MembraneBasedEnthalpyExchangers fail in OpenModelica

[FWuellhorst]

Describe the bug
The models in the package MembraneBasedEnthalpyExchangers fail in OpenModelica.

Error log

 Error in model:  AixLib.Fluid.MassExchangers.MembraneBasedEnthalpyExchangers.Examples.Test_EnthalpyExchanger 
Failed to build model: AixLib.Fluid.MassExchangers.MembraneBasedEnthalpyExchangers.Examples.Test_EnthalpyExchanger
[D:/04_git/AixLib/AixLib/Fluid/MassExchangers/MembraneBasedEnthalpyExchangers/BaseClasses/Functions/CollisionIntegral.mo:10:3-10:71:writable] Error: Invalid public variable epsSteam, function variables that are not input/output must be protected.


 
 Error in model:  AixLib.Fluid.MassExchangers.MembraneBasedEnthalpyExchangers.Validation.DynamicValidation 
Failed to build model: AixLib.Fluid.MassExchangers.MembraneBasedEnthalpyExchangers.Validation.DynamicValidation
[D:/04_git/AixLib/AixLib/Fluid/MassExchangers/MembraneBasedEnthalpyExchangers/BaseClasses/Functions/CollisionIntegral.mo:10:3-10:71:writable] Error: Invalid public variable epsSteam, function variables that are not input/output must be protected.


 
 Error in model:  AixLib.Fluid.MassExchangers.MembraneBasedEnthalpyExchangers.Validation.StaticValidation 
Failed to build model: AixLib.Fluid.MassExchangers.MembraneBasedEnthalpyExchangers.Validation.StaticValidation
[D:/04_git/AixLib/AixLib/Fluid/MassExchangers/MembraneBasedEnthalpyExchangers/BaseClasses/Functions/CollisionIntegral.mo:10:3-10:71:writable] Error: Invalid public variable epsSteam, function variables that are not input/output must be protected.