Heat Transfer Module Updates

For users of the Heat Transfer Module, COMSOL Multiphysics® version 6.1 introduces new modeling tools for spacecraft thermal analyses, a multiphysics coupling for defining a continuity condition between shared or facing surfaces, and new tools for defining surface-to-surface radiation models. Read more about the Heat Transfer Module updates below.

Spacecraft Thermal Analysis

The new Orbital Thermal Loads interface provides ready-made features for modeling radiative loads on a spacecraft, in particular radiation from the Sun and Earth for satellites orbiting around Earth. You can use this feature to include the spacecraft radiative properties, orbit and orientation, orbital maneuvers, and planet properties. The physics interface also computes and generates results that show direct solar radiation, albedo, and planet infrared flux as well as the radiative heat transfer between the different spacecraft parts. When combining this interface with a heat transfer interface, you can account for heat conduction in the solid parts of a spacecraft. You can view this feature in the following new models:

An orbit of a satellite around an Earth model showing the magnitude of the incident solar radiation.
Orbit of a satellite around the Earth. The track color indicates whether the satellite is in eclipse or not. The spacecraft surface color represents the magnitude of the incident solar irradiation. (Earth image credit: Visible Earth and NASA)

Thermal Connectors Between Shells and Domains

The new Thermal Connection multiphysics couplings are designed to define a continuity condition between two temperature fields, computed by a domain heat transfer interface and a Heat Transfer in Shells interface, respectively. The condition can be set on a boundary shared by the two interfaces or on two boundaries facing each other. The connector can be used for shells that are in contact through an edge, a boundary shared with the domain interface, or a boundary that is facing another boundary from the domain interface. This multiphysics coupling greatly simplifies the use of combined domain and shell interfaces in models. View this feature in the existing Disk-Stack Heat Sink model and the following new tutorial models:

A circuit board model with a disk-stack heat sink in the Heat Camera color table.
Temperature field in a circuit board (domains) and in a disk-stack heat sink (shell) with a continuity condition set by the Thermal Connector feature.

Verification Tools for Surface-to-Surface Radiation Models

There are new tools available to assist with defining surface-to-surface radiation models. During the model setup, the emitted radiation direction is now represented in the Graphics window with a symbol for the Opacity controlled option and gray surface models. A warning symbol is displayed in the case of unexpected configuration. Furthermore, during the view factor evaluation, an optional verification is available to detect inconsistent topology. These tools greatly reduce the risk of erroneous definition of models, especially for large and complex geometrical configurations. View these updates in the new Topology Verification for Surface-to-Surface Radiation model and these existing models:

A purple 3D model with red arrows representing the emitted radiation direction.
Model geometry with arrows representing the emitted radiation direction. The exclamation mark (front, center) indicates a boundary where no radiation direction is defined.

Surface-to-Surface Radiation Improvements

The ray-shooting method has been improved so that small surfaces are detected even when a coarse resolution is used for the view factor evaluation. Combined with the resolution adaptation, this improves the view factor accuracy with an optimal number of rays. In addition, for all view factor computation methods, expressions used to define variables and equations are now preprocessed so that their readability is facilitated and their evaluation is much faster during the assembly step. The following models showcase these new improvements:

A beach model with a parasol and two coolers.
This model shows solar heat flux at the beach, where two styrofoam coolers contain beverage cans. A parasol provides shade for one of the coolers, and the temperature of the beverage cans is computed over time.

Fluence Rate

In the Surface-to-Surface Radiation interface, it is now possible to add a Fluence Rate Calculation node in order to select the domains where the fluence rate has to be computed. The fluence rate indicates the exposure to radiation if a small object is placed in a cavity. This is useful when you want to, for example, check the UV exposure in a water purification reactor. You can view this new feature in the Annular Ultraviolet Reactor, Transparent Water model.

An ultraviolet reactor model in the Magma color table.
Fluence rate in an ultraviolet reactor filled with quasitransparent water.

Climate Data: ASHRAE 2021

Ambient properties, such as temperature, humidity, precipitation, and solar radiation, can be defined from an Ambient Properties node under Definitions > Shared Properties. Along with the possibility of adding user-defined meteorological data, ambient variables can be computed from monthly and hourly averaged measurements from values in handbooks provided by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). The meteorological data from the ASHRAE 2021 handbook has been integrated into COMSOL Multiphysics® and contains ambient data from more than 8500 weather stations around the world.

You can view this new feature in the following existing models:

A 1D plot with a dotted blue line and solid green line.
Maximum temperatures on the hottest days of the year (blue, 2013; green, 2021) at a weather station in Glasgow, UK, show that measured temperature increased after 2013. Data from ASHRAE Weather Data.

Enhanced Thermal Wall Functions for Viscous Dissipation

In the Nonisothermal Flow coupling under its Heat Transfer Turbulence settings, a new Thermal wall function setting is available for Reynolds-averaged Navier–Stokes (RANS) turbulence models. There are two options available: Standard, which is suitable for most configurations, and High viscous dissipation at wall, which accounts for viscous dissipation in the boundary layer. This is needed for accurate results in the case of fast internal flow, especially for narrow paths or if the fluid is very viscous. The new Zero Pressure Gradient 2D Flat Plate model highlights this new feature.

A 2D plot showing the temperature profile in the Heat Camera color table and velocity direction in white arrows.
Temperature profile (surface plot) induced by viscous dissipation close to the wall and velocity direction (arrows). The green curve indicates the limit of the boundary layer (99% U_inf), and the cyan curves indicate the velocity profile at x = 0.97 m and x = 1.9 m.

User-Defined Phase Transition Function for Phase Change Material

In the Phase Change Material feature, a User-defined phase transition function is available that enables more accurate description of material properties. This option makes it possible to use accurate phase change descriptions from measured or material databases. View this update in the new Phase Change in a Semi-Infinite Soil Column - Lunardini Solution model and the following existing models:

A 1D plot with three solid lines and temperature on the y-axis.
Temperature profile in an initially frozen domain heated over time.

Additional Features for Moisture Transport in Hygroscopic Porous Media

To simplify model definitions, the Moisture Flow multiphysics coupling has been updated so that the evaporation rate variable computed by the Moisture Transport interface is accounted for in the mass balance computed by the Brinkman Equations interface. In addition, the Open Boundary and Inflow boundary conditions can now be applied to exterior boundaries adjacent to domains where the Hygroscopic Porous Medium is active.

New Tutorial Models

COMSOL Multiphysics® 6.1 brings several new tutorial models to the Heat Transfer Module.