Modern cutting-edge physics research, superconducting technology application, nuclear fusion energy development and quantum computing industry development are highly dependent on the ultra-low temperature environment near absolute zero. The lower temperature limit of conventional industrial refrigeration equipment and liquid nitrogen refrigeration system cannot meet the operation requirements of high-end scientific research and high-end equipment. Cryogenic helium refrigeration equipment is the core equipment to realize continuous and stable cryogenic refrigeration in industrial and scientific research fields. It can create an ultra-low temperature environment of 1.5K to 4.5K (-268.7℃ to-271.6℃), and is a key infrastructure to support the stable operation of superconducting equipment and the landing of cutting-edge low-temperature scientific experiments. This guide explains the working principle, major applications, temperature levels, key selection criteria and system configurations of cryogenic helium refrigerators.
A cryogenic helium refrigerator plant is an ultra-low-temperature refrigeration system designed to provide continuous cooling using helium as the working fluid. Depending on the system configuration, it may use a Claude-type refrigeration cycle, turbo-expansion technology, Joule-Thomson expansion and other cryogenic refrigeration processes.
The helium refrigeration equipment abandons the open cooling mode of traditional refrigeration equipment and adopts a closed cycle structure throughout the process. The helium in the system is compressed, heat exchanged, expanded and cooled for load refrigeration, and the helium after heat absorption and temperature rise will flow back and re-compress for infinite recycling.
Helium refrigeration equipment ensures long-term stability of low temperature environment and adapts to 24-hour uninterrupted operation requirements of large equipment. At the temperature coverage level, the helium refrigerator can realize cryogenic refrigeration from 2.0K to 4.5K, covering most superconducting and frontier cryogenic experimental requirements.
Among all conventional elements, helium has the lowest standard boiling point, which is approximately 4.2K at atmospheric pressure, Which is also the core reason why helium refrigeration system cannot be replaced by extremely low temperature scenario.
The lowest temperature of liquid nitrogen refrigeration system commonly used by Volkswagen can only reach 77K (-196℃), which is an order of magnitude different from the low temperature range of helium refrigeration. It can only meet the basic scenarios such as conventional industrial cryogenic cooling and biological sample storage, and cannot support the superconducting operation requirements.
Helium has unique superfluid physics, and ordinary liquid helium (He I) is converted to superfluid helium (He II) at temperatures below 2.17K (lambda point). the superfluid helium has no flow resistance and strong heat conduction performance, can quickly take away that local concentrate heat of the equipment, and avoids the problem of overheat due to temperature difference of the equipment.
However, the use of helium also introduces additional engineering requirements. Helium systems require high gas purity, effective leak prevention, efficient compression and expansion equipment, and carefully designed insulation and heat-exchange systems. These factors make helium refrigeration considerably more complex than liquid nitrogen cooling.
Cryogenic helium refrigeration unit relies on mature Claude cycle principle, combines multi-stage heat exchange and turbo expansion refrigeration technology, and operates in full automatic closed-loop operation with stable working conditions and excellent energy efficiency.
First, ambient helium is pressurized by an oil-injected screw compressor to a pressure of 10 to 20 bar or more. The heat generated in the compression process is quickly taken away by the water cooling system, and the oil and impurities in helium are completely removed by the coalescer and the absorber to ensure the purity of the working medium.
The high-pressure pure helium enters the multistage counter-current heat exchanger, and the low-temperature and low-pressure helium returned is used for precooling. Most industrial equipment will be equipped with liquid nitrogen precooling system to initially cool helium to about 80K, greatly improving the overall refrigeration efficiency and shortening the cooling time.
The precooled high-pressure helium gas is subjected to isentropic expansion through a low-temperature turbine expander, and the temperature of the precooled high-pressure helium gas is rapidly reduced while applying work to the outside. aft multi-stage expansion and temperature reduction, that final temperature reduction is completed by match with a Joule-Thomson valve to form low-temperature liquid helium or ultra-low-temperature helium.
The ultralow temperature helium medium is in direct contact with the load equipment and continuously absorbs the heat generated by the operation of the equipment. After heat absorption and temperature rise, helium will return to all stages of heat exchangers, recover cold energy and re-enter the compressor to complete the whole closed-loop cycle.
For the 2K superfluid low temperature scenario, the equipment will be equipped with a low pressure cryogenic compression system to reduce the ambient pressure above the liquid helium bath and break the upper limit of atmospheric temperature, thus achieving the superfluid helium refrigeration effect of 1.8K to 2.0K.
The whole set of helium refrigeration system has precise structure and high integration degree. The core components perform their respective duties to jointly ensure the long-term stable operation of the equipment. The core composition consists of six modules.
Helium compressor is the power core of helium refrigeration system, responsible for helium pressurization and circulation transportation, which is the basis of continuous operation of the whole equipment.
The core purpose of cryogenic helium refrigeration equipment is to provide continuous, stable and controllable closed-loop cryogenic cooling environment for various superconducting equipment and cryogenic scientific research systems. The major applications of helium refrigeration include superconducting magnets, particle accelerators, fusion research, low-temperature physics, scientific research.
Superconducting magnet is the core component of high-end medical, industrial detection and scientific research equipment. Its superconducting characteristics can only be maintained in extremely low temperature environment. Once the temperature exceeds the standard, it will lose its zero resistance characteristics and cannot work normally.
Cryogenic helium refrigeration equipment can continuously cool superconducting magnet coils through stable liquid helium bath environment, accurately maintain the low temperature conditions required by the equipment, and ensure stable operation of magnets with zero resistance and high magnetic field strength.
Cryogenic helium refrigeration equipment is applied to medical nuclear magnetic resonance equipment, industrial superconducting detection equipment, laboratory high-field superconducting magnet, nuclear magnetic resonance spectrometer and other equipment, which is the most mature commercial application scene at present.
Particle accelerator is a big power for high-energy physics research. The superconducting RF cavity and beam-oriented superconducting magnet inside the equipment have extremely high requirements for low temperature stability and temperature uniformity, which is the core high-end application scenario of helium refrigeration equipment.
Superconducting RF cavity can greatly improve the quality factor (Q value), reduce the dynamic loss, and achieve high gradient, continuous and stable particle acceleration effect in ultra-low temperature environment. Superfluid helium has excellent thermal conductivity, which can quickly take away the heat generated by high frequency operation of the cavity and avoid overheating failure of the equipment.
Many top accelerator projects in the world adopt 2K superfluid helium refrigeration scheme, including LHC accelerator of European Nuclear Center, LCLS-II accelerator of SLAC National Accelerator of the United States, FRIB heavy ion accelerator and other large facilities of kilometer level, all of which rely on large helium refrigeration equipment to realize all-weather stable operation.
Nuclear fusion equipments rely on high-temperature plasma to release energy, but superconducting magnet systems that constrain plasma need extremely low temperature environment to maintain operation, forming a special working condition of “extremely cold and extremely hot”.
Tokamak nuclear fusion equipments (ITER, KSTAR, JT-60SA, etc.) are equipped with large helium refrigeration systems for cooling superconducting confinement magnets, equipment cryogenic insulation shields and vacuum cryopumps.
Nuclear fusion equipment has pulsed heat load fluctuations, which conventional cryogenic refrigeration equipment cannot adapt to. However, industrial-grade helium refrigeration equipments can adapt to pulsed heat changes and maintain low-temperature stability under complex working conditions. They are important core equipment for nuclear fusion energy research.
The research of superconducting qubits and quantum materials needs an extremely low temperature environment close to absolute zero. The mainstream dilution refrigerator can achieve million-level low temperature, but it still needs helium refrigeration equipment to provide pre-cooling support.
Cryogenic helium refrigeration equipment can stably provide 4K precooling environment, share basic cooling load for dilution refrigerator, and provide continuous liquid helium supply for quantum cryostat equipment, and build stable quantum experiment cryogenic platform.
The equipment is widely used in frontier fields such as superconducting quantum chip testing, quantum material low-temperature characteristic research, low-dimensional physics experiment, etc. It is the basic supporting equipment for quantum science and technology industrialization and scientific research exploration.
The research of cryogenic physics in universities and national key laboratories cannot be separated from the continuous cooling of helium refrigeration equipment, which can replace the traditional manual liquid helium supplement mode and realize long-term unattended continuous refrigeration.
The equipment is widely adapted to various cryogenic scientific research scenarios such as condensed matter physics experiments, cryogenic detector cooling, cold neutron source equipment, spectral analysis experiments, etc., providing a stable cryogenic environment for basic physics research.
Many national scientific research platforms will deploy large-scale shared helium refrigeration systems to provide cryogenic support for multiple laboratories and multiple groups of experimental equipment, greatly reducing scientific research costs and improving experimental stability.
The choice between a 4.5 K helium refrigerator and a 2 K helium refrigerator depends primarily on the required operating temperature, heat load and application.
The temperature range of 4.5K refrigeration system is stable from 4.2K to 4.5K, and the working fluid is ordinary liquid helium (He I). 4.5K helium refrigeration system is used for scientific research superconducting magnets, low frequency superconducting RF cavities, general cryogenic physics experiments and cost sensitive scientific research projects. It is the first choice for small and medium-sized laboratories and conventional superconducting applications.
The operating temperature of 2K superfluid refrigeration system is controlled from 1.8K to 2.1K, which is lower than the lambda phase transition point of liquid helium. The working medium is superfluid helium (He II). The operation is in negative pressure environment. It needs to be equipped with cryogenic compressor unit and special cryogenic cold box. However, 2K helium refrigerator has higher energy consumption than 4.5K helium refrigerator, more complex equipment structure, strict requirements for air tightness and helium purity, and much higher initial investment and later operation and maintenance costs than 4.5K equipment.
2K helium refrigerator is used in large particle accelerator, nuclear fusion superconducting magnet, high gradient superconducting radio frequency cavity, high precision quantum experiment and other scenes requiring extreme low temperature stability and heat dissipation efficiency.
| Feature | 4.5 K Helium Refrigerator | 2 K Helium Refrigerator |
| Typical temperature | ~4.5 K | ~1.8–2.1 K |
| Helium state | Gas / supercritical helium / liquid helium depending on system | Superfluid helium region |
| Typical applications | Superconducting magnets, research systems | SRF cavities, advanced accelerators |
| System complexity | Lower | Higher |
| Low-pressure pumping | Generally not required | Typically required |
| Heat-transfer capability | High | Extremely high |
| Energy consumption | Lower | Higher |
| Capital cost | Lower | Higher |
Cryogenic helium refrigeration equipment belongs to highly customized industrial equipment, and there is no general standard helium refrigerator. The selection needs to be comprehensively considered in combination with its own working conditions, refrigeration demand and long-term operation and maintenance cost. The core selection steps are divided into six dimensions.
Specify the target refrigeration temperature (4.5K/2K overpressure), the required refrigeration power, distinguish between static basic heat load and dynamic pulse heat load of equipment operation, reserve 15% to 50% safety redundancy, and avoid insufficient cooling capacity of equipment.
Evaluate thermodynamic energy efficiency of equipment, focusing on equipment quality factor (FOM) and input-output efficiency ratio. Optimize energy consumption and cooling rate of helium refrigeration system.
Check equipment reliability and operation convenience. Large-scale scientific research facilities usually require equipment availability of more than 95%. Priority shall be given to equipment equipped with redundant compressor, standby liquid helium energy storage and full-automatic purification system, so as to reduce shutdown failure and reduce operation and maintenance difficulty.
Evaluate the integration of helium refrigeration system in combination with site conditions, comprehensively consider equipment floor space, hydropower supporting facilities, cryogenic pipeline layout, helium reserves, remote automatic control capability, and take into account site safety and equipment upgrading and expansion space in the later period.
Balance life-cycle costs, distinguishing between initial helium refrigeration plant investment and long-term operating costs.
Choose a professional helium refrigerator customized solution. In combination with the project application scenario, operating conditions and long-term requirements, customized standardized or personalized equipment solutions are customized, and the installation, commissioning and post-operation and maintenance guarantee are completed by relying on the technical team of the helium refrigerator manufacturer.
Fullcryo is deeply engaged in the field of cryogenic helium refrigeration, focusing not only on the R & D and manufacturing of single helium refrigeration equipment, but also on the implementation of full-process and integrated ultra-low temperature refrigeration solutions. For ultra-low temperature application scenarios such as superconductivity, high-energy physics, nuclear fusion, quantum scientific research, etc., the standard temperature is only the foundation, and the cooperative stability, working condition adaptability and long-term operation efficiency of the whole system are the core keys to determine the success or failure of the project. We can customize 20K, 4.5K and 2K multi-stage temperature zone refrigeration systems on demand, combining the actual refrigeration capacity, heat load, helium flow rate, field conditions and future expansion requirements of the project to create exclusive customized solutions.
The standard industrial helium refrigerator can stably achieve low temperatures of 4.2K to 4.5K. The upgraded helium refrigerator equipped with low pressure cryogenic compression system can stably operate in the superfluid temperature range of 1.8K to 2.0K. The lowest temperature of optimized helium refrigerator can reach 1.5K. Extremely low temperatures below 1K in the milliKelvin range need to be achieved with dilution refrigeration equipment and cannot be achieved by conventional helium refrigeration equipments.
The lowest temperature of liquid nitrogen refrigeration is 77K, which is low in cost and convenient to obtain materials. It is only suitable for conventional cryogenic cooling, sample storage and equipment precooling, but cannot support superconducting operation. Liquid helium refrigeration can realize extremely low temperature from 2K to 4.5K, which is the core cold source for superconducting, quantum and high energy physics research. However, the cost is higher, the equipment is more precise, and the application scenarios of the two do not overlap at all.
Not the same device, core functions are significantly different. Helium liquefier is used for batch production of liquid helium, static storage, belongs to the intermittent cooling equipment, can not continue to load heat dissipation. Helium refrigeration unit adopts closed-loop cycle design, mainly focuses on continuous dynamic heat dissipation and refrigeration, and is compatible with liquefaction function, so it is the first choice for continuous operation of large equipment.
For high-end scenarios such as particle accelerators, nuclear fusion and high-precision quantum experiments, the equipment performance improvement and stability optimization brought about by 2K super-flow refrigeration can completely cover the additional energy consumption and equipment cost, and has extremely high application value. However, in conventional superconducting and ordinary low-temperature scientific research scenarios, 4.5K equipment has higher cost performance, and there is no need to blindly upgrade the 2K system.
Cryogenic helium refrigeration device is the core infrastructure for human beings to march into the field of near absolute zero low temperature, break through superconducting technology and cutting-edge physics research, and is an indispensable supporting system for many high-end scientific research equipment. For projects requiring customized ultra-low-temperature refrigeration, Fullcryo provides integrated helium refrigeration and liquefaction solutions covering 20 K, 4.5 K, 2 K and specialized low-temperature applications, with system configurations tailored to the specific project requirements.
