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Microfluidic analysis of CO2 bubble dynamics using thermal lattice-Boltzmann method

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Abstract

By means of microfluidic analysis with a thermal lattice-Boltzmann method, we investigated the hydrophilic, thermal and geometric effects on the dynamics of CO2 bubbles at anode microchannels (e.g., porous layers and flow channels) of a micro-direct methanol fuel cell. The simulation results show that a more hydrophilic wall provides an additional attractive force to the aqueous methanol in the flow direction and that moves the CO2 bubble more easily. The bubble propagates quicker in the microchannel with a positive temperature gradient imposed from the inlet to the exit, mainly due to the Marangoni effect. Regarding the geometric effect of the microchannel, the bubble moves more rapidly in a divergent microchannel than in a straight or convergent channel. On the basis of the quantitative evaluation of hydrophilic, thermal and geometric effects, we are able to design the bubble-removal technique in micro fuel cells.

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Abbreviations

e :

lattice velocity vector

e :

lattice speed (cm/s)

f :

density distribution function (g/cm3)

g :

thermal distribution function (g K/cm3)

\(G^{{\sigma \sigma^{\prime}}}\) :

interaction strength between the species σ and the other species σ′ (cm3/g s)

G σ :

fluid–solid interaction potential parameter of the species σ

G :

gravitational constant (cm/s2)

G′:

non-dimensional constant

T :

temperature (K)

t :

time (s)

U :

velocity vector(u,v)

u :

velocity in the x-direction (cm/s)

v :

velocity in the y-direction (cm/s)

X :

position vector (x,y)

β:

thermal expansion coefficient (1/K)

ρ:

density (g/cm3)

θ:

contact angle (°)

τ:

collision time for momentum transfer

τ T :

collision time for energy transfer

ψ:

function of the mass density

i :

lattice velocity directions

∞:

reference state

eq:

equilibrium

σ:

species

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Acknowledgments

National Science Council (contract NSC 95-2218-E-007-001) provided financial support; National Center for High-performance Computing provided high-speed computer facilities.

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Authors and Affiliations

  1. Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu, 30013, Taiwan

    K. Fei, W. H. Chen & C. W. Hong

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  1. K. Fei
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  2. W. H. Chen
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  3. C. W. Hong
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Corresponding author

Correspondence to C. W. Hong.

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Fei, K., Chen, W.H. & Hong, C.W. Microfluidic analysis of CO2 bubble dynamics using thermal lattice-Boltzmann method. Microfluid Nanofluid 5, 119–129 (2008). https://doi.org/10.1007/s10404-007-0232-x

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  • DOI: https://doi.org/10.1007/s10404-007-0232-x

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