Liu Kai, a native of Chongqing, opened his recent WeChat circle of friends, which at first glance does not seem to be much different from others, mostly cheering for Chinese athletes at the 2022 Winter Olympics in Beijing. But if you turn forward a little, you will find that there is a lot of dry space inside.
Screenshot of Liu Kai's circle of friends
On January 26, he shared a circle of friends at the Capital Gymnasium with the content "This is called CO₂ (carbon dioxide) transcritical straight cold ice rink", accompanied by a map that looks like a circular runway, with corresponding temperatures marked in 9 different places. Looking closely, there are actually only two temperature values of -8.8 degrees and -8.7 degrees in 9 places, which means that the temperature difference is only 0.1 degrees.
Today, more than a month later, as one of the main venues of the Beijing Winter Olympics, the Capital Gymnasium has been broken with 7 Olympic records and 1 world record, and the Capital Gymnasium is also known as the "fastest ice" along with the National Speed Skating Hall, which has broken 10 Olympic records. What makes Liu Kai proud is that the "fastest ice" of the Capital Stadium is created by him and his team!
Four years ago, due to the Winter Olympics, he was invited to Beijing to participate in the construction and transformation of venues
Liu Kai is a facility support officer for the Beijing 2022 Winter Olympics. Courtesy of respondents
Liu Kai was born in Chongqing in 1979 and was admitted to the then Heilongjiang Business School (now merged and renamed Harbin University of Commerce). Just saying the name of the school may feel strange to many people, but in terms of profession, it is not ambiguous at all. "My major was called freezing and refrigeration at the time." On the 17th, when interviewed by the upstream news reporter, Liu Kai proudly said at the beginning, "In the refrigeration engineering community, half of the talents are from our school (laughs). ”
After graduating in 2002, Liu Kai naturally entered the field of industrial refrigeration, which is a professional counterpart. "Cold storage, cold chain design and construction in daily life are all within our professional scope." Liu Kai said that until 2017, he was the chief engineer of a central enterprise in the industry, Chongqing Company.
"I arrived in Beijing in October 2017." The new company Liu Kai went to this time is called Est Refrigeration and Solar Technology (Beijing) Co., Ltd. He is also the chief engineer, but this time compared with his previous work experience of more than ten years, there is a big difference: he was invited to Beijing for the construction and transformation of the venues of the Beijing 2022 Winter Olympics.
The first piece of CO₂ transcritical direct cold ice surface of the Beijing Winter Olympics was made by him
Ice-making work in the Capital Gymnasium ahead of the Beijing Winter Olympics in January. Xinhua News Agency photo
When the interview topic entered the Beijing Winter Olympics, Liu Kai's speed of speech was obviously faster, and there was irrepressible pride and excitement between his words. The first thing that caught the reporter's attention was a series of numbers. The first figure is 1800 square meters.
According to Liu Kai, including the Winter Olympic training grounds, there are currently 49 ice surfaces in Beijing with an area of more than 1,800 square meters. The reason why the emphasis on an area of more than 1800 square meters is because the larger the ice surface area, the more difficult it is to make ice. This point is explained separately by Liu Kai later.
"Of these 49 pieces of ice, our company has made 50%. These include 4 blocks of Shougang Park, as well as short track speed skating, figure skating, ice hockey, curling national team training grounds and so on. "Liu Kai is like a family treasure.
It is worth mentioning that the Beijing 2022 Winter Olympics had been declared the first large-scale use of carbon dioxide refrigerants in history long before the opening. The most direct embodiment of this is that 7 ice surfaces in the Beijing competition area have adopted clean, low-carbon carbon dioxide transcritical direct cold ice making technology, which is the first time that this technology has been applied at the Winter Olympic Games. Liu Kai told the upstream news reporter, "4 of these 7 pieces were designed and built by my team. ”
This includes the Capital Gymnasium, which completed its first ice making in November 2020. It is not only the first piece of carbon dioxide transcritical direct cold ice surface of the Beijing 2022 Winter Olympics, but also the ice surface that Liu Kai and his team have devoted the most efforts to.
Carbon dioxide large-area ice making design, construction is very difficult
In addition to green environmental protection, carbon dioxide ice production has an important advantage that ice making is fast and the ice surface temperature is uniform. On the speed skating rink, the temperature is uniform, the smaller the temperature difference, the more uniform the hardness of the ice surface, and the smoother the ice surface. In layman's terms, the more "silky" the ice surface, the more conducive to the skating of the players, the more conducive to creating good results.
According to Liu Kai, before the Beijing Winter Olympics, there were about 20 sports venues in the world that used carbon dioxide to make ice. "Concentrated in Europe, Canada, I've seen it. These venues are generally not very large in size, and are mostly used in commercial projects and training. ”
Since carbon dioxide is greener and more environmentally friendly as a refrigerant, why is it not widely used until the Beijing Winter Olympics? Liu Kai explained that this is closely related to the difficulty of construction in the design and construction process.
The use of carbon dioxide direct evaporative refrigeration requires the coil containing the refrigerant carbon dioxide to be buried in the ground of the site; at the same time, the pressure of carbon dioxide gas is very large. "This puts forward higher requirements for design and construction." Liu Kai said that in the Capital Gymnasium, which eventually broke 7 Olympic records and 1 world record, the coil spacing of his own design was 75 mm, and a two-layer concrete pouring scheme was used to "clamp" the heat exchange coil in the middle.
The design and construction and technical research are all completed by the Chinese themselves
3 mm is the second important number mentioned by Liu Kai.
"Our concrete pouring is a 61x31 m, 1800 m2 flat surface without dividing seams, and the flatness must be within plus or minus 3 mm." Liu Kai said that this is why he will emphasize the ice surface of more than 1800 square meters, "such a large area without dividing seams, how to solve the thermal expansion and contraction of concrete is a big problem." At the same time, he also mentioned that the accuracy of the heat exchange coil is also up to plus or minus 3 mm.
It is worth noting that Liu Kai also mentioned that taking the ice surface production of the Capital Gymnasium as an example, the most difficult thing is actually to achieve carbon dioxide transcritical ice-making refrigeration units. "It's something we haven't done before." But Liu Kai said that even so, the machine for making ice for the ice surface of the Capital Gymnasium was designed by his own team.
Although the machine was then produced by a foundry, "the two-dimensional drawing and three-dimensional drawing of the entire machine, all the technical details were provided by us, and the factory was only responsible for the production as ordered." This also means that the "fastest ice" of the Capital Stadium was designed and built entirely by the Chinese themselves.
Dutch Susanna Shultin (left) breaks the world record in the women's 1,000m quarterfinals of the short track speed skating event at the Capital Gymnasium on Feb. 11. Xinhua News Agency photo
Throughout the interview, Liu Kai's honor and excitement for participating in the Beijing Winter Olympics as a senior technical support person has always been overflowing. Upstream reporters also noted that since the opening of the Beijing Winter Olympics, Liu Kai's locations for sharing the content of the circle of friends are almost all in the Capital Gymnasium. Not only is he cheering for the performance of Chinese athletes, he has said more than once that no matter which country's athletes win gold medals and break world records, it is "a consolation to the hard work of our capital stadium ice machine room security team!" ”
Upstream journalist Qiu Jinyi