09 April 2019
You need a couple more BCs.
The outside face of the cylinder, is that convective cooling to the air? What is the convective heat transfer coefficient? What is the air temperature?
Since this is a learning model, let's assume the temperature on the two circles representing the cooling fluid are 20 C at the fluid inlet and 100 C at the fluid outlet. I just made up that last temperature. When you build the 3D model, you will solve for this temperature, but for this 2D learning model, we will specify it. When you do the 3D model, you will need the convective heat transfer coefficient of the fluid to the spiral wall.
If you wanted to put in a three more holes between A and B, you could set the temperature of those holes at 40, 60 and 80 C.