Laminar Filmwise Condensation on Horizontal Disk Embedded in Porous Medium With Suction at Wall

2008 ◽  
Vol 130 (7) ◽  
Author(s):  
Tong-Bou Chang
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Liquid Film ◽  
Mechanical Energy ◽  
Disk Surface ◽  
Darcy Number ◽  
Nonlinear Ordinary Differential Equation ◽  
Phase Zone ◽  
Two Phase ◽  
Suction Parameter

This study performs a theoretical investigation into the problem of two-dimensional steady filmwise condensation flow on a horizontal disk embedded in a porous medium layer with suction at the disk surface. The analysis considers the case of a water-vapor system and is based on typical values of the relevant dimensional and dimensionless parameters. Due to the effects of capillary forces, a two-phase zone is formed between the liquid film and the vapor zone. The minimum mechanical energy concept is employed to establish the boundary condition at the edge of the horizontal disk and the Runge–Kutta shooting method is used to solve the second-order nonlinear ordinary differential equation of the liquid film. It is found that the capillary force and wall suction effects have a significant influence on the heat transfer performance. Specifically, the results show that the dimensionless heat transfer coefficient depend on the Darcy number Da, the Jacob number Ja, the effective Rayleigh number Rae, the effective Prandtl number Pre, the suction parameter Sw, and the capillary parameter Boc.

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 Darcy-Brinkman free convection about a wedge and a cone subjected to a mixed thermal boundary condition

1992 ◽  
Vol 15 (4) ◽  
pp. 789-794 ◽  
Author(s):  
G. Ramanaiah ◽  
V. Kumaran
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Porous Medium ◽  
Heat Transfer Coefficient ◽  
Free Convection ◽  
Transformation Group ◽  
Darcy Number ◽  
Thermal Boundary Condition ◽  
High Porosity

The Darcy-Brinkman free convection near a wedge and a cone in a porous medium with high porosity has been considered. The surfaces are subjected to a mixed thermal boundary condition characterized by a parameterm;m=0,1,∞correspond to the cases of prescribed temperature, prescribed heat flux and prescribed heat transfer coefficient respectively. It is shown that the solutions for differentmare dependent and a transformation group has been found, through which one can get solution for anymprovided solution for a particular value ofmis known. The effects of Darcy number on skin friction and rate of heat transfer are analyzed.

Natural Convection Inside a Bidisperse Porous Medium Enclosure

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Arunn Narasimhan ◽  
B. V. K. Reddy
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Natural Convection ◽  
Volume Fraction ◽  
Solid Phase ◽  
Darcy Number ◽  
The Core ◽  
Side Walls ◽  
Porous Blocks ◽  
Rayleigh Numbers

Bidisperse porous medium (BDPM) consists of a macroporous medium whose solid phase is replaced with a microporous medium. This study investigates using numerical simulations, steady natural convection inside a square BDPM enclosure made from uniformly spaced, disconnected square porous blocks that form the microporous medium. The side walls are subjected to differential heating, while the top and bottom ones are kept adiabatic. The bidispersion effect is generated by varying the number of blocks (N2), macropore volume fraction (ϕE), and internal Darcy number (DaI) for several enclosure Rayleigh numbers (Ra). Their effect on the BDPM heat transfer (Nu) is investigated. When Ra is fixed, the Nu increases with an increase in both DaI and DaE. At low Ra values, Nu is strongly affected by both DaI and ϕE. When N2 is fixed, at high Ra values, the porous blocks in the core region have negligible effect on the Nu. A correlation is proposed to evaluate the heat transfer from the BDPM enclosure, Nu, as a function of Raϕ, DaE, DaI, and N2. It predicts the numerical results of Nu within ±15% and ±9% in two successive ranges of modified Rayleigh number, RaϕDaE.

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.

Heat Conduction Analysis on the Evaporator in Gravity Heat Pipe of Heavy Oil Wellbore

2014 ◽  
Vol 608-609 ◽  
pp. 991-995
Author(s):  
Wei Li ◽  
Xin Yuan Tian
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Heat Pipe ◽  
Nucleate Boiling ◽  
Liquid Pool ◽  
Transfer Model ◽  
Two Phase ◽  
Extra Energy ◽  
Phase Change Heat Transfer ◽  
Bottom To Top

A technology for using petroleum deposit’s energy and the principle of medium’s phase change heat transfer to make hollow rod into heat pipe, which transferred heat from bottom to top in wellbore by using it without extra energy is proposed. It can improve the temprature distribution of the fluid at the upper part of wellbore; therefore paraffin deposition and flocculation are improved. In this paper, heat transfer model of liquid film and liquid pool is established by means of the equation of N-S.Based on the principle of micro unit in liquid film’s thermal equilibrium and liquid pool’s heat transfer.By analying the heat transfer coeffcients of this two part,it was found out that gravity heat pipe had better heat transfer performance with increasing the length of liquid film in evaporator,improving the flow rate of inner steam and strengthening nucleate boiling of liquid pool,when the requirement of the continuous circulation of two-phase flow was achieved.

Numerical Investigation of Heat Transfer in Forced Convection in a Helical Pipe Filled With a Porous Medium

2005 ◽  
Author(s):  
Liping Cheng ◽  
Andrey V. Kuznetsov
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Saturated Porous Medium ◽  
Axial Flow ◽  
Darcy Number ◽  
Momentum Equation ◽  
Darcy Law ◽  
Helical Pipe ◽  
Fluid Saturated Porous Medium ◽  
Flow Inertia

This paper investigates numerically heat transfer in a helical pipe filled with a fluid saturated porous medium. The analysis is based on the full momentum equation for porous media that accounts for the Brinkman and Forchheimer extensions of the Darcy law as well as for the flow inertia. Numerical computations are performed in an orthogonal helical coordinate system. The effects of the Darcy number, the Forchheimer coefficient as well as the Dean and Germano numbers on the axial flow velocity, secondary flow, temperature distribution, and the Nusselt number are analyzed.

scholarly journals Numerical Simulation of Transient Free Convection Flow and Heat Transfer in a Porous Medium

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Rajesh Sharma ◽  
Anuar Ishak
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Differential Equations ◽  
Darcy Number ◽  
Convection Flow ◽  
Force Model ◽  
Moving Plate ◽  
Drag Forces ◽  
Flow And Heat Transfer ◽  
Momentum And Heat Transfer

The coupled momentum and heat transfer in unsteady, incompressible flow along a semi-infinite vertical porous moving plate adjacent to an isotropic porous medium with viscous dissipation effect are investigated. The Darcy-Forchheimer nonlinear drag force model which includes the effects of inertia drag forces is employed. The governing differential equations of the problem are transformed into a system of nondimensional differential equations which are solved numerically by the finite element method (FEM). The non-dimensional velocity and temperature profiles are presented for the influence of Darcy number, Forchheimer number, Grashof number, Eckert number, Prandtl number, plate velocity, and time. The Nusselt number is also evaluated and compared with finite difference method (FDM), which shows excellent agreement.

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