Avila, Marc
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Avila, Marc
Official Name
Avila, Marc
Alternative Name
Avila, M.
ORCID
GND
6 results
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Item type:Publication, En route towards a comprehensive dimensionless representation of precipitation processesPrecipitation of (nano-) particles is a unit operation for the preparation of suspensions. Despite its widespread use, no general understanding is established of how different operating conditions, such as mixing rates or reactant concentrations, affect the precipitation outcome (e.g. the particle size distribution). We obtain overarching relations between the operating conditions and the precipitation outcome by deriving dimensionless numbers governing the precipitation process. In particular, we consider the interdiffusion of two chemical compounds reacting to a sparingly soluble salt by coupling the reaction–diffusion equations for the solute concentrations, to a population balance equation for the evolution of the dispersed phase including nucleation and growth. We vary the relevant process parameters for different chemical systems and uncover three dimensionless numbers, which fully determine the precipitation outcome under the assumption of fast chemical reactions. Two of these dimensionless numbers are Damköhler numbers, which put the relevant mixing kinetics in relation to the relevant time scales for the nucleation and the growth kinetics, respectively. The third dimensionless number corresponds to a dimensionless solid concentration. Simple functional expressions for the Damköhler numbers valid for any chemical system allow estimating whether the precipitation product is controlled by mixing, or solely by the kinetics of solid formation. In the mixing-controlled regime, scaling laws relate the mean particle sizes and the number of particles to the Damköhler number.journal articleBand:42871 79 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Quantitative modeling of precipitation processes(Elsevier, 2022-09-15); 109 78 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, The MaMBA-concept for an extraterrestrial base and its first module mock-upHabitats must enable astronauts to survive in an extraterrestrial environment, but the challenge is not only a technological one: architecture and engineering should be brought together to create an environment in which a crew can perform optimally. With missions to Mars in mind, crew mental health becomes a design driver equally important to the support of physiological functions. We here suggest a habitat concept, MaMBA (short for Moon and Mars Base Analog), which combines the two requirements. In its basic configuration, MaMBA consists of six upright cylindrical, hard-shell pressure vessels as main modules and two airlocks, which are all connected with inflatable corridor modules. We present the current state of the design and particularly focus on the laboratory module, of which we have constructed a mock-up equipped with scientific instrumentation. In the long-term, we plan to develop this laboratory module into a functional prototype including subsystems such as the life support system. Eventually, we aim to create a habitat which can serve as a test platform (for technologies, operations, and procedures) and whose usability is continually validated through iterative testing with human inhabitants. The habitat is open to international partners for simulations.journal article183 260 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Statistical Analysis of Thermal Conductivity Experimentally Measured in Water-Based Nanofluids(2021-06-16); ; ; ; Nanofluids are suspensions of nanoparticles in a base heat-transfer liquid. They have been widely investigated to boost heat transfer since they were proposed in the 1990's. We present a statistical correlation analysis of experimentally measured thermal conductivity of water-based nanofluids available in the literature. The influences of particle concentration, particle size, temperature and surfactants are investigated. For specific materials (alumina, titania, copper oxide, copper, silica and silicon carbide), separate analyses are performed. The conductivity increases with the concentration in qualitative agreement with Maxwell's theory of homogeneous media. The conductivity also increases with the temperature (in addition to the improvement due to the increased conductivity with water). Surprisingly, only silica nanofluids exhibit a statistically significant effect of particle size, whereby smaller particles lead to faster heat transfer. Overall, the large scatter in the experimental data prevents a compelling, unambiguous assessment of these effects. Taken together, the results of our analysis suggest that more comprehensive experimental characterizations of nanofluids are necessary to estimate their practical potential.journal articleBand:477Heft:2250188 110 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Impact of solvent properties on the precipitation of active pharmaceutical ingredientsIn antisolvent precipitation, water and an organic drug-containing solvent induces particle formation. For each water-solvent mixture, the fluid properties such as viscosity, density and diffusion coefficient but also the drug solubility depend nonlinearily on the fluid mixture compositions. Each property in itself has a strong impact on the solid formation, and thus on the outcome of the precipitation. The simulation framework recently developed by Schikarski et al. [1] allows investigating separately the impact of each fluid property on the precipitation. For a T-mixer and a novel 3-inlet-mixer, we first show that the viscosity and density variations largely determine the macroscopic mixing behavior and, thus, the build-up of supersaturation. The composition-dependent diffusion properties of the drug molecules largely govern the transport-controlled nucleation and particle growth at small scales. In a second step, we numerically predict the experimentally obtained full particle size distribution of the precipitated Ibuprofen nanoparticles using different water-solvent mixtures and different operating conditions. Our numerical results are in excellent agreement with our experimental measurements using ethanol, methanol and 2-propanol as solvents.journal articleBand:41559 62 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Oxygen droplet combustion in hydrogen under microgravity conditions(Elsevier {BV}, 2022); ; ; ; journal article299 145