The Local Thermal Nonequilibrium Interface
The Local Thermal Nonequilibrium interface (), found in the Porous Media physics area under the Heat Transfer branch () when adding a physics interface, is used to model heat transfer by conduction and convection, in porous media for which the solid and fluid phase temperatures are not in equilibrium. A Porous Medium model is active by default on all domains, with Porous medium type set to Local thermal nonequilibrium. All functionality for including other domain types, such as a solid domain, is also available, and surface-to-ambient radiation may be considered.
The temperature equations in the solid and fluid phases of the porous medium are solved and coupled through a transfer term proportional to the temperature difference between both phases. If this difference can be neglected, use the The Heat Transfer in Porous Media Interface instead.
The physics interface is an extension of the generic Heat Transfer interface. When this physics interface is added, the following default nodes are added in the Model Builder: Porous Medium, Thermal Insulation (the default boundary condition) overridden by Local Thermal Nonequilibrium Boundary (showing all the boundaries adjacent to domains where two temperatures are solved for solid and fluid phases), and Initial Values.
Specific subnodes are also present by default under the Fluid and Porous Matrix subnodes of the Porous Medium node:
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Initial Values, which allows to set a specific initial temperature for each phase
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Thermal Insulation, which sets a no flux condition for each phase
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Continuity (under Fluid subnode only), which ensures the continuity of the temperature between the fluid phase and the other domains.
Other subnodes implementing boundary conditions specific to the fluid and solid phases may be added, to model flow conditions, heat sources, fluxes, and phase change. This can be done by right-clicking Fluid or Porous Matrix to select physics features from the context menu.
Heat Sources
In the heat source features available under the Fluid and Porous Matrix subnodes, the user input corresponds to the heat production per total unit volume. It is multiplied by the volume fraction of each phase and added into the corresponding heat equation.
Heat Fluxes
In the heat flux features available under the Fluid and Porous Matrix subnodes, the user input corresponds to the heat flux per total unit surface. It is multiplied by the volume fraction of each phase and added into the corresponding heat equation. The surface fraction is approximated by the volume fraction.
By default, the shape functions used for the temperature in porous media are Linear.
See Settings for the Heat Transfer Interface and Feature Nodes for the Heat Transfer Interface for details.
Theory for Heat Transfer in Porous Media