Re: cooling water

[David Dockstader <DRDOCK00@UKCC.UKY.EDU>]

On Wed, 03 Jun 1998 00:05:34 -0500 Doug Craigen said:
> Another factor that I've heard plays a role is that water that has been heated
> will contain fewer gases that inhibit the cyrstallization.  This gives the hot
> water another slight advantage.  This may be the dominant factor in the related
> claim that hot water pipes freeze faster than cold water pipes.  In this case
> the system is somewhat closed, so evaporation is not as likely - but water
> sitting in a hot water pipe and water sitting in a cold water pipe will have a
> similar starting temperature (if the taps have been off for a while).
Not only disolved gasses, but think of all the lime that precipitates in
hot water heaters.  I suspect that in this case the cold water pipe starts to
freeze first and freezes from the outside in quite gradually, allowing water to
flow in the center of the pipe and relieve the pressure buildup from the
expanding ice.  However, the hot water pipe without condensation nuclei or
seed materials will supercool and then freeze suddenly and completely through
the pipe, bursting the pipe.  The ice forming from the outside in will in
many cases sufficiently insulate the interior section keeping the pipe from
freezing solid, long after the hot water pipe is fully frozen.