Heat Transfer Module Updates

For users of the Heat Transfer Module, COMSOL Multiphysics® version 5.6 includes directional dependent surface properties for surface-to-surface radiation, a new Porous Medium feature, and a Phase Change Interface boundary condition. Read about these heat transfer features and more below.

Phase Change Interface Boundary Condition

The new Phase Change Interface boundary condition, combined with the Deformed Geometry feature, defines the interface between two domains corresponding to two different phases. This boundary condition is based on the Stefan condition; it sets the phase change temperature, defines the front velocity from the latent heat of phase change, and specifies the solid side and heat flux jump evaluation. This boundary condition models the phase transformation as a sharp interface and can be used for a number of applications, including pure metal melting, as seen in the Tin Melting Front model, or solidification or sublimation, as seen in the Freeze-Drying model.

Simulation results for freeze-drying, with the solid and vapor shown to the left and temperature and total heat fluxes shown on the right in the heat camera color table. Freeze-drying model Gas and solid phases (left), and phase change interface, temperature, and total heat flux streamlines (right).

Heat and Moisture Transport in Porous Media

There are new interfaces and features for modeling coupled heat and moisture transport in porous media filled with moist air and liquid water. The new Moisture Transport in Porous Media interface provides a Hygroscopic Porous Medium feature by default, and can be used to model moisture transport in porous media by vapor convection and diffusion, as well as liquid water convection and capillary flow. The new interface accounts for convection in both liquid and gas phases due to total pressure variations, by modeling the liquid capillary flux, and by adding support for gravity forces. It can be combined with the Moist Air feature to model the effect of a moist air flow on a porous medium.

In the Heat Transfer interface, the new Moist Porous Medium domain feature defines effective material properties from the solid, liquid water, and moist air properties individually. The Moist Air subnode defines the material properties by taking into account the moisture content, and computes the convective flux and diffusive enthalpy flux in moist air. The Liquid Water subnode defines the liquid water saturation and velocity field, which may be automatically set by the Heat and Moisture multiphysics coupling, if available. The solid properties are handled by the Porous Matrix subnode. These new functionalities can be used for drying and evaporative cooling applications.

A sample is shown as a rectangle in 2D with streamlines visualizing the airflow and vapor concentration shown in a rainbow color table. Moist sample exposed to dry, warm airflow Concentration of vapor and total flux streamlines in a moist sample exposed to a dry and warm airflow. In COMSOL Multiphysics® version 5.6, the model setup is facilitated by the new features for heat and moisture transport in porous media.

New Porous Medium Feature

A new feature for handling a porous medium is available for defining the different phases: solids, fluids, and immobile fluids. In the Heat Transfer in Porous Media interface, the Porous Medium feature is used to manage the material structure with a dedicated subfeature for each phase: Fluid, Porous Matrix, and optionally, Immobile Fluids. This new workflow provides added clarity and improves the user experience. It also facilitates multiphysics couplings in porous media in a more natural way. Combined with the Moisture Transport and Porous Media Flow interfaces, the heat transfer in porous media improvements enable the modeling of nonisothermal flow and latent heat storage in porous media.

You can see this new setup in the following models:

The Porous Medium feature settings in COMSOL Multiphysics version 5.6 with the Effective conductivity options shown and Reciprocal average highlighted. The settings for the Porous Medium feature A porous material with a fluid, a solid, and an immobile fluid combined with the Porous Medium feature in the Heat Transfer in Porous Media interface. The Settings window shows the selection of the model defining the effective thermal conductivity from the different phases in the porous medium.

Directional Dependent Surface Properties for Surface-to-Surface Radiation

In the Surface-to-Surface Radiation interface, when the ray shooting method is selected, you can now define surface properties that depend on the radiation incidence angle. This is available in the Opaque Surface and Semitransparent Surface features for the surface emissivity, reflectivity, and transmittivity. This is useful for simulating surfaces that have a texture or pattern that is absorbing, reflecting, and transmitting heat radiation differently in different directions.

The COMSOL Multiphysics 5.6 UI with the Opaque Surface feature settings shown and a function plot for a directional dependent surface properties model to the right. Demonstrating the Opaque Surface feature The Opaque Surface feature defining directional dependent emissivity from the directionalEmissivity function (highlighted) under the Definitions node and the corresponding function plot in the Graphics window.

Semitransparent Surface for Radiation in Participating Media

The new Semitransparent Surface feature is available in the Radiation in Participating Media interface. On exterior boundaries, you can specify an external radiation intensity and account for the part of this incoming intensity that is diffusively or specularly transmitted through the surface. On interior boundaries, the radiation intensities on both sides of the surface are considered. This boundary condition is especially useful for modeling incident radiation coming from a transparent media on a participating media sample. This is the case for modeling the characterization of radiative properties of participating media, for example. You can see this feature demonstrated in the Radiative Cooling of a Glass Plate with Semitransparent Surfaces model.

The settings for the Semitransparent Surface boundary condition in the Radiation in Participating Media interface in COMSOL Multiphysics version 5.6. The settings for the Semitransparent Surface boundary condition The user interface for the Semitransparent Surface boundary condition in the Radiation in Participating Media interface provides user inputs to define the surface transmissivity on both sides of the boundary and the exterior radiation intensity that is used for external boundaries.

Thermal Contact and Symmetry for Layered Material

New functionalities extend the modeling capabilities for layered materials. The new Thermal Contact, Interface feature allows you to represent the surface asperities and the gap at the internal interfaces between the layers of a layered shell that are responsible for thermal resistance between the layer. This is needed to model the effect of delamination on thermal performances, as demonstrated in the Thermal Expansion of a Laminated Composite Shell with Thermal Contact, Interface model. Additionally, a Symmetry feature, introduced in the Heat Transfer in Shells interface, allows you to set symmetry conditions on edges to reduce the size of symmetric models.

The COMSOL Multiphysics 5.6 UI with the Thermal Contact Interface feature settings shown and a preview of a square model's two layers to the right. Demonstrating the Thermal Contact and Symmetry features Model containing a two-layer material with a thermal resistance between them represented on the layer layout preview (right). The Settings window provides the inputs to define the thermal contact properties through conduction and radiation. The model geometry size has been reduced thanks to the Symmetry condition present in the model tree.

Automatic Detection of Ideal Gas Material in Heat Transfer in Fluids

The Fluid feature, available within the various heat transfer interfaces, has been updated to take advantage of the ideal gas assumption to improve computational efficiency. The new From material option of the Fluid type list automatically detects whether the material applied on each domain selection is an ideal gas or not, and uses the relevant properties for either case. This may speed up computation when computing pressure work in compressible nonisothermal flows, for example. Since the gases available in COMSOL Multiphysics® and in the Material Library are modeled as ideal gases, many models with compressible nonisothermal flow are expected to benefit from this improvement.

A model of an LED bulb visualizing the velocity around the bulb in a color gradient from dark blue to white and the temperature in the bulb using the heat camera color table. An LED bulb model that uses automatic detection of the ideal gas formulation Temperature distribution (surface plot) and velocity (arrows and streamlines) in an LED bulb. By using the ideal gas formulation automatically, the computational time is 10% shorter in COMSOL Multiphysics® version 5.6.

Heat and Energy Balance

The postprocessing variables for energy and heat balance definition have been extended to cover new configurations. Specifically, the variables are for nonisothermal flow, to account for out-of-plane heat sources; for the work of volume forces, viscous dissipation, and pressure; for boundary stresses; and for enthalpy flux in cases of nonzero normal velocity on internal walls. The postprocessing variables or energy and heat balance definition have also been extended to layered materials. Energy and heat balance provide an alternative criterion to the solver error estimate to check the simulation accuracy. You can see this functionality demonstrated in the Electronic Chip Cooling model.

The COMSOL Multiphysics 5.6 UI with the Global Evaluation settings shown for a cross-flow heat exchanger model, which is shown in the Graphics window in a color gradient from dark red to white to indicate temperature in degrees Kelvin. Demonstrating the postprocessing variables for heat and energy balance Verification of the energy balance in the cross-flow heat exchanger model. The total net energy rate entering at the hot inlet is compared with the energy balance for the entire model.

New and Updated Tutorial Models and Applications

COMSOL Multiphysics® version 5.6 brings new and updated models and applications to the Heat Transfer Module.

Freeze Drying

Simulation results for freeze-drying, with the solid and vapor shown to the left and temperature and total heat fluxes shown on the right in the heat camera color table. Freeze-drying model Gas and solid phases (left), and phase change interface, temperature, and total heat flux streamlines (right).

Application Library Title:
freeze_drying
Download from the Application Gallery

Radiative Cooling of a Glass Plate with Semitransparent Surfaces

A circular glass plate model with the temperature in degrees Kelvin shown in a color gradient from dark red to white; the plate is mostly light yellow. Glass plate with semitransparent surfaces model Temperature in a glass plate with semitransparent surfaces after cooling for 10 seconds.

Application Library Title:
glass_plate_semitransparent_surface
Download from the Application Gallery

Tin Melting Front

A 2D model showing the temperature in degrees Kelvin, visualized in dark red to white, and arrows for the velocity field. Tin melting front model The Tin Melting Front tutorial model has been updated with the use of the new Phase Change Interface feature to capture the phase change front.

Application Library Title:
tin_melting_front
Download from the Application Gallery

Evaporation in Porous Media with Large Evaporation Rates

A sample is shown as a rectangle in 2D with streamlines visualizing the airflow and vapor concentration shown in a rainbow color table. Evaporation in porous media model The Evaporation in Porous Media with Large Evaporation Rates tutorial model has been updated with the use of the new Moisture Transport in Porous Media interface to model the transport of vapor and liquid water through the porous medium.

Application Library Title:
evaporation_porous_media_large_rate
Download from the Application Gallery

Inline Induction Heater

A simulation app for designing an inline induction heater, with fields for geometry, materials, and operating condition inputs on the left and the simulation results on the right. Inline induction heater app The Inline Induction Heater application now uses boundary layer meshes on faces.

Application Library Title:
inline_induction_heater
Download from the Application Gallery