The device and principle of operation of refrigeration units. Household refrigerators: classification, modern range of compression refrigerators Door opening indication

Comparative characteristics of the range of cotton and linen fabrics and the direction of its development

Assortment of cotton and linen fabrics

All fabrics, depending on the raw materials used, are divided: cotton (cotton), linen, silk, woolen.

Cotton fabrics are distinguished by a variety of design as a result of the use of various weaves and types of finishes, as well as good hygienic properties, wear resistance, lightness, and beautiful appearance. Most 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;

According to the production method: multi-colored and melange;

By the nature of the finish: severe, bleached, plain-dyed, printed;

By groups: chintz, coarse calico, linen, satin, dress, clothing, lining, teak, pile, shawl, blanket;

By appointment:

1) linen fabrics (coarse calico, calico, special fabric);

2) dress and shirt fabrics (chintz, coarse calico, satin);

3) dress fabric: summer subgroup (fabric chio - chio san), demi-season (spark), winter (flannel, bike);

4) pile fabrics (velveteen, velvet);

5) lining fabrics;

6) suit coats;

7) towel, 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, woolen fabrics come in grades 1 and 2, silk - grades 1,2,3

They are placed on undercarriages. 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 breath-permeable, and heat-conductive. Linen fabrics are indispensable for tailoring summer clothes, they are highly wear-resistant and wash well. The disadvantage of linen fabrics is their high wrinkling.

Classification:

In composition: linen and semi-linen;

By weave: linen, satin, finely patterned, coarsely patterned;

Finishing: severe, bleached, boiled, multicolored, melange;

By appointment: linen, costume and dress, furniture and decorative, beading, linen, piece goods;

By width: canvases, narrow, wide canvases;

By groups: (16 groups):

1) linen (cloths and canvases)

2) costume and dress (linen and semi-linen fabrics)

3) furniture and decorative (drape, furniture, mattress, terrace fabrics)

4) fabrics special purpose(board, case, severe rough, mattress)

5) piece products (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 according to the method of "getting cold":

Compression refrigerators and freezers;

Absorption-diffusion refrigerators;

Thermoelectric refrigerators.

The most widely used compression refrigerators. In these refrigerators, heat is taken from the inner 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.

In absorption-diffusion refrigerators, ammonia is used 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 means that when a constant electric current through a thermoelement of two series-connected (soldered) materials with different thermoelectromotive force, 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 as follows:

K - compression;

A - absorption-diffusion;

FC - thermoelectric.

Refrigerators, according to the current standard, can be classified according to a number of other features, the main of which are the purpose, installation method, number of chambers, temperature in the low-temperature compartment, complexity group, etc.

By 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 food products;

Refrigerator-freezers - devices for storing chilled and frozen foods (they differ from two-chamber refrigerators big size low-temperature chamber - from 40 l, the presence of two independent refrigeration units).

According to the installation method, refrigerators are distinguished:

"SH" - floor in the form of a cabinet;

"C" - floor in the form of a table;

"H" - built-in;

"B" - block-embedded;

"side-by-side" - cameras are placed parallel in a vertical plane.

According to the number of refrigerated chambers, refrigerators are: 1; 2 (D); 3 (T) and multi-chamber (M).

According to the temperature in the low-temperature compartment, refrigerators are divided into 6 ° C intervals from -6 to -24 ° C (and lower), every 6 degrees is usually denoted 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 climatic version(according to the ability to work at maximum temperatures environment):

SN, N - not higher than 32°С;

ST - not higher than 38°С;

T - not higher than 43°C;

Freezers:

N - not higher than 32°С;

T - not higher than 43°C. The chambers that are part of the refrigerators can also be divided into types:

Chambers for storing vegetables and fruits - have high humidity;

Refrigeration chambers for storing chilled products;

Low-temperature chamber (NTC) - for storing frozen food products;

MK - freezer;

Universal camera - general purpose camera.

According to the degree of comfort, refrigerators of ordinary and superior comfort are distinguished. Refrigerators of superior comfort 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 refrigerator compartment or part thereof;

A device for cooling drinks with their issuance without opening the door;

Signaling about operating modes;

Forced device automatic closing doors when opening them by 10 °;

Door opening angle limiter;

Ensuring the rearrangement of shelves with a height interval of not more than 50 mm or extension of 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 provides for other elements of comfort.

Depending on the functions performed, refrigeration appliances are divided into complexity groups from 0 to 5. The zero group is assigned to the most complex models, and 5 to the least complex.

Compression refrigerators occupy 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 to work, refrigerant vapor (freon) flows from the evaporator to the compressor cylinder, where it is compressed by a piston. Compressed and superheated vapors under pressure are fed into the condenser.

In the Condenser, the refrigerant vapors are cooled by the ambient air, condense, and turn into a liquid state. The liquid refrigerant flows through the capillary tube to the evaporator, the refrigerant pressure drops. In the evaporator, the liquid refrigerant boils at low pressure, turns into vapor and absorbs heat from the refrigerator compartment. The vaporized refrigerant enters the compressor again and the cycle repeats. The thermostat maintains the set temperature. The evaporator is covered with a "snow coat" during operation. If the layer of frost is more than 5 mm, this leads to more energy consumption and warming of the low-temperature compartment.

Parameters of compression refrigerators. Electrical parameters determine the quality of the functional properties of refrigerators. The total internal volume (measured in dm3 and in l) is the volume limited by the internal walls of the refrigerator with the door closed and removed removable elements. The total volume of refrigerators according to the standard is from 60 to 500 dm3.

The freezer volume indicates how much frozen food can fit in the freezer compartment.

The functional properties include the total energy consumption. For the consumer, this indicator is great importance because the fridge is open 24/7.

In Europe, since 1995, refrigerator manufacturers have been required to indicate their annual electricity consumption on a special information sticker. For clarity, each class of energy consumption is highlighted in color and denoted by letters - from A to G: A, B, C - very economical; D - intermediate; E, F, G - with high and very high power consumption. Energy consumption classes:

A 266-351 kW / year;

At 379-427 kW / year;

From 415-516 kW/year.

The ergonomic properties of refrigerators are determined by ease of use, the degree of comfort, the strength of shelves, pallets, dimensions, floor space, light and sound alarms matter.

The aesthetic properties of the refrigerator are the color solution, the proportionality of the forms of the refrigerator, the location of the chambers, the expressiveness of brand names.

The refrigeration unit must be safe in fire, sanitary (noise and vibration), electrical and mechanical terms.

A range of compression refrigerators. Compression refrigerators are single-, double- and multi-chamber. Such refrigerators are produced combined, such as "refrigerator-freezers". The range of refrigerators entering the trade includes a large number of models of different designs, various manufacturers: Atlant (Belarus), Electrolux (Sweden), Arston (Italy), Stinol, Nord, etc. Refrigerator markings: name, model symbol, ordinal number, type and amount of refrigerant, volume of the refrigerating chamber, date of issue.

The classification of devices of this group and the definition of types characterizing the functions performed by the product are given in GOST 30204-95, GOST 16317-87. The standard name of the group is "Household electrical refrigeration appliances".

Refrigeration appliances are divided according to their purpose into:

• - fridge. This is a thermally insulated cabinet of the appropriate volume with equipment, cooled by one or more refrigeration units and having one or more food storage compartments, at least one of which can store fresh food;
• - freezer. Thermally insulated cabinet with one or more freezer compartment, intended for freezing (from 32 ... 25 ° С to -18 ° С, depending on the climatic version of the device) and food storage; refrigerator household consumer trade
• - household refrigerator with freezer compartment. An electrical appliance that has one or more compartments for storing fresh food and one compartment for freezing and storing frozen food at a temperature of -18 ° C and below;
• - a chamber for storing frozen foods. An electrical appliance in which one or more compartments are provided, and the temperature of the products placed in them is equal to or lower than -18 ° C.

According to the method of obtaining cold on:

• - compression;
• - absorption-diffusion;
• - thermoelectric.

By installation method:

• - floor vertical type"cupboard". Access to the compartments of the refrigeration appliance is carried out from the front side;
• - horizontal type "chest". Access to the refrigerator is from above.

The main advantages of horizontal freezers are large usable volume and invariability temperature regime when extracting the next portion of products. With a horizontal design of the refrigeration appliance, as a result of natural temperature stratification, the coldest air is at the bottom.

By the number of cameras on:

• - single-chamber;
• - two-chamber;
• - three-chamber;
• - multi-chamber.

The refrigeration appliance chamber is an isolated interior space of the appliance with a separate outer door and cooling elements.

According to the ability to work at maximum ambient temperatures:

• - SN, N (at a temperature not exceeding 32 °C);
• - ST (temperature must not exceed 38 °C);
• - T (at a maximum temperature not exceeding 43 ° C).

Refrigerators vary:

By the presence of a low-temperature compartment (LTO) with LTO and without LTO.

By temperature in NTO:

• - with a temperature not higher than -6 C (marked with one asterisk *);
• - temperature not higher than -12 C (marked with two asterisks**);
• - temperature not higher than -18 C (marked with three asterisks***).

The chambers of refrigeration appliances are divided by purpose into:

• - chamber for storing fresh vegetables and fruits Fresh Food Storage Compartment;
• - a refrigerator for cooling and storing refrigerated products Refrigerator;
• - low-temperature chamber for storage of frozen products Frozen Food Storage Cabinet;
• - a freezer for freezing and storing frozen food Freezer, on the door of which the symbol **** is applied;
• - a universal chamber for storing food in fresh, chilled or frozen states.

Depending on the functions performed, refrigeration appliances are divided into complexity groups (0 ... 5). Complexity groups are determined by the functions performed by the refrigeration appliance and their design features:

• - temperature in the NTO;
• - defrosting products with a special device;
• - automatic or semi-automatic evaporator defrosting;
• - the presence of alarms, etc.

According to the features of equipping with comfort elements, refrigerators with ordinary and superior comfort are produced. The set of comfort elements in the models of the modern assortment is very diverse, so it is quite difficult to determine which model is more comfortable.

The nomenclature of the minimum necessary comfort elements includes automatic temperature control; device for making and issuing ice cubes; automatic defrosting of the refrigerator compartment evaporator; oil heating device; device for dispensing chilled drinks; the possibility of re-hanging the door for left-hand and right-hand opening; movement of the device on the floor with the help of roller supports; the possibility of rearranging the shelves in the refrigerator chamber or in its individual sections with an interval of no more than 50 mm; extension of the loaded shelf to a distance of at least 50% of its depth with fixation with a special element; light and sound signaling of operating modes; the presence of an opening angle limiter or a shock absorber that prevents the refrigerator from hitting the wall; door open alarm for more than 30s; the presence of a serving or installation plane, etc.

Non-standard features of the classification of refrigeration appliances that are relevant in the formation of the range include:

The location of the cameras with more than two:

• - upper and lower;
• - side;
• - mixed.

Number of compressors:

• - one;
• - two.

The number of "degrees of freedom" or the number of products combined in a single unit with a refrigerator:

• - fridge;
• - freezer;
• - microwave sublimator;
• - thermostat for storing vegetables;
• - cabinet for drying fruit;
• - defroster (the set may be different).

Evaporator defrosting method:

• - automatic (thawing of the snow cover on the surface of the evaporator of the chamber with a positive temperature during the shutdown of the refrigeration unit);
• - semi-automatic active defrosting (switching on heating element for defrosting NTO);
• - natural;
• - without snow cover freezing - No Frost based on forced air circulation system;
• - combined.

In refrigerators with semi-automatic defrosting, there is a corresponding marking on the HTO door.

Installation and operation method:

• - free-standing stationary;
• - built-in;
• - block-embedded;
• - portable.

Source of power:

• - from an alternating current source;
• - from an independent power source.

Gross volume.

When classifying refrigerators, the material of the shelves is taken into account; color graphic solution for the exterior design and internal elements of the refrigeration appliance; trademark; energy efficiency classes of devices; environmental properties of the refrigerant and other features.

By design and principle of operation, refrigerators of compression and absorption-diffusion types have much in common and are based on the removal of heat from the interior of the cabinet, where a low temperature has been established, to an environment with a higher temperature.

Structurally, the refrigerator includes a cabinet and a refrigeration unit.

On the commodity market, the range of refrigerator models is conditionally divided into “Asian” (low wide (more than 600 mm) models with rounded shapes and the location of the freezer at the top), typically “American” (large side by side refrigerator with freezer and refrigerator doors located side by side and interlocking sides) and "European".

"European" is recognized as a tall and narrow refrigerator with a freezer at the bottom. This layout is more rational - the device occupies a smaller area, the consumer uses the freezer compartment less often; warm, moist air is less likely to enter the freezer. The "American" models are characterized by the presence of a device for dispensing chilled drinks.

A useful element in the equipment of refrigeration appliances is the presence of a cold accumulator, which allows maintaining a steady temperature during a power outage for 9-24 hours. Cold accumulators can be used independently of the refrigerator.

The design of modern refrigeration appliances is determined both by the changing fashion ideas of consumers, and by new technical solutions that make changes in appearance appliances. In refrigerators with a wide frontal surface, in order not to completely open the inner chamber, doors with vertical and horizontal division into two parts are used.

At present, as well as a few years ago, the trends in the displacement of clear rectangular shapes continue in the design. Models are produced with smooth rounded shapes, with in-depth original hand grips on the front surface of the door in the form of tulip petals with shiny edging.

Italian manufacturers present the most unexpected solutions. This is the design of the Marine series (traditional shelves are replaced by shelves stylized as fishing nets); multi-color panels on the front panels with stars or the sun glowing in the dark. Nostalgie or Old Timer styles (60s style) are in fashion: a rounded top, a “pot-bellied” door, an old-fashioned metal handle similar to a car; product color - any, except white. At color solution models, the theory is taken into account, according to which, through the human subconscious, yellow, red, beige colors increase appetite, and black, green, gray, on the contrary, reduce it. There are models whose color is focused on the temperament of a person. The design in Hi-tech style, or modern, offers a front surface finish or the execution of the entire outer cabinet in stainless steel or 21st century material.

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: functioning in automatic mode; minimum noise level; high level reliability; complete safety of operation; perhaps small overall 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%.

According to the installation method, refrigerators are divided into floor, wall and built-in.

Floor-standing refrigerators installed on the floor of a room are the most popular 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 serving surface made of a special type of plastic 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 - devices included in the design of the furniture unit and 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 the climatic design, refrigerators are divided into U and T products. The first refrigerators are designed for operation in areas with a temperate climate, i. in the territory where the average of the annual absolute maxima of air temperature does not exceed 40 ° C, and the average of the minimums is below - 45 ° C. U products operated 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. Usually, for products of execution U, the upper limit value is assumed to be 40 ° C.

Refrigerators of execution T are operated in regions with a tropical climate, which include the Near and Middle East, India, Indonesia, Vietnam, a significant part of Africa and Latin America, Cuba, the southeast and far west of the United States and a number of other regions. In Russia, tropical refrigerators are manufactured for export to these countries. For products of version T, operated in residential premises, the limiting and operating values ​​of ambient temperatures are the same: from 10 to 45 ° С; The International Organization for Standardization (ISO) and the CMEA set the temperature range from 18 to 43°C. Refrigerators in tropical design are subject to increased requirements regarding the materials used, protective coatings, grounding, sealing of the cabinet and automation partings.

On a functional basis, refrigerators are distinguished for storing fresh food and fresh and frozen food. Fresh food storage units do not have a freezer compartment. They are produced in small quantities in some countries. The possibility of storing frozen products is provided only if the temperature in the low-temperature compartment is maintained at a temperature not higher than -6°C; the lower the temperature in the compartment, the longer the shelf life.

In accordance with international and domestic standards, refrigerators are divided into three categories: for short-term (several days) storage of frozen foods - the temperature is not higher than - 6 ° C; for medium-term storage (up to two weeks) - the temperature is not higher than - 12 ° C; for long-term storage (up to three months) - the temperature is not higher than - 18 ° C. Accordingly, refrigerators are marked with one, two or three stars. Models with two and three stars are called two-temperature. In the US, Canada and Australia, asterisk markings are not used. According to the standards of these countries, two-temperature refrigerators must ensure that the temperature in the low-temperature compartment does not exceed -15 ° C.

By design two-temperature refrigerators are single-chamber, two-chamber and multi-chamber. In two-chamber there is a heat-insulating partition between the low-temperature and positive compartments; each compartment has 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 combined: in the low-temperature chamber by force, and in the positive chamber - naturally.

Refrigerators with natural circulation air in the chamber can have one (conventional design) or two evaporators (design with a "weeping" 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 below or next to the positive one.

Refrigerators also differ in the way the evaporator is defrosted: they use manual defrosting, semi-automatic and automatic (partially or completely). In the first method, the consumer himself determines the start and end of the process, and also manually removes the 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 drainage system. Defrosting is automatic if the process is controlled and the defrost 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 manually defrosted 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 of an automatic defrosting system (due to its frequent operation) would lead to spoilage of frozen products.

There are three ways to heat the evaporator during defrosting: by ambient air; hot steam of freon supplied by the compressor to the evaporator, bypassing the condenser; electric heater. Manual defrosting uses natural ambient air heating, while semi-automatic and semi-automatic defrosting uses all three types of heating. Natural heating of the evaporator in case of partially automatic defrosting takes place 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.

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 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 way of installation on:

floor type cabinet (W); apole table type (C);

by the number of cameras on:

single-chamber; two-chamber (D); three-chamber (T).

In two chamber refrigerators there is a heat-insulating partition between the NTO and the positive compartment.

According to the ability to work at maximum ambient temperatures, refrigerators are divided into classes:

UHL - not higher than 32 0 С;

T - not higher than 43 0 C.

The chambers of refrigeration appliances are divided by purpose into:

chamber for storing fresh vegetables and fruits;

refrigerating chamber for cooling and storing chilled products;

low-temperature chamber for the storage of frozen foods (NTC);

freezer for freezing and storing frozen foods (MK);

a universal storage compartment for keeping food fresh, chilled or frozen.

Single-chamber refrigerators are divided into:

by the presence of NTO on:

single-chamber with NTO;

single-chamber without NTO;

by temperature in NTO on:

with a temperature not higher than -6 0 С;

with a temperature not higher than -12 0 С;

with a temperature not higher than -18 0 С.

The temperature in the NTO is not higher than - 6 0 С for short-term storage for several days, not higher than - 12 0 С for two weeks and not higher than - 18 0 С for three months.

Types of refrigeration units according to the principle of operation:

• compression
• absorption
• Thermoelectric
• With vortex coolers

The device and principle of operation of the compression refrigerator
The theoretical basis on which the principle of operation of refrigerators is built is the second law of thermodynamics. The cooling working fluid (refrigerant) in refrigerators performs the so-called reverse Carnot cycle. In this case, the main contribution to the heat transfer is made by a change in the thermodynamic state of the refrigerant not in the Carnot cycle, but in phase transitions - evaporation and condensation of the refrigerant. In principle, it is possible to use only the Carnot cycle in the refrigeration cycle, but in this case, to achieve high cooling capacity, either a compressor that creates a very high pressure or a very large heat exchange area in the cooling and heating heat exchangers is required.

The main components of the refrigerator are:

• a compressor that creates the necessary pressure difference;
• an evaporator that takes heat from the internal volume of the refrigerator;
• a condenser that gives off heat to the environment;
• thermostatic valve that maintains the pressure difference by throttling the refrigerant;
• refrigerant - a substance that transfers heat from the evaporator to the condenser.

The compressor sucks in the refrigerant in the form of vapor from the evaporator, compresses it (in this case, the temperature of the refrigerant rises) and pumps it into the condenser, where the refrigerant condenses into a liquid, giving off the heat of condensation to the external environment.
Hermetic reciprocating motor-compressors are used in household refrigerators. In these compressors, the electric motor is located inside the compressor housing, which prevents leakage of refrigerant through the shaft seal. An elastic suspension of the motor-compressor is used to absorb vibrations. The suspension of the motor-compressor can be external, when the entire housing of the motor-compressor is suspended on springs, or internal, when only the compressor motor is suspended inside the housing.
In modern household refrigerators, external suspension is not used, since it absorbs compressor vibrations worse, and which is also more noisy. To lubricate the rubbing parts of the compressor and electric motor, special refrigerant oils with a low pour point are used. Oil and refrigerant dissolve well in each other.
In the condenser, the refrigerant heated as a result of compression cools down, giving off heat to the external environment, and at the same time condenses, that is, it turns into a liquid entering the capillary.

In household refrigerators, finned-tube condensers are most often used; steel wire or perforated steel sheet is used as fins. Heat removal from condensers is usually natural - due to convection and thermal radiation; in high-performance and industrial refrigerators, forced cooling of the condenser with fan air or water is used.

Liquid refrigerant under pressure through a throttling hole (capillary or thermostatically controlled expansion valve) enters the evaporator, where, due to a sharp decrease in pressure, the liquid evaporates. At the same time, the refrigerant takes away heat from the inner walls of the evaporator, the extracted heat is spent on the heat of boiling of the liquid, due to which the refrigeration space of the refrigerator, where the evaporator is located, is cooled.

Evaporators of household refrigerators are most often sheet-pipe, welded from a pair of aluminum sheets with internal channels for the passage of the refrigerant. The freezer evaporator is often the case, while the refrigerator evaporator (in refrigerators with two evaporators) is located on the rear wall of the compartment.

Thus, in the condenser, the refrigerant under the influence high pressure condenses and turns into a liquid state, releasing heat, and in the evaporator, under the influence of low pressure, it boils and turns into a gaseous state, absorbing heat.

A thermostatic expansion valve is required to create the necessary pressure difference between the condenser and evaporator for the heat transfer cycle to take place. It allows you to correctly (most completely) fill the internal volume of the evaporator with boiling refrigerant. The flow area of ​​the valve changes as the heat flow in the evaporator decreases; as the temperature in the cold chamber decreases, the flow rate of the circulating refrigerant decreases.

In domestic refrigerators, a capillary is most often used instead of a temperature-controlled expansion valve. It does not change its cross section, but throttles a certain amount of refrigerant, depending on the pressure at the inlet and outlet of the capillary, its diameter, length and type of refrigerant.

The purity of the refrigerant is of great importance: water and impurities can clog the capillary or damage the compressor. Impurities can form as a result of corrosion of the internal walls of the refrigerator piping, and moisture can enter when filling the refrigerator, or penetrate through leaks (especially in refrigerators with an open compressor). Therefore, when charging, tightness is carefully observed; before charging with refrigerant, the circulation circuit is evacuated. Each refrigerator has a filter-drier, which is installed in front of the capillary.

A simple counterflow heat exchanger is also commonly used to lower the temperature of the liquid refrigerant from the condenser before it enters the evaporator. As a result, an already cooled liquid refrigerant enters the evaporator, which then cools even more in the evaporator, while the refrigerant coming from the evaporator is heated before entering the compressor and condenser. This improves the thermal efficiency and capacity of the refrigerator and prevents liquid refrigerant from entering the compressor.

Refrigerator diagram
1 - Motor-compressor.
2 - Injection tube.
3 - Condenser (or capacitor).
4 - Filter-drier.
5 - Capillary tube
6 - Refrigeration chamber evaporator.
7 - Freezer evaporator.
8 - Return pipeline.

The principle of operation of the absorption refrigerator
Just like in a compression refrigerator, in an absorption refrigerator, the cooling of the working chamber occurs due to the evaporation of the refrigerant (most often ammonia). Unlike a compression refrigerator, the refrigerant circulates by dissolving (absorbing) it in a liquid, usually water. Up to 1000 units of water can be dissolved in one unit of water. volume of ammonia. A saturated ammonia solution from the absorber enters the generator (desorber), and then into the reflux condenser, where it decomposes into ammonia and water. Gaseous ammonia is liquefied in the condenser and again enters the evaporator, and the water purified from ammonia enters the absorber.
A variety of devices, such as jet pumps, can be used to circulate water in the system, eliminating the need for moving parts. A gas that is inert to the components of the system, such as hydrogen, is also added to the refrigeration system. In this case, the pressure in the entire system is almost the same, and the evaporation of the refrigerant occurs due to a change in partial pressure.

In addition to ammonia and water, other pairs of substances can be used - for example, a solution of lithium bromide, acetylene and acetone. The advantages of absorption refrigerators are noiseless operation, the absence of moving mechanical parts, the ability to work from heating by direct combustion of fuel, the disadvantages are poor specific cooling performance per unit volume, sensitivity to position in space, and also fragility: the pipelines of such a refrigerator are relatively quickly clogged with corrosion products. In addition, the refrigeration unit contains toxic ammonia and combustible hydrogen. Such refrigerators are practically not used in modern apartments, but are common in places where there is no 24-hour access to electricity: for example, in mobile homes, where they are powered by electricity in campsite parking lots, and on the way they are powered by burning natural gas. In addition, absorption units are often used in industrial refrigerators in cases where it is more profitable to use the energy of gas combustion, rather than electricity. Their most efficient use in industry is in conjunction with cogeneration plants, which makes it possible to utilize excess heat and increase efficiency. In this case, we are talking about the so-called trigeneration. In addition, absorption machines allow the use of waste heat.

The principle of operation of a thermoelectric refrigerator
The operation of a thermoelectric refrigerator is based on the Peltier effect - when a current passes through the contact of two dissimilar conductors in the direction of the contact potential difference, thermal energy is transferred so that one of these "dissimilar" conductors is cooled, and the second is heated due to thermal energy from the first and electrical energy of the passed electric current. The refrigerator on Peltier elements is silent, reliable and durable, but it has not received wide distribution due to the high cost of cooling thermoelectric elements. Another disadvantage is the dependence of cooling capacity on the ambient temperature. However, cooler bags, small car coolers and coolers drinking water often made with cooling from Peltier elements.

The principle of operation of the refrigerator on vortex coolers
Cooling is carried out by expanding the air pre-compressed by the compressor in special blocks vortex coolers. It has not received distribution due to the high noise level, the need to supply compressed (up to 10-20 atm) air and its very high consumption, low coefficient useful action. Advantages - safety (since electricity is not used and there are no moving mechanical parts, no dangerous chemical compounds in the structure), durability, reliability.