unsw ceic3000 w2 process modeling and analysis

unsw ceic3000 w2 process modeling and analysis - CEIC3000...

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Unformatted text preview: CEIC3000 Process Modelling and Analysis Week 2 Model Development Session 1, 2012 A/Prof. J. Bao Contents 1 General Modelling Principles 1 1.1 Steady-state models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Dynamic models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2.1 Integral Balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2.2 Instantaneous Balances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2.3 Equivalence of instantaneous balance and integral balance . . . . . . . . . . . . 3 1.3 Model classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.3.1 Lumped parameter systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.3.2 Distributed parameter systems . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4 Modelling Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.5 Constitution relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2 Discrete Systems 10 3 Distributed Parameter Systems 12 1 General Modelling Principles 1.1 Steady-state models A process model is developed based on the mass and energy ow to and from the process of interest. A system boundary can be determined as shown in Figure 1. The emphasis in an introductory material and energy balances textbook is on steady-state balance equations that have the following form: [ mass or energy entering a system ] + [ mass or energy generated in a system ] [ mass or energy leaving a system ] = 0 (1) Eq. (1) is deceptively simple because there may be many ins and outs, particularly for component balances. The in and out terms would then include the generation and conversion of species by chemical reaction, respectively. * Wednesday, February 29, 2012. Recommended textbook: Bequette, B.W. Process Dynamics: Modelling, Analysis, and Simulation . Prentice Hall PTR NJ: 1998. ISBN 0-13-206889-3. 1 1.2 Dynamic models 1.2.1 Integral Balance An integral balance is developed by viewing a system at two different snapshots in time. Consider a finite time interval, t, and perform material balance over that time interval: [ mass or energy inside the system at t + t ] [ mass or energy inside the system at t ] = [ mass or energy entering the system from t to t + t ] + [ mass or energy generated in the system from t to t + t ] [ mass or energy leaving the system from t to t + t ] (2) For system in the figure, M | t + t M | t = t + t t m in dt + t + t t m generated t + t t m out dt (3) = t + t t ( m in + m generated m out ) dt (4) where M represents the total mass in the system, while m in and m out represent the mass rates entering and leaving the system, respectively....
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unsw ceic3000 w2 process modeling and analysis - CEIC3000...

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