Simulation Of Dynamic Thermal-hydraulic Coupling Characteristic Of Ring District Heating Network

Ring district heating(DH)systems are widely used in many large-scale heating systems,which correspondingly increase the difficulty of hydraulic and thermal dispatch.In this paper,the dynamic hydro-thermal coupling model is proposed based on the steady-state hydraulic model and dynamic thermal model.The dynamic characteristics and operation cost of DH network are analyzed.Firstly,the steady-state hydraulic model of the ring-shaped DH network is established and solved by the basic circuit matrix method.Dynamic thermal model is subsequently constructed based on the energy conservation equation and is solved by the first-order implicit upwind scheme,which is fast and unconditionally stable.The dynamic thermodynamic and hydraulic coupling calculation model based on breadthfirst traversal is proposed,and the calculation flow of this algorithm is given by MATLAB.When the hydraulic and thermal conditions of the loop central heating network change simultaneously,this algorithm can be used to analyze it.Analysis of dynamic characteristics of DH network are performed in a town of North China.Results show the proposed method can predict the thermal dynamics under the simultaneous change of hydraulic and thermal conditions.The temperature lag and attenuation of each thermal station are studied based on the proposed algorithm.Results show the time delay of heat transportation in DH system is apparent.The farther away from the heat source,the longer time delay.Temperature attenuation at the thermal station concerns with the supply water temperature at heat source and the distance between thermal station and heat source.Moreover,this method is significant in guiding the operation and optimal control of DH system.In this paper,the hydro-thermal coupling calculation of ring-shaped DH network is conducted within two operation modes(quantity regulation and quality regulation).Energy consumption of heat transmission and distribution is calculated to analyze the consumed energy during the dynamic operation.Reasons for the changed energy consumption are also studied.