The researches on Integrated Energy System continue to thrive nowadays, since it can promote the use of renewable energy and increase energy consumption efficiency. In this paper, a novel modelling method of District Heating Network (DHN) considering the change of the thermodynamic states of the working fluid is proposed, based on the basic components in DHN, including the pipelines, pressure sources (PSs) and junctions. And a corresponding DHN model constructed of these components is established. By applying this method, DHNs with diverse topologies, even with different supply and return networks, can be analyzed. In order to solve the equations efficiently, Newtonâ€™s method with its partial derivatives obtained by a numerical method is applied, and an appropriate set of initial values is also discussed. Finally, case studies of a cogeneration system are performed to demonstrate the validity of the proposed models as well as the analyzing methods.
Keywords Cogeneration systems, District heating network models, thermodynamic properties of working fluid, modified Newtonâ€™s method