PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Modelling Lumped Parameter Systems C5A
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences General 3D conservation space Governing equation
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences General 3D conservation space Governing equation General differential form where can vary in space and time Governing equation Lumped form where does not vary in space but varies in time
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences The lumped conservation balance General conservation balance Assuming homogeneity in the conserved quantity Lumped conservation balance
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Model Characteristics
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences The mass balance volume
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences A Process Example
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Overall mass balance
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Component mass balances
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Molar Balance Mass balances that involve reactions are most conveniently expressed as molar balances. i.e., where g i is the rate of generation or consumption of species i through reaction. i.e., ~
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Tank mass balance z P 1 P 2 P 3 P 0 F 1 F 2 Balance volumes tank holdup valves Conservation Constitutive A1: Well mixed in x,y,z directions A2: no mass holdup in valves A3: no physical losses from system A4: no mass losses from evaporation A5: Isothermal operation z x y Assumptions
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences The energy balance volume
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Energy balance Components of the balance Convective energy flows Conductive/radiative flows Work terms
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Energy Balance Terms Convective flows Heat flows Work terms shaft work expansion work flow work
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Total energy balance
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Reduced energy balances Neglect P E, K E PV constant or small Output specific enthalpies equivalent to bulk phase
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Reduced energy balances (cont.) all enthalpies evaluated at system temperature explicit appearance of reaction terms and temperature
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Tank energy balance Balance volumes tank holdup jacket holdup A5: Fixed mass holdup in jacket A6: well mixed jacket contents A7: negligible KE terms A8: negligible PE terms A9: negligible PV terms A10: jacket temperature is averaged A11: fixed heat capacities Assumptions
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Tank energy balances Conservation Constitutive Tank Conservation Constitutive Jacket System
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Momentum balance
PROCESS MODELLING AND MODEL ANALYSIS © CAPE Centre, The University of Queensland Hungarian Academy of Sciences Example momentum balance