[quote=Jeff Findley;1166649]In article 80d64180-bb17-4eb8-a5d5-f1428de554b0

There are two issues: conducting heat from the water to the container
wall, and radiating heat from the container wall into space. The
latter is easy enough to calculate: a perfect emitting surface at 0
deg_C radiates just over 300 W m^-2. Real materials aren't perfect
emitters, but you can get to 0.8 or better pretty easily. Freezing
water into ice takes 334 J/kg, so it's easy to work out a minimum time for
any amount of water, given the tank shape.

If there's poor conduction from the water in the interior to the
container wall, the actual time will be longer. You could look up
the thermal conductivity of water and work it out. If rapid freezing
is needed, you could use a tank that is small in at least one
dimension so no part of the water is far from a tank wall or put
copper filaments or something inside the tank to improve conduction.

If you try this for real :-), make sure your container can
accommodate the expansion as the water freezes.