heat transfer along a pipe
 

hello, everyone, I want to get some advice on a problem of turbulent transfer along a pipe. The pic of the problem is attached here. I want to do the simulation of heat transfer from inside to outside along the pipe but don't know how to set the boundary conditions.

1. in most cases, the inlet velocity, inlet temperature, the materials, thickness, heat conduction coefficient, ambient temperature can be known.
the outlet velocity, temperature, inside and outside surface heat convection coefficient should be calculated.

2. in the theoretical calculation, assume the outlet temperature, and use the parameter of average temperature of inlet of outlet, do the interation. The heat convection coefficient along the pipe is thought as constant.
but actually, the heat convection coefficient changes along the pipe.

3. for the simulation of fluent, how to set the boundary conditons can get the accurate result?
inlet--> velocity and temperature
outlet--> use the default setting?? don't know the outlet temperature and velocity
wall--> how to set the thermal conditions?? outside surface and ambient environment can be set to coupled, how to set the conditions of fluid and inside surface?
Thank you very much for any help