Papers by C. Schellenberg
Spiral-wound membrane modules used in water treatment for water reuse and desalination make use o... more Spiral-wound membrane modules used in water treatment for water reuse and desalination make use of spacer meshes for keeping the membrane leaves apart and for enhancing the mass transfer. Computational fluid dynamics (CFD) has gained importance in the design of new spacers with optimized hy-drodynamic characteristics, but this requires a precise description of the spacer geometry. This study developed a method to obtain accurate three-dimensional (3-D) geometry representations for any given spacer design from X-ray computed tomography (CT) scans. The method revealed that the filaments of industrial spacers have a highly variable cross-section size and shape, which impact the flow characteristics in the feed channel. The pressure drop and friction factors were calculated from numerical simulations on five commercially available feed spacers used in practice. Model solutions compared well to experimental data measured using a flow cell for average velocities up to 0.2 m/s, as used in industrial reverse osmosis and nanofiltration membrane operations. A newly-proposed spacer geometry with alternating strand thickness was tested, which was found to yield a lower pressure drop while being highly efficient in converting the pumping power into membrane shear. Numerical model solutions using CFD with geometries from CT scans were closer to measurements than those obtained using the traditional circular cross-section strand simplification, indicating that CT scans are very well suitable to approximate real feed spacer geometries. By providing detailed insight on the spacer filament shape, CT scans allow better quantification of local distribution of velocity and shear, possibly leading to more accurate estimations of fouling and concentration polarization.
The porosity of spacer-filled feed channels influences the hydrodynamics of spiral-wound membrane... more The porosity of spacer-filled feed channels influences the hydrodynamics of spiral-wound membrane systems and impacts the overall performance of the system. Therefore, an exact measurement and a detailed understanding of the impact of the feed channel porosity is required to understand and improve the hydrodynamics of spiral-wound membrane systems applied for desalination and wastewater reuse. The objectives of this study were to assess the accuracy of porosity measurement techniques for feed spacers differing in geometry and thickness and the consequences of using an inaccurate method on hydrodynamic predictions, which may affect permeate production. Six techniques were applied to measure the porosity namely, three volumetric techniques based on spacer strand count together with a cuboidal (SC), cylindrical (VCC) and ellipsoidal volume calculation (VCE) and three independent techniques based on volume displacement (VD), weight and density (WD) and computed tomography (CT) scanning. The CT method was introduced as an alternative for the other five already existing and applied methods in practice. Six feed spacers used for the porosity measurement differed in filament thickness, angle between the filaments and mesh-size. The results of the studies showed differences between the porosities, measured by the six methods. The results of the microscopic techniques SC, VCC and VCE deviated significantly from measurements by VD, WD and CT, which showed similar porosity values for all spacer types. Depending on the maximum deviation of the porosity measurement techniques from À6% to þ6%, (i) the linear velocity deviations were À5.6% and þ6.4% respectively and (ii) the pressure drop deviations were À31% and þ43% respectively, illustrating the importance of an accurate porosity measurement. Because of the accuracy and standard deviation, the VD and WD method should be applied for the porosity determination of spacer-filled channels, while the CT method is recommended for numerical modelling purposes. The porosity has a linear relationship with the flow velocity and a superlinear effect on the pressure drop. Accurate porosity data are essential to evaluate feed spacer performance in spiral-wound membrane systems. Porosity of spacer-filled feed channels has a strong impact on membrane performance and biofouling impact.
The reaction of azomethine dyes (1 ag) with malonodinitrile (2) gives dicyanomethylene-pyrazolin-... more The reaction of azomethine dyes (1 ag) with malonodinitrile (2) gives dicyanomethylene-pyrazolin-5-one (4) which immediately reacts with the eliminated anilines by HCN-amine exchange giving the deeply coloured arylamino-cyanomethylene-pyrazolinones (5 ag). Structural investigations and a study of the absorption characteristic are described.
Surface and Interface Analysis, 1999
In this study Ðlms of core-shell-structured latex particles are investigated by dynamic scanning ... more In this study Ðlms of core-shell-structured latex particles are investigated by dynamic scanning force microscopy "tapping mode imagingÏ. Polymer dispersions with cores of the low-viscosity polymer poly(2-ethylhexyl methacrylate) (PEtHMA) and shells of the cross-linked rubber poly(n-butyl acrylate) (PBA) were spread on a Ñat mica surface to form a monolayer. Topographic as well as phase images were recorded at di †erent amplitudes and damping factors (so-called soft and hard tapping). The topographic images show a continuous matrix formed by the particles, but a clear contrast of individual particles in the phase images could be obtained at high damping factors of the cantilever oscillation. The soft cores embedded in the matrix of the shell polymers caused a perceptible reduction of the phase of oscillation. Consequently, the total particle appeared soft enough because it allowed deformation of the soft cores below.
Langmuir, 1999
... C. Schellenberg, S. Akari, M. Regenbrecht, K. Tauer, FM Petrat, § and M. Antonietti* ... more ... C. Schellenberg, S. Akari, M. Regenbrecht, K. Tauer, FM Petrat, § and M. Antonietti* . Max-Planck-Institut für Kolloid-und Grenzflächenforschung, Kantstrasse 55, D-14513 Teltow-Seehof, Germany. Langmuir , 1999, 15 (4), pp 12831290. ...
Journal of Dispersion Science and Technology, 1999
... Material Science and Engineering Reports 21 101 (1997) 3) M. Antonietti, S. Akari, M. Regenbr... more ... Material Science and Engineering Reports 21 101 (1997) 3) M. Antonietti, S. Akari, M. Regenbrecht, e. Schellenberg, K. Tauer, Langmuir, submitted 4) L. Valera De La Rosa, ED Sudol, MS EIAasser, A. Klein, J.Polym.Sci.Polym.Chem. 34,461 (1996) 5) HU Moritz, in: "Polymer ...
Colloid & Polymer Science, 1999
Spiral-wound membrane modules used in water treatment for water reuse and desalination make use o... more Spiral-wound membrane modules used in water treatment for water reuse and desalination make use of spacer meshes for keeping the membrane leaves apart and for enhancing the mass transfer. Computational fluid dynamics (CFD) has gained importance in the design of new spacers with optimized hy-drodynamic characteristics, but this requires a precise description of the spacer geometry. This study developed a method to obtain accurate three-dimensional (3-D) geometry representations for any given spacer design from X-ray computed tomography (CT) scans. The method revealed that the filaments of industrial spacers have a highly variable cross-section size and shape, which impact the flow characteristics in the feed channel. The pressure drop and friction factors were calculated from numerical simulations on five commercially available feed spacers used in practice. Model solutions compared well to experimental data measured using a flow cell for average velocities up to 0.2 m/s, as used in industrial reverse osmosis and nanofiltration membrane operations. A newly-proposed spacer geometry with alternating strand thickness was tested, which was found to yield a lower pressure drop while being highly efficient in converting the pumping power into membrane shear. Numerical model solutions using CFD with geometries from CT scans were closer to measurements than those obtained using the traditional circular cross-section strand simplification, indicating that CT scans are very well suitable to approximate real feed spacer geometries. By providing detailed insight on the spacer filament shape, CT scans allow better quantification of local distribution of velocity and shear, possibly leading to more accurate estimations of fouling and concentration polarization.
Uploads
Papers by C. Schellenberg