Every day we open the door of a household appliance to get products, without thinking about the complex physical and chemical processes occurring inside its case. The refrigerator compartment keeps food fresh thanks to a continuous cooling cycle, which is ensured by the coordinated operation of several key components. Understanding how a compressor refrigerator workswill help the owner to operate the equipment correctly, notice signs of malfunction in time and extend the life of expensive equipment.
Modern climate control technology is based on the principle of taking heat from the internal chamber and transferring it to the environment. This process is impossible without a special working substance - a refrigerant, which circulates in a closed circuit, changing its state of aggregation. It is phase transitions substances that make it possible to effectively cool products, turning gas into liquid and back under the influence of pressure.
The main “heart” of the system is an electromechanical unit that creates the necessary pressure in the pipelines. Without this component, circulation of freon would be impossible, and the temperature inside the chamber would quickly become equal to room temperature. Let us consider in detail which elements ensure this continuous process and how they interact with each other to maintain an ideal microclimate.
Main elements of a refrigeration system
The design of any compressor refrigerator is based on four main components that are interconnected by copper or aluminum tubes. Malfunction of any of them leads to a stop of the entire cooling cycle. The first and most important element is the compressor, which is often called a motor-compressor. It performs the function of a pump that forcibly distils the refrigerant through the system and increases its pressure.
The second key unit is the condenser, which is a coil, usually located on the back wall of the case or hidden in the side panels. Here the process of heat transfer occurs: the hot gaseous freon leaving the compressor cools down and turns into a liquid state. The third element is capillary tube or a throttle, which serves as the boundary between high and low pressure zones, sharply reducing the pressure of the refrigerant before it enters the evaporator.
The evaporator, located directly inside the refrigerator or freezer, completes the cycle. This is where the refrigerant boils at low pressure, resulting in a huge amount of heat being absorbed from the interior of the chamber. Modern models are also equipped with filter driers that remove moisture from the system, preventing the formation of ice jams.
⚠️ Attention: In older models, the condensers are often designed as a black mesh panel at the back. In new built-in refrigerators, they can be hidden inside the case, and heat is removed through the side walls, which can heat up to 50-60 degrees.
All these elements are connected hermetically, and any depressurization leads to freon leakage and cooling cessation. To control the process, you use thermostat or an electronic board that reads the temperature sensors and gives a command to turn the motor on or off.
Physics of the process: cycle of compression and expansion
The operating principle of the refrigerator is based on the fundamental laws of thermodynamics, in particular on the ability of substances to absorb heat during evaporation and give it away upon condensation. The cycle begins at the moment when thermostat records an increase in the temperature in the chamber above the set value and closes the electrical power supply circuit of the motor. The compressor begins to work, sucking vaporous refrigerant from the evaporator.
Gas is compressed inside the motor, which leads to a sharp increase in its temperature and pressure. Steam heated to 80-90 degrees under high pressure is pushed into the condenser. Passing along a long coil, the substance gives off heat to the surrounding air and gradually condenses, turning into a liquid. This process is accompanied by the release of energy, so the grille at the back of the refrigerator is always warm.
Next, the liquid freon passes through a narrow hole capillary tube. Here a sharp pressure drop occurs: the pressure drops, and the liquid partially boils, turning into a vapor-liquid mixture. This mixture enters the evaporator, where boiling continues intensively at low pressure. To transform into gas, the substance requires heat, which it takes from the food and air inside the chamber.
Why does freon not run out?
Freon in the refrigerator is not consumed like fuel in a car or water in the tap. This is a working fluid that circulates in a sealed circuit for years. It changes its state of aggregation, but does not disappear. Leakage occurs only when there is mechanical damage to the tubes or corrosion, which is a malfunction and not a normal operation.
After the evaporator, the gaseous but cold refrigerant returns to the compressor again, and the cycle repeats. This process continues until the temperature sensor detects that the required minimum has been reached. It is important to understand what cooling happens precisely at the moment the freon boils in the evaporator, and not in the compressor.
Types of compressors: from classics to inverters
The evolution of refrigeration technology has led to the emergence of different types of engines, each of which has its own operating characteristics, noise level and energy efficiency. The traditional solution is piston compressorworking on the principle of an internal combustion engine, but without ignition. Inside it, a piston compresses the gas in a reciprocating motion.
Such motors operate on the “start-stop” principle: they turn on at full power when the temperature rises, and turn off completely when the set level is reached. This creates a characteristic noise during startup and cyclic temperature fluctuations in the chamber. Despite this, they remain reliable and maintainable.
A more modern alternative is inverter compressors. They do not turn off completely, but only reduce engine speed to a minimum to maintain temperature. This allows you to avoid voltage surges during start-up, reduce noise levels and reduce wear of parts.
There are also linear compressors in which the piston is driven by electromagnetic forces without the use of a crank mechanism. This reduces the number of rubbing parts, making the unit quieter and more economical. The choice of motor type affects the final cost of equipment and energy costs.
☑️ Signs of proper operation of the compressor
The role of the thermostat and automation
Smart control of the refrigerator is impossible without a temperature control system. In mechanical models, this function is performed thermostat by a device with a bellows filled with gas or liquid that is sensitive to temperature changes. When the chamber becomes warmer, the gas expands, presses on the membrane and closes the contacts, starting the motor.
Modern electronically controlled models (No Frost, Multi Flow) use digital sensors - thermistors. They transmit accurate data to the control board, which makes decisions about turning on the compressor, starting the blowers or activating the defrost system. The accuracy of such sensors is higher, which allows you to maintain the temperature with an error of less than one degree.
Automation also controls the operating time of the motor. If the cooling cycle is prolonged, the board can force the compressor to stop to protect against overheating. In addition, there are protective relays that prevent the motor from starting immediately after turning off, waiting for the pressure in the system to equalize.
A malfunction of the thermostat often leads to the fact that the refrigerator either does not turn on at all or works without stopping, causing food to freeze. In such cases, diagnostics and replacement of the sensor or thermostat are required.
⚠️ Attention: If your refrigerator operates without interruption for more than 24 hours, this may indicate a freon leak, a broken thermostat, or a broken door seal. Operation in this mode will quickly damage the compressor.
Comparison of refrigerant characteristics
For decades, various substances have been used in refrigeration technology. Previously, R12 freon was popular, which turned out to be destructive to the ozone layer. Now it has been replaced by more environmentally friendly analogues, such as R600a (isobutane) and R134a. They have different physical properties, which requires adaptation of the refrigerator design.
For example, isobutane (R600a) is a flammable gas, but is used in microdoses (about 60 grams), which makes it safe. It has high cooling capacity and allows you to make the walls of the refrigerator thinner. Freon R134a is less efficient, but not flammable, so it is often used in car refrigerators and large equipment.
| Parameter | R600a (Isobutane) | R134a | R12 (Obsolete) |
|---|---|---|---|
| Influence on the environment | Minimum | Average | Destroys ozone |
| Flammability | Flammable | Not flammable | Non-flammable |
| System pressure | Low | Average | Low |
| Flow energy | Low | Average | High |
| Refilling cost | Higher | Average | Low |
Replacing one type of refrigerant with another is possible only with a complete reconfiguration of the system and changing the oil in the compressor, since they require different lubricants. Mineral oil does not mix with synthetic oil, which can lead to blockage of the capillary system.
Typical malfunctions and their causes
Understanding the structure of the refrigerator helps to quickly diagnose problems. One of the most common reasons for the lack of cold is freon leak. It can occur due to corrosion of the evaporator (especially in models with a weeping evaporator) or mechanical damage to the tubes due to inaccurate defrosting.
The second common problem is a clogged capillary tube. Over time, an ice plug may form in the system or oil oxidation products may accumulate, which blocks the circulation of the refrigerant. The compressor hums, but there is no cold, and the condenser remains cold.
Failure of the compressor itself is the most serious failure. Interturn short circuit of the windings or jamming of the piston group requires replacement of the motor. This is often not economically feasible for older models. There may also be problems with the starting relay, which simply cannot start a working engine.
To extend the life of the equipment, it is necessary to regularly clean the condenser from dust, check the tightness of the door and not overload the chamber with products that block air circulation.
Why does the refrigerator hum or knock loudly?
A loud hum often indicates that the compressor is working under increased load. This may be caused by improper installation (casing misalignment) when vibration is transmitted to the floor or walls. The engine itself can make a knocking sound when internal parts or valves wear out. Fans in the No Frost system can also be a source of noise if ice is frozen on their blades or they are unbalanced.
Is it possible to transport a refrigerator lying down?
Transporting a refrigerator in a horizontal position is not recommended, but is possible if strict rules are followed. Oil from the compressor may leak into the freon circulation circuit. If you nevertheless transported the equipment lying down, before turning it on, you need to let it stand upright for at least 4-6 hours (or better yet, a day) so that the oil flows back into the compressor crankcase.
How often should you defrost the refrigerator?
The frequency of defrosting depends on the cooling system. Models with technology No Frost (without frost) are equipped with an automatic defrosting system and require manual defrosting only for hygienic cleaning - 1-2 times a year. Refrigerators with a drip system (crying wall) defrost automatically in cycles, but it is recommended to completely defrost them for washing once every 6 months. Old models require defrosting as frost forms more than 5 mm thick.