The Beijing Winter Olympics, which "drives 300 million people to participate in ice and snow sports", is in full swing. On February 5, the Chinese short track speed skating team composed of Wu Dajing, Ren Ziwei, fan Kexin and Qu Chunyu won the champion of the 2000 meter relay of the short track speed skating mixed team in the Beijing Winter Olympic Games and won the first gold medal of the Chinese team in the current Winter Olympic Games. The production of Shoujin is known as "the fastest ice meets the brightest star". The fast and slippery ice has always been one of the most important sports stages in the Winter Olympic Games. In addition to short track speed skating, there are many winter Olympic events that need fierce competition on the ice, such as speed skating, figure skating, curling, hockey and so on. This "ice and snow" is very different from the ice and snow of nature. It is not only the key factor affecting the competition results, but also related to the competitive safety of athletes. The process of making ice for the Winter Olympic Games is complex and the standards are strict. Moreover, many scientific and technological achievements are "hidden" under this ice. Different events need different ice In nature, water freezes when it is below 0 ℃. However, the making of "Winter Olympic ice" is not so simple. It should not only form quickly and have a smooth surface, but also meet the different needs of different competition events for ice surface temperature and thickness. So, what is the difference in the ice required for different ice sports in the Winter Olympics? Short track speed skating, the first gold project of the Chinese team in this winter Olympic Games, needs "the fastest ice", which requires the ice thickness of 3cm to 5cm and the ice temperature of - 7 ℃ to - 6 ℃. Short track speed skating is called "short track", and its ice track is 111.12 meters per lap. Compared with speed skating, which is called "Avenue", the perimeter of the ice path is much longer, 400 meters. Therefore, the "Avenue" requires the ice thickness to be 2.5cm to 3cm, and the ideal ice temperature is - 9 ℃ to - 5 ℃. Figure skating, known as "ice dance", requires a thickness of 6 cm to 7 cm and a temperature of - 4 ℃ to - 3 ℃. In order to be beautiful, athletes will also wear lighter and shiny clothes, so room temperature should also create a warm feeling like spring. In addition to skating, there are ice hockey, curling and other ice sports in the Winter Olympic Games, which also put forward different requirements for "Winter Olympic ice". Ice hockey and curling competition requires the ice surface temperature to be - 6 ℃, and the ice surface is required to be extremely flat. In the curling competition, the flatness deviation of 1mm on the ice surface will have a great impact on the direction of the curling, and then affect the players' play. On the ice hockey competition field of the National Stadium, the 1800 square meter ice surface is required to be a horizontal plane with an error of no more than 0.5mm. The Chinese ice making team of the Winter Olympic Games is striving to control the error within 0.1mm-0.2mm. The ice used in different competitions of Winter Olympics requires different temperatures and thicknesses. In the final analysis, it is because various competitions need ice with different hardness. The temperature and thickness of the ice surface will affect the hardness of the ice surface, thus affecting the performance of athletes. Take figure skating as an example. If the ice temperature is too low, the ice is easy to crack when athletes take off and fall; If the temperature is high, the ice will soften, and athletes will feel that the skate "can't be pulled out" and affect the take-off. Speed type short track speed skating and other events have lower requirements for ice temperature, so that the ice surface will be harder, which can provide better strength support for athletes and facilitate speed increase. There are these ways to create "Winter Olympic ice" In order to meet the demand for ice in various events of the Winter Olympics, China's ice making team made great efforts and began preparations early. Generally speaking, the ice making process consists of making basic ice, spraying white paint, pasting signs and drawing lines, making surface ice and other steps. Before ice making, the floor should be deeply cleaned. After the floor is pre cooled for 12-18 hours, the basic ice can be made. Making foundation ice can be regarded as the link of "laying foundation", in which ensuring the flatness of foundation ice is extremely important. If the foundation ice does not fully fit the concrete ground, the ice may crack after athletes step on it. Therefore, the basic ice needs the ice maker to sprinkle water evenly on every point of the field with a spray stick to make an ice layer about 2 cm thick. After paving the basic ice, the stadium is not the "milk white" ice rink familiar to the audience. This is because the ice maker has not finished spraying white paint. By spraying white paint on the basic ice layer, the ice that originally shows the color of concrete ground will become more beautiful milky white. After the white paint is fixed, the ice maker pastes the logo, mixes the weighed paint with soft water according to the proportion, and starts the line drawing work. The position and width of the line drawing need to meet the requirements of the international ice Federation standard. After pasting the logo and drawing lines, you can start making surface ice with a thickness of about 3cm. Finally, the ice making work can be truly completed by grinding and leveling with an ice sweeper. At the same time, the maximum height difference of ice surface within any 3 square meters shall not exceed 2mm. If making a curling track, the ice maker needs to "dot", that is, spray pure water on the ice to form uniform ice particles, and scrape the track to the required height and shape with an ice sweeper. In the process of ice making, ensuring accuracy is a major difficulty. For example, an ice maker needs to water the ice pipe to freeze the water into ice and form a whole piece of ice. In this process, if the pace of the ice maker is inconsistent when watering, it is easy to cause inconsistent thickness of the frozen ice. Therefore, when making ice, ice makers not only have time limit requirements, but also need accurate control. This means that ice making is a "manual job". "There's a lot of dirty work, heavy tools and cold ice. Sometimes, you have to work on the ice at - 6 ℃ for 16 to 18 hours." Zhang Zhiyuan, an ice maker at the curling venue of the Beijing Winter Olympic Games, said. Technology support to ensure competition ice In addition to "manual work", there are many "technical work" supported by scientific and technological achievements in ice making. The clean and low-carbon carbon carbon dioxide transcritical direct cooling ice making technology was adopted for the first time in the Beijing Winter Olympic Games. This is currently the world's most environmentally friendly ice making technology, with carbon emissions approaching zero, helping to create the fastest and most environmentally friendly ice. Compared with the traditional ice making technology, it not only improves the energy efficiency by more than 20%, the temperature difference on the ice surface can be controlled within 0.5 ℃, and the ice made is more uniform. There will be no different temperature and uneven hardness on each part. Zhang Xinrong, a professor at Peking University and a well-known expert in the field of international natural working medium research, believes that carbon dioxide transcritical direct cooling ice making technology has the advantages of high safety, low energy consumption and operation cost, environmental friendliness, and all heat can be recycled. It is one of the most promising working medium in the energy system of ice venues, which can make the cold and heat integration and efficient operation of the energy system of venues, It has broad application prospects all over the world. Experts from IFS have suggested adopting the internationally used environmental protection ice making technology, but after one and a half years of exploration, the Chinese team decided to choose the carbon dioxide transcritical direct cooling ice making technology. Carbon dioxide transcritical direct cooling ice making is to heat and pressurize gaseous carbon dioxide to form supercritical carbon dioxide fluid, then cool and depressurize the supercritical carbon dioxide fluid to - 20 ℃ to - 15 ℃, and then phase change evaporation and heat absorption to complete the process of refrigeration and ice making. The "ice ribbon" of the national speed skating hall is the world's first Winter Olympic Stadium using carbon dioxide transcritical direct cooling ice making technology. In the "ice ribbon", 12000 square meters of crystal clear ice showed a wonderful competitive scene for the world audience. In addition, the monitoring system is also the right "assistant" of the ice project. The staff of the former "Water Cube" and now "ice cube" venues have specially established a set of "health monitoring" system for the curling field, including acceleration sensor, strain sensor and ambient temperature sensor, which can not only monitor the deformation and vibration of the structure, but also monitor the ambient temperature and the inclination of the overall structure, The safety and competition comfort of the structure are evaluated in real time. Intelligent building management system has also contributed scientific and technological strength to the Winter Olympic Games. Zhang Jinquan, the responsible engineer of the ice cube venue operation Department and the assistant of the international ice maker, said that the curling competition has strict requirements for the venue environment. The temperature on the site must be controlled according to three layers: the ice surface temperature, the height temperature of 1.5m above the ice surface and the stand temperature. The temperature control of each layer must reach high precision. "Ice cube" upgraded the intelligent building management system and added dehumidification function to ensure the ice quality of the stadium. (Xinhua News Agency)