This subnode should be used to model the heat transfer due to hydrodynamic mixing in a fluid flowing through a porous medium. It adds an extra term ∇ ⋅ (kdisp∇T) to the right-hand side of the heat equation in porous media, through the modification of the effective thermal conductivity keff with the dispersive thermal conductivity kdisp:

This section sets the Longitudinal dispersivity λlo and Transverse dispersivity λtr used for the definition of the tensor of dispersive thermal conductivity:

where Dij is the dispersion tensor

and λijkl is the fourth-order dispersivity tensor

If the Extended porous matrix model is selected under Physical Model (with the Subsurface Flow Module), the Transverse horizontal dispersivity λtr, h and Transverse vertical dispersivity λtr, v are defined instead of the Transverse dispersivity λtr.

In this case it is assumed that z is the vertical direction and it defines the dispersion tensor as

More locations are available if the Heat transfer in porous media check box is selected under the Physical Model section. For example:
Heat Transfer in Solids>Porous Medium>Thermal Dispersion

Physics Tab with Porous Medium selected in the model tree:
Attributes>Thermal Dispersion