Hydrodynamic instabilities of near-critical CO2 flow in microchannels: Lattice Boltzmann simulation

Abstract

Motivated by systematic CO2 evaporation experiments which recently became available (J. Pettersen, “Flow vaporization of CO2 in microchannel tubes,” Doctor technicae thesis, Norwegian University of Science and Technology, 2002), the present work constitutes an exploratory investigation of isothermal flow of CO2 near its liquid–vapor critical point through a long 5 μm diameter microchannel. A modified van der Waals constitutive model—with properties closely approximating those of “real” near-critical CO2—is incorporated in a two-dimensional lattice Boltzmann hydrodynamics model by embedding a dimensionless parameter X, with X→1 denoting the “real” fluid. The hydrodynamic phenomena resulting by imposing a constant pressure gradient along a periodic channel are investigated by considering two regimes in tandem: (1) transition from bubbly to annular flow with a liquid film formed at the channel walls and (2) destabilization of the liquid film by the Kelvin–Helmholtz instability. Due to numerical constraints, intrinsic modeling errors are introduced and are shown to be associated with discrepancies in the relative vapor–liquid interfacial thickness, which is expressed by X. The effects of these errors are investigated both theoretically and numerically in the physical limit X→1. Numerically determined flow patterns compare qualitatively well with direct visualization results obtained by Pettersen. Overall, the characteristics of isothermal near-critical two-phase flow in microchannels can be reproduced by the appropriate modification of the thermophysical properties of CO2.

Experimental and numerical study of droplets hydrodynamics in microchannels

“…Several studies focused on simulating two‐phase flows inside milli‐ and microchannels. Holdych et al4 studied the stability of a gas–liquid annular stream using a Lattice–Boltzmann method in a two‐dimensional (2D) microchannel. Ghidersa et al5 carried out three‐dimensional (3D) computations of the hydrodynamics of a bubble chain in a millimetric channel using a Volume of Fluid Method.…”

Numerical investigations of gas–liquid two-phase flows in microchannels

“…19 and Holdych et al. 41

Figure 11.Snapshots of the bubble evolution for the case of Re = 7.45 and Ca = 1.3. (a) t = 0; (b) t = 3000; (c) t = 10,000; and (d) t = 50,000.

Figure 12.Steady-state phase distribution under Re = 13.35 and Ca = 2.35.

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Equation of State’s Crossover Enhancement of Pseudopotential Lattice Boltzmann Modeling of CO2 Flow in Homogeneous Porous Media

“…Therefore, various mitigation measures have been proposed to tackle global climate change. Among those proposed solutions, we use CO 2 in different applications such as Hot-Dry Rock (HDR) systems, heat engines, selective extraction processes, reclamation processes of metals from industrial effluents, and chemical reactions [2,3]. Nevertheless, CO 2 sequestration is recognized as one of the key strategies for reducing CO 2 emission rates.…”