The Device and Principle of Operation of the Refrigerator: Two-Chamber, Absorption

The device and principle of operation of the refrigerator: two-chamber, absorption

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The device, as well as the principle of operation of the refrigerator, is superficially studied in physics lessons, however, not every adult can imagine how the refrigerator works? Consideration and analysis of the main technical aspects will help in practice to extend the life and improve the performance of a household refrigerator.

Compression cooler device

The refrigerator device is best considered on the example of a compression sample, since such devices are most often used in everyday life:

  1. Compressor – a device that pushes the refrigerant (gas) with the help of a piston, creating different pressures in different parts of the system;
  2. Evaporator – a container into which the liquefied gas enters, absorbing heat from the refrigeration chamber;
  3. Capacitor – a container in which the compressed gas gives off heat to the surrounding space;
  4. expansion valve – a device that maintains the required pressure of the refrigerant;
  5. refrigerant – a mixture of gases (freon is most often used), which, under the influence of the operation of the compressor, circulates in the system, taking and giving off heat in its different parts.

Refrigerator operation

The most important aspect in understanding the operation of a compression apparatus is that it does not generate cold per se. Cold is caused by taking heat inside the device and sending it outside. Freon performs this function. Getting into the evaporator, which usually consists of aluminum tubes or plates soldered together, freon vapor absorbs heat.

You need to know: in old-style refrigerators, the evaporator housing is also the freezer housing. When defrosting this chamber, do not use sharp objects to remove ice, since all the freon will disappear through the pierced evaporator housing. A refrigerator without refrigerant becomes inoperative and is subject to costly repairs.

Further, under the influence of the compressor, freon vapor leaves the evaporator and passes into the condenser (a system of tubes that are located inside the walls and on the back of the unit). In the condenser, the refrigerant cools down, gradually becoming liquid. On the way to the evaporator, the gas mixture is dried in a filter-drier and also passes through a capillary tube. At the entrance to the evaporator, due to the increase in the inner diameter of the tube, the pressure drops and the gas becomes vaporous. The cycle is repeated until the required temperature is reached.

How does a compressor work?

With the help of a piston, the compressor distills the refrigerant from one pipe system to another, alternately changing the physical state of freon. When the refrigerant is supplied to the condenser, the compressor compresses it strongly, causing the freon to heat up. After going a long way through the labyrinth of condenser tubes, cooled freon enters the evaporator through an expanded tube. The sudden change in pressure cools the refrigerant rapidly. Now freon vapors are able to absorb a certain dose of heat and pass into the condenser tube system.

 

In household appliances, fully sealed compressor housings are used that do not allow the working gas mixture to pass through. For the purpose of tightness, the electric motor that drives the piston is also located inside the compressor housing. All rubbing parts inside the motor-compressor are lubricated with special oil.

The electrical circuit of the refrigerator can be useful for those who are ready for self-diagnosis and repair of the refrigerator:

 

The device and principle of operation of a two-chamber refrigerator

The device of a two-chamber refrigerator differs from a single-chamber one in that each compartment has its own evaporator. Unlike their predecessors, in two-chamber devices, both compartments are isolated from each other. In such devices, the freezer is usually located at the bottom, and the refrigeration part is at the top. The principle of operation of a two-chamber refrigerator is that the working gas mixture first cools the freezer evaporator to a certain sub-zero temperature. Only after that the freon passes into the evaporator of the refrigeration compartment. After the evaporator of the refrigerating chamber reaches a certain minus temperature, the thermostat is activated, which stops the operation of the motor.

The device and principle of operation of the refrigerator: two-chamber, absorption

In everyday life, two-chamber devices with one compressor are more often used. In units with two motors, the principle of operation of the refrigerator does not change significantly, just one compressor works for the freezer, the other for the refrigerator. It is generally accepted that the operation of a refrigerator with one compressor is more economical, but in reality this is not always the case. After all, in a device with two motors, you can turn off one of the cameras, in which there is no need. The operation of a two-chamber refrigerator with one compressor always involves the simultaneous cooling of both chambers.

Refrigerator and ambient temperature

The operating instructions for most household refrigerators indicate at what temperature it is best to operate it. The minimum allowable indicator is a temperature of +5 Celsius. Can the refrigerator work in cold conditions, especially in the cold? Consider possible problems:

  • The thermostat is not working properly. Under normal conditions, the thermostat breaks the electrical circuit when the required temperature is reached. When the air inside warms up, the thermostat will close the electrical circuit again, and the motor will resume its operation. In conditions of sub-zero ambient temperature, the thermostat most likely will not turn on the compressor again, since the heat inside the chamber simply has nowhere to come from;
  • Compressor difficult to start. In older devices, R12 and R22 refrigerants were most often used. For normal operation, refrigerant oils were used, which become too thick at temperatures below + 5 ° C, which means that the start and movement of the piston will be difficult;
  • The appearance of the effect of “wet run”. Since there is no heat in the refrigerator, the operation of the evaporator is disrupted. The vapor saturated with droplets enters the compressor. As a result of prolonged operation in such conditions, the entire mechanics of the motor will be damaged.

In simple words, a gentle attitude to the device will significantly extend its life.

The principle of operation of the absorption refrigerator

In the absorption apparatus, cooling is associated with the evaporation of the working mixture. Most often, this substance is ammonia. The movement of the refrigerant occurs as a result of the dissolution of ammonia in water. From the absorber, the ammonia solution enters the desorber, and then to the reflux condenser, in which the mixture is separated into its original components. In the condenser, the ammonia becomes liquid and is sent back to the evaporator.

 

Fluid movement is provided by jet pumps. In addition to water and ammonia, hydrogen or another inert gas is present in the system.

Most often, an absorption refrigerator is in demand where it is impossible to use a conventional compression analogue. In everyday life, such devices are rarely used, since they are relatively short-lived, and the refrigerant is a toxic substance.

Operation and rest mode of the compression refrigerator

Many users are interested in the question: how long should the refrigerator work? The only true criterion for the normal operation of a home appliance is a sufficient degree of freezing and cooling of food in it.

How long a refrigerator can work and how long it should rest is not spelled out in any instruction, however, there is the concept of “optimal working time ratio”. To calculate it, the duration of the working cycle is divided by the sum of the working and non-working cycle. So, for example, a refrigerator that has worked for 15 minutes with a further 25-minute rest will have a coefficient of 15/(15+25) = 0.37. The smaller this coefficient, the better the refrigerator works. If the result of the calculation is a number less than 0.2, then most likely the temperature in the refrigerator is incorrectly set. A coefficient greater than 0.6 means that the tightness of the unit is broken.

How does the No Frost refrigerator work?

In refrigerators with a no frost system (“no frost”), there is only one evaporator, which is hidden in the freezer behind a plastic wall. The cold from it is transferred using a fan, which is located behind the evaporator. Through the technological openings, cold air enters the freezer, and then into the refrigerator.

The device and principle of operation of the refrigerator: two-chamber, absorption

To justify its name, the No Frost refrigerator is equipped with a defrosting system. Several times a day, the timer activates the heating element located under the evaporator. The resulting liquid evaporates outside the refrigerator.

Just a few minutes, spendgiven to the study of the material, can in the future benefit the common man in the street, because, knowing the device and principle of operation, as well as the optimal operating conditions of the refrigerator, everyone will be able to extend the life of the home food keeper.

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