Comprehensive Analysis Of Energy Storage And Thermal-hydraulic Coupling Of Working Medium In Urban Heating Network

In most countries,the construction industry accounts for the largest share of total energy consumption and about a third of carbon emissions.In addition,with the progress of urbanization,people’s need for improved living standards is becoming more and more urgent.China’s climate varies widely across the country,which has a decisive impact on the demand for space heating.Optimizing existing heating networks and designing new heating systems that include a higher share of renewable and clean energy are effective ways to improve energy efficiency,reduce carbon emissions and improve people’s living standards.There is a large amount of energy storage in the heating pipe network system because it contains lots of pipes and heat exchangers,etc.The rational utilization of the energy storage mentioned above can achieve the purpose of improving energy efficiency and supplementing the gap of peak and frequency regulation in urban grid.In terms of energy storage and utilization of heating pipe network,the modeling of heating pipe network is carried out in two parts: heat transfer and energy storage.The influence factor θ is introduced into the energy storage model to improve the accuracy of the average heat transfer temperature in the heat exchange section.The model can be used to calculate the sustainable time when the heating pipe network uses its working medium to store and supply energy under the shutdown condition of the unit.The model can be used to calculate the duration of thermal storage energy under the condition of the unit failure shutdown.In the case of time-divided heating,the model deals with the change of heat demand caused by the change of outdoor temperature through quality regulation and quantity regulation,so as to obtain the guidance temperature and flow of secondary water supply.The thermal characteristics of heating network are generally divided into steady-state thermal characteristics and dynamic thermal characteristics.In this paper,the steady-state thermal characteristics of heating pipe network are modeled,solved and applied.According to the steady-state model of heating network,the thermal dynamic characteristics are discussed.The inlet temperature is disturbed,and the temperature is linearized when the heat network does not reach the steady state,and the dynamic temperature of the heating network with any location and any time is obtained.Thermodynamic characteristics and hydraulic characteristics of heating network are inseparable.Based on the analysis of the thermodynamic characteristics of the heat network,this paper analyzes the thermal-hydraulic coupling of the heating network.Two methods(basic mass conservation,energy conservation equation method and graph theory matrix method)are used to model and analyze the hydraulic power of heating network.In the modeling by graph theory,the structural information of the heating network is calculated by transforming it into a mathematically expressed directed graph.On the basic of hydraulic model,combined with the thermal characteristics model of heating pipe network in Chapter 3,the thermal-hydraulic coupling model of heating pipe network is obtained and the model is calculated and analyzed.