This model considers the conduction heat transfer between the buried pipe wall and the undisturbed ground temperature by adding a dynamic ground layer. The dynamic ground layer is modeled using the radial heat conduction model through a hollow cylinder Buildings.HeatTransfer.Conduction.SingleLayerCylinder. The undisturbed ground temperature is calculated by the model Buildings.BoundaryConditions.GroundTemperature.UndisturbedSoilTemperature. This model can consider an axial discretization of the pipe. A figure highlighting the main variables and parameters is shown below:
Ettore Zanetti, David Blum, Michael Wetter (2023) Control development and sizing analysis for a 5th generation district heating and cooling network using Modelica, In Proceedings of the 15th International Modelica Conference. Aachen, Germany, Oct 9-11, 2023.