COMSOL Multiphysics^® 6.1 Release Highlights

Fuel Cell & Electrolyzer Module Updates

For users of the Fuel Cell & Electrolyzer Module, COMSOL Multiphysics^® version 6.1 provides the ability to add auxiliary species, improved default solvers and stabilization for 3D models, and improvements to the Continuity condition for assembly geometries with identity pairs.

Auxiliary Species in the Hydrogen Fuel Cell and Water Electrolyzer Interfaces

It is now possible to add and arbitrarily define one additional auxiliary species in hydrogen and oxygen gas mixtures in the Hydrogen Fuel Cell and Water Electrolyzer interfaces. This allows for more flexible modeling of systems containing, for example, trace impurities, sulfuric compounds, heavy hydrocarbons, and ammonia.

The Settings window for defining the gas mixtures in the Hydrogen Fuel Cell and Water Electrolyzer interfaces.

Improved Default Solvers and Stabilization in the Hydrogen Fuel Cell and Water Electrolyzer Interfaces

The default solver generation for 3D models using the Hydrogen Fuel Cell and Water Electrolyzer interfaces has been significantly improved, with the generated default solver depending on the physics settings and the number of degrees of freedom. For large problems, algebraic multigrid iterative solvers are now generated by default, which reduces memory usage and computational time considerably. In addition, stabilization of the convective terms in the gas phase transport equations has been added to the Hydrogen Fuel Cell and Water Electrolyzer interfaces. The added stabilization makes it possible to solve fuel cell and electrolyzer models with coarser meshes, which is typically needed when working with larger geometries.

Resulting water-relative humidity levels in the Low Temperature PEM Fuel Cell with Serpentine Flow Field model, where the flow field plate width has been increased to 50 mm, the number of channels has been increased to 10, and the number of repeating "U" units has been increased to three. Larger model geometries of this kind benefit from the default solver and stabilization improvements.

Improved Continuity Condition on Assembly Pair Boundaries

Assembly pairs are typically used when nonmatching mesh elements are used on each side of a boundary. The need for using assembly pairs may arise when using, for instance, swept meshes in complex 3D geometries. In version 6.1, the Continuity boundary condition for potential dependent variables (for both the electrode and electrolyte phases) of assembly pair boundaries has been significantly improved in terms of accuracy and numerical stability in the Current Distribution interfaces.

Nonideal Species Activity Coefficients

Version 6.1 introduces functionality for modeling nonideal electrolytes using Debye–Hückel theory. In such electrolytes, even a small variation in concentration — in the millimolar range — may cause measurable changes in quantities such as pH and electrode equilibrium potential. The ability to account for nonideal effects in modeling and simulation is therefore an important addition to the electrochemistry interfaces. In this version, it is now possible to include these effects in the Tertiary Current Distribution, Nernst-Planck and Transport of Diluted Species interfaces. The activity coefficients may be defined using either the Debye-Hückel species activity or user-defined expressions.

Selecting the nonideal Debye-Hückel species activities. The setting is found in the nodes of the Tertiary Current Distribution, Nernst-Planck interface and the Transport of Diluted Species interface.

Advanced Chemical Formulas

It is now possible to use more advanced formulas for chemical species and chemical reactions. The enclosing marks (),[], and {} can be used to indicate structural units in the molecular formula in a coordination complex, for example. To improve readability, simplified names can be used in the reaction formula to indicate an entire species or a part of the molecular structure. When reaction balancing is performed, the complete composition and charge is considered.

Improved Performance of Property Evaluations

The enhanced performance of property evaluations is noticeable in all property computations, such as density and viscosity, as well as for thermodynamic properties like heat capacity and vapor pressure. Models where a significant part of the solution time is spent performing property evaluations can now be solved in as much as 30% less time.

Improved Functionality for Adding Species to a System

The functionality to search for species in the database and add them to a model has been extended and improved. The species filtered from a search can now be added one at a time using the Enter key. In addition, it is no longer necessary to reset the filter result when a species has been added.

New Tutorial Model

COMSOL Multiphysics^® version 6.1 brings one new tutorial model to the Fuel Cell & Electrolyzer Module.

Fuel Cell Stack Cooling

Oxygen mole fraction (streamlines) and hydrogen mole fraction (surface) in a proton exchange membrane (PEM) fuel cell stack.

Application Library Title:

stack_cooling

Download from the Application Gallery