Inside every household refrigerator there is a continuous and complex physical process that allows you to keep food fresh for many months. The central role in this invisible work is played by a special working substance known as refrigerant. It is its circulation in a closed circuit that removes heat from the inner chamber to the outside, creating the necessary microclimate for storing food.
Many users mistakenly believe that cold is “pumped” into the refrigerator or produced magically, but in fact, the equipment only transfers thermal energy. Understanding how refrigerant workswill help owners better understand the causes of possible breakdowns and operate the device more efficiently. In this article, we will examine in detail the thermodynamic cycle, the properties of various types of gases and methods for diagnosing leaks.
The fundamental principle is the ability of a liquid to absorb huge amounts of heat when evaporating. The refrigerant in the refrigerator works according to this law, constantly changing its state of aggregation from gas to liquid and back. This process requires a sealed system, a compressor to create pressure and heat exchangers for efficient energy transfer.
Physical properties and types of modern refrigerants
The choice of a working substance for refrigeration equipment is always a compromise between efficiency, safety and environmental friendliness. The substance must have a low boiling point at atmospheric pressure, a high heat of vaporization and chemical inertness with respect to the system materials. Historically, the industry has evolved from the use of ammonia and sulfur dioxide to modern synthetic compounds.
The most widespread in the past were fluorinated hydrocarbons, known as freons. They are non-toxic, non-flammable and odorless, which made them ideal for household use. However, it later became clear that some types of freons, when released into the atmosphere, destroy the Earth's ozone layer. This has led to a global revision of standards and the introduction of new, more environmentally friendly, but often flammable analogues.
⚠️ Attention: Modern refrigerants such as R600a (isobutane) are flammable. It is strictly forbidden to open the pipelines of the system without professional equipment and skills, since a spark from the tool can lead to an explosion of the gas mixture.
Today, two main types of substances can most often be found in household refrigerators. The first is R134a, which replaced the ozone-depleting R12. It is safe, but has a high global warming potential. The second, which is gaining popularity, is natural gas, which is efficient and environmentally friendly, but requires increased care during installation and repair due to its explosion hazard. R600a, natural gas, which is efficient and environmentally friendly, but requires increased care during installation and repair due to its explosion hazard.
Thermodynamic cycle: four stages of cooling
The operation of the refrigeration system is based on a closed cycle, which is repeated continuously as long as the device is plugged in. This process can be divided into four key stages, at each of which the refrigerant changes its physical parameters. Understanding these stages is necessary for diagnosing malfunctions, since a violation at any stage leads to a loss of cooling capacity.
The first stage is compression. Compressor, being the heart of the system, sucks gaseous refrigerant of low pressure and temperature from the evaporator. Inside the cylinder or chamber of the compressor, the gas is subjected to sudden compression, as a result of which its temperature and pressure increase critically. At the exit from the compressor, we receive hot gas under high pressure, ready to give up its heat to the environment.
Next follows the condensation stage. The hot gas enters the condenser - this is the same black grill on the back wall of most refrigerators. Here, blown by natural or forced air flow, the refrigerant cools. By giving off heat to the kitchen, the gas turns into a liquid state, while remaining under high pressure. It is at this moment the main selection of heat occurs from the internal volume of the refrigeration chamber transferred by the refrigerant.
The third stage is throttling. High pressure liquid refrigerant flows to a capillary tube or expansion valve. Passing through a very narrow hole, the substance expands sharply, which leads to a drop in pressure and temperature. The refrigerant turns into a low temperature vapor-gas mixture, ready to boil. This pressure difference is the driving force of the entire cycle.
The final stage is evaporation. The cold mixture enters the evaporator located inside the freezer or refrigerator. Taking heat from the food and air inside the chamber, the refrigerant boils and completely turns into a gaseous state. After this, the cycle repeats: the gas is again sucked into the compressor. Violation of the tightness at any stage breaks this cycle.
☑️ Signs of normal operation of the cycle
The role of the compressor and capillary tube
These two elements create the necessary conditions for the circulation of matter. The compressor provides the movement, and the capillary tube creates the pressure difference. Without this connection, the refrigerant would simply stand in the pipes without performing its function. Compressors come in piston, linear, and inverter types, and each type has a different effect on the efficiency of gas compression.
The capillary tube is a long copper tube of very small diameter. It serves as a hydraulic resistance, dividing the circuit into a high-pressure zone (before the tube) and a low-pressure zone (after the tube). The length and diameter of this tube are calculated by the manufacturer's engineers to the nearest millimeter for a specific type of refrigerant and compressor power.
If the capillary tube becomes clogged in the system, circulation will stop. The compressor will operate under vacuum, trying to pump gas, but the refrigerant will not be able to get into the evaporator. As a result, the chamber is warm, and there is no cold on the back wall. Conversely, if the tube is too short or wide, the pressure will not drop sufficiently, and boiling will begin at a higher temperature, which will not allow the desired cooling to be achieved.
Why can’t you replace the capillary tube with an “eye”?
The length and diameter of the capillary tube are strictly calculated for the volume of the compressor and the type of refrigerant. Using an unsuitable tube will either result in insufficient cooling or overload and burn out the compressor.
Modern models with the system No Frost often use a thermostatic expansion valve (TEV) instead of a capillary tube. The expansion valve is capable of dynamically changing the flow area depending on the temperature at the outlet of the evaporator, which makes the operation of the system more stable under changing loads. However, most budget and mid-range models still use the classic capillary system.
Table of characteristics of popular refrigerants
To understand the differences between substances, it is important to consider their physical parameters. The boiling point at atmospheric pressure determines how low the temperature the system can reach in the evaporator. Global Warming Potential (GWP) and Ozone Depletion Potential (ODP) are key environmental indicators regulated by international protocols.
| Refrigerant Type | Chemical Formula | Boiling Point (°C) | Flammability | Effect on ozone |
|---|---|---|---|---|
| R12 (Freon) | CCl2F2 | -29.8 | No | High |
| R134a | CH2FCF3 | -26.1 | No | Zero |
| R600a (Isobutane) | C4H10 | -11.7 | Yes (high) | Zero |
| R290 (Propane) | C3H8 | -42.1 | Yes (high) | Zero |
As can be seen from the table, the transition to environmentally friendly gases is often associated with a change in their flammability. R600a has a higher boiling point than R12, which requires more effective thermal insulation and fine-tuning of the system, but allows for excellent energy performance. Using the wrong gas can lead to compressor failure or insufficient cooling.
Diagnostics of leaks and system malfunctions
You can determine that the refrigerant in the refrigerator is not working correctly or that a leak has occurred using a number of indirect signs. Since the system is sealed, the gas does not disappear anywhere on its own unless the integrity of the circuit is compromised. Most often, leaks occur in solder joints, in the foamed part of the housing (evaporator) or in the condenser due to corrosion.
The first sign of problems is the continuous operation of the compressor without shutdowns. Trying to gain temperature, the sensor does not give the command to stop, and the motor wears out. At the same time, it may be warm inside the chamber, or the freezer is working, but the temperature in the refrigerator compartment is higher than normal. There may be no characteristic uniform cooling or frost on the back wall.
For accurate diagnostics, technicians use leak detectors - devices that capture gas molecules in the air. The nitrogen pressure test method is also used: the system is pumped up with pressure and the pressure gauge is monitored. If the pressure drops, it means the seal is broken. Visually, you can notice oily stains in places of leakage, as the refrigerant circulates along with the compressor oil.
⚠️ Attention: If you hear hissing or smell a specific smell (although many gases are odorless, the smell can be caused by oil or impurities), immediately unplug the refrigerator and ventilate the room. Do not try to find a leak with an open flame.
It is important to distinguish between a leak and a blockage. When clogged, the compressor may also hum, but the condenser will only be cold or warm at the beginning, and the suction pressure will be lower than normal. Repair in both cases requires calling a specialist, since it is necessary to vacuum the system and accurately fill the gas by weight.
Environmental aspects and the future of refrigeration technologies
The refrigeration industry is in a constant search for a balance between efficiency and safety for the planet. Following the Montreal Protocol, which limited the use of ozone-depleting substances, and the Kyoto Protocol, aimed at reducing greenhouse gases, manufacturers are forced to implement new solutions. The future belongs to natural refrigerants and mixtures that do not harm the environment.
One of the promising areas is the use of CO2 (R744) as a refrigerant. Carbon dioxide does not burn, is non-toxic and has zero ozone depletion potential. However, its operation requires systems operating at very high pressure, which makes the technology expensive and difficult for mass household use. However, in industrial refrigeration this is already a reality.
Magnetic cooling technologies and absorption refrigerators are also being developed, where circulation occurs without a mechanical compressor, due to thermal effects. However, the classic compression cycle using fluorinated or hydrocarbon gases remains dominant due to the proven technology and high reliability.
It is important for users to understand that proper disposal of old refrigerator is a contribution to environmental protection. You cannot simply throw equipment into a landfill where the refrigerant can escape into the atmosphere. Specialized collection points ensure safe extraction and neutralization or regeneration of gases.
Frequently asked questions (FAQ)
Is it possible to fill a refrigerator with freon yourself if you have a cylinder?
It is strictly not recommended. Refilling requires evacuation of the system (removing moisture and air), accurate weighing of the gas (an error of 5-10 grams is critical) and the use of special tools. Unprofessional refilling will lead to compressor failure or explosion.
Why do new refrigerators have less gas than old ones?
Modern refrigerants (for example, R600a) have a higher refrigerating capacity, so to achieve the same effect, much less is required (about 30-50 grams versus 100-150 gram for old R12). In addition, a smaller amount of flammable gas is safer.
How long does the refrigerant last in a refrigerator?
In a perfectly sealed system, the refrigerant is not consumed and can circulate for decades without replacement. If the gas disappears somewhere, it means that there is a microcrack in the system or poor-quality soldering that requires repair.
Is the smell from the refrigerator dangerous for health?
The most modern gases (R600a, R134a) in low concentrations are not toxic to humans. However, if there is a large leak in a confined space, there is a risk of suffocation (oxygen displacement) or fire (for R600a). If you suspect a leak, you need to ventilate the room.
Can the refrigerator operate without refrigerant?
No. Without a working fluid, the heat transfer process is impossible. The compressor will simply drive empty space, quickly overheat and burn out, and cooling will not occur at all.