Freeze/Thaw Structural Analysis in Metal Tubing

[MercyMedical]

I am currently working on a program that involves the analysis of metal tubing that will contain a working fluid that will undergo a freeze and thaw process due to ambient temperatures. I need to determine what kind of stress the tubing will experience due to the thermal expansion during the thaw.

Currently I am modeling the solid fluid as only capable of expansion in the radial direction, not longitudinal, although this may be a bit too conservative. After I have determine the expansion of the tube and the solid fluid over the operating temperature range I'm somewhat at a standstill on how to calculate the pressure caused by the difference in diameters as well as the resulting stress experienced in the tube.

Any help to point me in the right direction would be appreciate. Thanks.

 

[MikeHalloran]

ISTR (from decades ago) that the next step is to calculate the stress required in the tube to compress the solid frozen contents down to the nominal ID of the tube.

That involves applying a virtual pressure to the OD of the frozen contents and using the solid's bulk modulus to back-calculate how large that virtual pressure must be, ... then applying that number as an internal pressure to the tube material and figuring out how far it expands or whether it fractures.

... and repeating with thicker or stronger tube until the tube doesn't fracture or yield beyond acceptable limits.
... or something like that.




Mike Halloran
Pembroke Pines, FL, USA

 

[MiketheEngineer]

If it freezes - I will bet the tube blows.... Just my experience.

 

[flash3780]

Water experiences about a 9% expansion when it freezes because the molecules form an open lattice. From there, it behaves much like any solid, shrinking as temperature decreases. I think that you should be able to deal with this by defining coefficients of thermal expansion.

 

[MercyMedical]

flash3780,

The working fluid I'm dealing with actually isn't water. I'm looking at ammonia and propylene. Due to that, I'm more concerned of the expansion that the tubing will experience during the thawing process. This is for a serpentine radiator tubing, roughly 0.250" OD.