Help please!

REZA

Hi I am modeling convection heat transfer coeficient on the outer surface of a cylinder placed in the wind tunnel. I found out through the experimental data that the temperature on the surface of the cylinder that I am modeling is changing from 40 to 50 C while I assumed a constant temperature for the cylinder surface regarding the fact that I did not have heat flow rate through its surface and want to measure the h value. Should I define a UDF for the temperature or just average these temperatures and use a constant temperature? Cheers, Reza