Does hot water freeze faster?

Perry_2

you are right that their water boils at 110* - but it also boils at 100*

Now all of you steam types may or may not be surprised if I tell you that our water boils at 92* ... (and over quite a range* too).

You may be very amazed at all the temps I can make water boil - or not boil at...

Perry

Will_5

Rate of Transfer

reading another post someting came to mind, I didn't want to hijack the thread so I thought I'd start another......

Correct me if I'm wrong, but isn't it true that hot water will not freeze any faster than cold water, 100 degree water will drop to 50 degrees exponentially faster that 35 degree water will drop to 33. The rate of heat transfer is greater the larger the delta T. That being said, if you do a combustion test where the water temp is 180 degrees and the flue gas temp is 390 gross and you do a test with 140 degree water and 330 flue gas temp, the CO, excess air and oxygen will be the same.Doesn't the efficiency have to go up? That would show in the combustion efficiency right?

C

Mike T., Swampeast MO

> reading another post someting came to mind, I

> didn't want to hijack the thread so I thought I'd

> start another......

>

> Correct me if I'm wrong,

> but isn't it true that hot water will not freeze

> any faster than cold water, 100 degree water will

> drop to 50 degrees exponentially faster that 35

> degree water will drop to 33. The rate of heat

> transfer is greater the larger the delta T. That

> being said, if you do a combustion test where the

> water temp is 180 degrees and the flue gas temp

> is 390 gross and you do a test with 140 degree

> water and 330 flue gas temp, the CO, excess air

> and oxygen will be the same.Doesn't the

> efficiency have to go up? That would show in the

> combustion efficiency right?

>

> C



Still an unanswered question and yet another mysterious--dare I say "black magic"--property of water...

Mike T., Swampeast MO

> reading another post someting came to mind, I

> didn't want to hijack the thread so I thought I'd

> start another......

>

> Correct me if I'm wrong,

> but isn't it true that hot water will not freeze

> any faster than cold water, 100 degree water will

> drop to 50 degrees exponentially faster that 35

> degree water will drop to 33. The rate of heat

> transfer is greater the larger the delta T. That

> being said, if you do a combustion test where the

> water temp is 180 degrees and the flue gas temp

> is 390 gross and you do a test with 140 degree

> water and 330 flue gas temp, the CO, excess air

> and oxygen will be the same.Doesn't the

> efficiency have to go up? That would show in the

> combustion efficiency right?

>

> C



Still an unanswered question and yet another mysterious--dare I say "black magic"--property of water...

Mike T., Swampeast MO

Still an unanswered question and yet another mysterious--dare I say "black magic"--property of water...

Will_5

According to Newton

I was right
( rate at which a body cools is proportional to the temperature difference between the object and its surroundings.)

I never new they had a name for it though " the mpemba effect", sounds like somebody was out in the cold too long when they came up with that one!!

So that being said.... obviously the rate of transfer increases with lower boiler temper and overall efficiency goes up but does the combustion effeciency reflect that? or does steady state remain at steady state?

I probably should be able to come up with this, but I'm scratching my head.

C

Al Letellier_9

hot water freeze faster

> reading another post someting came to mind, I

> didn't want to hijack the thread so I thought I'd

> start another......

>

> Correct me if I'm wrong,

> but isn't it true that hot water will not freeze

> any faster than cold water, 100 degree water will

> drop to 50 degrees exponentially faster that 35

> degree water will drop to 33. The rate of heat

> transfer is greater the larger the delta T. That

> being said, if you do a combustion test where the

> water temp is 180 degrees and the flue gas temp

> is 390 gross and you do a test with 140 degree

> water and 330 flue gas temp, the CO, excess air

> and oxygen will be the same.Doesn't the

> efficiency have to go up? That would show in the

> combustion efficiency right?

>

> C

Al Letellier_9

hot water freeze faster

Yep.....why do the heat lines freeze before the water lines. Less air, less dense and heat goes to cold....why else to they use 165* water in a Zamboni?...if they used cold water, they would need one hour period breaks.

Will_5

Zamboni

I have to differ on the Zamboni, I thought they used hot water because it would have a melting effect to the top surface causing it to create a smoother surface and it does not produce air bubbles. I'm not sure it freezes faster though, although I'm not saying doesn't

I knew there would be a lot of discussion on this one!!

C

Mike T., Swampeast MO

You're not alone in scratching your head...

In an ideal world combustion efficiency is separate from heat transfer efficiency and the "boiler temperature" has no bearing on combustion efficiency.

Heat transfer purely via radiation is the only way I know to completely separate the two.

DanHolohan

The Second Friday Club

did this experiement. Cold water freezes faster.

Brad White_160

But is it not also true that

water that has been heated to drive out excess air will freeze faster than water that has entrained air? Even if the deaerated water is at a slightly higher temperature.

I remember that from 7th. grade science class, IIRC.

Will_5

You would think

that would make sense....... yet then again in the refrigeration world they would say " There's no such thing as cold, cold is only lack of heat ". Never did truly understand that!!

C

bob_46

Cunner

don't leave the window open the cold will come in!

Will_5

Ahhhh

I new an someone from the engineering community would chime in at some point. I still pondering my combustion eff. questions but something as simple as water freezing is a lot more entertaining.

Will_5

Will

the cold come in or the heat go out?

Mike T., Swampeast MO

Water freezing is NOT simple!

Brad White_160

The real fun and essential property of water...

This one used to stump me, but water is one substance that becomes less dense when it freezes. There may be others but I do not know what they are...

The reason frozen water is less dense is the crystalline structure- the crystals space out (not unlike me some days I suppose) and create a material with a lower density.

Now, imagine what would happen if this were not true and ice behaved as most solids do compared to their liquid forms:

Lakes and even the oceans would freeze solid as ice was formed, sinks, more ice forms and sinks....

Will_5

Easier

than making steam!!!!!!!! If I run out of ice I can always throw an ce cube tray out side, or does anyone actually have one of those anymore?

bob_46

And when

they space out the pipe breaks!

Mike T., Swampeast MO

Making steam is easy. Controlling it can be difficult...

JERRYG

old question,old answer

this question has resurrected every so often over the last 40 years that I know of.
It began with refrigeration mechanics that claimed that putting hot water in ice cube trays made them freeze faster.They claim this occured with a system that utilized a flooded evaporator.It had a refrigerant feed device called a "lowside float" that maintained the refrigerant level in the evap.Placing hot water in the freezer cause a rapid boiling of the refrigerant in the evap and increase the cooling effect.

Weezbo

Faster than What? )

ok another Trick question...:)

i need to have you here with me today then i could let you do a simple experiment..take a one gallon pail of cold water and a one gallon pail of hot water outside ,freez you fingers to d bone and come back in when one or the other buckets of water froze....

i think, that you would determine in your mind the sanest course of events would to be to get out of the cold and it is like that for the water as well. you have heat within your circulating systems which is given off to the cold..if you hang around in the cold long enough ,there is no heat to circulate..so "*the ugly bag of predominatly water" will freeze quicker if it is cold than if it is hot. trust me on this

* old star wars quote...

Perry_2

All else being equal....cold water freezes faster than hot water

Here is the engineering answer:

Assuming that the water - and what is disolved in it - is the same: Cold water always freezes faster than hot water. The hot water first must cool down to the temperature of the cold water - before it can cool down and freeze. Always.

So what about when there are differences in the water: If you first heat up or treat some water to remove the disolved water; and then cool it down to the same temperature that the other cold water is: Then the water that was treated will freeze faster than the water that still contains dissolved O2 and other things (assuming they start from the same temp). Actually, the "treated" water can freeze faster in some situations where it is a couple of degrees warmer than the cold water (but not more than a few degrees).

The old story about boiled water freezing faster... is only true if the boiled water is first allowed to cool down to the same essential temperature as the other cold water. Boiling the water removes disolved O2 and other things.

Another way to make a difference - especially in pipes - is the location of the pipe in the wall related to the cold. As stated above, a poorly insulated wall will freeze a "hot" water pipe fast once the heat is turned off. It would actually freeze a cold water filled pipe in the same location faster - just most people don't have both pipes in the same place at the same time.

Hope that helps.

Perry

Darrell

Water, freezing, density, changing properties, .

Let me see if I can sort this out in real world terms...

The likelihood of a water line freezing is directly proportional to the density of the builder/owner.

The speed at which the water line will freeze depends on how busy I am when the heat locks out.

When a house freezes hard...it is time to change properties.

Weezbo

essentially ,that is correct *~/:)

it also seems to have a certain Ring of Truth to it

Unknown

the zamboni

Just read an article about the guy driving a zamboni for a living... He stated that they only use ro water for resurfacing as its freeze quicker... Bottom line, the less junk in water, the faster it will freeze...

Perry_2

Purer water freezes faster than less pure water...

If the water starts at the same temperature.

In almost all cases that is true.

Perry

George Peteya_4

Hot Water ...

... is used so that the new ice bonds to the layer below. Use cold water and the new ice can break off, annoying the figure skating moms. The result of cold water is called rain ice, even in an indoor arena.

BTW, you CAN do a 360° with a Zamboni, at least I could 35 years ago.

powerhead

Ice nine!!

Kurt Vonegut wrote about "Ice Nine" (was it Cat's Cradle?).
The theory and actual experiments involved freezing water different ways. In his book when they got to experiment number nine they had developed a crystal with special properties.

When this crystal of "Ice Nine" was added to a body of water, all of the molecules instantly locked up like a stack of cannon balls or a crate of oranges. The idea was to use it as a military tool so that the Army and Marines would stop getting jeeps and tanks and things stuck in mud, could cross rivers and streams without building bridges, etc.

When the crystals fell into the wrong (power and money hungry) hands all of the worlds waters instantly froze. and the end of the world arrived.

The scariest part is that experiments similar to this actually [i]were[/i] undertaken................

Mitch_4

speaking strictly from a personal perspective

I service a couple of buildings where they imbedded the water pipe in an ouside wall, and there is a couple spaces where the insulation is not there and the HOT water pipe always freezes but the cold one does not, I am not talkin about it averages more..I always is the hot line..

So the laws of physics may be absolute, but the pipes in these buildings never studied law and HOT freezes faster.

Mitch

jp_2

pressure too

don;t forget about pressure, the higher the water pressure the lower the freeze point.

also remember water must expand to freeze.

i see pex freezing quicker than copper, i figure the pex expands allowing the water to freeze.

my guess is that in a hot water pipe, water has a better ability to expand, maybe due to the large hot water tank? thus the allowable expansion lets it freeze. not a perfect, theory, but maybe close?

i remember hot water will freeze faster if allowed to evaproate at the same time, large surface area compared to volume, as in the zamboni case.

MikeL_2

Hot / cold

The cold water piping is almost always connected to a device ( ballcock, humidifyer, ice maker.......) that has the potential to continue to draw/ move water after the rest of the piping system is dormant. I think personal grooming habits also play a role. I usually brush my teeth and flush right before bed; the hot water is idle and cooling while the cold water in the piping leading to the sink has been replaced with ambient temp. water from the basement..........

Unknown

RE: Zamboni

If I recall my college Physics correctly, the hot water is used in the Zamboni to create a process called Regelation whereby the water changes to ice much quicker at just that thickness or ratio of which it is put on the ice (just a film). This same principle happens between the blade of the ice skate and the ice as someone is skating but by friction or the weight being distributed across the small area of ice that is in contact with the blade.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Ray Landry_2

As stack temp drops, wouldn't you think that your combustion numbers like c02 co ect would become effected because the draft could potentially decrease with the cooler flue temp? This is one of the reasons why I made the thread about combustion numbers changing as bwt dropped.

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Christian Egli_2

The very effective world of phase change steam heat & AC cooling

This little kid tried all the ice cube freezing strategies until he got kicked out of the kitchen. Man, is it boring opening the freezer door every two seconds. This old fridge of ours was not like the modern ones with a fan to circulate air inside it, that is important, read on.

Place two closed containers of water in the icebox and you'll see the hot one freeze last. Convincingly.

This riddle has not much to do with physics per se, it's more about semantics. When we say the ice cube tray filled with hot water freezes first, we really mean the hot steamy water will cool faster. The difference is not trivial.

When water takes the slide down to freezing temperatures, it goes about it by loosing heat. It has 1 BTU per pound and per degree to loose, thus between freezing and boiling, you've got about 180 BTUs to get rid of. Water in a bottle will slide at the speed of conduction and convection and radiation (in whatever proportions). The effect is the same when going down a slide wearing shorts, it binds, it's painful and mainly, it's slow.

Those who know steam heat, will know there is a lightning fast method for removing heat from the boiler. Steaming away cools a burning hot boiler considerably faster than mere hot water, the numbers come out in a relation of 1000 to 1. This is a difference that matters. Flue gas temperatures often show this too with steam boilers producing lower temperature smoke as they boil away rather than when they just get warm.

Massive heat movements are not solely linked to temperature jump, they're also related to the transfer mode. A massive transfer rate even at a high temperature jump can dwarf a meager transfer rate at the largest possible temperature differential.

Those who know vacuumizers, will know this heat removing phase change works anytime a pound of water is made to disappear. If you ski like me and you get your pants wet from falling in the snow too much, you'll know exactly where those 1000 BTUs are leaving from; they leave you short changed.

Back to the ice cube tray.

The cold water tray is full of placid molecules that will wait for their fate. The hot tray - the boiling hot tray - is also full of molecules, most of which won't do anything much until the strong ones make a statement, this is just like the moderates in politics. Within the hot water tray? who are those boiling hot enterprising atoms ready to take their destiny into their own hands? It's that winner portion of water that will take off in steam; it's only a very small portion, but when it goes, it takes 1000 to 1 BTUs along with it.

What happens between the two ice trays [and oh, the ice tray patent was first held by a Daytonian, it was a complicated gadget that came with a lever on top to crush the cubes and the Frigidaire plant was right here in town until it got converted into a car factory... we've even got a cooled outdoor sculpture to commemorate this feat... blah blah blah] so back to the two competitors, say the one at 40F looses a BTU per minute, it's getting somewhere while the other one starts out at 212F and it too will loose a BTU or more per minute. At 212F, it may very well contain more than double the total BTUs of the other. So, if you're thinking hot water hydronics, you're thinking this is a lame race... but watch what the small fraction of boiling water does.

In very short order, the bits of steam wafting off the hot tray remove thousands of BTUs - the cold tray did not see this cooling effect coming. As we were watching the one BTU drop minute by minute, a robber was making a break with one thousand of them.

That big loss is enough to drop the temperature on the hot tray in a huge way, faster and deeper than for the cold tray. Right off the start.

Once the steam is mostly gone, the race reverts to the ordinary handicaps, but by this time, the game is already decided and won - the cold water tray has no magic trick to throw.

Whether water next freezes like so or like so, is a moot point. The physics were siding with steam and evaporation on this one.

***

I do think this explanation is rather perplexing, the same way so many people think steam is not worth the trouble.

I came up with this theory after much frustration with an air humidifier. And for the little kid still in me, this next experiment was the proof to this hot steamy cold riddle.

We're talking about an air duct humidifier consisting of a spongy mass through which hot air is fed. The spongy mass is constantly kept wet by having a drip tube pouring over it's forehead, and whatever water does not get taken away into the air stream simply gets dumped down the drain along with any residual heat built into the leftover.

Here's what was frustrating me. The unit was fed with stone cold water, and during it's travel through the breeze, it would warm up, get hot and flow out the bottom of the sponge. A big stream of hot water going down the drain - to pure waste - meanwhile, the air was not being humidified the way we all wanted.

We need more water, some said, we need a newer, bigger unit some other said, and I said, we need a preheated supply of warm water feed.

Here's what I (along with those not in favor of the idea) expected to have happen. Sure, a little more of the hot water will get sucked into the air stream, which we want, but now instead of all this warm water drain waste, we'll have a drain waste that'll be double hot. BTU wise, a bigger loss.

And here's what spilled out of the machine on a hot water diet.

Oh there still was a waste, but it was now just a tiny trickle (mind you, input flow rates were not altered). This satisfied everyone that more humid air was created.

But, what was truly remarkable, is that the waste was not hot at all, it wasn't air-temperature hot either, IT WAS STONE COLD.

We were putting very hot water into a hot air stream and the resulting mix became cold, this with lots of evaporation. Before, we were putting cold water into a hot air stream and the result was nothing but warm waste and no steaming.

The key is phase change, when this happens, your BTU get robbed from you, right from under your nose, but first, you need to get the evaporation going - and for effective steam, this starts around 212F

Same thing with home heating steam, same thing with home air conditioning. This riddle is only a mystery by how powerful it is.

The science set for the Christmas gift sounds like a lot of fun.

Christian

gerry gill

hot water freezes faster

or more accuratley, previously heated water freezes faster than water that has not been heated..previously heated water is no longer chemically the same as non-heated water..its no longer apples for apples..if you think they are still the same, boil some water, then chill it in the refrigerator..hows it taste? like crap huh...because previously heated water is no longer the same as cold tap water..and i've done the experiments also..the hot water froze first.

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Techman

Which unfreezes faster?

Both sides of "which freezes faster?" seem to have valid points! So my question is "Which ice cools down my "Yukon Jack" faster ? Happy Holidays to ALL

Plumdog_2

best ice

It comes from a frozen Beaver Pond and adds a certain something special to the cocktail at the end of the day.

Dick Charland

My understanding is hot water with less entrained air will help the water freeze to a clearer less cloudy cube which is essential when looking into the glass to see if it is time to refill the glass.

Weezbo

make some ice cubes out of a dash of vodka in the water...

would be my best guess.