			Home About us Contact

Process Simulation (process + simulation)

Distribution by Scientific Domains

Chemistry	43%
Polymers and Materials Science	26%
Engineering	8%

Selected Abstracts

Process simulation of p -doping in GaN and related group III nitrides

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2007
Y. J. Zhou
Abstract In this work we use the PROCOM sofware to model Mg doped GaN film growth by MOCVD. The 2/3D conservation equations of mass, energy, momentum and species are solved by the nonsymmetric conjugate gradient method with block preconditioning (H. C. Elman, Preconditioned conjugate gradient methods for nonsymmetric systems of linear equations (Yale University Research Report, 1981) [5]). A kinetics model with gas/surface adduct formation has been incorporated with detailed Mg dopant reaction mechanism. We reproduced broad doping profiles caused by memory effects and verified that the formation of (NH3)2 -MgCp2 and NH3 -MgCp2 adducts play an important role in p-doping of GaN and related Group III nitrides. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Novel pervaporation technology using absorption refrigeration for vapor removal

AICHE JOURNAL, Issue 11 2002
Alaa Fahmy
A novel process configuration for pervaporation and vapor permeation realizes the permeation driving force by absorbing the permeate vapor into a suitable solution with a very low vapor pressure. Although the suggested process design lacks an experimental demonstration, by using two well-established technologies,the separation by pervaporation and the absorption refrigeration,it can achieve technical and economic advantages over the conventional condensation technology. Vacuum pressures as low as 8 mbar can be obtained at ambient temperatures without refrigeration, as well as low vacuum ranges that are not possible by condensation without freezing. Process simulations and feasibility investigations for the suggested process are discussed. [source]

Performance comparison of checkpoint and recovery protocols

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 15 2003
Himadri Sekhar Paul
Abstract Checkpoint and rollback recovery is a well-known technique for providing fault tolerance to long-running distributed applications. Performance of a checkpoint and recovery protocol depends on the characteristics of the application and the system on which it runs. However, given an application and system environment, there is no easy way to identify which checkpoint and recovery protocol will be most suitable for it. Conventional approaches require implementing the application with all the protocols under consideration, running them on the desired system, and comparing their performances. This process can be very tedious and time consuming. This paper first presents the design and implementation of a simulation environment, distributed process simulation or dPSIM, which enables easy implementation and evaluation of checkpoint and recovery protocols. The tool enables the protocols to be simulated under a wide variety of application, system, and network characteristics. The paper then presents performance evaluation of five checkpoint and recovery protocols. These protocols are implemented and executed in dPSIM under different simulated application, system, and network characteristics. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Modeling the Porosity Formation in Austenitic SGI Castings by Using a Physics-Based Material Model,

ADVANCED ENGINEERING MATERIALS, Issue 3 2010
B. Pustal
Abstract On solidification, microsegregations build up in solid phases due to changes in solid concentrations with temperature. Diffusion, which is a kinetic process, usually reduces the occurrence of microsegregations. This work is aimed at modeling such kinetic effects on the solidification of austenitic cast iron, using a holistic approach. For this purpose, a microsegregation model is developed and validated. Moreover, this model is directly coupled to a commercial process-simulation tool and thermodynamic software. A series of GJSA-XNiCr 20-2 clamp-rings is cast by varying the inoculation state and the number of feeders. The composition of this cast alloy is analyzed and the microstructure characterized to provide input data for the microsegregation model. In order to validate the software, cooling curves are recorded; differential thermal analysis, electron dispersive X-ray analysis and electron probe micro analysis are carried out. Furthermore, the porosity within the casting is analyzed by X-ray. By performing coupled simulations, the different cooling characteristics within the casting lead to pronounced differences in phase fractions and solidification temperatures which are due to dendrite arm coarsening. The hot spot effect below the feeders is assisted by a shift towards lower solidification temperatures over the solidification time. This shift is a result of the local cooling characteristics, which can only be predicted when process simulation is directly coupled with material simulation. The porosity predictions and the porosity analysis exhibit good agreement. A comparison between experimental and virtual cooling curves closes, implying that the novel coupling concept and its implementation are valid. [source]

Thermo-Economic Modelling and Optimisation of Fuel Cell Systems,

FUEL CELLS, Issue 1 2005
F. Marechal
Abstract This paper describes and illustrates the application of a methodology for thermo-economic design and optimisation of fuel cell systems. This methodology combines the use of process simulation and process integration techniques to compute thermo-economic performances of fuel cell systems that will be used in a multi-objective optimisation framework. The method allows the generation of integrated fuel cell system configurations and their corresponding optimal operating conditions. It should be used as a preliminary design methodology, allowing the identification of promising system configurations, which would be further analysed. The methodology and the thermo-economic models are described and demonstrated for the design of PEMFC hybrid systems, combining fuel cell and gas turbine technologies. [source]

SMB chromatography design using profile advancement factors, miniplant data, and rate-based process simulation

AICHE JOURNAL, Issue 11 2009
Shawn D. Feist
Abstract This article describes a systematic miniplant-based approach to rapid development of simulated moving bed (SMB) chromatography applications. The methodology involves analysis of single-column pulse tests to screen adsorbents and operating conditions and to determine initial values of profile advancement factors used to specify flow rates for an initial SMB miniplant experiment. A lumped-parameter linear driving force rate-based model is developed by fitting process data from a single miniplant run. The data are fit in a two-step procedure involving initial determination of effective adsorption isotherm constants as best-fit parameters with subsequent adjustment of calculated mass transfer coefficients to refine the data fit. The resulting simulation is used to guide further miniplant work and minimize experimental effort. The methodology is illustrated with miniplant data for a binary protein separation showing excellent agreement between model results and process data generated over a wide range of operating conditions. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Computer aided design for sustainable industrial processes: Specific tools and applications

AICHE JOURNAL, Issue 4 2009
Maurizio Fermeglia
Abstract Chemical Process Sustainability can be estimated using different sustainability indicators. The quantitative estimation of those indicators is necessary (i) for evaluating the environmental impact of a chemical process and (ii) for choosing the best design among different available alternatives. To accomplish these goals, the computerized calculation of sustainability indicators requires the use of at least three computer tools: (i) process simulation, (ii) molecular modeling and a (iii) sustainability indicators software code. In this work, a complete software platform, Process Sustainability Prediction Framework, integrated with process simulation programs, which support the CAPE-OPEN interfaces, is presented and discussed. The article contains also description and application of molecular modeling techniques to estimate different toxicological data, which are used in the calculation of sustainability indicators. A representative example of one chemical process and thermo-physical properties used in the toxicological data calculation, are reported to demonstrate the applicability of the software to real cases. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Application of CAMD in separating hydrocarbons by extractive distillation

AICHE JOURNAL, Issue 12 2005
Biaohua Chen
Abstract The solvent is the core of extractive distillation, and a suitable solvent plays an important role in the economical design of extractive distillation. Computer-aided molecular design (CAMD) has been applied to rapidly screen the solvents for separating hydrocarbons by extractive distillation. The systems of propane/propylene, n-butane/1-butene, and n-heptane/benzene, respectively, as the representatives of C3, C4, and C6 hydrocarbons were investigated, and the potential solvents were selected by means of CAMD. The designed results were further proven by experiments and process simulation. The mechanism for separating hydrocarbons by extractive distillation is based on the different fluidities of the electron cloud of CC (no double bond), CC (one double bond), and ACH (aromatic carbon ring) bonds and thus different interactions between solvent and hydrocarbon molecules. To improve the separation ability of the main solvent, one strategy is to add some additive that can form hydrogen bonding with the main solvent to make into a mixture. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source]

New approach to refinery process simulation with adaptive composition representation

AICHE JOURNAL, Issue 3 2004
Heiko Briesen
Abstract The established technique for simulation of refinery processes is the use of pseudocomponents. However, in order to increase the economical benefit of plant operation, it seems inevitable to include molecular information in petroleum mixtures characterization. This will lead to a strong increase of problem size. For this new class of models, there currently seems to be no special algorithms available. The classic pseudocomponent approach is compared with a newly developed solution strategy, which is explicitly developed to efficiently solve simulation problems with a high detail in composition representation. The new solution strategy is an adaptive multigrid method based on a wavelet,Galerkin discretization. With the wavelet,Galerkin discretization the model can easily be formulated on various levels of detail. In an iterative procedure the multigrid concept exploits these different formulations to construct correction-term approximations to the true solution. The discretization of these correction-term models is now done with a detail in composition representation that is determined by a residual-based adaptation strategy. The proposed method has been implemented for a simple 9-stage distillation column and tested for a variety of feed mixtures. In all investigated tests the proposed method proved to be superior to the conventional pseudocomponent approach in terms of accuracy and efficiency. © 2004 American Institute of Chemical Engineers AIChE J, 50: 633,645, 2004 [source]

Prediction of phase equilibria for binary mixtures by molecular modeling

AICHE JOURNAL, Issue 10 2001
Maurizio Fermeglia
Two new procedures based on quantum/COSMO calculations and on molecular mechanics/dynamics simulations, respectively, for estimating the PHSCT EOS parameters and to predict VLE behavior for binary mixtures are presented. The quality of the predictions achieved with both methods, in conjunction with the confined computational time aspects involved, can be considered satisfactory so that these strategies can be judged as promising routes toward an on-line coupling between molecular and process simulation. [source]

Paths to deutero-learning through successive process simulations: a case study

KNOWLEDGE AND PROCESS MANAGEMENT: THE JOURNAL OF CORPORATE TRANSFORMATION, Issue 4 2004
Päivi Haho
This paper discusses the dynamic interaction between organizational learning processes and their outcomes in the context of innovative business process development and change projects in a pharmaceutical company. Through the answers to the research questions, I wish to demonstrate the paths to deutero-learning, which seldom can be empirically identified in an organization. The paper uses notions of strategic, operational and cultural outcomes,including their intangible and tangible manifestations,to explain different results in organizational learning processes. From 1998 to 1999, the pharmaceutical case company applied an evolutionary, process simulation-based business process development method. This method was used to invent and implement business process innovations in the New Product Development process, to shorten the time-to-market of its new medical entities. Successive process simulations guided and focused the business process development and actions on the strategically most valuable areas. The process simulations prepared the organization for the change, and promoted the implementation of the process outcomes. The successive simulations have triggered and thereafter sustained individual and organizational learning. Thus, they have accelerated organizational learning processes and the development of knowledge and innovations. The case demonstrates efficient deutero-learning, enabled through empowered successive process simulations. The results indicate that development projects are more successful, if there are intangible learning outcomes and systemic process learning at the early stages of the project. This also supports double-loop learning in the business process development project and assists changes in norms to occur. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Flow modeling and simulation for vacuum assisted resin transfer molding process with the equivalent permeability method

POLYMER COMPOSITES, Issue 2 2004
Renliang Chen
Vacuum assisted resin transfer molding (VARTM) offers numerous advantages over traditional resin transfer molding, such as lower tooling costs, shorter mold filling time and better scalability for large structures. In the VARTM process, complete filling of the mold with adequate wet-out of the fibrous preform has a critical impact on the process efficiency and product quality. Simulation is a powerful tool for understanding the resin flow in the VARTM process. However, conventional three-dimensional Control Volume/Finite Element Method (CV/FEM) based simulation models often require extensive computations, and their application to process modeling of large part fabrication is limited. This paper introduces a new approach to model the flow in the VARTM process based on the concept of equivalent permeability to significantly reduce computation time for VARTM flow simulation of large parts. The equivalent permeability model of high permeable medium (HPM) proposed in the study can significantly increase convergence efficiency of simulation by properly adjusting the aspect ratio of HPM elements. The equivalent permeability model of flow channel can simplify the computational model of the CV/FEM simulation for VARTM processes. This new modeling technique was validated by the results from conventional 3D computational methods and experiments. The model was further validated with a case study of an automobile hood component fabrication. The flow simulation results of the equivalent permeability models were in agreement with those from experiments. The results indicate that the computational time required by this new approach was greatly reduced compared to that by the conventional 3D CV/FEM simulation model, while maintaining the accuracy, of filling time and flow pattern. This approach makes the flow simulation of large VARTM parts with 3D CV/FEM method computationally feasible and may help broaden the application base of the process simulation. Polym. Compos. 25:146,164, 2004. © 2004 Society of Plastics Engineers. [source]

Microwave and conventional curing of thick-section thermoset composite laminates: Experiment and simulation

POLYMER COMPOSITES, Issue 2 2001
Erik T. Thostenson
In conventional processing, thermal gradients cause differential curing of thick laminates and undesirable outside-in solidification. To reduce thermal gradients, thick laminates are processed at lower cure temperatures and heated with slow heating rates, resulting in excessive cure times. Microwaves can transmit energy volumetrically and instantaneously through direct interaction of materials with applied electromagnetic fields. The more efficient energy transfer of microwaves can alleviate the problems associated with differential curing, and the preferred inside-out solidification can be obtained. In this work, both microwave curing and thermal curing of 24.5 mm (1 inch) thick-section glass/epoxy laminates are investigated through the development of a numerical process simulation and conducting experiments in processing thick laminates in a conventional autoclave and a microwave furnace. Outside-in curing of the autoclave-processed laminate resulted in visible matrix cracks, while cracks were not visible in the microwave-processed laminate. Both numerical and experimental results show that volumetric heating due to microwaves promotes an inside-out cure and can dramatically reduce the overall processing time. [source]

Rotational molding cycle time reduction through surface enhanced molds: Part A,Theoretical study

POLYMER ENGINEERING & SCIENCE, Issue 9 2007
M.Z. Abdullah
Rotational molding has been regarded as a plastic molding method with great potential. The process offers virtually stress-free products having no weld lines or material wastage, and utilizes relatively inexpensive molds. Yet its widespread growth is hindered due to long production cycle times, which are limited by the time required to heat up and cool down the mold and the product. To address this issue, efforts have been made to enhance heat transfer to and from molds, ultimately reducing cycle times. The application of extended and rough surfaces to molds is investigated here. The aim of this study is to predict reductions in cycle time due to the enhancement of mold surfaces (i.e. roughness-enhanced and pin-enhanced molds). By utilizing a combination of heat transfer correlations, numerical analysis, and an existing rotational molding process simulation, cycle time predictions were made. The average predicted cycle time reductions were ,21 and 32% for the roughness-enhanced and pin-enhanced molds considered, under a variety of conditions. POLYM. ENG. SCI., 47:1406,1419, 2007. © 2007 Society of Plastics Engineers [source]

Analysis of laser/IR-assisted microembossing

POLYMER ENGINEERING & SCIENCE, Issue 5 2005
Chunmeng Lu
To shorten the cycle time in conventional hot embossing, an infrared laser (laser/IR)-assisted microembossing process was investigated in this study. Since the laser/IR heats the substrate rapidly and locally, the heating and cooling time can be substantially reduced. Two different modes of IR embossing were tested. In one case, the polymer substrate was the IR-transparent poly(methyl methacrylate) (PMMA) and a carbon black-filled epoxy mold was used. In the second case, the polymer substrate was an IR-absorbent PMMA, and an IR transparent epoxy mold was used. The experimental results showed that both a shorter cycle time and good replication accuracy could be achieved. A commercially available finite element (FEM) code, DEFORMÔ, was used for process simulation. The relationship between the penetration of radiation energy flux from the laser/IR heating source and temperature distribution inside the polymer substrate was considered in the simulation. The flow pattern observed in the experiments agreed well with the numerical simulation. However, the displacement curve showed a discrepancy. POLYM. ENG. SCI., 45:661,668, 2005. © 2005 Society of Plastics Engineers [source]

A physical-mathematical model for the dispersion process in continuous mixers

POLYMER ENGINEERING & SCIENCE, Issue 1 2002
H. Potente
To modify the properties of polymers, mineral fillers are frequently added during the compounding process. Because of adhesive forces, these pulverized fillers tend to agglomerate. Therefore, in order to achieve good homogenization, it is essential not only to distribute them but also to break down the solid agglomerates. A number of relating models have been published, describing observations (agglomerate rupture, erosion, clustering) made during the dispersion process in a mostly isolated manner. New models for each observed effect have been developed and later superimposed in order to get a comprehensive model of the dispersion process. To verify the model, it was implemented into a program for the process simulation of co-rotating twin-screw extruders. It was then compared to experimental data. The results showed that the model is able to describe the experimentally determined data. [source]

Effects of physical properties estimation on process design: a case study using AspenPlus

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009
Loic Cadoret
Abstract This study focuses on the physical property model parameters estimation in order to accurately simulate separation processes for a given set of components. The non-random two-liquid (NRTL) model was chosen and parameters were calculated using different methods: experimental data regression and UNIFAC and COSMO-SAC (conductor-like screening model, segment activity coefficient) predictive models. The vapor-liquid equilibrium (VLE) obtained from these different models was compared and results showed that COSMO-SAC can be a reliable tool when data or functional groups are missing. Results also showed that the use of UNIFAC to estimate activity coefficients at infinite dilution can, in some cases, leads to inaccurate results and strongly impact process simulation results. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

An exergy calculator tool for process simulation

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2007
Juan M. Montelongo-Luna
Abstract The constant tightening of environmental regulations and the ongoing need to reduce operating costs have posed a challenge for the design of any chemical process. Process engineers use process simulators to help them perform calculations that will, ultimately, result in design parameters or operating conditions for a plant or process. Exergy is a potential indicator that can aid in the design of energy efficient chemical processes and plants. The exergy concept has been increasingly used as a tool to locate the critical energy use in many industrial processes, both chemical and non-chemical. However, currently most process simulators in the market do not offer the capability of calculating the exergy of a process. An open-source exergy calculator has been created by embedding the calculation procedure in an open-source chemical process simulator. This improves process simulation by including a potential tool for design teams to quickly evaluate several process options in detail in order to understand their energy utilisation. A simple exergy analysis for a gas processing facility is used to demonstrate the capabilities of the tool. The analysis shows where the largest quantities of exergy are being consumed within the plant, thus pointing to areas where improvement in energy usage can be made. The use of exergy as a potential design and retrofit tool is also discussed. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

An integrated, finite element-based process model for the analysis of flow, heat transfer, and solidification in a continuous slab caster

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2003
C. H. Moon
Abstract An integrated, finite element-based process model is presented for the prediction of full three-dimensional flow, heat transfer, and solidification occurring in a continuous caster. Described in detail are the basic models for the analysis of turbulent flow and heat transfer in the liquid steel zone, in the zone of mixture of the liquid steel and solidified steel, and in the solidified zone. Then, the models are integrated to form a process model which can take into account the strong interdependence between the heat transfer behaviour and the flow behaviour. The capability of the process model to reveal the detailed aspects of turbulent flow, heat transfer, and solidification occurring in a continuous caster is demonstrated through a series of process simulations. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Paths to deutero-learning through successive process simulations: a case study

Understanding hydrological processes with scarce data in a mountain environment

HYDROLOGICAL PROCESSES, Issue 12 2008
A. Chaponnière
Abstract Performance of process-based hydrological models is usually assessed through comparison between simulated and measured streamflow. Although necessary, this analysis is not sufficient to estimate the quality and realism of the modelling since streamflow integrates all processes of the water cycle, including intermediate production or redistribution processes such as snowmelt or groundwater flow. Assessing the performance of hydrological models in simulating accurately intermediate processes is often difficult and requires heavy experimental investments. In this study, conceptual hydrological modelling (using SWAT) of a semi-arid mountainous watershed in the High Atlas in Morocco is attempted. Our objective is to analyse whether good intermediate processes simulation is reached when global-satisfying streamflow simulation is possible. First, parameters presenting intercorrelation issues are identified: from the soil, the groundwater and, to a lesser extent, from the snow. Second, methodologies are developed to retrieve information from accessible intermediate hydrological processes. A geochemical method is used to quantify the contribution of a superficial and a deep reservoir to streamflow. It is shown that, for this specific process, the model formalism is not adapted to our study area and thus leads to poor simulation results. A remote-sensing methodology is proposed to retrieve the snow surfaces. Comparison with the simulation shows that this process can be satisfyingly simulated by the model. The multidisciplinary approach adopted in this study, although supported by the hydrological community, is still uncommon. Copyright © 2007 John Wiley & Sons, Ltd. [source]