Study On Optimization Of Pipe Network Of Regional Heating And Cooling System

The district cooling and heating system provides conditions for the application of renewable energy,helps promote the transformation of China’s energy structure,reduces greenhouse gas emissions,and realizes the long-term benefits of sustainable development.However,the actual operation of the district cooling and heating system has the problems of large initial investment and high operating cost.Based on the above background,this paper optimizes the resistance of the primary pipe network,the diameter of the secondary pipe network,and the insulation thickness of the pipeline in the district cooling and heating system,proposes optimization measures and optimization methods,and compiles the optimization program of the pipe network in order to improve the economic efficiency of the district cooling and heating system reduces the design difficulty,improves the design accuracy,and promotes the better development of the district cooling and heating system.Cooling and heating load calculations are very important and are the basis for the design of district cooling and heating systems.Using Design Builder to build typical building models for commercial,office,and residential buildings,the hourly load and annual dynamic load of each design are obtained.It is found that the load characteristics of the three typical buildings are very different,mainly affected by outdoor weather data and internal disturbance.The cooling load indexes of typical commercial,office,and residential buildings are 147.8 W/m~2,107.1 W/m~2,and 61.7 W/m~2 for typical commercial,office,and residential buildings,and the heat load indexes are 69.2 W/m~2,52.7 W/m~2,39.1 W/m~2.Measures to reduce the resistance of the primary pipe network computer room are proposed,and ANSYS Fluent is used to perform CFD simulations on 90°and 135°bends and bends with different curvature radii to verify the optimization effect.The simulation results found that the use of 135°elbows instead of 90°elbows can effectively reduce the local drag coefficient by 20.29%;the elbows with Rc/D=1.5 and Rc/D=2 are more energy-efficient than those with Rc/D=1.The tube effectively reduces the local drag coefficients of 17.63%and 22.86%,and the optimization effect is obvious.A new method for optimizing the diameter of the secondary pipe network is proposed,and branch correction coefficients are introduced on the basis of the segmented optimization ideas and theories.Taking the whole life cycle annual calculation cost of the entire pipeline network(main line+branch)as the objective function,a mathematical model of the annual calculation cost of the secondary pipeline network based on the hourly load throughout the year is established,and the"pipe diameter optimization"program is compiled to provide Designers use.Use this program to optimize a regional cooling and heating project.The new pipe network optimization method has obvious economic advantages compared with the traditional pipe diameter design method.The initial investment of the pipe network is reduced by 26.67%,and the life cycle cost is reduced by 8.39%.Analyze the cold and heat loss of the secondary pipe network.The cost caused by the cold and heat loss of the pipeline is the main source of the cold and heat loss of the secondary pipe network,accounting for 83.37%,and the cost caused by the temperature rise and heat loss of the water pump only accounts for 16.63%.Establish a mathematical model for calculating the annual cost of insulation,compile the"Insulation Thickness Optimization"program in the MATLAB environment,optimize the pipeline insulation thickness,and study the economic insulation thickness and cold and heat loss of pipelines under different pipe diameters.As the pipe diameter increases,the economical insulation thickness increases first,then decreases,and remains unchanged for a while.In the cumulative annual cold and heat loss of the pipeline,the cumulative heat loss of the water supply pipe during the heating period>the cumulative heat loss of the pipeline return pipe during the heating period>the cumulative cold loss of the pipeline water supply pipe during the cooling period>the cumulative cold loss of the pipeline return pipe during the cooling period,respectively 37.09%,28.38%,22.31%,12.22%...