Hello Abderezakabidi,

If what you refer to as 'functions' are really Modelica functions (and not models) then you need to pass the global parameters as arguments to the function.

If you simply need to share information across various components/systems (like an ambient temperature) then you can declare this "global variable" in the model containing your instatiated components/subsystems. See for example how Modelica.Fluid.System is used.

I recommend you take a look at Mike Tillers online Modelica book: https://mbe.modelica.university/

Best regards,
Rene Just Nielsen