BHE Interconnection Editor

The BHE Interconnection Editor allows the definition of BHE arrays with parallel or serial interconnection of the single borehole heat exchangers. It is called as a tool from the Borehole-heat exchanger toolbar. Due to the implementation as a tool all other FEFLOW functions can be used while the dialog is open. This is especially important to visualize the connections set in the dialog but not applied yet in the Slice or 3D view. Unlike other dialogs, the BHE Interconnection Editor is not closed by an OK button, but by simply closing the window using its close button in the upper right corner (after hitting Apply to make the changes known to the model) or by switching to another tool in one of the toolbars. In case of using the window corner for closing the dialog, it might be necessary to switch back to the standard Pan tool in the View toolbar after using the BHE Interconnection Editor.

Each array is equipped with inflow and outflow, and the inflow carries a flow rate and an inlet temperature or heat input rate. As for a single BHE, these values defining the inflow can be time-constant or time-varying.

When branching into a number of connections from one BHE or from the input the flow is equally distributed according to the number of pipes.

BHE Arrays

By default, this list contains a single array, i.e., one inflow and one outflow pipe for the system. With the plus and x buttons, additional arrays can be created or existing arrays deleted.

 

Index	Internal index of the array
Name	User-defined array name
Flow Rate	Total flow-rate through the array, positive from inflow to outflow
Input Type	Inlet temperature or Heat-input rate as discussed in the reference for the Borehole-heat Exchanger dialog.
Input Value	Inlet temperature or heat-input rate value or time series

 

The input data Flow Rate and Input Value can be defined by a constant value or a reference to a time-series previously input in the Time-series dialog. The input mode is changed by a left-click on the icon showing up when double-clicking on the respective value in the list.

BHE Interconnection

In the interconnection section, the parallel or serial links between the single BHEs are defined. A chart provides quick graphical output to check the settings. At the same time, the connections and selected inlet/outlet points and BHEs are shown in the active Slice view.

The elements of the array can be linked to each other by drag-and-drop or by using the context menu on each of the elements in the Use Output of and Link to Input at tables.

The preview of the links on the right-hand side shows the logical connections without a geographic reference. All elements (connection points and BHEs) can be moved by drag-and-drop. Their default positions (also not related to their geographical location) can be restored by pressing the Restore default positions for current BHE array layout button on the upper right.

 

FEFLOW does not support interconnections between different arrays, i.e., borehole heat exchangers being part of more than one BHE array. If such systems are defined, the Validate function will return an error in the setup. If Validate is not run or the system is not corrected after the check, FEFLOW will report an error at simulation start.

Validate

All defined connections can be checked by clicking on Validate. The validation detects checks for the correct sum of flows at each BHE and tests for loops in the system.

Revert and Apply

By clicking on Revert, the link status of the last Apply action is restored. Apply applies the current link status to the model.