The Interfacial Area Weighted Area-Averaged Gas Velocity Model for the Interfacial Area Transport Equation in the System Analysis Code

2021 ◽  
Author(s):  
Mengsi Shen ◽  
Meng Lin
Keyword(s):  
Experimental Data ◽  
Transport Equation ◽  
Interfacial Area ◽  
Theory Model ◽  
Gas Velocity ◽  
Two Phase ◽  
Interfacial Area Concentration ◽  
Interfacial Area Transport ◽  
Drift Flux Model ◽  
Interfacial Area Transport Equation

Abstract The interfacial area transport equation is a more accurate and stable way to compute the interfacial area concentration than the traditional empirical correlation in the two-phase two-fluid model. And among the parameters in the two-group interfacial area transport equation, the interfacial area concentration weighted area-averaged gas velocity is an important parameter to close the two-group area-averaged interfacial area transport equation in the system analysis code. However, there has been no theory model to compute the interfacial area concentration weighted area-averaged gas velocity until now. So this study established the theory model for two-group interfacial area concentration weighted area-averaged gas velocity based on the drift-flux model for the two-phase dispersed bubble flow. The experimental data were selected from the published literature, which include the detailed two-phase interfacial structure experimental data for the slug bubble flow. The interfacial area concentration weighted area-averaged gas velocity model predicted the selected experimental data well, which validated the developed model. Moreover, the difference between the interfacial area concentration weighted area-averaged gas velocity and the void weighted area-averaged gas velocity is clarified quantitatively for the first time. The theory model developed in this study can be improved and then be used to compute the interfacial area weighted area-averaged gas velocity because it includes the empirical parameter of conventional drift-flux model.

Interfacial Area Transport Equation and Implementation Into Two-Fluid Model

2009 ◽  
Vol 1 (1) ◽  
Author(s):  
Mamoru Ishii ◽  
Seungjin Kim ◽  
Xiaodong Sun ◽  
Takashi Hibiki
Keyword(s):  
Transport Equation ◽  
Fluid Model ◽  
Interfacial Area ◽  
Flow Conditions ◽  
Two Phase ◽  
Interfacial Area Concentration ◽  
Interfacial Area Transport ◽  
Interfacial Area Transport Equation ◽  
Two Fluid Model ◽  
Two Fluid

A dynamic treatment of interfacial area concentration has been studied over the last decade by employing the interfacial area transport equation. When coupled with the two-fluid model, the interfacial area transport equation replaces the flow regime dependent correlations for interfacial area concentration and eliminates potential artificial bifurcation or numerical oscillations stemming from these static correlations. An extensive database has been established to evaluate the model under various two-phase flow conditions. These include adiabatic and heated conditions, vertical and horizontal flow orientations, round, rectangular, annulus, and 8×8 rod-bundle channel geometries, and normal-gravity and reduced-gravity conditions. Currently, a two-group interfacial area transport equation is available and applicable to comprehensive two-phase flow conditions spanning from bubbly to churn-turbulent flow regimes. A framework to couple the two-group interfacial area transport equation with the modified two-fluid model is established in view of multiphase computational fluid dynamics code applications as well as reactor system analysis code applications. The present study reviews the current state-of-the-art in the development of the interfacial area transport equation, available experimental databases, and the analytical methods to incorporate the interfacial area transport equation into the two-fluid model.

Two-Fluid CFD Model of Adiabatic Air-Water Upward Bubbly Flow Through a Vertical Pipe With a One-Group Interfacial Area Transport Equation

2009 ◽  
Author(s):  
Deoras Prabhudharwadkar ◽  
Chris Bailey ◽  
Martin Lopez de Bertodano ◽  
John R. Buchanan
Keyword(s):  
Experimental Data ◽  
Transport Equation ◽  
Bubbly Flow ◽  
Interfacial Area ◽  
Correct Prediction ◽  
Interfacial Area Transport ◽  
One Dimensional ◽  
Interfacial Area Transport Equation ◽  
The One ◽  
Two Fluid

This paper describes in detail the assessment of the CFD code CFX to predict adiabatic liquid-gas two-phase bubbly flow. This study has been divided into two parts. In the first exercise, the effect of Lift Force, Wall Force and the Turbulent Diffusion Force have been assessed using experimental data from the literature for air-water upward bubbly flows through a pipe. The data used here had a characteristic near wall void peaking which was largely influenced by the joint action of the three forces mentioned above. The simulations were performed with constant bubble diameter assuming no bubble interactions. This exercise resulted in selection of the most appropriate closure form and closure coefficients for the above mentioned forces for the range of flow conditions chosen. In the second exercise, the One-Group Interfacial Area Transport equation was introduced in the two-fluid model of CFX. The interfacial area density plays important role in the correct prediction of interfacial mass, momentum and energy transfer and is affected by bubble breakup and coalescence processes in adiabatic flows. The One-Group Interfacial Area Transport Equation (IATE) has been developed and implemented for one-dimensional models and validated using cross-sectional area averaged experimental data over the last decade by various researchers. The original one-dimensional model has been extended to multidimensional flow predictions in this study and the results are presented in this paper. The paper also discusses constraints posed by the commercial CFD code CFX and the solutions worked out to obtain the most accurate implementation of the model.

CFD Simulations of Cap-Bubbly Two-Phase Flows Using Two-Group Interfacial Area Transport Equation

2011 ◽  
Author(s):  
Xia Wang ◽  
Xiaodong Sun
Keyword(s):  
Transport Equation ◽  
Fluid Model ◽  
Interfacial Area ◽  
Phase Flow ◽  
Two Phase ◽  
Interfacial Area Transport ◽  
Interfacial Area Transport Equation ◽  
Proposed Model ◽  
Two Fluid Model ◽  
Two Fluid

Knowledge of cap-bubbly flows is of great interest due to its role in understanding of flow regime transition from bubbly to slug or churn-turbulent flow. One of the key characteristics of such flows is the existence of bubbles in different sizes and shapes associated with their distinctive dynamic natures. This important feature is, however, generally not well captured by available two-phase flow models. In view of this, a modified two-fluid model, namely a three-field two-fluid model, is proposed. In this model, bubbles are categorized into two groups, i.e., spherical/distorted bubbles as Group-1 while cap/churn-turbulent bubbles as Group-2. A two-group interfacial area transport equation (IATE) is implemented to describe the dynamic changes of interfacial structure in each group, resulting from intra- and inter-group interactions and phase changes due to evaporation and condensation. Attention is also paid to the appropriate constitutive relations of the interfacial transfers due to mechanical and thermal non-equilibrium between different fields. The proposed three-field two-fluid model is used to predict the phase distributions of adiabatic air-water flows in a narrow rectangular duct. Good agreement between the simulation results from the proposed model and relevant experimental data indicates that the proposed model may be used as a reliable computational tool for two-phase flow simulations in narrow rectangular flow geometry.

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