Analytical Simulation of Annular Two-Phase Flow Considering the Four Involved Mass Transfers

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Zahra Baniamerian ◽  
Ramin Mehdipour ◽  
Cyrus Aghanajafi
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Fluid Flow ◽  
Analytical Model ◽  
Two Phase Flow ◽  
Experimental Models ◽  
Analytical Models ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase

Efficiently employing two-phase flows for cooling objectives requires comprehensive knowledge of their behavior in different conditions. Models, capable of predicting heat transfer and fluid flow trends in this area, are of great value. Numerical/analytical models in the literature are one-dimensional models involving with many simplifying assumptions. These assumptions in most cases include neglecting some mechanisms of mass transfer in two-phase flows. This study is devoted to developing an analytical two-dimensional model for simulation of fluid flow and mass transfer in two-phase flows considering the all mass transfer mechanisms (entrainment, evaporation, deposition and condensation). The correlation employed for modeling entrainment in this study, is a semiempirical correlation derived based on physical concept of entrainment phenomenon. Emphasis is put on the annular flow pattern of liquid vapor two-phase flow since this regime is the last encountered two-phase regime and has a higher heat transfer coefficient among other two-phase flow patterns. Attempts are made to employ the least possible simplification assumptions and empirical correlations in the modeling procedure. The model is then verified with experimental models of Shanawany et al., Stevanovic et al. and analytical model of Qu and Mudawar. It will be shown, considering pressure variations in both radial and axial directions along with applying our semiempirical entrainment correlation has improved the present analytical model accuracy in comparison with the accuracy of available analytical models.

Two-Phase Flow Heat and Mass Transfer Model Construction and Experiment Study of the Fuel Evaporation Progress

2012 ◽  
Vol 614-615 ◽  
pp. 174-180
Author(s):  
Bo Yun Liu ◽  
Jin Yun Pu ◽  
Xiang Lie Yi
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Two Phase Flow ◽  
Time Dependent ◽  
Transfer Model ◽  
Phase Flow ◽  
Two Phase ◽  
Dependent Behavior ◽  
Mass Evaporation ◽  
Hot Surface

As for the time-dependent behavior of the fuel heat and mass evaporation transfer progress on hot surface,consider the convective mass transfer and heat transfer, the liquid-gas two-phase flow of continuous heat transfer model was studied. By the dimensionless transform, the time-dependent behavior of the concentration distribution and the temperature field was obtained. The result of n-Heptanes evaporation transfer progress on hot surface experiment is consistent with the academic model.

A Study of Transient Heat Transfer in a Vertical Two-Phase Flow During Blowdown of a Pipeline

2001 ◽  
Author(s):  
S. Bautista-Fragoso ◽  
Yuri V. Fairuzov
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Conjugate Heat Transfer ◽  
Two Phase Flow ◽  
Pipe Wall ◽  
Mathematical Formulation ◽  
Local Thermal Equilibrium ◽  
Phase Flow ◽  
Two Phase ◽  
Drift Flux Model

Abstract A numerical model of transient two-phase flow and conjugate heat transfer in a vertical pipeline is presented in the present paper. The drift-flux model is used to describe the fluid flow in the pipeline. The modeling of transient conjugate heat transfer is based on a mathematical formulation in which the pipe wall and the fluid are assumed to be in local thermal equilibrium. The effect of the thermal capacity of the pipe wall is taken into account by an additional term in the energy equation for the fluid flow. Such an approach allows significant simplifying the problem and reducing the computer running time. Numerical simulations of blowdown of a pipeline/riser system were performed. The effect of the pipe wall on the flow behavior was investigated.

Analysis of Heat Transfer and Fluid Flow in Two-Phase Thermosyphon Loop with Minichannels

2016 ◽  
Vol 831 ◽  
pp. 92-103 ◽  
Author(s):  
Henryk Bieliński ◽  
Jaroslaw Mikielewicz
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
General Model ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Phase Flow ◽  
Two Phase ◽  
Considerable Impact ◽  
Flow Condensation ◽  
Computer Processor

The present paper offers an analysis of heat transfer and fluid flow in two phase thermosyphon loop with minichannels. A one-dimensional model of two-phase flow and heat transfer in a closed thermosyphon loop with minichannels was examined. The created general model is based on mass, momentum, and energy balances in the evaporators, rising tube, condensers and the falling tube. The separate two-phase flow model is used in calculations. The numerical results obtained for the selected heater and cooler using the general model of thermosyphon loop indicate that the mass flux increases with increasing length of the heated section and decreases with increasing length of the cooled section of the loop. It was found that the heat transfer coefficient for flow boiling and flow condensation in the steady state increases with increasing heat flux in the heater and cooler with minichannels, respectively. The design and configuration of heaters and coolers has a considerable impact on the efficiency of thermosyphon loop. These factors make it possible to optimize the computer processor cooling.

Analytical and Numerical Simulation of the Two Phase Flow Heat Transfer in the Vent and Scavenge Pipes of the Clean Engine Demonstrator

2008 ◽  
Author(s):  
Michael Flouros
Keyword(s):  
Heat Transfer ◽  
Two Phase Flow ◽  
Numerical Models ◽  
Environmentally Friendly ◽  
The Other ◽  
Analytical Models ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Heat ◽  
The Impact

Advanced aircraft engine development dictates high standards of reliability for the lubrication systems, not only in terms of the proper lubrication of the bearings and the gears, but also in terms of the removal of the large amounts of the generated heat. Heat is introduced both internally through the rotating hardware and externally through radiation, conduction and convection. In case where the bearing chamber is in close proximity to the engine’s hot section, the external heat flux may be significant. This is, for example, the case when oil pipes pass through the turbine struts and vanes on their way to the bearing chamber. There; the thermal impact is extremely high, not only because of the hot turbine gases flowing around the vanes, but also because of the hot cooling air which is ingested into the vanes. The impact of this excessive heat on the oil may lead to severe engine safety and reliability problems which can range from oil coking with blockage of the oil tubes to oil fires with loss of part integrity, damage or even failure of the engine. It is therefore of great importance that the oil system designer is capable of predicting the system’s functionality. As part of the European Research program EEFAE (Efficient and Environmentally Friendly Aero Engine), the project CLEAN (Component vaLidator for Environmentally-friendly Aero-eNngine) [1], [2] was initiated with the goal to develop future engine technologies. Within the scope of this program, MTU Aero Engines has designed the lubrication system and has initiated an investigation of the heat transfer in the scavenge and vent tubes passing through the high thermally loaded TCF (Turbine Center Frame). The objective was to evaluate analytical and numerical models for the heat transfer into the air and oil mixtures and benchmark them. Three analytical models were investigated. A model which was based on the assumption that the flow of air and oil is a homogeneous mixture which was applied on the scavenge flow. The other two models assumed annular two-phase flows and were applied on the vent flows. Additionally, the two phase flow in the scavenge and vent pipes was simulated numerically using the ANSYS CFX package. The evaluation of the models was accomplished with test data from the heavily instrumented test engine with special emphasis on the TCF. Both the analytical and the numerical models have demonstrated strengths and weaknesses. The homogeneous flow model correlation and the most recent correlation by Dr. Busam for vent flows have demonstrated very good agreement between test and computed results. On the other hand the numerical analysis produced remarkable results, however at the expense of significant modeling and computing efforts. This particular work is unique compared to published investigations since it was conducted in a real engine environment and not in a simulating rig. Nevertheless, research in two-phase flow heat transfer will continue in order mitigate any deficiencies and to further improve the correlations and the CFD tools.

A Mechanistic Model for Predicting Heat and Mass Transfer in Vertical Two-Phase Flow

Volume 3 ◽  
2004 ◽  
Author(s):  
Siamack A. Shirazi ◽  
Ebrahin Al-Adsani ◽  
John R. Shadley ◽  
Edmund F. Rybicki
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Two Phase Flow ◽  
Mechanistic Model ◽  
Intermittent Flow ◽  
Phase Flow ◽  
Empirical Correlations ◽  
Transfer Coefficients ◽  
Two Phase

The mass transfer coefficient plays an important role in predicting corrosion rates. Using similarities between heat and mass transfer mechanisms, a mechanistic model is proposed to predict heat and mass transfer coefficients for two-phase flow in vertical pipes. The mechanistic model is evaluated by using water-air heat transfer experimental data obtained from the literature. The mechanistic model is also compared with commonly used empirical correlations. In comparison with available heat transfer correlations, the mechanistic model performs very well for vertical annular flow, bubbly flow and slug or intermittent flow that were considered. The mechanistic model is based on physics of two-phase flow and thus is expected to be more general than empirical correlations.

Theory study of gas–water relative permeability in roughened fractures

2018 ◽  
Vol 232 (24) ◽  
pp. 4615-4625 ◽  
Author(s):  
Gang Lei ◽  
Cai Wang ◽  
Zisen Wu ◽  
Huijie Wang ◽  
Weirong Li
Keyword(s):  
Porous Media ◽  
Analytical Model ◽  
Relative Permeability ◽  
Two Phase Flow ◽  
Fractured Reservoirs ◽  
Fractured Porous Media ◽  
Analytical Models ◽  
Phase Flow ◽  
Two Phase ◽  
Proposed Model

It has been shown that gas–water relative permeability in fracture or fractured porous media plays an important role in determination of flow characteristics for gas–water two-phase flow. The accurate prediction of gas–water two-phase flow in fracture or fractured media is hence highly important. In most recent analytical models for gas–water relative permeability in fracture, the fracture is conceptualized as smooth wall. Reliable characterization of roughened fracture surface is severely limited. The analytical models for gas–water two-phase relative permeability in roughened fracture are scarce, thus, it is desirable to develop an analytical model for gas–water relative permeability in fracture with roughened surface. The goal of this work is to present an analytical model for gas–water relative permeability in roughened fracture. The rough surface topography of roughened fracture can be addressed by fractal theory. In addition, the proposed model is modified by considering the influence of tortuosity to study the gas–water relative permeability in fractured porous media. The proposed gas–water relative permeability is found to be a function of the structural parameters of roughened fracture. The predictions of relative permeability by the proposed model have similar variation trend with available experimental data, which verifies the theoretical models. We also conduct several sensitivity studies. These proposed analytical models provides a more realistic representation of gas–water two-phase flow in roughened fracture and fractured porous media, and gives rise to more reliable gas–water relative permeability curves that can be used for analyzing gas–water two-phase flow characteristic in fractured reservoirs.

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