Sizing of 5GDHC networks
Learn how to design passive 5GDHC networks using the nPro software. Active networks with a central pump are dimensioned like traditional district heating networks based on a fixed pressure gradient (Pa/m).
General information
nPro employs a unique approach to dimensioning 5GDHC networks. The design primarily relies on calculating the maximum allowable pressure gradient (Pa/m). Users can customize the design by incorporating individual parameters, ensuring the dimensioning fits the specific conditions of the system being analyzed.
Assumptions for designing passive 5GDHC networks in nPro
The circulation pumps in decentralized heat pumps perform all the pumping work and determine the maximum permissible pressure loss in the critical path of the system. The pressure loss in the energy hub is calculated either from the losses in ground heat exchangers (based on user-defined parameters) or from a predefined value. The total pressure loss along each path, including pipeline losses, a percentage for fittings, calculated or predefined losses in the energy hub, and losses in substations of the buildings, must not exceed the pressure head of the decentralized heat pump.
Parameters and settings for designing a passive 5GDHC network
The circulation pump must be configured to "decentralized". Ensure that the specified pressure head matches the maximum pump head of the heat pumps. The pressure loss in the energy hub must also be specified — either through the parameters of the boreholes or a predefined loss value. To obtain a valid network design the pressure loss in the energy hub must to be lower than the maximum pressure head of the decentral heat pumps.
Design criterion for a 5GDHC network in nPro
The design of a 5GDHC network in nPro is based on the maximum allowable average pressure gradient along a path, defined as the shortest connection between a building and the energy hub. The design ensures that the pressure loss in the pipes does not exceed the allowable limit. The maximum allowable average pressure gradient is determined as follows:
$$ \text{max pressure gradient}_\text{path} = \frac{\left(\text{pump head}_\text{decentralized} - \Delta p_\text{energy hub}\right)}{1 + \left(\frac{\text{percentage of fittings losses}}{100}\right)} \div L_\text{path length} $$
Here, \( \Delta p_\text{energy hub} \) represents the pressure loss in the energy hub, and "percentage of fittings losses" accounts for the additional losses from pipe fittings. \( L_\text{path length} \) is the path length in meters. By iterating over all connections, the smallest maximum pressure gradient is established for each path. Depending on the selected method (load profiles or heating load), the maximum flow rate is calculated, and the pipes are dimensioned accordingly.
Additional design parameters
Users can further refine the design using custom parameters and constraints. This includes editing the pipe parameter table or uploading custom pipe data. Adding or removing pipe diameters influences the available options, allowing prioritization of specific diameters for the design. The design criteria "pressure gradient" and "flow velocity" in the network settings provide additional manual constraints. If the calculated pressure gradient or resulting flow velocity exceeds the defined limits, the algorithm selects the next larger pipe diameter. These options enable users to implement various common design approaches in nPro.
Video tutorial on 5GDHC networks
Watch a detailed video tutorial on designing 5GDHC networks here:
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