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.

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.

Effect of Tube Geometry and Curvature on Film Condensation in the Presence of a Noncondensable Gas

2014 ◽  
Vol 7 (1) ◽  
Author(s):  
Huijun Li ◽  
Wenping Peng ◽  
Yingguang Liu ◽  
Chao Ma
Keyword(s):  
Heat Transfer ◽  
Film Thickness ◽  
Liquid Film ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Liquid Film Thickness ◽  
Film Condensation ◽  
Tube Surface ◽  
Noncondensable Gas ◽  
Tube Geometry

Based on the double boundary layer theory, a generalized mathematical model was developed to study the distributions of gas film, liquid film, and heat transfer coefficient along the tube surface with different geometries and curvatures for film condensation in the presence of a noncondensable gas. The results show that: (i) for tubes with the same geometry, gas film thickness, and liquid film thickness near the top of the tube decrease with the increasing of curvature and the heat transfer rate increases with it. (ii) For tubes with different geometries, one need to take into account all factors to compare their overall heat transfer rate including gas film thickness, liquid film thickness and the separating area. Besides, the mechanism of the drainage and separation of gas film and liquid film was analyzed in detail. One can make a conclusion that for free convection, gas film never separate since parameter A is always positive, whereas liquid film can separate if parameter B becomes negative. The separating angle of liquid film decreases with the increasing of curvature.

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 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.

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