Heat conductivity constitutive law

I was looking on the white papers and I saw that constitutive laws can be implemented in FEFLOW for viscosity, density etc. and also for parameters like heat conductivity.
I am very interested in this possibility, because it can be useful for modelling, i.e., groundwater filled borehole heat exchangers in which water can become ice and hence heat conductivity can be greatly enhanced (from 0.59 to 2.2 W/(mK)!!!).
Is it possibile, and if, how?
Thank you for your attention.

While the relationships for viscosity and density are built-in ones in FEFLOW (with some modifications possible), the thermal conductivities are material properties and not subject to consitutive relationships based on temperature.  Thus (currently) the only way of implementing such dependencies is the open programming interface IFM, writing user-specific code.

I found that the IFM module "lambdat.dll" is able at varying the thermal conductivity according to the node temperature, using the Zoth and Hänel (1988) formula...

Yes - that's true - I had forgotten about this module. The plug-in is currently not listed on the plug-ins web page (http://www.feflow.info/62.html), but that will be fixed soon.

Hi! Does this plug-in work for FeFlow 6.2? If so, what do I need to do after I attach it and activate it? Nothing seems to happen after I do that and I'm therefore wondering how it works...
Thank you for any help!
Regards
Zeno

Hi Zeno, yes the plugin works for FEFLOW 6.2. The plugin uses callback functions related with the simulation. Accordingly, you only have to attach the plugin to the fem-problem and run the simulation. You may even check the impact of varying the thermal conductivity according to temperatures. Run the exactly the same model two times, one time with and one time without the plugin.