@article{roberts_carbonell_saez_2000, title={Gas-lift reactors for rapid reactions with appreciable gas consumption}, volume={23}, DOI={10.1002/(sici)1521-4125(200001)23:1<80::aid-ceat80>3.0.co;2-m}, abstractNote={Gas-lift reactors offer important advantages for a number of gas/liquid and gas/liquid/solid reactions. However, the design and operation of these reactors can be complex when there is a substantial change in the molar gas flow rate along the length of the reactor, e.g., when a gaseous reactant is converted into a liquid product. In this situation, there is a strong coupling between reactor hydrodynamics and reaction kinetics, which arises from the fact that the rate of liquid circulation through the reactor and the longitudinal profile of gas holdup in the riser are mutually dependent. Several one-dimensional models have been developed to describe kinetic/hydrodynamic coupling in gas-lift reactors. These models offer useful insights into the parameters that affect reactor performance. The models can also be used to explore different approaches to scale-up.}, number={1}, journal={Chemical Engineering & Technology}, author={Roberts, G. W. and Carbonell, R. G. and Saez, A. E.}, year={2000}, pages={80–87} }
 @article{littlejohn_grant_saez_2000, title={Mechanisms for the removal of calcium phosphate deposits in turbulent flow}, volume={39}, ISSN={["0888-5885"]}, DOI={10.1021/ie990624h}, abstractNote={This work investigates the mechanisms for the removal of calcium phosphate deposits from stainless steel tubing in turbulent flows. Two types of deposits were analyzed:  brushite (dicalcium phosphate dihydrate, DCPD) and a mixture of DCPD/hydroxyapatite (HAP). Cleaning studies were carried out at pHs ranging from 2.85 to 10. The data were analyzed by means of a mathematical model that incorporates the effects of interfacial dissolution and mass transfer. The results show that the HAP/DCPD cleaning rate is influenced both by the kinetics of the interfacial dissolution and by mass transfer. Within the same range of experimental conditions, the rate-limiting mechanism for DCPD removal was the abrasion of the solid by shear stresses. In this case, the interfacial dissolution process plays the role of decreasing the structural integrity of the deposit. These findings show that the removal mechanism of the HAP/DCPD mixture differs significantly from the behavior of individual components.}, number={4}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Littlejohn, F and Grant, CS and Saez, AE}, year={2000}, month={Apr}, pages={933–942} }
 @article{kabin_withers_grant_carbonell_saez_2000, title={Removal of solid organic films from rotating disks using emulsion cleaners}, volume={228}, ISSN={["0021-9797"]}, DOI={10.1006/jcis.2000.6832}, abstractNote={Measurements have been made of the rate of removal of a solid organic film (phenanthrene) from the surface of a rotating disk using emulsions containing water, the nonionic surfactant Tween 20, and d-limonene as the organic phase. The results show that phenanthrene removal initially occurs by the uptake of phenanthrene into the emulsion drops as small aggregates. Simultaneously, the organic phase penetrates into the phenanthrene film, diminishing the adhesive force between the film and the substrate. After sufficient time, the phenanthrene film detaches from the rotating disk surface as a solid. This detachment mechanism accounts for the vast majority of the phenanthrene removal ( approximately 90%). Initial solubilization rates were analyzed using two solubilization models. Both models assume that phenanthrene removal occurs via a mass transfer limited removal of phenanthrene-laden emulsion drops from the phenanthrene film surface into the bulk solution. One model treats the emulsion as homogeneous while the other accounts for the finite size of the emulsion droplets. The latter model was also used to relate the flux of organic phase impacting the phenanthrene film to the detachment times. Copyright 2000 Academic Press.}, number={2}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Kabin, JA and Withers, ST and Grant, CS and Carbonell, RG and Saez, AE}, year={2000}, month={Aug}, pages={344–358} }
 @article{marquez_saez_carbonell_roberts_1999, title={Coupling of hydrodynamics and chemical reaction in gas-lift reactors}, volume={45}, DOI={10.1002/aic.690450220}, abstractNote={Abstract}, number={2}, journal={AIChE Journal}, author={Marquez, H. A. and Saez, A. E. and Carbonell, R. G. and Roberts, G. W.}, year={1999}, pages={410–423} }
 @article{colberg_saez_grant_hutchison_hesterberg_1999, title={Dynamic hydration of phospholipid films in aqueous environments}, volume={151}, ISSN={["0927-7757"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0344267705&partnerID=MN8TOARS}, DOI={10.1016/S0927-7757(98)00842-5}, abstractNote={A dynamic study of the hydration of phospholipid films attached to solid substrates when exposed to liquid water at room temperature is presented. The phospholipids used were 1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine (DPPE), and a modification of DPPE with a fluorescent molecular probe: n-(5-fluoresceinthicarbamoyl)-1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine, triethylammonium salt (FITC-DPPE). Three different experimental techniques were used: rates of hydration were measured by depositing the phospholipid film on a quartz crystal microbalance (QCM), total internal reflection fluorescence (TIRF) studies were carried out with FITC-DPPE films deposited on the internal surface of a cylindrical quartz tube, and X-ray diffraction analysis was used to determine possible changes of the film’s crystalline structure during hydration. The DPPE films exhibited different successive hydration stages: within the first 2 h, the films uniformly hydrate towards a limiting water uptake (short-time behavior); however, at one point, hydration rates suddenly increase and the hydration process continues for longer periods of time, of the order of 24 h. No evidence of change in the film crystalline structure was found when dry and hydrated DPPE films were analyzed by wide-angle X-ray diffraction. The FITC-DPPE films showed a completely different hydration pattern: water uptake reached a maximum value at short times and then decreased continuously until an asymptotic value was reached. The TIRF results on FITC-DPPE films show that the evolution of fluorescence with time closely resembles the hydration results obtained in the QCM. This is attributed to the self quenching occurring in the phospholipid films.}, number={3}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Colberg, MT and Saez, AE and Grant, CS and Hutchison, K and Hesterberg, D}, year={1999}, month={Jul}, pages={483–495} }
 @article{see_roberts_saez_1999, title={Effect of drag and frictional losses on the hydrodynamics of gas-lift reactors}, volume={45}, ISSN={["1547-5905"]}, DOI={10.1002/aic.690451121}, abstractNote={The purpose of this communication is to examine several assumptions concerning the drag and frictional losses in gas-lift reactors that are common to the Saez et al. (1998) and Marquez et al. (1999) models, and to some other published models. These assumptions are as follows. (1) The friction factor in the downcomer must be adjusted upward with respect to correlations for fully developed, single-phase flow in pipes in order to account for developing flow. (2) Mechanical energy losses in the gas/liquid separator and the straightening vanes can be neglected. (3) Frictional losses in the riser are adequately described by the correlation of Akita et al. (1988), which explicitly accounts for two-phase flow.}, number={11}, journal={AICHE JOURNAL}, author={See, KH and Roberts, GW and Saez, EA}, year={1999}, month={Nov}, pages={2467–2471} }
 @article{kauser_dos santos_delgado_muller_saez_1999, title={Flow of mixtures of poly(ethylene oxide) and hydrolyzed polyacrylamide solutions through porous media}, volume={72}, DOI={10.1002/(SICI)1097-4628(19990509)72:6<783::AID-APP6>3.3.CO;2-5}, abstractNote={In this work, the porous media flow of polymer solutions of poly(ethylene oxide) (PEO), hydrolyzed polyacrylamide (HPAA), and their blends is investigated. Aqueous solutions of PEO exhibit critical extension thickening when flowing through porous media. HPAA solutions also exhibit critical extension thickening in excess salt environments, but their behavior changes to a more gradual extension thickening when dissolved in deionized water. The mixtures of solutions of HPAA and PEO therefore vary its porous media flow behavior, depending on the ionic environment. In deionized water, a critical extension thickening similar to that obtained with PEO is still observed when HPAA is mixed in at concentrations low enough so that its apparent viscosity does not mask the influence of PEO. In the presence of salt, only a critical extension thickening is observed, which is attributed to transient network formation of both PEO and HPAA molecules. The mixtures generally exhibit a less critical behavior and display a lower than expected sensitivity of the onset Reynolds number for extension thickening with concentration. The results presented herein indicate that interspecies molecular interactions through transient network formation and the associated flow modification play a major role in determining the complex non-Newtonian flow behavior of these polymer solutions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 783–795, 1999}, number={6}, journal={Journal of Applied Polymer Science}, author={Kauser, N. and Dos Santos, L. and Delgado, M. and Muller, A. J. and Saez, A. E.}, year={1999}, pages={783–795} }
 @article{marquez_amend_carbonell_saez_roberts_1999, title={Hydrodynamics of gas-lift reactors with a fast, liquid-phase reaction}, volume={54}, ISSN={["0009-2509"]}, DOI={10.1016/S0009-2509(98)00351-0}, abstractNote={The reactive absorption of CO2 into concentrated KOH solutions was studied in an external-loop, gas-lift reactor. Three different inlet gas compositions were used: air, 50–50 vol% air–CO2, and pure CO2. The downcomer liquid velocity and the axial profile of the cross-sectionally averaged gas holdup in the riser were measured. The reaction is so fast that the CO2 is consumed appreciably along the riser, and this causes a significant reduction in the liquid circulation relative to a system with no reaction. A one-dimensional, pseudo-steady-state model has been developed to describe the interactions of hydrodynamics, mass transfer, and chemical reaction for the bubbly flow regime in the riser. The model considers mass transfer from the gas to the liquid phase and its enhancement due to the chemical reaction, and is based on the spatially averaged equations of continuity, momentum, and macroscopic mechanical energy. The rate of liquid circulation, and the axial variation of gas holdup, gas composition, pressure, and gas and liquid velocity, are predicted. The gas/liquid mass transfer coefficient and the bubble radius at the sparger, neither of which was known a priori, were used to minimize the error of the data with respect to the model.}, number={13-14}, journal={CHEMICAL ENGINEERING SCIENCE}, author={Marquez, MA and Amend, RJ and Carbonell, RG and Saez, AE and Roberts, GW}, year={1999}, month={Jul}, pages={2263–2271} }
 @article{kabin_saez_grant_carbonell_1999, title={Removal rates of major and trace components of an organic film using aqueous nonionic surfactant solutions}, volume={38}, ISSN={["0888-5885"]}, DOI={10.1021/ie980587e}, abstractNote={This work examines the cleaning of organic films composed of a primary component (abietic acid) mixed with trace amounts of a second contaminant (benzoic acid). Films were removed from a rotating disk in the presence of aqueous solutions of two poly(ethylene glycol) alkyl ether surfactants: C 12 E 5 and C 16 E 8 . With C 12 E 5 the abietic acid was removed from the disk in three successive cleaning stages - solubilization, shear removal, and rollup - whereas the benzoic acid was almost completely removed during the initial solubilization stage. Also, with C 12 E 5 the results show that the micellar solubilization rate of the trace contaminant is directly proportional to its concentration in the film. The ratio of the molar removal rates of benzoic acid to abietic acid with C 12 E 5 is an order of magnitude greater than the ratio of the mole fractions of the two components in the contaminant film. Solutions of C 16 E 8 removed the abietic acid by only the solubilization and rollup stages. The ratio of the molar removal rates of benzoic acid to abietic acid with C 16 E 8 was equal to the ratio of the mole fractions of the two components in the contaminant film. A mathematical model is proposed to quantify the simultaneous removal of benzoic acid and abietic acid during the micellar solubilization stage. The model takes into account the mass-transfer rate between the film and the bulk solution, as well as the micellization rates at the film/surfactant solution interface. The model adequately represents the experimental data.}, number={3}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Kabin, JA and Saez, AE and Grant, CS and Carbonell, RG}, year={1999}, month={Mar}, pages={683–691} }
 @article{colberg_carnes_saez_grant_hutchinson_hesterberg_1998, title={Hydration and removal of supported phospholipid films in aqueous surfactant solutions}, volume={327}, ISSN={["0040-6090"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032141167&partnerID=MN8TOARS}, DOI={10.1016/s0040-6090(98)00638-5}, abstractNote={Dynamic studies of the hydration and removal of phospholipid films attached to solid substrates were performed. The phospholipids used were 1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine (DPPE), and a modification of DPPE containing a fluorescent molecular probe: n-(5-fluoresceinthicarbamoyl)-1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine, triethylammonium salt (FITC-DPPE). The phospholipid films were exposed to water and aqueous solutions of the anionic surfactant sodium dodecyl sulfate (SDS). The film mass was determined as a function of time by means of a quartz crystal microbalance (QCM). The crystalline structure of the film during the hydration process was analyzed by means of wide-angle X-ray diffraction. At low surfactant concentrations (below 20% of the critical micelle concentration (CMC)), the presence of surfactant increased the hydration rate of the film, as well as its maximum water uptake. At surfactant concentrations as low as 50% of the CMC, competitive hydration and removal of the phospholipid film were observed. X-Ray diffraction measurements show that the crystal structure of the DPPE films did not change significantly upon exposure to water and surfactant solutions. In contrast, FITC-DPPE films exhibited changes in the long-range spacing of their crystalline structure upon hydration.}, number={1998 Aug. 31}, journal={THIN SOLID FILMS}, author={Colberg, MT and Carnes, K and Saez, AE and Grant, CS and Hutchinson, K and Hesterberg, D}, year={1998}, month={Aug}, pages={247–251} }
 @article{saez_marquez_roberts_carbonell_1998, title={Hydrodynamic model for gas-lift reactors}, volume={44}, ISSN={["0001-1541"]}, DOI={10.1002/aic.690440619}, abstractNote={Abstract}, number={6}, journal={AICHE JOURNAL}, author={Saez, AE and Marquez, MA and Roberts, GW and Carbonell, RG}, year={1998}, month={Jun}, pages={1413–1423} }
 @article{ventura-medina_pironti_saez_1998, title={Liquid phase mixing in a slurry bubble column with draft tube}, volume={163}, ISSN={["0098-6445"]}, DOI={10.1080/00986449808912352}, abstractNote={Abstract In this work we characterize liquid phase mixing in a 150 L bubble column with a draft tube (internal airlift configuration) for a water-air-sand system at high solid concentrations. Liquid mixing is assessed by measuring the evolution of sodium chloride concentration after a pulse of concentrated NaCl solution is injected. Tracer concentrations were measured by means of electrical conductivity probes. The experimental set up consists of a 0.29 m internal diameter, 3 m length Plexiglas column with a conical bottom (cone apex angle of 60°) and a concentric draft tube with 0.14 m internal diameter and 2 m length. The gas superficial velocity based on the cross section of the column vaired from 0.057 to 0.22 m/s. Sand particles of 280 μm in average size were used, with slurry concentrations ranging from 120 to 500 kg/m3. From the tracer outputs, circulation time (time between peaks of the response curve) and mixing time (time required to achieve a 95% homogeneous solution) were determined after the ...}, journal={CHEMICAL ENGINEERING COMMUNICATIONS}, author={Ventura-Medina, E and Pironti, FF and Saez, AE}, year={1998}, pages={219–231} }
 @article{kabin_tolstedt_saez_grant_carbonell_1998, title={Removal of organic films from rotating disks using aqueous solutions of nonionic surfactants: Effect of surfactant molecular structure}, volume={206}, DOI={10.1006/jcis.1998.5689}, abstractNote={In prior work, we examined the removal of abietic acid films from rotating fiberglass laminate disks by aqueous solutions of a nonionic surfactant. A three-stage cleaning mechanism was found, consisting successively of solubilization, shear-driven cleaning, and roll-up. We extend this work by exploring the influence of the surfactant molecular structure on the kinetics of the cleaning process. Five different poly(ethylene glycol) alkyl ether surfactants (CxEy) were used. Both the alkyl (x) and ethoxy (y) chain lengths were varied. Not all of the surfactants exhibited a three-stage cleaning mechanism. It was found that for surfactants with relatively high solubilization rates, the shear-driven cleaning stage did not occur. The selection of the most efficient surfactant depends on whether the surfactant concentration is below or above its critical micelle concentration (CMC). At submicellar concentrations, faster cleaning is obtained by surfactants that can induce shear-driven removal. At concentrations above the CMC, it is found that surfactant efficiency for a fixed alkyl or ethoxy chain length increases as the surfactant becomes more hydrophilic. This is attributed in part to the lower viscosity that the film achieves with the more hydrophilic surfactants due to their partitioning into the film, as well as their ability to carry water into the film. Copyright 1998 Academic Press.}, number={1}, journal={Journal of Colloid and Interface Science}, author={Kabin, J. A. and Tolstedt, S. L. and Saez, A. E. and Grant, Christine and Carbonell, R. G.}, year={1998}, pages={102–111} }
 @article{littlejohn_saez_grant_1998, title={Use of sodium polyaspartate for the removal of hydroxyapatite/brushite deposits from stainless steel tubing}, volume={37}, ISSN={["0888-5885"]}, DOI={10.1021/ie980006l}, abstractNote={This research investigates the use of sodium polyaspartate, a nontoxic, biodegradable polycarboxylic sequestrant, for removing calcium phosphate deposit consisting of hydroxyapatite (HAP) and brushite or dicalcium phosphate dihydrate (DCPD) from stainless steel surfaces. Cleaning studies show that the use of sodium polyaspartate under alkaline conditions significantly enhances the removal rates when compared to deionized water. In acidic solutions, sodium polyaspartate concentrations below 300 ppm inhibit removal of HAP/DCPD deposits whereas higher concentrations increase the removal rate. Comparative cleaning studies at alkaline pHs show that sodium polyaspartate cleans the surface at a rate comparable to sodium citrate but slower than in ethylenediaminetetraacetic acid. Supplementary dissolution experiments show that sodium polyaspartate enhances the HAP/DCPD dissolution rate while inhibiting the release of Ca2+. On the basis of these findings, we have concluded that sodium polyaspartate improves the HA...}, number={7}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Littlejohn, F and Saez, AE and Grant, CS}, year={1998}, month={Jul}, pages={2691–2700} }
 @article{carrington_tatham_odell_saez_1997, title={Macromolecular dynamics in extensional flows .1. Birefringence and viscometry}, volume={38}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(96)00999-8}, abstractNote={The opposed jets apparatus is used to investigate the dynamics of the coil-stretch transition of polymer solutions in an idealized stagnation point extensional flow-field. A linear CCD detector allows optical retardation profiles to be recorded as the strain rate is varied. A numerical transformation enables true birefringence profiles to be produced, which enable the assessment of localized molecular orientation and stretching around the stagnation point. High molecular weight, closely monodisperse aPS and PEO are studied in θ and good solvents. Flow modification effects are apparent to extremely low concentration (≈c∗/100). Under θ conditions, the width of the transition is consistent with the residual polydispersity. Simultaneous measurements of flow resistance enable the determination of the effective extensional viscosity. The increase in extensional viscosity due to molecular stretching is found to be of the order of the number of equivalent flexible units in the chain, after correction is made for the area of high molecular extension.}, number={16}, journal={POLYMER}, author={Carrington, SP and Tatham, JP and Odell, JA and Saez, AE}, year={1997}, month={Aug}, pages={4151–4164} }
 @article{carrington_tatham_odell_saez_1997, title={Macromolecular dynamics in extensional flows .2. The evolution of molecular strain}, volume={38}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(96)01080-4}, abstractNote={The opposed jets apparatus has been used to investigate the dynamics of the coil-stretch transition of polymer solutions in an idealized stagnation point extensional flow field. Flow simulations generated fluid strain profiles for different geometries. Assuming a molecular uncoiling model, true birefringence profiles have been converted to molecular strains for closely monodisperse, high molecular weight aPS under θ-conditions. This has enabled macromolecular deformation to be followed as a function of position and residence time. Non-linear hydrodynamic friction FENE dumb-bell simulations give qualitative agreement. Initially, molecular uncoiling is non-affine, consistent with changing hydrodynamic screening on extension. Deformation in a good solvent is more affine. Results are compared with PEO/water to investigate the effect of molecular parameters. The effective extensional viscosity has been ascertained by correction for the area of high molecular extension. The increase in extensional viscosity due to molecular stretching is substantial, of the order of the number of equivalent flexible units in the chain. © 1997 Elsevier Science Ltd.}, number={18}, journal={POLYMER}, author={Carrington, SP and Tatham, JP and Odell, JA and Saez, AE}, year={1997}, month={Sep}, pages={4595–4607} }
 @article{yan_saez_grant_1997, title={Removal of oil films from stainless steel tubes}, volume={43}, ISSN={["0001-1541"]}, DOI={10.1002/aic.690430127}, abstractNote={Abstract}, number={1}, journal={AICHE JOURNAL}, author={Yan, JF and Saez, AE and Grant, CS}, year={1997}, month={Jan}, pages={251–259} }
 @article{siquier_ronchetti_calderon_llaguno_saez_1997, title={Spatial distribution of gas and solid phases in conical slurry bubble columns}, volume={159}, ISSN={["0098-6445"]}, DOI={10.1080/00986449708936600}, abstractNote={In this work we perform an experimental study of the spatial distribution of phases in slurry bubble columns with conical distributors that have a volume comparable to that of the cylindrical section. Three different distributors were used whose apex angles were 13°, 22° and 34°. In gas-liquid operation, the gas holdups are axially uniform in the cylindrical section and decrease towards the wall, whereas in the conical section they increase towards the inlet. These trends are observed in the three cones for all the operating conditions explored. The solids distributions in the conical sections are qualitatively different depending on whether the operation is semibatch or continuous with respect to the flow of solid-liquid suspension: in semibatch operation, the concentration monotonically increases towards the bottom of the cone and exhibits a slight increase as the wall is approached; in continuous operation, an absolute maximum in solids concentration is obtained at a point located on the wall of the co...}, journal={CHEMICAL ENGINEERING COMMUNICATIONS}, author={Siquier, S and Ronchetti, A and Calderon, M and Llaguno, P and Saez, AE}, year={1997}, pages={173–190} }