Every day we open the door of a household appliance to get food, without even thinking about the complex physical processes hidden behind the white walls. Many people believe that cold is simply "produced" inside the chamber, just as a lamp produces light, but this is a fundamental misconception. In fact, refrigeration technology does not create cold, but only intensively takes heat from the internal space and throws it out.
This phenomenon is based on the second law of thermodynamics, which states that heat spontaneously transfers from more heated bodies to less heated ones. To start the reverse process and cool the products, external work is required, which is performed by compressor. It is the forced circulation of the refrigerant that allows us to enjoy coolness even on a hot summer day, turning an ordinary metal box into an effective freshness preservative.
Understanding the principle of why it is cold in the refrigerator will help you not only be more careful with your appliances, but also save energy. If you know how the system works, you can more easily diagnose problems such as insufficient cooling or excessive ice build-up. Let's dive into the technical details to understand what exactly causes the temperature inside the chamber to drop below the surrounding environment.
Key principle: taking heat, not creating it
Key point to learn: cold is the absence of heat. When you feel a chill, you are actually experiencing the process of heat energy being removed from your body or food. In the refrigeration chamber this process is organized cyclically and continuously. A special substance called refrigerant (often freon) circulates in a closed circuit, changing its state of aggregation.
The process of evaporation of liquid is always accompanied by the absorption of heat. Remember how cold your hand becomes if you wipe it with alcohol or acetone: the liquid evaporates, taking away thermal energy from the surface of the skin. A similar principle works inside evaporator the refrigerator. The refrigerant, being in a liquid state under low pressure, boils at very low temperatures and actively absorbs heat from the air of the chamber.
⚠️ Attention: If you hear gurgling or hissing immediately after turning off the compressor, do not be alarmed. This is a normal physical process of refrigerant flowing and changing pressure in the system, and not a sign of a breakdown.
After the refrigerant has absorbed heat and turned into gas, it must release this energy to the external environment so that the cycle can repeat. This is why the back wall or side panels of a running refrigerator often feel warm to the touch. This is the heat that was removed from the internal volume of the chamber, plus the additional energy expended by the compressor on compressing the gas.
The heart of the system: the role of the compressor and condenser
The driving force of this entire system is compressor. This is an electromechanical pump that creates the necessary pressure to circulate the refrigerant. Without it, freon would simply sit in the tubes, and heat exchange would be impossible. The compressor compresses the gaseous refrigerant, significantly increasing its temperature and pressure, after which it sends the hot gas to the condenser.
The condenser is the same black coil that is usually located on the back wall of the device (although in modern models it can be built into the side walls of the case). Passing through a long condenser tube, the hot gas gradually cools and turns into a liquid state, releasing heat into the kitchen air. This process is called condensation, and it is critical to operating efficiency.
If the condenser is contaminated with dust or pet hair, heat transfer is impaired. The compressor has to work longer and harder to cool the refrigerant to the desired temperature. This leads to increased energy consumption and accelerated wear of the motor. Regular cleaning of the rear grill is an easy way to extend the life of the unit.
It is important to note that in modern inverter models the compressor does not turn off completely, but only reduces the speed. This allows you to maintain a more stable temperature and reduces noise levels. Unlike older linear models that operate in a start-stop mode, inverter motors provide smooth power control.
Refrigerant circulation: path from liquid to gas
To understand why it is cold in the refrigerator, you need to trace the full path of the refrigerant. After leaving the condenser, where it has become a liquid, the freon passes through a filter drier to remove moisture. Then it enters capillary tube or the thermostatic valve. Here there is a sharp drop in pressure.
Having entered the evaporator, which is located inside the freezer or refrigeration chamber, the refrigerant begins to boil rapidly even at subzero temperatures. At this moment, it actively “sucks” heat from food and air. Having passed through the evaporator, the refrigerant again becomes a gas and returns to the compressor, completing the circle.
- ❄️ Evaporator: zone of active boiling and heat absorption inside the chamber.
- 🔥 Condenser: zone of cooling and heat transfer to the external environment.
- 💨 Compressor: pump that creates a pressure difference for the movement of freon.
- 💧 Capillary tube: throttle, sharply reducing the pressure in front of the evaporator.
The length of the capillary tube and the diameter of its hole are calculated by engineers with high accuracy for each specific model. If there is a blockage or leak in the system, the pressure balance will be disrupted and the refrigerator will stop cooling. That is why independent repair of the circulation system without special equipment and skills is practically impossible.
What will happen if there is air left in the system?
The presence of air in the refrigerant circulation circuit leads to an increase in condensation pressure. This causes overheating of the compressor, increased energy consumption and can lead to ruptured tubes or motor failure.
Cold management: thermostats and electronics
The refrigerator should not freeze indefinitely, otherwise the food will turn into ice blocks, and the compressor will burn out from overload. To control the temperature, it is used thermostat (in mechanical models) or an electronic sensor (in models with control No Frost). These devices constantly monitor the temperature inside the chamber.
When the temperature reaches the set value, the thermostat opens the electrical circuit and the compressor stops. The chamber gradually heats up from the heat of the food and the environment. As soon as the temperature rises above the set threshold, the sensor again gives the command to start. The difference between the on and off temperatures is called the differential.
Modern control systems can use several sensors: one in the freezer compartment, another in the refrigerator compartment, and a third to control defrost. The electronic unit processes this data and decides whether to turn on the compressor or fans. This allows you to achieve high accuracy and stability of the temperature regime.
| Sensor type | Location | Function | Fault symptom |
|---|---|---|---|
| Thermostat | Inside the chamber or on the wall | Turning on/off the compressor | The refrigerator does not turn on or off |
| Defrost sensor | On the evaporator | Defrost control | Increasing "fur coat", no defrosting |
| Temperature sensor | Air duct or rear wall | Data transfer to the board | Incorrect temperature, error on display |
| Fan sensor | In the evaporator area | Flow control | Noise, lack of air circulation |
If you notice that the refrigerator starts working continuously or, conversely, turns on too rarely, the problem may be in the sensor. However, before drawing conclusions, it is worth checking the settings and the tightness of the door.
No Frost system: how the cold is distributed evenly
In classic refrigerators, it is coldest at the back wall, where the evaporator is located, and it can be warmer at the door. System No Frost (No frost) solves this problem using forced air circulation. In such models, the evaporator is hidden in a special compartment, usually at the top of the freezer or behind the back panel.
The fan drives cold air from the evaporator through channels into the chambers. Thanks to this, the temperature is equalized throughout the entire volume, and ice does not form on the walls. The air is constantly mixed, which ensures the same storage conditions on different shelves. This is especially important for products that are sensitive to temperature changes.
⚠️ Attention: In No Frost systems, products may ventilate faster due to the constant movement of dry air. Use containers with lids or cling film for storage.
Periodically, the No Frost system automatically switches to defrost mode. The heating element (heating element) turns on and melts the ice accumulated on the hidden evaporator. The water flows into the pan and evaporates. The user does not need to do anything - everything happens automatically. This eliminates the need for manual defrosting every few months.
☑️ Checking the No Frost system
The influence of the external environment and proper operation
The efficiency of the refrigerator directly depends on the conditions in which it is located. If the room is too hot, the compressor has a harder time transferring heat through the condenser. Therefore, it is not recommended to install the refrigerator next to a stove, a radiator, or in direct sunlight.
Frequently opening the door also disrupts the temperature regime. Warm, moist air enters the chamber, which condenses on cold surfaces and turns into frost. The compressor has to work longer to compensate for the added heat. Try to minimize the time when the door is open.
The load on the refrigerator also plays a role. An empty refrigerator cools faster, but also heats up faster when the door is opened. A refrigerator full of food or special cold accumulators keeps the temperature more stable, since food has a high heat capacity. However, do not overcrowd the chamber - air should circulate freely between the products.
Check the rubber seals on the doors regularly. If they are worn out or dirty, cold air will flow out and warm air will flow in. A simple test with a sheet of paper will help check the tightness: clamp the sheet with the door and try to pull it out. If the sheet is pulled out without effort, the seal requires replacement or adjustment.
Frequently asked questions about the operation of the refrigerator
Why does the refrigerator sometimes make a loud click?
A click is most often made by the thermostat when starting or stopping the compressor. This is normal operating sound. However, if the clicks are frequent and the refrigerator does not start, the start relay or the compressor itself may be faulty.
Is it possible to put a hot pan in the refrigerator?
It is strictly not recommended. A hot object will create a localized source of heat, causing the compressor to wear out. In addition, condensation from hot food can lead to freezing of the evaporator and disruption of the No Frost system.
Why are there different temperatures in different corners of the refrigerator?
In models without No Frost, it is coldest at the back wall. In models with a fan, the temperature should be even, but cold air is heavier than warm air, so it may be slightly colder below than on the upper shelves. Take this into account when placing food.
How often should you defrost the refrigerator?
No Frost systems do not require manual defrosting, but it is recommended to turn off the appliance once a year for washing and drying. Older models with a drip system or static cooling need to be defrosted as ice forms (usually 1-2 times a year).
Does the height of the shelves affect cooling?
Yes, it does. Do not block the vents (if your model has them) with food. Air should flow freely around all products. If the shelves are packed tightly, “heat pockets” may form in the center of the chamber, where food will deteriorate faster.