Magnetic‑Bearing Air‑Cooled Chiller (Air‑Cooled Magnetic‑Bearing Variable‑Frequency Centrifugal Chiller)
1. Definition
The magnetic‑bearing air‑cooled chiller is an oil‑free variable‑speed centrifugal chiller. Its core is a high‑speed permanent‑magnet variable‑frequency centrifugal compressor equipped with magnetic‑bearing electromagnetic bearings. The rotor is suspended by electromagnetic force to achieve zero physical mechanical friction, and the whole unit eliminates the lubricating oil system. It adopts fin‑type air‑cooled condenser with axial fans to dissipate heat directly to ambient air. No cooling tower or cooling‑water system is required. The complete unit is an outdoor monoblock assembly, which can be installed on rooftops or ground. Only chilled‑water piping and power supply connection are needed for commissioning.
Principle of magnetic‑bearing: Consists of electromagnetic coils, high‑precision displacement sensors and closed‑loop controller. Coil current is dynamically adjusted in millisecond intervals to maintain rotor suspension. Upon power failure, the rotor lands on protective bearings to avoid impact damage.Optional configuration: Some models are integrated with free‑cooling modules. Under low‑ambient‑temperature conditions, the compressor can be shut down, and outdoor air is utilized to cool chilled water directly for further energy saving, widely applied in IDC data centers.
2. System Composition
Magnetic‑bearing oil‑free centrifugal compressor: Permanent‑magnet high‑speed variable‑frequency motor with active electromagnetic suspension bearing; stepless cooling‑capacity regulation from 10%‑100%; oil‑free design.
Fin‑and‑tube air‑cooled condenser: Axial fans enforce convective heat rejection to discharge refrigerant condensation heat directly to outdoor air.
Shell‑and‑tube evaporator: Produces conventional 7 °C air‑conditioning chilled water.
Electronic expansion valve, PLC touch‑screen control system; complete protection functions including high/low pressure, water‑flow interlock, freeze protection, anti‑surge and bearing protection.
Peripheral auxiliaries: chilled‑water pump, expansion tank, water‑treatment device; cooling‑water pump and cooling tower are not required.
3. Key Performance Parameters
(National‑standard air‑cooled rated condition: ambient dry‑bulb 35 °C, chilled‑water 7 °C /12 °C)‑ Unit cooling capacity: 230 kW‑2000 kW (65‑570 RT)‑ Full‑load COP: 3.4‑4.2‑ Integrated Part‑Load Value (IPLV): 7.5‑9.5 (much higher than air‑cooled screw and air‑cooled scroll chillers)‑ Extremely low starting current with soft‑start feature, minor impact on transformers‑ Noise level: 68‑74 dB(A), low vibration‑ Main refrigerants: R134a, R513A low‑GWP eco‑friendly refrigerants‑ Water‑supply limitation: Stable outlet water temperature ≥5 °C; cannot produce ‑5 °C ~‑25 °C glycol low‑temperature process cooling water‑ Operating ambient range: ‑10 °C ~ 43 °C; obvious cooling‑capacity degradation above 38 °C; antifreeze kit required for low‑temperature environment.
4. Core Advantages
Oil‑free system with low maintenance costRefrigeration oil, oil separator and oil filter are completely eliminated. No oil‑film fouling occurs on heat‑exchanger surfaces to sustain long‑term heat‑transfer efficiency. No oil‑related maintenance is needed. Annual work mainly includes fin cleaning and electrical inspection, with far‑lower maintenance workload compared with air‑cooled screw chillers.
Simple installation without cooling‑water systemNo machine room or cooling tower is required; zero cooling‑water consumption and eliminates legionella risk from cooling towers. Suitable for water‑scarce regions and renovation projects where cooling‑tower installation is prohibited by property management, reducing civil‑engineering auxiliary investment.
Excellent part‑load performanceThe magnetic‑bearing compressor maintains high efficiency even at 10% partial load. Since buildings operate under part‑load conditions most of the time, its annual comprehensive energy efficiency is significantly superior to air‑cooled screw and air‑cooled scroll chillers.
Low vibration, monoblock integrated structure; multiple units can be paralleled for mutual redundancy. Free‑cooling module is optional to effectively reduce PUE for data centers.
5. Inherent Drawbacks & Selection Constraints
Obvious performance degradation under high‑ambient‑temperature conditions: Above 38 °C ambient temperature, condensing pressure rises, cooling capacity drops and unit power consumption increases. Its full‑load performance in hot‑summer regions is inferior to water‑cooled magnetic‑bearing chillers.
Incapable of low‑temperature glycol process cooling; only applicable for conventional air‑conditioning and constant‑temperature chilled‑water above 5 °C; not suitable for chemical low‑temperature‑process applications.
High procurement cost, higher than air‑cooled air‑bearing chillers and far higher than air‑cooled screw chillers. Suitable for projects with long annual operating hours; not recommended for intermittent‑operation projects due to long payback period.
Sophisticated magnetic‑bearing electronic‑control system, sensitive to power‑supply‑voltage fluctuation and harmonic distortion; on‑site repair relies on original‑manufacturer technical support.
Outdoor exposed installation leads to easy dust and catkin accumulation on fins, requiring regular washing. Antifreeze glycol or complete water‑circuit draining is mandatory in winter. Large footprint requires sufficient rooftop load‑bearing capacity.
6. Application Scenarios
✅ Recommended Applications
Large‑scale commercial projects where cooling‑tower and dedicated refrigeration‑machine‑room installation are unavailable: office buildings, hospitals, museums, hotel‑complex renovation projects.
Central air‑conditioning systems in water‑scarce and water‑resource‑stressed regions.
IDC data centers and computing‑power rooms (prefer versions equipped with free‑cooling modules).
Clean‑workshop projects demanding high refrigerant‑system cleanliness without cooling‑water‑system configuration.
❌ Not‑Recommended Applications
Chemical and low‑temperature‑process applications requiring low‑temperature glycol chilled‑water.
Projects with long‑duration extreme‑high‑temperature summer conditions and continuous full‑load operation requirements.
Small‑and‑medium‑size projects with low annual operating hours and frequent start‑stop cycles.
7. Horizontal Comparison Table
| Comparison Item | Magnetic‑Bearing Air‑Cooled Chiller | Air‑Cooled Air‑Bearing Chiller | Air‑Cooled Screw Chiller | Water‑Cooled Magnetic‑Bearing Chiller |
|---|
| Suspension / Bearing | Active electromagnetic suspension, closed‑loop electronic control | Dynamic‑pressure air‑film bearing, purely mechanical | Mechanical sliding bearing with lubricating‑oil system | Active electromagnetic suspension, closed‑loop electronic control |
| IPLV | 7.5‑9.5 | 7.0‑8.8 | 4.5‑6.0 | 10.0‑12.1 |
| Performance @ 38 °C high‑temperature condition | Severe cooling‑capacity degradation | Severe cooling‑capacity degradation | Noticeable degradation | Stable performance with negligible degradation |
| Cooling water / cooling tower | ❌ Not required | ❌ Not required | ❌ Not required | ✅ Mandatory |
| Oil‑system maintenance | Oil‑free, no oil‑related maintenance | Oil‑free, no oil‑related maintenance | Annual refrigeration‑oil & oil‑filter replacement | Oil‑free, no oil‑related maintenance |
| Low‑temperature glycol duty | ❌ Not available | ❌ Not available | ✅ Available | ❌ Not available |
| Power‑grid adaptability | Poor, vulnerable to voltage fluctuation | Strong, good anti‑disturbance capability | General | Poor, vulnerable to voltage fluctuation |
| Procurement cost | Very high | High | Medium | Highest |
8. Maintenance Guidelines
Wash air‑cooled fins annually to remove dust and catkins and prevent high‑pressure alarms.
Inspect power‑supply stability for magnetic‑bearing controller and frequency converter; voltage stabilizer is recommended for unstable power supply.
Add industrial antifreeze glycol or fully drain water circuit for winter freeze‑protection.
Regular inspection of fans and electrical connections; no oil‑system maintenance required.
Selection Rule
Choose magnetic‑bearing air‑cooled chiller for projects without cooling‑tower feasibility, in water‑scarce areas, with long‑duration annual operation and sufficient budget.Select air‑cooled air‑bearing chiller for better power‑grid anti‑interference performance under identical conditions.Prioritize water‑cooled units for scenarios of long‑term high‑temperature full‑load operation in summer.Select air‑cooled screw chiller if low‑temperature process cooling is demanded.
Precautions for Unit Use
Installation precautions
1. When lifting, positioning, and installing the unit, safety must be taken into account to prevent collisions and ensure the integrity of the equipment.
2.If the unit is installed outdoors, efforts should be made to avoid exposure to wind and rain (except for rainproof types), direct sunlight, or other heat sources that directly radiate; The computer room environment must be kept dry, clean, and ensure good ventilation, leaving space for unit maintenance and upkeep.
3. For air-cooled units, please ensure that there are no obstructions around the unit and reserve 1 meter of space; There is no obstruction within 2 meters of the top of the unit to ensure good ventilation.
4. It is recommended to install the unit on a strong and level ground, and install shock-absorbing rubber pads under the unit chassis to correct the level of the unit. If there are anchor bolts, they must be installed and fixed.
5. The circulating water pump used in conjunction with the unit should be selected and installed according to the data requirements such as water flow rate and water resistance required by the unit.
6. The water pump must be installed in front of the inlet of the unit, and it is recommended to install a filter at the inlet of the water pump to prevent foreign objects from entering the heat exchanger of the unit; If the unit is installed in areas with poor water quality, water treatment must be carried out first to avoid damage to the heat exchanger.
7. It is recommended to install valves, water pressure gauges, thermometers, water flow switches, and other equipment for the water pipeline system connecting the unit, in order to facilitate the inspection and maintenance of the unit's daily operation.
8.To prevent air from being trapped in the water system, the air must be completely discharged before starting the compressor.
9. The chilled water pipeline must be insulated properly to avoid loss of cooling capacity, condensation, and freezing.
10. The weight of the system connection pipeline shall not be borne by the machine body. Rubber shock-absorbing flexible joints and gate valves shall be installed at the inlet and outlet of the unit to avoid vibration and facilitate maintenance.
11.When configuring wires for the unit, wires with slightly larger cross-sections (with margin) should be selected according to the power consumption, and reliable electronic control components and grounding power sources should be installed to prevent accidents such as overload and leakage.
12. As the unit is equipped with reverse phase and phase loss protection, attention must be paid to whether the line phase is correct during wiring installation. The unit cannot operate normally when the phase is misconnected or missing.
13. The operator of the unit must observe the operation status of the unit at all times. Once any abnormal situation is found, please promptly troubleshoot. Forced operation will inevitably cause damage to the unit.
Precautions for operation:
1. Before starting up, check whether all water outlets and pipelines of the unit have been correctly installed and connected.
2. Before starting up, check if the power supply of the unit is connected and if the phase sequence is correct.
3. Before starting up, ensure the safety of the power and water sources. Please carefully refer to the equipment operation manual and strictly follow the instructions for use and operation.
Maintenance precautions:
1. Regularly replace the water in the water tank (it is recommended to replace it every 2 months).
2. Regularly clean the radiator of the unit. For air-cooled units, it is recommended to clean the radiator every 3 months; It is recommended to clean the shell and tube condenser and cooling tower of water-cooled units every 6 months (if the usage environment or water quality is poor, it is recommended to shorten the cleaning cycle).
3.If the unit is not used for a long time, please turn off the main power supply; When the ambient temperature is below 0 ℃ and the unit is shut down for more than 6 hours, the unit and pipelines may freeze, and the damage caused by this is not covered by the warranty.
The best way to avoid pipeline freezing is to completely drain all the water in the unit system!
4. Regularly check the water quality on site to ensure that the water source is qualified (pH ≈ 7). If it contains corrosive substances and causes damage to the unit, it is not covered by the warranty.
5.When the unit encounters unavoidable faults during use, please inform our company of the unit model, component name, and other information so that we can provide you with services more quickly.
6.During the warranty period, our company promises to provide free maintenance services for the unit (excluding human damage, improper use, natural disasters, and uncontrollable factors).
Warning: This unit is a high-voltage, highly specialized mechanical equipment, and should be operated correctly by professional technicians strictly in accordance with the "User and Installation Manual".
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