Get term from tid in views
Do you use "Content: Has taxonomy term ID" field as contextual filter? 

If yes then edit this filter, in "WHEN THE FILTER VALUE IS IN THE URL OR A DEFAULT IS PROVIDED" section check "Override title" and in appeared textfeild input "Department: %1"

"%1" will be replaced by the name of current term. If no term is specified "%1" will be replaced by "all".

If you want change word "all" then in section "WHEN THE FILTER VALUE IS NOT IN THE URL" click on "Exceptions", check "Override title" and specify your value.