Quantification of mixing and mixing rate from experimental observations

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 121-127
Author(s):  
R. Everson ◽  
D. Manin ◽  
L. Sirovich ◽  
M. Winter
Keyword(s):  
Mixing Rate

CFD analysis and RSM optimization of obstacle layout in Tesla micromixer

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Xiaowen Wang ◽  
Lihong Yang ◽  
Fujia Sun
Keyword(s):  
Chemical Reaction ◽  
Chemical Engineering ◽  
Design Method ◽  
Mixing Rate ◽  
Special Flow ◽  
Surface Method ◽  
Rsm Optimization ◽  
Effective Technology ◽  
Optimal Design Method ◽  
Lateral Offset

Abstract As a kind of fast and efficient mixing equipment, micromixer has been applied to chemical reaction detection. Its application can not only save experimental samples but also reduce the experimental time. In micromixers, Tesla structure is widely used due to its simple structure and special flow mechanism. In this paper, CFD and response surface method are used to analyze and verify the flow field of the configuration of adding diamond obstacles in the Tesla mixer. The results show that the order of layout parameter weight from large to small is obstacle size > vertical offset > horizontal offset. And the Desirability was 0.806, the optimal diamond obstacle size is 46.35 μm and the optimal lateral offset is 18.78 μm. In addition, a constant value OF 20 μm is predicted as the optimal vertical offset of the micromixer. Compared with the Tesla-type micromixer without obstacles, the diamond-shaped barrier Tesla-type micromixer designed in this paper has higher mixing rate and lower pressure drop under the same conditions, which can be applied to chemical reactors, and can also help to improve the accuracy of chemical reaction. It can be demonstrated that the presented optimal design method of obstacles layout in Tesla mixer is a simple and effective technology to improve the liquid mixing in microfluidic devices, and it has a broad application prospect in chemical engineering.

scholarly journals Numerical study of flame structure in the mild combustion regime

2015 ◽  
Vol 19 (1) ◽  
pp. 21-34 ◽  
Author(s):  
Amir Mardani ◽  
Sadegh Tabejamaat
Keyword(s):  
Fuel Injection ◽  
Numerical Study ◽  
Flame Structure ◽  
Combustion Regime ◽  
Low Oxygen ◽  
Mixing Rate ◽  
Jet Flame ◽  
Reduced Mechanism ◽  
Mild Combustion ◽  
O2 Concentration

In this paper, turbulent non-premixed CH4+H2 jet flame issuing into a hot and diluted co-flow air is studied numerically. This flame is under condition of the moderate or intense low-oxygen dilution (MILD) combustion regime and related to published experimental data. The modelling is carried out using the EDC model to describe turbulence-chemistry interaction. The DRM-22 reduced mechanism and the GRI2.11 full mechanism are used to represent the chemical reactions of H2/methane jet flame. The flame structure for various O2 levels and jet Reynolds numbers are investigated. The results show that the flame entrainment increases by a decrease in O2 concentration at air side or jet Reynolds number. Local extinction is seen in the upstream and close to the fuel injection nozzle at the shear layer. It leads to the higher flame entertainment in MILD regime. The turbulence kinetic energy decay at centre line of jet decreases by an increase in O2 concentration at hot Co-flow. Also, increase in jet Reynolds or O2 level increases the mixing rate and rate of reactions.

Fine Silver Powders Production

2021 ◽  
Vol 410 ◽  
pp. 411-417
Author(s):  
Anastasia A. Zvereva ◽  
Vladimir A. Shunin ◽  
Roman S. Voinkov ◽  
Konstantin L. Timofeev
Keyword(s):  
Silver Powder ◽  
Raw Material ◽  
Solution Temperature ◽  
Production Environment ◽  
Optimum Conditions ◽  
Mixing Rate ◽  
Silver Recovery ◽  
Variable Parameters ◽  
Ph Level ◽  
Tapped Density

The article lays out the findings aimed to develop the fine silver powder production technique for electronics industry by selecting the variable parameters whereby a number of powder grades can be produced in the existing production environment (JSC “Uralelektromed”, Russia). The tests for significance of the parameters of silver recovery by ascorbic acid such as pH level of nitrate silver solution, dispersant flow rate, initial concentration of silver, mixing rate and solution temperature made it possible to choose optimum conditions to produce powders of 0.8-6.3 μm in particle size, of 3.0-4.2 g/cm3 in tapped density and with the specific surface area of 2300-4300 cm2/g. Crystalline silver of 99.98 % purity served as a raw material for obtaining silver powders.

DEVELOPMENT OF CONTINUOUS ANTI-SOLVENT RECRYSTALLIZATION METHOD TO PRODUCE CEFTRIAXONE SODIUM NANO CRYSTALS INJECTION USING CERAMIC FILTRATION

2021 ◽  
Vol 74 (9) ◽  
pp. 2323-2336
Author(s):  
Firas Aziz Rahi ◽  
Krar Kadhim Mj
Keyword(s):  
Particle Size ◽  
Water Purification ◽  
Porous Ceramic ◽  
Ceramic Filter ◽  
Dissolution Time ◽  
Mixing Rate ◽  
Ceftriaxone Sodium ◽  
Continuous Recrystallization ◽  
Ceramic Filtration ◽  
Clear Solution

The aim: In this work we developed a method of continuous recrystallization to meet industrial requirements. Materials and methods: Continuous recrystallization method was investigated using porous ceramic filter for water purification with pour size less than 1 μm, that ensures high mixing rate of ethanol and water. Results and conclusions: The results of experiments using crystallization through ceramic filter, gives superior products in particle size, and produced needle shaped ceftriaxone crystals form, that showed significant improvement in dissolution time and obtained ceftriaxone sodium powder to be reconstituted in injectable formula that give clear solution without insoluble microparticles.

scholarly journals The β-mixing rate of STIT tessellations

Stochastics ◽  
2015 ◽  
Vol 88 (3) ◽  
pp. 396-414 ◽  
Author(s):  
S. Martínez ◽  
W. Nagel
Keyword(s):  
Mixing Rate

scholarly journals A Model Study on the Role of Wetland Zones in Lake Eutrophication and Restoration

2001 ◽  
Vol 1 ◽  
pp. 605-614 ◽  
Author(s):  
J.H. Janse ◽  
W. Ligtvoet ◽  
S. Van Tol ◽  
A.H.M. Bresser
Keyword(s):  
Nutrient Loading ◽  
Predatory Fish ◽  
Nutrient Concentrations ◽  
Fish Stock ◽  
Mixing Rate ◽  
Marsh Vegetation ◽  
Model Calculations ◽  
Critical Loading ◽  
Marsh Area

Shallow lakes respond in different ways to changes in nutrient loading (nitrogen, phosphorus). These lakes may be in two different states: turbid, dominated by phytoplankton, and clear, dominated by submerged macrophytes. Both states are self-stabilizing; a shift from turbid to clear occurs at much lower nutrient loading than a shift in the opposite direction. These critical loading levels vary among lakes and are dependent on morphological, biological, and lake management factors. This paper focuses on the role of wetland zones. Several processes are important: transport and settling of suspended solids, denitrification, nutrient uptake by marsh vegetation (increasing nutrient retention), and improvement of habitat conditions for predatory fish. A conceptual model of a lake with surrounding reed marsh was made, including these relations. The lake-part of this model consists of an existing lake model named PCLake[1]. The relative area of lake and marsh can be varied. Model calculations revealed that nutrient concentrations are lowered by the presence of a marsh area, and that the critical loading level for a shift to clear water is increased. This happens only if the mixing rate of the lake and marsh water is adequate. In general, the relative marsh area should be quite large in order to have a substantial effect. Export of nutrients can be enhanced by harvesting of reed vegetation. Optimal predatory fish stock contributes to water quality improvement, but only if combined with favourable loading and physical conditions. Within limits, the presence of a wetland zone around lakes may thus increase the ability of lakes to cope with nutrients and enhance restoration. Validation of the conclusions in real lakes is recommended, a task hampered by the fact that, in the Netherlands, many wetland zones have disappeared in the past.

scholarly journals Numerical Analysis of the Heterogeneity Effect on Electroosmotic Micromixers Based on the Standard Deviation of Concentration and Mixing Entropy Index

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1055
Author(s):  
Alireza Farahinia ◽  
Jafar Jamaati ◽  
Hamid Niazmand ◽  
Wenjun Zhang
Keyword(s):  
Reynolds Number ◽  
Zeta Potential ◽  
Electroosmotic Flow ◽  
Molecular Diffusion ◽  
Slip Surface ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Slip Coefficient ◽  
Mixing Rate ◽  
Heterogeneous Distribution

One approach to achieve a homogeneous mixture in microfluidic systems in the quickest time and shortest possible length is to employ electroosmotic flow characteristics with heterogeneous surface properties. Mixing using electroosmotic flow inside microchannels with homogeneous walls is done primarily under the influence of molecular diffusion, which is not strong enough to mix the fluids thoroughly. However, surface chemistry technology can help create desired patterns on microchannel walls to generate significant rotational currents and improve mixing efficiency remarkably. This study analyzes the function of a heterogeneous zeta-potential patch located on a microchannel wall in creating mixing inside a microchannel affected by electroosmotic flow and determines the optimal length to achieve the desired mixing rate. The approximate Helmholtz–Smoluchowski model is suggested to reduce computational costs and simplify the solving process. The results show that the heterogeneity length and location of the zeta-potential patch affect the final mixing proficiency. It was also observed that the slip coefficient on the wall has a more significant effect than the Reynolds number change on improving the mixing efficiency of electroosmotic micromixers, benefiting the heterogeneous distribution of zeta-potential. In addition, using a channel with a heterogeneous zeta-potential patch covered by a slip surface did not lead to an adequate mixing in low Reynolds numbers. Therefore, a homogeneous channel without any heterogeneity would be a priority in such a range of Reynolds numbers. However, increasing the Reynolds number and the presence of a slip coefficient on the heterogeneous channel wall enhances the mixing efficiency relative to the homogeneous one. It should be noted, though, that increasing the slip coefficient will make the mixing efficiency decrease sharply in any situation, especially in high Reynolds numbers.

scholarly journals A Hydrodynamical Model for Calculating the Vertical Temperature Profile in Lakes During Cooling

1983 ◽  
Vol 14 (4) ◽  
pp. 239-254 ◽  
Author(s):  
Jörgen Sahlberg
Keyword(s):  
Heat Flux ◽  
Temperature Profile ◽  
Vertical Mixing ◽  
Hydrodynamical Model ◽  
Measured Temperature ◽  
Vertical Temperature ◽  
Mixing Rate ◽  
Mixing Processes ◽  
Vertical Temperature Profile ◽  
Radiation Fluxes

A one-dimensional hydrodynamical model is used for simulating the vertical temperature profile in a lake during cooling conditions. The vertical mixing rate is calculated by solving the equations for turbulent kinetic energy, k, and dissipation of energy, ε. The heat exchange between the water and atmosphere consists of the radiation fluxes, sensible and latent heat flux. Temperature measurements from Lake Väsman during November-December, 1981, were used in the verification study. The agreement between calculated and measured temperature profiles is very good. This indicates that both the mixing processes and the net heat flux are well described in the model.

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