Modeling the dynamic characteristics of a district heating network

The study of the dynamic characteristics of the district heating (DH) systems is a necessary prerequisite for the control strategy. Through the study of the primary system and secondary system in DH systems, dynamic models of the DH network are built in this paper. Two important parameters and their mathematical expressions representing the dynamic characteristics of the DH network are described. These parameters include the lag time and relative attenuation degree of DH systems. Test data about three heat exchange stations were used in the calculation of the lag time and relative attenuation degree in the process of solving the dynamic models. Peak-valley method was introduced to find the actual lag time, and the correspondence analysis method was used to obtain the actual relative attenuation degree. The comparison of actual data with calculating data of the two parameters verified the correctness of the dynamic models. The lag time is proved to be approximately equal to the flow time of the heat medium in the DH network, and some parameters influencing the relative attenuation degree are analyzed. This will help the technicians to regulate the DH systems in the process of operation and management using the two parameters.