Posted Mon, 18 May 2020 12:06:53 GMT by Henk Witte

I need to model a system with several wells, each well has an water extraction / injection regime and will have a temperature bc associated with the injection period (6 months). I need to find the resulting extraction temperature.

The final goal is to obtain extraction temperatures affected by other wells and borehole heat exchangers in the vicinity. The borehole model runs OK.

I have tried a multi-layer well with a temperature BC, but I cannot set the BC only during injection period (is that possible)?

I have also looked at the "open loop" plugin but it is not clear how to use that plugin extactly. I cannot "edit" the plugin (error message No nodal reference distribution).

Note I can only model one well of each pair as the data available from the national database only has the "warm" wells.

Posted Tue, 19 May 2020 06:32:58 GMT by Peter Schätzl Grundwassermodellierer

One option for this is the application of gaps in the time series. When there is a gap, no temperature BC will be set. The advantage of the plug-in is that it determines the injection period on its own and thus you do not need to prepare a time series with gaps for the temperature BC. There are different OpenLoop plug-ins: The one called OpenLoop Design that comes with FEFLOW nowadays does much more than what I said (or rather: something different). It can use minimum and maximum injection temperatures, and based on the energy demand of the building it will modulate the flow through the system and give a message when the demand cannot be fulfilled. There's another one called OpenLoop (or maybe SimpleOpenLoop) which takes the extraction temperature, adds a differential (defined in a time series) and uses the result as injection temperature. Each of the plug-ins has a help file that can be accessed via the help entry in the context menu of the plug-in in the corresponding panel. There you can see why it doesn't come up in your case.
Posted Tue, 19 May 2020 08:01:03 GMT by Henk Witte
Thank you!

Two further questions:

1) with the "gap"method I assume you introduce one multilayer well BC with flow rate (inject/extract) and one temperature BC with the "gapped" temperature BC. Do you then apply that temperature BC only to the node in the top slice of the multilayer well?

2) with the openloop I can open the help but not edit or assign anything. What I did not see in the help file is how to select the nodes/edges (?) where to apply the plugin to, but perhaps I miss something in how to apply plugins (sorry - steep learning curve and little time due to project deadlines).

Henk Witte
Posted Tue, 19 May 2020 08:07:23 GMT by Peter Schätzl Grundwassermodellierer
1) You apply the temp BC to the bottom node of the MLW (FEFLOW internally sets the well BC at the bottom node, with a discrete feature above)
2) For OpenLoop Design, the help says what I've put below; OpenLoop I do not have (as I'm no longer with DHI), and I don't recall exactly what it needs (though I coded it a long time ago...):

"3. A nodal distribution in User Data with the name 'OpenLoop' is created to identify participating nodes.In that reference distribution, all nodes belonging to a specific group (injection and extraction nodes) are assigned the same integer value. All other nodes should have values less than or equal to 0. In case of using multilayer wells, only the bottom nodes of the multilayer wells should be included in the distribution. Be careful with mesh refinement: In case of refining the mesh after assigning the power function number, the data interpolation will lead to a number of nodes with non-zero values around the wells, too.

4. A second nodal distribution in User Data with the name 'OpenLoopPortion' is to be created to define the portions of injection/extraction on the nodes belonging to a system. The integer reference value represents the number of the time-series to be used as the portion function for the well at this location. The same time-series ID may be used for more than one well. The values in the time series are expected to be between 0 and 1, and typically would add up to 1 when summing over all extraction or injection nodes of a system (unless water is discharged elsewhere). All other nodes are to be given zero or negative values. "
Posted Tue, 19 May 2020 08:23:24 GMT by Henk Witte
Thanks for the fast reply!

Henk Witte

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