Heat transfer simulation: boundary condition for heat exchange with ground

[Duo Huang]

Hi all, I'm currently working on a project involving heat transfer simulation. We want to simulate the cooling of a large steel slab sitting on the ground. I'm struggled to choose a proper boundary conditions to apply for the bottom surface of the slab which is in contact directly with ground. Both constant temperature and constant heat flux do not seem appropriate here.

I would really appreciate any suggestions.
Thank you very much for your help. Have a nice day.

 

[CarlB]

You should include the ground in your model, to some depth. At least a depth where temperature won't change much, given the time of simulation, & size of slab. Use a ground temperature at depth typical for that depth for time of year (could be 2ft to 10 ft...). Use soil thermal conductivity appropriate for soil type & moisture content.