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1

New analysis of experimental data of the hydrodynamic liquid film around jet zone on horizontal plate

Elmahi Abdelbaki, Baki Touhami, Tebbal Mohamed

Archive of Mechanical Engineering

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2021

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LXVIII, nr 4

435--448

EN

Optimization of cooling systems is of major importance due to the economy of cooling water and energy in thermal installations in the industry. The hydrodynamic study of the film is a prerequisite for the study of the intensity of the heat transfer during the cooling of a horizontal plate by a liquid film. This experimental work made it possible to quantify the hydrodynamic parameters by a new approach, a relation linking the thickness of the film to the velocity was found as a function of the geometrical and hydrodynamic characteristics of the sprayer. A new statistical approach has been developed for the measurement of the velocity, the liquid fluid arriving at the edge of the plate and having velocity V is spilled out like a projectile. The recovering of the liquid in tubes allowed us to quantify flow rates for different heights positions relative to the plate, statistical processing permitted us to assess the probable velocity with a margin of error.

2

Formation and rupture of gas film of antibubble

Bai Lichun, Sun Jinguang, Zeng Zhijie, Ma Yuhang, Bai Lixin

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2020

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nr 23(1)

91--104

EN

The formation and rupture of gas film in the process of formation, rupture and coalescence of antibubbles were investigated by high-speed photography. It was found that a gas film will appear and wrap a droplet when the droplet hit a layer of liquid film or foam before impacting the gas-liquid interface. The gas film may survive the impact on the gas-liquid interface and act as the gas film of an antibubble. A multilayer droplet will be formed when the droplet hits through several layer of liquid films, and a multilayer antibubble will be formed when the multilayer droplet impact a gas-liquid interface or a single layer of foam on the liquid surface. The way to generate antibubbles by liquid films will undergo the formation and rupture of gas films. The coalescence of two antibubbles, which shows a similar merging process of soap bubbles, also undergo the rupture and formation of gas films. The rupture of gas film of antibubble caused by aging and impact is also discussed.

3

Added mass of rising bubble approaching to solid wall – numerical studies

Zawala Jan

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 6

41--50

EN

The numerical approach for determination of influence of deformation of the gas bubble (radius 0.74 mm) on added mass coefficient in (i) steady-state conditions and (ii) during approach to the horizontal wall, is proposed. It is shown that the bubble deformation can be tuned numerically (within the range 1.06 - 1.88) via proper variations of the Laplace pressure, without changing the bubble radius. Influence of the bubble deformation on its motion parameters is discussed and compared to theoretical predictions regarding the bubble drag coefficient and Reynolds number. Moreover, the approach allowing determination of the added mass of rising bubble, on the basis of variations in fluid kinetic energy, is described. It is shown that calculated added mass variations strongly depends on the interplay between (i) the bubble deformation ratio and (ii) its rising velocity. This effect is especially important for added mass of a gas bubble approaching a solid wall, because it can affect the kinetics of drainage of the separating liquid film formed under dynamic conditions, when Re >> 1.

4

Some remarks on attachment of a gas bubble to another phase both immersed in water

Kowalczuk P. B., Drzymala J.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 1

147--154

EN

In this paper the importance of definition of hydrophobicity and aquaoleophilicity in terms of contact angle as well as the properties of water films in flotation and oil agglomeration were briefly presented. It was shown that the hysteresis of contact angle for a considered system depends on the way of measurement and geometry of the system due to the presence of other that excess pressure and capillary forces and buffering properties of the capillary force. It was suggested that, the measured advancing and receding contact angles should be, when possible, recalculated into the Young (rest, equilibrium) contact angle. It was discussed that quartz is not a good model of hydrophilic surface because its contact angle with a gas phase in water is not zero and that a spontaneous attachment between highly hydrophobic materials such as hydrocarbons and Teflon in dynamic system, such as flotation, does not occur.

5

Dry patch formation in diabatic annular two-phase flows

Anglart H.

Journal of Power Technologies

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2014

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Vol. 94, nr 5

85--95

EN

Conditions for the formation of a stable dry patch in vertical annular two-phase flows in heated channels are investigated. An analytical model of the force balance for the leading edge of the liquid film is developed. In addition to surface tension, evaporation thrust and capillary forces, the model includes the effect of turbulence, the pressure gradient and the interfacial shear stress. Numerical evaluations are performed to validate the model and to indicate the importance of various factors on the dry patch stability and on the resulting minimum wetting rate of the liquid film. The analyses indicate that good agreement with measurements is obtained in the case of a stagnant patch formed on liquid film flowing down a vertical surface. It is shown that for low and moderate mass flow rate of the gas phase in vertical co-current annular flow, the force balance is dominated by the stagnation and the shear stress forces. With growing mass flow rate of the gas phase, the pressure gradient and the interfacial shear stress become increasingly important. As a result, in accordance with measurements, the predicted minimum flow rate of the liquid film at which the patch is re-wetted decreases.

6

Wyroby hydroizolacyjne typu folia w płynie stosowane w budownictwie. Cz. 2. Błędy i braki w wymaganiach oraz w badaniach laboratoryjnych

Pałasz A.

Izolacje

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2013

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R. 18, nr 10

18--20

PL

W artykule przedstawiono analizę poprawności metod badawczych i wymagań dotyczących produkcji oraz wprowadzania do obrotu folii w płynie. Opisano zawarte w dokumentach normatywnych błędy oraz zaproponowano sposoby ich poprawienia.

EN

The article presents an analysis of the correctness of test methods for requirements regarding production and introduction of liquid film products to the market. Errors found in the norms are described and methods of their correction are proposed.

7

Grubość filmów cieczy przy pierścieniowym przepływie cieczy dwufazowej z gazem

Brandt A.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2011

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z. 98

13-14

EN

The liquid film thickness in the three-phase flow in vertical pipes have been investigated. The reduce film thickness of liquid medium in function of Reynolds number in sprinkler conditions have been measured. The comparison of experimental results with different methods of calculating the reduce liquid film thickness have been considered.

8

Heat transfer in a liquid film over an unsteady stretching surface with the effects of viscous dissipation, thermal radiation and non-uniform heat source in the presence of external magnetic field

Abel. M. S., Tawade J. V.

International Journal of Applied Mechanics and Engineering

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2010

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Vol. 15, no 4

967-992

EN

This paper presents a mathematical analysis of an MHD flow and heat transfer to a laminar liquid film from a horizontal stretching surface. The flow of a thin fluid film and subsequent heat transfer from the stretching surface is investigated with the aid of similarity transformation. The transformation renders it possible to reduce the unsteady boundary layer equations to a system of non-linear ordinary differential equations. A numerical solution of the resulting nonlinear differential equations which agrees well with the analytic solution, is obtained by the efficient shooting technique. The effects of boundary layer thickness on various physical parameters such as the unsteadiness parameter S and magnetic parameter Mn, Prandtl number Pr, Eckert number Ec, thermal radiation parameter Nr and non-uniform heat source/sink parameters which determine the temperature profiles, the heat transfer coefficient are tabulated and plotted in figures. It is shown that the heat fluxes from the liquid to the elastic sheet decreases with S for […] and increases with S for […]. Some important findings reported in this work reveal that the combined effect of thermal radiation and non-uniform heat source have significant impact on controlling the rate of heat transfer in the boundary layer region.

9

Optoelectronic measuring system for assessment of the annular two-phase gas-very viscous liquid flow

Witczak S., Czernek K.

Turbulence : international journal

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2005

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Vol. 11

25-33

EN

The paper presents the results of tests and theoretical considerations on assessment of hydrodynamics of a cocurrent annular downward flow of a very viscous liquid and a gas in vertical pipes. Measurement methods have been presented; special attention was paid to the optoelectronic measuring system. Systematic of flow patterns has been discussed and some chosen quantities characterizing flowing liquid films of high viscosity have been described.

10

Wpływ struktury powierzchni na wymianę ciepła w aparatach z cienkowarstewkowym spływem cieczy

Poniewierski M., Środulska-Krawczyk M.

Inżynieria Chemiczna i Procesowa

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2001

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T. 22, z. 3D

1181--1186

PL

Przeprowadzono badania wymiany ciepła od ścianki rury do spływającego grawitacyjnie filmu cieczy. W celu zwiększenia intensywności wymiany ciepła wprowadzono wymuszoną turbulizację spływającej cieczy. Opracowano równania korelacyjne opisujące zależność współczynnika wnikania ciepła α od Г, wybranych parametrów fizyko-chemicznych (η, λ, ρ, c,p, σ) i geometrycznych opisujących elementy turbu- lizujące film cieczy.

EN

Some examinations of heat transfer from tube wall to thin film down gravitationally were carried out. To intensify the heat transfer, the turbulence of thin film was forced. Some correlations describing an effect of process (Г). physico-chemical (η, λ, ρ, c,p, σ) and geometrical (characterising the devices causing the film turbulence) parameters were derived.

11

Analytical model of heat transfer in films on rotating discs

Mikielewicz J., Mikielewicz D.

Archives of Thermodynamics

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1999

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Vol. 20, no 3/4

105-118

EN

This paper examines the performances of thin liquid films impinging normally on rotating discs. It is found that very high heat transfer coefficients can be achieved at modest disc speeds with water-like liquids. The model considers the influence of the heat transfer boundary conditions, Reynolds number and Prandtl number. The comparisons with experimental data show very good qualitative consistency.