The question of why a refrigerator in a compressor is needed often confuses non-specialists, since in conventional household refrigeration cabinets there is no such unit in the classical sense. However, in the context of industrial equipment, namely screw compressors, this element is critically important. Refrigerator, or cooler, is a heat exchange device, without which normal operation of the screw pair is impossible. It is responsible for removing excess heat generated during gas compression.
If we consider screw compressor, we are dealing with a device where the temperature of the working environment can reach critical values. Without effective heat removal, the oil, which acts as a seal and lubricant, will quickly begin to degrade. This will lead to jammed rotors and costly production downtime. Therefore, understanding the role of the cooler is the basis for any engineer servicing such systems.
It is worth immediately noting that the term “refrigerator” is used here in the technical sense of a heat exchanger. It does not freeze the air to sub-zero temperatures, like a household appliance, but maintains the optimal thermal operating conditions of the oil and compressed gas. The main task is to prevent the oil temperature from exceeding 100-110°C in order to maintain its viscosity properties. Depending on the design, it can be an air radiator or a liquid heat exchanger.
The principle of operation of the cooling system in screw units
The operation of a screw compressor is based on the engagement of two rotors, between which air or gas moves. This process releases a colossal amount of thermal energy. To ensure that the system operates stably, oil is injected directly into the compression chamber. This oil gets hot and must be cooled before cycling again. This is where the oil cooler comes into play oil refrigerator.
Hot oil from the screw block is supplied to the heat exchanger. Depending on the type of design, heat is transferred either to the air flow, which is driven by a fan through the radiator fins, or to water circulating in a closed circuit. The cooled oil is returned to the system, where it is again mixed with the intake air, sealing the gaps and lubricating the bearings. Without this cycle Installation efficiency would have dropped to zero in a matter of minutes.
The efficiency of heat transfer directly affects the performance of the entire installation. If the refrigerator is clogged with dust or scale, the discharge temperature will begin to rise. The automatic control system, having received a signal from the sensors, can initiate an emergency stop. That is why regular checking of the cleanliness of heat transfer surfaces is a mandatory item of routine maintenance.
Types of heat exchangers: air and water
The choice of refrigerator type depends on the operating conditions and available resources at the enterprise. There are two main types of designs, each of which has its own characteristics. Air coolers they are radiators with aluminum or copper plates, blown by a powerful fan. They are easier to install, since they do not require a water supply, but are sensitive to dust in the air.
Water heat exchangers, or shell-and-tube devices, operate on the principle of heat transfer from oil to running water. Inside the housing there are tubes through which water flows, washed by oil from the outside (or vice versa). Such systems are more compact and efficient at high loads, but require constant monitoring of water quality and corrosion protection. In some models Plate heat exchangers can be easily disassembled for mechanical cleaning.
When choosing equipment, it is important to consider climatic conditions. For hot workshops, air cooling may not be effective enough, and then the only solution is a water circuit. It is also worth remembering about water consumption: modern systems often operate in a closed cycle using cooling towers, which saves resources.
The role of oil and temperature conditions
Oil in a screw compressor performs a triple function: lubrication, sealing and cooling. However, the oil itself needs protection from overheating. If the temperature in the circuit rises above the permissible level, the process of oxidation and coking begins. The resulting carbon deposits settle on the valves and in the refrigerator itself, reducing the efficiency of heat transfer.
The optimal operating temperature of the oil is in the range from 70 to 90 degrees Celsius. At temperatures below 70 degrees, moisture contained in the compressed air may condense in the oil, which leads to emulsification and loss of lubricating properties. Above 100 degrees, the oil begins to age quickly. Refrigerator maintains this balance, ensuring a stable viscosity of the liquid.
Violation of the temperature regime often causes failure of expensive components. For example, overheating can lead to deformation of the rotors or destruction of the bearings of the screw unit. Therefore, the cooling system is designed with a power reserve to cope with peak loads in the summer.
What happens when the oil overheats?
With prolonged overheating, the oil loses its anti-friction properties, varnish deposits form on the internal surfaces, which leads to jamming of the screw pair and emergency stop of the compressor.
Typical malfunctions and diagnostic methods
Operation of compressor equipment requires constant monitoring of parameters. Refrigerator problems often manifest as a sudden jump in discharge temperature. If the sensors show values close to emergency values, it is necessary to immediately check the condition of the heat exchanger. The most common cause is contamination of external surfaces with dust, lint or oil film.
Internal contamination is also possible, especially if low-quality oil is used in the system or the timing of its replacement is violated. In water refrigerators, the tubes are often overgrown with limescale (scale), which sharply reduces the heat transfer coefficient. For diagnostics, you can compare the temperature of the oil at the inlet and outlet of the refrigerator: if the temperature difference is too small when the fan is running, it means that heat transfer is impaired.
Other problems include mechanical damage to the radiator fins or leaks at the joints of the pipes. Vibration from a running compressor can weaken the fastening elements, which will lead to depressurization of the circuit. It is important to periodically conduct a visual inspection and, if necessary, tighten connections.
☑️ Diagnostics of the cooling system
Comparative table of characteristics of cooling systems
For a better understanding of the differences between types of refrigerators, it is advisable to consider their main parameters in comparison. This will help when choosing equipment or upgrading an existing line.
| Parameter | Air cooling | Water cooling | Combined |
|---|---|---|---|
| Efficiency heat transfer | Average | High | Maximum |
| Dependence on the environment | High (dust, temperature) | Low | Average |
| Service cost | Low | High (water, chemistry) | Average |
| Installation dimensions | Large | Compact | Medium |
| Installation complexity | Low | High (pipelines) | High |
As can be seen from the table, each type has its own advantages. Air systems are popular for their simplicity, but they may not cope well in hot or dusty climates. Water systems require water preparation, but ensure stable operation in any conditions. Engineering calculation helps to choose the best option for a particular production.
⚠️ Attention: When switching from air to water cooling (or vice versa), it is necessary to reconfigure the thermostatic valve and check the compatibility of seal materials with the new mode temperatures.
Maintenance and prevention of contamination
Regular maintenance is the key to a long life of the compressor. For air coolers, the main procedure is blowing with compressed air or washing with a special solution. This must be done carefully so as not to bend the soft aluminum radiator fins. The frequency of procedures depends on the dustiness of the room: in clean workshops once every six months is enough, in dirty workshops - monthly.
Water heat exchangers require chemical washing to remove scale and salt deposits. To do this, the circuit is turned off, the water is drained and an acid solution is circulated inside, dissolving deposits. After flushing, the system is thoroughly rinsed with neutral water. Ignoring this procedure can lead to local overheating and rupture of the heat exchanger tubes.
It is also important to monitor the condition of the fans. The blades must be clean and balanced. Fan vibration can be transmitted to the entire assembly, causing the fasteners to loosen. Fan bearings should be replaced at the first sign of noise or play.
The influence of external factors on the operation of the refrigerator
The environment plays a key role in efficiency of the cooling system. In summer, when the air temperature in the compressor room exceeds 35-40 degrees, the efficiency of the air cooler decreases. In such cases, it may be necessary to organize an additional supply of cold air or install exhaust ventilation.
In winter, the situation may be the opposite: the oil will cool down too quickly, which is also harmful for the compressor. To solve this problem, thermostats are used that redirect the oil flow bypassing the refrigerator until it warms up to operating temperature. Automatic The compressor strictly controls this process.
It is also important to take into account air humidity. In the cold season, when the compressor is operating at its maximum capacity, condensation may form inside the air ducts or on external elements if the operating conditions are not met. This can lead to corrosion of metal parts.
⚠️ Attention: Do not allow the compressor to operate at ambient temperatures below +5°C and above +40°C without special preparation of the room, this can lead to condensation of moisture in the oil or overheating.
Modern solutions and energy saving
Modern compressor stations are equipped with intelligent control systems that optimize the operation of the refrigerator. Fans can be frequency controlled, turning on only when really necessary. This reduces energy consumption and noise.
Heat recovery technologies are also being developed. The excess heat removed by the refrigerator does not have to be released into the atmosphere. It can be used to heat water in the heating system or hot water supply of an enterprise. This turns the “refrigerator” into a source of free energy, increasing the overall economic efficiency of the installation.
The use of new materials, such as composites or coatings with high thermal conductivity, makes heat exchangers more compact and durable. Engineers are constantly working to improve the geometry of the channels in order to reduce hydraulic resistance and increase the efficiency of heat transfer.
Is it possible to use water from a river for cooling?
The use of water from open reservoirs without preliminary filtration and water treatment is strictly prohibited, as this will lead to rapid fouling of the heat exchanger with biological organisms and silt.
What will happen if you completely turn off the refrigerator?
Completely turning off the refrigerator will lead to instant overheating of the oil. The temperature in the screw block will exceed 120°C in a few minutes, which will cause thermal destruction of the oil, jamming of the rotors and, most likely, will require major repairs or replacement of the screw pair.
How often do you need to change the oil in a water-cooled system?
The oil change schedule depends on the type of fluid used and operating conditions, but is usually 2000-4000 operating hours. However, with water cooling, it is important to ensure that water does not get into the oil, in which case replacement is required immediately.
Why does the oil temperature not rise above 60 degrees?
Too low an oil temperature (below 70°C) often indicates a malfunction of the thermostatic valve, which allows oil to bypass the radiator, or idling. Long-term operation at low temperatures is harmful due to the risk of moisture condensation.
Is it possible to wash an air radiator with water under pressure?
It is possible, but only using special detergents and low pressure so as not to bend the aluminum plates. After washing, the radiator must be thoroughly dried before starting the compressor to avoid short circuits in the fan motor.
Which type of refrigerator is quieter?
Water cooling systems are usually quieter, since they do not require a powerful large-diameter fan, which is the main source of noise in air models. However, water circulation pumps also create some background noise.