Problem 5 – Hint 3

In order to avoid the wrong conclusion that the length L remains always constant, you need to keep in mind that the average temperature over a cross-section of the warm “sausage” around the pipe is not on the order of the water temperature inside the pipe, but significantly lower. So, the first thing you need to do is to relate that average temperature to the radius of the “sausage” which in turn is a function of time.

Please submit the solution to this problem via e-mail to