Impeller optimization is essential to improve the performance of stirred tanks, which are widely used in the chemical industry. In this study, a novel channel impeller was developed by eliminating blades from conventi...
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Impeller optimization is essential to improve the performance of stirred tanks, which are widely used in the chemical industry. In this study, a novel channel impeller was developed by eliminating blades from conventional impellers to optimize mixing efficiency. By employing Eulerian-Eulerian model and the standard k-epsilon turbulence model, the hydrodynamic and particle suspension performance of this novel impeller were compared with traditional impellers (pitched blade impeller, propeller, and Rushton). The results reveal that the novel impeller significantly reduces power consumption and power number, while generating a flow pattern characterized by strong radial flows and a complex multi-peak axial velocity profile. Moreover, regions of high turbulent kinetic energy and turbulent energy dissipation rate are more concentrated and symmetrical, thereby improving local mixing efficiency. Notably, the novel impeller achieves a more uniform pressure and stress distribution, offering potentially better fluiddynamics performance and greater durability in practical applications.
An annular reactor is a type of reactor in which chemical reactants move through an annular gap between two concentric cylinders. This type of design is suitable for a variety of chemical processes because it facilita...
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An annular reactor is a type of reactor in which chemical reactants move through an annular gap between two concentric cylinders. This type of design is suitable for a variety of chemical processes because it facilitates efficient heat transfer and mixing of reactants. Previous research has shown that this type of reactor shows promising results in the photocatalytic decomposition of pollutants, which is why it is used in air purification tests. This paper presents a model of one such type of air purification reactor modeled in COMSOL Multiphysics simulation software and provides an overview of the steps that need to be taken in order to effectively model the photocatalytic oxidation. The purpose of modelling the reactor is to test its effectiveness in computer simulations of the decomposition of pollutants in the air using the process of photocatalytic oxidation, which is a combination of photooxidation based on the effect of UV radiation and catalytic oxidation. The resulting simulations allow the scaling of the system (its increase or decrease) so that it can be adapted to certain conditions and used in the real world as a method of air purification at the very sources of polluted air.
This study investigates the hydrothermal liquefaction (HTL) aqueous phase (AP) of Shorea sawdust in a semi-flow batch reactor, focusing on the reaction network and computational fluid dynamics (CFD) simulation. High-p...
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This study investigates the hydrothermal liquefaction (HTL) aqueous phase (AP) of Shorea sawdust in a semi-flow batch reactor, focusing on the reaction network and computational fluid dynamics (CFD) simulation. High-performance liquid chromatography (HPLC) was used to detect lignocellulosic decomposition compounds, revealing the presence of glucose, galactose, xylose, furfural, ethanol, and other undefined compounds due to lignocellulosic decomposition. Reaction ordinate (R0) indicates that the reaction progresses steadily as time increases, and higher temperature leads to a greater reaction ordinate, agreeing with Arrhenius' assumption that gained energy enables molecules to overcome the activation energy barrier. However, saccharide C6 and C5 yield at 220 degrees C fluctuates as the reaction increases, suggesting secondary reactions. A kinetic model was built based on a reaction network, which was developed based on HPLC results. Arrhenius parameters revealed that reaction yield is influenced by temperature and time, whereas galactose, xylose, and ethanol production are time dependent. In contrast, glucose formation is influenced by both time and temperature. The prediction of saccharide yields by the model confirmed that 220 degrees C is the optimal temperature for glucose and ethanol production, balancing slow reactions and rapid degradation. CFD simulations show a uniform pressure distribution inside the reaction chamber with high localised pressure at the input (1570 Pa). In addition, feedstock particles tend to distribute along the chamber wall because of the laminar flow, which is consistent with the observation of the experiment. The findings highlight the intricate relationship between reaction conditions and the composition of the HTL product, contributing to a more comprehensive understanding of the process.
This study employs computational fluid dynamics (CFD) coupled with the population balance model (PBM) to explore the sensitivity of the drag model for the predictive accuracy of the gas-liquid two-phase flow in contin...
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This study employs computational fluid dynamics (CFD) coupled with the population balance model (PBM) to explore the sensitivity of the drag model for the predictive accuracy of the gas-liquid two-phase flow in continuous casting (CC) mold. Several single bubble drag models have been numerically evaluated for high turbulent intensity and gas flow rate operation parameters. Then, the influence of turbulence effect and bubble swarm mechanisms on bubble dynamic behaviors are investigated. The predicted mean bubble diameter and flow pattern were studied and compared with the experimental data. The results show that all single bubble drag models, except for the Grace model, can predict the bubble size distribution (BSD) well. Meanwhile, all models significantly overestimate the bubble diameter near the nozzle under high gas flow rate conditions. A novel drag correction factor based on local gas holdup and BSD is proposed, which takes into account both the hindrance effect of small bubbles and the accelerating effect of large bubbles. The proposed drag correction factor can accurately predict BSD and flow pattern transition in the CC mold under high gas holdup regions. Compared with the simulation results of the previous single bubble drag model, the mean relative error predicted by the novel drag correction factor is decreased by 69.33%.
Mixing non-Newtonian fluids effectively in industrial processes requires optimized impeller designs, with power consumption as key indicators of mixing quality. This study investigated the power consumption and shear ...
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Mixing non-Newtonian fluids effectively in industrial processes requires optimized impeller designs, with power consumption as key indicators of mixing quality. This study investigated the power consumption and shear rate using the Metzner-Otto concept, which is widely used to optimize the mixing process of non-Newtonian fluids. Specifically, in this study, the power consumption and average shear rate with Newtonian and various concentrations of non-Newtonian fluids in tank vessels stirred by single-stage (1S) and double-stage (2S) six-blade paddle impellers were investigated. computational fluid dynamics simulations were performed to analyze power dissipation and shear rates in the stirred tank. The results indicate that local shear rate vary with changes in the shear-thinning behavior of non-Newtonian fluids at constant impeller speed (N). The power dissipation and high-shear fluid volume at the critical shear rate threshold for 2S were two times those of 1S. As the average shear rate is similar, the Metzner-Otto constant (Ks) was also equivalent for both configurations. The findings can be used to characterize the power dissipation and shear distribution in a stirred-tank vessel for non-Newtonian fluids with single-stage and multistage impellers operating in laboratory or industrial plants.
This paper describes the importance of computational fluid dynamics (CFD) as a tool for the design, analysis, and optimization of the different sections of catalytic hydrotreating (HDT) reactors. This paper describes ...
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This paper describes the importance of computational fluid dynamics (CFD) as a tool for the design, analysis, and optimization of the different sections of catalytic hydrotreating (HDT) reactors. This paper describes the genesis and evolution of CFD, its application to the simulation of a HDT reactor, and the mathematical relations that underpin it. It also delineates the formulation and solution of specific problems using CFD. Then, a revision of the selected research papers that have been published to date for the CFD simulation of the HDT process is made. This analysis yielded valuable insights into the utility of CFD for simulating the HDT process. It also identified several bibliographical references that can serve as a comprehensive foundation for those developing CFD simulations in diverse process scenarios.
Cell-laden, scaffold-based tissue engineering methods have been successfully utilized for the treatment of bone fractures and diseases, caused by factors such as trauma, tumors, congenital anomalies, and aging. In suc...
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Cell-laden, scaffold-based tissue engineering methods have been successfully utilized for the treatment of bone fractures and diseases, caused by factors such as trauma, tumors, congenital anomalies, and aging. In such methods, the rate of scaffold biodegradation, transport of nutrients and growth factors, as well as removal of cell metabolic wastes at the site of injury are critical fluid-dynamics factors, affecting cell proliferation and ultimately tissue regeneration. Therefore, there is a critical need to identify the underlying material transport mechanisms and factors associated with cell-seeded, scaffold-based bone tissue engineering. The overarching goal of this study is to contribute to patient-specific, clinical treatment of bone pathology. The overall objective of the work is to establish computational fluid dynamics (CFD) models: (i) to identify the consequential mechanisms behind internal and external material transport through/over porous bone scaffolds designed based on the principles of triply periodic minimal surfaces (TPMS) and (ii) to identify TPMS designs with optimal geometry and flow characteristics for the treatment of bone fractures in clinical practice. In this study, advanced CFD models were established based on ten TPMS scaffold designs for (i) single-unit internal flow analysis, (ii) single-unit external flow analysis, and (iii) cubic, full-scaffold external flow analysis, where the geometry of each design was parametrically created. The influence of several design parameters, such as surface representation iteration, wall thickness, and pore size on geometry accuracy as well as computation time, was investigated in order to obtain computationally efficient and accurate CFD models. The fluid properties (such as density and dynamic viscosity) as well as the boundary conditions (such as no-slip condition, inlet flow velocity, and pressure outlet) of the CFD models were set based on clinical/research values reported in the literature, accord
In this review, the application of computational fluid dynamics (CFD) simulations in analyzing thermal processes within food technology is explored. The focus is on understanding heat transfer, fluid flow, and tempera...
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In this review, the application of computational fluid dynamics (CFD) simulations in analyzing thermal processes within food technology is explored. The focus is on understanding heat transfer, fluid flow, and temperature distribution during various food processing methods, such as baking, frying, pasteurization, and cooling. Detailed insights that are often challenging to obtain through experimental methods alone are provided by CFD simulations, allowing for the optimization of process parameters to enhance product quality and safety. It is demonstrated that CFD can effectively model complex thermal phenomena, providing valuable data on temperature gradients and flow patterns. These simulations assist in the designing of more efficient processing equipment, improving energy consumption, and ensuring uniform heat treatment, which is crucial for maintaining the nutritional and sensory attributes of food products. Furthermore, the integration of CFD in the food industry leads to significant advancements in product development, reducing the time and cost associated with experimental trials. Future research should focus on refining these models for greater accuracy and exploring their application in emerging food processing technologies.
The raceway is the energy source and core reaction region in the blast furnace (BF). This study creates a polyhedral particle based on the BF charge. The effects of particle shape, tuyere velocity, and deadman resista...
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The raceway is the energy source and core reaction region in the blast furnace (BF). This study creates a polyhedral particle based on the BF charge. The effects of particle shape, tuyere velocity, and deadman resistance on the microstructure and mechanical properties of the raceway are analyzed based on the discrete element method-computational fluid dynamics method. The results show that with a velocity of 200 m s-1, the pressure gradient and drag forces of polyhedral particles are 60.94% and 70.06% higher than those of spherical particles, and the height and depth of the raceway are 26.76% and 57.14% of those of spherical particles, respectively. The raceway size is positively proportional to the velocity and inversely proportional to the convective heat transfer rate. The deadman particle diameter and porosity determine the distribution of central and edge gas flow and raceway size, with porosity having a more significant impact on the raceway size. These findings contribute to understanding the dynamics and thermodynamic behavior of irregular particle systems in the raceway.
To address the critical role of atmospheric temperature in climate change and disaster monitoring, enhancing measurement accuracy to 0.1 degrees C is essential. Current instruments are susceptible to radiation interfe...
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To address the critical role of atmospheric temperature in climate change and disaster monitoring, enhancing measurement accuracy to 0.1 degrees C is essential. Current instruments are susceptible to radiation interference, resulting in errors of approximately 1 degrees C. This study introduces a novel temperature sensor that improves accuracy by combining natural ventilation with forced ventilation. Silver-coated aluminum plates (95 % reflectivity) and white-coated deflectors (87 % reflectivity) minimize solar radiation errors. A neural network algorithm, along with CFD simulations, further corrects radiation errors under varying weather conditions. Field tests based on the 076B ventilation device demonstrate that this new sensor reduces the average radiation error to 0.02 degrees C, achieving a RMSE of 0.034 degrees C and a MAE of 0.028 degrees C. The correlation coefficient (r) with the reference temperature reached 0.999, demonstrating the sensor's high precision and providing an effective solution for reducing temperature measurement errors to below 0.1 degrees C. Um die entscheidende Rolle der atmosph & auml;rischen Temperatur im Klimawandel und bei der Katastrophen & uuml;berwachung zu adressieren, ist eine Verbesserung der Messgen & auml;uigkeit auf 0,1 degrees C unerl & auml;sslich. Aktuelle Instrumente sind anf & auml;llig f & uuml;r Strahlungsst & ouml;rungen, was zu Fehlern von etwa 1 degrees C f & uuml;hrt. Diese Studie stellt einen neuartigen Temperatursensor vor, der die Genauigkeit durch die Kombination von nat & uuml;rlicher Bel & uuml;ftung und erzwungener Bel & uuml;ftung verbessert. Silberbeschichtete Aluminiumplatten (95 % Reflektivit & auml;t) und wei ss beschichtete Abweiser (87 % Reflektivit & auml;t) minimieren Strahlungsfehler. Ein neuronales Netzwerk-Algorithmus sowie CFD-Simulationen korrigieren zus & auml;tzlich Strahlungsfehler unter variierenden Wetterbedingungen. Feldtests basierend auf dem 076B Bel & uuml;ftungsger & auml;t zeigen, d
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