In the Beijing Winter Olympics, in order to give the athletes participating in the ice project a good ice experience, the team of Professor Ma Yitai and Tian Hua of Tianjin University, with the special support of the National Key Research and Development Plan for the Winter Olympics of Science and Technology, developed the international advanced carbon dioxide transcritical direct cold ice making technology through school-enterprise cooperation, and built the "most beautiful and fastest ice" for athletes from all over the world.
It is reported that the remodeled Capital Gymnasium will host two sports competitions in figure skating and short track speed skating. In both events, high-quality ice surfaces help athletes achieve better results, and in addition to the quality of the ice surface depending on the superb skills of the ice makers, the uniformity of the ice surface temperature difference and the uniformity of the soft and hardness determined by the ice making system are also key foundations. Ice machines are at the heart of artificial ice rink construction. In previous Winter Olympic Games, ice rink ice machines mainly use synthetic refrigerant technology such as Freon or ammonia refrigeration technology, the former will cause a negative impact on the climate, and the latter has certain safety risks.
The ice machine technology with carbon dioxide as the refrigerant and direct evaporation under the ice surface is considered to be a green, low-carbon, high-efficiency and energy-saving solution, but the technology has always been mastered by European and American enterprises. On the occasion of the Beijing Winter Olympics, through the collaborative research of industry, education and research, Ouyue Ice and Snow Investment Management (Beijing) Co., Ltd., Tianjin University and Est refrigeration and solar energy technology (Beijing) Co., Ltd. and other 8 units jointly developed, designed and built carbon dioxide transcritical direct cooling ice units with independent intellectual property rights, and demonstrated applications in the ice rink of the Capital Gymnasium to serve the development of the Winter Olympics and the ice and snow industry.
Co2 transcritical direct cooling technology is designed energy-saving from the four processes of compression, cooling, throttling and evaporation of co2 ice systems. For the compression process, this technology uses two-stage compression to achieve "half the effort" for the source energy consumption; design full thermal recovery for the cooling process, recover the cooling heat, and realize the hot water demand of different temperatures such as ice rink pouring and snow melting; for the evaporation process, direct evaporation and heat absorption under the ice surface is used to provide a stable cold supply for the ice rink, and optimize the design of the under-ice evaporation coil and civil engineering to ensure uniform ice surface temperature. Carbon dioxide transcritical direct cold ice making technology ice machine from the key components to the integration of the whole machine, have realized the domestic design, processing, assembly and operation, especially the water-cooled air cooler is the first application in the world, effectively solving the engineering problem of the long first body cooling circuit. The comprehensive energy saving of the technical system is more than 50%, the ice surface temperature difference is controlled within 0.3 °C to 0.4 °C, and both the comprehensive energy efficiency and the ice surface temperature difference have reached the international advanced level, thus providing athletes with a high-quality ice surface with uniform and stable softness and hardness.
The Capital Stadium will host two events, figure skating and short track speed skating, which have different strict requirements for the thickness of the ice layer and the temperature of the ice surface, and need to continuously carry out the rapid conversion of the two pieces of ice according to the schedule. In this regard, the project team also made full use of the uniform temperature of carbon dioxide ice, combined with the precision control system and linear cooling strategy, to achieve rapid and efficient ice surface conversion within 2 hours, which saved time compared with the requirements of the International Olympic Committee within 3 hours of ice conversion.
Tianjin University is one of the earliest teams in China to carry out research on carbon dioxide transcritical refrigeration heat pump technology. The carbon dioxide transcritical direct-cooling ice making technology used in the equipment is the core result of the "Ice Machine R&D and Application Demonstration" project of the National Key R&D Program for the Winter Olympics of Science and Technology, and Tian Huawei is the project leader.