About the Pipe Network Calculation of District Networks

Detection of Network Geometry and Components

Once the calculation has been started, the district network is analyzed in all details from the drawing. Only components of the layers that were selected in the component analysis dialog are detected.

To analyze the geometry of the district network, the trench sections are analyzed first. Trench sections in the district network are always limited by a tee or by components on which the pipe dimension changes.

The program then searches for the starting components of the district network. Start components are boilers, heat pumps and sub-network starts.

Based on this, the individual flow paths in the district network are determined. Flow paths always lead from the starting component to a heat interface unit or a sub-network end. A normal heat pipe network therefore always contains as many flow paths as the number of consumers and sub-network ends were drawn.

During the analysis, the previously selected material is automatically assigned to the pipes in the drawing, unless assignments have been made manually beforehand.

Calculation Process

Before calculating the district network, you can define various calculation settings, e.g. limit values for the maximum velocity and the pipe friction pressure loss (R-value) in manifolds and heat interface units. You can also set all the parameters for determining the heat losses, the diversity method used and the strategy for pipe dimensioning in the Settings.

When starting the pipe network calculation, the smallest dimension is selected for all trench sections for which the dimensions have not been locked. The smallest dimension always is the first active dimension in the pipe tables. If you do not wish to go beyond a certain dimension, disable smaller dimensions in the pipe tables.

The program first determines the required mass flow rates in the district network based on the mass flow rates of the consumers and, if applicable, sub-network end symbols, which you can set individually on each of the symbols. As an alternative to entering the mass flow rate, the capacity of the consumer can also be entered. Taking into account the flow and return temperatures, the corresponding mass flow rate is then automatically determined, output and considered in the calculation.

Mass flow rates are used to determine the flow resistances in the network. As soon as the limits for the R-value or the speed is surpassed, the program applies the next larger dimension to the affected pipe section (unless the dimension is specifically fixed). The program is also based on the configurations of the pipe material lists.

The last step for the calculation is the hydraulic balancing. This is done by comparing the flow path’s pressure losses and the throttle of all flow paths to the equals pressure loss as it occurs in the critical path of the trench.

The critical paths in the district network are automatically detected by the program by first determining the pressure losses in all flow paths. This critical path is highlighted in color in the flow paths table of the calculation dialog and can be selected with the U key.

The network is then hydraulically balanced.