The company has internal recruitment, which happens to be the department I want to go to most. If I tell my department head,

You still have to pay attention to strategy when doing things.

I don't know the relationship between the recruitment process and departments in your company, but one thing I am sure of is that you can't talk to your supervisor directly. What will you do to your supervisor in case you are not hired in the end? You will inevitably leave him with the impression that he is not at ease with his work. Will he trust you in the future? Will it train you? Perhaps, if you lose your wife and fold your soldiers, you will fail at both ends.

You can't get it, but you can't lose it again. The safe way is to go to the human resources manager privately to express your intention first. He is the last employing department. If anyone is interested in this position, he will certainly welcome it. In the process of contact, you can observe his attitude towards you, so that you can also judge your chances of winning a successful competition. At the same time, you can tell him your doubts directly, because he is from the human resources department, and he will not ignore this kind of problem. It is also the responsibility of the human resources department to solve this problem, and he will give you guidance. Perhaps, your company has a clear internal recruitment registration and competition process, but you just don't know it. In short, you must rely on the human resources department to solve this problem.