Temperature as function of direction
 

Hello,
got a little problem.
I try to simulate an heatexchanger. Because of my model is to big(61Tubes) i have to waiver of the innerflow. My question is, how to define a Temperature function for the wall of a tube.
The function is quite simple:
T(x)=T0 - 20*x/618
T0=343.15K
L(length of the tube)= 618mm
x is the coordinate of the length, so that at the beginning i got an value of 343.15K and at the end 323.15K for the temperature.
big thanks for help

Use an UDF in which you can define the temperature as a boundary condition.

Do

I didn't work with UDF before, so i just don't how....