Many of us take a household refrigerator for granted: open the door - it’s cold there, close it - the food is preserved. However, the question of where exactly this cold comes from remains a mystery for most users, hidden behind the opaque walls of the case. In fact, cold is not created out of nowhere, it is the result of a complex physical process of transferring thermal energy.
Inside the device there is a constant struggle with heat penetrating through the thermal insulation from the external environment, as well as emitted by the products themselves. To understand the nature of this phenomenon, it is necessary to consider a closed circuit through which a special substance circulates, changing its state of aggregation under the influence of pressure.
The source of “cold” is not magic, but the laws of thermodynamics, which state that heat always moves from a more heated body to a less heated one. The task of the technology is to forcibly select this thermal energy inside the chamber and throw it outside into the kitchen.
The physical basis of cooling: evaporation and heat absorption
The key point in the operation of any refrigeration machine is the property of liquids to boil at low temperatures if the pressure is reduced. It is this principle that is used in evaporatorwhich is often called the “heart” of cold formation. When a liquid refrigerant enters a low-pressure zone, it begins to boil intensely, turning into gas.
The vaporization process requires a huge amount of energy. Since there is no external heat source nearby, the liquid begins to actively take this energy from the surrounding space - in this case, from the air inside the fridge compartment. As a result, the air cools down and the products are cooled.
It is important to understand that the refrigerant (previously freon was used, now more environmentally friendly mixtures are used more often) is only a heat transfer agent. It does not burn or is consumed during operation, but constantly circulates in a closed circuit, changing its state from liquid to gas and back.
⚠️ Attention: If you hear gurgling or noise of flowing liquid immediately after turning off the compressor, this is normal. This is how the refrigerant behaves, redistributing in the system after the pressure stops.
The effectiveness of this process directly depends on the tightness of the circuit. Even a microscopic gas leak disrupts the pressure balance, and the liquid stops boiling at the required temperature, which leads to a complete loss of refrigeration capacity.
Closed cycle device: from the compressor to capillary
For the cooling process to be continuous, the gaseous refrigerant must be converted back into liquid and returned to the evaporator. This is done compressor by a powerful electric motor that compresses the gas, increasing its pressure and temperature. The heated gas enters the condenser (the black grill on the back or sides of the housing), where it cools to room temperature and condenses, becoming a liquid.
Next, the liquid refrigerant passes through a filter drier, which removes moisture, and enters a very thin tube - a capillary. This is where the sharp drop in pressure occurs. Having passed through the narrow opening of the capillary, the liquid ends up in the expanded space of the evaporator, where the pressure is again low and the boiling cycle is repeated.
Modern models can be equipped with one or two compressors. In two-compressor systems, the circuits for the freezer and refrigerator compartments are separated, which allows you to independently regulate the temperature and save energy when operating one of the zones.
This entire system is controlled electronically or by a mechanical thermostat that monitors the temperature inside the chambers. As soon as the specified threshold is reached, the circuit opens and the motor stops until the next temperature increase.
The role of the refrigerant and types of refrigerants
The substance circulating inside the system must have specific physical and chemical properties: low boiling point, high heat of vaporization and chemical inertness. For decades, the standard was chlorofluorocarbons (CFCs), known as R-12.
However, these gases have been found to destroy the Earth's ozone layer. So the industry moved to hydrochlorofluorocarbons (HCFCs) and then to hydrofluorocarbons (HFCs) such as R-134a. Nowadays, natural refrigerants are becoming increasingly popular, for example, isobutane (R-600a), which has excellent refrigeration properties and zero potential for ozone destruction.
The use of different types of gases requires different oils to lubricate the compressor. Mineral oils are compatible with R-12, synthetic (polyester) oils are compatible with R-134a, and special blends are often used for R-600a. Mixing different types of oils and gases is strictly prohibited, as this leads to the formation of acids and blockage of the system.
| Refrigerant type | Marking | Features | Application |
|---|---|---|---|
| Freon (obsolete) | R-12 | Destroys ozone, high stability | Old Soviet and imported models |
| Tetrafluoroethane | R-134a | Safe for ozone, requires synthetic oil | Most modern refrigerators |
| Isobutane | R-600a | Explosive in high concentrations, economical | Modern energy-efficient models |
| Propane | R-290 | High efficiency, flammability | Industrial installations and some household |
Why can’t you mix refrigerants?
Mixing different types of gases (for example, R-12 and R-134a) leads to unpredictable changes in pressure in the system, destruction of compressor seals and the formation of aggressive chemical compounds that corrode the tubes from the inside.
Heat removal systems: static versus No Frost
After heat has been removed from the products, it must be effectively distributed or removed. Older and budget models use static system (Direct Cool). In it, cold air falls down naturally, and a “snow coat” of frost is formed on the back wall, which periodically thaws.
In systems No Frost (or Full No Frost) the cold is generated in a separate hidden evaporator, usually located in the upper part of the freezer or behind the back panel. The fan forcibly drives dry cold air through special channels, distributing it evenly throughout the entire volume.
This allows you to avoid the formation of ice on products and walls, but has its own characteristics. The air in such refrigerators is drier, which can lead to faster weathering of food if it is not packaged. In addition, the presence of a fan creates additional noise.
An important element of the No Frost system is the defrosting heating element. It is turned on by a timer or compressor hour meter, melting the ice on the hidden evaporator. The resulting water flows into a pan located above the compressor, where it evaporates from the heat of the running motor.
☑️ Signs of a working No Frost system
Common cooling circuit malfunctions
Understanding where the cold is coming from helps diagnose breakdowns. If the compressor runs continuously but there is no cold, there is most likely a refrigerant leak or a capillary tube blockage. In the first case, the gas escaped through a microcrack, in the second, the system became clogged with oil decay products or ice.
If the compressor turns on for a few seconds and turns off with a click (thermal relay), this may indicate an interturn short circuit in the motor winding or a wedge in the mechanical part. Attempts to start such an engine with a “kick” (start relay) usually give only short-term results.
Another common problem is a malfunction of the thermostat or temperature sensor. The electronics “think” that the chamber is already cold and does not give the command to start, although the food has defrosted. Or, on the contrary, it does not turn off the compressor, leading to deep freezing.
⚠️ Attention: If you smell burning or see that the tubes near the compressor are covered with frost, immediately unplug the device. Operation in this mode can lead to a fire or complete failure of the unit.
Diagnostics of system tightness requires special equipment: leak detectors, pressure gauge manifolds and vacuum pumps. At home, you can only visually inspect the tubes for oil stains (oil often comes out along with the gas) and listen to the operation of the motor.
Energy efficiency and the influence of operating conditions
We figured out where the cold comes from, but how much energy is spent on it? The energy class (A, A+, A++, etc.) shows how efficiently the refrigerator transfers heat. The higher the class, the better the insulation and the more efficient the compressor.
The operation of the system is affected by the ambient temperature. If the refrigerator is located near a radiator or in direct sunlight, the condenser cannot efficiently transfer heat. The compressor is forced to work longer and with greater load, trying to maintain the set temperature inside.
It is also important not to overload the chambers with food or place hot dishes. A sudden increase in temperature forces the system to work at its limit. Regular defrosting (for static models) and cleaning the condenser from dust at the back of the device will help maintain the efficiency of heat exchange.
Modern inverter compressors allow you to smoothly regulate power, avoiding peaks loads at start-up. This not only reduces noise, but also extends the life of the mechanism, making the cooling process more stable and predictable.
Questions and answers (FAQ)
Why does the back wall inside the refrigerator become covered with ice or water?
This is normal for refrigerators with a drip system (Direct Cool). Moisture from the air condenses on the cold back wall (where the evaporator is located), freezes, and then, when the compressor turns off, melts and flows into the drain hole. If there is too much ice, check the tightness of the door closure or the condition of the seal.
Is it possible to install the refrigerator in a niche without gaps?
No, this is strictly prohibited. For effective heat dissipation (condensation), air must circulate freely around the chassis, especially around the rear grille and sides. The minimum gap is usually 5-10 cm. Violation of this rule will lead to overheating of the compressor and increased energy consumption.
A loud click and hum is heard, but there is no cold - what is it?
Most likely, the start-up relay has failed or the compressor itself cannot start (jammed). The clicking sound is the work of the thermal protection. You need to call a technician to replace the relay or diagnose the motor.
How often do you need to defrost a No Frost refrigerator?
The No Frost system does not require manual defrosting to remove ice, as this happens automatically. However, it is recommended to completely turn off the refrigerator 1-2 times a year for washing, drying and treating with antibacterial agents, since bacteria can accumulate in the drainage system and on the shelves.