In high-tech industries such as quantum computing, controlled fusion and superconducting devices, cryogenic refrigeration technology is the core prerequisite to ensure stable operation and break through technological bottlenecks.Helium Refrigerator is the core equipment in the cryogenic field. In this article, we will analyze the Helium Refrigerator.
With the rapid iteration of the high-tech industry, the requirements for refrigeration temperature, stability and efficiency continue to rise, ordinary refrigeration equipment can no longer meet the demand for liquid helium temperature zone (-269 ° C or so) and the following cryogenic needs. The helium refrigerator is a professional cryogenic equipment that utilizes the characteristics of helium to achieve ultra-low temperature refrigeration.
With a boiling point of only 4.2K (-268.93°C) at atmospheric pressure, helium is the most difficult of all gases to liquefy, making it easy to achieve ultra-low-temperature environments in the liquid helium temperature range and below, providing the extreme low-temperature conditions needed for superconductivity, quantum computing and other fields.
The basic principle of Helium Refrigeration is “heat absorption and cooling” through a refrigeration cycle. The mainstream cycle is based on the Joule-Thomson effect and the Brayton cycle.
Joule-Thomson effect: This means that when a gas expands freely in an isenthalpic environment, the temperature will rise and fall (depending on the initial temperature of the gas). For helium, the expansion process is accompanied by a significant decrease in temperature at temperatures below the inversion temperature, which is the core effect of Helium refrigerator to achieve ultra-low temperatures and the core principle of the Linde-Hampson cycle.
Brayton Cycle: Mainly used in large helium refrigeration equipment, through the cycle of “compression → cooling → expansion → heat absorption”, utilizing a turbine expander to allow the helium to do work on the outside world, further lowering the temperature.
A complete helium refrigeration system consists of a number of core components that work together, including the following five categories:
The compressor is the “powerhouse” of a helium refrigeration system. Its core function is to compress the gaseous helium to high pressures (typically tens of megapascals) and to remove the heat generated by the compression process from the system. Helium compressors include oil-injected screw compressors and centrifugal cold compressors for different refrigeration capacity requirements.
The heat exchanger is a key component in the “cooling pre-treatment” process. Its core function is to exchange heat between the high pressure, high temperature helium output from the compressor and the low temperature helium returning from the expansion end. In large helium refrigeration plants, the heat exchanger is often of the plate-fin design, which is characterized by ultra-low leakage rates and high heat exchange.
Expansion valves or turboexpanders are the core components of helium refrigerators to realize “ultra-low temperatures”. They are responsible for expanding and depressurizing the high pressure, pre-cooled helium gas to achieve a sudden drop in temperature by using the Joule-Thomson effect or by doing work on the outside.
Expansion Valve: A relatively simple structure, suitable for small helium coolers, where the helium is rapidly expanded through a narrow valve channel, the temperature is instantly lowered, and some of the helium is liquefied.
Turboexpander: Suitable for large, high power helium refrigeration equipment, through the high-speed rotation of the turbine helium external work, the temperature drops dramatically, the refrigeration efficiency is higher, some of the turbine expander speed up to 100,000 – 150,000 revolutions per minute, is one of the core components of large helium refrigeration systems.
Liquid helium tanks (also known as liquid helium dewars) are used to store the liquid helium produced after expansion and cooling, while maintaining the liquid helium at a low temperature to prevent it from evaporating. Liquid Helium Dewars reduce the evaporation rate of liquid helium and Fullcryo ensures that the liquid helium is stored safely and that a constant supply of liquid helium is available for downstream equipment.
The control and monitoring system is the “brain” of the helium refrigeration system and is responsible for the real time monitoring of the entire system, including helium pressure, temperature, flow rate, liquid helium level, and the operating status of all components. Fullcryo’s cryogenic systems are remotely controlled for 24-hour real-time monitoring and commissioning by operators.
The Helium Refrigerator works in a closed loop cycle, from helium gas compression to liquid helium supply and recycling, each step is interlocked to ensure a constant cryogenic output, which can be divided into the following 5 steps:
First, the gaseous helium is drawn into the compressor, which compresses it to a high pressure (typically 10-30 MPa) through mechanical work. During the compression process, the molecular kinetic energy of the helium increases and the temperature rises (up to 100°C or more).
The high pressure, high temperature helium is fed into the heat exchanger, where it is fully exchanged with the low temperature helium returning from the expansion end.
The returning low-temperature helium (at a temperature close to that of liquid helium) absorbs heat from the high-pressure helium, gradually increases its own temperature, and is returned to the compressor for recompression. The high pressure helium, on the other hand, releases heat and gradually lowers its temperature to near room temperature (typically 0-10°C), completing the pre-cooling process.
After pre-cooling, the high pressure helium gas is fed into an expansion valve or a turbine expander to start the expansion and depressurization process, which is the core step in achieving ultra-low temperatures.
If an expansion valve is used, the helium will expand rapidly through a narrow channel, the pressure will drop suddenly, and the temperature will instantly drop to about 4.2K (-268.93℃) by using the Joule-Thomson effect, and part of the helium will be liquefied directly; if a Turbine Expander is used, the helium will push the turbine to rotate at a high speed to do external work, and the temperature will be lowered further, and the temperature can reach the super-fluid helium temperature zone of 2K (-271℃) to meet the needs of higher-precision cryogenic temperatures. This can even reach 2K (-271℃) super fluid helium temperature zone, which can meet the demand of higher precision cryogenic temperature.
The liquid helium produced after expansion and cooling is introduced into a liquid helium storage tank. The tanks are vacuum insulated to minimize heat transfer from the outside world and to reduce evaporation losses of the liquid helium.
The gaseous helium from the evaporation of the liquid helium, as well as the low temperature gaseous helium returning from the expansion end, re-enter the heat exchanger and exchange heat with the high pressure helium, warming it up and drawing it into the compressor again, completing the refrigeration cycle.
With their ultra-low temperature refrigeration capability and high stability, helium refrigerators are widely used in high-tech fields and have become the core equipment to promote the development of cutting-edge technologies:
In particle gas pedals, superconducting magnets need to be operated in the liquid helium temperature region (4.2K) in order to realize the characteristics of strong magnetic field and low loss, and to ensure the acceleration and deflection precision of the particle beam. Helium refrigeratorprovide a continuous and stable low temperature environment for superconducting magnets, which is the core guarantee for the normal operation of particle gas pedals.
The 400 W @ 4.5 K helium refrigerator developed by Fullcryo serves the Beijing Superconducting Linear Accelerator Nuclear Physics Facility, which helps to realize the construction of heavy ion irradiation conditions and key technology research.
The core component of magnetic resonance imaging (MRI) equipment in the medical field and nuclear magnetic resonance (NMR) equipment in the scientific research field is a superconducting magnet, which cannot function properly without the cooling of liquid helium.
Helium refrigerator provide a stable supply of liquid helium to the superconducting magnets to maintain their ultra-low temperatures and ensure that the equipment generates a uniform, stable and strong magnetic field. Liquid helium dewars are also widely used as a storage component in such equipment to ensure its continuous operation.
Controlled fusion is an important future direction for clean energy, and its core devices (e.g. tokamak devices) need to operate at ultra-low temperatures to achieve plasma confinement and stabilization. Recently, Fullcryo signed a contract with a Korean company for a kilowatt-scale helium cooling equipment. The equipment will be used in South Korea’s controlled fusion field to provide a stable deep cryogenic environment for, among other things, its superconducting magnet system.
The quantum chip is the core of a quantum computer, and the stability of its quantum bits is highly susceptible to temperature effects. It needs to operate in an ultra-low-temperature environment close to absolute zero (0K) in order to minimize the interference of thermal noise and to ensure the precision and stability of quantum computing. Helium refrigerator (especially helium cooling equipment based on dilution cooling) are able to provide a stable ultra-low temperature environment for quantum chips, and are the key support equipment for quantum computers to realize large-scale and commercial applications.
As a leading cryogenic equipment solution provider in the helium refrigeration field, Fullcryo’s liquid helium/liquid hydrogen refrigeration equipment is used in scientific research institutes and high-tech enterprises around the world, and has become a core force in driving cryogenic technology to the ground.
Fullcryo 4.5k liquid helium refrigeration equipment parameters are as follows:
| Helium refrigerator series | Refrigerating Capacity W | Compressor Rating kW |
| FHLR-40 | 160-250 | 79-90 |
| FHLR-70 | 250-320 | 90-132 |
| FHLR-100 | 320-450 | 132-160 |
| FHLR-140 | 450-580 | 160-200 |
| FHLR-180 | 580-750 | 200-250 |
| FHLR-240 | 750-900 | 250-315 |
| FHLR-280 | 900-1000 | 315-355 |
| Customized products | ≥1000 |
As the high-tech industry continues to upgrade, helium refrigeration technology will evolve toward higher efficiency, greener, and smaller size, with specific trends including:
Higher Refrigeration Efficiency: Optimize the design of cryogenic engineering systems to further improve energy recovery and reduce energy consumption, while achieving lower refrigeration temperatures.
Green energy adaptation: Combining green energy technologies (e.g. solar, wind) to optimize the power supply of Helium refrigerator and reduce fossil energy consumption.
Miniaturization and Integration: For scenarios such as laboratories and small quantum devices, we develop miniaturized and integrated Helium refrigerator to enhance the portability and flexibility of the equipment, and to promote the application of cryogenic technology in more niche areas.
