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Post by Lokifan on Jan 10, 2017 20:38:16 GMT
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Post by GTCGreg on Jan 10, 2017 21:18:42 GMT
Noooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo Please, Not again. This isn't just beating a dead horse, it's beating the dried up, crumbling, mummified bones of a dead horse. |
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Post by the light works on Jan 11, 2017 2:12:57 GMT
if the original was done in an ice cream freezer, it may be that it was an ice bath model of freezer - maybe under THOSE circumstances, the hot ice cream mix starts the ice bath melting, which then absorbs heat more efficiently through better contact with the ice cream drum.
in short, perhaps rather than it being the hot start that makes it freeze faster, it is the difference it creates in the ice bath that causes the mpemba effect. remember that typically rock salt is added to the ice bath to cause the ice to melt, thus causing it to absorb heat more rapidly.
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Post by silverdragon on Jan 11, 2017 10:14:35 GMT
I have looked at this...
To My Understanding, in that, you may want to try and look at this yourself before you take my word on it.
Hot water may take "less time" to freeze than cold than you expect, but.
It takes more energy.
Yeah, you read that right. And it has to be a no-shirt-sherlock thing that cant be dismantled there, hasnt it?..
You will exhaust more energy getting boiling liquid to freezing point than you will with cold water..
Its only a matter of simples physics, if it takes {x} joules of energy to take water from [y] degree Celsius to [z]degC over [t] amount of time, the the reverse be true, it takes x to get from Z to Y over the same amount of T, and therefore, if there is in either case a greater difference in Y and Z, either T takes longer or X is increased.
Its the same as a running man tackling a hill, he may do it in less time than a walking man, sure, but he will be more knackered at the top than the walking man.
This is assuming the walking man and the running man are of equivalent states of fitness...
So if you have a reasonably decent freezer, one that can sense "warmth" and kick in the cooling process, if it kicks in to "Super freeze" like mine does and does double the amount of usual work on tickover, yes, Hot water has the potential to absorb the extra cooling power ...
Just dont expect that on tickover consumption of energy.
It has to take energy to cool, there is no such thing as "free" when it comes to heat transfer by mechanical process is there?.
Back to the article on strong and weak hydrogen bonds, yes, there is still a lot to be leant about bonds in chemicals, we still dont know for sure everything about non Newtonian fluids do we?.
I am going to leave that to someone with a degree in particle physics to work it out....
And I doubt someone doing an article in "Science alert" internet magazine has that kind of qualifications?..
As in, yeah, I know, we still dont know, there is more we know we dont know than there is we know we are working on.
BTW, as always, if someone fact checks my "Simples science" above and find it has errors, let me know, I will edit as required...
But as far as I know, its "Ballpark" in the right area for what you call the thousand yard view of non qualified scientists, and pretty much on the ball for us here?..
And, of course, If anyone has the time to do the full half hour lecture tour, go ahead, I am interested.
Just that article is an article for the sake of an article, I dont think it has any breaking science in it does it?.
Just someone who noted that putting his hot fluid in a freezer and the freezer probably kicked into overdrive to work the temp back down to acceptable levels, he got a super-freeze...
I am wondering how my own freeze would react.
1] by inhibiting the super-freeze function and letting it go at its own pace on normal freeze functions.
2] letting the freezer "react" to a sudden rise in temp and kicking in its own reactive super-freeze. [which stops at -18degC being the mark I have set for the freeze to go down to.
3] selecting super-freeze [to -24degC] right from the start before I even put the hot liquid in, and letting it have that 1hr overdrive run.
I am suspecting the order I have put above would replicate the time resultant frames needed to get to "Ice cream" stage?..
However, this I would be interested in.
Setting up a scientific [taking notes] experiment of an isolated small refrigeration unit with a set speed on the heat exchange that measures the power requirements with a temp sensor in the middle of the subject "ice cream" mass, to measure the length of time taken to freeze from cold produce around 5degC "Fridge" temp, produce at say room temp of 22degC max, and Hot boiling liquid.
Expected results are that the power requirements of the Hot boiling liquid are going to be rather a lot...
Room temp will be more than Fridge temp.
I am wondering if indeed the Boiling temp may be "faster" over time to achieve Frozen temp than room temp...
I doubt it, but, on my expected results, as always, failure is indeed an option.
Of course the power requirements to do that may be "Interesting", especially if they aint Linear between the temp points.
As in, if it isnt a directly proportional X amount of power to each Y of degC?..
If it is, indeed, not the case, than this directly supports the ideal that some chemical bonds are stronger/weaker dependant on temp, and that a faster change of temp can alter the power requirements to do so.
Is the reverse true.
Would "Flash boiling" a pan of water take less or more power than slow rises in temp?.
Testing would be a immersed heating coil inside a insulated "kettle" that has say 1,000 joules of energy in enough water to go from room temp to just below boiling for that expected amount of water, and that energy put through it at different rates from slow to fast from the same start point of temp and noting the resultant temp afterwards.
Repeat again from "frozen" at say -10degC and see if anything changes.
Anyone following this train of thought or have I completely de-railed somewhere and got lost in a siding in some remote Welsh railway yard?..
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Post by the light works on Jan 11, 2017 15:15:26 GMT
I am still thinking that given how long this has been around, Mpemba was using a traditional ice cream freezer, in which you place the ice cream tub in the outer tub, and fill the gap with ice cubes; then sprinkle salt on the ice to chemically force melting.
at this point it goes from the "hot water freezes faster" myth to the "fast chilling your beer" myth.
the test demonstrated that burying the beer in ice definitely was less effective than sinking it in a salted-ice-water slurry.
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Post by ponytail61 on Jan 11, 2017 16:15:19 GMT
I am still thinking that given how long this has been around, Mpemba was using a traditional ice cream freezer, in which you place the ice cream tub in the outer tub, and fill the gap with ice cubes; then sprinkle salt on the ice to chemically force melting. at this point it goes from the "hot water freezes faster" myth to the "fast chilling your beer" myth. the test demonstrated that burying the beer in ice definitely was less effective than sinking it in a salted-ice-water slurry. When I think of ice cream freezers I have two different things in mind. There is the display/dip freezer that you serve out of and there is also a commercial hardening/storing freezer. The dip cabinets should be kept at 0 to +5 deg. while the hardening freezers should be -10 to -20 and go all the way to -40 |
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Post by the light works on Jan 11, 2017 16:51:33 GMT
I am still thinking that given how long this has been around, Mpemba was using a traditional ice cream freezer, in which you place the ice cream tub in the outer tub, and fill the gap with ice cubes; then sprinkle salt on the ice to chemically force melting. at this point it goes from the "hot water freezes faster" myth to the "fast chilling your beer" myth. the test demonstrated that burying the beer in ice definitely was less effective than sinking it in a salted-ice-water slurry. When I think of ice cream freezers I have two different things in mind. There is the display/dip freezer that you serve out of and there is also a commercial hardening/storing freezer. The dip cabinets should be kept at 0 to +5 deg. while the hardening freezers should be -10 to -20 and go all the way to -40 I'm thinking of this kind.  |
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Post by GTCGreg on Jan 11, 2017 17:49:43 GMT
As TLW already pointed out in his first post on this thread, this phenomena always comes back to the same physical property, and that is the thermal interface between the water and the sounding colder area that will be receiving the thermal energy from the water. If warmer water temperature somehow modifies that interface by lowering its resistance to thermal energy transfer, then the water will get colder faster. That's what happens in TLW's explanation of adding salt to the ice surrounding the cream in an ice cream maker. It doesn't lower the temperature of the ice. It partially melts the ice creating a liquid heat transfer media so the cream can get not colder, but colder faster. This is also what happens with the so called mpemba effect. The warmer cream causes some of the ice to melt and that liquid-ice mush can transfer heat faster than just ice alone. Thus the cream freezes faster. This really isn't a mystery, nor is it rocket science.
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Post by the light works on Jan 12, 2017 1:00:33 GMT
As TLW already pointed out in his first post on this thread, this phenomena always comes back to the same physical property, and that is the thermal interface between the water and the sounding colder area that will be receiving the thermal energy from the water. If warmer water temperature somehow modifies that interface by lowering its resistance to thermal energy transfer, then the water will get colder faster. That's what happens in TLW's explanation of adding salt to the ice surrounding the cream in an ice cream maker. It doesn't lower the temperature of the ice. It partially melts the ice creating a liquid heat transfer media so the cream can get not colder, but colder faster. This is also what happens with the so called mpemba effect. The warmer cream causes some of the ice to melt and that liquid-ice mush can transfer heat faster than just ice alone. Thus the cream freezes faster. This really isn't a mystery, nor is it rocket science. which explains why physicists can't figure it out. |
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Post by GTCGreg on Jan 12, 2017 2:01:07 GMT
As TLW already pointed out in his first post on this thread, this phenomena always comes back to the same physical property, and that is the thermal interface between the water and the sounding colder area that will be receiving the thermal energy from the water. If warmer water temperature somehow modifies that interface by lowering its resistance to thermal energy transfer, then the water will get colder faster. That's what happens in TLW's explanation of adding salt to the ice surrounding the cream in an ice cream maker. It doesn't lower the temperature of the ice. It partially melts the ice creating a liquid heat transfer media so the cream can get not colder, but colder faster. This is also what happens with the so called mpemba effect. The warmer cream causes some of the ice to melt and that liquid-ice mush can transfer heat faster than just ice alone. Thus the cream freezes faster. This really isn't a mystery, nor is it rocket science. which explains why physicists can't figure it out. I think there a plenty of physicists that have it figured out. You just don't hear from them because they have better things to do. Besides, what reporter want's to report on boring science when they can report on exciting false science. Time to move along. There is no great mystery or magic going on here. Just boring physics. |
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Post by the light works on Jan 12, 2017 2:09:52 GMT
which explains why physicists can't figure it out. I think there a plenty of physicists that have it figured out. You just don't hear from them because they have better things to do. Besides, what reporter want's to report on boring science when they can report on exciting false science. Time to move along. There is no great mystery or magic going on here. Just boring physics. that was to be read in a "well there's your problem" inflection. |
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Post by silverdragon on Jan 12, 2017 10:06:33 GMT
I am still thinking that given how long this has been around, Mpemba was using a traditional ice cream freezer, in which you place the ice cream tub in the outer tub, and fill the gap with ice cubes; then sprinkle salt on the ice to chemically force melting. at this point it goes from the "hot water freezes faster" myth to the "fast chilling your beer" myth. the test demonstrated that burying the beer in ice definitely was less effective than sinking it in a salted-ice-water slurry. Bugger.... trust ME to overthink the idea. To me a freezer is a big cabinet in the corner of the room that hums slightly. Its a matter of semantics to say at this point that "What you call an ice-cream freezer is what I call an ice cream maker" isnt it?.. But in saying that also, if it was placed in a cabinet freezer, on a glass shelf, the condensation on the outside of the cream container would create a frozen bridge between the cold shelf and the tub, thus allowing a greater surface area of the tub to conduct cold into the tub.... so yeah, partial melting works both ways, in that it allows a greater area of conduction of heat. This is just physics isnt it?.. |
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Post by silverdragon on Jan 12, 2017 10:08:10 GMT
which explains why physicists can't figure it out. I think there a plenty of physicists that have it figured out. You just don't hear from them because they have better things to do. Besides, what reporter want's to report on boring science when they can report on exciting false science. Time to move along. There is no great mystery or magic going on here. Just boring physics. Not for me... It makes me think better knowing there is more than I first realised. |
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Post by GTCGreg on Jan 12, 2017 14:35:38 GMT
I already have this one figured out. And have for a long time. Yet every few years, it resurfaces as a new mystery of science. It's no mystery and I'm tired of hearing about it.
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Post by the light works on Jan 12, 2017 14:46:40 GMT
I already have this one figured out. And have for a long time. Yet every few years, it resurfaces as a new mystery of science. It's no mystery and I'm tired of hearing about it. I, on the other hand, had not yet heard the original theory was based on making ice cream. |
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Post by GTCGreg on Jan 12, 2017 16:15:03 GMT
I already have this one figured out. And have for a long time. Yet every few years, it resurfaces as a new mystery of science. It's no mystery and I'm tired of hearing about it. I, on the other hand, had not yet heard the original theory was based on making ice cream. Yep, that's what started the madness. And it wasn't even water. |
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