chamber for storing frozen foods (NTK);
a freezer for freezing and storing frozen foods (MK);
a universal chamber for storing food in fresh, chilled or frozen condition.
Single-chamber refrigerators are divided into:
according to the availability of scientific and technical information on:
single-chamber with NTO;
single-chamber without NTO;
by temperature in NTO at:
with a temperature not higher than -6 0 C;
with a temperature not higher than -12 0 C;
with a temperature not higher than -18 0 C.
The temperature in the NTO is not higher than - 6 0 C ensures short-term storage for several days, not higher than - 12 0 C for two weeks and not higher than - 18 0 C for three months.