Simulate an active network with a central pump

Cold district heating, part 5: simulation of an active network with a central circulation pump

Overview

This part shows how a passive network with decentralized circulation pumps is converted into an active network with a central pump. The conversion is done in just a few steps.

Swapping the plants

Replacing the decentralized heat pump with pump by a variant with a valve
Replacing the decentralized heat pump: from the variant with a pump to the variant with a valve

Starting from the previous example with decentralized heat pumps and circulation pumps:

  1. Select the decentralized heat pump with pump.
  2. Click Replace.
  3. Select a decentralized heat pump with valve from the database.
  4. Copy the element so that it can be edited.
  5. Repeat the procedure for all other plant types.

Structure of the new plant

Plant editor with heat pump and valve instead of circulation pump
New plant: heat pump with valve (instead of circulation pump) to regulate on a 3 Kelvin temperature difference

The new plant consists of:

  • Heat pump with the corresponding pressure loss
  • Valve (instead of the circulation pump), which regulates on a fixed temperature difference of 3 Kelvin

The consumer side is now passive — no decentralized pump is required any more.

Installing the central pump

The network still needs a circulation pump, which is now placed centrally in the borehole field:

  1. Open the borehole field in the plant editor.
  2. Delete the existing connection line.
  3. Drag a pump with defined head into the plant.
  4. Connect the elements.
  5. Confirm with OK.

The network has now been converted into an active system.

Performing the steady-state calculation

  1. Open the steady-state calculation dialog.
  2. For the supply, select a central pump instead of decentralized pumps.
  3. Start the calculation.

The pressure loss at the worst point should hardly differ from the passive system, since only the pump has been swapped.

Pump sizing

Pump sizing with system curve and pump selection from the database
Pump sizing: system curve and selection of a suitable pump from the database
  1. Click Details > Pump sizing.
  2. The system curve is displayed.
  3. Select a suitable pump from the database.
  4. Click Assign pump.

The pump is stored in the plant with the corresponding curve and head.

Running the simulation

  1. Switch to the simulation.
  2. Set the simulation time (e.g. 14 days for a quick check).
  3. Start the simulation.

Evaluating the results

Results with temperature difference at the consumers and pump diagram
Results: temperature difference at the consumers and pump diagram with constant pressure increase (0.8 bar)

In results mode, check in particular:

  • Temperature difference at the consumers: The configured 3 Kelvin should be reached. If not, the pump must be re-sized or the pressure increase adjusted.
  • Pump diagram: The central pump runs with a constant pressure increase (e.g. 0.8 bar).

The system has now been successfully converted into an active network with a central pump.

Video tutorial

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