Modeling of Two-Phase Flow Structure Evolution in Subcooled Nucleate Convective Boiling With Coupling of Bubble-Tracking and Two-Fluid Models

2008 ◽  
Author(s):  
Ivo Kljenak ◽  
Bosˇtjan Koncˇar ◽  
Luka Sˇtrubelj ◽  
Borut Mavko
Keyword(s):  
Fluid Model ◽  
Three Dimensional ◽  
Vertical Channel ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Structure Evolution ◽  
Two Phase ◽  
Convective Boiling ◽  
Tracking Model ◽  
Two Fluid

A model of subcooled nucleate boiling flow in a vertical channel at low-pressure conditions is proposed. The model consists of a three-dimensional bubble-tracking model and a two-dimensional two-fluid model which are coupled off-line. By taking into account dynamic phenomena (liquid flow, bubble motion and interaction) and thermal phenomena (liquid heating, bubble nucleation and condensation), the model is able to simulate the gradual evolution of void fraction profiles along the boiling channel. The model is assessed by simulating experiments that were performed at Purdue University (USA) at atmospheric pressure in a vertical annulus with a central heating rod.

Simulation of Subcooled Nucleate Boiling in a Vertical Annulus With Coupling of Bubble-Tracking and Two-Fluid Models: Further Comparison With Experimental Results

2006 ◽  
Author(s):  
Ivo Kljenak ◽  
Bosˇtjan Koncˇar ◽  
Borut Mavko
Keyword(s):  
Fluid Model ◽  
Three Dimensional ◽  
Vertical Channel ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Experimental Results ◽  
Tracking Model ◽  
Two Fluid Model ◽  
Vertical Annulus ◽  
Two Fluid

A model of subcooled nucleate boiling flow in a vertical channel at low pressure conditions that was developed earlier is further validated by comparison of simulations with experimental results from Purdue University (USA). The model consists of a three-dimensional bubble-tracking model and a two-dimensional two-fluid model which are coupled off-line. By taking into account dynamic phenomena (liquid flow, bubble motion and interaction) and thermal phenomena (liquid heating, bubble nucleation and condensation), the model is able to simulate the gradual evolution of void fraction profiles along the boiling channel.

Nucleate Boiling Flow Simulation With Coupling of Eulerian and Lagrangian Methods

2005 ◽  
Author(s):  
Bosˇtjan Koncˇar ◽  
Ivo Kljenak ◽  
Borut Mavko
Keyword(s):  
Model Simulation ◽  
Fluid Model ◽  
Nucleate Boiling ◽  
Homogeneous Distribution ◽  
Lagrangian Simulation ◽  
Radial Profiles ◽  
Boiling Flow ◽  
Tracking Model ◽  
Two Fluid Model ◽  
Two Fluid

Subcooled boiling flow was simulated by combining the two-fluid model of the CFX-4.4 code and a Lagrangian bubble-tracking model. At present, both models are coupled “off-line” via the local bubble Sauter diameter. The two-fluid model simulation with the CFX-4.4 code provides local values of turbulent kinetic energy field of the liquid phase, which is used as an input for the bubble-tracking model. In the bubble-tracking model, vapour is distributed in the liquid in the form of individually tracked bubbles. The result of the Lagrangian simulation is a non-homogeneous distribution of local Sauter diameter, which is used in the two-fluid model to predict the interfacial forces and interfacial transfer rates of mass and heat transfer. The coupled approach requires a few iterations to obtain a converged solution. The results of the proposed approach were validated against boiling flow experiments from the literature. A good agreement between measured and calculated radial profiles of void fraction and bubble diameter was obtained.

Simplification of Ensemble Averaged Two-Phase Flow with Heat and Mass Transfer Equations for Boiling in a Channel

2008 ◽  
Vol 273-276 ◽  
pp. 616-621
Author(s):  
Hikmet Ş. Aybar ◽  
Mohsen Sharifpur
Keyword(s):  
Two Phase Flow ◽  
Fluid Model ◽  
Three Dimensional ◽  
Phase Flow ◽  
Governing Equations ◽  
Ensemble Averaging ◽  
Two Phase ◽  
Transfer Equations ◽  
Two Fluid Model ◽  
Two Fluid

Generation of vapor and predication of its behavior is an important problem in many industries. In this study, the three dimensional governing equations for turbulence two-phase flow are derived using ensemble averaging two fluid model. The governing equations are simplified by a heuristic approach based on boiling data, and the equations are used to obtain the parameters for each phase along the channel. A computer program is written for the simplified one-dimensional equations, and the results are compared with experimental data.

Analysis of Two-Phase Cavitating Flow with Two-Fluid Model Using Integrated Boltzmann Equations

2013 ◽  
Vol 5 (05) ◽  
pp. 607-638 ◽  
Author(s):  
Shuhong Liu ◽  
Yulin Wu ◽  
Yu Xu ◽  
Hua-Shu Dou
Keyword(s):  
Turbulence Model ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Three Dimensional ◽  
Cavitating Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Pump Sump ◽  
Two Fluid Model ◽  
Two Fluid

AbstractIn the present work, both computational and experimental methods are employed to study the two-phase flow occurring in a model pump sump. The two-fluid model of the two-phase flow has been applied to the simulation of the three-dimensional cavitating flow. The governing equations of the two-phase cavitating flow are derived from the kinetic theory based on the Boltzmann equation. The isotropic RNGk — ε — kcaturbulence model of two-phase flows in the form of cavity number instead of the form of cavity phase volume fraction is developed. The RNGk—ε—kcaturbulence model, that is the RNGk — eturbulence model for the liquid phase combined with thekcamodel for the cavity phase, is employed to close the governing turbulent equations of the two-phase flow. The computation of the cavitating flow through a model pump sump has been carried out with this model in three-dimensional spaces. The calculated results have been compared with the data of the PIV experiment. Good qualitative agreement has been achieved which exhibits the reliability of the numerical simulation model.

Simplified two-group two-fluid model for three-dimensional two-phase flow Computational Fluid Dynamics for vertical upward flow

2018 ◽  
Vol 108 ◽  
pp. 503-516 ◽  
Author(s):  
Takashi Hibiki ◽  
Joshua P. Schlegel ◽  
Tetsuhiro Ozaki ◽  
Shuichiro Miwa ◽  
Somboon Rassame
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Three Dimensional ◽  
Phase Flow ◽  
Upward Flow ◽  
Two Phase ◽  
Two Fluid Model ◽  
Two Fluid

Simulation of Subcooled Nucleate Boiling in a Vertical Tube With a Bubble-Tracking Model

1999 ◽  
Author(s):  
Ivo Kljenak ◽  
Borut Mavko
Keyword(s):  
Three Dimensional ◽  
Cylindrical Tube ◽  
Nucleate Boiling ◽  
Vertical Tube ◽  
Bubble Nucleation ◽  
Core Region ◽  
Turbulent Dispersion ◽  
Radial Profiles ◽  
Bubble Interaction ◽  
Tracking Model

Abstract A three-dimensional bubble-tracking model was developed to simulate subcooled nucleate boiling in a heated vertical cylindrical tube. The behavior of the liquid-vapor system results from motion, interaction and heat transfer mechanisms prescribed mostly at the level of individually-tracked vapor bubbles. The model takes into account bubble nucleation and liquid heating caused by wall heat flux, bubble sliding on tube walls, bubble condensation in the low-temperature tube core region, bubble interaction through wake drift, bubble collisions and coalescence, bubble radial migration towards the tube core region, and turbulent dispersion in the liquid phase. The agreement between calculated void fraction and liquid temperature radial profiles along the flow with experimental results from other authors is promising.

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