Any owner of a modern refrigerator has at least once thought about how exactly a stable low temperature is maintained inside his equipment. The heart of the cooling system is evaporatorhidden from the user's eyes, but performs the critical job of removing heat. It is this element that is responsible for directly cooling the air inside the chambers, converting the refrigerant from a liquid into a gaseous state.
Understanding the operating principle of this unit allows you not only to operate the equipment more competently, but also to quickly diagnose serious faults before the products deteriorate. Unlike the compressor, which creates pressure, the evaporator is in direct contact with the internal environment, taking away thermal energy. Modern models of refrigerators they use complex designs of heat exchangers, the efficiency of which directly affects energy consumption.
If you notice that the equipment has started to work louder, a layer of ice has appeared on the walls or, conversely, food stopped freezing, the problem often lies precisely in the cooling circuit The boiling point of freon in the evaporator is about -30...-40 degrees Celsius, which allows you to effectively remove heat even with minimal energy consumption. In this article we will analyze in detail the device, functions and typical problems associated with this key element.
The physical principle of the heat exchanger
The main task of the evaporator is to intensively absorb heat from the internal volume of the refrigerator or freezer. This process is based on a fundamental physical law: during evaporation (transition from the liquid phase to the gaseous phase), any substance absorbs a significant amount of thermal energy. In the refrigeration circuit, the refrigerant, passing through the capillary tube and entering the expanded cavity of the evaporator, sharply changes its pressure and boils.
The boiling process of freon occurs at very low temperatures, the freezing point of water. When the liquid refrigerant passes through the channels of the heat exchanger, it “pulls” heat from the metal surface of the tubes and the plates attached to them. Heat transfer occurs continuously until the freon completely transforms into a gaseous state. That is why the surface of the evaporator is always cold, and sometimes even covered with frost during operation.
It is important to understand that the evaporator does not “produce cold”, it only transfers thermal energy from the inside to the outside. The compressor compresses the heated gas, sending it to the condenser (the radiator at the back of the refrigerator), where the heat is dissipated into the atmosphere. The cooled and liquefied freon then enters the evaporator again and the cycle repeats. Disruption of any link in this chain leads to the cooling process stopping.
⚠️ Attention: An attempt to defrost the refrigerator mechanically (chipping ice with a knife) often leads to damage to the evaporator tubes. A puncture of the tube causes an immediate release of all the freon and requires expensive professional repairs with soldering and refilling.
Design features and location
The location of the evaporator directly depends on the type of defrosting system installed in your refrigerator model. In older units and budget models with drip system (Direct Cool), the evaporator is often a foam circuit built directly into the side walls or rear panel of the refrigerator compartment. In the freezer compartment of such models, the heat exchanger may be visible as an open coil or plate behind a plastic panel.
More modern models with a system No Frost (no frost) use one powerful evaporator, which is usually located in a hidden compartment behind the back wall of the freezer. Unlike direct systems, here the fan forces air through the cold fins of the heat exchanger, distributing the cooled flow to all chambers through an air duct system. This allows you to avoid the formation of an ice coat on the products.
The material for production is most often aluminum or copper. Aluminum plates are lightweight and have good heat dissipation, but they are more sensitive to corrosion and mechanical damage. Copper tubes are more reliable, but are used less frequently due to their high cost. The design can be made in the form of a coil fused to a metal sheet, or in the form of a stacked block of corrugated plates.
Types of evaporators: Weeping wall versus No Frost
Differences in the design of evaporators determine not only the defrosting method, but also the microclimate inside the refrigerator. In weeping wall systems, the evaporator is hidden behind the rear panel of the refrigerator compartment. Periodically, the compressor turns off, the wall thaws, and moisture flows through the groove into the drainage hole. Here temperature conditions may be less stable, and the humidity is higher, which is good for vegetables, but bad for storing meat in open packaging.
The system No Frost uses an evaporator, which is constantly blown by a fan. This creates intense air exchange. The advantages of such a system are obvious: no need for manual defrosting and uniform temperature throughout the entire volume. However, there are also disadvantages: the air in such refrigerators is drier, which can lead to rapid weathering of food if containers are not used.
There are also combined systems where there is a “crying” evaporator in the refrigerator compartment, and No Frostin the freezer compartment. This is a compromise that allows you to maintain moisture for fresh food and keep your freezer free of ice. Understanding the type of your system helps to correctly set the thermostat and understand why condensation or ice appears on the back wall.
- 🧊 Direct Cool: The evaporator is located inside the chamber or foamed in the wall, defrosting is manual or automatic (drip).
- 💨 No Frost: The evaporator is hidden in a separate block, works in tandem with a fan, ice does not form due to cyclic heating Heating element.
- 🔄 Combined: Combines the advantages of both systems, but requires more complex maintenance and diagnostics.
Symptoms of malfunction of heat exchange equipment
Diagnosis of problems with the evaporator often begins with a visual inspection and analysis of the behavior of the refrigerator. If you notice that the unit hums continuously without turning off, but the temperature inside does not drop to the set values, this may indicate a freon leak or a clogged capillary tube. In such cases evaporator may be partially covered with frost only at the beginning of the circuit, and the rest of the circuit remains warm.
Excessive freezing with a “fur coat” or the formation of ice blocks in the freezer is a sure sign of a violation of the defrosting cycle. In No Frost systems, the defrosting system is responsible for this: heating element, thermostat and timer. If one of the elements fails, the evaporator becomes covered with ice, blocking the channels for air passage. As a result, the fan hums, but the cold does not enter the chamber.
Mechanical damage, such as swelling of the rear wall of the refrigerator, often indicates corrosion of the foamed evaporator. This is a common problem in certain manufacturers' models where the thin metal is exposed to moisture and chemical reactions. Visually, this manifests itself as rusty spots or bumps on the inner wall of the chamber.
☑️ Diagnosis of cooling problems
⚠️ Attention: If you hear a hissing sound after trying to break off the ice, immediately unplug the refrigerator and ventilate the room. The release of freon can be dangerous when concentrated, and contact of compressor oil with air while the engine is running can damage it.
The process of diagnostics and integrity testing
To accurately determine the condition of the evaporator, technicians use specialized equipment. The primary stage is visual troubleshooting. The back panel of the freezer is removed (in No Frost models), and the condition of the heat exchanger is assessed. A uniform layer of frost over the entire surface of the coil when the compressor is running indicates normal circulation of freon.
If traces of oil are visible on the tubes or connections, this is almost guaranteed to indicate a microcrack. The oil flows out along with the gas and remains at the damage site. To search for hidden leaks in a foamed circuit, the nitrogen pressure test method is used. The technician connects the pressure gauge station, pumps up the pressure and monitors the readings. A drop in the pressure gauge needle confirms a leak.
The patency of the capillary tube is also checked. If it is clogged with oil breakdown products or moisture, freon will not flow into the evaporator in the required volume. In this case, one part of the circuit will be cold and the other at room temperature. Diagnostics requires skill, as it is necessary to correctly interpret pressure and temperature readings at different points in the circuit.
| Symptom | Probable cause | Required actions |
|---|---|---|
| The evaporator is unevenly covered with ice | Freon leak or blockage | Call a technician to find the leak and refill |
| Ice coat in the freezer (No Frost) | Malfunction of the defrost system | Check Heating element, defrost sensor and timer |
| Bloating of the inner wall | Corrosion of the foamed circuit | Installation of an external evaporator (reweighing required) |
| The refrigerator does not freeze, the compressor hot | Complete loss of freon | Searching for breakdown, soldering, vacuuming and refilling |
Evaporator repair and replacement: what you need to know
Evaporator repair is a complex technological process that is almost impossible to perform efficiently in at home without special tools. If the exposed evaporator (plate in the freezer) is damaged, it can often be soldered with soft or hard solder. However, it is impossible to solder the damage site on the aluminum pipeline inside the polyurethane foam “coat” of the wall.
In case of corrosion of the foamed circuit, the only effective solution is installation external evaporator. The technician cuts off the back wall inside the chamber (or uses an existing hole), installs a new aluminum coil and secures it to the wall. The old circuit is cut off and silenced. This extends the life of the refrigerator for several years.
After any work related to opening the circuit, a procedure for vacuuming the system is mandatory. The remaining moisture inside will turn into ice during operation and clog the capillary, so using a vacuum pump is critical. It is also necessary to accurately calculate and charge the amount of refrigerant indicated on the factory tag.
Is it possible to drive with a faulty evaporator?
Operating a refrigerator with a freon leak leads to the compressor running idle. The engine overheats, the oil in it loses its properties, which can ultimately lead to a compressor wedge - the most expensive failure. It is better to turn off the equipment immediately.
Operating rules to extend service life
The durability of the evaporator and the entire refrigeration system depends on proper operation. Never place hot food inside the chamber. A sharp jump in temperature and humidity creates an extreme load on the heat exchanger and compressor, forcing the system to work at the limit of its ability to compensate for heat.
Regularly, at least once a year, completely defrost the refrigerator, even if you have a No Frost system. This is necessary to clean hidden drainage channels and check the condition of the seals. Dirt and mold in the drainage can cause stagnation of water, which will lead to corrosion of structural elements.
Monitor the temperature conditions. Setting the regulator to maximum cold unnecessarily causes the evaporator to operate in constant freezing mode, which reduces the life of the defrost system. The optimal temperature in the refrigerator compartment is +4...+5 degrees, in the freezer -18 degrees.
Why does the back wall of the refrigerator become covered with ice?
Icing of the back wall in refrigerators with a drip system is a normal operating process. Moisture condenses on the cold evaporator, freezes, and then, during the compressor shutdown cycle, melts and flows into the drain. If the ice does not melt and turns into a block, check the tightness of the door and the condition of the sealing rubber. Also, the cause may be a malfunction of the thermostat.
Is it possible to replace the evaporator yourself?
Theoretically, it is possible if you have the skills to solder copper and aluminum pipes, as well as access to a nitrogen cylinder, a vacuum pump and refrigerant. However, without experience, there is a high risk of making a mistake that will lead to the compressor burning out. Installing an external evaporator requires disassembling the case and sealing it, which is difficult to do efficiently at home.
How often do you need to defrost a refrigerator with an evaporator?
Refrigerators with the Direct Cool system (“crying wall”) require defrosting as ice accumulates, usually once every 3-6 months. No Frost systems do not require manual defrosting, but preventive disconnection from the network for a day once a year for hygiene and checking drainage will only benefit the equipment.
What to do if after defrosting the refrigerator does not freeze?
If after complete defrosting (24 hours) and turning on the refrigerator does not begin to cool, it is possible that a water lock has formed in the system (hydraulic blockage) or the compressor start relay has failed. Let the equipment run for several hours. If the cold does not appear, you need to call a technician for diagnostics.