scholarly journals Discussion: “Pressure Drop and Liquid Film Thickness of Two-Phase Annular and Annular-Mist Flows” (Chien, Sze-Foo, and Ibele, W., 1964, ASME J. Heat Transfer, 86, pp. 89–96)

1964 ◽  
Vol 86 (1) ◽  
pp. 96-96
Author(s):  
H. N. McManus
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Film Thickness ◽  
Liquid Film ◽  
Liquid Film Thickness ◽  
Two Phase

Measurement of Liquid Film Thickness in Micro Tube Annular Flow

2010 ◽  
Author(s):  
Hiroshi Kanno ◽  
Youngbae Han ◽  
Yusuke Saito ◽  
Naoki Shikazono
Keyword(s):  
Heat Transfer ◽  
Film Thickness ◽  
Liquid Film ◽  
Annular Flow ◽  
Liquid Film Thickness ◽  
Phase Flow ◽  
Two Phase ◽  
Micro Scale ◽  
Film Model ◽  
Annular Film

Heat transfer in micro scale two-phase flow attracts large attention since it can achieve large heat transfer area per density. At high quality, annular flow becomes one of the major flow regimes in micro two-phase flow. Heat is transferred by evaporation or condensation of the liquid film, which are the dominant mechanisms of micro scale heat transfer. Therefore, liquid film thickness is one of the most important parameters in modeling the phenomena. In macro tubes, large numbers of researches have been conducted to investigate the liquid film thickness. However, in micro tubes, quantitative information for the annular liquid film thickness is still limited. In the present study, annular liquid film thickness is measured using a confocal method, which is used in the previous study [1, 2]. Glass tubes with inner diameters of 0.3, 0.5 and 1.0 mm are used. Degassed water and FC40 are used as working fluids, and the total mass flux is varied from G = 100 to 500 kg/m2s. Liquid film thickness is measured by laser confocal displacement meter (LCDM), and the liquid-gas interface profile is observed by a high-speed camera. Mean liquid film thickness is then plotted against quality for different flow rates and tube diameters. Mean thickness data is compared with the smooth annular film model of Revellin et al. [3]. Annular film model predictions overestimated the experimental values especially at low quality. It is considered that this overestimation is attributed to the disturbances caused by the interface ripples.

scholarly journals ANALYSIS OF INTERFACIAL AND MASS TRANSFER EFFECTS ON FORCED CONVECTION IN GAS-LIQUID ANNULAR TWO-PHASE FLOW

2004 ◽  
Vol 3 (1) ◽  
pp. 45
Author(s):  
E. Nogueira ◽  
B. D. Dantas ◽  
R. M. Cotta
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Film Thickness ◽  
Liquid Film ◽  
Liquid Film Thickness ◽  
Phase Flow ◽  
Transfer Effects ◽  
Two Phase ◽  
Transfer Rates ◽  
Interface Waves

In a gas-liquid annular two-phase flow one of the main factors influencing the determination of heat transfer rates is the average thickness of the liquid film. A model to accurately represent the heat transfer in such situations has to be able of determining the average liquid film thickness to within a reasonable accuracy. A typical physical aspect in gas-liquid annular flows is the appearance of interface waves, which affect heat, mass and momentum transfers. Existing models implicitly consider the wave effects in the momentum transfer by an empirical correlation for the interfacial friction factor. However, this procedure does not point out the difference between interface waves and the natural turbulent effects of the system. In the present work, the wave and mass transfer effects in the theoretical estimation of average liquid film thickness are analyzed, in comparison to a model that does not explicitly include these effects, as applied to the prediction of heat transfer rates in a thermally developing flow situation.

scholarly journals Analytical Solutions of Heat Transfer and Film Thickness with Slip Condition Effect in Thin-Film Evaporation for Two-Phase Flow in Microchannel

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Ahmed Jassim Shkarah ◽  
Mohd Yusoff Bin Sulaiman ◽  
Md. Razali bin Hj Ayob
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Film Thickness ◽  
Liquid Film ◽  
Two Phase Flow ◽  
Current Model ◽  
Liquid Film Thickness ◽  
Phase Flow ◽  
Two Phase ◽  
Analytical Results

Physical and mathematical model has been developed to predict the two-phase flow and heat transfer in a microchannel with evaporative heat transfer. Sample solutions to the model were obtained for both analytical analysis and numerical analysis. It is assumed that the capillary pressure is neglected (Morris, 2003). Results are provided for liquid film thickness, total heat flux, and evaporating heat flux distribution. In addition to the sample calculations that were used to illustrate the transport characteristics, computations based on the current model were performed to generate results for comparisons with the analytical results of Wang et al. (2008) and Wayner Jr. et al. (1976). The calculated results from the current model match closely with those of analytical results of Wang et al. (2008) and Wayner Jr. et al. (1976). This work will lead to a better understanding of heat transfer and fluid flow occurring in the evaporating film region and develop an analytical equation for evaporating liquid film thickness.

scholarly journals Dynamics and effective distance of gas–liquid two-phase swirling flow induced by vortex tools

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401879961 ◽  
Author(s):  
Zhao Zhang ◽  
Ruiquan Liao ◽  
Jie Liu
Keyword(s):  
Pressure Drop ◽  
Film Thickness ◽  
Liquid Film ◽  
Swirling Flow ◽  
Flow Behavior ◽  
Helix Angle ◽  
Liquid Film Thickness ◽  
Liquid Ratio ◽  
Effective Distance ◽  
Two Phase

Based on the mechanistic model of the two-phase swirling annular flow behavior, a calculation method for the effective distance of vortex tool is obtained by taking Kelvin–Helmholtz instability into account. The rationality of the proposed method is validated by comparing the predicted liquid film thickness and pressure under non-swirling flow with the commonly used correlations. Then, the influences of gas–liquid ratio, helix angle, and hub diameter of vortex tool on the liquid film thickness, pressure drop, and effective distance have been analyzed. Results show that the presence of the vortex tool causes the decrease in the liquid film thickness and increase in the pressure drop. The liquid film thickness increases gradually as the helix angle and the hub diameter increase, and the larger helix angle results in smaller pressure drop. The effective distance increases with an increase in the gas–liquid ratio and decreases with an increase in helix angle and hub diameter. A sudden decrease occurs when the helix angle exceeds 60°. The gas–liquid ratio and helix angle are more dominant factors than the hub diameter on the liquid film thickness, pressure drop, and effective distance.

scholarly journals Interfacial waviness during condensation heat transfer

2021 ◽  
Vol 2116 (1) ◽  
pp. 012014
Author(s):  
A Berto ◽  
P Lavieille ◽  
M Azzolin ◽  
S Bortolin ◽  
M Miscevic ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Film Thickness ◽  
Liquid Film ◽  
Transfer Coefficient ◽  
Liquid Film Thickness ◽  
Condensation Heat Transfer ◽  
Internal Diameter ◽  
Transfer Coefficients ◽  
Two Phase

Abstract Heat transfer coefficients and liquid film thickness have been measured during convective condensation inside a 3.4 mm internal diameter channel. Condensation tests have been run with refrigerant R245fa during vertical downflow at mass velocity equal to 50 kg m-2 s-1 and 100 kg m-2 s-1. The test section is composed of two heat exchangers for the measurement of the heat transfer coefficient connected by means of a glass tube designed for the visualization of the two-phase flow patterns and for the measurement of the liquid film thickness. The liquid film thickness is determined by coupling a shadowgraph technique and chromatic confocal measurements. The measured values of heat transfer coefficient and liquid film thickness are reported and analysed together to investigate the effect of waves on the condensation heat transfer mechanisms.

Characteristics of the Liquid Film and Pressure Drop in Horizontal, Annular, Two-phase Flow Through Round, Square and Triangular Tubes

2004 ◽  
Vol 126 (5) ◽  
pp. 807-817 ◽  
Author(s):  
Timothy A. Shedd ◽  
Ty A. Newell
Keyword(s):  
Pressure Drop ◽  
Film Thickness ◽  
Liquid Film ◽  
Friction Velocity ◽  
Thickness Measurement ◽  
Secondary Flows ◽  
Liquid Film Thickness ◽  
Two Phase ◽  
Flow Through ◽  
Film Thickness Measurement

A unique set of liquid film thickness and pressure drop data has been obtained for horizontal, annular flow of air and water through round, square and triangular tube using a noninvasive, optical liquid film thickness measurement system. In the square and triangular tubes, the liquid film was thinned in the corners, indicating an effect of turbulent secondary flows in these geometries. In addition, when the film thickness is nondimensionalized using a friction velocity based on the total pressure drop, it is found that virtually all the data lie below h+=35 and that dryout occurs at approximately h+=5. The two-phase friction factor for the annular flows examined in all the tubes can be correlated using the Lockhart–Martinelli parameter, Xtt, when adjustments are made for the hydraulic diameters of the nonround tubes.

scholarly journals ANALYSIS OF INTERFACIAL AND MASS TRANSFER EFFECTS ON FORCED CONVECTION IN GAS-LIQUID ANNULAR TWO-PHASE FLOW

2004 ◽  
Vol 3 (1) ◽  
Author(s):  
E. Nogueira ◽  
B. D. Dantas ◽  
R. M. Cotta
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Film Thickness ◽  
Liquid Film ◽  
Liquid Film Thickness ◽  
Phase Flow ◽  
Transfer Effects ◽  
Two Phase ◽  
Transfer Rates ◽  
Interface Waves

In a gas-liquid annular two-phase flow one of the main factors influencing the determination of heat transfer rates is the average thickness of the liquid film. A model to accurately represent the heat transfer in such situations has to be able of determining the average liquid film thickness to within a reasonable accuracy. A typical physical aspect in gas-liquid annular flows is the appearance of interface waves, which affect heat, mass and momentum transfers. Existing models implicitly consider the wave effects in the momentum transfer by an empirical correlation for the interfacial friction factor. However, this procedure does not point out the difference between interface waves and the natural turbulent effects of the system. In the present work, the wave and mass transfer effects in the theoretical estimation of average liquid film thickness are analyzed, in comparison to a model that does not explicitly include these effects, as applied to the prediction of heat transfer rates in a thermally developing flow situation.

scholarly journals Two-Phase Region Effect on Film Condensation on an Inclined Plate Embedded in a Porous Medium

2020 ◽  
Vol 78 (2) ◽  
pp. 67-84
Author(s):  
Yee Lee Yeu ◽  
Alexander Gorin
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Porous Media ◽  
Film Thickness ◽  
Liquid Film ◽  
Phase Region ◽  
Liquid Film Thickness ◽  
Film Condensation ◽  
Two Phase ◽  
Region Effect

Film condensation in a porous medium has been receiving increasing attention due to its wide range of heat transfer applications. Some examples of these practical applications are distillation, drying technology, geothermal energy, cooling towers, heat exchangers, and air conditioning. One of the characteristic features of film condensation in porous media is the formation of a two-phase zone separating the liquid film and the vapour zone due to capillary pressure. In this paper, a physico-mathematical model of liquid film condensation on a surface embedded in a porous medium with a two-phase region effect is developed and presented. The model is based on momentum and continuity equations as applied to the liquid film and the two-phase flow region supplemented with the Darcy flow assumption and assumptions on the Leverette J-function and the saturation behaviour near the edge of the liquid film. The developed model allows a simple analytical solution to the problem in distinction to semi-analytical and numerical solutions published by different authors. From the model developed, it shows that the presence of the two-phase region decreases the liquid film thickness. By taking the capillary effects into consideration results in higher heat transfer and condensation rates due to the decrease in the liquid film thickness. The presented model yields good agreement when compared to the theoretical results and experimental data by other authors. The developed model addresses the fundamental concepts of phase transition in porous media which can effectively find applications in many areas.

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