Why does running water not freeze?
It will freeze, in a complicated relationship between temperature and flow rate. An icicle is essentially a frozen stream of water, to present an example. Basically, as long as water replacement rate exceeds heat loss rate, the water will not freeze. Only the water exposed to the cold will lose the heat needed to cause solidification. In flowing water, that water is removed from the zone of exposure by warmer incoming water (replacement water), which then starts to lose its heat. Only when the average residence time of water becomes long enough for the water to lose enough heat to attain freezing (solidification) will you see the water freeze over.
