Local thickness and wave velocity measurement of wavy films with a chromatic confocal imaging method and a fluorescence intensity technique

Lel, V. V.; Al-Sibai, Faruk; Leefken, Ansgar; Renz, Ulrich

doi:10.1007/s00348-005-0020-x

Cited by 103 publications

(66 citation statements)

References 23 publications

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“…Observations from experiments (Nogueira et al 2006) and numerical simulations Dukler & Bergelin (1952) 1500 < N f < 9000 Lel (2.21) Lel et al (2005) 40 < N f < 9000 Karapantsios (2.22) Karapantsios & Karabelas (1995) 9000 < N f < 44 000 Brown (2.23) Brown (1965) laminar film and N f > 120 Kang (2.24) Kang et al (2010) 10 < N f < 450 Cubic Brown (2.25) and (2.26) new model laminar film (Zheng et al 2007;Feng 2008) indicate that this distance depends on the Reynolds number (equivalently, on N f ) and that the length required for the film to develop becomes longer as inertia becomes more important. Sena Esteves & Guedes de Carvalho (1993) determine an expression for Z .…”

Section: (D) the Development Of The Falling Filmmentioning

confidence: 99%

“…Lel et al 2005;Nogueira et al 2006). Nusseldt (1916) presents a theoretical analysis of the forces acting on an element of a viscous liquid, falling under gravity, in a film in which the fluid flow is laminar.…”

Section: (B) Falling Liquid Filmsmentioning

confidence: 99%

“…The implicit nature of equation (2.10) limits its practicality, and several experimental studies have sought to determine a more practical correlation for film thickness. Karapantsios et al (1989), Lel et al (2005) and Zhou et al (2009) summarize data from several studies, which use a number of different working fluids and experimental designs. The various datasets, taken together, cover the Reynolds number range 10 Re f 15 000.…”

Section: (B) Falling Liquid Filmsmentioning

confidence: 99%

“…Bugg & Saad 2002;Nogueira et al 2006). There is also a large body of previous work (summarized in Karapantsios et al 1989;Lel et al 2005;Zhou et al 2009) that describes the behaviour of falling liquid films in general (i.e. not specifically associated with the rise of Taylor bubbles).…”

Section: Introductionmentioning

confidence: 99%

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The thickness of the falling film of liquid around a Taylor bubble

et al. 2011

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We present the results of laboratory experiments that quantify the physical controls on the thickness of the falling film of liquid around a Taylor bubble, when liquid-gas interfacial tension can be neglected. We find that the dimensionless film thickness l (the ratio of the film thickness to the pipe radius) is a function only of the dimensionless parameter N f = r gD 3 /m, where r is the liquid density, g the gravitational acceleration, D the pipe diameter and m the dynamic viscosity of the liquid. For N f 10, the dimensionless film thickness is independent of N f with value l ≈ 0.33; in the interval 10 N f 10 4 , l decreases with increasing N f ; for N f 10 4 film thickness is, again, independent of N f with value l ≈ 0.08. We synthesize existing models for films falling down a plane surface and around a Taylor bubble, and develop a theoretical model for film thickness that encompasses the viscous, inertial and turbulent regimes. Based on our data, we also propose a single empirical correlation for l (N f ), which is valid in the range 10 −1 < N f < 10 5 . Finally, we consider the thickness of the falling film when interfacial tension cannot be neglected, and find that film thickness decreases as interfacial tension becomes more important.

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Section: (D) the Development Of The Falling Filmmentioning

confidence: 99%

Section: (B) Falling Liquid Filmsmentioning

confidence: 99%

Section: (B) Falling Liquid Filmsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The thickness of the falling film of liquid around a Taylor bubble

et al. 2011

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“…Lel et al [19] performed point measurements with high temporal resolution and accuracy of film thickness and interfacial wave velocity using a confocal lens technique and compared it to a fluorescence intensity method, and reported satisfactory agreement. Further, Moran et al [20] made local measurements of the velocity profile within the liquid film as hydrodynamic waves travel down the film surface, and found that for large waves the velocity profiles were significantly different to Nusselt theory [21].…”

Section: Case Study I: Heated Falling Filmsmentioning

confidence: 99%

Heat transfer augmentation in unsteady conjugate thermal systems – Part II: Applications

Mathie

Nakamura

Markides

2013

International Journal of Heat and Mass Transfer

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Many energy conversion and other thermal-fluid systems exhibit unsteady convective heat exchange. In such systems, generic spatiotemporal variations in the flow give rise to variations in the heat flux for a given fluid-solid temperature difference, which can be interpreted as spatiotemporal fluctuations of the instantaneous heat transfer coefficient. These variations can lead to unsteady conjugate heat transfer, in which the exchanged heat flux arises from an interaction between the bulk fluid temperature and the temperature in the solid. Further, the nonlinear coupling between the fluctuating temperature differences and the heat transfer coefficient can lead to an effect we refer to as augmentation, which quantitatively describes the ability of a particular arrangement to have a different time-mean heat flux from the product between the mean heat transfer coefficient and the mean temperature difference across the fluid. It is important to be able to understand and to model in a simple framework the effects of the material properties, the geometry and the character of the heat transfer coefficient on the thermal response of the fluid-solid system, and consequently to predict the overall heat transfer performance of these systems. This paper, which follows on from its predecessor (Mathie and Markides, 2012a), is concerned with the phenomenon of augmentation in simple, one-dimensional, unsteady and conjugate fluid-solid systems. A simple semi-analytical one-dimensional model of heat transfer with a time-varying heat transfer coefficient, which was presented in Mathie and Markides (2012a), is applied herein to two different paradigm problems. Such a model can be an important tool in the design of improved heat exchangers and thermal insulation, through for example, the novel selection of materials to exploit these augmentation effects. The first flow considered is a thin, wavy fluid film flowing over a heated plate. This film flow exhibits a periodic fluctuation in the heat transfer coefficient, that is linked to the wavy interfacial deformations of free surface of the liquid film. The second flow considered concerns the heat transfer behind a backwards-facing step, which exhibits broadband fluctuations in the heat transfer coefficient due to the flow separation and turbulence behind * Corresponding author.

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New insight and experimental study of ineffective void in hydrodynamic performance of countercurrent‐flow packing column

Xu,

Gao,

Gao

et al. 2024

AIChE Journal

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Extensive experimental research and hydrodynamic models have been proposed to guide the design of superior packings. However, most research has concentrated on the effective void (ε − H) of packing while ignoring the ineffective void (ε − H − HL), which causes discrepancies in hydrodynamic performance compared to actual observations. This study evaluated the hydrodynamic performance under diverse conditions considering the liquid holdup (H), pressure drop (ΔP), and gas flooding velocity (uf). A novel approach to hydrodynamic model construction is introduced by incorporating an ineffective void. The results indicate that at a constant hold‐up area, liquid flow (L) and viscosity (μ) significantly influence liquid hold up, moderated by the gas velocity in the flooding area. The pressure drop rises as the viscosity, gas flow rate, and liquid flow rate increase. Notably, a considerable pressure drop initiates flooding at the bottom of the absorber. Elevated liquid flow rates and viscosities correlate with higher ineffective void values (HL) in the packing column. At low gas flow rates, the gas flow rate marginally affects HL values. However, after the flooding point was achieved, the values of HL rapidly increased as the gas flow rate increased. Moreover, a linear relationship emerges between the liquid holdup and HL, as evidenced by the consistent variation in the liquid holdup and the F‐factor. Utilizing the ineffective void yields a more accurate fit for the experimental data, reducing the average absolute relative deviation to 10.2%, 7.4%, and 10.8%, respectively.

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Local thickness and wave velocity measurement of wavy films with a chromatic confocal imaging method and a fluorescence intensity technique

Cited by 103 publications

References 23 publications

The thickness of the falling film of liquid around a Taylor bubble

The thickness of the falling film of liquid around a Taylor bubble

Heat transfer augmentation in unsteady conjugate thermal systems – Part II: Applications

New insight and experimental study of ineffective void in hydrodynamic performance of countercurrent‐flow packing column

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