Selecting the Right Physics Interface
The Heat Transfer branch () included with this module has a number of physics interfaces that can be used to model energy transport. One or more of these can be added; either by themselves or together with other physics interfaces, typically flow physics interfaces.
While the standard COMSOL Multiphysics package includes physics interfaces for simulating heat transfer through conduction and convection, this module provides extra functionality within the standard Heat Transfer interfaces. The CFD Module also includes additional Heat Transfer interfaces such as The Heat Transfer in Porous Media Interface.
For heat transfer in single-phase flows, the CFD Module provides the Nonisothermal Flow () (located under the Fluid Flow branch) and Conjugate Heat Transfer () (located under the Heat Transfer branch) interfaces. There are several versions of these interfaces that combine heat transfer with either laminar or turbulent flow. The multiphysics interfaces automatically couple the flow and heat equations and they also provide functionality, such as support for turbulent heat transfer, that is not readily available when adding the interfaces separately.
Heat Transfer in Solids or Fluids, and Joule Heating
The Heat Transfer in Solids (), Heat Transfer in Fluids () (general convection and conduction), and Electromagnetic Heating>Joule Heating interfaces (), all belong to the COMSOL Multiphysics base package.
Heat Transfer in Porous media
The Heat Transfer in Porous Media interface () is an extension of a the generic heat transfer interface that includes modeling heat transfer through convection, conduction and radiation, conjugate heat transfer, and nonisothermal flow. The ability to define material properties, boundary conditions, and more for porous media heat transfer is also activated by selecting the Heat transfer in porous media check box on any heat transfer interface.
Nonisothermal Flow and Conjugate Heat Transfer
The Nonisothermal Flow () and Conjugate Heat Transfer () interfaces solve the Navier-Stokes equations together with an energy balance. They can also solve for heat transfer in solids.
Nonisothermal Flow and Conjugate Heat Transfer differ by their default features. The default heat transfer domain feature for Nonisothermal Flow is a Heat Transfer in Fluids node while Conjugate Heat Transfer has a Heat Transfer in Solids node as its default domain feature.
The Laminar Flow versions of the physics interfaces are used primarily to model slowly flowing fluids in environments where energy transport is also an important part of the system and application, and must be coupled or connected to the fluid flow in some way. Stokes’ law (creeping flow) can be activated from the Nonisothermal Flow, Laminar Flow and Conjugate Heat Transfer, Laminar Flow interfaces if wanted. If you expect the flow to become turbulent, select one of the versions of the turbulent flow interfaces. Each physics interface includes a RANS turbulence model to calculate the turbulence and algebraic models for the turbulent Prandtl number.
The Nonisothermal Flow and Conjugate Heat Transfer interfaces can solve the fully compressible form of the Navier-Stokes equations. But boundary conditions and stabilizations are provided for Mach numbers less than 0.3. If you expect the Mach number in your model to become higher than 0.3, use The High Mach Number Flow Interfaces.
 
Theory for the Heat Transfer Module in the Heat Transfer Module User’s Guide
The Joule Heating Interface in the COMSOL Multiphysics Reference Manual