Backward Compatibility with Version 4.4

Out-of-plane Heat Transfer update

The out-of-plane heat transfer property, which was available in 2D and 1D geometries, has been removed as of COMSOL Multiphysics 5.0. Now, all geometries are considered 3D geometries and thickness or area parameters are always available.

API Users

With the Overall heat transfer rate option (previously named Total power or Total heat flux), the thickness parameters (dz_entr and Ac_input) have been removed for the following features:

•	Heat Source

•

Heat Flux

•	Boundary Heat Source

•	Layer Heat Source

•	Inflow Heat Flux

Compatibility with previous code is maintained for most of the cases. However, three configurations require manual updates of the code:

•	If you specified the thickness parameter twice (there were two instances of specifying the parameter).

•	If you first specified the thickness and in a second command the total power value.

•	If you first specified the thickness and then activated the out-of-plane heat transfer option.

For these 3 cases, you need to rewrite this part of the Java® code by doing the following. For a heat source example (2D and 1D axisymmetric geometries):
Ptot_50 = Ptot_44_value*ht.d/dz_entr_44_value,
where Ptot_44_value is the total power value used in previous versions, Ptot_50 is the total power value used since COMSOL Multiphysics 5.0, and dz_entr_44_value is the value used in previous versions.

In 1D geometries, the following update should be performed: Ptot_50 = Ptot_44_value*ht.d/Ac_input_44_value ,
where Ac_input_44_value is the value used in previous versions.

Flux Variables

The flux variables are always given in W/m² (also for 2D or 1D geometries). To obtain the corresponding flux variables in W/m on a boundary in 2D, for example, the flux variables have to be multiplied by the thickness ht.d.

The following variables have been updated following this convention:

•	Conductive heat flux, ht.dflux

•	Convective heat flux , ht.cflux

•	Translational heat flux, ht.trlflux

•	Total energy flux, ht.teflux

•	Total heat flux, ht.tflux

•	Boundary convective heat flux, ht.chflux

•	Radiative heat flux, ht.rflux

All flux variables now have the following sign convention: positive heat flux corresponds to heating, whereas negative heat flux corresponds to cooling. The variables chflux and rflux may have opposite signs compared to previous versions, depending on the context where they are defined.

Inflow Heat Flux is only applicable on non-solid domains

The Inflow Heat Flux feature is no longer applicable on boundaries adjacent to the following domain features: Heat Transfer in Solids, Biological Tissue, and Isothermal Domain. This restriction avoids ill-posed configurations due to the null velocity field in these features. This may change model results if this boundary condition was previously applied to a boundary adjacent to a nonfluid domain.

Heat Transfer with Phase Change Now Uses a Volumetric Formulation

The variables ht.thetai now represent volume fractions (they were mass fractions before). This implies changes in the definition of density and heat capacity at constant pressure close to the phase change interface. Far from the phase change interface, the density and heat capacity are unchanged.