Application Research On Refrigeration Systems Of Ice Rinks With CO₂ As Refrigerant

In consideration of the environmental protection,the refrigeration system with CO₂as refrigerant in ice rinks has become a prevailing trend in foreign countries.By contrast,the CO₂ is still not available in any domestic refrigeration systems of ice rinks.However,when the Winter Olympic Games（2022）is approaching,domestic ice rinks have wit-nessed unprecedented improvements and there is a possibility that CO₂ will be utilized as the refrigerant in the ice rinks in China.This paper study the optimal layout of cooling pipes with CO₂ as secondary refrigerant,and the operation performance as well as econ-omy while using CO₂ as the refrigerant in refrigeration systems of ice rinks,aiming at providing some reference for the construction of ice rinks in China.On the one hand,in order to study the optimal layout of the cooling pipes with CO₂as secondary refrigerant,the thermal model of the ice rink is established by using ANSYS software and the independence of the grid is verified in this paper firstly.For the general applicability of the research results of the optimal layout of the cooling pipes,this paper analyzes the effect of three parameters（distances between antifreeze pipes,the tempera-ture of antifreeze in the antifreeze pipes and the temperature of soil）on the temperature of the ice surface.Based on the model mentioned above,this paper then studies the opti-mal layout of cooling pipes in six distinct kinds of ice rinks（ice hockey rink,short track speed skating rink,400 m speed skating rink,figure Skating rink,curling rink and recrea-tional ice rink）with typical structure and the ultimate research result shows that,accord-ing to the type of ice rinks,the type of climate in the area where the ice rink is located and the condensation temperature（or outlet temperature of gas cooler）of the refrigeration system,the suitable cooling pipes of the CO₂ direct system and NH₃/CO₂ indirect system are the pipes with 9.53 mm outer diameter and the optimal distances between cooling pipes fluctuate from 20 mm to 60 mm.On the other hand,this paper focuses on a typical ice hockey rink in Beijing to study the performance and economy of the refrigeration systems using CO₂ as refrigerant.Six kinds of systems（R22/glycol solution indirect system（system R1）,R22/CaCl₂ solution indirect system（system R2）,NH₃/glycol solution indirect system（system N1）,NH₃/CaCl₂ solution indirect system（system N2）,NH₃/CO₂ indirect system（system N3）and the CO₂ direct system（system C1））is selected to research.The analysis of energy consumption indicates that the system N3 consumes the least electricity while the system C1 consumes the most,but system C1 has excellent heat recovery performance.And the analysis of initial investment shows that the amounts of initial investment of system N3 and system C1 have increased significantly due to using CO₂ as refrigerant.Through the following meticulous study,however,it turns out that the dynamic annual cost to run system R1 is the highest and the dynamic annual cost to run system N3 and system C1 is the lowest.Compared with the system R1,the dynamic annual cost of system N3 and system C1 is reduced by 8.11%and 9.34%respectively.At last,this paper gives the sen-sitivity analysis,describing what effect the electricity price and the natural gas price can exert on the dynamic annual cost.After studies,this paper finally obtains the optimal external diameter and the optimal distances between cooling pipes of the cooling pipes while using CO₂ as the secondary refrigerant.What’s more,the operation performance and economy of the CO₂ direct sys-tem and NH₃/CO₂ indirect system with CO₂ as the refrigerant are compared with the con-ventional refrigeration systems.In fact,the objective of this thesis is to provide a theoret-ical basis for the construction and application of the refrigeration systems equipped with CO₂ as the refrigerant in the future ice rinks.