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Author Topic: Does arctic ocean also show a indication of Mpemba effect?  (Read 2072 times)

peterlvmeng

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Does arctic ocean also show a indication of Mpemba effect?
« on: November 12, 2019, 02:05:33 AM »
We know the Mpemba effect describes the phenomenon that temperature of hotter water decrease more fast than cool water with surrounding temperature belows 0 degree. The arctic ocean also shows a fast freezing and now the Dmi 80N anamoly also shows a dramatic decrease. It is interesting. I know Mpemba effect is controversial right now and hardly to be verified sometimes. But it is really interesting.

kassy

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Re: Does arctic ocean also show a indication of Mpemba effect?
« Reply #1 on: November 12, 2019, 01:52:12 PM »
How many buoys would we need to tease that out?

Just looking at the refreeze maps i would say no though.

And: Schaatser Max Dohle onderzocht het effect bij vorst in de buitenlucht. Daarbij bleek dat een glas koud water bij herhaling sneller bevroor dan een glas warm water. Onder natuurlijke omstandigheden kon het Mpemba-effect dus niet worden aangetoond.

Ice skater Max Dohle researched the effect in outdoor frost. A glass of cold water always freezes quicker then a glass of warm water. Under natural conditions the Mpemba effect could not be demonstrated.

https://nl.wikipedia.org/wiki/Mpemba-effect

I don´t think it is relevant because the arctic water is as warm or cold as it is and then freezes when it gets cold enough. No Chuckchi flash freeze in sight. 

Also you are never going to see 42 and 18 C water next to eachother in the arctic. The Mpenda effect is temperature dependent and the ranges of arctic water are probably outside the zone (for now  ;) ).

See graph at the top here:
https://en.wikipedia.org/wiki/Mpemba_effect

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kassy

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Re: Does arctic ocean also show a indication of Mpemba effect?
« Reply #2 on: July 09, 2022, 06:29:24 PM »
I just ran across an interesting article which delves deeper into this. Interestingly enough it turns out that Mpemba´s initial observation actually relates to ice: 

Quote
“My name is Erasto B Mpemba, and I am going to tell you about my discovery, which was due to misusing a refrigerator.” Thus begins a 1969 paper in the journal Physics Education in which Mpemba described an incident at Magamba Secondary School in Tanzania when he and his classmates were making ice cream.

Space was limited in the students’ refrigerator, and in the rush to nab the last available ice tray, Mpemba opted to skip waiting for his boiled-milk-and-sugar concoction to cool to room temperature. An hour and a half later, his mixture had frozen into ice cream, whereas that of a classmate who, also in a rush, had skipped the boiling and put his room-temperature milk-and-sugar mixture directly into the refrigerator, remained a thick liquid slurry. When Mpemba asked his physics teacher why this occurred, he was told, “You were confused, that cannot happen.”

Later, Osborne came to visit Mpemba’s high-school physics class. He recalled the teenager raising his hand and asking, “If you take two beakers with equal volumes of water, one at 35°C and the other at 100°C, and put them into a refrigerator, the one that started at 100°C freezes first. Why?” Intrigued, Osborne had one of his technicians at the University College in Dar es Salaam test this observation and found evidence for the effect that bears Mpemba’s name. Still, Osborne concluded that the tests were crude and more sophisticated experiments would be needed to figure out what might be going on.

Then it gets a bit more complicated:

Quote
When Zhiyue Lu of the University of North Carolina read about the Mpemba effect in middle school, he snuck into an oil refinery in the Shandong province of China where his mother worked and used precision lab equipment to measure temperature as a function of time in a sample of water (he ended up supercooling the water without it freezing). Later, while studying nonequilibrium thermodynamics as a graduate student, he tried to reframe his approach to the Mpemba effect. “Is there any thermodynamic rule that will forbid the following: Something starting further away from the final equilibrium that would approach equilibrium faster than something starting from close?” he asked.

Lu met Oren Raz, who now studies nonequilibrium statistical mechanics at the Weizmann Institute of Science in Israel, and they began developing a framework to investigate the Mpemba effect generally, not just in water. Their 2017 paper in the Proceedings of the National Academy of Sciences modeled the random dynamics of particles, showing that, in principle, there are nonequilibrium conditions under which the Mpemba effect and its inverse could occur. The abstract findings suggested that the components of a hotter system, by virtue of having more energy, are able to explore more possible configurations and therefore discover states that act as a sort of bypass, allowing the hot system to overtake a cool one as both drop toward a colder final state.

https://www.theatlantic.com/science/archive/2022/07/mpemba-effect-hot-water-freezes-fast/661525/

It is far from solved in general or for water.

Musing about the tests above it would be interesting to test this with a mix of water and crushed ice. Maybe try some with different salt levels. You can start with just freezing time. If anyone finds anything just let us now. :)
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weatherdude88

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Re: Does arctic ocean also show a indication of Mpemba effect?
« Reply #3 on: July 09, 2022, 07:17:26 PM »
The physical molecular process for the Mpemba effect has been well known for years. Here is a paper for your education:

https://pubs.acs.org/doi/abs/10.1021/acs.jctc.6b00735