Lateral Mixing Mechanisms in Vertical and Horizontal Interconnected Subchannel Two-Phase Flows

Gencay, Sarman; Teyssedou, Alberto; Tye, Peter

Title: Lateral Mixing Mechanisms in Vertical and Horizontal Interconnected Subchannel Two-Phase Flows

Full Record
Other Related Research

Abstract

A lateral mixing model based on equal volume exchange between two laterally interconnected subchannels is presented. The following mixing mechanisms are taken into account in this model: (a) diversion cross flow, caused by the lateral pressure difference between adjacent subchannels; (b) turbulent void diffusion, which is governed by the lateral void fraction difference between the subchannels; (c) void drift, responsible for the tendency of the vapor phase to drift toward unobstructed regions; and (d) buoyancy drift, which takes into account the effect of gravity in horizontal flows. Experimental two-phase air-water data obtained using two test sections having different geometries and orientations are used to determine the diffusion coefficients required by the mixing model. Under the absence of diversion crossflow, i.e., negligible lateral pressure difference between the subchannels, it is observed that the diffusion coefficient increases with increasing average void fraction in the subchannels. Moreover, for vertical flows turbulent void diffusion seems to be considerably affected by the geometry of the subchannels. For horizontal flows under nonsymmetric inlet void fraction conditions, even though the interconnected subchannels have the same geometry, different turbulent void diffusion and void drift coefficients are required to satisfy the conditions of hydrodynamic equilibrium. In the present studymore »« less

Authors:: Gencay, Sarman; Teyssedou, Alberto; Tye, Peter

Publication Date:: Wed May 15 00:00:00 EDT 2002

OSTI Identifier:: 20826754

Resource Type:: Journal Article

Journal Name:: Nuclear Technology

Additional Journal Information:: Journal Volume: 138; Journal Issue: 2; Other Information: Copyright (c) 2006 American Nuclear Society (ANS), United States, All rights reserved. http://epubs.ans.org/; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0029-5450

Country of Publication:: United States

Language:: English

Subject:: 42 ENGINEERING; DIFFUSION; EQUILIBRIUM; GEOMETRY; MIXING; TWO-PHASE FLOW; VAPORS; VOID FRACTION; VOIDS; WATER

Citation Formats


                    Gencay, Sarman, Teyssedou, Alberto, and Tye, Peter. Lateral Mixing Mechanisms in Vertical and Horizontal Interconnected Subchannel Two-Phase Flows.  United States: N. p., 2002. 
        Web.

Copy to clipboard


                    Gencay, Sarman, Teyssedou, Alberto, & Tye, Peter. Lateral Mixing Mechanisms in Vertical and Horizontal Interconnected Subchannel Two-Phase Flows.  United States.

Copy to clipboard


                    Gencay, Sarman, Teyssedou, Alberto, and Tye, Peter. 2002.  
        "Lateral Mixing Mechanisms in Vertical and Horizontal Interconnected Subchannel Two-Phase Flows".  United States.

Copy to clipboard


                    
@article{osti_20826754,

  title        = {Lateral Mixing Mechanisms in Vertical and Horizontal Interconnected Subchannel Two-Phase Flows},

  author       = {Gencay, Sarman and Teyssedou, Alberto and Tye, Peter},

  abstractNote = {A lateral mixing model based on equal volume exchange between two laterally interconnected subchannels is presented. The following mixing mechanisms are taken into account in this model: (a) diversion cross flow, caused by the lateral pressure difference between adjacent subchannels; (b) turbulent void diffusion, which is governed by the lateral void fraction difference between the subchannels; (c) void drift, responsible for the tendency of the vapor phase to drift toward unobstructed regions; and (d) buoyancy drift, which takes into account the effect of gravity in horizontal flows. Experimental two-phase air-water data obtained using two test sections having different geometries and orientations are used to determine the diffusion coefficients required by the mixing model. Under the absence of diversion crossflow, i.e., negligible lateral pressure difference between the subchannels, it is observed that the diffusion coefficient increases with increasing average void fraction in the subchannels. Moreover, for vertical flows turbulent void diffusion seems to be considerably affected by the geometry of the subchannels. For horizontal flows under nonsymmetric inlet void fraction conditions, even though the interconnected subchannels have the same geometry, different turbulent void diffusion and void drift coefficients are required to satisfy the conditions of hydrodynamic equilibrium. In the present study this condition is achieved by introducing a new void drift coefficient expressed as a correction term applied to the turbulent void drift term.},

  doi          = {},

  url          = {https://www.osti.gov/biblio/20826754},
  journal      = {Nuclear Technology},

  issn         = {0029-5450},

  number       = 2,

  volume       = 138,

  place        = {United States},

  year         = {Wed May 15 00:00:00 EDT 2002},

  month        = {Wed May 15 00:00:00 EDT 2002}

}

Copy to clipboard

Journal Article:

Other availability

Find in Google Scholar

Search WorldCat to find libraries that may hold this journal

Save / Share:

Export Metadata

Save to My Library

Similar records in OSTI.GOV collections:

Sensitivity Studies of the Inter-subchannel Mixing in Subchannel Analysis

Journal Article Mao, Hu; Yang, Bao-Wen - Transactions of the American Nuclear Society

In the PWR reactor core, the power profile is nonuniform and the inter-subchannel mixing is of great importance for flatting the temperature distribution of the coolant and for reactor core safety analysis. Subchannel codes are widely used in the reactor core safety analysis to assess the thermal hydraulic behavior of fuel assemblies. One of basic assumptions in subchannel analysis is that axial flow predominates in the channel flow. Under this assumption, the lateral momentum equation in subchannel codes can be simplified without bringing in significant errors. The inter-subchannel mixing leading to the exchange of mass, energy and momentum are modeledmore »« less
Two-phase redistribution in horizontal subchannel flow-turbulent mixing and gravity separation

Journal Article Shoukri, M; Chan, A; Tawfik, H - Int. J. Multiphase Flow; (United States)

The redistribution of two-phase flow in two horizontal interconnected subchannels caused by gravity separation and turbulent mixing has been investigated experimentally using an air-water loop. The measured redistribution data included the axial distribution of void fraction and liquid and gas flow rates in the two subchannels. The redistribution data exhibited an asymptotic behaviour, approaching certain flow distributions independent of the inlet distribution. The observed equilibrium distributions were explained as a balance between gravity forces (which tend to cause flow stratification) and turbulent diffusion (which tends to homogenize the two-phase mixture). A constitutive equation for transverse vapour drift, to account formore »« less
https://doi.org/10.1016/0301-9322(84)90026-0
Numerical simulation of two-phase flow in horizontal interconnected subchannels

Journal Article Shourki, M; Carver, M; Tahir, A - Nucl. Technol.; (United States)

Different subchannel computer codes have been successfully used for the thermal-hydraulic analysis of coolant flow in vertical fuel channels. None of these methods, however, is suitable for two-phase flow in horizontal fuel channels, such as those of the CANDU nuclear reactors, due to the lack of appropriate constitutive relationships that can correctly account for the gravity separation effects. A transverse vapor drift model that accounts for the combined effect of gravity separation and turbulent diffusion has been incorporated into the existing subchannel computer code SAGA. Although the basic structure of the code remains similar to SAGA III, some modifications inmore »« less
CFD-Informed Spacer Grid Models in the Subchannel Code CTF

Journal Article Blyth, Taylor; Salko, Robert; Avramova, Maria - Transactions of the American Nuclear Society

Data from computational fluid dynamics (CFD) simulations can be utilized to improve the predictive capabilities of the subchannel code CTF. Past work incorporating CFD results into CTF has included accounting for directed crossflow and turbulent mixing between adjacent subchannels. Spacer grids impact fluid flow in various ways, and this work focuses on four spacer grid effects, namely: 1. Directed crossflow; 2. Turbulent mixing; 3. Enhanced downstream heat transfer; 4. Pressure drop correlation. Heat transfer augmentation occurs partially due to the disturbances in the developed flow and from the additional turbulence generated by the presence of obstructions in the fluid flow'smore »« less
Single- and Two-Phase Diversion Cross-Flows Between Triangle Tight Lattice Rod Bundle Subchannels - Data on Flow Resistance and Interfacial Friction Coefficients for the Cross-Flow

Conference Higuchi, Tatsuya; Kawahara, Akimaro; Sadatomi, Michio; ...

Single- and two-phase diversion cross-flows arising from the pressure difference between tight lattice subchannels are our concern in this study. In order to obtain a correlation of the diversion cross-flow, we conducted adiabatic experiments using a vertical multiple-channel with two subchannels simplifying the triangle tight lattice rod bundle for air-water flows at room temperature and atmospheric pressure. In the experiments, data were obtained on the axial variations in the pressure difference between the subchannels, the ratio of flow rate in one subchannel to the whole channel, the void fraction in each subchannel for slug-churn and annular flows in two-phase flowmore »« less

Similar Records