scholarly journals Lattice Boltzmann Simulation of Nucleate Pool Boiling in Saturated Liquid

2011 ◽  
Vol 9 (5) ◽  
pp. 1347-1361 ◽  
Author(s):  
Yoshito Tanaka ◽  
Masato Yoshino ◽  
Tetsuo Hirata
Keyword(s):  
Lattice Boltzmann ◽  
Solid Wall ◽  
Bubble Diameter ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Immiscible Fluids ◽  
Nucleate Pool Boiling ◽  
Two Phase ◽  
Boiling Process

AbstractA thermal lattice Boltzmann method (LBM) for two-phase fluid flows in nucleate pool boiling process is proposed. In the present method, a new function for heat transfer is introduced to the isothermal LBM for two-phase immiscible fluids with large density differences. The calculated temperature is substituted into the pressure tensor, which is used for the calculation of an order parameter representing two phases so that bubbles can be formed by nucleate boiling. By using this method, two-dimensional simulations of nucleate pool boiling by a heat source on a solid wall are carried out with the boundary condition for a constant heat flux. The flow characteristics and temperature distribution in the nucleate pool boiling process are obtained. It is seen that a bubble nucleation is formed at first and then the bubble grows and leaves the wall, finally going up with deformation by the buoyant effect. In addition, the effects of the gravity and the surface wettability on the bubble diameter at departure are numerically investigated. The calculated results are in qualitative agreement with other theoretical predictions with available experimental data.

scholarly journals Determination of Pool Boiling Critical Heat Flux Enhancement in Nanofluids

2007 ◽  
Author(s):  
Bao H. Truong
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Porous Coating ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Sem Images ◽  
Heat Transfer Coefficients ◽  
Nucleate Boiling Heat Transfer

Nanofluids are engineered colloids composed of nano-size particles dispersed in common fluids such as water or refrigerants. Using an electrically controlled wire heater, pool boiling Critical Heat Flux (CHF) of Alumina and Silica water-based nanofluids of concentration less than or equal to 0.1 percent by volume were measured. Silica nanofluids showed a CHF enhancement up to 68% and there seems to be a monotonic relationship between the nanoparticle concentration and the magnitude of enhancement. Alumina nanofluids had a CHF enhancement up to 56% but the peak occurred at the intermediate concentration. The boiling curves in nanofluid were found to shift to the left of that of water and correspond to higher nucleate boiling heat transfer coefficients in the two-phase flow regime. Scanning Electron Microscopy (SEM) images show a porous coating layer of nanoparticles on wires subjected to nanofluid CHF tests. These coating layers change the morphology of the heater’s surface, and are responsible for the CHF enhancement. The thickness of the coating was estimated using SEM and was found ranging from 3.0 to 6.0 micrometers for Alumina, and 3.0 to 15.0 micrometers for Silica.

Inverse Determination of the Local Heat Transfer Coefficients for Nucleate Boiling on a Horizontal Cylinder

2003 ◽  
Vol 125 (6) ◽  
pp. 1087-1095 ◽  
Author(s):  
H. Louahlia-Gualous ◽  
P. K. Panday ◽  
E. A. Artioukhine
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pool Boiling ◽  
Gradient Methods ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Nucleate Boiling ◽  
Nucleate Pool Boiling ◽  
Transfer Coefficients ◽  
Iterative Regularization

This article treats the local heat transfer for nucleate pool boiling around the cylinder using the inverse heat conduction analysis. The physical model considers a half section of a cylinder with unknown surface temperature and heat flux density. The iterative regularization and the conjugate gradient methods are used for solving the inverse analysis. The local Nusselt number profiles for nucleate pool boiling are presented and analyzed for different electric heat. The mean Nusselt number estimated by IHCP is closed with the measured values. The results of IHCP are compared to those of Cornewell and Houston (1994), Stephan and Abdelsalam (1980) and Memory et al. (1995). The influence of the error of the measured temperatures and the error in placement of the thermocouples are studied.

Flow Boiling on Heterogeneous Wetting Surface in a Vertical Narrow Microchannel

2020 ◽  
Author(s):  
Yuhao Lin ◽  
Junye Li ◽  
Kan Zhou ◽  
Wei Li ◽  
Kuang Sheng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Instability ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Flow Patterns ◽  
Bubble Nucleation ◽  
Working Fluid ◽  
Hydrophilic Surface ◽  
Structured Surfaces ◽  
Boiling Process

Abstract The micro structured surfaces have significant impact on the flow patterns and heat transfer mechanisms during the flow boiling process. The hydrophobic surface promotes bubble nucleation while the hydrophilic surface supplies liquid to a heating surface, thus there is a trade-off between a hydrophobic and a hydrophilic surface. To examine the effect of heterogeneous wetting surface on flow boiling process, an experimental investigation of flow boiling in a rectangular vertical narrow microchannel with the heterogeneous wetting surface was conducted with deionized water as the working fluid. The heat transfer characteristics of flow boiling in the microchannel was studied and the flow pattern was photographed with a high-speed camera. The onset of flow boiling and heat transfer coefficient were discussed with the variation of heatfluxes and mass fluxes, the trends of which were analyzed along with the flow patterns. During the boiling process, the dominated heat transfer mechanism was nucleate boiling, with numerous nucleate sites between the hydrophilic/hydrophobic stripes and on the hydrophobic ones. In the meantime, after the merged bubbles were constrained by the channel walls, it would be difficult for them to expand towards upstream since they were restricted by the contact line between hydrophilic/hydrophobic stripes, thereby reduce the flow instability and achieve remarkable heat transfer performance.

Parallelization of Lattice Boltzmann method using MPI domain decomposition technology for a drop impact on a wetted solid wall

2014 ◽  
Vol 05 (02) ◽  
pp. 1350024 ◽  
Author(s):  
Zhi Shang ◽  
Ming Cheng ◽  
Jing Lou
Keyword(s):  
Domain Decomposition ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
High Performance ◽  
Message Passing Interface ◽  
Solid Wall ◽  
Data Communication ◽  
Drop Impact ◽  
Two Phase ◽  
Boltzmann Method

Lattice Boltzmann method (LBM) is a new attractive computational approach for simulating isothermal multi-phase flows in computational fluid dynamics (CFD). It is based on the kinetic theory and easy to be parallelized. This study aims to analyze the performance of parallel LBM programming for the incompressible two-phase flows at high density and viscosity ratio. For this purpose, a liquid drop impact on a wetted wall with a pre-existing thin film of the same liquid is simulated by using the parallel LBM code. During the simulations, the domain decomposition, data communication and parallelization of the LBM code using the message passing interface (MPI) library have been investigated. The computational results show that the parallel LBM code exhibits a good high performance computing (HPC) on the parallel speed-up.

Lattice Boltzmann Simulation of Surface Tension Dominated Vortices Behaviour in Two-Phase Mixing Layer

2006 ◽  
Author(s):  
Y. Y. Yan ◽  
Y. Q. Zu
Keyword(s):  
Surface Tension ◽  
Multiphase Flow ◽  
Lattice Boltzmann ◽  
Mixing Layer ◽  
Vertical Direction ◽  
Immiscible Fluids ◽  
Interfacial Interactions ◽  
Two Phase ◽  
Phase Mixing ◽  
Two Fluids

Surface tension dominating mixings and interfacial interactions are major phenomena of multiphase flow in microchannels and a variety of micro mixers. Such phenomena are concerned with interfacial interactions not only at fluid-solid interface but also at different fluids/phases interfaces. In this paper, vortices behaviours in a mixing layer of two immiscible fluids are studied numerically. The lattice Boltzmann method (LBM) is employed to simulat surface tension dominated mixing process. As a mesoscopic numerical method, the LBM has many advantages, which include the ability of incorporating microscopic interactions, the simplicity of programming and the nature of parallel algorithm and is therefore ideal for simulating multiphase flow. In this article, the index function methodology of the LBM is employed to simulate surface tension dominated vertices behaviour in a two-dimensional immiscible two-phase mixing layer. The initial interface between two-fluids is evenly distributed around the midpoint in vertical direction. Different velocity perturbations which consist of a basic wave and a series of sub-harmonic waves are forced at the entrance of a rectangular mixing layer of the flow field. By changing the strength of surface tension and the combinations of perturbation waves, the effects of the surface tension and the velocity perturbation on vortices merging are investigated. The vortices contours and frequency spectrums are used to analyse the mechanism of vortices merging. Some interesting phenomena, which do not take place in a single-phase mixing layer, are observed and the corresponding mechanism is discussed in details.

Core–annular flow in a periodically constricted circular tube. Part 1. Steady-state, linear stability and energy analysis

2001 ◽  
Vol 432 ◽  
pp. 31-68 ◽  
Author(s):  
CHARALAMPOS KOURIS ◽  
JOHN TSAMOPOULOS
Keyword(s):  
Weber Number ◽  
Annular Flow ◽  
Viscosity Ratio ◽  
Solid Wall ◽  
Immiscible Fluids ◽  
Straight Tube ◽  
Neutral Stability ◽  
Ohnesorge Number ◽  
Dimensionless Numbers ◽  
Two Phase

The concentric, two-phase flow of two immiscible fluids in a tube of sinusoidally varying cross-section is studied. This geometry is often used as a model to study the onset of different flow regimes in packed beds. Neglecting gravitational effects, the model equations depend on five dimensionless parameters: the Reynolds and Weber numbers, and the ratios of density, viscosity and volume of the two fluids. Two more dimensionless numbers describe the shape of the solid wall: the constriction ratio and the ratio of its maximum radius to its period. In addition to the effect of the Weber number, which depends on both the fluid and the flow, the effect of the Ohnesorge number J has been examined as it characterizes the fluid alone. The governing equations are approximated using the pseudo-spectral methodology while the Arnoldi algorithm has been implemented for computing the most critical eigenvalues that correspond to axisymmetric disturbances. Stationary solutions are obtained for a wide parameter range, which may exhibit flow recirculation at the expanding portion of the tube. Extensive calculations are made for the dependence of the neutral stability boundaries on the various parameters. In most cases where the steady solution becomes unstable it does so through a Hopf bifurcation. Exceptions to this are cases where the viscosity ratio is O(10−3) and, then, the most unstable eigenvalue remains real. Generally, steady core–annular flow in this geometry is more susceptible to instability than in a straight tube and, in similar ranges of the parameters, it may be generated by different mechanisms. Decreasing the thickness of the annular fluid, inverse Weber number or the Ohnesorge number or the density of the core fluid stabilizes the flow. For stability reasons, the viscosity ratio must remain strictly below unity and it has an optimum value that maximizes the range of allowed Reynolds numbers.

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.

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