A technologically advanced, modern device of small size, indispensable on long, long trips and outings. The task of all car refrigerators is to maintain low temperatures in the sealed chamber where chilled food and drinks are stored. However, different types of cooling technology achieve this goal in different ways.
Refrigerators for cars are divided into four main types based on design complexity, cost, principles, and operating characteristics:
- compressor
- thermoelectric.
- absorption.
- cooler bags.
The latter type does not relate to technology and is designed to maintain the temperature of pre-chilled products. How auto-refrigerators of other categories work is discussed in more detail within the framework of this article.
Absorption refrigerator
An absorption (adsorption) refrigerator is a unit that operates by absorbing water. The refrigerant of the device is ammonia. It is this that dissolves in the liquid that is located in the technical part of the unit. Next, the aqueous solution moves under pressure to the generator, and from it to the reflux condenser. In the latter, the process of condensation of the solution begins, which leads to the separation of gas from the liquid.
When the process is over, the concentrated ammonia vapor will pass through the condenser, where it will again be compressed by external forces, and enter the evaporator. Water will enter the absorber. In this way, an almost continuous cooling process is carried out.
Such refrigerators are divided into types:
- gas;
- electrical;
- electric gas.
What does the absorption module consist of?
The absorption type involves the movement of refrigerant through the refrigeration system, which occurs due to the dissolution of ammonia in the water mass.
Absorption cycle
The main parts of an absorption refrigeration chamber are:
- Generator. The mixture saturated with ammonia is fed to the generator, where it boils. The generator (boiler) is heated by connection to the electrical network or by heat from gas combustion.
- Capacitor. It gives off heat to the surrounding space.
- Absorber. Ammonia vapors are sucked off by an absorber. This process is based on the difference in steam pressure - in the absorber it is significantly lower. In it, the ammonia-water solution absorbs ammonia vapor. Saturation of the ammonia-water mixture with ammonia occurs, accompanied by the release of heat. Therefore, the absorber is cooled by water.
- Evaporator. In the evaporation unit, located in the space being cooled, refrigerant vapors are separated from the ammonia-water composition during the boiling process. This is possible because the temperature at which ammonia boils is 33.4 degrees Celsius, that is, it is significantly less than the boiling threshold of water.
- Control valves. The refrigerant is directed to the desired device.
- Pump. Supplies supersaturated ammonia solution inside the generator.
Refrigerator refrigeration unit
These devices are connected by pipes and assembled into a closed circuit. The schematic diagram of a refrigerator operating using the absorption method is shown below.
"Morozko 3m": principle of operation
This unit operates on the absorption-diffusion principle. The work involves a system of seamlessly drawn pipes, which are made of steel. The system is sealed and has no parts that could move. The advantage of the refrigerator is that it operates silently.
The inert gas contained in the refrigerator allows you to establish uniform pressure throughout the technical part of the refrigerator. The movement of the ammonia-water solution is carried out under the action of a thermosiphon.
If we consider in detail the operation of the working part of the refrigerator, the process proceeds as follows:
- A solution of ammonia and water is heated.
- The heated liquid, brought to a boil, rises through the thermosiphon. This happens due to the fact that its density becomes less than the density of the second solution in the thermosyphon.
- As soon as the liquid leaves the tube, ammonia-water vapor begins to be released.
- The steam reaches the condenser through the regenerator.
- A condensation process occurs.
- The liquid gas enters the evaporator, where it again turns into steam.
The cycle repeats itself in a circle. Thanks to constant steam generation, a low temperature in the device is achieved.
Operating principle of the absorption refrigeration module
The principle of operation of an absorption refrigerator is as follows. The generator provides boiling of the ammonia mixture, which enters the condenser in vapor form. The unused low-concentrated ammonia-water mixture penetrates into the absorber, where it is saturated with ammonia.
Refrigerator device
The ammonia refrigerant vapor is received by the condenser. Ammonia boils in it and transforms it from a vapor state into a liquid state. Liquid ammonia is directed to the evaporator using a valve.
This process ensures that heat is taken in by the evaporator and transferred to the external space by the condenser. The generator is the pressure component of the absorption refrigerator circuit, and the absorber performs the suction of ammonia.
Unlike a compression refrigerator, an absorption refrigerator has 2 refrigerant flow circuits. The large chain ensures the operation of the system; ammonia-water liquid of varying degrees of saturation passes through the small chain.
How does a gas refrigerator work?
Gas units have a distinctive feature: they are able to operate even without access to electricity. The principle of their operation is to use gas, which is produced by connecting the unit to a gas pipeline or gas cylinder.
In this case, the water-ammonia solution is heated by gas. This happens in the absorber, where ammonia is mixed with water and then enters the evaporator. In the evaporator, ammonia is separated from water due to evaporation, as a result of which cooling occurs inside the refrigerator chamber.
Important! Gas requires careful handling, as it can be very dangerous if all conditions for safe operation are not provided.
Types of absorption auto-refrigerators
Such equipment is only a subclass of cooling equipment, but requires an even deeper classification.
The first criterion is the heat sources used.
Cooling is carried out as a result of heating the ammonia-water mixture; it can be heated either directly by fire from diesel fuel or natural gas, or by steam or water heated by it (75-200 and 75-95 degrees, respectively). Electric models are especially popular, where water is heated using metal heating elements.
Car refrigerators can be stationary or portable.
Stationary models have significant dimensions and weight, and are not equipped with handles convenient for transportation, but they are equipped with plugs for a 220V socket and are used outside the car.
Portable ones are designed for constant movement, so they are designed to work from a gas cylinder or cigarette lighter.
Only stationary models are classified according to the type of construction and installation methods. There are floor-mounted, wall-mounted and built-in varieties.
Operating principle of the ammonia device
The operating principle of an ammonia refrigerator is to evaporate ammonia in water. A solution of water and ammonia enters the reflux condenser. Its purpose is to decompose the solution into its components, after which the ammonia gas is compressed again and passes into the evaporator. Actions are repeated in a circle.
Interesting! Sometimes hydrogen is added to the system, and the resulting cooling occurs due to a change in partial pressure. Such refrigerators make small camping forms for tourists.
Advantages and disadvantages
Absorption refrigerators are not the most popular, so you need to weigh the advantages and disadvantages before purchasing.
Advantages
- significant energy savings; when operating on gas or fuel, there is no need for it at all;
- very quiet operation;
- high degree of environmental safety - in modern models there is much more water than ammonia;
- operation without breakdowns continues for 20 years;
- fire safety.
Flaws
- significant cost of equipment;
- in low-quality models, the dissolution of ammonia in the water mass occurs with the release of heat without its removal, this noticeably heats the entire system and partially neutralizes its effect;
- ammonia, albeit in reduced concentration, is used in most systems, and it is hazardous to health;
- A breakdown is a death sentence for an absorption refrigerator; it cannot be repaired.
Absorption refrigerator that does not consume electric current
Such a refrigerator is a unit powered by a heating boiler. The principle of operation is designed in such a way that the heat generated as a result of cooling the refrigerator is used for heating, and the unit itself operates from a heating boiler. Energy power is expended only to provide heating.
Important! It is worth noting that the system is still in development, but such refrigerators may actually appear soon.
Features of car refrigerators powered by a cigarette lighter
Car owners use installations that produce cold in the three ways mentioned above and choose refrigeration equipment depending on:
- vehicle capabilities, interior or trunk capacity;
- duration of trips, number of people participating in them;
- temperature characteristics, time required to reach the desired temperature;
- the condition of the road surfaces on which you often have to travel;
- the cost of refrigeration equipment.
The selected units are of compressor, absorption or thermoelectric type, united by the ability to connect them to the car’s cigarette lighter. In this case, the electricity powering the installation comes from the battery. The peculiarity of the principle of operation of a car refrigerator from a cigarette lighter is the presence of additional electrical equipment in the circuit and a special wire for connection.
If you choose a ready-made model of any type, you need to pay attention to whether it comes with a special connecting cord and how long it is. The ideal combination is the operation of refrigeration equipment from the cigarette lighter and a standard 220V network. This technique can be used on the road and at home. It is important to consider the length of the wire in order to install the refrigerator in the cabin or trunk.
Absorption gas-electric unit
Many people prefer to call such devices electric gas. Such devices have a number of advantages, including:
- silent operation;
- compact size;
- efficiency;
- long service life, rare calls for repair service.
Also, such refrigerators can be installed in cars running on gasoline or gas.
Watch this video on YouTube
Operating principle of minibar absorption unit
Watch this video on YouTube
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Main Applications
Absorption refrigerators are not picky about power sources - the unit can be powered from a stationary outlet, from the vehicle’s on-board system, or from a gas cylinder. This allows you to use the device anywhere, including on the go – right in the car. A car refrigerator of small capacity and power lasts for a month on a five-liter cylinder, which is why it is in demand among frequent travelers.
The use of absorption refrigerators is relevant in dacha conditions, when the owners appear intermittently and do not store a lot of food. The device is also suitable in all regions where the power supply is unstable - thanks to an alternative heating source in the form of the same gas cylinder, uninterrupted cooling of products is guaranteed.
The working principle of a thermoelectric refrigerator
To reduce the temperature in the refrigerator compartment, heat is pumped out of it by a special system. This is ensured by the well-known Peltier effect. This type of refrigerator contains cube-shaped thermoelectric elements made from various metals and connected by electricity. When electric current passes from one metal to another, heat also passes with it . An aluminum plate absorbs heat from the food in the refrigerator, and the cubic elements transfer it to the stabilizer, which in turn dissipates it outside through a fan. Most Nord portable refrigerators work precisely on this principle.
Each of these types has its own positive and negative aspects, taking into account which the choice of a refrigeration device for domestic or industrial needs should be based.
Basic elements of a refrigerator
No refrigerator will be able to work if it is missing at least one of the main structural elements:
- Coolant. Its role is played by a gas moving in a closed circle and transferring heat.
- Capacitor. A device that removes heat from the refrigeration chamber to the outside. Presented in the form of a grille on the back of the refrigerator.
- A compressor is a motor that pumps up pressure and forces gas to move through a closed system.
- An evaporator is a device that removes heat. Most refrigerators use the back wall as the evaporator.
Adsorption refrigerators
Adsorption refrigerators are not too rare, but are often unknown to the public. It seems incredible that cooling is achieved by burning gas. Today there is an idea of creating an adsorption refrigerator powered by solar energy. The exact date of creation of the first model is unknown. During the Cold War, the design of the device was classified for use in the military and space industries; the creation of an adsorption refrigerator seemed too profitable. The information was removed from textbooks, and this continued until the conference in Paris in 1992. Some data on the first adsorption refrigerators are extracted from specialized textbooks published before 1960.
Let's talk about terms. Absorption and adsorption refrigerators are mentioned in the literature. These are related designs that work on varieties of sorption; some writers make mistakes, not really knowing the meaning of what is happening. More important is the fact that equipment of this type exists, operating through cycles of absorption and return of refrigerant by adsorbent granules or liquid absorbent.
The difference between the phenomena underlying the work:
- The absorbent absorbs the substance throughout its entire volume.
- In the case of adsorption, we are talking only about the surface layer; the absorbed substance does not penetrate deeper.
Taking into account these considerations, it is not difficult to understand the confusion that has arisen in the household appliances section. A liquid sorbent is called an absorbent, and a solid (in granules) is called an adsorbent.
What is the prospect
This invention could be a real breakthrough in the field of cooling equipment. After all, eliminating freon and pumps from the cooling process will significantly reduce the size of the unit itself and simplify the maintenance of such devices. The magnetic refrigerator can be used not only in household appliances, air conditioners and heat pumps. If anyone has not yet read our article about this equipment, I recommend everyone to read it at this link. This invention can be used in cars, various industrial units and much more. It will significantly increase the energy efficiency of such systems and allow you to save on electricity.
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I hope the article was clear and useful. I am very pleased that domestic young scientists help the development of world science and modern technologies. We look forward to the completion of testing and the start of mass production of the magnetic refrigerator. In my opinion, this is an excellent option for replacing the old one.
How to tell if a refrigerator is quiet or noisy
Special standards are imposed on household appliances, indicating what characteristics the equipment must have in order to fall into a certain group. Often interpretations of laws overlap, contradicting each other. The document applicable to quiet refrigerators is ST SEV 4672-84. Despite the antiquity of the document, it is valid. Regarding refrigerators, data is provided there that allows for classification:
- Group A:
- Up to 200 liters – 40 dB.
- From 200 to 400 liters – 43 dB.
- Over 400 liters – 50 dB.
- Group B:
- Up to 200 liters – 42 dB.
- From 200 to 400 liters – 45 dB.
- Over 400 liters – 55 dB.
- Group C:
- Up to 200 liters – 53 dB.
- From 200 to 400 liters – 55 dB.
- Over 400 liters – 60 dB.
The class of a refrigerator in terms of noise is determined by its volume. Let us add that inverter compressors today are capable of providing 42 dB (expensive Liebherr models reach 38 dB), but we have never observed a lower level. Adsorption refrigerators clearly fall into group A. There is simply nothing to make noise in the devices, only the refrigerant rustles slightly. Choosing the quietest refrigerator means choosing a synonym for the word adsorption. There are no options.
How to measure the noise of a refrigerator? The method is based on adjusting sound pressure, excluding from the spectrum frequencies that are not audible to the human ear. This applies to compressors capable of producing ultrasound. As for adsorption refrigerators, there is no need to make any adjustments; the measured sound pressure will become the desired parameter. For the purposes of the experiment, you will need a microphone and a work methodology.
The quiet refrigerator under test is installed indoors without sound reflection. For domestic conditions, you will need a suspended ceiling and carpets on the floors and walls. The composition of the equipment is determined according to ST SEV 1351-78 or ST SEV 1807-79. The refrigerator is installed on a hard floor at a distance of 15 cm from the sound-reflecting wall. Let's say a piece of ordinary painted concrete. The nearest corner is at a distance of at least 1.5 m. Microphones are located as in the drawing.
where d – at least 1 m; a, b, c are chosen based on reasonable limits. The surface area of the measurement is found by the formula:
S = 2 (2ac + 2ab + bc), in fact, the area of the parallelepiped minus the floor and the rear concrete wall.
Before measurement, the refrigerator runs for 6 hours on medium mode, then breaks for 10 minutes. After the device is turned on again, after 3 minutes a measurement is taken. The results are processed according to the document ST SEV 541-77 (GOST 23941-2002).
Features of compressor refrigerators
The high-performance and most common refrigerators in everyday life are compressor refrigerators. As the name suggests, they assume a compressor. It is this unit that is the heart of refrigeration machines; it is responsible for circulating the refrigerant through the pipes of the system, due to which the low temperature in the chambers is maintained. Today you can buy a compressor-type refrigerator, either a simple single-chamber or a multi-chamber one. Volume up to 500 liters and even more. With the ability to adjust the cooling temperature. Without the need for periodic defrosting (with No Frost function).
Types of compressor units
Household refrigerators that make noise during operation, rumble, vibrate a little, and even shudder when the electric motor starts—with a linear compressor. They work cyclically. When the sensor, which has detected an increase in temperature in the chambers, is triggered, the compressor turns on at full power and the chamber is cooled. The temperature has dropped to the set point - the sensor gives a signal again, the compressor turns off just as abruptly as it turned on. The sensor continues to monitor the temperature. Then the cycle repeats.
More advanced models - with an inverter compressor.
The inverter-type compressor operates smoothly, without abrupt switching on and off. To maintain the set temperature in the chamber, it does not turn off completely, but only reduces the speed to a minimum at the right moment.
Refrigerators with an inverter compressor are practically silent, consume less energy than linear units, but are more expensive.
Disadvantages of adsorption refrigerators
The noise parameters of adsorption-type refrigerators are limited by the gurgling of the refrigerant, but the type of equipment exhibits disadvantages:
- Consumes excess energy.
- It takes a long time to get into working mode (on average, half an hour).
- Does not tolerate tilts and distortions relative to earthly gravity.
- Ammonia and other refrigerants are simply dangerous; the substances have long been abandoned in compressor models.
To sum it up, let's say that companies producing the quietest refrigerators are obliged to satisfy the consumer's interest. Today the technique is popular among fishermen: it is better than freezing fish with a carbon dioxide fire extinguisher. However, complaints about the low reliability of the technology, which, according to scientists, can work forever, in the absence of moving parts, give reason to think that not everything is so smooth in the field of adsorption. Reviews of quiet refrigerators confirm the advantages and disadvantages of the devices, until the authors mentioned the high price of the equipment. As users note, for a lot of money you want less complexity and more reliability.
