Double pipe heat exchanger
 

Please help
I have a project at the university, a project is required of me ( double pipe heat exchanger)
( 4 regions ,, external pipe - internal pipe - hot fluid - cold fluid )
On openfoam


I finished the project but I get an error


I hope to find someone who has the same project ready, and put it for me in the comments so that I can learn from it

Thank you

The error
 

This is the error