In order to navigate when the kitchen equipment fails, many housewives are forced to understand the principle of operation of many devices, such as: an electric stove, microwave oven, refrigerator and others. The main function of the refrigerator is to keep nutritious food fresh, so it has to work constantly, and the services of a repair technician cannot be used instantly. Understanding how the refrigerator works will help save financial and time resources, and many malfunctions can be repaired by hand.
The interior of the refrigerator
Everyone knows how a refrigerator works, in simple words - this equipment freezes and cools a wide variety of products, allowing them to avoid spoilage for some time.
At the same time, not everyone knows certain features of this device: what does the refrigerator consist of, where does the cold come from in the inner plane of the chamber, how it is created by the refrigerator and why the device turns off from time to time.
To understand these issues, it is necessary to consider in detail the principle of operation of the refrigerator.... To begin with, we note that cold air masses do not arise by themselves: a decrease in air temperature is carried out inside the chamber during the operation of the unit.
This refrigeration equipment includes several main parts:
- refrigerant;
- evaporator;
- capacitor;
- compressor.
The compressor is the heart of any refrigeration unit... This element is responsible for the circulation of the refrigerant through a large number of special tubes, some of which are located at the back of the refrigerator. The rest of the parts are camouflaged in the inside of the camera under the panel.
During operation, the compressor, like any motor, is exposed to significant heating, so it takes some time to cool down. So that this unit does not lose its performance due to overheating, a relay is built into it, which opens the electrical circuit at certain temperature indicators.
The tubes located on the outer surface of the refrigeration equipment are the condenser. It is designed to release heat energy to the outside. The compressor, while pumping the refrigerant, sends it to the inside of the condenser by means of high pressure. As a result, a substance with a gaseous structure (isobutane or freon) becomes liquid and begins to heat up. The excess heat is then dissipated in the room so that the refrigerant is cooled naturally. It is for this reason that it is forbidden to install heating devices next to refrigerators.
The owners, who know about the principle of operation of the refrigerator, try to arrange for their “kitchen assistant” the most optimal conditions for cooling the condenser and compressor. This allows you to extend its life..
To obtain cold in the inner chamber, there is another part of the pipe system, into which the liquefied gaseous substance is sent after the condenser - it is called the evaporator. This element is separated from the condenser by a drying filter and a capillary. The principle of cooling inside the chamber:
- Once in the evaporator, freon begins to boil and expand, again transforming into gas. In this case, the absorption of thermal energy is carried out.
- The tubes in the chamber cool not only the air masses of the unit, but also cool themselves.
- The refrigerant is then sent back to the compressor and the cycle repeats.
In order to prevent nutritious foods from freezing inside the refrigerator, a thermostat is built into the equipment. A special scale makes it possible to set the required degree of cooling, and after reaching the required values, the equipment automatically turns off.
Single and double chamber models
The unit that cools the air in each refrigerator has a general design principle. However, there are still differences in the functioning of different equipment. They are based on the peculiarities of the movement of the refrigerant in refrigeration cabinets with one or a pair of chambers.
The diagram, which was presented just above, is typical for single-chamber models. Regardless of the location of the evaporator, the principle of operation will be the same... However, if the freezer is located under or above the cooling compartment, then an additional compressor is needed for stable and full operation of the refrigerator. For a freezer, the principle of operation will be the same.
The refrigeration compartment, in which the temperature does not fall below zero, starts only after the freezer has cooled sufficiently and turned off. Just at this moment, the refrigerant from the freezing system is sent to the chambers with a positive temperature, and the evaporation / condensation cycle is already at a lower level, therefore it is impossible to say for sure how long the refrigeration equipment needs to work before it turns off automatically. It all depends on the thermostat setting and the volume of the freezer chamber.
Fast freezing function
This function is typical for two-compartment refrigerators. In this mode, the refrigerator can work continuously for a long time. Fast freezing is intended for effective freezing of products in large volumes..
After activating the option, special LED indicators on the panel will light up, indicating that the compressor is running. Here you need to take into account the fact that the operation of the unit will not be stopped automatically, and too long the operation of the refrigerator can negatively affect its condition.
After manual shutdown of the unit, the indicators themselves will go out, and the compressor drive will shut down.
Modern refrigerators are equipped with a wide variety of functions. And today, housewives are aware of the existence of the automatic defrosting function. Non-freezing and drip refrigeration systems have made human life much easier, but the principle of the refrigerator has remained the same.
Today, a huge number of products need cooling, and without cold it is impossible to implement many technological processes. That is, we face the need to use refrigeration units in everyday life, in trade, in production. It is far from always possible to use natural cooling, because it will be able to lower the temperature only to the parameters of the ambient air.
Refrigeration units come to the rescue. Their action is based on the implementation of simple physical processes of evaporation and condensation. The advantages of machine cooling include the automatic maintenance of constant low temperatures that are optimal for a particular type of product. Also important are the insignificant specific operating, repair costs and the cost of timely maintenance.
To obtain cold, the property of the refrigerant is used to adjust its own boiling point when the pressure changes. To convert a liquid into vapor, a certain amount of heat is supplied to it. Similarly, condensation of a vaporous medium is observed during heat removal. The principle of operation of the refrigeration unit is based on these simple rules.
This equipment includes four units:
- compressor
- capacitor
- thermostatic expansion valve
- evaporator
All these units are connected to each other in a closed technological cycle using piping. The refrigerant is supplied through this circuit. This is a substance endowed with the ability to boil at low negative temperatures. This parameter depends on the pressure of the vaporized refrigerant in the evaporator tubes. A lower pressure corresponds to a lower boiling point. The vaporization process will be accompanied by the removal of heat from the environment in which the heat exchange equipment is placed, which is accompanied by its cooling.
Boiling produces refrigerant vapors. They enter the compressor suction line, are compressed by it and enter the heat exchanger-condenser. The compression ratio depends on the condensing temperature. In this technological process, an increase in the temperature and pressure of the working product is observed. The compressor creates such output parameters at which it becomes possible to transfer steam into a liquid medium. There are special tables and diagrams for determining the pressure corresponding to a certain temperature. This refers to the process of boiling and condensation of vapors of the working medium.
A condenser is a heat exchanger in which hot refrigerant vapors are cooled to dew point and transferred from vapor to liquid. It does this by extracting heat from the heat exchanger by the ambient air. The process is carried out using natural or artificial ventilation. The second option is often used in industrial refrigeration machines.
After the condenser, the liquid working medium enters the thermostatic expansion valve (choke). When it is triggered, the pressure and temperature decrease the operating parameters of the evaporator. The technological process goes round again. To obtain cold, it is necessary to select the boiling point of the refrigerant below the parameters of the medium to be cooled.
The figure shows a diagram of the simplest installation, after examining which you can visually represent the principle of operation of the refrigerating machine. From designations:
- "I" - evaporator
- "K" -compressor
- "KS" - capacitor
- "D" - throttle valve
The arrows indicate the direction of the technological process.
In addition to the listed main units, the refrigeration machine is equipped with automatic devices, filters, dryers and other devices. Thanks to them, the installation is automated as much as possible, ensuring efficient operation with minimal human control.
Various freons are mainly used today as a refrigerant. Some of them are gradually being phased out due to their negative impact on the environment. Certain freons have been proven to deplete the ozone layer. They were replaced by new, safe products such as R134a, R417a and propane. Ammonia is used only in large-scale industrial plants.
The theoretical and real cycle of the refrigeration unit
This figure shows the theoretical cycle of a simple refrigeration plant. It can be seen that not only direct evaporation but also superheating of steam occurs in the evaporator. And in the condenser, the vapor turns into a liquid and is somewhat supercooled. This is necessary in order to improve the energy efficiency of the technological process.
The left side of the curve is saturated liquid and the right is saturated vapor. What is between them is a vapor-liquid mixture. On the D-A` line, there is a change in the heat content of the refrigerant, accompanied by the release of heat. But the segment B-C`, on the contrary, indicates the release of cold during the boiling process of the working medium in the evaporator tubes.
The actual duty cycle differs from the theoretical due to the presence of pressure losses in the compressor piping, as well as on its valves.
To compensate for these losses, the compression work must be increased, which will reduce the cycle efficiency. This parameter is determined by the ratio of the refrigeration power generated in the evaporator to the power consumed by the compressor and the electrical network. Plant efficiency is a comparative parameter. It does not directly indicate the performance of the refrigerator. If this parameter is 3.3, it will indicate that the unit of electricity consumed by the installation accounts for 3.3 units of cold produced by it. The higher this indicator, the higher the efficiency of the installation.
The device and principle of operation of the refrigeration unit
Cooling is subdivided into natural and artificial. Energy is not spent on the first. Moreover, the temperature of the object tends to the temperature of the surrounding air. Artificial cooling is a decrease in the temperature of an object to a level below the same indicator of the environment. This kind of cooling requires refrigeration machines or devices. They are usually used in industry to achieve the required storage conditions, the course of chemical reactions, and safety. Heat and refrigeration machines are very widely used in everyday life. Their principle of operation is based on the phenomena of sublimation and condensation.
Ice chilling
This is the most affordable and simple form of cooling. It is especially convenient in areas where there is a possibility of natural ice accumulation.
As a means of cooling, ice is used in the preparation and storage of fish, in the short-term storage of vegetable products, in the transportation of food products in a chilled form. Ice is used in cellars and glaciers. In such equipment, thermal insulation is very important. In stationary glaciers, the walls are hydraulically and thermally insulated. They are designed for a temperature range of +5 ... + 8 ° C.
Ice-salt cooling
The ice-salt cooling method makes it possible to maintain even lower temperature conditions in the volume to be cooled. Using ice and salt together makes it possible to lower the temperature at which ice melts. This is the principle. Refrigeration principle.
For this purpose, ice and sodium chloride are mixed. Depending on the salt concentration, the ice temperature ranges from -1.8 to -21.2 ° C.
The melting point reaches a minimum if the salt in the mixture is 23%. In this case, the ice does not melt at a minimum value.
Dry ice is used to maintain low temperatures during the storage of fruits, ice cream, vegetables, semi-finished products. This is the name of the solid state of carbon dioxide. At atmospheric pressure and heating, it turns from solid to gaseous, passing the liquid phase. The cold performance of dry ice is twice that of water ice. When dry ice is sublimated, carbon dioxide is produced, which, among other things, performs a preservative function, contributing to the preservation of food.
Cooling methods using ice also have a number of disadvantages that limit their application. In this regard, machine cooling becomes the main method of generating cold.
Artificial cooling
Machine cooling is the production of cold produced by refrigeration machines and installations. This method has several advantages:
- in automatic mode, the temperature level remains constant, which is different for different groups of products;
- the cooled space is optimally used;
- it is convenient to operate the refrigerated premises;
- low maintenance costs.
How does it work
The principle of operation of the refrigeration machine is as follows. Of course, a person who only uses a refrigeration machine or is looking for it does not have to deeply and comprehensively understand the operation of refrigeration machines. At the same time, knowledge of the fundamental principles of the operation of such installations will not be at all superfluous. This information can help you make an informed choice of equipment and make it easier to talk with professionals when choosing refrigeration equipment.
It is also important to understand how the chiller works. In situations where refrigeration equipment fails and a specialist call is required, it makes sense to delve into the principle of operation of such machines. After all, understanding the specialist's explanations that you need to replace or repair any part of the refrigerating machine will allow you not to lose extra money.
The main principle of a refrigerating machine is to remove heat from an object being cooled and transfer it to another object. It is important to understand that heating or contraction of an object is accompanied by the transfer of energy to it, while cooling and expansion takes away energy. Heat transfer is based on this.
To transfer heat, refrigeration machines use refrigerants - special substances that take heat away from the object of cooling during boiling and expansion at a constant temperature. Subsequently, after compression, energy is transferred to the cooling medium through condensation.
Purpose of individual nodes
The compressor of the refrigeration machine ensures the circulation of the refrigerant in the system, its boiling in the evaporator with the injection into the condenser block.
It is designed to suck the refrigerant freon in a gaseous state from the evaporators, and, by compressing, pump it into the condenser, where it turns into a liquid. Then freon in a liquid state accumulates in the receiver. This unit is equipped with inlet and outlet shut-off valves. The further path of the refrigerant is from the receiver to the filter drier. Here, residual moisture and impurities are removed and fed to the evaporator.
In the evaporator, the refrigerant reaches a boil, which removes heat from the object to be cooled. Further, the refrigerant, already in a gaseous state, enters the compressor from the evaporator, being cleaned from impurities through a filter. Further, the operating cycle of the unit is repeated, this is the principle. Refrigeration principle.
Refrigeration unit
The combination of a set of parts and assemblies of a refrigeration machine on a single frame is usually called a refrigeration unit. The combination of the refrigeration machine units by the manufacturer makes the installation more convenient, and it happens faster.
The cooling capacity of such units is a parameter representing the amount of heat taken away from the medium subjected to cooling in one hour. With different operating modes, the cold performance varies over a wide range. When the condensing temperature rises and the evaporating degree decreases, the performance decreases.
Refrigerants
Refrigerating machines used in trade organizations use freon or freon as refrigerants, and ammonia for freezing on an industrial scale.
Halon is a heavy gas, colorless and with a faint odor, perceptible only when its concentration in the air reaches 20%. The gas is neither flammable nor explosive. Lubricating oils are readily soluble in freon. At high temperatures, they form a homogeneous mixture with it. Freon does not affect the taste, aroma and color of products.
Refrigeration units with freon should not contain more than 0.006% of the mass of moisture. Otherwise, it will freeze in the thin tubes, interfering with the operation of the chiller. Due to the high fluidity of the gas, a good sealing of the units is required.
Ammonia is a colorless, pungent-smelling gas that is dangerous to the human body. Its permissible content in the air is 0.02 mg / l. When the concentration reaches 16%, an explosion is possible. When the gas content is over 11% and an open flame nearby, combustion starts.
As long as the equipment functions properly, the user is not interested in how it works. Knowledge of how the refrigerator works will be needed when a breakdown occurs: it will help to avoid a serious malfunction or quickly determine the location. Correct operation is also highly dependent on user awareness. In the article, we will consider the device of a household refrigerator and its operation.
How is a compressor refrigerator
Atlant, Stinol, Indesit and other models are equipped with compressors that start the cooling process in the chamber.
Main constituent parts:
- Compressor (motor). It can be inverter and linear. Thanks to the start of the motor, freon moves through the tubes of the system, providing cooling in the chambers.
- The condenser is the tubes on the back of the case (in the latest models it can be placed on the side). The heat generated by the compressor during operation is transferred from the condenser to the environment. This prevents the refrigerator from overheating.
This is why manufacturers forbid installing appliances near batteries, radiators and stoves. Then overheating cannot be avoided, and the motor will fail quickly.
- Evaporator. Here freon boils and turns into a gaseous state. In this case, a large amount of heat is taken, the tubes in the chamber are cooled together with the air in the compartment.
- Thermoregulation valve. Maintains the set pressure for refrigerant movement.
- The refrigerant is freon gas or isobutane. It circulates through the system to help cool the chambers.
It is important to understand correctly how the technique works: it does not generate cold. The air is cooled by the removal of heat and its release to the surrounding space. Freon passes into the evaporator, absorbs heat and turns into a vaporous state. The engine drives the piston of the motor. The latter compresses freon and creates pressure to distill it through the system. Getting into the condenser, the refrigerant cools down (heat goes out), turning into a liquid.
To set the desired temperature regime in the chambers, a thermostat is installed. In models with electronic control (LG, Samsung, Bosch), it is enough to set the values on the panel.
Moving to the filter drier, the refrigerant gets rid of moisture and passes through the capillary tubes. Then it goes back to the evaporator. The motor distills freon and repeats the cycle until the optimum temperature is established in the compartment. As soon as this happens, the control board sends a signal to the start-up relay, which shuts down the motor.
Single-compartment and double-compartment refrigerator
Despite the same structure, there are still differences in the principle of operation. Older double chamber models have one evaporator for both chambers. Therefore, if during defrosting mechanically remove the ice and touch the evaporator, the entire refrigerator will fail.
The new two-compartment cabinet has two compartments, each with an evaporator. Both chambers are isolated from each other. Usually, in such cases, the freezer is at the bottom and the refrigerator compartment is at the top.
Since there are zero temperature zones in the refrigerator (read what the freshness zone in the refrigerator is), freon is cooled in the freezer to a certain level and then moved to the upper compartment. As soon as the indicators reach the norm, the thermostat is triggered, and the start relay turns off the motor.
Devices with one motor are most in demand, although with two compressors they are also gaining popularity. The latter function in the same way, just a separate compressor is responsible for each chamber.
But it is not only in two-chamber technology that the temperature can be set separately. There are such devices ("Minsk" 126, 128 and 130), where electromagnetic valves are installed. They cut off the supply of freon to the refrigerator compartment. Cooling is performed based on the readings from the temperature controller.
A more complex design involves the placement of special sensors that measure the temperature outside and regulate it inside the chamber.
How long does the compressor run
The exact readings are not listed in the instructions. The main thing is that the motor power is sufficient for the normal freezing of products. There is a general coefficient of operation: if the device operates for 15 minutes and rests 25 minutes, then 15 / (15 + 25) = 0.37.
If the calculated values are less than 0.2, then you need to adjust the readings of the thermostat. More than 0.6 indicates a violation of the tightness of the chamber.
Absorption refrigerator
In this design, the working fluid (ammonia) evaporates. The refrigerant circulates through the system by dissolving the ammonia in the water. Then the liquid goes to the stripper, and then to the reflux condenser, where it is again separated into water and ammonia.
Refrigerators of this type are rarely used in everyday life, since they are based on poisonous components.
Models with No Frost and Weeping Wall
Technique with the Know Frost system is at the peak of its popularity today. Because the technology allows you to defrost the refrigerator once a year, just to wash it. Features of functioning ensure the removal of moisture from the system, so ice and snow do not form in the chamber.
An evaporator is located in the freezer compartment. The cold it generates is circulated through the refrigerator compartment using a fan. There are openings in the chamber at the level of the shelves, where the cold stream comes out and is evenly distributed over the compartment.
After a cycle of operation, a defrost starts. The timer starts the heating element of the evaporator. The ice melts and the moisture is removed to the outside, where it evaporates.
"Crying vaporizer". The name is based on the principle that ice builds up on the evaporator while the compressor is running. As soon as the motor shuts off, the ice melts and condensation flows into the drain hole. The defrost method is called drip.
Super freeze
This function is also called "Fast Freeze". It is implemented in many two-chamber models "Khaer", "Biryusa", "Ariston". In electromechanical models, the mode is started by pressing a button or turning a knob. The compressor starts non-stop operation until the food is completely frozen both inside and outside. After that, the function must be disabled.
The electronic control automatically turns off superfreezing according to the signals from the thermoelectric sensors.
Electrical diagram
To independently find the cause of the problem, you will need knowledge of the electrical circuit.
The current supplied to the circuit goes this way:
- goes through the thermostat contacts (1);
- defrost buttons (2);
- thermal relay (3);
- start-up relay (5);
- is fed to the working winding of the motor motor (4.1).
An inoperative motor winding passes a voltage greater than the set value. At the same time, the starting relay is triggered, closes the contacts and starts the winding. After reaching the desired temperature, the thermostat contacts open and the motor stops the motor.
Now you understand how the refrigerator works and how it should work. This will help to properly operate the device and extend its useful life.
Today we cannot imagine our life without devices that cool food. Even in production, it is impossible to implement the technological process without refrigeration machines. So, it turns out that refrigeration units are necessary for us in our daily life, including production and trade.
It is not always possible to use free cooling, given the seasonality and the ability to reduce the temperature to a maximum of air temperature, and in summer this is not at all realistic. And this is where our need for a refrigerator begins. based on the fact that with the help of technology to implement the evaporation process and generate condensate.
Among the advantages of refrigeration units, one can single out the automatic operation of maintaining a constant low temperature, which will be optimal for a specific category of products. But this concerns the actual benefits, and if we take into account the costs of operation, repair and maintenance, then the refrigerator turns out to be a profitable technique.
The principle of operation of a chiller is based on cooling, a physical process based on the consumption of heat generated by the machine as a result of the boiling of a liquid. With what temperature indicator the liquid medium reaches a boil will depend on the origin of the liquid and the level of pressure exerted.
A high pressure reading means a high boiling point. Exactly in the same dependence this process works and vice versa: lower pressure - lower temperature of boiling and evaporation of the liquid.
The chemical properties of each type of liquid qualitatively affect the temperature required for boiling. So, for example, water boils at 100 degrees, and liquid nitrogen needs -174 degrees Celsius.
Consider liquid freon. This refrigerant is the most popular substance with which the entire refrigeration system is saturated. By the way, freon under normal conditions in an open container can boil even at normal atmospheric pressure. Moreover, this process will begin immediately as soon as the freon comes into contact with air.
This phenomenon is certainly accompanied by the absorption of ambient heat. You will be able to observe how the vessel will be covered with frost, because condensation and freezing of water vapor of the air occurs. This action will end only when the refrigerant takes on a gaseous state, or the pressure above the freon does not increase in order to stop evaporation and stop the conversion of liquid freon into gaseous.
This is how you can describe the principle of operation of the refrigeration machine in simple words.... A similar cycle is performed by liquid freon in the refrigerator system. The difference lies in the fact that the vessel is not open, but a special one that does not have access to air, called a heat exchanger unit, or, to be more precise, an evaporator.
The refrigerant boiling in the evaporator enters the active phase of absorbing heat emanating from the hose of the heat exchanger assembly. And the tubes, or rather their material, will be washed by liquid, and this is directly related to the air cooling process. This process should not be interrupted, it is permanent. To maintain it, it is necessary to regularly boil freon in the evaporator, which means constant removal of gaseous refrigerant and adding it in a liquid state.
Condensation of liquid freon vapor requires a temperature exactly what it will be, depending on atmospheric pressure. The higher the pressure reading, the higher the degree for condensation. A pressure of 23 atmospheres is necessary to condense the vapor of R22 freon, while the temperature will be +55 degrees.
Refrigerant vapors, when converted to liquid, generate a large amount of heat into the environment. The refrigerator for this process has a special, completely sealed heat exchanger, called a condenser. It is designed to remove the released heat energy. The capacitor looks like an aluminum element with a ribbed surface.
In order to remove freon vapors from the evaporator, and create a pressure that will be optimally favorable for condensation, a special pumping device is needed - a compressor. In addition, a refrigeration unit cannot do without the operation of the freon flow regulator. This function is assigned to the throttling capillary tube. Each of the elements of the refrigeration system is connected to each other by a pipeline, forming a sequential chain - this is how the system's circle is closed.
The principle of operation of the refrigeration unit on freon
Assumes the execution of a real cycle, which is significantly different from the theoretical one. The difference lies in the presence of such a thing as pressure loss. This happens during a real cycle on the compressor valves (read more about the types of the compressor here :) and on its piping in particular. Such losses must be compensated later.
To do this, it is necessary to achieve an increase in the work of compression, which will reduce the effectiveness of the cycle. The essence of this parameter is the ratio of the power of the unit and the power required for the operation of the compressor. But how efficiently the installation works is a comparative parameter, which does not in any way affect the performance of the refrigerator.
The principle of operation of the refrigeration unit on freon for comparison: the efficiency of work is 3.5, that is, for 1 unit of electrical energy for this system, there are 3.5 units of cold, which it produces. The efficiency of the machine will increase with the growth of this indicator.