Mpemba Paradox
Numerical reproduction of observations confirms that water skin supersolidity enhances the local thermal diffusivity favoring heat diffusing outwardly in the liquid path. Analysis of experimental database reveals that O:H–O bond possesses memory to emit e
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Mpemba Paradox
• Mpemba effect integrates the energy “emission–conduction–dissipation” dynamics of the hydrogen bond in the “source–path–drain” cycle system. • O:H–O bond memory entitles water to emit energy at a rate proportional to its initial storage. • Water skin supersolidity favors outward heat diffusion by raising the local thermal diffusivity. • Non-adiabatic “source–drain” interface enables rapid heat dissipation, but convection, evaporation, frost, supercooling, and solutes contribute insignificantly.
Abstract Numerical reproduction of observations confirms that water skin supersolidity enhances the local thermal diffusivity favoring heat diffusing outwardly in the liquid path. Analysis of experimental database reveals that O:H–O bond possesses memory to emit energy at a rate depending on its initial storage. Unlike other usual materials that lengthen and soften all bonds when they are absorbing thermal energy, water performs abnormally at heating to lengthen the O: H nonbond and shorten the H–O covalent bond through interoxygen Coulomb coupling. Cooling does oppositely to release energy, like releasing a coupled pair of bungees with full recoverability, at a rate of history dependence. Being sensitive to the source volume, skin radiation, and the drain temperature, Mpemba effect proceeds only in the strictly non-adiabatic ‘source-path-drain’ cycling system for the heat “emission-conduction-dissipation” dynamics with a relaxation time that drops exponentially with the rise of the initial temperature of the liquid source.
11.1
Challenge: Why Does Warm Water Freeze Quickly?
The Mpemba effect [1–5] is the assertion that hot water freezes quicker than its cold, even though it must pass through the same lower temperature on the way to freezing. Figure 11.1 shows numerical reproduction of the measured (insets) initial-temperature θi dependence of the thermal relaxation θ(θi, t) profile and the temperature difference Δθ(θi, t) between the skin and the bulk of liquid water under identical experimental conditions (purity, volume, drain temperature, etc.) [6], which demonstrate the following:
© Springer Science+Business Media Singapore 2016 C.Q. Sun and Y. Sun, The Attribute of Water, Springer Series in Chemical Physics 113, DOI 10.1007/978-981-10-0180-2_11
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Mpemba Paradox
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Fig. 11.1 Numerical reproduction [7] of the measured (insets) initial-temperature and time dependence of a the θ(θi, t) [6] and b the skin-bulk temperature difference Δθ(θi, t) of water at cooling. Inset a shows cooling and freezing of 30 ml deionized water at θi = 25 and 35 °C in a glass beaker without cover or being mixed using magnetic stirring (Reprinted with permission from [7].)
(1) The liquid temperature θ drops exponentially with cooling time (t) until the transition from water to ice with a relaxation time τ that
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