How do magnetic bearings work in a centrifugal compressor?

Magnetic bearings are playing an increasingly important role in the development of sophisticated and efficient compressors.

It could be argued that two key concerns for operators of compressors include enhancing their efficiency and reducing maintenance needs (and their ensuring costs). This is in part accompanied by a global effort to enhance efficiency with the ultimate goal of making equipment more sustainable, including environmentally-friendly district cooling initiatives.

As such, magnetic bearings in centrifugal compressors are providing a key answer, and an alternative to traditional equipment, which employed oil as a lubricant for the bearings, leading to some problems.

Such is the fact that, and as we’ll see below in this article, magnetic bearings for centrifugal compressors have been recommended by professional and regulatory bodies, such as  the U.S. Department of the Navy. After a case study, the organization was able to verify that oil free magnetic bearing compressors operate more efficiently, particularly during partial load conditions.

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What are magnetic bearings

Magnetic bearings are a type of bearing that uses magnetic forces to support and stabilize the rotation of a shaft or other moving parts without the need for physical contact.

In order to function, magnetic bearings consist of two main components: the rotor (the rotating part) and the stator (or stationary part). It’s the latter which contains electromagnets that generate magnetic fields, and the rotor typically includes permanent magnets or electromagnets. Through the combination of both, magnetic forces are able to maintain the desired position and stability of the rotor.

Magnetic bearings represent an alternative to traditional bearings, which rely on mechanical contact to support the load and reduce friction. Additionally, they use oil as a lubricant, which is often the cause for wear in the equipment.

In contrast, magnetic bearings operate without any physical contact between the rotating and stationary parts, resulting in several advantages, as we’ll see below. This working principle means magnetic bearings are oil free in their functioning.

A magnetic-bearing chiller compressor can be installed as part of a new chiller installation or a retrofit on an existing chiller. Additionally, it has been prescribed for chillers that, as a rule, run at partial loads. This is particularly important as an advancement for compression equipment in the 50-500 TR range (Conry et al., 2002).

The benefits of magnetic bearings in a centrifugal compressor

As we’ve mentioned above, the fact that magnetic bearings operate without any physical contact between the rotating and stationary parts results in several advantages:

-        Frictionless operation: the lack of physical contact between the moving parts means there is virtually no friction. This increases the heat transfer efficiency of the chiller, as no oil can enter the equipment; as well as reducing energy losses due to friction.

-        Low maintenance: the absence of mechanical contact and an oil free functioning also means there are no parts that can wear out. As a result, there are reduced maintenance requirements and a longer service life.

-        High-speed capability: magnetic bearings can support very high rotational speeds without the limitations imposed by friction.

-        Great precision and control: they offer excellent control over the position and orientation of the rotating element, making them suitable for certain applications that require precise positioning and stability.

-        Reduced noise and vibration: because of the absence of physical contact, noise and vibrational levels are minimized.

-        Light weight: magnetic bearings allow for faster installations due to their light weight

In fact, as part of their research, the U.S. Department of the Navy identified an average of 49% in power savings and 6.4 years average return on investment, unveiling how magnetic bearings can become a wise investment.


Chiller efficiency: the key for sustainable cooling

With the global climate crisis looming over, the development of increasingly efficient equipment stands out as a key achievement. This is precisely the context in which the importance of magnetic bearings and chiller efficiency can be understood.

As global concerns about climate change and energy consumption grow, improving the efficiency of cooling systems has become a priority in various sectors, including residential, commercial, and industrial applications.

As more and more cities embrace district energy, the development of efficient and sustainable compressors remains a crucial aspect. As such, this guarantees that sustainable cities will also be able to provide comfortable temperatures for citizens.

District cooling represents a centralized system that provides cooling to multiple buildings or areas from a single energy source. It is considered more sustainable compared to conventional individual heating and cooling systems for several reasons, their energy efficiency being one of the most important. As such, the heat pumps are a type of cooling technology that can also be used for heating. They operate by transferring heat from one location to another, and when used in cooling mode, they can achieve high levels of efficiency compared to traditional heating and cooling systems.

Compression chillers are the heart of these district cooling systems, as they are responsible for the cooling process. Their primary function is to produce chilled water, which then turns into the cooling medium used to cool the buildings in the network. The chiller achieves this by absorbing heat from the water, typically through an evaporator, using a refrigeration cycle.

It’s precisely in this aspect where chiller efficiency through the use of magnetic bearings remains particularly crucial. In other words, achieving chiller efficiency through magnetic bearings will have a direct impact on how efficient and sustainable district cooling systems can be.

Their advantages are also economic, as energy optimization also translates into less operational costs.

Additionally, as we’ve seen above, research has shown the magnetic bearings configuration to be particularly useful in partial load scenarios. This must be taken into consideration when designing district cooling systems, as compression chillers are in charge of efficiently handling varying cooling loads from different buildings in the district. In fact, their role in load management helps ensure that cooling resources are allocated optimally, minimizing waste and ensuring consistent cooling across the network.

When designing sustainable, optimized district cooling systems, efficiency must remain a top priority. This is also true of some additional aspects which relate to the installation’s environmental impact. This includes the use of sustainable refrigerants (moving away from those contributing to ozone depletion and global warming) and guaranteeing water savings, particularly in projects  where water scarcity can become an issue.

At ARANER, we’re at the forefront of developing sustainable district cooling systems that adjust to the particular needs of each project. As such, our focus has been on implementing significant enhancements in our equipment, including the use of magnetic bearings whenever they stand out as an adequate response.

Get in touch with us and learn how we can supercharge your project with sustainability and efficiency at the front.

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