Freezing moving water

ChrisJ

I figured I'd throw this one up on the pole and see who salutes it.

Does circulating or moving water lower the freezing point? If so, how much?
Does simply circulating water with a pump warm the water at all? Theoretically?

Would the water's freezing point be higher at the suction side of the pump, or leaving the pump? Let's assume slight vacuum on the suction side and 5 PSI on the outlet.

What about if the pump is intentionally run into slight cavitation, how would this effect temperature and freezing points? Does cavitation cool or warm the water?

fentonc

I think the affect of pressure changes on freezing temperature is pretty negligible for water. There might be some actual effect from the mechanical movement of water that prevents/delays freezing, but it seems like the energy from running the pump either gets dissipated into the room around the pump or into the water/pipes (because where else would it go?). If the circulator is running without an external heat source like a boiler, and the water is cooler than room temperature in the house, the dominant effect will be the radiators acting in reverse - heating up the water and cooling down the room (and thus preventing water from freezing by warming it up).

EBEBRATT-Ed

just a guess. Pump will warm the water, cavitation will really warm it but just at the pump because it's not moving. Resistance to flow causes pipe friction and warms the water but wouldn't change water freeze point

ChrisJ

EBEBRATT-Ed said:

just a guess. Pump will warm the water, cavitation will really warm it but just at the pump because it's not moving. Resistance to flow causes pipe friction and warms the water but wouldn't change water freeze point

I'm lost as to what you mean "it's not moving".
Do you mean the actual cavitation it self isn't moving?

JUGHNE

Standing water in lakes and ponds will freeze before running/moving water in rivers and streams.

No math used or needed.

mattmia2

Is that because it is moving or because it is mixing with warmer water below?

ChrisJ

mattmia2 said:

Is that because it is moving or because it is mixing with warmer water below?

I believe simply because it's being mixed with warmer water.

JUGHNE

I think because it is moving.

Where would the warmer water be coming from?

Sources could be some underground springs, but many miles away.

It will eventually freeze over but later than ponds.

ChrisJ

JUGHNE said:

I think because it is moving.

Where would the warmer water be coming from?

Sources could be some underground springs, but many miles away.

It will eventually freeze over but later than ponds.

Most if not all streams are fed by lakes or springs.
The lakes freeze over which insulates the water from the air.

The springs are insulated by soil.

Everything I've looked up claims water moving or not freezes at the same temperature.
That's why I started this thread. I'm curious how true it is, and what other things effect it.

EdTheHeaterMan

I think that @fentonc covered it perfectly, even using charts and graphs that on one understands. Of course @JUGHNE is spot on with his highly technical observations. What else do you need to know?

IMHO just leave leave the tap dripping and the circulator operating if the burner goes out during freezing weather conditions. You can't be any worse off.

ChrisJ

EdTheHeaterMan said:

I think that @fentonc covered it perfectly, even using charts and graphs that on one understands. Of course @JUGHNE is spot on with his highly technical observations. What else do you need to know?

IMHO just leave leave the tap dripping and the circulator operating if the burner goes out during freezing weather conditions. You can't be any worse off.

This question has nothing to do with HW heat or any heating system.

GGross

ChrisJ said:

JUGHNE said:

I think because it is moving.

Where would the warmer water be coming from?

Sources could be some underground springs, but many miles away.

It will eventually freeze over but later than ponds.

Most if not all streams are fed by lakes or springs.
The lakes freeze over which insulates the water from the air.

The springs are insulated by soil.

Everything I've looked up claims water moving or not freezes at the same temperature.
That's why I started this thread. I'm curious how true it is, and what other things effect it.

I think this is correct. When you look this up online remember they are talking about the water temperature freeze point being the same. So in my understanding the freeze point remains the same, but it would require a lower ambient temperature to get the water to freeze point when it is moving, instead of standing still

JUGHNE

I recall a lab experiment where a beaker of water was cooled down to right at freezing or maybe a little below. The water did not freeze until you bumped the beaker and then it all instantly froze.

Maybe nothing to do with this conversation but just testing my memory.

Matt_67

I agree with the moving water picking up heat from the ground. Typical commercial ice machines have a pump that moves water over the evaporator, i doubt they'd do that if it took more energy. Water is unique in that its most dense at around 34 degrees and then gets less dense as it actually freezes so that might play a role here too.

PC7060

Yes, standing water freezes faster.  Moving water inhibits the chain reaction between molecules that occurs during crystallizing process.    

Jamie Hall

Water is funny stuff. One of the most often overlooked characteristics of it is that it is densest at 4 C, unlike almost any other liquid, which would be densest at its freezing point. Furthermore, normal ice is considerably less dense than water at any temperature.

This is helpful. In still water, the water cooled by the air, if it's below freezing, will stay at the surface -- and may freeze, but it won't sink, and the ice will happily float on the surface. Leaving warmer liquid water underneath. Now if there is a spring, or currents in the body of water, that will bring that warmer (denser) water to the surface or near it, and may keep it from freezing -- or just thin the layer of ice (as countless people have discovered to their dismay...).

So in a body of water it's not so much the moving itself which keeps it from freezing, but the mixing with warmer, more dense water. If there isn't a source of that slightly warmer water, though, a stream will freeze eventually.

Even in a very cold long winter, a lake will rarely freeze more than a couple of feet thick because of this. Good for fish...

If you're looking at a pipe, though, it won't freeze provided two things: the water is kept flowing, and there has to be at some point in that flow path where it has a chance to warm up again. Where I've seen heating systems get in trouble is where there are several paths for the water to take, and one of them is really cold -- then ice will start to form in that path, and that reduces the flow, so it gets colder, so more ice forms, and eventually (it may not take long) a plug of ice forms -- and then you have a frozen pipe. It's much worse with domestic water, as it can take a fair amount of flow to keep things warm enough. The proverbial dripping faucet is not enough sometimes.

ChrisJ

One thing I have experience with is water not freezing at a higher pressure.

Specifically a 2 liter bottle of soda I forgot in the freezer at my parent's old house when I was around 20 years old. I took it out, thought "Oh, it didn't freeze, good!" and as I was unscrewing the cap I paused thinking "Maybe this is a bad idea" and before I could tighten it, it blew off and dented the kitchen ceiling.

It made some mess, but not near as bad as you'd expect as the slush / ice plugged the bottle.

Now, it's been over 20 years since that happened so maybe I'm remembering wrong, but I do know it dented the ceiling. Not much, but enough to see a slight outline from the cap.

Makes you wonder.....
If letting a faucet run under the wrong conditions could actually cause it to freeze.

hot_rod

Some bottled water has a lower freezing point also. Is it because it is super purified, or that they added sodium or other ingredients? Or both I suspect.

Be interesting to know when water in tube moving 3 fps freezes. DI water would be a lower freeze point?

Jamie Hall

DI water has a higher freeze point -- anything in the way of dissolved solids will lower the freezing point.

I love @ChrisJ 's experience with the soda bottle! Not so much, perhaps, depression of the freezing point with pressure (it does drop, but not that much!) but supercooled. If there are no nuclei for the crystals to form, they may not -- until a shock (did you shake that bottle even a little??) comes along and then whang the whole thing starts to freeze up.

It's a pilot's nightmare, by the way -- supercooled water is not that uncommon in some weather conditions, but when an airplane comes along and disturbs it it does the same thing -- and ice cubes don't fly very well.

ChrisJ

Jamie Hall said:

DI water has a higher freeze point -- anything in the way of dissolved solids will lower the freezing point. I love @ChrisJ 's experience with the soda bottle! Not so much, perhaps, depression of the freezing point with pressure (it does drop, but not that much!) but supercooled. If there are no nuclei for the crystals to form, they may not -- until a shock (did you shake that bottle even a little??) comes along and then whang the whole thing starts to freeze up. It's a pilot's nightmare, by the way -- supercooled water is not that uncommon in some weather conditions, but when an airplane comes along and disturbs it it does the same thing -- and ice cubes don't fly very well.

Not on purpose or that I remember.

But something upset it.

JUGHNE

If a soda machine loses power in the winter, the heaters quit working and the diet soda (no sugar) freezes first. FWIW

Did you get in trouble or not get caught putting the dent in the ceiling?

mattmia2

ChrisJ said:

One thing I have experience with is water not freezing at a higher pressure.

Specifically a 2 liter bottle of soda I forgot in the freezer at my parent's old house when I was around 20 years old. I took it out, thought "Oh, it didn't freeze, good!" and as I was unscrewing the cap I paused thinking "Maybe this is a bad idea" and before I could tighten it, it blew off and dented the kitchen ceiling.

It made some mess, but not near as bad as you'd expect as the slush / ice plugged the bottle.

Now, it's been over 20 years since that happened so maybe I'm remembering wrong, but I do know it dented the ceiling. Not much, but enough to see a slight outline from the cap.

Makes you wonder.....
If letting a faucet run under the wrong conditions could actually cause it to freeze.

That isn't because the pressure changes the freezing point but because as soon as you let the pressure off of it some of the carbon dioxide comes out of solution, the carbonic acid was depressing the freezing point. I think as soon as a little bit of carbon dioxide comes out of solution the liquid is now below its freezing point and most of the carbon dioxide comes out of solution as it turns to ice.

aircooled81

Great post, love it, I wanna guess... but who won?

Does circulating or moving water lower the freezing point? 'No'
If so, how much? 'moving water doesn't freeze at same temp as water lacking motion'
Does simply circulating water with a pump warm the water at all? 'yes, impart energy to the water, some will be motion some will be heat' Theoretically? 'yup'

Would the water's freezing point be higher at the suction side of the pump, or leaving the pump? 'higher leaving the pump, higher the pressure the lower the freezing point.' Let's assume slight vacuum on the suction side and 5 PSI on the outlet. 'slight vaccum lowers the boiling point, releases heat easier therfore heading closer to freezing than higher pressure'

What about if the pump is intentionally run into slight cavitation, how would this effect temperature and freezing points? 'lower pressure, closer to freezing direction'
Does cavitation cool or warm the water? 'cavitation doesn't cool the water, lower pressure does. cavitation is just the phenomenon of lowering the pressure to release the condensed gases'

mattmia2

The freezing point changes with pressure but not very much. It is around 1 tenth of a farenheit degree for every 100 psi.

ronaldsauve

I grew up in Vermont where we lived on a farm with gravity fed water from a well on the hill. The water line was only a few inches below the surface for most of the way to the house. But near the house it also diverted to what used to be a milk house, then to our house but buried deeper. It would get pretty cold in Vermont in those days, (the 50’s 60’s 70’s), in fact I remember one time it hit 45° below zero, and as a teenager my car still started. But 30° below zero was common in the winter. So what does all this have to do with the topic at hand? Plenty. At the former milk house, my dad set up a pipe to the surface with a wooden plug in the end that he drilled a pin hole in. So all winter it sprayed a minuscule spray into the air. Of course the spray froze and made a beautiful ice sculpture all winter. But our waterlines from the well to the house never froze, even at 45° below zero!

ChrisJ

ronaldsauve said:

I grew up in Vermont where we lived on a farm with gravity fed water from a well on the hill. The water line was only a few inches below the surface for most of the way to the house. But near the house it also diverted to what used to be a milk house, then to our house but buried deeper. It would get pretty cold in Vermont in those days, (the 50’s 60’s 70’s), in fact I remember one time it hit 45° below zero, and as a teenager my car still started. But 30° below zero was common in the winter. So what does all this have to do with the topic at hand? Plenty. At the former milk house, my dad set up a pipe to the surface with a wooden plug in the end that he drilled a pin hole in. So all winter it sprayed a minuscule spray into the air. Of course the spray froze and made a beautiful ice sculpture all winter. But our waterlines from the well to the house never froze, even at 45° below zero!

And they all used water that was much warmer from far below the ground.

So the actual movement of it was irrelevant other than it kept the water's temperature from dropping below 32F.

Joeh1223

Is it true if you let your faucet drip your pipes won’t freeze?

ArthurPeabody

ChrisJ said:

Does circulating or moving water lower the freezing point?

Yes. Freezing isn't getting cold, it's a loss of entropy, an introduction of order. You can test this yourself with a lab mixer when it's freezing out. The water will fall below the freezing point if stirred constantly.

ChrisJ said:

Does simply circulating water with a pump warm the water at all?

Yes, because of friction. A superfluid, one entirely frictionless (which happens with helium at low-enough temperatures), wouldn't. It's not a big effect.

ChrisJ said:

Would the water's freezing point be higher at the suction side of the pump, or leaving the pump? Let's assume slight vacuum on the suction side and 5 PSI on the outlet.

Unlike many substances water expands when its temperature drops below 4°C, which means that as you increase the pressure on it its freezing point lowers. Glaciers melt at their bottoms - pressure-melting - because of the weight of the glacier on top.

ChrisJ said:

One thing I have experience with is water not freezing at a higher pressure.

Specifically a 2 liter bottle of soda I forgot in the freezer at my parent's old house when I was around 20 years old. I took it out, thought "Oh, it didn't freeze, good!" and as I was unscrewing the cap I paused thinking "Maybe this is a bad idea" and before I could tighten it, it blew off and dented the kitchen ceiling.

I've often experienced a bit of slush forming in a soda bottle when I removed the cap.

Look at the phase diagram for water, a graph of its state in temperature versus pressure. https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Introductory_Chemistry_(CK-12)/13:_States_of_Matter/13.20:_Phase_Diagram_for_Water

JUGHNE said:

I recall a lab experiment where a beaker of water was cooled down to right at freezing or maybe a little below. The water did not freeze until you bumped the beaker and then it all instantly froze.

This is correct; it's called super-cooling. Crystallization requires water molecules changing their orientation to each other, a little more than the thermal motion at the freezing point. You have to keep the water very still as you cool it. I first encountered it in Jules Verne's 'Off on a comet', in which an entire sea froze all at once. I've imagined a murder mystery in which a swimming pool is super-cooled then the victim is dumped into it. It'd be a torturous death and a mystery to the investigators, especially if they come upon it after it's thawed.

ArthurPeabody

hot_rod said:

Some bottled water has a lower freezing point also. Is it because it is super purified, or that they added sodium or other ingredients?

Anything added lowers the freezing point; it's called molal freezing point depression.

Jamie Hall said:

If there are no nuclei for the crystals to form, they may not -- until a shock (did you shake that bottle even a little??) comes along and then whang the whole thing starts to freeze.

You've confused the nuclei necessary to make bubbles when boiling water with freezing. Any foreign substance will depress the freezing point.

ChrisJ

Joeh1223 said:

Is it true if you let your faucet drip your pipes won’t freeze?

It may, because if it's running fast enough it keeps the water temperature higher by bringing in fresh water.

But, sometimes more importantly if it does freeze having the faucet open, even a little, relieves enough pressure to stop the pipe or tube from splitting. As the ice forms it builds pressure between it and the closed valve and that pressure I believe is more often than not what splits the pipe.

wam525

Joeh1223 said:

Is it true if you let your faucet drip your pipes won’t freeze?

Yes, likely ok for the pipes, but a slow drip will likely cause water in the drain pipes to freeze, and this could be a 2nd major issue. I know from experience.

JustinTheCarpenter

Yes it will. Dripping faucets will freeze, the pipes leading to them will freeze, any water standing or moving will freeze if conditions are right. You need to evaluate conditions & make an (impossible to be) educated guess. My $.02

ronaldsauve

ChrisJ said:

ronaldsauve said:

I grew up in Vermont where we lived on a farm with gravity fed water from a well on the hill. The water line was only a few inches below the surface for most of the way to the house. But near the house it also diverted to what used to be a milk house, then to our house but buried deeper. It would get pretty cold in Vermont in those days, (the 50’s 60’s 70’s), in fact I remember one time it hit 45° below zero, and as a teenager my car still started. But 30° below zero was common in the winter. So what does all this have to do with the topic at hand? Plenty. At the former milk house, my dad set up a pipe to the surface with a wooden plug in the end that he drilled a pin hole in. So all winter it sprayed a minuscule spray into the air. Of course the spray froze and made a beautiful ice sculpture all winter. But our waterlines from the well to the house never froze, even at 45° below zero!

And they all used water that was much warmer from far below the ground.

So the actual movement of it was irrelevant other than it kept the water's temperature from dropping below 32F.

Our water was not “from far below the ground”. It was a dug well, the bottom of the well was about 5 feet below grade on a side hill. This was very common years ago in homes like the one I grew up in. The 2 story colonial house was built about 1800, no insulation, or any place in the walls to put any. It was a type of post and beam construction, with solid planks about 4 or 5 inches thick and up to a few feet wide filling in the exterior walls between the posts and beams, stone foundation, dirt cellar floor, wood stove heat, and so on. Nothing like you see these days, we’re unlikely to ever see trees of the size to make planks a few feet wide. Most people would probably doubt that such planks are possible, unless they were familiar with what was common back then.

ronaldsauve

ChrisJ said:

ronaldsauve said:

I grew up in Vermont where we lived on a farm with gravity fed water from a well on the hill. The water line was only a few inches below the surface for most of the way to the house. But near the house it also diverted to what used to be a milk house, then to our house but buried deeper. It would get pretty cold in Vermont in those days, (the 50’s 60’s 70’s), in fact I remember one time it hit 45° below zero, and as a teenager my car still started. But 30° below zero was common in the winter. So what does all this have to do with the topic at hand? Plenty. At the former milk house, my dad set up a pipe to the surface with a wooden plug in the end that he drilled a pin hole in. So all winter it sprayed a minuscule spray into the air. Of course the spray froze and made a beautiful ice sculpture all winter. But our waterlines from the well to the house never froze, even at 45° below zero!

And they all used water that was much warmer from far below the ground.

So the actual movement of it was irrelevant other than it kept the water's temperature from dropping below 32F.

One more thought: the dug well on the side hill was a heavily wooded hill as most of our property was. But the water line ran a couple hundred yards in wooded area, then from there came into the open for another 300 yards or so to the former milk house, which had been abandoned years before, and all that was left of it was a concrete “tub”. But the water line from the well to the former milk house was only a few inches underground the whole way. The original line was lead pipe, which we replaced with ABS pipe when I was about 14 years old, and my 2 younger brothers and I spent a whole summer digging up the old lead pipe, and replacing it with the ABS. We didn’t dig the trench any deeper, as if you’ve ever tried to dig by hand with pick and shovel in a bony creek bed like we did, you’d know why. Like digging stone and rock packed solid over years or centuries of water running in it. Not easy digging to say the least!

ChrisJ

@ronaldsauve

5 feet is deeper than most footings in the NJ / PA / NY area. 6 feet is plenty to keep water lines from freezing even in extreme prolonged cold.

jumper

A circulator does warm water. Just make a closed loop and see in a few days.

mvickers

Essentially, the water that's being 'disturbed'/moving will withstand freezing, as in, my creek only freezes on its surface and the moving water underneath never freezes.  My pond that's near the creek doesn't freeze where the supply from the above pond enters mine.  And, while the surface of the pond will freeze, it only freezes for a few inches, and to a degree, I can keep the surface from freezing by injecting air into the pond through submerged aerators.  When the air pump is running, the water above the aerators looks like it's boiling, doesn't freeze.  A fountain or falls would have a similar effect and keep it from freezing

mattmia2

a fountain would be mixing in the water that is being warmed by the ground, a waterfall would tend to freeze because it is mostly he surface water going over the falls, at least a natural one

ronaldsauve

ChrisJ said:

@ronaldsauve

5 feet is deeper than most footings in the NJ / PA / NY area. 6 feet is plenty to keep water lines from freezing even in extreme prolonged cold.

Except that the waterline itself was only a few inches below ground for almost 500 yards

ChrisJ

ronaldsauve said:

ChrisJ said:

@ronaldsauve

5 feet is deeper than most footings in the NJ / PA / NY area. 6 feet is plenty to keep water lines from freezing even in extreme prolonged cold.

Except that the waterline itself was only a few inches below ground for almost 500 yards

Ok.

Regardless, moving water still freezes at the normal freezing point, just like standing water. 32F at sea level.

This isn't a hypothesis, it's a scientific fact. Just like the planet is a sphere.

mattmia2

ronaldsauve said:

ChrisJ said:

@ronaldsauve

5 feet is deeper than most footings in the NJ / PA / NY area. 6 feet is plenty to keep water lines from freezing even in extreme prolonged cold.

Except that the waterline itself was only a few inches below ground for almost 500 yards

And warmer water from the spring a couple feet below ground was constantly warming it.