District heating system#
The district heating system is a great example for the usage of flexible user-defined subsystems. The example system and data are based on the district heating system Hamburg Wilhelmsburg . The source code for this example can be found here. Although the structure of the system (see the Figure below) does not seem very complex, it has more than 120 components. But we can easily determine repeating structures for the consumers and this is, where the subsystems come in place.
The single consumers are connected to the main grid with a control valve at the outlet and each fork is connected with a pipe to the next fork. Also, the main grid may have a dead end (e.g. in the housing areas, see subsystem closed) or is open to connect to another part of the grid (industrial area, see subsystem open). Additionally, each branch of the main grid is connected to the upstream part with the fork subsystem (Ki, see subsystem fork).
After the system has been set up, we designed the pipes’ insulation in a way, that the feed flow the temperature gradient is at 1 K / 100 m and the back flow gradient is at 0.5 K / 100 m. Having designed the system, heat losses at different ambient temperatures can be calculated, as the heat transfer coefficient for the pipes has been calculated in the design case. By this way, it is for example possible to apply load profiles for the consumers as well as a profile for the ambient temperature to investigate the network heat losses over a specific period of time.