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The extraction kinetics of polyphenols, which are leached from red vine leaves, are studied and evaluated using a laboratory robot and nonconventional processing techniques such as ultrasonic (US)-, microwave (MW)-, and pulsed electric field (PEF)-assisted extraction processes. The robotic high-throughput screening reveals optimal extraction conditions at a pH value of 2.5, a temperature of 56 °C, and a solvent mixture of methanol:water:HCl of 50:49:1 v/v/v. Nonconventional processing techniques, such as MW- and US-assisted extraction, have the fastest kinetics and produce the highest polyphenol yield. The non-conventional techniques yield is 2.29 g/L (MW) resp. 2.47 g/L (US) for particles that range in size from 450 to 2000 µm and 2.20 g/L (MW) resp. 2.05 g/L (US) for particles that range from 2000 to 4000 µm. PEF has the lowest yield of polyphenols with 0.94 g/L (450–2000 µm), resp. 0.64 g/L (2000–4000 µm) in comparison to 1.82 g/L (2000 to 4000 µm) in a standard stirred vessel (50 °C). When undried red vine leaves (2000 to 4000 µm) are used the total phenol content is 1.44 g/L with PEF.
The fluid dynamic (flow rates) and hydrodynamic behavior (local droplet size distributions and local holdup) of a continuous DN300 pump-mixer were investigated using water as the continuous phase and paraffin oil as the dispersed phase. The influence of the impeller speed (375 to 425 rpm), the feed phase ratio (10 to 30 volume percent), and the total flow rate (0.5 to 2.3 L/min) were investigated by measuring the pumping height, local holdup of the disperse phase, and the droplet size distribution (DSD). The latter one was measured at three different vessel positions using an image-based telecentric shadowgraphic technique. The droplet diameters were extracted from the acquired images using a neural network. The Sauter mean diameters were calculated from the DSD and correlated with an extended model based on Doulah (1975), considering the impeller speed, the feed phase ratio, and additionally the flow rate. The new correlation can describe an extensive database containing 155 experiments of the fluid and hydrodynamic within a 15 % error range
A novel core–shell species for the adsorption-based separation of carbon dioxide (
CO2) from methane (
CH4) is introduced
by hydrothermal synthesis of Ni-MOF-74 on mesoporous spherical Al2O3
carrier substrate. The material was characterized
and the shell thickness determined by means of optical and scanning electron microscopy as well as volumetric
adsorption and fluid displacement experiments. Kinetic experiments with Ni-MOF-74@Al2O3 core–shell composites carried
out at 303.15 K and at pressures up to 10 bar expose remarkably dominating uptake rates for CO2
over CH4.
In the
contrary Ni-MOF-74@Al2O3 appears to be unselective according to equilibrium data at the same conditions. Dynamic
breakthrough experiments of binary CH4/
CO2-mixtures (at 303.15 K and 5 bar) prove the prevailing effect of adsorption
kinetics and the storage function of the mesoporous core. This statement is supported by a considerable boost in
CO2-
selectivity and capacity compared to adsorption equilibria measured on pure Ni-MOF-74 by the factor of 55.02 and
up to 2.42, respectively.
Sorption measurements of water vapor on an isoreticular series of Imidazolate Frameworks
Potsdam (IFP), based on penta-coordinated metal centers with secondary building units (SBUs)
connected by multidentate amido-imidate-imidazolate linkers, have been carried out at 303.15 K. The
isotherm shapes were analyzed in order to gain insight into material properties and compared to
sorption experiments with nitrogen at 77.4 K and carbon dioxide at 273.15 K. Results show that water
vapor sorption measurements are strongly influenced by the pore size distribution while having a
distinct hysteresis loop between the adsorption and desorption branch in common. Thus, IFP-4 and
-8, which solely contain micropores, exhibit H4 (type I) isotherm shapes, while those of IFP-1, -2 and
-5, which also contain mesopores, are of H3 (type IV) shape with three inflection points. The choice
of the used linker substituents and transition metals employed in the framework has a tremendous
effect on the material properties and functionality. The water uptake capacities of the examined IFPs
are ranging 0.48 mmol g????1 (IFP-4) to 6.99 mmol g????1 (IFP-5) and comparable to those documented for
ZIFs. The water vapor stability of IFPs is high, with the exception of IFP-8.
Exploiting Direct Laser Writing for Hydrogel Integration into Fragile Microelectromechanical Systems
(2019)
The integration of chemo-responsive hydrogels into fragile microelectromechanical systems (MEMS) with reflective surfaces in the micron to submicron range is presented. Direct laser writing (DLW) for 3D microstructuring of chemoresponsive “smart” hydrogels on sensitive microstructures is demonstrated and discussed in detail, by production of thin hydrogel layers and discs with a controllable lateral size of 2 to 5 µm and a thickness of some hundred nm. Screening results of polymerizing laser settings for precision microstructuring were determined by controlling crosslinking and limiting active chain diffusion during polymerization with macromers. Macromers are linear polymers with a tunable amount of multifunctional crosslinker moieties, giving access to a broad range of different responsive hydrogels. To demonstrate integration into fragile MEMS, the gel was deposited by DLW onto a resonator with a 200 nm thick sensing plate with high precision. To demonstrate the applicability for sensors, proof of concept measurements were performed. The polymer composition was optimized to produce thin reproducible layers and the feasibility of 3D structures with the same approach is demonstrated.
In this work, steady-state droplet size distributions in a DN300 stirred batch vessel with a
Rushton turbine impeller are investigated using an insertion probe based on the telecentric transmit-
ted light principle. High-resolution droplet size distributions are extracted from the images using
a convolutional neural network for image-analysis in order to investigate the influence of impeller
speed and phase fraction (up to 50 vol.-%). In addition, Sauter mean diameters were calculated and
correlated with two semi-empirical approaches, while the standard approach only accomplished 5.7%
accuracy, and the correlation of Laso et al. provided a relative mean error of 4.0%. In addition, the
correlated exponent in the Weber number was fitted to the experimental data of this work yielding a
slightly different value than the theoretical (−0.6), which allows a better representation of the low
coalescence tendency of the system, which is usually neglected in standard procedures.
A novel shadowgraphic inline probe to measure crystal size distributions (CSD),
based on acquired greyscale images, is evaluated in terms of elevated temperatures and fragile
crystals, and compared to well-established, alternative online and offline measurement techniques,
i.e., sieving analysis and online microscopy. Additionally, the operation limits, with respect to
temperature, supersaturation, suspension, and optical density, are investigated. Two different
substance systems, potassium dihydrogen phosphate (prisms) and thiamine hydrochloride (needles),
are crystallized for this purpose at 25 L scale. Crystal phases of the well-known KH2PO4/H2O system
are measured continuously by the inline probe and in a bypass by the online microscope during
cooling crystallizations. Both measurement techniques show similar results with respect to the crystal
size distribution, except for higher temperatures, where the bypass variant tends to fail due to
blockage. Thiamine hydrochloride, a substance forming long and fragile needles in aqueous solutions,
is solidified with an anti-solvent crystallization with ethanol. The novel inline probe could identify
a new field of application for image-based crystal size distribution measurements, with respect
to difficult particle shapes (needles) and elevated temperatures, which cannot be evaluated with
common techniques.
In this work, we investigate and compare the condensation behavior of hydrophilic, hydrophobic, and biphilic microgrooved silicon samples etched by reactive ion etching. The microgrooves were 25 mm long and 17−19 μm deep with different
topologies depending on the etching process. Anisotropically etched samples had 30 μm wide rectangular microgrooves and silicon ridges between them. They were either left hydrophilic or covered with a hydrophobic fluorocarbon or photoresist layer.
Anisotropically etched samples consisted of 48 μm wide semicircular shaped microgrooves, 12 μm wide silicon ridges between them, and a 30 μm wide photoresist stripe centered on the ridges. The lateral dimensions were chosen to be much smaller than the capillary length of water to support drainage of droplets by coalescence rather than droplet sliding. Furthermore, to achieve a low thermal resistance of the periodic surface structure consisting of water-filled grooves and silicon ridges, the trench depth was also kept small. The dripped-off total amount of condensate (AoC) was measured for each sample for 12 h under the same boundary
conditions (chamber temperature 30 °C, cooling temperature 6 °C, and relative humidity 60%). The maximum increase in AoC of 15.9% (9.6%) against the hydrophilic (hydrophobic) reference sample was obtained for the biphilic samples. In order to elucidate their unique condensation behavior, in situ optical imaging was performed at normal incidence. It shows that the drainage of droplets from the stripe’s surface into the microgrooves as well as occasional droplet sliding events are the dominant processes to clear the surface. To rationalize this behavior, the Hough Circle Transform algorithm was implemented for image processing to receive
additional information about the transient droplet size and number distribution. Postprocessing of these data allows calculation
Modeling of solid-particle effects on bubble breakage and coalescence in slurry bubble columns
(2020)
Solid particles heavily affect the hydrodynamics in slurry bubble columns. The effects arise through varying breakup and coalescence behavior of the bubbles with the presence of solid particles where particles in the micrometer range lead to a promotion of coalescence in particular. To simulate the gas-liquid-solid flow in a slurry bubble column, the Eulerian multifluid approach can be employed to couple computational fluid dynamics (CFD) with the population balance equation (PBE) and thus to account for breakup and coalescence of bubbles.
In this work, three approaches are presented to modify the breakup and coalescence models to account for enhanced coalescence in the coupled CFD-PBE framework. The approaches are applied to a reference simulation case with available experimental data. In addition, the impacts of the modifications on the simulated bubble size distribution (BSD) and the applicability of the approaches are evaluated. The capabilities as well as the differences and limits of the approaches are demonstrated and explained.
In this paper we present the comparison of experiments and numerical simulations for bubble cutting by a wire. The air bubble is surrounded by water. In the experimental setup an air bubble is injected on the bottom of a water column. When the bubble rises and contacts the wire, it is separated into two daughter bubbles. The flow is modeled by the incompressible Navier–Stokes equations. A meshfree method is used to simulate the bubble cutting. We have observed that the experimental and numerical results are in very good agreement. Moreover, we have further presented simulation results for liquid with higher viscosity. In this case the numerical results are close to previously published results.