Written/Reporter Wang Xueying Editor/Ding Lin
New Media Editor/Song Meng
Scientific audit:
Yang Yong'an (Professor, Department of Refrigeration and Air-conditioning Engineering, Tianjin University of Commerce)
▲ On February 8, the beijing 2022 Winter Olympics speed skating men's 1500 meters final was held at the National Speed Skating Hall "Ice Ribbon". Dutch player Kay Nuis in the race. (Photo by Xinhua news agency reporter Xue Yuge)
In addition to the excellent performance of the athletes themselves, the national speed skating hall "Ice Ribbon" competition venue is also indispensable.
Have you ever wondered why the "ice ribbon" can be so "smooth"? What are some of its commendable unique features? Let's find out together in the following.
The National Speed Skating Hall, known as the "Ice Ribbon", is the iconic venue of the Beijing Area of the 2022 Winter Olympics. Not only is the ice ribbon the largest all-ice design in Asia (with an ice surface area of up to 12,000 square meters), but it is also the first Winter Olympic venue in the world to adopt "CARBON DIOXIDE Transcritical Direct Evaporative Refrigeration Technology".
As a very distinctive "China solution" during the 2022 Winter Olympics, carbon dioxide transcritical direct cold ice making technology is regarded as one of the most advanced, environmentally friendly and efficient ice making technologies at present. So, where is this technology?
In fact, the principle of carbon dioxide refrigeration is similar to the refrigerant cycle in ordinary air conditioners: carbon dioxide is gaseous at room temperature and pressure, but after applying a certain high pressure, carbon dioxide will become a critical state of fluid; these fluids are then sent to the area where refrigeration is needed, and a large amount of heat absorption will be absorbed during its evaporation process, and then the purpose of cooling and cooling will be achieved.
▲ In September 2020, during the construction of the "Ice Ribbon", the staff was laying the refrigeration pipeline system (Source: Visual China)
"The most critical feature of this technology is that it is atmospheric friendly, and it does not cause ozone layer destruction, which contributes very much to carbon peaking and carbon neutrality." Yang Yongan, a professor in the Department of Refrigeration and Air Conditioning Engineering at Tianjin University of Commerce, explains.
For a long time, chiller manufacturers or winter sports venues have used Freon compounds as the main refrigerant. However, since 1971, with the gradual improvement of the scientific community's understanding of Freon, people have finally realized that Freon-like substances can cause environmental hazards such as ozone layer destruction and greenhouse effect. In contrast, carbon dioxide refrigerants, as natural refrigerants, appear to be both environmentally friendly and safe.
Although carbon dioxide is a greenhouse gas, its greenhouse effect is much lower than that of the Freon-type synthetic refrigerants used in conventional refrigeration systems. For example, R134a refrigerant, which is commonly used in automotive air conditioning systems, has a global greenhouse effect potential (GWP) of 1300 – 1300 times that of carbon dioxide refrigerants (GWP value of 1).
▲In January 2021, the "Ice Ribbon" completed the first ice making (Source: Visual China)
Not only that, but CO2 refrigeration is also more energy efficient than conventional refrigeration systems. Yang Yongan pointed out that the thermodynamic properties of carbon dioxide are very excellent: "In the case of reasonable system design, its efficiency is close to that of conventional systems, and the system is compact and the size of the unit is small... The flow resistance (in the pipeline) is very small, so when used, the working medium pump has little power and the pressure loss in the evaporator is also small. Therefore, carbon dioxide refrigeration technology is more in line with the concept of "green, energy saving and environmental protection" of the Beijing Winter Olympic Games.
In addition to being more environmentally friendly, carbon dioxide as a refrigerant also has the advantages of no odor, non-flammability, non-combustion, and is safer than flammable refrigerants such as alkanes.
It is reported that in order to better play the advantages of carbon dioxide direct cold ice, the "ice ribbon" is equipped with an advanced intelligent energy management system, which can efficiently recover the waste heat generated by the refrigeration system, and provide nearly 70 °C hot water for the dehumidification of the venue, the maintenance and watering of the ice surface and the daily needs of athletes.
In the case of full ice operation, the "ice ribbon" can save more than 2 million kWh of electricity per year in the refrigeration link alone, which is equivalent to the electricity consumption of more than 6,000 households in Beijing for a month. As carbon emissions approach zero throughout the refrigeration process, this is comparable to the carbon reduction achieved by planting more than 1.2 million trees.
As the speed skating venue of this Winter Olympic Games, "Ice Ribbon" has extremely high requirements for the quality of the ice surface. Uneven ice temperature will cause the ice surface to be soft in some places, and the ice surface in some places to be too hard - for speed skaters, too soft ice surface will lead to slower speed, and too hard places may not be able to pedal the ice, affecting the player's competition performance.
▲ In October 2021, the first Beijing Winter Olympic Test Match "Meet in Beijing" Speed Skating China Open was held in the "Ice Ribbon". Pictured is Chinese player Yang Binyu in the women's 3000m competition (Source: Visual China)
Traditional ice rinks usually use indirect refrigeration (e.g. the use of Freon refrigerants, glycol carrier refrigerants), and because the refrigerants are often not heated at a fixed temperature, the ice temperature difference between such ice rinks is generally as high as 1.5 °C-2 °C.
In contrast, the "ice ribbon" adopts carbon dioxide direct cooling ice system, which not only has higher heat exchange efficiency of the system, but also uniform ice temperature, and its ice surface temperature difference can basically be controlled within 0.5 ° C, which helps to create the "fastest ice" for top events.
(This content is jointly produced by Beijing Science and Technology News and China Digital Science and Technology Museum)
Producer: Popular Science Central Kitchen
Producer: Beijing Science and Technology News | Beike Media
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