Optimización fluidodinámica de un microrreactor para la síntesis de catalizadores FeNiCo-LDH.
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Date
2026
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Universidad de Concepción
Abstract
La síntesis continua de catalizadores FeNiCo-LDH requiere un mezclado rápido y homogéneo, debido a las diferencias entre los productos de solubilidad de los cationes metálicos, las cuales pueden provocar precipitación preferencial, segregación de fases y una distribución no uniforme. En este contexto, la presente memoria tuvo como objetivo optimizar la geometría de un microrreactor de flujo oscilatorio mediante simulaciones de Dinámica de Fluidos Computacional, incorporando obstáculos triangulares en la cámara divergente para intensificar el mezclado sin superar una caída de presión operacional de 45,000 Pa.
Se desarrolló un estudio numérico, comparativo y paramétrico en ANSYS Fluent. Inicialmente, se evaluaron 40 configuraciones geométricas a un número de Reynolds de 400, variando la ubicación longitudinal, la separación respecto de las paredes y el ángulo de los obstáculos. Las geometrías con un índice de mezcla superior al 75 % fueron analizadas posteriormente en el intervalo 100≤𝑅𝑒≤3,200, considerando el índice de mezcla, la caída de presión y una eficiencia basada en el número de Euler. Finalmente, las configuraciones de mejor desempeño fueron comparadas con el diseño base mediante la tasa de deformación, la helicidad y los coeficientes de estiramiento y compresión.
Los resultados mostraron que una separación de 1 mm, un ángulo de 110° y las ubicaciones de 8.95 y 12.925 mm favorecieron la homogeneización. La geometría 12.925_1_110 presentó el mejor desempeño preliminar, con un índice de mezcla de 84.15% a 𝑅𝑒=400. En el análisis posterior, las geometrías 8.95_1_110 y 12.925_1_110 alcanzaron índices de mezcla superiores al 95%, mantuvieron la caída de presión bajo 45,000 Pa hasta un 𝑅𝑒 de 2,400 y conservaron eficiencias cercanas al 41%. En cambio, a 𝑅𝑒=3,200, todas las configuraciones excedieron el límite de presión, por lo que esta condición fue descartada.
El análisis cinemático evidenció que los obstáculos intensificaron los gradientes de velocidad, la interacción entre velocidad y vorticidad, y los procesos de estiramiento y compresión de las estructuras de vórtices. Además, su ubicación determinó la región del microrreactor donde estos mecanismos se desarrollaron con mayor intensidad. Se concluye que las geometrías optimizadas mejoraron significativamente el mezclado y permitieron cumplir simultáneamente los criterios de homogeneización y viabilidad hidráulica, aunque su eficiencia no fue superior a la del diseño original en todas las condiciones. Estos resultados constituyen una base para una futura fabricación, validación experimental y aplicación del microrreactor en la síntesis continua de FeNiCo-LDH.
The continuous synthesis of FeNiCo-LDH catalysts requires rapid and homogeneous mixing due to differences in the solubility products of the metal cations, which can lead to preferential precipitation, phase segregation, and non-uniform composition. In this context, the objective of this thesis was to optimize the geometry of an oscillatory flow micromixer through Computational Fluid Dynamics simulations, incorporating triangular obstacles into the divergent chamber to enhance mixing without exceeding an operational pressure drop of 45,000Pa. A numerical, comparative, and parametric study was conducted using ANSYS Fluent. Initially, 40 geometric configurations were evaluated at a Reynolds number of 400 by varying the longitudinal position, wall clearance, and obstacle angle. Geometries with a mixing index above 75% were subsequently analyzed over the range 100≤𝑅𝑒≤3,200, considering the mixing index, pressure drop, and an efficiency metric based on the Euler number. Finally, the best-performing configurations were compared with the baseline design using the strain rate, helicity, and stretching and compression coefficients. The results showed that a wall clearance of 1mm, an angle of 110°, and obstacle positions of 8.95 and 12.925mm promoted homogenization. The 12.925_1_110 geometry exhibited the best preliminary performance, achieving a mixing index of 84.15% at 𝑅𝑒=400. In the subsequent analysis, the 8.95_1_110 and 12.925_1_110 geometries achieved mixing indices above 95%, maintained the pressure drop below 45,000Pa up to 𝑅𝑒=2,400, and retained efficiencies close to 41%. However, at 𝑅𝑒=3,200, all configurations exceeded the pressure limit, and this operating condition was therefore discarded. The kinematic analysis showed that the obstacles intensified velocity gradients, the interaction between velocity and vorticity, and the stretching and compression processes of vortex structures. Furthermore, their location determined the region of the micromixer where these mechanisms developed most intensely. It is concluded that the optimized geometries significantly improved mixing and simultaneously met the criteria for homogenization and hydraulic feasibility, although their efficiency was not superior to that of the original design under all operating conditions. These results provide a basis for future fabrication, experimental validation, and application of the micromixer in the continuous synthesis of FeNiCo-LDH.
The continuous synthesis of FeNiCo-LDH catalysts requires rapid and homogeneous mixing due to differences in the solubility products of the metal cations, which can lead to preferential precipitation, phase segregation, and non-uniform composition. In this context, the objective of this thesis was to optimize the geometry of an oscillatory flow micromixer through Computational Fluid Dynamics simulations, incorporating triangular obstacles into the divergent chamber to enhance mixing without exceeding an operational pressure drop of 45,000Pa. A numerical, comparative, and parametric study was conducted using ANSYS Fluent. Initially, 40 geometric configurations were evaluated at a Reynolds number of 400 by varying the longitudinal position, wall clearance, and obstacle angle. Geometries with a mixing index above 75% were subsequently analyzed over the range 100≤𝑅𝑒≤3,200, considering the mixing index, pressure drop, and an efficiency metric based on the Euler number. Finally, the best-performing configurations were compared with the baseline design using the strain rate, helicity, and stretching and compression coefficients. The results showed that a wall clearance of 1mm, an angle of 110°, and obstacle positions of 8.95 and 12.925mm promoted homogenization. The 12.925_1_110 geometry exhibited the best preliminary performance, achieving a mixing index of 84.15% at 𝑅𝑒=400. In the subsequent analysis, the 8.95_1_110 and 12.925_1_110 geometries achieved mixing indices above 95%, maintained the pressure drop below 45,000Pa up to 𝑅𝑒=2,400, and retained efficiencies close to 41%. However, at 𝑅𝑒=3,200, all configurations exceeded the pressure limit, and this operating condition was therefore discarded. The kinematic analysis showed that the obstacles intensified velocity gradients, the interaction between velocity and vorticity, and the stretching and compression processes of vortex structures. Furthermore, their location determined the region of the micromixer where these mechanisms developed most intensely. It is concluded that the optimized geometries significantly improved mixing and simultaneously met the criteria for homogenization and hydraulic feasibility, although their efficiency was not superior to that of the original design under all operating conditions. These results provide a basis for future fabrication, experimental validation, and application of the micromixer in the continuous synthesis of FeNiCo-LDH.
Description
Tesis presentada para optar al título de Ingeniero/a Civil Aeroespacial.
Keywords
Catalizadores, Dinámica de fluidos computacional, Microrreactores