Dear cmmcnamara,
I found your post while trying to solve a very similar example. Like you, I want to compare the results of the Simscape pipe (from the thermal liquid library) with the results of a textbook. According to VDI Heatatlas (p. 697 – 698), the outlet temperature of a 1 m long pipe with a 10mm diameter should be 52.2 °C assuming a constant wall temperature of 100 °C and an inlet temperature boundary condition of 10 °C in combination with a massflow 0.5 m/s.
Leaving all settings initial, I receive an outlet temperature of 40.12 °C, which is an unacceptable difference compared to the textbook solution. However, I found out that the value of the “internal surface absolute roughness” (in the “Friction and Heat Transfer” setting of the pipe) seems to be of major importance for the result. In other words, if I play around with that value, I can easily fit the Simscpape model results to the analytical solution.
Another interesting result occurs if I make a subsystem with 10 pipe segments (each pipe segment has now a length of 0.1m). With the same setting, the outlet temperature is 46.34 °C. It seems like the number of elements is also of great importance for the numerical solution. It would be great if some of the Mathworks people around that forum can reply to that post. Browsing several forums across the internet, I more and more get the impression that a lot of people out there deal with the same kind of problem. With the results given above, it is difficult for me to “trust” the Simscape solution.
Here you can see the results of the pipe (only one pipe segment 1m long):
Here you can see the results of the pipe (10 segments 0.1 m each):
