China achieves major breakthroughs in cryogenic refrigeration technology

Creating an ultra-large cryogenic "refrigerator" that provides an ultra-low temperature environment below 20K (minus 253 degrees Celsius) or even down to 2K (minus 271 degrees Celsius), while ensuring continuous and stable operation at hundreds of watts to tens of thousands of watts—this capability has earned large cryogenic refrigeration equipment the title of "ultra-low temperature factory."

Scientifically, 20K is known as the liquid hydrogen temperature range, while 2K is the superfluid helium temperature range. Large refrigeration equipment operating in the liquid hydrogen to superfluid helium temperature ranges plays a crucial supporting role in aerospace engineering, hydrogen energy storage and transportation, helium resource development, and the operation of many large scientific installations. For a long time, China had relied almost entirely on imported large cryogenic refrigeration equipment.

Photo shows a large cryogenic refrigeration system from liquid helium to superfluid helium temperature ranges developed by the Technical Institute of Physics and Chemistry under the Chinese Academy of Sciences (TIPC-CAS). (Photo provided by the TIPC-CAS)

After over 10 years of sustained efforts, a research team from the Technical Institute of Physics and Chemistry under the Chinese Academy of Sciences (TIPC-CAS) has succeeded in developing a series of key and core technologies and launched large-scale cryogenic refrigeration equipment operating from 20K to 2K and from hundreds of watts to kilowatts, enabling the domestic manufacturing of these "ultra-low temperature factories."

"Helium gas becomes a liquid at minus 269 degrees Celsius and turns into superfluid helium at minus 271 degrees Celsius. What cools the high-field superconducting magnets in particle accelerators like the Beijing Electron Positron Collider (BEPC) is exactly the liquid helium or superfluid helium produced by large cryogenic refrigeration equipment," said Hu Zhongjun, a researcher with the TIPC-CAS, in front of a display board for the BEPC at the National Science Library, Chinese Academy of Sciences.

Apart from the BEPC, the operation of other large scientific facilities such as the Shanghai Synchrotron Radiation Facility and the High Energy Photon Source also relies heavily on large cryogenic refrigeration equipment.

Experts believe that China sees an increasingly urgent demand for large cryogenic technology and equipment as it experiences rapid economic and social development. However, to independently develop such equipment is exceptionally difficult.

"Large cryogenic refrigeration equipment is different from common air conditioners or refrigerators," said Liu Liqiang, a researcher with the TIPC-CAS, adding that the systems needed are extremely complex.

In 2009, the TIPC-CAS took the lead in conducting research on key core components and system integration for large cryogenic refrigeration systems.

From October 2010 to December 2014, the TIPC-CAS developed China's first domestically produced large cryogenic refrigeration system operating in the liquid hydrogen temperature range with a capacity of 10,000 watts.

In April 2015, a project was launched to develop a large cryogenic refrigeration system from liquid helium to superfluid helium temperature ranges. After more than five years of efforts, the researchers, building on previous achievements, not only independently developed large helium refrigerators with specifications of "2500W@4.5K" and "500W@2K", but also made a series of breakthroughs in refrigeration technology for liquid helium and superfluid helium temperature ranges, allowing China to join the ranks of internationally advanced nations in this field.

However, simply producing a prototype was not enough, and industrialization was needed to drive the development of upstream and downstream industries.

Given the high applicability of and urgent industrial demand for large cryogenic refrigeration equipment, the TIPC-CAS abandoned the traditional path of commercialization, and creatively explored the application and commercialization of the equipment while it was still in the R&D phase.

Under this model, the equipment has been commercialized exactly when it was fully developed. In 2016, the TIPC-CAS, in collaboration with private capital, set up Beijing Sinoscience Fullcryo Technology Co., Ltd. (Fullcryo).

"Research institutes excel at technology development while enterprises are strong in engineering transformation. The complementary advantages shorten the commercialization cycle and enhance the capability of China's cryogenic industry," said Zhang Yanqi, chairman of board of Fullcryo.

It is reported that the implementation of the large cryogenic refrigeration equipment project has driven China to establish a complete chain from R&D, engineering demonstrations to industrial applications in this field.

At the same time, it has boosted the innovation capabilities of related supporting companies, initially forming a comprehensive and clearly divided low-temperature industrial cluster.

Zhang explained that through enterprise-university-research institution collaboration, Fullcryo rapidly grew into a leading enterprise in the cryogenic industry.

Fullcryo was the first in China to develop a series of multi-specification large hydrogen-helium refrigeration equipment and liquefaction systems for the cryogenic temperature range, allowing China to establish itself in the global manufacturing of large cryogenic refrigeration equipment.

Today, more and more major projects are using large cryogenic refrigeration equipment independently developed by China, from superconducting accelerators, to ground testing of spacecraft, and to advanced light sources. China's helium refrigerators and hydrogen liquefiers with hundreds of watts of capacity have been applied in major international scientific projects as well.