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My question:

If a thin-walled copper or brass pipe is open on both ends (let's dimension it at 60 cm long by 8mm inner diameter, as an example) and is filled with slightly salty water (estuarine water; slightly salty, but not quite sea water), and subjected to below-freezing temperatures for a few days, is there a significant risk that enough ice-plug constriction can form inside it such that the pipe walls burst? Or, will the ice harmlessly extrude?

(My practical problem is that I am afraid I probably did not get all the water out of the heat exchanger in a marine diesel engine, and that the lower parts of the piping may have become filled with ice. It was three or four days of -7C to -8C air temperature at night, warming up slightly, perhaps to 0 or even +1C during the day; the heat exchanger is inside the closed-off boat engine room, and the boat is in the water, so the engine room was probably a few degrees warmer than the air temperature due to conduction).

From my reading of the literature I am thinking (hoping, really!) that I may be lucky this time, because 1) slightly salty water begins its freezing process by segregating into pure ice platelets and brine-rich solution, which allows the fluid brine (and perhaps some of the ice) to continue to flow out the two open ends; 2) being not so cold inside the engine room, supercooling of the brine was less likely, and consequently 'flash freezing' that might have formed annular rings in two places at the same time, allowing high water pressure to build up in-between, was also less likely; and 3) the slightly salty composition would make the ice less rigid and therefore more able to flow through the open ends of the heat exchanger tubes.

Any comments/thoughts/ideas on how ice will flow or deform? Many thanks

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    $\begingroup$ You have done a lot of research yourself, could you duplicate the situation where you could observe it, rather than keeping your fingers crossed because you can't get at the pipe? Or can you heat the area even a little bit to reduce the chance of a leak? I would guess that the ice will take the path of least resistance, along the pipe. There seem to be a lot of things in your favor, but I will look up how ice forms. $\endgroup$ – user108787 Nov 14 '16 at 22:28
  • $\begingroup$ This site my.ilstu.edu/~jrcarter/ice/extrude78 may provide some reassurance. The pipes are steel, so they are stronger than copper, but less ductile in axial expansion. The length of the extrusions ( of pure water ice) in the pictures would indicate to me that ice does take the easiest route, along the pipes. Best of luck with how it turns out. $\endgroup$ – user108787 Nov 14 '16 at 22:51

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