  We consider two common heat transfer processes and perform a through
sensitivity study of the variables involved. We derive and discuss analytical
formulas for the heat transfer coefficient in function of film velocity, air
temperature and pipe diameter. The according plots relate to a qualitative
analysis of the multi-variable function $h$, according to functional
optimization. For each process, we provide with graphs and tables of the
parameters of interest, such as the Reynolds number. This method of study and
the specific values can constitute a useful reference for didactic purposes.
