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Geothermal Heating
Use this subnode under a Porous Medium node to take into account the contribution of geothermal heat production by adding a source term Qgeo to the right-hand side of the heat equation:
The predefined expression of the heat source uses the Geothermal Density, the Radiogenic heating per unit mass, and a distribution function that can be set.
Geothermal Heat Production
Specify the Radiogenic heating per unit mass qgeo.
The two option buttons in the same group control the distribution function f(zgeo):
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If  Uniform distribution is selected, f(zgeo) = 1 and the geothermal heat source is assumed to be independent on depth.
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If  Exponential distribution is selected, two additional input fields are displayed underneath. The exponential distribution f(zgeo) = exp(zgeo ⁄ hgeo), is defined by the constant Length scale: hgeo and the variable Depth zgeo. The depth can be, for example, the vertical coordinate direction. The heat source achieves its maximum value where zgeo = 0, typically the top surface of a model.
Geothermal Density
Select the Geothermal density: Solids, Porous media, or User defined:
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If  Solids is selected, it calculates the geothermal density based on the volume fraction of solid material
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 If Porous media is selected, it calculates the geothermal density based on all mobile and immobile components of the porous medium:
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 If User defined is selected, enter a value for the Geothermal density ρgeo.
The Geothermal Heating subnode requires the Subsurface Flow Module. For a detailed overview of the functionality available in each product, visit https://www.comsol.com/products/specifications/
Location in User Interface
Context Menus
Heat Transfer in Porous Media>Porous Medium>Geothermal Heating
Ribbon
Physics Tab with Porous Medium selected in the model tree:
Attributes>Geothermal Heating