Coupling of Heat Transfer to Electrochemical Reactions
Irreversible voltage losses in an electrochemical cell can occur due to the following phenomena:
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Charge transport in the electrolyte (Joule heating)
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Charge transport in the solid conductor materials (Joule heating)
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Activation overpotentials in the electrode reactions
In addition, reversible heat sources and sinks can appear due to the entropy changes in the electrode reactions. How these heat sources are defined are described at the end of this chapter.
Most Electrochemistry interfaces define and announce heat source variables that for instance can be used by the General Source and the Boundary Heat source nodes in the Heat Transfer interfaces.
An alternative way to couple an electrochemical interface to a heat transfer interface is by the use of the Multiphysics nodes that become available in the model builder tree if there is both a Heat Transfer interface and an Electrochemistry interface available in the same component.
The Electrochemical Heating multiphysics node defines a domain heat source in the heat transfer interface, based on the sum of irreversible (Joule heating and activation losses) and reversible heat in the electrochemistry interface.
The Temperature Coupling node can be used to set the temperature in the electrochemistry interface to equal the temperature dependent variable in the heat transfer interface.
You can also use the heat source variables defined by the electrochemistry interfaces when setting up manual heat couplings between different components in a model. For instance if you are using a 1D electrochemical cell model to calculate an average heat source in a 3D heat transfer model. The names of the heat source variables are xxx.Qh (domain, Joule heating and porous electrode reactions) and xxx.Qbfc (boundary, electrode surface reactions), where xxx is the electrochemistry interface identifier.
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Electrochemistry Interfaces
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Multiphysics Coupling Nodes