It is difficult to imagine a modern apartment without a refrigerator. Everyone knows that a refrigerator retains cold inside itself, so food stored in it does not spoil for a long time. How does a refrigerator work?
The refrigerator has 4 main components:
1. Refrigerant- a substance that circulates and transfers heat. Freon gas is used as a refrigerant.
2. Compressor- a motor that operates on the principle of a pump and drives the refrigerant in a circle.
3. Capacitor- through it the heat goes out into the environment. The condenser is a grill on the back wall of the refrigerator.
4. Evaporator- it takes heat from the refrigerator. Typically the evaporator is the inner wall of the refrigerator.
Main parts of a household refrigerator:
1 - evaporator, 2 - condenser, 3 - filter drier, 4 - capillary, 5 - compressor
The compressor draws refrigerant from the evaporator. The refrigerant is in a vapor state at this moment. The compressor pumps it under pressure into the condenser. The refrigerant is compressed under pressure, that is, it changes from a gaseous state to a liquid. At the same time, its temperature rises. Hot gas, passing through the condenser pipes, gives off heat to the surrounding space and, as a result, cools to room temperature.
The refrigerant then enters the evaporator through a very narrow opening (capillary). Its pressure decreases sharply, and due to this, the refrigerant evaporates - it boils, turning into steam. At the same time, it cools down greatly. As a result, it removes heat from the walls of the evaporator, and the evaporator, in turn, cools the interior of the refrigerator and the food contained in it.
Thus, the refrigerant works in a cycle: in the condenser, under the influence of high pressure, it condenses and turns into a liquid state, highlighting heat, and in the evaporator under the influence of low pressure it boils and turns into a gaseous state, absorbing warm.
Scheme of operation of a compression refrigerator
1 - condenser, 2 - capillary, 3 - evaporator, 4 - compressor
The refrigerator must have a thermostat, with which the cooling temperature of the refrigerator compartment is set. When this temperature is reached, the thermostat opens the electrical circuit and the compressor stops.
After some time, the temperature in the refrigerator begins to rise again (under the influence of the environment). Then the contacts of the thermostat close and the electric motor of the motor-compressor starts using a protective starting relay. The entire cycle is repeated from the beginning until the temperature in the refrigerator drops again to the desired value.
That's why we hear the refrigerator start to "rumble" from time to time, and then go quiet again - this is the compressor motor turning on and off.
In the refrigerant circulation diagram in the very first picture, you probably noticed one more link - the filter drier. It is needed to clean and dry the refrigerant that passes through it. The filter drier is a cylinder filled with a substance that absorbs moisture (silica gel or zeolite).
So, the refrigerator is designed in such a way that it doesn't cool air in the chamber, and picks up heat comes out of it and releases it into the environment. This is ensured by the pressure difference in the condenser and evaporator of the refrigerator. The refrigerant moves from a high-pressure area, where it turns into a liquid (condenses), to a low-pressure area, where the refrigerant's pressure decreases and it turns into vapor (evaporates).
The article uses materials from the site secureforms.danfoss.com and
In a two-chamber refrigerator, various automation schemes are used to obtain low temperatures (in the freezer compartment or in the frozen food storage compartment) and above-zero temperatures (in the fresh chilled food storage compartment). The simplest automation scheme is considered to be one with a common control device.
Automation diagram for a two-chamber home refrigerator with a common control device: NTI-low-temperature evaporator, VTI-high-temperature evaporator, RU-control device, KM-compressor, Tr-thermoregulator.
The refrigerant is supplied through one control device, first to the evaporator of the low-temperature compartment, and then to the evaporator of the high-temperature chamber. With this method of feeding evaporators with refrigerant, incomplete evaporation of the agent occurs in the evaporator of the low-temperature chamber and the vapor-liquid mixture of the refrigerant enters the evaporator of the high-temperature chamber, where a higher temperature is maintained.
The operation of the compressor is controlled by a thermostat, the capillary of which is in contact with the evaporator of low- or high-temperature chambers. In the latter case, a large temperature difference occurs in the freezer compartment. To reduce the drop on the evaporator near the thermostat capillary, a temperature stabilizer is often installed, which is an electric heater with a power of 6-10 W.
PO-starting winding of the engine, RO-working winding of the engine, ZR-protective relay, TC-temperature stabilizer, Tr-thermostat, H-anti-condensation resistance, El-electric lamp, V-lamp switch.
The electrical circuit for the automation of a two-chamber refrigerator with a temperature stabilizer is similar to the circuit. In contrast to the electrical circuit for the automation of a single-chamber refrigerator, when the thermal relay contacts open, the temperature stabilizer turns on, heats the capillary of the thermal relay, reducing the duration of the compressor's standstill. In this case, the difference between the on and off temperatures decreases. Constantly switched on anti-condensation electric heater with a power of 15 W. protects against condensation falling onto the outer wall of the cabinet chamber near the doorway of the freezer.
NTI-low-temperature evaporator, VTI-high-temperature evaporator, RU-regulating device, KM-compressor, Tr-thermoregulator, coolant-liquid separator, Kd-condenser.
The automation circuit with a common control device and a liquid separator prevents liquid freon from entering the compressor. After throttling in the control device in the evaporator of the low-temperature chamber, incomplete evaporation of the refrigerant occurs and a vapor-liquid mixture enters the liquid separator. Particles of the liquid agent, separated from the vapor, are deposited in the low part of the separator, and then enter the evaporator of the high-temperature chamber, where the liquid completely boils away. The refrigerant vapor from the evaporator and the upper part of the liquid separator is sucked off by the compressor.
The compressor is controlled by a thermostat, the capillary of which is pressed against the evaporator of the low-temperature chamber. With a scheme with one boiling point in two evaporators and two evaporators, maintaining different temperatures in the two chambers of the refrigerator is difficult.
The electrical automation circuit is similar to that of a two-chamber refrigerator with a temperature stabilizer. The difference is that the circuit does not have a temperature stabilizer.
Let's consider automation schemes for two-chamber refrigerators with different freon boiling temperatures in the evaporators.
NTI-low-temperature evaporator, VTI-high-temperature evaporator, RU-regulating device, KM-compressor, Tr-thermoregulator, Dr-throttle, Kd-condenser.
In an automation scheme with a common control device in front of the high-temperature evaporator (HTE) and a throttle in front of the low-temperature evaporator (LTE), the refrigerant is throttled in the control device and fills the HTE. By lowering the pressure in the throttle a second time “to itself,” the agent from VTI enters NTI. This scheme reliably ensures that the required temperatures are maintained in each chamber.
The electrical circuit of this refrigerator is similar
NTI-low-temperature evaporator, VTI-high-temperature evaporator, RU-regulating device, KM-compressor, Tr-thermostat, SV-solenoid valve, Kd-condenser, Tr1, Tr2-thermostats.
In an automation scheme with the supply of refrigerant to each evaporator through an independent control device, the operation of the compressor is controlled by a thermostat, the capillary of which is fixed to the low-temperature evaporator. The operation of the solenoid valve upstream of the high-temperature evaporator control device is controlled by another thermostat.
The electrical diagram of such a refrigerator is shown below.
PO-starting winding of the engine, RO-working winding of the engine, PR-starting relay, ZR-protective relay, Tr1-temperature regulator of the cooling chamber, Tr2-temperature regulator of the freezing chamber, SV-solenoid valve, H-anti-condensation resistance, El-electric lamp, Vl- lamp switch.
When the temperature of the evaporator and, accordingly, the air in the cooling chamber decreases, the contacts of the thermostat open, turning off the solenoid valve. The supply of refrigerant to the high-temperature evaporator is stopped, but the compressor continues to operate if the contacts of the low-temperature evaporator thermostat are closed.
When the temperature of the evaporator and, accordingly, the air in the freezer chamber decreases, the contacts of the second thermal relay break the power supply circuit of the compressor motor. The circuit also has a permanently switched on anti-condensation electric heater.
The most successful, in my opinion, is the automation scheme of a two-chamber refrigerator with a common control device and a solenoid valve.
NTI-low-temperature evaporator, VTI-high-temperature evaporator, Dr-throttle, coolant-liquid separator, RU-regulating device, KM-compressor, SV-solenoid valve, Kd-condenser, Tr1, Tr2-thermostats.
The circuit uses a common control device and a liquid separator. There is a downstream choke in front of the high temperature evaporator. When the solenoid valve is closed, the refrigerant is throttled in the control valve and fills the liquid separator. Then passing through the throttle, the refrigerant fills the evaporator in the cooling chamber, from where it enters the evaporator of the freezer.
When the VTI has cooled to the set temperature, its thermostat turns on the solenoid valve. The refrigerant, overcoming less hydraulic resistance compared to the throttle, enters the NTI.
When the low-temperature evaporator cools to the set temperature, its thermostat stops the compressor.
Below are technological and electrical diagrams of a two-chamber refrigerator with automatic defrosting of evaporators by refrigerant vapor.
a-technological diagram: NTI-low-temperature evaporator, VTI-high-temperature evaporator, RU-regulating device, KM-compressor, Tr-thermoregulator, SV-solenoid valve, CD-condenser, En-electric heater.
b-electrical diagram: PO-starting winding of the engine, RO-working winding of the engine, PR-starting relay, ZR-protective relay, Tr-thermostat, SV-solenoid valve, H-heater, H1-temperature stabilizer, DF-defrostator.
The solenoid valve is automatically turned on when the defrostator contacts are closed, which occurs periodically with the help of a 2.5 W defrost electric motor, constantly connected to the network. At the same time, the electric heater turns on.
The refrigerant vapor compressed by the compressor, bypassing the condenser, through a solenoid valve through a special tube enters first the evaporator of the freezing chamber, and then into the evaporator of the cooling chamber and heats them up, causing the snow coat to melt. Freon vapors, giving off heat to the cold walls of the evaporator, condense. To avoid liquid agent entering the compressor, it is evaporated by an electric heater installed at the outlet of the VTI.
After the snow coat has thawed, the defrostor contacts are opened using an electric motor. This turns off the solenoid valve and the electric heater. This turns off the solenoid valve and the electric motor. The unit begins to operate in normal mode, controlled by a thermostat. The temperature stabilizer, located in the operating winding circuit of the compressor motor, turns off when the thermostat contact opens.
Types of refrigerators and their cooling systems
The first devices for cooling food and drinks appeared several thousand years ago in Ancient Egypt and China. In most cases, ancient refrigerators consisted of two containers: a smaller one containing food was placed in a larger one, partially filled with ice or cold water. Obviously, such a device was available exclusively to rich people and was not only a luxury item, but also a work of art.
The scientific and technological revolution of the 19th century also contributed to food freezing technologies. Thus, since 1850, in experimental and industrial models, and since 1913 in household refrigerators, so-called heat pumps have been used for cooling - special devices that transfer heat from the working (refrigerator or freezer) chamber to the external environment.
The possibility of long-term preservation of food freshness was appreciated, therefore, by the middle of the 20th century, almost every American family had a refrigerator, 30% of housewives from Western Europe - and only individual citizens of the Soviet Union, since the father of all nations I.V. Stalin attributed refrigerator to bourgeois excesses. It is unlikely that Stalin deliberately tried to starve the population of stale food; it’s just that in the pre-war years, almost all the metal needed, including for the manufacture of refrigerators, was used for the construction of military equipment. Nevertheless, the beginning of mass production of refrigerators in the USSR coincided with the debunking of the cult of personality, therefore, if there was no sex in the Soviet Union for another forty long years until 1991, by the end of the 80s there were refrigerators in almost every family.
Over the next twenty years of rampant democracy, refrigerators penetrated into all kitchens, including village and country houses. Modern housewives can afford to be capricious and choose from a whole variety of models that suit them in color and size. However, despite their endless variety, the technology for cooling and freezing food and drinks in almost all refrigerators has remained unchanged for half a century.
Types of refrigerators
In total, four types of refrigeration units can be distinguished that claimed to be domestic: compression, absorption, thermoelectric and refrigerator with vortex coolers.
In the latter, extremely rare type, which has not gone beyond prototypes and test installations, cooling is carried out by expanding the air compressed by the compressor in special chambers - vortex coolers. These devices were reliable and safe, but had extremely low efficiency, made monstrous noise and therefore had virtually no chance of success, especially in everyday life.
Units of the second type - absorption refrigerators, the design of which was proposed by Albert Einstein, provides cooling of the working chamber due to the evaporation of ammonia. They got their name because the circulation of the refrigerant occurs during the process of its dissolution in a liquid, most often in water. For further operation of the refrigerator, this solution is divided into water and ammonia, after which the latter is liquefied, then evaporates and dissolves again in water, then the cycle is repeated from the very beginning.
Unlike vortex refrigerators, absorption refrigerators are practically silent; in addition, most designs also have no moving parts. Devices based on this principle have a feature that is quite exotic for household devices - they can operate not on electricity, but on burned fuel, such as wood. This allows you to take such refrigerators, for example, on a hike or to the beach. Despite the advantages, there are also disadvantages - relatively low specific productivity, as well as the potential danger of poisoning with toxic substances.
Car refrigerator
At the heart of the work thermoelectric refrigerator lies the Peltier effect - cooling the point of contact of two different conductors during the passage of electric current. Refrigerators using such elements are reliable, silent, but quite expensive and extremely inefficient compared to other heat pumps. Despite this, they can be found in car coolers, water coolers and computer coolers.
Peltier element structure
The most common in everyday life compression refrigerators. They are based on the property of a substance to absorb heat during evaporation. The refrigerant (safe freon gas) boils in the evaporator, thereby cooling the air in the internal chamber. To complete the cycle, it must be turned back into liquid. This occurs when the increased pressure created by the compressor in the condenser produces heat. Condensers can be placed at the rear either open (the familiar grille) or closed (the condenser is protected by a special plate, and ventilation holes are provided on top for efficient heat exchange). In addition, some manufacturers place the condenser in the side walls, which allows you to install the refrigerator close to the wall.
The compressor is the noisiest element of the refrigerator
This type of heat pump is relatively simple, cheap and safe for domestic use. The disadvantage of the design is the noise generated by the compressor, therefore, to reduce the noise load, it is placed on special vibration suspensions.
Single and double compressor refrigerators
There are refrigerators on the market equipped with both one and two compressors. In the latter case, each chamber (refrigerator and freezer) has an autonomous cooling system, which allows you to independently regulate the temperature and turn off unused chambers. This can be useful, for example, during a long vacation or when there is temporarily no need to freeze and store food for a long time.
In refrigerators with one compressor, a solenoid valve is used to separately control the operation of the chambers, which regulates the supply of refrigerant to the evaporators. For consumers, this means that they will not notice any difference in operation compared to dual-compressor models. The only difference is that you cannot turn off the freezer.
In general, two-compressor models are somewhat more expensive, less reliable (due to a larger number of elements and, accordingly, a greater likelihood of failure), but potentially have the advantage that if one compressor fails, the second continues to function. It remains unclear who will be content with one working camera out of two possible ones.
Cooling systems
Any refrigerators, even the most modern ones, require regular maintenance. This is primarily due to the fact that frost freezes on the evaporators. There are several systems that deal with this problem with varying degrees of success.
The most common is the so-called crying wall or "cry". A refrigerator with such a system works as follows: the evaporator on the rear wall cools the refrigerator compartment, but at the same time frost forms on it. At one stage of the refrigerator’s operation, the compressor stops, cooling stops and the frost melts, turning into water, which flows through the drainage system into a special container located near the compressor. When the latter operates, the container heats up and the water evaporates. Obviously, at the same time, a fairly high humidity is maintained in the refrigeration chamber.
The familiar “crying” wall
The operation of such a system involves defrosting the freezer evaporator from several times a year to once every few years, depending on operating conditions - load, humidity, frequency of door opening and other factors. Such devices are theoretically more reliable than models with forced cooling, since the system is simpler.
Second type - mixed cooling, when in the refrigerator compartment defrosting occurs automatically (a “crying” wall), and in the freezer - with the help of an electric heater. Depending on the manufacturer, such a combined system may be called differently - No Frost, Frost Free, etc.
The third, technically more complex, system is based on cooling products using cold air flows. An evaporator hidden behind the wall uses special fans to cool both chambers. Its temperature is slightly lower than inside the chambers, and therefore frost freezes only on it, while thawing, as in the case of a combined system, occurs due to a special heater. As a result, the walls of the refrigerator chambers equipped with such a system do not freeze, which greatly facilitates maintenance. Marketing names - Full No Frost, Full Frost Free, etc.
No Frost systems impress with the complete absence of frost in the freezer
It should be noted that, regardless of the cooling system, it is necessary to periodically carry out hygienic cleaning of the refrigerator, which can be easily combined with defrosting.
Shelves
Despite their apparent simplicity, shelves play a big role in the operation of the refrigerator. The fact is that the old lattice shelves, with all their many shortcomings, had one serious advantage - they provided high-quality air circulation, and therefore more uniform cooling.
The convenience of using a refrigerator largely depends on the shelves.
Modern shelves made of tempered glass are very convenient, beautiful and hygienic, but they significantly impede air convection. Therefore, many manufacturers equip their devices with forced ventilation to ensure high-quality air mixing. Typically, each solution gets its own marketing name and is presented as a significant improvement, such as Multi Air Flow, Dynamic Air Flow, etc.
Additional cooling system features
Some refrigerator models are equipped super freeze function- it allows you to additionally cool the freezer so that when new products are added, the temperature does not increase and those already stored do not thaw. In addition, the lower temperature ensures rapid freezing, which means it allows you to better preserve the beneficial properties of food. It should be noted that a similar function exists for the refrigerator compartment.
A significant expansion of the functionality of the refrigerator is, of course, the so-called freshness zones. Such a zone is a separate chamber or cell (box) in which the temperature is maintained close to zero. This allows you to preserve the freshness of products, especially perishable ones, for a long time without freezing. It is optimal to have a separate chamber, similar to a refrigerator, but smaller in size. This separation allows you to effectively maintain temperature and humidity.
Freshness zones reduce the frequency of trips to the store
Typically, users are offered two freshness zones:
- dry, intended for storing meat, poultry, fish, seafood;
- wet, which is ideal for preserving vegetables, fruits, and herbs.
Thus, according to information from the company - one of the founders of zero zones - the shelf life of berries increases by 3-4 times, potatoes and apples will remain fresh for almost three months, and meat and poultry will last a whole week instead of several days. This means you can plan your diet and supplies with much more freedom. In simpler solutions, where the fresh zone is a drawer or special compartment inside the refrigerator compartment, such temperature and humidity control is understandably not possible, which reduces the usefulness of the zero zone.
An ice maker will surely delight your guests
Another nice addition could be ice maker- a special device that automatically prepares ice. Typically, these refrigerators are directly connected to a cold water source, which is filtered to improve the quality of the ice. It should be noted that in some cases, some manufacturers may call ice generators a special tray system that provides for minimal automation of ice production.
As you know, the main function of a refrigerator is to cool food and drinks.
Previously, refrigerators looked rather unattractive and did not always fit into the interior. Their functionality and capacity were also very limited and left much to be desired.
Old refrigerator models
Now the situation has changed and now refrigerators are almost the most important detail in the interior. The functionality of refrigerators becomes more voluminous every year, and capacity is constantly being optimized, including by reducing the main components of the refrigerator, such as a compressor, etc.
Modern models of household refrigerators
The only thing that remains unchanged is maintenance, but to carry out repairs you need to know its structure and operating principle.
The principle of operation of the refrigerator.
The principle of operation of any refrigerator, including a household one, is based on the principle of changing the state of the liquid, ice into water, water into steam and steam into ice, and so on in a circle.
Fig.1 Operating principle of the refrigerator
As shown in Figure 1, the principle is based on the movement of refrigerant from the condenser to the capillary, from the capillary to the evaporator, from the evaporator to the compressor, and from the compressor to the condenser. As the refrigerant passes through a circle, it is exposed to high and low pressure, causing its state to change.
Main components and parts of the refrigerator:
- Compressor- the main element in each refrigerator is it, which pumps and transfers refrigerant (freon) into the condenser, and also sucks refrigerant vapor (freon) from the evaporator. Refrigerant (Freon) is a gas (colorless and odorless). When exposed to temperature or pressure, it changes its properties.
- Capacitor- the artery of the refrigerator, it is a metal tube with a small outer diameter, approximately 5 mm. As a rule, it is made in the form of a snake. It is connected to thin metal rods across the entire width every 10-15 mm. In the condenser system, freon is compressed, after which it acquires a liquid state. Also, filter-driers are mounted in or near the condenser - a device that looks like a cylinder, the ends of which are narrowed. Its main purpose is to dry freon, as well as delay and filter debris that is generated during operation.
- Evaporator- Carries one of the main functions. Due to the fact that freon is injected into it, after which the freon is subsequently cooled to a low temperature. The entire evaporator system is called a refrigerator unit.
- Relay- the start protection relay is usually located on or near the compressor. The principle of operation of the refrigerator relay is to start and ensure operation of the compressor, and also serves to protect against network overloads.
- Thermometers- now they are called a control unit, usually such units combine an indication of temperature, freezing and defrosting, an icebreaker and much more. Its main purpose is to control and inform about the operation of the refrigerator and the operation of all its functions.
- Circuit breakers- are usually located next to the control unit and are often connected to thermometers and other sensors. They serve to protect the entire control unit and all electronic devices of the refrigerator from overvoltage or power surges in the network.
- Shelves- shelves, as it may seem at first glance that they do not serve the main function in the operation of the refrigerator, but this is not so. They act as insulating covers for freezers to contain the cold inside the freezers.
- Seals- rubber gaskets with magnetic holders. Seals serve to seal the refrigerator compartments from external influences and prevent air from entering the interior of the chambers.
- Impellers- perform the function of a regular fan or hood. It regulates air exchange and air circulation in the refrigerator chamber.
- Lamps- provide lighting for convenient use of the refrigerator at night.
It should be noted that the entire system is interconnected by copper tubes - which supply refrigerant (freon) from one device to another.
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These records on refrigerators are presented to you from our own notes based on the technical literature read by domestic authors, as well as from personal practice in repairing home refrigerators.
Getting cold - in refrigerators
Any body that has a higher temperature compared to its environment is capable of cooling naturally. That is, heat from a warmer body is transferred to the environment, and the temperature of the body itself will decrease.
To cool the body to a temperature below the environment, you will need a method of artificial cooling with the expenditure of a certain amount of energy.
For this method of artificial cooling, there are special machines that take heat from the object being cooled and transfer it to a warmer environment. The principle of transferring heat in this way is called the artificial method of producing cold, which is how all refrigerators work.
Cooling in refrigeration chambers occurs as a result of the boiling of the refrigerant, which is forced to circulate in a closed refrigerator system. This refrigerant or whatever it is also called refrigerant, is usually freon.
Refrigerators \refrigerators\ are of two types:
- absorption;
- compression
As we know, compression types of refrigerators, where refrigerant circulation occurs forcibly due to the operation of a motor-compressor, have become more widely used.
refrigerator Atlant
Based on the photograph of the Atlant refrigerator, this refrigerator can be characterized as follows:
The design of a compression refrigerator is of a closed type with one motor - a compressor, ensuring complete sealing of the refrigeration unit.
The refrigerator compartment is located in the upper compartment of the refrigerator. The freezer is located in the lower compartment. The lower compartment of the freezer consists of three drawers for freezing food. The upper compartment of the refrigerator consists of six shelves for storing food in a chilled state.
For absorption types of refrigerators, the circulation of the refrigerant occurs under the influence of the heating element \Heating element\, or where the circulation of the refrigerant occurs in a different way, under the influence of another heat source.
And the third way to obtain artificial cold is the thermoelectric method, where the work of transferring heat from a cooled object to a warmer environment is carried out due to the movement and flow of electrons. That is, in this example, cooling occurs due to the flow of electric current. As is known, this method of obtaining artificial cold is not used in household refrigerators.
Compression type refrigerators
As mentioned above, the principle of operation of compression types of refrigerators is the operation of a motor-compressor, due to which the refrigerant is pumped and circulated in a closed refrigerator system.
The system consists of:
- condenser \coil\;
- control valve;
- evaporator
and compressor. The compressor is driven by an electric motor, hence the name “motor-compressor”.
This diagram of the refrigeration unit \Fig. 1\ is comparable, for example, to a two-chamber Atlant refrigerator, and the fundamental principle of operation itself is no different from single-chamber refrigerators with one motor - a compressor.
Figure No. 2 shows a diagram of a refrigeration unit with one motor - compressor, consisting of:
- motor - compressor;
- thermal circuit;
- condenser \coil\;
- zeolite filter;
- small cross-section capillary tube;
- refrigeration chamber evaporator;
- freezer evaporator;
- discharge tube.
The operating principle of a compression-type refrigerator is as follows:
The heated refrigerant under the pressure of the piston in the cylinder is supplied through the discharge pipeline to the condenser. At increased pressure, the refrigerant changes from a gaseous state to a liquid state, releasing heat into the environment. Further, when the refrigerant passes through the valve, a sharp drop in pressure is created in the evaporator, and the refrigerant boils at low pressure. The process of liquid passing through the valve into the evaporator is called throttling.
The evaporator, as you understand, is located in the wall of the freezer. When the refrigerant boils in the evaporator, heat is removed from the environment, that is, the freezer. The refrigerant vapor from the evaporator is sucked by the compressor and then the compressed refrigerant in the cylinder is supplied under pressure to the condenser.
Repeated cycles of refrigerant circulation in a closed refrigerator system occur again and again. That is, the refrigerant circulating during operation of the refrigerator takes heat from the freezer through the evaporator and releases heat through the condenser to the environment.
The electrical energy that is expended when cooling the freezer depends on the work performed by the motor-compressor. Refrigerators \refrigerators\ are determined by their refrigeration capacity, which takes into account the amount of heat \kcal\ that the evaporator is capable of removing within one hour.
The cooling capacity of the same refrigerator will be different, depending on the ambient temperature itself, therefore, it is not recommended to install refrigerators near the heating system \radiators, pipes\.
The assessment of the cooling capacity of different types of refrigerators is determined by measuring the temperature of the refrigerant in the corresponding places of the refrigerator. Temperature measurements include places such as:
- temperature of suction refrigerant vapors;
- dew point;
- boiling point of the refrigerant in the evaporator;
- subcooling temperature of the liquid refrigerant in front of the control valve.
Temperatures have a significant impact on cooling capacity:
- refrigerant boiling in the evaporator;
- refrigerant condensation.
To determine cooling capacity, the following “standard” temperature conditions are accepted for:
- the boiling point of the refrigerant in the evaporator is minus fifteen degrees Celsius;
- condensation temperature - minus thirty degrees Celsius;
- temperature of sucked refrigerant vapors - fifteen degrees Celsius;
- the temperature of the liquid refrigerant in front of the control valve is thirty-two degrees Celsius.
Compression-type refrigeration machines are of closed and open types by design, differing in the location of the compressor and electric motor, as well as the presence of detachable connections.
For open types, in refrigeration machines the electric motor and the compressor are installed separately, where the crankshaft of the compressor is driven by an electric motor through a belt drive. In these refrigerators of this type, refrigerant leakage occurs in the sealing areas, that is, the seals remain the main place of refrigerant leakage.
The piping connections between the evaporator, condenser and compressor are detachable. At the places of such connections, refrigerant leakage is also possible.
In closed-type refrigeration machines, in particular this applies to most all modifications of household and home refrigerators, there are no detachable connections. That is, here the entire system is tightly welded and sealed, refrigerant leakage is almost impossible. In this example, a refrigerant leak may occur due to any mechanical damage with the formation of microcracks.
For closed type refrigerators or as they are also called hermetic refrigeration units, the difficulty of repair lies in the impossibility of disassembling and replacing parts, for example the same motor-compressor. Similar repairs will be discussed in this topic later.
Refrigerator refrigerants
Among the main parameters of the refrigerant \refrigerant\ is its boiling point. The relationship is as follows: the lower the temperature of the cooled object (freezer) needs to be lowered, the lower the boiling point of the refrigerant should be.
- The refrigerant is selected not only taking into account its boiling point, the refrigerant must also be:
- not poisonous;
- non-flammable;
- explosion-proof;
- with low pressure for condensation.
Typically the refrigerant used in home refrigerators is - freon 12.
freon - 12
Freon 12 is a heavy, colorless gas that is not poisonous. A weak specific smell of gas is felt with a large leak if the gas concentration in the air is more than 20%. The boiling point of this gas is almost minus 30 degrees Celsius, the solidification temperature is minus 155 degrees Celsius.
Among other refrigerants used in refrigeration machines are:
- freon -11;
- freon - 13;
- freon - 22.
Freon-12, like other refrigerants, is fluid in its properties, capable of penetrating into the slightest microcracks and metal pores. This gas can also corrode varnish coatings. Special varnishes are used to insulate the windings of an electric motor\sealed unit\.
When making repairs, it should be taken into account that this gas washes away rust well from the inner surface of the entire system - accordingly, the parts must be clean. If liquid freon comes into contact with the skin, it can cause freezing of the skin surface; freon does not have any irritating effect on the respiratory system.
Gas evaporation does not affect the taste of stored products and does not change the structure of any products stored in the refrigerator. During the repair process, the rubbing parts of the motor-compressor are thoroughly lubricated; special refrigeration refrigeration oils are used for this purpose.
Corrosion of the internal surfaces of the metal is caused by the so-called aging of the oil - its oxidation, the ingress of atmospheric oxygen into the composition of the special refrigerator oil. Therefore, before application, the oil is thoroughly dried and special antioxidant additives are added to the oil composition.
Corrosivity in the freon composition can subsequently cause blockage of small flow sections that are present in the circulation system. Lubricating oil for such purposes is used grade HF 12-16. You should also take into account the solubility of lubricating oil in freon; the oil contains paraffin, which can subsequently also cause blockage of small passages in the refrigerator system. This brand of lubricating oil is used in closed-type refrigeration compression machines using freon-12 in the system, that is, it can be used in modern home refrigerators.
The principle of operation and structure of the refrigerator
Home refrigerators have two chambers for storing food:
- refrigeration;
- freezer
chambers\branches\. If products have a long shelf life when frozen, special home refrigerators are used for this purpose. For products stored simply chilled \in the refrigerator\, the temperature ranges from 2 to 8 degrees Celsius.
Periodic shutdown of the refrigerator is carried out due to the operation of the thermostat, \cyclical operation\ and does not affect the conditions for freezing and storing food.
At the owner's request, manual adjustment of the thermostat makes minor changes in the temperature in the refrigerator chamber. Also, with the help of a thermostat and its settings, the required reduced temperature is ensured depending on the ambient temperature \warm room, cool room\.
refrigerator thermostat
Names such as refrigerator thermostat and refrigerator thermostat are absolutely identical in their purpose.
The refrigerator thermal protection relay is designed to protect the windings:
- stator;
- rotor
electric motor from sudden voltage surges and current overloads.
refrigerator compressor motor
The motor-compressor of closed-type refrigeration machines is tightly welded in a metal casing, like other parts of the refrigeration system as a whole.
The heat-protective relay \start-protective relay\ has a detachable connection to the motor-compressor of the refrigerator, and in the event of a malfunction, the heat-protective relay must be replaced.
starting - protective relay of the Atlant refrigerator
The differences between the names: “starting-protective relay and heat-protective relay” - there is no difference.
Why did you choose a closed-type compression unit for home refrigerators? This design of home refrigerators makes it possible to practically eliminate the leakage of the working fluid - freon. That is, when producing refrigerators, the manufacturer pays special attention to the manufacture of permanent connections in the circulating system.
In turn, these types of refrigerators ensure economical energy consumption. At an ambient temperature of 25 degrees Celsius, the electricity consumption is up to 1.2 kilowatts per hour.
The capacity of the refrigeration chamber is determined geometrically, that is, it is measured either in cubic decimeters or in liters. According to standards, per kilogram of food there are 6 - 8 liters of refrigerator space. The capacity of home refrigerators usually does not exceed 400 liters.
Based on the number of people in the family, when purchasing a refrigerator, the following options for choosing refrigerators are convenient:
- for a family of two people, the capacity of the refrigerator compartment is selected to be 100 - 160 liters;
- for a family of three people, the capacity is selected to be 160 - 200 liters;
- A family of four people sticks to a capacity of 240 - 300 liters;
- more than four people, the chamber capacity is up to 400 liters.
For better heat removal by the evaporator, it is more advisable to install shelves in the form of a metal grid in refrigerators. Shelves made in this way allow you to evenly distribute the temperature in the refrigerator compartment.
On the door, on the freezer side, refrigerators have a push-button light switch. When the refrigerator door is opened, the contacts close and the refrigerator compartment is illuminated by an electric light bulb.
To store frozen food in large quantities, refrigerators with a larger freezer compartment are provided. For the freezer compartment\frozen food storage\ you can use the following calculation - for half a kilogram of frozen food there is one liter of capacity\freezer\.
Snow cover in the chamber is formed from air condensation entering when the door is opened, as well as when there is insufficient sealing when the refrigerator door is closed. The resulting snow coat must be systematically removed, since such formation impairs the heat removal by the evaporator from the chamber.
Typically, the design of the refrigerator previously included a tray to collect melt water during defrosting. Currently, refrigerators are manufactured in which there is a hole in the freezer itself to drain the water formed as a result of condensation. When water flows into the hole, it then simply evaporates. Owners of refrigerators, when defrosting them \removing ice, snow coat\, turn off the refrigerator and with the doors open, effective complete defrosting occurs. Also, some refrigerator designs are equipped with heating elements for the defrosting process. That is, both semi-automatic and automatic defrosting of the chamber occurs when the motor-compressor is turned off with the participation of a thermostat.
Automatic defrosting occurs automatically, periodically after a certain time and without the participation of the owner. The water in this example is drawn out through a tube from the chamber, where it then evaporates.
Home refrigerators - and their types
The methods for generating artificial cold in refrigerators are different and depend on the type of refrigeration machine. As already mentioned, refrigerators are divided into:
- compression;
- absorption;
- thermoelectric\semiconductor\.
absorption refrigerator Ezetil Absorber A – 4000
thermoelectric refrigerator Tropi Cool Classic
According to their purpose, refrigerators are divided into:
- two-chamber;
- single-chamber;
- low temperature.
Single-compartment refrigerators are used to store food in a chilled state.
Double-chamber refrigerators are used for storing both frozen and chilled foods.
Low-temperature refrigerators are used for freezing and also for storing frozen foods.
low-temperature refrigerator HNT – 200
Also, according to their design, refrigerators are:
- wall;
- built-in;
- desktop;
- floor
built-in refrigerator
Low-temperature refrigerators are usually produced in the form of a chest, the lid \door\ of such a refrigerator is located on top.
Single-chamber floor-standing \cabinet-style \ refrigerators are more common in home use.
Small-sized refrigerators, the so-called “cabinet tables,” are also convenient for their operation.
In purchasing and choosing refrigerators, of course, everything depends on the desires of the buyer himself. For example, combined floor-standing refrigerators can be combined, for example, with a kitchen cabinet.
To order, the refrigerator can be made combined\combined\with a sideboard. The finishing of these refrigerated cabinets is done to match the color of the combined furniture.
Wall-mounted refrigerators have double doors and their design resembles a small wall cabinet.
refrigerating cabinet \wall-mounted, tabletop\ Liebherr FKv 503 Premium
Built-in refrigerators are the least common. To cool the condenser, the refrigeration unit is placed in a built-in cabinet to ensure air circulation.
In countertop refrigerators, cooling usually occurs thermoelectrically.
Double-chamber refrigerators consist of two food storage chambers: a cooling chamber and a freezer chamber.
Low-temperature refrigerators, or “freezers” as they are also called, are used for long-term frozen food storage.
In the following topics you will familiarize yourself with a detailed description of refrigerator repairs and their electrical circuits.
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