Showing papers on "Schmidt number published in 2006"

A critical review of dispersion in packed beds

Abstract: The phenomenon of dispersion (transverse and longitudinal) in packed beds is summarized and reviewed for a great deal of information from the literature. Dispersion plays an important part, for example, in contaminant transport in ground water flows, in miscible displacement of oil and gas and in reactant and product transport in packed bed reactors. There are several variables that must be considered, in the analysis of dispersion in packed beds, like the length of the packed column, viscosity and density of the fluid, ratio of column diameter to particle diameter, ratio of column length to particle diameter, particle size distribution, particle shape, effect of fluid velocity and effect of temperature (or Schmidt number). Empirical correlations are presented for the prediction of the dispersion coefficients (D T and D L) over the entire range of practical values of Sc and Pem, and works on transverse and longitudinal dispersion of non-Newtonian fluids in packed beds are also considered.

Hydrodynamic interactions and Brownian forces in colloidal suspensions: coarse-graining over time and length scales.

Abstract: We describe in detail how to implement a coarse-grained hybrid molecular dynamics and stochastic rotation dynamics simulation technique that captures the combined effects of Brownian and hydrodynamic forces in colloidal suspensions. The importance of carefully tuning the simulation parameters to correctly resolve the multiple time and length scales of this problem is emphasized. We systematically analyze how our coarse-graining scheme resolves dimensionless hydrodynamic numbers such as the Reynolds number Re, which indicates the importance of inertial effects, the Schmidt number Sc, which indicates whether momentum transport is liquidlike or gaslike, the Mach number, which measures compressibility effects, the Knudsen number, which describes the importance of noncontinuum molecular effects, and the Peclet number, which describes the relative effects of convective and diffusive transport. With these dimensionless numbers in the correct regime the many Brownian and hydrodynamic time scales can be telescoped together to maximize computational efficiency while still correctly resolving the physically relevant processes. We also show how to control a number of numerical artifacts, such as finite-size effects and solvent-induced attractive depletion interactions. When all these considerations are properly taken into account, the measured colloidal velocity autocorrelation functions and related self-diffusion and friction coefficients compare quantitatively with theoretical calculations. By contrast, these calculations demonstrate that, notwithstanding its seductive simplicity, the basic Langevin equation does a remarkably poor job of capturing the decay rate of the velocity autocorrelation function in the colloidal regime, strongly underestimating it at short times and strongly overestimating it at long times. Finally, we discuss in detail how to map the parameters of our method onto physical systems and from this extract more general lessons—keeping in mind that there is no such thing as a free lunch—that may be relevant for other coarse-graining schemes such as lattice Boltzmann or dissipative particle dynamics.

Dynamic subgrid‐scale models for momentum and scalar fluxes in large‐eddy simulations of neutrally stratified atmospheric boundary layers over heterogeneous terrain

Abstract: The accuracy of large-eddy simulations (LESs) of the atmospheric boundary layer (ABL) over complex terrain relies on the ability of the subgrid-scale (SGS) models to capture the effect of subgrid turbulent fluxes on the resolved fields of velocity and scalars (e.g., heat, water vapor, and pollutants). A common approach consists of parameterizing the SGS stresses and fluxes using eddy viscosity and eddy diffusivity models, respectively. These models require the specification of two parameters: the Smagorinsky coefficient in the eddy viscosity model and, in addition, the SGS Schmidt/Prandtl number in the eddy diffusivity model. This is complicated by the dependence of the coefficients on local conditions such as distance to the ground, mean shear, and atmospheric stability. In this study, scale-dependent dynamic SGS models are used in conjunction with Lagrangian averaging to compute both the Smagorinsky coefficient and the SGS Schmidt (or Prandtl) number dynamically as the flow evolves in both space and time based on the local dynamics of the resolved scales. These tuning-free models are implemented in LES of both homogeneous and heterogeneous neutral atmospheric boundary layers with surface fluxes of a passive scalar. In the homogeneous simulations the models are shown to accurately predict the resolved flow statistics (mean profiles and spectra of velocity and scalar concentration) and spatial distributions of the SGS model coefficients and parameters. In simulations over heterogeneous surfaces both coefficients adjust in a self-consistent way to horizontal flow inhomogeneities associated with changes in surface conditions. For smooth-to-rough (rough-to-smooth) abrupt changes in surface roughness the Smagorinsky coefficient decreases (increases) in response to increased (decreased) mean shear and flow anisotropy associated with these transitions. The SGS Schmidt number also adjusts to inhomogeneities in the scalar field associated with changes in surface scalar flux. This illustrates the need for local calculation of model coefficients and brings into question the common practice of using a constant SGS Schmidt/Prandtl number in LES of the ABL.

Flux corrected finite volume scheme for preserving scalar boundedness in reacting large-eddy simulations

Abstract: Preserving scalar boundedness is an important prerequisite to performing large-eddy simulations of turbulent reacting flows. A number of popular combustion models use a conserved-scalar, mixture-fraction to parameterize reactions that, by definition, is bound between zero and one. To avoid unphysical clipping, the numerical scheme solving the conserved-scalar transport equation must preserve these bounds, while minimizing the amount of numerical diffusivity. To this end, a flux correction method is presented and applied to the quadratic-upwind biased interpolative convective scheme that ensures preservation of the scalar's physical bounds while retaining the low numerical diffusivity of the original quadratic-upwind biased interpolative convective scheme. It is demonstrated that this bounded quadratic-upwind biased interpolative convective scheme outperforms the third-order weighted essentially nonoscillatory scheme in maintaining spatial accuracy and reducing numerical dissipation errors both in generic test cases as well as direct numerical simulation of canonical flows.

Dispersion in steady and oscillatory flows through a tube with reversible and irreversible wall reactions

Abstract: An asymptotic analysis is presented for the advection–diffusion transport of a chemical species in flow through a small-diameter tube, where the flow consists of steady and oscillatory components, and the species may undergo linear reversible (phase exchange or wall retention) and irreversible (decay or absorption) reactions at the tube wall. Both developed and transient concentrations are considered in the analysis; the former is governed by the Taylor dispersion model, while the latter is required in order to formulate proper initial data for the developed mean concentration. The various components of the effective dispersion coefficient, valid when the developed state is attained, are derived as functions of the Schmidt number, flow oscillation frequency, phase partitioning and kinetics of the two reactions. Being more general than those available in the literature, this effective dispersion coefficient incorporates the combined effects of wall retention and absorption on the otherwise classical Taylor dispersion mechanism. It is found that if the phase exchange reaction kinetics is strong enough, the dispersion coefficient is probably to be increased by orders of magnitude by changing the tube wall from being non-retentive to being just weakly retentive.

The Hydrodynamic Interaction in Polymer Solutions Simulated with Dissipative Particle Dynamics

Abstract: We analyzed extensively the dynamics of polymer chains in solutions simulated with dissipative particle dynamics (DPD), with a special focus on the potential influence of a low Schmidt number of a typical DPD fluid on the simulated polymer dynamics. It has been argued that a low Schmidt number in a DPD fluid can lead to underdevelopment of the hydrodynamic interaction in polymer solutions. Our analyses reveal that equilibrium polymer dynamics in dilute solution, under a typical DPD simulation conditions, obey the Zimm model very well. With a further reduction in the Schmidt number, a deviation from the Zimm model to the Rouse model is observed. This implies that the hydrodynamic interaction between monomers is reasonably developed under typical conditions of a DPD simulation. Only when the Schmidt number is further reduced, the hydrodynamic interaction within the chains becomes underdeveloped. The screening of the hydrodynamic interaction and the excluded volume interaction as the polymer volume fraction is increased are well reproduced by the DPD simulations. The use of soft interaction between polymer beads and a low Schmidt number do not produce noticeable problems for the simulated dynamics at high concentrations, except that the entanglement effect which is not captured in the simulations.

Turbulent diffusion in protoplanetary discs: the effect of an imposed magnetic field

Abstract: We study the effect of an imposed vertical magnetic field on the turbulent mass diffusion properties of magnetorotational turbulence in protoplanetary discs. It is well-known that the effective viscosity generated by the turbulence depends strongly on the magnitude of such an external field. In this Letter we show that the turbulent diffusion of the flow also changes, but that the diffusion coefficient does not rise with increasing vertical field as fast as the viscosity does. The vertical Schmidt number, i.e. the ratio between viscosity and vertical diffusion, can be close to 20 for high field magnitudes, whereas the radial Schmidt number is increased from below unity to around 3.5. Our results may have consequences for the interpretation of observations of dust in protoplanetary discs and for chemical evolution modelling of these discs.

Unsteady flows with mass transfer in narrow zigzag spacer-filled channels : A numerical study

Abstract: A computational fluid dynamics (CFD) model was used to simulate unsteady fluid flow with mass transfer in two-dimensional narrow channels containing zigzag spacers. A solute with a Schmidt number of 600 dissolving from the wall and channel Reynolds numbers up to 1683 were considered. Time averaging and Fourier analysis were performed to gain insight into the dynamics of the different flow regimes encountered, ranging from steady flow to vortex shedding behind the spacer filaments. The relationship between vortex shedding, pressure drop, and mass-transfer enhancement was explored. It was found that, at a Reynolds number between 526 and 841, the flow becomes unsteady. As the Reynolds number increases, the region of maximum mass transfer moves upstream from the wall opposite the downstream spacer to the region between spacers. The regions of high mass transfer are correlated not only to those of high shear rate but also to those where the fluid flow is toward the wall. Two main causes for mass-transfer enhancement were found: increased wall shear and an inflow of lower concentration fluid into the boundary layer, with the latter dominating unsteady mass-transfer enhancement for membrane filtration of sodium chloride.

Turbulent mixing in the outer solar nebula

Abstract: The effects of turbulence on the mixing of gases and dust in the outer solar nebula are examined using three-dimensional MHD calculations in the shearing-box approximation with vertical stratification. The turbulence is driven by the magnetorotational instability. The magnetic and hydrodynamic stresses in the turbulence correspond to an accretion time at the midplane about equal to the lifetimes of T Tauri disks, while accretion in the surface layers is 30 times faster. The mixing resulting from the turbulence is also fastest in the surface layers. The mixing rate is similar to the rate of radial exchange of orbital angular momentum, so that the Schmidt number is near unity. The vertical spreading of a trace species is well matched by solutions of a damped wave equation when the flow is horizontally averaged. The damped wave description can be used to inexpensively treat mixing in one-dimensional chemical models. However, even in calculations reaching a statistical steady state, the concentration at any given time varies substantially over horizontal planes, due to fluctuations in the rate and direction of the transport. In addition to mixing species that are formed under widely varying conditions, the turbulence intermittently forces the nebula away from local chemical equilibrium. The different transport rates in the surface layers and interior may affect estimates of the grain evolution and molecular abundances during the formation of the solar system.

Turbulent mass transfer through a flat shear-free surface

Abstract: Mass transfer through the flat shear-free surface of a turbulent open-channel flow is investigated over a wide range of Schmidt number (1 ≤ Sc ≤ 200) by means of large-eddy simulations using a dynamic subgrid-scale model. In contrast with situations previously analysed using direct numerical simulation, the turbulent Reynolds number Re is high enough for the near-surface turbulence to be fairly close to isotropy and almost independent of the structure of the flow in the bottom region (the statistics of the velocity field are identical to those described by I. Calmet & J. Magnaudet J. Fluid Mech. vol. 474, 2003, p. 355). The main statistical features of the concentration field are analysed in connection with the structure of the turbulent motion below the free surface, characterized by a velocity macroscale u and an integral length scale L. All near-surface statistical profiles are found to be Sc-independent when plotted vs. the dimensionless coordinate Sc 1/2 yu/v (y is the distance to the surface and v is the kinematic viscosity). Mean concentration profiles are observed to be linear throughout an inner diffusive sublayer whose thickness is about one Batchelor microscale, i.e. LSc -1/2 Re -3/4 . In contrast, the concentration fluctuations are found to reach their maximum near the edge of the outer diffusive layer which scales as LSc -1/2 Re -1/2 . Instantaneous views of the near-surface isovalues of the concentration and vertical velocity are used to reveal the influence of the Schmidt number. In particular, it is observed that at high Schmidt number, the tiny concentration fluctuations that subsist in the diffusive sublayer just mirror the divergence of the two-component surface velocity field. Co-spectra of concentration and vertical velocity fluctuations indicate that the main contribution to the turbulent mass flux is provided by eddies whose horizontal size is close to L, which strongly supports the view that the mass transfer is governed by large-scale structures. The dimensionless mass transfer rate is observed to be proportional to Sc -1/2 over the whole range of Schmidt number. Based on a frequency analysis of the concentration equation and on the Sc -1/2 Re -3/4 scaling of the diffusive sublayer, it is shown that the mass transfer rate at a given Sc is proportional to 1/4 , being the variance of the divergence of the surface velocity field. This yields dimensionless mass transfer rates of the form αSc -1/2 Re -1/4 , where the value of a is shown to result from both the kinematic blocking of the vertical velocity and the viscous damping of the horizontal vorticity components induced by the free surface.

Schmidt number effects in dissipative particle dynamics simulation of polymers.

Abstract: Simulation studies for dilute polymeric systems are presented using the dissipative particle dynamics method. By employing two different thermostats, the velocity-Verlet and Lowe’s scheme, we show that the Schmidt number (Sc) of the solvent strongly affects nonequilibrium polymeric quantities. The fractional extension of wormlike chains subjected to steady shear is obtained as a function of Sc. Poiseuille flow in microchannels for fixed polymer concentration and varying number of repeated units within a chain is simulated. The nonuniform concentration profiles and their dependence on Sc are computed. We show the effect of the bounce-forward wall boundary condition on the depletion layer thickness. A power law fit of the velocity profile in stratified Poiseuille flow in a microchannel yields wall viscosities different from bulk values derived from uniform, steady plane Couette flow. The form of the velocity profiles indicates that the slip flow model is not useful for the conditions of these calculations.

Toward a Unified Scaling Relation for Interfacial Fluxes

Abstract: Interfacial fluxes, that is, gas exchange at the water–atmosphere interface and benthic fluxes at the sediment–water interface, are often parameterized in terms of wind speed or turbulent friction velocity, with numerous empirical relationships obtained from individual experiments. The present study attempts to combine the general outcome of such experiments at both interfaces into a universal scaling relation for the thicknesses of the viscous and diffusive sublayers in terms of the Kolmogorov and Batchelor length scales, respectively. Transfer velocities can then be described in terms of the Schmidt number of the respective tracer and in terms of the turbulence dissipation rate. Applying law-of-the-wall scaling to convert dissipation rates into an appropriate friction velocity estimate results in a mechanistic description of the transfer velocity, which is comparable to common empirical parameterizations. It is hypothesized, however, that the dissipation rate and hence the directly estimated level of turbulence provide a more appropriate variable for the parameterization of interfacial fluxes than wind speed or turbulent friction velocity inferred from law-of-the-wall scaling.

Theoretical study of chemical reaction effects on vertical oscillating plate with variable temperature

Abstract: An exact solution to the ∞ow of a viscous incompressible unsteady ∞ow past an inflnite vertical oscillating plate with variable temperature and mass difiusion is presented here, taking into account of the homogeneous chemical reaction of flrst-order. Both the plate temperature and the concentration level near the plate are raised linearly with respect to time. The dimensionless governing equations has been obtained by the Laplace transform method, when the plate is oscillating harmonically in its own plane. The efiects of velocity and concentration are studied for difierent parameters like phase angle, chemical reaction parameter, thermal Grashof number, mass Grashof number, Schmidt number and time are studied. The solutions are valid only for small values of time t. It is observed that the velocity increases with decreasing phase angle !t or chemical reaction parameter.

Effect of spatial filtering on the Schmidt decomposition of entangled photons

Abstract: A simple analytic decomposition of the spatially entangled two-photon field allows us to generalize the earlier results of Law and Eberly [Phys. Rev. Lett. 92, 127903 (2004)] to more realistic experimental geometries of spontaneous parametric down-conversion. We quantify analytically how spatial filtering reduces the Schmidt number or dimensionality of the two-photon entanglement from a 'generated' value to a generally much lower 'usable or detected' value, for both collinear and noncollinear phase matching. We also discuss the intimate relation between the (two-photon) Schmidt number and the classical (one-photon) concept of etendue or geometric extent.

Numerical Solution of Mass Transfer Efiects on Unsteady Flow Past an Accelerated Vertical Porous Plate with Suction

Abstract: The unsteady free convection and mass transfer boundary layer ∞ow past an accelerated inflnite vertical porous ∞at plate with suction is con- sidered when the plate accelerates in its own plane. The governing equations are solved both analytically and numerically using flnite difierence scheme. The ∞ow phenomenon has been characterized with the help of ∞ow parameters such as suction parameter (a), porosity parameter (fi), Grashof number (Gr, Gc), Schmidt number (Sc) and Prandtl number (Pr). The efiects of these parameters on the velocity fleld, temperature fleld and concentration distribu- tion have been studied and the results are presented graphically and discussed quantitatively. This type of problem is signiflcantly relevant to geophysical and astrophysical studies.

Transient radiative hydromagnetic free convection flow past an impulsively started vertical plate with uniform heat and mass flux

Abstract: The interaction of free convection with thermal radiation of viscous incompressible MHD unsteady ∞ow past an impulsively started vertical plate with uniform heat and mass ∞ux is analyzed. This type of problem flnds application in many technological and engineering flelds such as rocket propulsion systems, space craft re-entry aerothermodynamics, cosmical ∞ight aerodynamics, plasma physics, glass production and furnace engineering .The Rosseland approximation is used to describe the radiative heat transfer in the limit of the optically thin ∞uid. The non-linear, coupled equations are solved using an implicit flnite difierence scheme of Crank-Nicolson type. Velocity, temperature and concentration of the ∞ow have been presented for various parameters such as thermal Grashof number, mass Grashof number, Prandtl number, Schmidt number, radiation parameter and magnetic parameter. The local and average skin friction, Nusslet number and Sherwood number are also presented graphically. It is observed that, when the radiation parameter increases the velocity and temperature decrease in the boundary layer.

Variable Turbulent Schmidt Number Formulation for Scramjet Applications

Abstract: In high speed engines, thorough turbulent mixing of fuel and air is required to obtain high performance and high efficiency Thus, the ability to predict turbulent mixing is crucial in obtaining accurate numerical simulation of an engine and its performance Current state of the art in CFD simulation is to assume both turbulent Prandtl number and Schmidt numbers to be constants However, since the mixing of fuel and air is inversely proportional to the Schmidt number, a value of 045 for the Schmidt number will produce twice as much diffusion as that with a value of 09 Because of this, current CFD tools and models have not been able to provide the needed guidance required for the efficient design of a scramjet engine The goal of this investigation is to develop the framework needed to calculate turbulent Prandtl and Schmidt numbers as part of the solution This requires four additional equations: two for the temperature variance and its dissipation rate and two for the concentration variance and its dissipation rate In the current investigation emphasis will be placed on studying mixing without reactions For such flows, variable Prandtl number does not play a major role in determining the flow This, however, will have to be addressed when combustion is present The approach to be used is similar to that used to develop the k-zeta model In this approach, relevant equations are derived from the exact Navier-Stokes equations and each individual correlation is modeled This ensures that relevant physics is incorporated into the model equations This task has been accomplished The final set of equations have no wall or damping functions Moreover, they are tensorially consistent and Galilean invariant The derivation of the model equations is rather lengthy and thus will not be incorporated into this abstract, but will be included in the final paper As a preliminary to formulating the proposed model, the original k-zeta model with constant turbulent Prandtl and Schmidt numbers is used to model the supersonic coaxial jet mixing experiments involving He, O2 and air

Lie Group Analysis of Natural Convection Heat and Mass Transfer in an Inclined Surface

Abstract: Natural convection heat transfer fluid flow past an inclined s emi- infinite surface in the presence of solute concentration is i nvestigated by Lie group analysis. The governing partial differential equati ons are reduced to a system of ordinary differential equations by the translat ion and scaling symmetries. An exact solution is obtained for translation symmetry and numerical solutions for scaling symmetry. It is found that t he velocity increases and temperature and concentration of the fluid decrease with an increase in the thermal and solutal Grashof numbers. The velocity and concentration of the fluid decrease and temperature increases with increase in th e Schmidt number.

Scaling Laws for Free Turbulent Gas Jets and Diesel-Like Sprays

Abstract: Scaling laws for free turbulent gas jets and diesel-like sprays are deduced and experimentally validated. The analysis is based on basic conservation equations and experimental evidence. As a new contribution, the effect of the Schmidt number on the scaling laws is analyzed and included, which leads to a more general set of normalized parameters. By analyzing the scaling laws, it is possible to obtain a clear comprehension of gas-jet or diesel-spray behavior, as well as an understanding of the relationship between input and output parameters. Two new parameters are introduced that characterize mass and momentum transfer in the radial direction of the gas jet or diesel spray, thus providing valuable information about the mixing process.

Radiation effect with simultaneous thermal and mass diffusion in mhd mixed convection flow from a vertical surface with ohmic heating

Abstract: The effects of radiation on heat transfer in MHD mixed convection flow and mass transfer past an infinite vertical plate with Ohmic heating and viscous dissipation have been discussed. Approximate solutions have been derived for the velocity, temperature field, concentration profiles, skin friction and rate of heat transfer using multi-parameter perturbation technique. The obtained results are discussed with the help of graphs to observe the effect of various parameter like Schmidt number (Sc), Prandtl number (Pr), Magnetic parameter (M) and radiation parameter (F), taking two cases viz. Case I: when Gr > 0 (i.e. flow on cooled plate) and Case II: Gr < 0 (i.e. flow on heated plate).

Velocity and Concentration Distributions of Round and Plane Turbulent Jets

Abstract: The analytical solutions for the velocity distribution of turbulent round and plane jets described in the classical textbook of Schlichting (Boundary Layer Theory 7th edition (1979)) based on boundary-layer approximations are well-known, and have provided the fundamental understanding of the mechanics of turbulent jets. However, the scaling coefficients involved were not well quantified as discussed recently by Mathieu and Scott (An Introduction to Turbulent Flow(2000)). In this paper, it is shown that the coefficients can be better determined by the available experimental measurements in the literature. Furthermore, by assuming that the turbulent diffusivity relates to the eddy viscosity, it is shown that closed-form analytical solutions can also be obtained for the scalar concentration distribution in addition to the velocity distribution. The turbulent Schmidt number is found to be less than 1 for both plane and round jets, and close to the isotropic turbulence value of 0·7 in the round jet case.

Observations and theories of Polar Mesospheric Summer Echoes at a Bragg wavelength of 16 cm

Abstract: [1] We present measurements of Polar Mesospheric Summer Echoes, PMSE, at the very short Bragg wavelength of 16 cm which occur infrequently. The measurements were carried out with the EISCAT 930 MHz UHF radar. Part of the data were taken under the influence of HF heating. A comprehensive comparison of the measurements with the theory of turbulence including enhancement of the Schmidt number is carried out, but other theories are also considered. Estimates of the energy dissipation rates inferred from the signal spectral widths are used to calculate Batchelor scale lengths as a function of the Schmidt number. Hill's multipolar diffusion model is used to calculate the diffusion rates (which depend on the charge number of ice particles of nanometer size radius) leading to estimates of the Schmidt numbers. It is argued that the use of the slow diffusion coefficient in the calculations should give conservative estimates, i.e., lower bounds, of the necessary ice charge numbers to explain the measurements, the condition for enhanced scattering being that the Bragg scale of the radar should be greater than the Batchelor scale. Based on information from other experiments published in the literature, e.g., the charge number of mesospheric ice particles, and theoretical considerations, the main conclusion of this investigation is that none of the most prominent theories can explain satisfactorily the measurements unless charge numbers in excess of 10 electrons for the measured wide spectra and at least in excess of 100s of electrons for the measured narrow spectra are assumed. The HF heating effect on the mesosphere appears to have a similar influence on PMSE at a Bragg wavelength of 16 cm as it has at greater wavelengths, namely a weakening of PMSE during the heater-on periods and a recovery during the heater off-periods. This behaviour is as expected given the rapidity and large amount of electron heating that the HF wave produces with the consequent rapid and large enhancement of the electron diffusion rate during heater-on periods regardless of the electron diffusion model or reference to any particular model of PMSE.

New model for turbulent mass transfer and its application to the simulations of a pilot-scale randomly packed column for CO2-NaOH chemical absorption

Abstract: A complex model for simulating the mass transfer process in gas−liquid system is introduced by combining the computational fluid dynamics (CFD) model, the turbulent mass transfer model with the −ec equations for its closure, and the heat balance equation. By the proposed complex model, the axial and radial concentration distributions along the packed column can be obtained without assuming the “turbulent Schmidt number” or experimentally measuring the turbulent mass transfer diffusivity. The validation of the proposed model is tested by its application to a pilot-scale randomly packed 7 m high chemical absorption column with a 0.1 m internal diameter packed with 1/2 in. ceramic Berl saddles for CO2 removal by NaOH aqueous solutions. The simulated results are compared with the experimental data by Tontiwachwuthikul et al. (Chem. Eng. Sci. 1992, 47 (2), 381−390). Satisfactory agreement between the simulation and experiment in terms of the temperature and concentration distributions along the column height i...