I'd say that you can't tell the difference.

Online Materials Information Resource - MatWeb

Over-all heat transfer coeffients have to do with modeling a system or part of a system such as a heat exchanger.

For the construction materials of such a system, of importance are the specific thermal conductivities of said materials; in your case, T11 & T22 grade alloys.

These will go into determining the over-all heat transfer coeffient. You will also need to know inlet & outlet temperatures and the heat/fluid contact area.

See here:

http://en.wikipedia.org/wiki/Heat_transfer_coefficient#Alternative_Method_.28A_simple_method_for_determining_the_overall_heat_transfer_coefficient.29

For your specific application, we would need quite a bit more information.

Come back with more information!

Unless the thermal conductivity is wildly different between T11 and T22, the overall thermal conductivity will be very nearly the same. (Compared to boundary conditions, fluid turbulence, and fluid thermal conductivity, the conductivity of the metal is relatively minor.)

That's right, in terms of resistance to heat flow, there are 2 fairly large resistances, relating to heat transfer from hotter fluid to metal and from metal to cooler fluid, added to one much smaller one, relating to conduction through the metal, so a change in metal conductivity has little effect. The ΔT across the metal is much less than the temperature difference between the bulk fluids.