Steady-state calculation & checking the sizing

Cold district heating, part 2: perform the steady-state calculation and verify the network sizing

Overview ▶ 0:10

Cold district heating network ready for hydraulic calculation — The fully created network as the starting point for hydraulic calculation and sizing verification

In this second tutorial, the network is calculated hydraulically and the pipe sizing is verified. The goal is to ensure that the pressure losses in the network can be handled by the installed pumps.

Adjusting the display ▶ 0:30

Visualization settings for pipe network, text color, and text scaling — Adjusting the display: pipe network size, uniform text color, and text scaling

Under Visualization, various display options can be configured:

Scale the pipe network smaller for better recognition.
Set a uniform text color.
Adjust the text scaling.

Setting up systems ▶ 0:58

Systems tab with decentralized heat pumps and energy plant — System configuration: decentralized heat pumps and creation of a new system for the energy plant

On the Systems tab, decentralized heat pumps are already assigned. For the energy plant (probe field), a new system must be created:

Select the energy plant and click Assign new system.
Create a new system in the database.
Select the geothermal probe field as the element.
Add a quadratic pressure-loss element as a second element for the manifold (e.g. 0.1 bar at 45 m³/h volume flow).
Connect the elements in series.
Assign meaningful names (e.g. “Manifold” for the pressure-loss element, “Probe field” for the overall system).

Parameterizing the geothermal probe field ▶ 2:30

Parameters of the geothermal probe field with 25 probes and 100 m depth — Configuration of the probe field: 25 probes at 100 m depth each with 32 mm pipes

For the probe field, the hydraulic consideration is done first. Probe sizing is covered in a separate video. In this example, 25 probes are configured at a depth of 100 m each with 32 mm pipes.

Performing the steady-state calculation ▶ 3:34

Steady-state calculation dialog with supply temperature and temperature difference — Steady-state calculation with specification of supply temperature, 3 Kelvin temperature difference, and decentralized pumps

Open the steady-state calculation dialog.
The supply temperature is specified for the fluid viscosity.
Set the temperature difference to 3 Kelvin.
Select decentralized pumps as the supply option.
Start the calculation.

Evaluating the results ▶ 4:02

Steady-state calculation results with pressure loss at the worst point — Calculation results: pressure loss at the worst point (0.87 bar) and detailed pressure-loss breakdown

After the calculation, the following is shown:

Pressure loss at the worst point (e.g. 0.87 bar)
Visualization of various calculation results
Via the Details button: detailed breakdown of the pressure loss (manifold, probe field, network) along with the corresponding volume flow

Checking the pump sizing ▶ 4:24

Pump sizing with operating point and pump curve — Verification of the pump sizing: operating point in the context of the pump curve

Pump sizing shows whether the stored pumps can handle the calculated pressure loss. For a cold district heating network with decentralized pumps, these are usually already built into the heat pump.

If the pressure loss exceeds the pump capacity, the sizing must be adjusted.

Optimizing the sizing ▶ 5:22

Pipe sizing with maximum pump head instead of maximum pressure loss per meter — Optimizing the sizing: switching to maximum pump head (0.75 bar) to reduce pressure loss

To reduce the pressure loss, the sizing method can be changed:

Open the pipe sizing dialog.
Switch from maximum pressure loss per pipe length to maximum pump head.
Use Shift-click to select all entries and enter the maximum head (e.g. 0.75 bar).
Run the sizing again.

Verifying the result ▶ 6:31

Optimized result with pressure loss within the limit and pump in operating range — Optimized result: pressure loss of 0.7 bar is within the limit, pump operates within its range

After running the steady-state calculation again, the maximum pressure loss should be within the limit (e.g. 0.7 bar for a limit of 0.75 bar). Pump sizing now shows that the operating point lies within the pump’s operating range.

Assigning pumps ▶ 7:18

Pump assignment in pump sizing — Assigning a pump from the database — automatically applied to all similar systems

If no pump has been assigned to a system yet, you can select an entry in pump sizing and assign the pump to the system. It will then be automatically applied to all identical systems as well.

The project is now fully prepared for simulation in the next step.