scholarly journals CFD Modeling to Predict Mass Transfer in Multicomponent Mixtures

2019 ◽  
Vol 14 (4) ◽  
Author(s):  
Mitra Sadat Lavasani ◽  
Rahbar Rahimi ◽  
Mortaza Zivdar ◽  
Mohammad Kalbassi
Keyword(s):  
Mass Transfer ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Ternary Mixtures ◽  
Cfd Modeling ◽  
Multicomponent Mixtures ◽  
Distillation Columns ◽  
Multicomponent Distillation ◽  
Interactive Nature ◽  
Two Phases

Abstract A novel three-dimensional computational fluid dynamics mass transfer (CMT) model in Eulerian–Eulerian frame work is deploys for investigating the concentration profiles, and trays efficiencies in multicomponent distillation columns. The proposed model is based on Maxwell Stefan equations, and CFD was employed as a powerful tool to model the hydrodynamics and mass transfer. The two phases are modelled as two interpenetrating phases with interphase momentum, heat and mass transfer. The Closure model is developed for mass interphase transfer rate in ternary mixtures. The predictability of the mass transfer behaviours of multicomponent can result in a more efficient and predictable design of distillation trays. Two non-ideal ternary mixtures were studied. The tray geometry and operating conditions are based on the experimental works of Kalbassi and the composition profiles, tray efficiencies, and point efficiencies of mixtures were presented. The obtained results were confirmed by the experimental data. The results indicate that the values of individual component tray efficiencies and point efficiencies for these multicomponent systems were considerably different which confirm the interactive nature of the mass transfer in multicomponent mixtures. These mixtures also illustrated different point efficiencies across the tray because of the composition dependency of these mixtures. The average relative error for the prediction of efficiencies is about 8 %, which indicates the accuracy of the model.

CFD Modeling of Mass-Transfer Processes in Randomly Packed Distillation Columns

2000 ◽  
Vol 39 (5) ◽  
pp. 1369-1380 ◽  
Author(s):  
F. H. Yin ◽  
C. G. Sun ◽  
A. Afacan ◽  
K. Nandakumar ◽  
K. T. Chuang
Keyword(s):  
Mass Transfer ◽  
Cfd Modeling ◽  
Distillation Columns ◽  
Transfer Processes ◽  
Mass Transfer Processes

On Entropy Generation and the Effect of Heat and Mass Transfer Coupling in a Distillation Process

2018 ◽  
Vol 43 (1) ◽  
pp. 57-74
Author(s):  
Paulina Burgos-Madrigal ◽  
Diego F. Mendoza ◽  
Mariano López de Haro
Keyword(s):  
Mass Transfer ◽  
Entropy Production ◽  
Heat And Mass Transfer ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Entropy Production Rate ◽  
Distillation Columns ◽  
First Case ◽  
Three Stages ◽  
Cold Liquid

AbstractThe entropy production rates as obtained from the exergy analysis, entropy balance and the nonequilibrium thermodynamics approach are compared for two distillation columns. The first case is a depropanizer column involving a mixture of ethane, propane, n-butane and n-pentane. The other is a weighed sample of Mexican crude oil distilled with a pilot scale fractionating column. The composition, temperature and flow profiles, for a given duty and operating conditions in each column, are obtained with the Aspen Plus V8.4 software by using the RateFrac model with a rate-based nonequilibrium column. For the depropanizer column the highest entropy production rate is found in the central trays where most of the mass transfer occurs, while in the second column the highest values correspond to the first three stages (where the vapor mixture is in contact with the cold liquid reflux), and to the last three stages (where the highest temperatures take place). The importance of the explicit inclusion of thermal diffusion in these processes is evaluated. In the depropanizer column, the effect of the coupling between heat and mass transfer is found to be negligible, while for the fractionating column it becomes appreciable.

Use of CFD Modeling for Designing Intake and Discharge Structures in a Discharge Canal

2010 ◽  
Author(s):  
Fangbiao Lin ◽  
George Pigg ◽  
Gerald Schohl
Keyword(s):  
Power Plants ◽  
Cooling Tower ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
The North ◽  
Cfd Models ◽  
Discharge Canal ◽  
Before And After ◽  
Pros And Cons

This paper presents a computational fluid dynamics (CFD) modeling approach for designing intake and discharge structures in a discharge canal for nuclear and fossil power plants. It discusses how the CFD models are developed, what types of results can be obtained from the CFD modeling study and how the results are used for developing designs of the intake and discharge structures. The pros and cons of the CFD modeling method for this type of application are also discussed. Intake and discharge structures for a “Helper Cooling Tower South” will be added to the discharge canal of the Crystal River Energy Complex (CREC). The CFD modeling was used to confirm suitable locations for the new intake and discharge structures to minimize potential recirculation and potential loss of cooling tower efficiency, and to evaluate the erosion of the banks on the north and south side of the canal due to the flow from the discharge structure. The CFD model was developed using FLUENT for the existing and future configurations of the discharge canal that consists of the existing intake, discharges, and the new intake and discharge structures. The CFD modeling runs were performed to investigate three-dimensional flow patterns, velocities and temperatures in the discharge canal under current and future operating conditions. Current and future conditions refer to those before and after installation of the Helper Cooling Tower South Intake and Discharge structures, respectively. Comparing the CFD results (streamlines, temperature and velocity distributions, etc.) for the future conditions to those for the existing conditions, the locations and designs of the new intake and discharge structures were assessed and developed. This study demonstrates that the new intake is not impacted by the new and existing discharge structures, and the existing intake will perform similarly as it performs before the construction of the new intake and discharges. The study also identifies some sections of the canal banks and bottom that may need to be protected from erosion due to the impacts of the high velocity water from the discharge structures.

A Comparative Study of a Morphing Wing

2017 ◽  
Author(s):  
Eun Jung Chae ◽  
Amin Moosavian ◽  
Alexander M. Pankonien ◽  
Daniel J. Inman
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Superior Performance ◽  
Cfd Modeling ◽  
Navier Stokes ◽  
Morphing Wing ◽  
Trailing Edge ◽  
Analytical Approaches

Along with recent advancements in novel materials and manufacturing processes, the interest in morphing wings has increased in order to further improve the aerodynamic performance of flying bodies. The morphing wing can be tailored to deliver superior performance, compared to its non-morphing counterparts, for multiple operating conditions and in varying flows. In particular, the morphing wing is implemented for drag reduction and lift enhancement, and hence, the maneuverability, adaptability, and capability of the morphing wing can encompass an even wider spectrum by changing the wing shape. In this research, an existing morphing UAV wing design, Spanwise Morphing Trailing Edge (SMTE), actuated by bending Macro Fiber Composites (MFCs), is considered to generate the spanwise sinusoidal variations on the trailing edge of the morphing wing. A comparative aerodynamic study of the morphing wing by varying the spatial frequency (i.e., number of waves along the span) and the phase shift (i.e., wave shape along the span) at different angles of attack is conducted through analytical approaches and numerical Computational Fluid Dynamic (CFD) simulations, which are validated with previous experimental measurements. The analytical approach uses the three-dimensional (3D) Prandtl lifting line theory, and the CFD modeling in turbulence flow solves the 3D Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ω Shear Stress Transport (SST) turbulence model. Note that the numerical simulations of a morphing wing focus on the pre-stall condition to estimate the aerodynamic performance. This work extends a prior study about a nominal flight condition testing a morphing wing at multiple flight conditions to evaluate multi-point 1 performance. The results show that there are governing aerodynamic efficiency zones of the lift-to-drag ratio, endurance, and aircraft range within a zone of angles of attack. Therefore, the morphing wing is shown to have a good aerodynamic performance as compared to the non-morphing wing.

scholarly journals Multi-Dimensional Modeling of the CFR Engine for the Investigation of SI Natural Gas Combustion and Controlled End-Gas Autoignition

2020 ◽  
Author(s):  
Diego Bestel ◽  
Scott Bayliff ◽  
Anthony Marchese ◽  
Daniel Olsen ◽  
Bret Windom ◽  
...  
Keyword(s):  
Natural Gas ◽  
Chemical Reactivity ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
General Tendency ◽  
Natural Gas Engines ◽  
Advantages And Disadvantages ◽  
Crank Angle ◽  
Wide Range

Abstract Engine knock and misfire are barriers to pathways leading to high-efficiency Spark-Ignited (SI) Natural Gas engines. The general tendency to knock is highly dependent on engine operating conditions and the fuel reactivity. The problem is further complicated by low emission limits and the wide range of chemical reactivity in pipeline quality natural gas. Depending on the region and the source of the natural gas, its reactivity, described by its methane number (analogous to the octane number for liquid SI fuels) can span from 65–95. In order to realize diesel-like efficiencies, SI natural gas engines must be designed to operate at high BMEP near knock limits over a wide range of fuel reactivity. This requires a deep understanding regarding the combustion-engine interactions pertaining to flame propagation and end-gas autoignition (EGAI). However, EGAI, if controlled, provides an opportunity to increase SI natural gas engine efficiency by increasing combustion rate and the total burned fuel, mitigating the effects of the slow flame speeds of natural gas fuels which generally reduce BMEP and increase unburned hydrocarbon emissions. For this reason, in order to study EGAI phenomenon, the present work highlights multi-dimensional computational fluid dynamics (CFD) models of the Cooperative Fuel Research (CFR) engine. The CFR engine models are used to investigate fuel-engine interactions that lead to EGAI with natural gas, including effects of fuel reactivity, engine operating parameters, and exhaust gas recirculation (EGR). A Three-Pressure Analysis, performed with GT-Power, was used to estimate initial and boundary conditions for the three-dimensional CFD model. CONVERGE CFD v2.4 was used for the three-dimensional CFD modeling where the level set G-Equation model and SAGE detailed chemical kinetics solver were used. An assessment of the different modeling approaches is also provided to evaluate their limitations, advantages and disadvantages, and for which situations they are most applicable. Model validation was performed with experimental data taken with a CFR engine over varying compression ratio, CA50, EGR fraction, and IMEP and shows good agreement in Peak Cylinder Pressure (PCP), PCP crank angle, and the location of the 10%, 50%, and 90% mass fraction burned (CA10, CA50, and CA90, respectively). The models can predict the onset crank angle and pressure rise rate for light, medium, and heavy EGAI under a variety of fuel reactivities and engine operating conditions.

Heat and Mass Transfer Evaluation in the Channels of an Automotive Catalytic Converter by Detailed Fluid-Dynamic and Chemical Simulation

2006 ◽  
Vol 129 (4) ◽  
pp. 536-547 ◽  
Author(s):  
Cinzio Arrighetti ◽  
Stefano Cordiner ◽  
Vincenzo Mulone
Keyword(s):  
Mass Transfer ◽  
Surface Chemistry ◽  
Heat And Mass Transfer ◽  
Ad Hoc ◽  
Catalytic Converter ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Local Heat ◽  
Operating Conditions ◽  
Spark Ignition Engines

The role of numerical simulation to drive the catalytic converter development becomes more important as more efficient spark ignition engines after-treatment devices are required. The use of simplified approaches using rather simple correlations for heat and mass transfer in a channel has been widely used to obtain computational simplicity and sufficient accuracy. However, these approaches always require specific experimental tuning so reducing their predictive capabilities. The feasibility of a computational fluid dynamics three-dimensional (3D) model coupled to a surface chemistry solver is evaluated in this paper as a tool to increase model predictivity then allowing the detailed study of the performance of a catalytic converter under widely varying operating conditions. The model is based on FLUENT to solve the steady-state 3D transport of mass, momentum and energy for a gas mixture channel flow, and it is coupled to a powerful surface chemistry tool (CANTERA). Checked with respect to literature available experimental data, this approach has proved its predictive capabilities not requiring an ad hoc tuning of the parameter set. Heat and mass transfer characteristics of channels with different section shapes (sinusoidal, hexagonal, and squared) have then been analyzed. Results mainly indicate that a significant influence of operating temperature can be observed on Nusselt and Sherwood profiles and that traditional correlations, as well as the use of heat/mass transfer analogy, may give remarkable errors (up to 30% along one-third of the whole channel during light-off conditions) in the evaluation of the converter performance. The proposed approach represents an appropriate tool to generate local heat and mass transfer correlations for less accurate, but more comprehensive, 1D models, either directly during the calculation or off-line, to build a proper data base.

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