Adv_Process_Modelin_ - Advance Process Modeling Assoc Prof Ir Dr Mohd Sobri Takriff Dept of Chemical& Process Engineering Universiti kebangsaan

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Unformatted text preview: Advance Process Modeling Assoc. Prof. Ir. Dr. Mohd Sobri Takriff Dept. of Chemical & Process Engineering Universiti kebangsaan Malaysia © 2008 Introduction 1 1.0 INTRODUCTION DEFINITION: Before further discussion on process modeling is presented, it is of paramount importance that the definition of a model in general and process model is first understood. Several defintions of model and process model are presented below. & Model is derived from the Latin – modus which means a measure. Used as a noun it means “a small representation of a planned or existing object - Webster’s New World Dictionary & A mathematical or physical system, obeying certain specified conditions, whose behavior is used to understand a physical, biological or social system to which it is analogous in some way- McGraw-Hill Dictionary of scientific and technical terms & A process model is a set of equations (including the necessary input data) that allows us to predict the behavior of a chemical system - Bequette, B.W, 1998 The definition by Bequette (1998) will used in this course. Figure 1 ilustrate miniature representation or a model of a house and a sport car. These models have all the atributes of the actual object. Introduction 2 (a) House model (b) Car Model Figure 1. Example of models A good model is desired to have all the attributes able to predict or emulate the behaviors of of the actual process or object. The accuracy of a model depends on accurately it is able represent the actual object. There is however a trade off between model accuracy and solution requirements. An accurate model will require consideration of evry fine detils of the object which is translated into a complex sets of mathematical equations whose solution will also be very complex. CLASSIFICATION OF MODEL Process model may be classified into three categories namely, theoretical or fundamental model, empirical model or semi-empirical model. & Theoretical or fundamental model is developed from fundamental principles of physics and chemistry. Fundamental in this respect means models that are based on known physical-chemical relationships. This includes the conservation of mass and conservation of energy as well as reaction kinetics, transport phenomena, and thermodynamic (phase equilibrium, etc.) relationships. & Empirical models on the other hand is developed from mathematical and statistical analysis. An empirical model might be used if the process is too complex for a fundamental model (either in the formulation of the model, or the numerical solution of the model), or if the empirical model has satisfactory predictive capability. An example of an empirical model Introduction 3 is a simple least squares fit of an equation to experimental data....
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This note was uploaded on 03/21/2010 for the course ENGINEERIN Advance Pr taught by Professor - during the Spring '10 term at Universiti Teknologi Malaysia.

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Adv_Process_Modelin_ - Advance Process Modeling Assoc Prof Ir Dr Mohd Sobri Takriff Dept of Chemical& Process Engineering Universiti kebangsaan

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