The Mpemba effect

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Summary:

Mpemba effect conditions

Main Question or Discussion Point

What are the conditions needed to occur the effect?
 
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  • #2
russ_watters
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What are the conditions needed to occur the effect?
The answer to that isn't clear. It isn't clear whether there are any conditions that would reliably enable the effect to occur. And it is certainly only possible if one of the parameters of the experiment you might expect to be constant actually isn't. My best speculation is you might be able to cause it to occur if you have a large surface area to volume ratio in a low humidity environment, which causes a significant fraction of the hot water to evaporate, enabling the remaining water to cool and freeze faster than if the full amount were present.
 
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  • #3
ZapperZ
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Summary:: Mpemba effect conditions

What are the conditions needed to occur the effect?
This forum has had a large number of threads on this topic, in addition to the numerous hits one can obtained in a google search.

Zz.
 
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This forum has had a large number of threads on this topic
Really? I was looked for before post but failed.Could you please show me some?
 
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Borek
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Really? I was looked for before post but failed.Could you please show me some?
On PC in the right upper corner of the window there is a "search" command. Using it to look for "mpemba" yields four pages of hits.
 
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The answer to that isn't clear. It isn't clear whether there are any conditions that would reliably enable the effect to occur. And it is certainly only possible if one of the parameters of the experiment you might expect to be constant actually isn't.
I agree.According to Newton's law of cooling, if we set as surrounding temperature To=0 => ΔT=T-To=T, during the cooling of a material body the rate of temperature decrease (cooling rate=q) is proportional to the temperature (T): dQ=mcdT= κAΔΤdt = κATdt => dT/dt=hT=q
where t is the time & h is the heat transfer coefficient.The greater the value of h, the higher is the cooling rate, q so more likely to occur Mpemba effect: this is my aspect claimed in my published article.Heat transfer coefficient is dependent upon the physical properties of the water (such as m:mass,c: specific heat) and the physical situation (such as A:interface area,κ: thermal diffusivity).However, h is affected by much many factors such as the container’s shape and material and the air circulation within the freezer, among others.Thus, the Mpemba effect is hard to predict and is not observed in every instance.
 
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Borek
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this is my aspect claimed in my published article
So you have come here pretending you ask questions, while in fact you are trying to promote your work?

Sneaky and rude if you ask me.
 
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  • #8
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So you have come here pretending you ask questions, while in fact you are trying to promote your work?
Sneaky and rude if you ask me.
No.Since I got tired of reading other's articles in these threads,I think it is legitimate.
 
  • #9
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Sneaky and rude, +1.

The paper is in a predatory or near-predatory journal, and it shows a complete ignorance of thermodynamics. It asks us to consider two otherwise identical containers of water at the same temperature and different entropy. Obviously nonsense.
 
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The paper is in a predatory or near-predatory journal, and it shows a complete ignorance of thermodynamics. It asks us to consider two otherwise identical containers of water at the same temperature and different entropy. Obviously nonsense.
This is a peer reviewed journal member of DOAJ.Also,my perspective is accepted by Prof.Martin Chaplin.I can provide the link,if you permitt.
 
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This may not be the thread to ask in, but:

I had never heard of the 'Mpemba effect' until this morning. I was aware of claims that hot water froze faster than cold water. As someone who has put significant effort into cooling beer as quickly as possible, I can say for certain:
Some places in a refrigerator (or freezer) are subject to much higher air speeds than others. This is true (mostly) while the compressor is running (evap fan), and the precise situation depends on the construction of the freezer, the distribution of things in the freezer, the defrost cycle, insulation... When the circ fan is not running, insulation performance and (other) thermal mass dominate the situation.

Why is the 'Mpemba effect' not obviously an artifact of the (incorrect) asssumption that 2 spots in a freezer are subjected to the same cooling?
 
  • #12
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This is a peer reviewed journal
Really? And none of the peers noticed that it begins with a thermodynamic impossibility?
 
  • #13
Borek
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First of all: per forum rules, we don't discuss original research.

Thread locked.
 
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