Numerical
Simulation for Interfacial Forces of Counter-Current Flow over an Inclined
Plate

Rajesh
K. Singh^1,2 and  Janine E. Galvin¹,
Xin Sun³ and Sankaran Sundaresan⁴

¹Computational Science and
Engineering Division, National Energy Technology Laboratory,

Albany, Oregon 97321, United States

²ORISE Postdoc
Fellow, National Energy Technology Laboratory,

Albany, Oregon 97321, United States

³Fundamental
Computational Sciences Directorate, Pacific Northwest National Laboratory,

Richland,
Washington 99352, United State

⁴
Department
of Chemical and Biological Engineering, Princeton University,

Princeton,
New Jersey 08544, United States

CFD
modeling of solvent-based carbon capture is a complex multi-scale
problem.  The detailed behavior of the liquid film on the structured
packing element and the flow distribution through the packing are key aspects
influencing the overall efficiency of the column.  These scales cannot be
resolved simultaneously within a single computational model.  The
two-fluid model (TFM) approach is a suitable technique for modeling large scale
systems; however, it requires closure models for unresolved scales. 
Namely, the small scale structures of the interface will influence the mass,
momentum and heat transfer between the phases.  The goal of this effort is
to examine the use of volume of fluid (VOF) simulations to develop an
interfacial force model for momentum transfer.

Here
turbulent multiphase flow simulations for countercurrent gas-liquid flow over
an inclined plate are carried out using volume of fluid method (VOF). The
effects of solvent properties on the hydrodynamics of gas-liquid flows are
systematically investigated. Interfacial area and film thickness have been
found to scale well with the Kapitza number.
 The advantage of the Kapitza number is that it
only depends on fluid properties and therefore it is fixed for a given solvent.
The computation of the interfacial force at the solid-liquid and solid-gas
interfaces is straightforward. In contrast, computation of the force at the gas-liquid
interface is challenging due to it being a moving and flexible boundary. In
this problem the total interfacial force is computed as the sum of the force
due to shear and the interfacial surface tension force for varying gas/liquid
flow rates and solvent properties. A theory for an interfacial force is
proposed based on the CFD simulated results. The simulation results show that
the liquid-solid drag (wall shear) is always higher than the gas-liquid
interfacial force.

Multiphase
flow simulations are also conducted for countercurrent gas-liquid flow through
a packed column using the TFM approach. 
In these simulations the packing is treated as a porous region with a
general model for the gas-liquid interaction force.  Plans are to adopt a more appropriate
mechanism based on the detailed results from the VOF study.