A long and slender shaft of diameter 2R and length L 1 + L 2 is insulated over length L 1 and…

A long and slender shaft of diameter 2R and length L1
+ L2 is insulated over length L1 and produces heat only
in this section while over length L2, it is exposed to a convection
boundary (h, Tf). Write the governing differential equations and the
associated boundary conditions from which temperatures in sections L1
and L2 can be obtained. Both ends may be treated as adiabatic
surfaces.