A numerical study of mass transfer from laminar liquid films

Zhou, Guangzhao; Prosperetti, Andréa

doi:10.1017/jfm.2020.587

Cited by 9 publications

(7 citation statements)

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“…Those regions include: • The crest of the main wave keeps a lower temperature than the rest of the film over a relatively long downstream distance. A vortex (in the moving frame of reference, attached to the wave) is known to induce a liquid circulation inside the crest (Roberts and Chang 2000;Miyara 2000;Albert et al 2014;Zhou and Prosperetti 2020). This would explain the rather uniform temperature observed in this region.…”

Section: Heat Transfer Enhancement By the Mixingmentioning

confidence: 95%

“…• Another mechanism for the enhancement of heat and mass transfers relates to the variable film thickness (Kapitza and Kapitza 1965). When undulations pass through a liquid film, the mean thickness of the film becomes smaller than the thickness of the flat laminar film transporting the same flow rate (Zhou and Prosperetti 2020). This results from the fact that the velocity profile is not linear with the distance to the wall in a falling liquid film.…”

Section: Introductionmentioning

confidence: 99%

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Temperature distribution in the cross section of wavy and falling thin liquid films

et al. 2021

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Wave instabilities of falling liquid films are crucial in many applications to enhance heat and mass transfer. Despite the importance of this issue, the interplay between the heat transfer and the wavy dynamics of falling films is still not completely understood. To get more insight, a planar laser-induced fluorescence technique has been developed for imaging the temperature distribution in the cross section of thin liquid films (approximately 0.5-1 mm thick), which are falling down an inclined heated surface. This study reports on the implementation of this imaging technique. It also discusses its advantages and limitations for the investigation of the heat transfer in the falling liquid films. Two-dimensional flow conditions and regular waves are considered for the reconstruction of a complete temperature field in the waves. Measurements provide new understanding of the wave ability to generate mixing within the film. Temperature maps reveal preferential regions where mixing occurs first, before eventually spreading to the rest of the film if the wave amplitude and the travel distance are large enough. The increase in the heat transfer coefficient is directly related to the internal mixing observed in the temperature images.

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Section: Heat Transfer Enhancement By the Mixingmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Temperature distribution in the cross section of wavy and falling thin liquid films

et al. 2021

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“…Since the literature contains only a small number of suitable examples, it has been necessary to carry out additional simulations by a method that we now briefly describe. A more extensive exposition is available in a recent paper [24].…”

Section: Numerical Simulationsmentioning

confidence: 99%

“…1, while the second case was used for validation in an earlier paper Ref. [24]. For all these cases we performed our own simulations to facilitate the extraction of the wavelength and attenuation of the capillary waves.…”

Section: Comparisonmentioning

confidence: 99%

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Capillary waves on a falling film

Zhou

Prosperetti

2020

Phys. Rev. Fluids

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This paper shows that the wavelength and rate of spatial attenuation of the small ripples accompanying the large waves that form on a liquid film flowing down an inclined plane are dictated by the requirement that their velocity equal the velocity of the large wave. For this purpose numerical simulations of film flow are carried out and validated by comparison with published work. The wavelength and rate of spatial attenuation of the computed capillary waves are shown to equal, to an excellent approximation, the corresponding quantities obtained from an approximate form of the Orr-Sommerfeld equation in which the phase velocity is set equal to the velocity of the large waves. Thus the overall structure of the falling film waves is similar to that encountered in many other problems exhibiting a wave-hierarchical structure, such as waves in dusty or reacting gases, hydraulic jumps, undular bores, and others.

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