When you open the refrigerator door and feel cool, you rarely think about the complex physical processes occurring inside the metal box. Many people mistakenly believe that cold is generated by some special element, just like a light bulb emits light. In fact, there are no sources of cold as such in nature. Cold is just the absence of heat, and the task of household appliances is to actively select thermal energy from the internal space of the chamber.
The main engine of this process is compressorwhich is often called the heart of the unit. It is this that creates the pressure necessary for circulation refrigerant - a special gaseous substance that can easily pass from liquid to gaseous state and back. Understanding what exactly takes away heat from products will help you better understand malfunctions and more effectively use the capabilities of your equipment.
In this article we will analyze in detail the physical principles of the cooling system, consider the role of each component and answer the question of why this process is sometimes disrupted. You will learn how the cycle of converting steam into liquid and back works, and why Freon remains the most popular working fluid in modern models.
The principle of heat selection: physics of the process
To understand what exactly cools products, you need to remember the school physics course. Liquids evaporate and absorb heat from the environment. The simplest example: if you drop alcohol or ether on your skin, you will feel cold. The same principle underlies the operation of any refrigeration equipment. Inside the system circulates refrigerantwhich, passing through thin evaporator tubes, boils at very low temperatures.
During the boiling process, the refrigerant actively “pulls” thermal energy from the air inside the chamber. Thus, the products are not directly cooled, but give up their heat to the refrigerant. After the gas has taken heat, the compressor compresses it, increasing the temperature and pressure, after which the hot gas is sent to the condenser (grid at the back), where it releases the accumulated heat into the kitchen atmosphere.
⚠️ Attention: The efficiency of heat extraction directly depends on the tightness of the system. If a microcrack appears in the circuit, the refrigerant will evaporate and the heat absorption process will stop, despite the running motor.
The cycle is repeated continuously until the thermostat registers that the set temperature has been reached. It is important to understand that evaporator is the very element that is in direct contact with the air of the chamber and produces cold. The compressor only ensures the movement of the working fluid in a closed circuit.
Major components of the cooling system
The cooling system consists of several critical components, each of which performs its own function. If one of them fails, the entire process is disrupted. Let's look at the key elements that keep your chamber cold.
- ❄️ Compressor: motor, which creates pressure to circulate the gas.
- ❄️ Condenser: external radiator, where the gas cools and turns into liquid.
- ❄️ Capillary tube: a narrow channel where a sharp drop in pressure occurs.
- ❄️ Evaporator: internal radiator, where the liquid boils and cools the chamber.
Deserves special attention capillary tube. This is a very thin copper pipe that connects the condenser and the evaporator. It is at this point that the refrigerant expands sharply, causing its temperature to instantly drop. Without this pressure difference, boiling at low temperatures would be impossible.
In modern models with the system No Frost another important element is added - a fan. It forces air through the evaporator, distributing the cold throughout the entire volume of the chamber. In static refrigerators, the cold drops by gravity, which often leads to uneven cooling.
The role of the refrigerant: the blood of the refrigeration system
The refrigerant is a working substance that transfers heat from the products to the outside. In everyday life it is often called freon, although this is the name of a specific brand that has become a household name. Different models may use different types of gases, such as R600a (isobutane) or R134a. Each of them has its own physical properties and requirements for tightness.
Modern refrigerants are environmentally friendly and do not destroy the ozone layer, unlike older analogues. However, they require high precision when filling. A lack of gas will cause the evaporator to be only partially cold, and an excess will lead to an increase in pressure and load on the compressor.
| Refrigerant type | Features | Where used | Temperature boiling point |
|---|---|---|---|
| R600a (Isobutane) | Explosive, economical | Modern household models | -11.7 °C |
| R134a | Safe, high efficiency | Industrial and old household | -26.5 °C |
| R22 (Freon) | Harmful to the environment (prohibited) | Old Soviet refrigerators | -40.8 °C |
| R404A | High cooling capacity | Chest freezers, showcases | -46.5 °C |
Replacing the type of refrigerant during the repair process is impossible without reworking the entire system. If your refrigerator has been refilled R600a, you cannot use another gas, as this will lead to incorrect operation thermostat and possible breakdown of the compressor.
Why is R600a considered explosive?
Isobutane is essentially a household gas. In concentrations in air from 1.3% to 8.4% it forms an explosive mixture. That is why, when repairing such refrigerators, it is prohibited to use tools that produce a spark, and it is necessary to ventilate the room.
Differences between static and No Frost
The answer to the question “what cools” depends on the type of your refrigeration system. In classic models with static cooling, the cold is produced by an evaporator located behind the back wall or in the freezer compartment. Cold air sinks down, displacing warm air upward. This is natural convection.
In systems No Frost (or “complete No Frost”) the process is organized differently. Here the evaporator is hidden in a separate compartment, usually at the top of the cabinet or behind the freezer panel. A powerful fan drives air through this ice radiator and distributes it among the chambers through special channels.
- 🌀 In static conditions, cooling occurs unevenly, it is colder at the back wall.
- 🌀 In No Frost, the temperature is the same on all shelves thanks to forced circulation.
- 🌀 In No Frost, moisture is frozen on a hidden evaporator, so the products do not get airy.
The main advantage No Frost is the absence of the need for manual defrosting. However, such systems have a caveat: due to the constant operation of the fan and more complex design, they may consume a little more electricity. In addition, dry air dries out products faster if they are not packaged.
Why the refrigerator stopped cooling: the main reasons
If you notice that the products have started deteriorate, but the chamber has become warmer, which means that the heat extraction process is disrupted. The most common cause is a refrigerant leak. Even a microscopic hole in the circuit causes gas to escape and circulation stops. In this case, the compressor may work constantly, but there will be no cold.
The second common problem is a malfunction compressor. It may seize, burn out, or lose its ability to generate the required pressure. Also, the starting relay that starts the engine often fails. In such cases, the refrigerator either hums but does not start, or clicks and is silent.
⚠️ Attention: If you hear gurgling or hissing after turning off the compressor, this is normal. But if these sounds are constant and are accompanied by a lack of cold, the capillary tube may be clogged or the valve is broken.
In models with No Frost a common cause of loss of cold is a malfunction of the defrost system. If the heating element or defrost timer breaks, the evaporator becomes overgrown with ice, the fan stops moving air, and the cold stops flowing into the chamber. Outwardly, it may look like a running motor, but without results.
☑️ Diagnosis of lack of cold
How to extend the life of the cooling system
In order for evaporator and the compressor to serve for a long time, you must follow the operating rules. Do not overload the chamber with food so that it blocks the ventilation openings. Air circulation is the key to uniform cooling and no unnecessary load on the motor.
Regularly check the rubber seals on the doors. If they do not fit tightly, warm, moist air enters the chamber. This leads to increased formation of frost on the evaporator and frequent starts of the compressor. Wipe the rubber bands with a soft cloth and check their elasticity.
Do not place the refrigerator close to the wall or furniture. The condenser (black grille on the back or sides) needs fresh air to effectively remove heat. If heat does not escape into the room, the efficiency of the entire system will drop and energy consumption will increase.
The myth of defrosting
Modern refrigerators with No Frost do not require defrosting for the sake of cold, but once a year it is still recommended to turn them off for hygienic washing and checking the condition of plastic elements.
Frequently asked questions (FAQ)
Why is the back wall of the refrigerator covered with ice?
In static models this is normal, since the evaporator is located there. In No Frost models, an ice crust on the back wall of the main chamber indicates a malfunction of the defrost system or the door is not tightly closed.
Is it possible to replace the refrigerant yourself?
Absolutely not. This requires special equipment (vacuum pump, pressure gauges, scales) and a license. Unprofessional refilling will lead to compressor failure or explosion (in the case of R600a).
How long does it take for a refrigerator to get cold after defrosting?
Usually the process takes from 2 to 6 hours depending on the volume of the chamber and the type of refrigerant. It is recommended to load food no earlier than 8-10 hours after switching on.
Does the temperature in the room affect the operation of the refrigerator?
Yes, a lot. If the room is hot (above +30°C), the condenser releases heat worse, the compressor works longer and gets hotter. In a cold room (below +10°C), the refrigerator may not turn on at all, since the thermostat does not see the temperature difference.