Introduction to Compressor Cooling Methods

Oil Injection Cooling: The oil injection cooling method is used in small screw compressors as an improvement over the water-cooled or air-cooled methods employed by oil-free screw compressors, which can lead to uneven cooling. By injecting lubricating oil into the interior of the screw compressor, internal components can be cooled uniformly, preventing localized areas from being inadequately cooled. However, internal oil injection can cause carbon buildup due to the oxidation of the lubricating oil and the volatilization of its lighter components. As a result, synthetic compressor oils were researched and developed. Although synthetic compressor oils allow the compressor to operate at higher temperatures, the damage high temperatures can cause to the compressor prevents further increases in operating temperature. This is why every screw compressor is equipped with a temperature limit switch.

• Water-Cooled Cooling: This method uses a water circulation system to cool the compressor. Its advantages include excellent cooling performance, making it suitable for high-power applications and high-temperature environments. However, it requires a water circulation system, leading to higher maintenance costs. The aforementioned internal oil injection cooling is only applicable to medium and small-sized screw compressors. Since the cooling effect of internal oil is generally not as good as that of water, water cooling remains the primary method for large, high-pressure compressors. Some medium and small compressors also use water cooling, though with many structural improvements.

• Air-Cooled Cooling: This method blows air over the compressor's heat sink using a fan to dissipate heat. Its advantages are simple structure and easy maintenance. However, its performance is poor in high-temperature environments. Scroll compressors are mainly used in air-cooled chiller units but can also be found in water-cooled systems. Typically, a single compressor is insufficient to meet the cooling load, so multiple compressors are combined. From the perspective of cooling effectiveness, any lubricating oil can be used as a coolant.

However, since the lubricating oil cools within the compressor, it interacts with high temperatures, high pressures, air, and trace substances in the air, making the physical and chemical properties of the lubricating oil extremely important.