Flowing Water and Freezing
Name: Joseph F.
We all know that moving water does not freeze. My
question is, at what point does the temperature overtake the moving
water? Is there a correlation between the volume, velocity and the
temperature of the environment. An example: if I need a hose above ground
and have it on all the time is there a temperature that it would freeze
and at what velocity with the water need to maintain to keep it from
freezing? I am hoping for some type of equation that would tell me this
What you describe is a very complex problem. Running water will freeze
provided that the rate at which heat is removed from the cold surface
exceeds the heat required to transform water at 0 C. to ice at 0 C.
However, the dynamics of this process will be very complicated depending
upon the temperature of the cold surface and the hydrodynamics of the water
flow across that surface (which could be air). Every sleet or hail storm
involves the freezing of liquid water to ice under very turbulent
conditions, for example. I do not think you will find any "simple" equation
to describe such processes.
With visions of huge chunks of ice floating down the Missouri River, I must
differ on your point that "moving water does not freeze." Now leaving a hose
running, which seems to be the gist of your question, is another story. Here,
you have water that is supplied from a source that is above the freezing
point of water. For example, my well brings up water at maybe, 50? Degrees
Fahrenheit. If I run it through a hose on the ground, how slow can I turn it
down before the water freezes up in the hose? The main variables in this
would seem to be a) the ability of the hose conduct heat, b) the length of
hose, c) the outside temperature, and d) the velocity of the water. As the
water moves through the hose, it will lose energy to the surroundings; if it
loses enough energy, it will freeze up. But alas, I don't know of any simple
equation to predict this. Interesting question though. It does seem that one
could work out an equation for this. Perhaps a civil engineer has to deal
with questions like this.
Paul Mahoney, Ph.D.
It would be very difficult to develop an equation to
approximate what you are looking for here. There are
far too many variables, some of which I am listing
1. inside diameter of the hose
2. material composition of the hose (some insulate
better than others
3.mini-environment of the hose (exposed to sunlight,
exposed to wind, lying in insulating grass, lying on
non-insulated hard surface)
4. velocity of the flowing water
5. temperature of the incoming water (which could
provide a "melting' effect on the forming ice
As you can see, depending upon these and other
characteristics of your scenario, you can have a range
of outcomes...some where the hose could freeze solid,
others where no freezing was able to happen at all.
Suffice it to say that if you hold all of the
variables constant except flow velocity you may be
able to develop an experiment and plot flow vs. time
for water flow from the outer end of the hose to
cease( frozen hose); from that you could develop your
This is a tough one...good luck.
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Update: June 2012