Magnetic levitation refrigeration unit

Magnetic levitation chiller

It is the use of magnetic force to make objects in a non-contact suspended state. The research on magnetic levitation technology first began with maglev trains. With the rapid development of modern control theory and electronic technology, magnetic levitation technology took a new step in the mid-1960s and shifted towards application direction, starting to study magnetic levitation bearings.

The system of magnetic levitation chiller technology consists of four parts: rotor, sensor, controller, and actuator. Assuming that the rotor is disturbed downwards at the equilibrium position, it will deviate from its reference position. At this time, the sensor detects the displacement of the rotor from the reference point. The microprocessor as the controller converts the detected displacement into a control signal, and then the power amplifier converts this control signal into a control current. The control current generates magnetic force in the executing magnet, thereby driving the rotor back to its original equilibrium position

Magnetic levitation chillers can be roughly divided into compression section, motor section, magnetic levitation bearings and controllers, and frequency conversion control section. The compression part consists of two-stage centrifugal impellers and inlet guide vanes. A supplementary air port is reserved in the middle of the two-stage impellers, which can achieve two-stage compression with supplementary air in the middle, as shown in Figure 2.

Characteristics of magnetic levitation chiller unit

1. The use of environmentally friendly refrigerant R134a has zero ozone depletion (ODP), no ban schedule is set in the new Montreal Protocol, and it belongs to positive pressure refrigerant. The external atmosphere is not easy to penetrate the system, the working pressure is low, the container safety is guaranteed, and there is no obvious toxicity or flammability.

2. Low operating noise

Under low operating noise and full load conditions, the noise level is as low as about 70dB, and under partial load conditions, the noise level is even lower, about 20dB lower than conventional units. The low operating noise makes the magnetic levitation compressor particularly suitable for the renovation projects of new and existing buildings such as hotels and hospitals that have strict noise requirements.

3. Oil free operation

1) The shaft of the magnetic levitation compressor is not in contact with the bearing.

2) Compared with traditional bearings, magnetic levitation bearings have no mechanical friction, only air flow friction, and the energy loss of air flow friction is only 2% of mechanical friction;

3) 90% of compressor burnout accidents are caused by lubricating oil failure, and magnetic levitation compressors have eliminated a large number of faults caused by oil return issues.

4) When lubricating oil is used, a layer of oil film will be formed on the surface of the heat exchanger, which will block the heat absorption and release of the heat exchanger, affecting the heat transfer efficiency of the heat exchanger.

4. Compact structure and small footprint

The advantage of high-speed magnetic levitation chillers is that the impeller diameter can be reduced to 5-8cm. The volume and weight of magnetic levitation compressors are only about 20% of conventional compressors with the same cooling capacity, saving floor space and making lifting more convenient;

5. Efficient operation and stable performance

The use of two-stage compression can increase the theoretical refrigeration coefficient by about 10% compared to one-stage compression. By using frequency conversion technology, the unit can operate at low speed under low load (usually the lowest partial load is 10%), avoiding the occurrence of surge while maintaining efficient operation.

6. Other advantages during actual operation

The starting of the magnetic levitation compressor is a soft start, with a starting current of only 0-6A, while the starting current of traditional compressors requires 200-600A. Moreover, in actual operation, the magnetic levitation modular chiller unit starts smoothly in multiple modules without any surge current. The first one starts smoothly before the next one starts, making the operation safer;

When there is a sudden power outage, the electricity in the capacitor of the compressor can ensure that the shaft speed slowly decreases until it reaches zero, avoiding damage to the compressor caused by sudden shutdown.

Application of magnetic levitation chiller unit

Based on the characteristics of low noise and high energy efficiency ratio under partial load, magnetic levitation chillers are particularly suitable for central air conditioning systems in hospitals, hotels, high-end office buildings, green, energy-saving and environmentally friendly buildings, etc. It can fully utilize the high-efficiency and energy-saving effects of partial load, greatly saving the operating costs of the entire air conditioning project. In addition, due to the high COP of magnetic levitation variable frequency centrifugal chillers at outlet temperatures ranging from 3-18 ° C, they can also be applied to air conditioning systems such as low-temperature air supply systems and independent fresh air systems.

Suspended chillers have outstanding advantages of high efficiency and energy conservation. Compared with ordinary centrifugal chillers, maglev centrifugal chillers can reduce energy consumption by about 40% throughout the year. The COP under nominal operating conditions can reach the national level 1 energy efficiency level of chillers, and its JPLV can reach 8.3-9. It is an energy-saving product worth promoting vigorously. At present, maglev technology is still a new type of technology, and there are few domestic manufacturers that have mastered and produced it, resulting in relatively expensive unit prices. With future development and cost reduction, magnetic levitation chillers have broad application prospects.