List of Units xiii
Preface xv
1 Ventilation for Control 1
1.1 Control Options 2
1.2 Ventilation for Control of Air Contaminants 3
1.3 Ventilation Applications 5
1.4 Case Studies 7
1.5 Summary 9
References 11
2 Principles of Airflow 12
2.1 Airflow 13
2.2 Density 13
2.3 Continuity Relation 14
2.4 Pressure 16
2.4.1 Pressure Units 16
2.4.2 Types of Pressure 17
2.5 Head 18
2.6 Elevation 20
2.7 Pressure Relationships 22
2.7.1 Reynolds Number 24
2.8 Losses 26
2.8.1 Frictional Losses 26
2.8.2 Shock Losses 28
2.9 Losses in Fittings 30
2.9.1 Expansions 30
2.9.2 Contractions 32
2.9.3 Elbows 35
2.9.4 Branch Entries (Junctions) 36
2.10 Summary 38
List of Symbols 38
Problems 39
3 Airflow Measurement Techniques 43
3.1 Measurement of Velocity by PitotStatic Tube 45
3.1.1 Pressure Measurements 47
3.1.2 Velocity Profile in a Duc 50
3.1.3 PitotStatic Traverse 57
3.1.4 Application of the PitotStatic Tube and Potential Errors 60
3.2 Mechanical Devices 61
3.2.1 Rotating Vane Anemometers 61
3.2.2 Deflecting Vane Anemometers (Velometer) 68
3.2.3 Bridled Vane Anemometers 71
3.3 Heated-Element Anemometers 72
3.4 Other Devices 75
3.4.1 Vortex Shedding Anemometers 75
3.4.2 Orifice Meters 76
3.4.3 Venturi Meters 76
3.5 Hood Static Pressure Method 77
3.6 Calibration of Instruments 79
3.7 Observation of Airflow Patterns with Visible Tracers 80
3.7.1 Tracer Design 81
3.7.2 Application of Visible Tracers 84
List of Symbols 85
References 86
Manufacturers of Airflow Measuring Instruments 87
Manufacturers of Smoke Tubes 87
Problems 87
4 General Exhaust Ventilation 90
4.1 Limitations of Application 91
4.2 Equations for General Exhaust Ventilation 93
4.3 Variations in Generation Rate 99
4.4 Mixing 100
4.5 Inlet Outlet Locations 101
4.6 Other Factors 102
4.7 Comparison of General and Local Exhaust 105
List of Symbols 106
References 106
Problems 107
5 Hood Design 108
5.1 Classification of Hood Types 109
5.1.1 Enclosures 109
5.1.2 Exterior Hoods 110
5.1.3 Receiving Hoods 115
5.1.4 Summary 116
5.2 Design of Enclosing Hoods 116
5.3 Design of Exterior Hoods 120
5.3.1 Determination of Capture Velocity 120
5.3.2 Determination of Hood Airflow 125
5.3.3 Exterior Hood Shape and Location 135
5.4 Design of Receiving Hoods 135
5.4.1 Canopy Hoods for Heated Processes 135
5.4.2 Hoods for Grinding Operations 138
5.5 Evaluation of Hood Performance 141
List of Symbols 142
References 142
Appendix: Exterior Hood Centerline Velocity Models 144
Problems 148
6 Hood Designs for Specific Applications 151
6.1 Electroplating 152
6.1.1 Hood Design 152
6.1.2 Airflow 155
6.2 Spray Painting 159
6.2.1 Hood Design 159
6.2.2 Airflow 163
6.3 Processing and Transfer of Granular Material 165
6.4 Welding, Soldering, and Brazing 169
6.5 Chemical Processing 177
6.5.1 Chemical Processing Operations 178
6.6 Semiconductor Gas Cabinets 187
6.6.1 Entry Loss 190
6.6.2 Optimum Exhaust Rate 191
6.7 Low-Volume High-Velocity Systems for Portable Tools 192
Example 6.1 Calculation of Exhaust Rate for Open-Surface Tanks 199
Example 6.2 Design of a Low-Volume High-Velocity Exhaust System 200
List of Symbols 201
References 202
7 Chemical Laboratory Ventilation 204
7.1 Design of Chemical Laboratory Hoods 205
7.1.1 Vertical Sliding Sash Hoods 205
7.1.2 Horizontal Sliding Sash Hoods 209
7.1.3 Auxiliary Air Supply Hoods 212
7.2 Face Velocity for Laboratory Hoods 214
7.3 Special Laboratory Hoods 216
7.4 Laboratory Exhaust System Features 217
7.4.1 System Configuration 217
7.4.2 Construction 218
7.5 Factors Influencing Hood Performance 220
7.5.1 Layout of Laboratory 220
7.5.2 Work Practices 222
7.6 Energy Conservation 224
7.6.1 Reduce Operating Time 224
7.6.2 Limit Airflow 225
7.6.3 Design for Diversity 227
7.6.4 Heat Recovery 227
7.6.5 Ductless Laboratory Hoods 227
7.7 Performance of Laboratory Hoods 228
7.8 General Laboratory Ventilation 229
References 229
Problems 230
8 Design of Single-Hood Systems 232
8.1 Design Approach 233
8.2 Design of a Simple One-Hood System (Banbury Mixer Hood) 234
8.3 Design of a Slot Hood System for a Degreasing Tank 241
8.3.1 Loss Elements in a Complex Hood 241
8.3.2 Degreaser Hood Design Using Velocity Pressure Calculation Sheet (Example 8.2) 245
8.4 Pressure Plot for Single-Hood System 247
List of Symbols 247
Example 8.1 Banbury Mixer System Designed by the Velocity Pressure Method 248
Example 8.2 Degreaser System Designed by the Velocity Pressure Method 250
References 251
Appendix: Metric Version of Example 8.1 252
Problems 252
9 Design of Multiple-Hood Systems 254
9.1 Applications of Multiple-Hood Systems 254
9.2 Balanced Design Approach 256
9.3 Static Pressure Balance Method 260
9.3.1 Foundry Cleaning Room System (Example 9.1) 260
9.3.2 Electroplating Shop (Example 9.2) 262
9.4 Blast Gate Balance Method 265
9.5 Other Computational Methods 265
List of Symbols 266
Example 9.1 Foundry Cleaning Room Designed by Static Pressure Balance Method 267
Example 9.2 Electroplating Shop System Designed by Static Pressure Balance Method 272
References 278
Additional Reading 279
Appendix: Metric Version of Example 9.1 280
10 Fans and Blowers 282
10.1 Types of Air Movers 283
10.1.1 Axial Flow Fans 283
10.1.2 Centrifugal Fans 285
10.1.3 Air Ejectors 287
10.2 Fan Curves 288
10.2.1 Static Pressure Curve 289
10.2.2 Power Curve 291
10.2.3 Mechanical Efficiency Curve 293
10.2.4 Fan Laws 295
10.2.5 Relationship between Fan Curves and Fan Tables 297
10.3 Using Fans in Ventilation Systems 298
10.3.1 General Exhaust Ventilation Systems 298
10.3.2 Local Exhaust Ventilation Systems 300
10.4 Fan Selection Procedure 305
List of Symbols 308
References 309
Problems 309
11 Air-Cleaning Devices 311
11.1 Categories of Air-Cleaning Devices 312
11.1.1 Particle Removers 312
11.1.2 Gas and Vapor Removers 322
11.2 Matching the Air-Cleaning Device to the Contaminant 325
11.2.1 Introduction 325
11.2.2 Device Selection 326
11.3 Integrating the Air Cleaner and the Ventilation System 326
11.3.1 Gravity Settling Devices 330
11.3.2 Centrifugal Collectors 330
11.3.3 Filters 331
11.3.4 Electrostatic Precipitators 334
11.3.5 Scrubbers 334
11.3.6 Gas and Vapor Removers 335
List of Symbols 336
References 337
Problems 337
12 Replacement-Air Systems 338
12.1 Types of Replacement-Air Units 340
12.2 Need for Replacement Air 341
12.3 Quantity of Replacement Air 342
12.4 Delivery of Replacement Air 344
12.4.1 Replacement-Air System 1 (RAS-1), Melting Furnaces 349
12.4.2 Replacement-Air System 2 (RAS-2), Floor Casting 349
12.4.3 Replacement-Air System 3 (RAS-3), Sand Handling 350
12.4.4 Replacement-Air System 4 (RAS-4), Shakeout 351
12.5 Replacement Air for Heating 352
12.6 Energy Conservation and Replacement Air 353
12.7 Summary 356
References 356
13 Quantification of Hood Performance 358
13.1 Hood Airflow Measurements 359
13.2 Hood Capture Efficiency 360
13.2.1 Influence of Cross-Drafts on Hood Performance 361
13.2.2 Relationship between Airflow Patterns and Capture Efficiency 363
13.2.3 Shortcomings of the Centerline Velocity Approach 370
13.3 Use of Capture Efficiency in Hood Design 372
List of Symbols 372
References 373
14 Application of Computational Fluid Dynamics to Ventilation System Design 374
14.1 Introduction 374
14.2 Methods 376
14.2.1 Grid-Based Methods 377
14.2.2 Grid-Free Methods 378
14.3 Applications 379
14.3.1 Historical Perspectives 379
14.3.2 Current Progress 380
14.4 Issues on the Use of Computational Fluid Dynamics 386
14.5 Commercial Codes: Public-Domain Information 387
References 387
Appendix 389
15 Reentry 391
15.1 Airflow around Buildings 393
15.2 Measurement of Reentry 396
15.3 Calculation of Exhaust Dilution 401
15.4 Scale Model Measurement 404
15.5 Design to Prevent Reentry 406
15.5.1 Stack Height Determination 407
15.5.2 Good Engineering Practices for Stack Design 408
List of Symbols 412
References 413
Problems 415
Index 417
