Lattice Boltzmann Simulations of Bubble Dynamics at the Anode of a µDMFC

2005 ◽  
Author(s):  
Kai Fei ◽  
Chin-Hsien Cheng ◽  
Che-Wun Hong
Keyword(s):  
Pore Size ◽  
Flow Rate ◽  
Diffusion Layer ◽  
Lattice Boltzmann ◽  
Stream Flow ◽  
Bubble Dynamics ◽  
Model Simulation ◽  
Solid Wall ◽  
Two Phase ◽  
Flow Channels

This paper presents the bubble transport phenomenon at the anode of a micro direct methanol fuel cell (μDMFC) from a messooscopic viewpoint. Carbon dioxide bubbles generated at the anode may block part of the catalyst/diffusion layer and also the flow channels that cause the μDMFC malfunction. Lattice-Boltzmann methods (LBM) were employed in this paper to simulate the two phase flow in a simplified micro channel which emulates the bubble dynamics in the porous diffusion layer and the flow channel. A two-dimensional, nine velocity model (D2Q9) was established. The surface tension, buoyancy force were treated as source terms in the momentum equation. Bounce back boundary conditions were assumed at the fluid-solid interface in this model. Simulation results and parametric studies showed that the pore size, the stream flow rate and the hydrophilic effect between the fluid and the solid wall play the major roles in the bubble dynamics. Larger pore size, higher methanol stream flow rate and greater hydrophilicity are preferred for bubble removal at the anode diffusion layer and also the flow channels.

Lattice Boltzmann Simulations of CO2 Bubble Dynamics at the Anode of a μDMFC

2005 ◽  
Vol 3 (2) ◽  
pp. 180-187 ◽  
Author(s):  
K. Fei ◽  
C. H. Cheng ◽  
C. W. Hong
Keyword(s):  
Surface Tension ◽  
Pore Size ◽  
Flow Rate ◽  
Diffusion Layer ◽  
Lattice Boltzmann ◽  
Stream Flow ◽  
Bubble Dynamics ◽  
Solid Wall ◽  
Flow Channels ◽  
Lattice Boltzmann Simulations

This paper presents the bubble transport phenomenon at the anode of a micro-direct methanol fuel cell (μDMFC) from a mesoscopic viewpoint. Carbon dioxide bubbles generated at the anode may block part of the catalyst/diffusion layer and also the flow channels that cause the μDMFC malfunction. Lattice-Boltzmann simulations were performed in this paper to simulate the two-phase flow in a microchannel with an orifice which emulates the bubble dynamics in a simplified porous diffusion layer and in the flow channel. A two-dimensional, nine-velocity model was established. The buoyancy force, the liquid-gas surface tension, and the fluid-solid wall interaction force were considered and they were treated as source terms in the momentum equation. Simulation results and parametric studies show that the pore size, the fluid stream flow rate, the bubble surface tension, and the hydrophilic effect between the fluid and the solid wall play the major roles in the bubble dynamics. Larger pore size, higher methanol stream flow rate, and greater hydrophilicity are preferred for bubble removal at the anode diffusion layer and also the flow channels of the μDMFC.

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.

Micro-scale simulation of bubble-water flow in coal seams by the lattice Boltzmann method

2016 ◽  
Vol 56 (2) ◽  
pp. 608
Author(s):  
Jie Yi ◽  
Huilin Xing ◽  
Tianwei Sun ◽  
Victor Rudolph
Keyword(s):  
Coal Seam ◽  
Water Flow ◽  
Flow Rate ◽  
Bubble Size ◽  
Lattice Boltzmann ◽  
Water Flow Rate ◽  
Bubble Flow ◽  
Coal Seam Gas ◽  
Two Phase ◽  
Flow Process

The production of coal seam gas initially requires pumping and removing significant amounts of water to sufficiently reduce the hydrostatic pressure in the subsurface, so that methane can desorb from the matrix and diffuse into the cleat systems; majority of the methane molecules gather into nucleation or bubbles. During the depression, the flow pattern of gas in cleats changes from bubble flow to slug flow, and finally forms circular flow. The significance of the bubble flow process—during which the liquid phase is continuous while the gas phase exists as small bubbles randomly distributed within the liquid—has not been emphasised because of its complexity. In this study, a free energy based two-phase lattice Boltzmann model is used to simulate the gas bubble/water flow behaviour in micro-cleats of a coal seam gas reservoir. The model was validated by comparison with analytical results based on dimensionless numbers, and good agreement was found in general. The influences of bubble shape, bubble size, and coal surface wettability on gas water two-phase flow in micro-cleats are discussed. The simulation results indicate that the bubble size and wettability of gas have significant impacts on the flow capacity of both gas and water. A decrease of the water flow rate is observed when large bubbles occur, and the gas flow rate decreases when the gas wettability becomes stronger. The bubble flow process significantly influences the drainage of water and the further gas production.

AMADEUS Project and Microscopic Simulation of Boiling Two-Phase Flow by the Lattice-Boltzmann Method

1997 ◽  
Vol 08 (04) ◽  
pp. 843-858 ◽  
Author(s):  
Yasuyoshi Kato ◽  
Koji Kono ◽  
Takeshi Seta ◽  
Daniel Martínez ◽  
Shiyi Chen
Keyword(s):  
Phase Transition ◽  
Gas Phase ◽  
Lattice Boltzmann ◽  
Bubble Dynamics ◽  
Two Phase Flow ◽  
Phase Interface ◽  
Lattice Boltzmann Model ◽  
Phase Flow ◽  
Two Phase ◽  
Boltzmann Model

A two-dimensional lattice-Boltzmann model with a hexagonal lattice is developed to simulate a boiling two-phase flow microscopically. Liquid-gas phase transition and bubble dynamics, including bubble formation, growth and deformation, are modeled by using an interparticle potential based on the van der Waals equation of state. Thermohydrodynamics is incorporated into the model by adding extra velocities to define temperature. The lattice-Boltzmann model is solved by a finite difference scheme so that numerical stability can be ensured at large discontinuity across the liquid-gas phase boundary and the narrow phase interface thickness can be attained. It is shown from numerical simulations that the model has the ability to reproduce phase transition, bubble dynamics and thermohydrodynamics while assuring numerical instability and narrow phase interface.

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.

scholarly journals Liquid Water Transport in Porous Metal Foam Flow-Field Fuel Cells: A Two-Phase Numerical Modelling and Ex-Situ Experimental Study

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1186 ◽  
Author(s):  
Ashley Fly ◽  
Kyoungyoun Kim ◽  
John Gordon ◽  
Daniel Butcher ◽  
Rui Chen
Keyword(s):  
Flow Field ◽  
Pore Size ◽  
Flow Rate ◽  
Liquid Water ◽  
Metal Foam ◽  
Porous Metal ◽  
Ex Situ ◽  
Air Flow Rate ◽  
Two Phase ◽  
Foam Flow

Proton exchange membrane fuel cells (PEMFCs) using porous metallic foam flow-field plates have been demonstrated as an alternative to conventional rib and channel designs, showing high performance at high currents. However, the transport of liquid product water through metal foam flow-field plates in PEMFC conditions is not well understood, especially at the individual pore level. In this work, ex-situ experiments are conducted to visualise liquid water movement within a metal foam flow-field plate, considering hydrophobicity, foam pore size and air flow rate. A two-phase numerical model is then developed to further investigate the fundamental water transport behaviour in porous metal foam flow-field plates. Both the experimental and numerical work demonstrate that unlike conventional PEMFC channels, air flow rate does not have a strong influence on water removal due to the high surface tensions between the water and foam pore ligaments. A hydrophobic foam was seen to transport liquid water away from the initial injection point faster than a hydrophilic foam. In ex-situ tests, liquid water forms and maintains a random preferential pathway until the flow-field edge is reached. These results suggest that controlled foam hydrophobicity and pore size is the best way of managing water distribution in PEMFCs with porous flow-field plates.

scholarly journals Role of Pore-Size Distribution on Effective Rheology of Two-Phase Flow in Porous Media

2021 ◽  
Vol 3 ◽  
Author(s):  
Subhadeep Roy ◽  
Santanu Sinha ◽  
Alex Hansen
Keyword(s):  
Porous Media ◽  
Pressure Drop ◽  
Pore Size ◽  
Power Law ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Viscous Forces ◽  
Capillary Bundle

Immiscible two-phase flow of Newtonian fluids in porous media exhibits a power law relationship between flow rate and pressure drop when the pressure drop is such that the viscous forces compete with the capillary forces. When the pressure drop is large enough for the viscous forces to dominate, there is a crossover to a linear relation between flow rate and pressure drop. Different values for the exponent relating the flow rate and pressure drop in the regime where the two forces compete have been reported in different experimental and numerical studies. We investigate the power law and its exponent in immiscible steady-state two-phase flow for different pore size distributions. We measure the values of the exponent and the crossover pressure drop for different fluid saturations while changing the shape and the span of the distribution. We consider two approaches, analytical calculations using a capillary bundle model and numerical simulations using dynamic pore-network modeling. In case of the capillary bundle when the pores do not interact to each other, we find that the exponent is always equal to 3/2 irrespective of the distribution type. For the dynamical pore network model on the other hand, the exponent varies continuously within a range when changing the shape of the distribution whereas the width of the distribution controls the crossover point.

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