Modeling Indoor Air Pollution

✍ Scribed by Darrell W. Pepper, David Carrington

• Publisher: Imperial College Press
• Year: 2009
• Tongue: English
• Leaves: 361
• Category: Library

✦ Synopsis

Emission of pollutants and their accumulation due to poor ventilation and air exchange are serious problems currently under investigation by many researchers. Of particular concern are issues involving air quality within buildings. Toxic fumes and airborne diseases are known to produce undesirable odors, eye and nose irritations, sickness, and occasionally death. Other products such as tobacco smoke and carbon monoxide can also have serious health effects on people exposed to a poorly ventilated environment; studies indicate that indirect or passive smoking can also lead to lung cancer. Design for prevention or remediation of indoor air pollution requires expertise in optimizing geometrical configurations; knowledge of HVAC systems, perceived or expected contaminants and source locations; and economics. Much of the design concept involves ways in which to optimize the benefits or balance the advantages and disadvantages of various configurations and equipment. The fact that a room or building will conceivably become contaminated is generally an accepted fact -- to what extent indoor air pollution will become critical is not really known until it happens. A series of numerical models that run in MATLAB are described in the text and placed on the Web. These models include the finite difference method, finite volume method, finite element method, the boundary element method, particle-in-cell, meshless methods, and lagrangian particle transport. In addition, all example problems can be run using COMSOL, a commercial finite-element-based computer code with a great deal of flexibility and application. By accessing AutoCad ICES or DWG file structures, COMSOL permits a building floor plan to be captured and the interior walls discretized into elements. Contents: Fluid Flow Fundamentals; Contaminant Sources; Assessment Criteria; Simple Modeling Techniques; Dynamics of Particles, Gases and Vapors; Numerical Modeling -- Conventional Techniques; Numerical Modeling -- Advanced Techniques; Turbulence Modeling; Homeland Security Issues.

✦ Table of Contents

Contents......Page 12
Acknowledgements......Page 8
Preface......Page 10
1. Introduction......Page 16
1.2 Ventilation Systems......Page 17
1.3 Exposure Risks......Page 18
1.4 Numerical Modeling of Indoor Air Flow.......Page 20
1.5 Comments......Page 22
2.1 Conservation Equations......Page 24
2.2 Ideal Fluids......Page 26
2.2.1 Conformal mapping.......Page 31
2.2.2 Schwarz–Christoffel transform.......Page 34
2.2.3 Numerical mapping.......Page 38
2.2.4 Superposition for stream functions.......Page 39
2.3 Turbulence.......Page 41
2.4 Species Transport.......Page 45
2.5 Comments......Page 47
3.1 Types of Contaminants......Page 48
3.2 Units......Page 50
3.3 Materials......Page 51
3.4 Typical Operations.......Page 53
3.5 The Diffusion Equation.......Page 54
3.6 Diffusion in Air......Page 56
3.7 Evaporation of Droplets......Page 58
3.8 Resuspension of Particulate......Page 61
3.9 Coagulation of Particulate......Page 63
3.10 Comments......Page 64
4.1 Exposure......Page 66
4.2 Economics......Page 69
4.3 Comments......Page 71
5.1 Analytical Tools......Page 72
5.2 Advection Model......Page 80
5.3 Box Model.......Page 82
5.4 Comments......Page 90
6.1 Drag, Shape, and Size of Particles......Page 92
6.2 Particle Motion.......Page 95
6.2.1 Deposition of particulate with aerodynamic
diameters > 1μ by settling......Page 99
6.2.2 Particle motion in electrostatic field.......Page 101
6.2.5 Thermophoretic transport for particles with diameter greater than the molecular mean free path......Page 102
6.3 Particle Flow in Inlets and Flanges.......Page 103
6.4 Comments......Page 106
7. Numerical Modeling – Conventional Techniques......Page 108
7.1 Finite Difference Method......Page 109
7.1.2 Implicit......Page 112
7.1.3 Upwinding.......Page 113
7.2 Finite Volume Method......Page 119
7.2.2 FVM.......Page 124
7.3 The Finite Element Method......Page 127
7.3.1.1 Linear element......Page 130
7.3.1.2 Quadratic and higher order elements......Page 131
7.3.2.1 Triangular elements......Page 137
7.3.2.2 Quadrilateral elements.......Page 139
7.3.2.3 Isoparametric elements......Page 140
7.3.3 Three-dimensional elements......Page 143
7.3.4 Quadrature.......Page 145
7.3.5 Time dependence.......Page 147
7.3.6 Petrov–Galerkin method.......Page 148
7.3.7 Mesh generation.......Page 150
7.3.8 Bandwidth.......Page 155
7.3.9 Adaptation.......Page 156
7.3.9.1 Element subdivision.......Page 160
7.4 Further CFD Examples......Page 165
7.5 Model Verification and Validation......Page 168
7.6 Comments......Page 171
8. Numerical Modeling – Advanced Techniques......Page 174
8.1 Boundary Element Method.......Page 175
8.2 Lagrangian Particle Technique......Page 186
8.3 Particle-in-cell.......Page 190
8.4 Meshless Method......Page 197
8.4.1.1 Smoothed particle hydrodynamics (SPH) techniques including Kernel Particle Methods (RKPM), and general kernel reproduction methods (GKR)......Page 202
8.4.1.2 Meshless Petrov–Galerkin (MLPG) methods including moving least squares (MLS), point interpolation methods (PIM), and hp-clouds.......Page 203
8.4.1.4 Radial basis functions (RBFs)......Page 204
8.4.2.1 Heat transfer in a 2-D plate.......Page 211
8.4.2.2 Singular point in a 2-D domain......Page 212
8.4.2.3 Heat transfer within an irregular domain......Page 214
8.4.2.4 Natural Convection......Page 216
8.5 Molecular Modeling......Page 223
8.6 Boundary Conditions for Mass Transport Analysis.......Page 227
8.7 Comments......Page 230
9.1 Brief History of Turbulence Formulation......Page 232
9.2 Physical Model......Page 236
9.2.1 Turbulent flow......Page 237
9.2.2 Two-equation turbulence closure models......Page 239
9.2.2.1 Two-equation k-ε......Page 240
9.2.2.2 Two-equation k-w......Page 241
9.2.3 Large Eddy Simulation (LES).......Page 242
9.2.4 Direct Numerical Simulation (DNS)......Page 244
9.2.5 Turbulent transport of energy or enthalpy.......Page 245
9.2.6 Derivation of enthalpy transport......Page 246
9.2.7 Turbulent energy transport.......Page 251
9.2.9 Coupled fluid-thermal flow......Page 252
9.3 Numerical Modeling......Page 254
9.3.1 Projection algorithm......Page 255
9.3.2 Finite volume approach......Page 258
9.3.3 Finite element approach......Page 260
9.3.3.1 Weak forms of the governing equations.......Page 261
9.3.3.2 Matrix equations.......Page 265
9.3.3.3 Time advancement of the explicit/implicit matrix equations......Page 267
9.3.3.4 Mass lumping......Page 268
9.3.3.5 General numerical solution.......Page 269
9.4 Stability and Time Dependent Solution......Page 270
9.5 Boundary Conditions.......Page 271
9.5.1 Boundary conditions for velocity under decomposition......Page 272
9.5.2 Boundary conditions for pressure and velocity correction.......Page 273
9.5.3 Boundary conditions for turbulent kinetic energy and specific dissipation rate......Page 274
9.5.4 Boundary conditions for thermal and species transport......Page 277
9.5.5 Thermal and species flux calculation in the presence of Dirichlet boundaries......Page 278
9.6 Validation of Turbulence Models......Page 279
9.7 Comments......Page 289
10.1 Introduction.......Page 292
10.2 Potential Hazards......Page 293
10.2.1 Prevention and protection.......Page 298
10.3 A Simple Model......Page 301
10.3.1 Example – analytical model of anthrax dispersion:......Page 305
10.3.2 Example – numerical model of anthrax dispersion:......Page 307
10.4.1 CONTAM 2.4 (NIST).......Page 311
10.4.2 I-BEAM (EPA)......Page 313
10.4.3 COMIS-MIAQ (APTG-LBNL)......Page 314
10.4.4 FLOVENT (Flomerics, Inc.)......Page 315
10.5 Comments......Page 316
Appendix A Diffusion Coefficients in Gas......Page 318
B.1.1 Model properties......Page 324
B.1.2.1 Geom1......Page 325
B.1.2.3 Boundary mode......Page 326
B.1.4.1 Mesh statistics......Page 327
B.1.5.1 Application mode properties......Page 328
B.1.6 Application mode: Convection and diffusion......Page 329
B.1.6.4 Subdomain settings......Page 330
B.1.7.2 Stationary......Page 331
B.1.7.3 Advanced......Page 332
B.1.8 Postprocessing......Page 333
B.2.1 Answer input deck......Page 334
B.2.2 Answer solutions......Page 336
Bibliography......Page 338
Index......Page 356