The device and principle of operation of the refrigeration machine. The principle of operation of the refrigeration unit Diagrams of refrigeration units and where they are used

An ordinary person, as a rule, does not need to understand the principle of operation of a refrigeration machine; the result is important for him. The result of the operation of the refrigeration unit is: chilled products - from frozen vegetables to meat and dairy products, or, for example, chilled air, if we are talking about split systems.

Another thing is when the refrigeration machines fail and a specialist call is required to repair the refrigeration units. In this case, it would not be bad to understand the principle of operation of such units. At least in order to understand the need to replace or repair a component of the refrigeration machine.

The main purpose of a refrigeration plant is to take heat from a cooled body and transfer this heat or energy to another object or body. To understand the process, it is necessary to understand a simple thing - if we heat or compress a body, then we impart energy (or heat) to this body, while cooling and expanding, we take away energy. This is the basic principle on which heat transfer is built.

In a refrigeration machine, refrigerants are used to transfer heat - the working substances of a refrigeration machine, which, when boiling and in the process of isothermal expansion, take heat from the object being cooled and then, after compression, transfer it to the cooling medium due to condensation.

The refrigeration compressor 1 sucks off the gaseous refrigerant - freon from the evaporators 3, compresses it and pumps it into the condenser 2. In the condenser 2, the freon condenses and passes into a liquid state. From the condenser 2, the liquid refrigerant enters the receiver 4, where it accumulates. The receiver is equipped with shut-off valves 19 at the inlet and outlet. From the receiver, the refrigerant enters the filter-drier 9, where the remaining moisture, impurities and contaminants are removed, then it passes through the sight glass with a humidity indicator 12, the solenoid valve 7 and is throttled by the thermostatic valve 17 into the evaporator 3.

In the evaporator, the refrigerant boils, taking heat from the object to be cooled. The refrigerant vapors from the evaporator through the filter on the suction line 11, where they are cleaned of contaminants, and the liquid separator 5 enter the compressor 1. Then the operation cycle of the refrigeration unit is repeated.

Liquid separator 5 prevents liquid refrigerant from entering the compressor. To ensure guaranteed oil return to the compressor crankcase, an oil separator 6 is installed at the compressor outlet. In this case, the oil enters the compressor through the shut-off valve 24, filter 10 and sight glass 13 along the return line.

Vibration isolators 25, 26 on the suction and discharge lines dampen vibrations during compressor operation and prevent their propagation along the refrigeration circuit.

The compressor is equipped with a crankcase heater 21 and two shut-off valves 20. The crankcase heater 21 evaporates the refrigerant from the oil, preventing the refrigerant from condensing in the compressor crankcase during its standstill and maintaining the set oil temperature.

The cooling process in a refrigeration machine is based on the physical phenomenon of heat absorption during boiling () liquid. The boiling point of a liquid depends on the physical nature of the liquid and on the pressure of the environment. The higher the pressure, the higher the temperature of the liquid and, conversely, the lower the pressure, the lower the temperature, the liquid boils and evaporates. Under the same conditions, different liquids have different boiling points , so, for example, at normal atmospheric pressure, water boils at a temperature of + 100 ° C, ethyl alcohol + 78 ° C, R-22 minus 40.8 ° C, freon R-502 minus 45.6 ° C, freon R-407 minus 43.56°С, liquid nitrogen minus 174°С.

Liquid freon, which is currently the main refrigerant of the refrigeration machine, which is in an open vessel at normal atmospheric pressure, immediately boils. In this case, intense absorption of heat from the environment occurs, the vessel is covered with frost due to condensation and freezing of water vapor from the surrounding air. The process of boiling liquid freon will continue until all the freon passes into a gaseous state, or the pressure over the liquid freon increases to a certain level and the process of its evaporation from the liquid phase stops.

A similar process of refrigerant boiling occurs in a refrigeration machine, with the only difference that the refrigerant boils not in an open vessel, but in a special, sealed heat exchanger unit, which is called -. At the same time, the refrigerant boiling in the evaporator tubes actively absorbs heat from the material of the evaporator tubes. In turn, the material of the evaporator tubes is washed by liquid or air, and as a result of the process, the liquid or air is cooled.

In order for the process of refrigerant boiling in the evaporator to occur continuously, it is necessary to constantly remove gaseous refrigerant from the evaporator and “add” liquid refrigerant.

To remove the generated heat, an aluminum heat exchanger with a finned surface, called a condenser, is used. To remove refrigerant vapors from the evaporator and create the pressure necessary for condensation, a special pump - compressor is used.

An element of the refrigeration unit is also a refrigerant flow regulator, the so-called throttling. All elements of the refrigeration machine are connected by a pipeline in a series circuit, thereby providing a closed system.

The principle of operation of refrigeration units. Video

Today, we cannot imagine our life without appliances that cool products. Even in production, it is impossible to implement a technological process without refrigeration machines. So, it turns out that refrigeration units are necessary for our daily life, including production and trade.

It is not always possible to use natural 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 here begins our need to purchase a refrigerator. It is based on the fact that with the help of technology to realize the evaporation process and produce condensate.

Among the advantages of refrigeration units is the automatic operation of maintaining a constant low temperature, which will be optimal for a particular category of products. But this concerns the actual benefit, 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 the refrigeration machine is based on cooling - a physical process based on the consumption of heat generated by the machine as a result of boiling liquid. With what temperature indicator the liquid medium comes to a boil will depend on the origin of the liquid and the level of pressure exerted.

High pressure - high boiling point. This process works in exactly the same way and vice versa: lower pressure - lower boiling and evaporation temperature 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 a normal atmospheric pressure. Moreover, this process will begin immediately, as soon as freon comes into contact with air.

This phenomenon is necessarily 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 in the air occurs. This action will be completed only when the refrigerant takes on a gaseous state, or the pressure above the freon does not increase to stop evaporation and stop the conversion of liquid freon into gaseous.

So 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 goes into the active phase of absorbing heat coming from the hose of the heat exchanger unit. And the tubes, or rather their material, will be washed by liquid, and this is directly related to the air cooling process. Such a process should not be interrupted, it is permanent. To maintain it, regular boiling of freon in the evaporator is necessary, which means that the gaseous refrigerant is constantly removed and added in a liquid state.

The condensation of liquid freon vapor requires a temperature exactly the same as it will be depending on atmospheric pressure. The higher the pressure indicator, the higher the degree for condensation. A pressure of 23 atmospheres is necessary to condense R22 freon vapors, while the temperature will be +55 degrees.

Refrigerant vapors during their transformation into a liquid release a large amount of heat into the environment. The refrigerator for such a process has a special, absolutely sealed heat exchanger called a condenser. It is designed to remove the released thermal energy. The capacitor looks like an aluminum element with a ribbed surface.

In order to remove freon vapor from the evaporator, and create a pressure that is optimally favorable for condensation, a special pumping device is needed - a compressor. In addition, in a refrigeration unit, one cannot do without the work of a freon flow regulator. This function is assigned to the throttling capillary tube. Each of the elements of the refrigeration system is interconnected by a pipeline, forming a serial chain - this is how the circle of the system closes.

The principle of operation of the refrigeration unit on freon

It involves the execution of a real cycle, which differs significantly 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 compressor here:) and on its piping in particular. Such losses must be compensated for 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 affect the performance of the refrigerator in any way.

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 that it produces. The efficiency of the machine will increase with the growth of this indicator.

In order to navigate when kitchen equipment fails, many housewives are forced to understand the principle of operation of many devices, such as an electric stove, microwave, refrigerator, and others. The main function of the cold store is to keep nutritious food fresh, so it must be constantly running, and the services of a repair specialist cannot be used instantly. Understanding how the refrigerator works will help save financial and time resources, and many malfunctions can be fixed by hand.

Refrigerator interior

Everyone knows how a refrigerator works, in simple words - this equipment freezes and cools a variety of products, allowing them to avoid spoilage for some time.

At the same time, not everyone knows certain features of this device: what the refrigerator consists of, where the cold comes 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 on their own: a decrease in air temperature is carried out inside the chamber during the operation of the unit.

This refrigeration equipment includes several main parts:

• coolant;
• evaporator;
• capacitor;
• compressor.

The compressor is a kind of 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 behind the refrigerator. The remaining parts are hidden in the inside of the chamber under the panel.

During operation, the compressor, like any motor, is subjected to significant heat, so it needs some time to cool down. So that this unit does not lose its performance due to overheating, a relay is built into it that 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, pumping the refrigerant, sends it inside 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. Excess heat is then dissipated in the room so that the cooling of the refrigerant occurs naturally. It is for this reason that it is forbidden to install heating devices near refrigerators.

The owners, who know about the principle of operation of the refrigerator, try to arrange the most optimal conditions for cooling the condenser and compressor for their "kitchen assistant". This allows you to extend its service 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 a gas. In this case, thermal energy is absorbed.
• 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 for nutritious foods not to freeze 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 desired values, the equipment automatically turns off.

Single chamber and double chamber models

The air-cooling unit in each refrigerator has a general device principle. However, there are still differences in the functioning of different equipment. They are based on the characteristics of refrigerant movement in refrigerated cabinets with one or a pair of chambers.

The scheme, which was presented a little higher, 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 required for stable and full-fledged operation of the refrigerator. For the freezer, the principle of operation will be the same.

The cooling compartment, in which the temperature does not drop below zero, starts only after the freezer has cooled down sufficiently and turned off. Just at this moment, the refrigerant from the freezer system is sent to the positive temperature chambers, and the evaporation / condensation cycle is already at a lower level, so it is impossible to say exactly how long the refrigeration equipment needs to work before automatic shutdown. It all depends on the setting of the thermostat and the volume of the freezer.

Quick freeze function

This function is typical for two-chamber 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 light up, indicating that the compressor is running. Here it is necessary to take into account the fact that the operation of the unit will not be stopped automatically, and too long operation of the refrigerator may adversely affect its condition.

After manual shutdown of the unit, the indicators will turn off by themselves and the compressor drive will turn off.

Modern refrigerators are equipped with a wide variety of functions. And today, housewives know about the existence of the automatic defrost function. Freeze-free and drip refrigeration systems have made human life much easier, but the principle of operation of the refrigerator has remained the same.