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Process Simulators (process + simulator)

Distribution by Scientific Domains

Chemistry	66%

Selected Abstracts

Shear stress nucleation in microcellular foaming process

POLYMER ENGINEERING & SCIENCE, Issue 6 2002
Lee Chen
The effect of shear stress on the foaming process has been studied using the Foaming Process Simulator developed previously. The polymer samples were saturated with gas in the test chamber. A rotor was used to apply shear stress to the polymer samples. Foams were obtained by releasing the pressure quickly. Polystyrene, filled and unfilled, was used as the material. The cell density was analyzed with a scanning electron microscope. It was found that the cell density was significantly increased by introducing shear stress. The higher the shear stress, the more significant the effect. A cell stretch model has been developed to explain the cell nucleation enhancement with shear stress. The nucleation sites are stretched under the shear stress. The stretched nuclei are much easier to expand for cell formation owing to their larger surface areas and non-spherical shapes. The model prediction shows the same tendency of the effect of shear stress observed in the experiment. The key issue with shear stress nucleation is the transformation of mechanical shear energy into surface energy. [source]

Performance characteristics and modelling of a micro gas turbine for their integration with thermally activated cooling technologies

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2007
Adrián Vidal
Abstract We have developed a simple model of a micro gas turbine system operating at high ambient temperatures and characterized its performance with a view to integrating this system with thermally activated cooling technologies. To develop and validate this model, we used experimental data from the micro gas turbine test facility of the CREVER research centre. The microturbine components were modelled and the thermodynamic properties of air and combustion gases were estimated using a commercial process simulator. Important information such as net output power, microturbine fuel consumption and exhaust gas mass flow rate can be obtained with the empirical correlations we have developed in this study. This information can be useful for design exhaust gas fired absorption chillers. Copyright © 2006 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 algorithm for the use of surrogate models in modular flowsheet optimization

AICHE JOURNAL, Issue 10 2008
José A. Caballero
Abstract In this work a methodology is presented for the rigorous optimization of nonlinear programming problems in which the objective function and (or) some constraints are represented by noisy implicit black box functions. The special application considered is the optimization of modular process simulators in which the derivatives are not available and some unit operations introduce noise preventing the calculation of accurate derivatives. The black box modules are substituted by metamodels based on a kriging interpolation that assumes that the errors are not independent but a function of the independent variables. A Kriging metamodel uses non-Euclidean measure of distance to avoid sensitivity to the units of measure. It includes adjustable parameters that weigh the importance of each variable for obtaining a good model representation, and it allows calculating errors that can be used to establish stopping criteria and provide a solid base to deal with "possible infeasibility" due to inaccuracies in the metamodel representation of objective function and constraints. The algorithm continues with a refining stage and successive bound contraction in the domain of independent variables with or without kriging recalibration until an acceptable accuracy in the metamodel is obtained. The procedure is illustrated with several examples. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source]

An exergy calculator tool for process simulation

A New Numerical Approach for a Detailed Multicomponent Gas Separation Membrane Model and AspenPlus Simulation

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2005
M. H. Murad Chowdhury
Abstract A new numerical solution approach for a widely accepted model developed earlier by Pan [1] for multicomponent gas separation by high-flux asymmetric membranes is presented. The advantage of the new technique is that it can easily be incorporated into commercial process simulators such as AspenPlusTM [2] as a user-model for an overall membrane process study and for the design and simulation of hybrid processes (i.e., membrane plus chemical absorption or membrane plus physical absorption). The proposed technique does not require initial estimates of the pressure, flow and concentration profiles inside the fiber as does in Pan's original approach, thus allowing faster execution of the model equations. The numerical solution was formulated as an initial value problem (IVP). Either Adams-Moulton's or Gear's backward differentiation formulas (BDF) method was used for solving the non-linear differential equations, and a modified Powell hybrid algorithm with a finite-difference approximation of the Jacobian was used to solve the non-linear algebraic equations. The model predictions were validated with experimental data reported in the literature for different types of membrane gas separation systems with or without purge streams. The robustness of the new numerical technique was also tested by simulating the stiff type of problems such as air dehydration. This demonstrates the potential of the new solution technique to handle different membrane systems conveniently. As an illustration, a multi-stage membrane plant with recycle and purge streams has been designed and simulated for CO2 capture from a 500,MW power plant flue gas as a first step to build hybrid processes and also to make an economic comparison among different existing separation technologies available for CO2 separation from flue gas. [source]