Research On Optimum Specific Friction And Optimum Cooling Radius Of District Cooling System

District cooling has been applied in China,but the research on specific friction and cooling radius of district cooling systems in the industry is still lacking.This paper conducts theoretical and practical research on the optimal specific friction resistance and optimal cooling radius of the district cooling system,develops relevant application software,and promotes the promotion and application of the district cooling system.First,this paper takes the life cycle cost annual conversion cost as the objective function,analyzes the components of the life cycle cost cost,and establishes the mathematical model of the optimal specific friction of the transmission and distribution system;A new evaluation method for selecting the optimal cooling radius based on the principle of the primary energy consumption ratio ECR’of the energy consumption of the cold water circulation pump and the transported cooling capacity is proposed,and establishes a mathematical model of the optimal cooling radius,which is provided for the subsequent software compilation Theoretical conditions.Secondly,this paper analyzes the influencing factors of the optimal specific friction resistance and the optimal cooling radius.In the analysis of the influencing factors of the optimal specific friction,the effects of cooling scale,temperature difference between supply and return water,electricity price,pump efficiency,insulation material and thickness on the optimal specific friction and the economics of the transmission and distribution pipeline network were studied.In the analysis of the influencing factors of the optimal cooling radius,the influence of the temperature difference between the supply and return water,the cooling scale and the value of ECR’on the optimal cooling radius was studied.The research results show that:the cooling scale,the temperature difference between the supply and return water and the selection of ECR’are the main factors affecting the best specific friction and the best cooling radius,which can be used as the best specific friction and the most Basic input for the calculation of the best cooling radius.Thirdly,in order to facilitate the engineering application of the research results,this paper writes the optimization software for each transmission and distribution parameter of the district cooling system based on MATLAB GUI technology,and describes the interface design,software compilation and use method of the software.The software can automatically solve for the optimal specific friction resistance and the optimal cooling radius under different ECR’according to different cooling scales,water supply temperature and return water temperature;it can also automatically plot the different cooling conditions under different input conditions.R-L curve,V-R curve,V-L curve,to meet the different needs of the district cooling system pipe network design.Finally,this paper takes a district cooling system as a case,compares the optimized specific friction calculated with the best specific friction mathematical model and the specific friction calculated according to the traditional hydraulic calculation.It is concluded that the optimal specific friction of the district cooling system of the project is 42.35 Pa/m,and it is more economical to use optimized specific frictional resistance.This article also compares the cost composition of traditional specific friction and optimized specific friction in this case and the proportion of each cost reduction using optimized specific friction.This paper also calculates the optimal cooling radius for the case where the primary energy consumption ratio ECR’is 3%,5%,10%,and 15%,respectively,L_B0.03=442.99m,L_B0.05=738.32m,L_B0.10=1476.64m,L_B0.15=2214.97m.