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.

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.

Boundary element method in numerical study of three-dimensional Stokes flows in channels of arbitrary shape

2012 ◽  
Vol 9 (1) ◽  
pp. 94-97
Author(s):  
Yu.A. Itkulova
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Cross Section ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cylindrical Tube ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Periodic Flows ◽  
Element Method

In the present work creeping three-dimensional flows of a viscous liquid in a cylindrical tube and a channel of variable cross-section are studied. A qualitative triangulation of the surface of a cylindrical tube, a smoothed and experimental channel of a variable cross section is constructed. The problem is solved numerically using boundary element method in several modifications for a periodic and non-periodic flows. The obtained numerical results are compared with the analytical solution for the Poiseuille flow.

Experimental and simulation study of impurity transport response to RMPs in RF-heated H-mode plasmas at EAST

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Germán Vogel ◽  
Hongming Zhang ◽  
Yongcai Shen ◽  
Shuyu Dai ◽  
Youwen Sun ◽  
...  
Keyword(s):  
Inner Core ◽  
Extreme Ultraviolet ◽  
Transport Coefficients ◽  
Three Dimensional ◽  
Line Emission ◽  
Core Region ◽  
Emission Mitigation ◽  
One Dimensional ◽  
Impurity Transport ◽  
Transport Code

Spatial profiles of impurity emission measurements in the extreme ultraviolet (EUV) spectroscopic range in radiofrequency (RF)-heated discharges are combined with one-dimensional and three-dimensional transport simulations to study the effects of resonant magnetic perturbations (RMPs) on core impurity accumulation at EAST. The amount of impurity line emission mitigation by RMPs appears to be correlated with the ion Z for lithium, carbon, iron and tungsten monitored, i.e. stronger suppression of accumulation for heavier ions. The targeted effect on the most detrimental high-Z impurities suggests a possible advantage using RMPs for impurity control. Profiles of transport coefficients are calculated with the STRAHL one-dimensional impurity transport code, keeping $\nu /D$ fixed and using the measured spatial profiles of $\textrm{F}{\textrm{e}^{20 + }}$ , $\textrm{F}{\textrm{e}^{21 + }}$ and $\textrm{F}{\textrm{e}^{22 + }}$ to disentangle the transport coefficients. The iron diffusion coefficient ${D_{\textrm{Fe}}}$ increases from $1.0- 2.0\;{\textrm{m}^2}\;{\textrm{s}^{ - 1}}$ to $1.5- 3.0\;{\textrm{m}^2}\;{\textrm{s}^{ - 1}}$ from the core region to the edge region $(\rho \gt 0.5)$ after the onset of RMPs. Meanwhile, an inward pinch of iron convective velocity ${\nu _{\textrm{Fe}}}$ decreases in magnitude in the inner core region and increases significantly in the outer confined region, simultaneously contributing to preserving centrally peaked $\textrm{Fe}$ profiles and exhausting the impurities. The ${D_{\textrm{Fe}}}$ and ${\nu _{\textrm{Fe}}}$ variations lead to reduced impurity contents in the plasma. The three-dimensional edge impurity transport code EMC3-EIRENE was also applied for a case of RMP-mitigated high-Z accumulation at EAST and compared to that of low-Z carbon. The exhaust of ${\textrm{C}^{6 + }}$ toward the scrape-off layer accompanying an overall suppression of heavier ${\textrm{W}^{30 + }}$ is observed when using RMPs.

CFD Simulation of Particle Transport and Dispersion in Indoor Environment by Human Walking

2012 ◽  
Author(s):  
Iman Goldasteh ◽  
Goodarz Ahmadi ◽  
Andrea Ferro
Keyword(s):  
Particulate Matter ◽  
High Speed ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Study Data ◽  
Turbulent Dispersion ◽  
Experimental Chamber ◽  
Indoor Environments ◽  
Three Dimensional Model ◽  
Particle Resuspension

Particle resuspension is an important source of particulate matter in indoor environments that significantly affects the indoor air quality and could potentially have adverse effect on human health. Earlier efforts to investigate indoor particle resuspension hypothesized that high speed airflow generated at the floor level during the gate cycle is the main cause of particle resuspension. The resuspended particles are then assumed to be dispersed by the airflow in the room, which is impacted by both the ventilation and the occupant movement, leading to increased PM concentration. In this study, a three dimensional model of a room was developed using FLUENT™ CFD package. A RANS approach with the RNG k-ε turbulence model was used for simulating the airflow field in the room for different ventilation conditions. The trajectories of resuspended particulate matter were computed with a Lagrangian method by solving the equations of particle motion. The effect of turbulent dispersion was included with the use of the eddy lifetime model. The resuspension of particles due to gait cycle was estimated and included in the computational model. The dispersion and transport of particles resuspended from flooring as well as particle re-deposition on flooring and walls were simulated. Particle concentrations in the room generated by the resuspension process were evaluated and the results were compared with experimental chamber study data as well as simplified model predictions, and good agreement was found.

Prediction of Parameters Distribution of Upward Boiling Two-Phase Flow With Two-Fluid Models

2002 ◽  
Author(s):  
Wei Yao ◽  
Christophe Morel
Keyword(s):  
Void Fraction ◽  
Fluid Model ◽  
Constitutive Relations ◽  
Turbulent Dispersion ◽  
Dispersion Force ◽  
Liquid Temperature ◽  
Two Phase ◽  
Radial Profiles ◽  
Two Fluid Model ◽  
Two Fluid

In this paper, a multidimensional two-fluid model with additional turbulence k–ε equations is used to predict the two-phase parameters distribution in freon R12 boiling flow. The 3D module of the CATHARE code is used for numerical calculation. The DEBORA experiment has been chosen to evaluate our models. The radial profiles of the outlet parameters were measured by means of an optical probe. The comparison of the radial profiles of void fraction, liquid temperature, gas velocity and volumetric interfacial area at the end of the heated section shows that the multidimensional two-fluid model with proper constitutive relations can yield reasonably predicted results in boiling conditions. Sensitivity tests show that the turbulent dispersion force, which involves the void fraction gradient, plays an important role in determining the void fraction distribution; and the turbulence eddy viscosity is a significant factor to influence the liquid temperature distribution.

A Model of Bubble Nucleation on a Micro Line Heater

1999 ◽  
Vol 121 (1) ◽  
pp. 220-225 ◽  
Author(s):  
S.-D. Oh ◽  
S. S. Seung ◽  
H. Y. Kwak
Keyword(s):  
Bubble Formation ◽  
Three Dimensional ◽  
Bubble Nucleation ◽  
Heat Diffusion ◽  
Nucleation Theory ◽  
Molecular Cluster ◽  
Heater Surface ◽  
Calculation Results ◽  
Critical Bubble ◽  
Superheat Limit

The bubble nucleation mechanism on a cavity-free micro line heater surface was studied by using the molecular cluster model. A finite difference numerical scheme for the three-dimensional transient conduction equation for the liquid was employed to estimate the superheated volume where homogeneous bubble nucleation could occur due to heat diffusion from the heater to the liquid. Calculation results revealed that bubble formation on the heater is possible when the temperature at the hottest point in the heater is greater than the superheat limit of the liquid by 6°C–12°C, which is in agreement with the experimental results. Also it was found that the classical bubble nucleation theory breaks down near the critical point where the radius of the critical bubble is below 100 nm.

scholarly journals Crystallization and preliminary X-ray analysis of the major peanut allergen Ara h 1 core region

2010 ◽  
Vol 66 (9) ◽  
pp. 1071-1073 ◽  
Author(s):  
Cerrone Cabanos ◽  
Hiroyuki Urabe ◽  
Taro Masuda ◽  
Mary Rose Tandang-Silvas ◽  
Shigeru Utsumi ◽  
...  
Keyword(s):  
Sodium Citrate ◽  
Three Dimensional ◽  
Core Region ◽  
Dimensional Structure ◽  
Monoclinic Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Peg 400 ◽  
Ara H 1 ◽  
Peanut Allergens

Peanuts contain some of the most potent food allergens known to date. Ara h 1 is one of the three major peanut allergens. As a first step towards three-dimensional structure elucidation, recombinant Ara h 1 core region was cloned, expressed inEscherichia coliand purified to homogeneity. Crystals were obtained using 0.1 Msodium citrate pH 5.6, 0.1 MNaCl, 15% PEG 400 as precipitant. The crystals diffracted to 2.25 Å resolution using synchrotron radiation and belonged to the monoclinic space groupC2, with unit-cell parametersa= 156.521,b= 88.991,c= 158.971 Å, β = 107.144°. Data were collected at the BL-38B1 station of SPring-8 (Hyogo, Japan).

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