Agro-Product Processing Technology

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Principles and Practice

B. K. Bala(Autor*in)

CRC Press

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Professor B. K. Bala is the dean of the Faculty of Engineering,

Bangabandhu Sheikh Mujibur Rahman Science and Technology

University, Gopalganj, Bangladesh, and was a professor in the

Department of Farm Power and Machinery, Bangladesh Agricultural

University, Mymensingh, Bangladesh, where he was engaged in teaching

and research for over 42 years starting from 1970. He has supervised

more than a dozen PhD students in the areas of drying and storage

of agro products, modeling of food security, modeling of integrated

energy systems and energy policy, renewable energy, modeling of climate

change impacts, and emerging technologies such as neural network,

exergy, genetic algorithm, and computational fluid dynamics.

Professor Bala received a B.Sc. (Eng.) degree from Bangladesh

University of Engineering and Technology, Dhaka, Bangladesh, in

1969 and an M.Eng. degree from the Asian Institute of Technology, Bangkok, Thailand, in 1975.

Professor Bala also received a Ph.D. degree from the University of Newcastle upon Tyne, UK, in

1983 and worked on modeling and simulation of heat and mass transfer during industrial deep-bed

drying of malt and provided the foundation and basis for energy conservation and online control of

industrial deep bed drying of malt. He also worked on solar drying as an EC postdoctoral fellow at

the University of Newcastle upon Tyne, UK, from 1992 to 1993. He was on a DAAD study visit at

the Institute of Agricultural Engineering in the Tropics and Subtropics, University of Hohenheim,

Germany, for research on solar drying in 1995. Professor Bala also served as a research fellow at the

Institute of Agricultural and Food Policy Research, Universiti Putra Malaysia from 2012 to 2014.

Professor Bala has published 207 scientific papers mostly in high-impact factor journals, and

he is also the author of nine textbooks. He is the author of Drying and Storage of Cereal Grains

published by Wiley-Blackwell in 2017, and he is the co-author of System Dynamics Modeling and

Simulation published by Springer in 2017.

Autor*in

B. K. Bala

Bangabandhu Sheikh Mujibur Rahman Science and Technology University, Bangladesh

Inhalt

Contents

Foreword ..........................................................................................................................................xv

Preface............................................................................................................................................xvii

Author .............................................................................................................................................xix

Chapter 1 Introduction ..................................................................................................................1

1.1 Introduction .........................................................................................................1

1.2 Impotence of Postharvest Technology .................................................................2

1.3 Importance of Postharvest Losses .......................................................................2

1.4 Postharvest Technology .......................................................................................3

References ....................................................................................................................5

Chapter 2 Physical, Thermal, and Chemical Properties of Food and Biological Materials .........7

2.1 Introduction .........................................................................................................7

2.2 Physical Properties ..............................................................................................7

2.2.1 Physical Dimensions ................................................................................7

2.2.2 1000-Grain Weight ..................................................................................7

2.2.3 Bulk Density ............................................................................................8

2.2.4 Shrinkage .................................................................................................8

2.2.5 Friction ....................................................................................................9

2.2.5.1 Angle of Internal Friction and Angle of Repose ......................9

2.2.5.2 Coefficient of Friction ............................................................. 10

2.3 Thermal Properties ............................................................................................ 11

2.3.1 Specific Heat .......................................................................................... 11

2.3.2 Thermal Conductivity ........................................................................... 13

2.3.2.1 Theory ..................................................................................... 13

2.3.2.2 Apparatus and Measurement .................................................. 14

2.3.3 Latent Heat of Vaporization .................................................................. 15

2.3.3.1 Determination of Latent Heat of Vaporization ....................... 16

2.3.4 Heat Transfer Coefficient of Product Bed ............................................. 18

2.3.4.1 Dimensional Analysis ............................................................. 19

2.3.4.2 Comparison of Theory and Experiment ................................. 19

2.3.4.3 Theory .....................................................................................20

2.3.4.4 Determination of Volumetric Heat Transfer Coefficient ........22

2.4 Chemical Properties ..........................................................................................24

2.4.1 Starch .....................................................................................................24

2.4.2 Protein ...................................................................................................24

2.4.3 Fat ..........................................................................................................24

2.4.4 Vitamin ..................................................................................................24

Key to Symbols ..........................................................................................................24

Exercises .....................................................................................................................26

References ..................................................................................................................27

Chapter 3 Cleaning, Grading, and Sorting .................................................................................29

3.1 Grade Factor ....................................................................................................29

3.2 Washing ...........................................................................................................30

3.3 Sorting Fruits and Vegetables ..........................................................................30

3.4 Sorting Grain ...................................................................................................30

3.5 Spiral Separator ............................................................................................... 32

3.6 Indent Cylinder Separator ............................................................................... 33

3.7 Color Separator ................................................................................................ 33

3.8 Centrifugal Separation ....................................................................................34

3.8.1 Stokes' Equation .................................................................................34

3.9 The Centrifuge................................................................................................. 35

3.10 The Cream Separator ....................................................................................... 35

3.11 Cyclone Separator ............................................................................................36

3.12 Machine Vision................................................................................................ 39

3.12.1 Image Acquisition ............................................................................. 39

3.12.1.1 Computer Vision System .................................................. 39

3.12.1.2 Ultrasound and Infrared ...................................................40

3.12.1.3 Tomographic Imaging ......................................................40

3.12.2 Preprocessing ....................................................................................40

3.12.3 Segmentation ..................................................................................... 41

3.12.4 Feature Extraction ............................................................................. 42

3.12.4.1 Color Features .................................................................. 42

3.12.4.2 Morphological Features.................................................... 43

3.12.4.3 Texture Features ............................................................... 43

3.12.5 Classification .....................................................................................44

Bibliography ............................................................................................................... 45

Chapter 4 Psychrometry .............................................................................................................. 47

4.1 Introduction ..................................................................................................... 47

4.2 Psychrometric Terms ....................................................................................... 47

4.2.1 Humidity Ratio ..................................................................................48

4.2.2 Relative Humidity .............................................................................48

4.2.3 Specific Volume ................................................................................49

4.2.4 Vapor Pressure ..................................................................................49

4.2.5 Dry-Bulb Temperature ......................................................................49

4.2.6 Dew Point Temperature.....................................................................49

4.2.7 Wet-Bulb Temperature ......................................................................49

4.2.8 Enthalpy ............................................................................................50

4.2.9 Adiabatic Wet-Bulb Temperature ...................................................... 51

4.2.10 Psychrometric Wet-Bulb Temperature .............................................. 52

4.3 Construction of Psychrometric Chart ..............................................................54

4.4 Use of Psychrometric Chart ............................................................................54

4.4.1 Sensible Heating and Cooling ........................................................... 55

4.4.2 Heating with Humidification ............................................................. 55

4.4.3 Cooling with Humidification ............................................................56

4.4.4 Cooling with Dehumidification.........................................................56

4.4.5 Drying ............................................................................................... 57

4.4.6 Mixing of Airstreams ....................................................................... 59

4.4.7 Heat Addition with Air Mixing .......................................................... 61

4.4.8 Drying with Recirculation .................................................................. 62

Key to Symbols ..........................................................................................................66

Exercises .....................................................................................................................68

Bibliography ...............................................................................................................68

Chapter 5 Drying of Agro Products ............................................................................................69

5.1 Principles of Drying ..........................................................................................69

5.2 Importance of Drying ........................................................................................69

5.3 Moisture Content ............................................................................................... 70

5.3.1 Moisture Content Representation .......................................................... 70

5.3.2 Determination of Moisture Content ...................................................... 72

5.3.2.1 Direct Methods ....................................................................... 73

5.3.2.2 Indirect Methods ..................................................................... 75

5.4 Equilibrium Moisture Content .......................................................................... 76

5.4.1 Determination of Static Equilibrium Moisture Content ........................77

5.4.2 Static Equilibrium Moisture Content Models .......................................77

5.5 Mechanism of Drying........................................................................................82

5.6 Thin-Layer Drying ............................................................................................84

5.6.1 Thin-Layer Drying Equations ...............................................................84

5.6.1.1 Empirical Drying Equations ...................................................84

5.6.1.2 Theoretical Drying Equations ................................................84

5.6.1.3 Semi-Theoretical Drying Equations .......................................85

5.6.2 Drying Rate ...........................................................................................87

5.6.3 Drying Parameters .................................................................................87

5.6.4 Drying Rate Constant and Diffusion Coefficient ..................................88

5.6.4.1 Drying Rate Constant .............................................................88

5.6.5 Half Response Time .............................................................................. 91

5.7 Deep-Bed Drying ..............................................................................................92

5.7.1 Logarithmic Model ................................................................................92

5.7.2 Partial Differential Equation Model ......................................................98

5.7.2.1 Method of Solution ............................................................... 102

5.7.2.2 Comparisons of Simulated and Observed Results ................ 103

5.8 Fluidized Bed Drying Model .......................................................................... 103

5.8.1 Heat Balance Equation ........................................................................ 104

5.8.2 Drying Rate Equation .......................................................................... 104

5.8.3 Mass Balance Equation ....................................................................... 105

5.9 Agro-Product Drying Systems ........................................................................ 106

5.9.1 Solar Drying Systems .......................................................................... 106

5.9.1.1 Solar Dryers .......................................................................... 106

5.9.2 Batch Drying Systems ......................................................................... 110

5.9.2.1 Flatbed Dryer ........................................................................ 111

5.9.3 Continuous Flow Drying Systems ....................................................... 113

5.9.3.1 Cross-Flow Dryer ................................................................. 113

5.9.3.2 Cross-Flow Batch Dryer ....................................................... 113

5.9.3.3 Concurrent Flow Dryer ......................................................... 114

5.9.3.4 Counterflow Dryer ................................................................ 114

5.9.3.5 Mixed-Flow Dryer ................................................................ 116

5.10 Safe Temperature for Drying Grain .............................................................. 117

5.11 Selection of Dryers ........................................................................................ 117

Key to Symbols ........................................................................................................ 118

Exercises ................................................................................................................... 119

Bibliography ............................................................................................................. 120

Chapter 6 Parboiling of Rice .................................................................................................... 123

6.1 Introduction ................................................................................................... 123

6.2 Principles of Parboiling .................................................................................124

6.3 Soaking ..........................................................................................................124

6.3.1 Kinetics of Soaking ........................................................................... 126

6.3.2 Finite Element Modeling of Soaking of Water by Paddy .................. 132

6.3.3 Half Response Time .......................................................................... 137

6.3.4 Kinetics of Water Diffusion and Starch Gelatinization .................... 137

6.4 Steaming ........................................................................................................ 140

6.5 Drying ............................................................................................................ 140

6.6 Effect of Parboiling on Milling, Nutritional, and Cooking Qualities

of Rice ........................................................................................................... 141

6.7 Parboiling Methods ....................................................................................... 142

6.7.1 Traditional Methods .......................................................................... 142

6.7.1.1 Single Stage Parboiling ...................................................... 142

6.7.1.2 Double Stage Parboiling ..................................................... 142

6.7.2 Modern Methods ............................................................................... 142

6.7.2.1 CFTRI (Central Food Technological Research

Industries) Method ............................................................. 143

6.7.2.2 Jadavpur University Method .............................................. 143

6.7.2.3 Malek Process .................................................................... 143

6.7.2.4 Schule Process .................................................................... 143

6.7.2.5 Crystal Rice Process .......................................................... 144

6.7.2.6 Rice Conversion Process .................................................... 144

6.7.2.7 Avorio Process .................................................................... 144

6.7.3 Estimation of Heat Required for Parboiling ...................................... 144

6.7.3.1 Soaking Operation.............................................................. 144

6.7.3.2 Steaming Operation............................................................ 144

6.7.3.3 Drying Operation ............................................................... 145

Exercises ................................................................................................................... 159

Bibliography ............................................................................................................. 160

Chapter 7 Milling of Rice and Wheat ....................................................................................... 163

7.1 Introduction ................................................................................................... 163

7.2 Rice Milling .................................................................................................. 163

7.3 Traditional Methods ...................................................................................... 163

7.3.1 Home Pounding ................................................................................. 163

7.3.2 Huller Mills ....................................................................................... 164

7.3.3 Sheller Mills ...................................................................................... 164

7.3.4 Rubber Roll Sheller Mills .................................................................. 164

7.4 The Modern Rice Milling Process ................................................................ 165

7.5 Modern Rice Milling Machinery .................................................................... 167

7.5.1 Paddy Cleaner ...................................................................................... 167

7.5.2 Stoner ................................................................................................... 167

7.5.3 Rubber Roll Sheller ............................................................................. 167

7.5.4 Paddy Separator ................................................................................... 169

7.5.5 Whitening or Polishing........................................................................ 171

7.5.5.1 Cone-Type Polisher ............................................................... 171

7.5.5.2 Horizontal Abrasive-Type Polisher ....................................... 172

7.5.5.3 Friction-Type Polisher ........................................................... 172

7.5.6 Bran and Polished Rice Separator ....................................................... 173

7.5.7 Rice Grader ......................................................................................... 173

7.5.8 Rice Mixing ......................................................................................... 174

7.6 Wheat Milling ................................................................................................. 174

7.6.1 Conditioning/Hydrothermal Treatment ............................................... 174

7.6.2 Milling ................................................................................................. 174

7.6.3 Storage of Finished Products ............................................................... 175

7.7 Size Characteristics ......................................................................................... 175

7.7.1 Sieve ..................................................................................................... 175

7.7.2 Fineness Modulus ................................................................................ 176

7.7.3 Energy Requirements .......................................................................... 177

Bibliography ............................................................................................................. 179

Chapter 8 By-Product Utilization ............................................................................................. 181

8.1 Introduction ..................................................................................................... 181

8.2 Fuels and Combustion ..................................................................................... 181

8.2.1 Furnaces .............................................................................................. 182

8.3 Pyrolysis and Gasification ............................................................................... 183

8.3.1 Pyrolysis (Destructive Distillation) and Gasification .......................... 183

8.3.2 Types of Gasifiers ................................................................................ 184

8.3.2.1 Countercurrent Moving Bed Gasifiers .................................. 185

8.3.2.2 Concurrent Moving Bed Gasifiers ........................................ 185

8.3.2.3 Crosscurrent Moving Bed Gasifiers ..................................... 185

8.3.2.4 Fluidized Bed Gasifiers ........................................................ 185

8.3.3 Gasification Process ............................................................................ 185

8.3.3.1 Oxidation .............................................................................. 186

8.3.3.2 Reduction .............................................................................. 186

8.3.3.3 Drying ................................................................................... 186

8.3.4 Gasifier Units ....................................................................................... 186

8.4 Liquefaction ..................................................................................................... 187

8.5 Hydrolysis Followed by Fermentation ............................................................. 189

8.6 Biochar Production and Utilization ................................................................. 190

8.6.1 Biochar Carbonizer ............................................................................. 190

8.6.2 Types of Carbonizers ........................................................................... 191

8.6.2.1 Application............................................................................ 192

8.7 Rice Husk Pelletizing and Briquetting ............................................................ 192

8.7.1 Need for Briquetting ............................................................................ 193

8.7.2 Principle and Technology .................................................................... 193

8.7.3 Types of Briquetting Machines ....................................................... 193

8.7.3.1 High- and Medium-Pressure Compaction .......................194

8.7.3.2 Screw Press ...................................................................... 194

8.7.3.3 Piston Press ...................................................................... 195

8.7.3.4 Low-Pressure Compaction ............................................... 195

8.7.3.5 Hand-Molded Briquettes .................................................. 195

8.7.4 Applications ..................................................................................... 195

8.7.5 Limitations....................................................................................... 196

8.7.6 Future Prospective ........................................................................... 196

8.8 Biogas Digesters ............................................................................................ 196

8.8.1 Anaerobic Digestion Process ........................................................... 197

8.8.2 Indian-Type Biogas Digester ........................................................... 197

8.8.3 The Chinese Biogas Digester .......................................................... 198

8.8.4 Digester Sizing ................................................................................ 199

8.9 Composting ....................................................................................................202

8.9.1 Process of Composting ....................................................................203

8.9.2 Mixing of Materials in the Compost ...............................................203

8.9.3 Starting a Composter .......................................................................204

8.9.4 Operating a Compost .......................................................................204

8.9.5 Simple Thermophile Composting Procedure ..................................204

8.9.6 Types of Composters .......................................................................205

8.10 Utilization of Rice Bran - Stabilizer Design and Oil Extraction ..................207

8.11 Bran - Stabilizer Design ...............................................................................207

8.12 Oil Extraction ................................................................................................207

8.12.1 Batch Extraction Method .................................................................208

Bibliography .............................................................................................................208

Chapter 9 Storage of Agro Products .........................................................................................209

9.1 Principles of Storage ......................................................................................209

9.2 Interactions of Physical, Chemical, and Biological Variables in the

Deterioration of Stored Grains ...................................................................... 211

9.3 Computer Simulation Modeling for Stored Grain Pest Management ........... 212

9.4 Grain Storage Systems .................................................................................. 213

9.4.1 Traditional Storage Systems ............................................................ 213

9.4.2 Modern Storage Systems ................................................................. 214

9.4.2.1 Bagged Storage System .................................................... 214

9.4.2.2 Silo Storage System ......................................................... 215

9.4.2.3 Airtight Grain Storage ..................................................... 216

9.4.2.4 Aerated Storage System ................................................... 218

9.4.2.5 Low-Temperature Storage System (Grain Chilling

by Refrigeration) .............................................................. 221

9.4.2.6 Controlled Atmosphere Storage Systems ........................224

9.4.2.7 Damp Grain Storage System with Chemicals .................226

9.5 Design of Grain Storages...............................................................................228

9.5.1 Structural Requirements ..................................................................228

9.5.2 Janssen's Equation ...........................................................................229

9.5.3 Rankine's Equation.......................................................................... 232

9.5.4 Airy's Equation ................................................................................ 233

9.5.5 Construction Materials ....................................................................236

Key to Symbols ........................................................................................................240

Exercises ................................................................................................................... 241

Bibliography ............................................................................................................. 241

Chapter 10 Heating and Cooling of Agro Products ....................................................................245

10.1 Introduction ....................................................................................................245

10.2 Heat Conduction ............................................................................................246

10.2.1 The Differential Equation of Heat Conduction in Cartesian

and Cylindrical Coordinate Systems ...............................................246

10.2.1.1 The Differential Equation of

Heat Conduction in Cartesian Coordinate System ..........246

10.2.1.2 The Differential Equation of

Heat Conduction in Cylindrical Coordinate System .......248

10.2.2 The Composite Wall ........................................................................249

10.2.3 Cylinder and Sphere ......................................................................... 251

10.3 Convection ..................................................................................................... 252

10.3.1 Forced Convection ........................................................................... 252

10.3.2 Natural or Free Convection .............................................................. 255

10.3.3 Heat Exchangers ..............................................................................256

10.4 Radiation ........................................................................................................ 261

10.4.1 Radiation Intensity and Shape Factor ..............................................263

10.4.2 Radiation Exchange between Black Surfaces ..................................264

10.4.3 Heat Exchange by Radiation between Gray Surfaces......................265

10.5 Cooling ........................................................................................................... 267

10.5.1 Cooling Rate .................................................................................... 267

10.6 Freezing .........................................................................................................269

10.6.1 Freezing Point Depression ...............................................................269

10.7 Heating ........................................................................................................... 271

10.7.1 Boiling-Point Elevation .................................................................... 272

Key to Symbols ....................................................................................................... 275

Exercises ................................................................................................................. 276

Bibliography ............................................................................................................277

Chapter 11 Refrigeration and Cold Storage ................................................................................ 279

11.1 Introduction .................................................................................................... 279

11.2 Vapor Compression Refrigeration Cycle .......................................................280

11.3 Pressure-Enthalpy (p-h) Chart ......................................................................280

11.3.1 Unit of Refrigeration ........................................................................ 281

11.4 Refrigerants .................................................................................................... 281

11.4.1 Desirable Characteristics of Refrigerants ........................................ 281

11.5 Construction of Psychrometric Chart ............................................................287

11.6 Moisture Control and Storage of Vegetables Crops ....................................... 291

11.6.1 Potatoes ............................................................................................ 291

11.6.1.1 Adequate Volume ............................................................. 291

11.6.1.2 Adequate Strength ........................................................... 291

11.6.1.3 Storage Environment .......................................................292

11.6.1.4 Suberization Period ..........................................................292

11.6.1.5 Short-Term Storage ..........................................................292

11.6.1.6 Long-Term Storage ..........................................................292

11.7 Cooling Requirement .....................................................................................293

Exercises ...................................................................................................................297

Bibliography .............................................................................................................298

Chapter 12 Separation .................................................................................................................299

12.1 Introduction ....................................................................................................299

12.2 Contact Equilibrium Process .........................................................................299

12.2.1 Absorption........................................................................................299

12.2.2 Extraction .........................................................................................300

12.2.2.1 Rate of Extraction ............................................................300

12.2.2.2 Leaching .......................................................................... 301

12.2.3 Distillation .......................................................................................303

12.2.3.1 Vapor-Liquid Equilibrium ...............................................303

12.2.3.2 Flash Vaporization ...........................................................305

12.2.3.3 Batch Distillation .............................................................306

12.2.3.4 Fractionation ....................................................................307

12.2.3.5 Steam Distillation ............................................................ 311

12.3 Mechanical Separation Process ..................................................................... 312

12.3.1 Filtration ........................................................................................... 312

12.3.2 Sedimentation .................................................................................. 314

12.3.2.1 Sedimentation for Low Concentration Suspensions .......... 314

12.3.2.2 Sedimentation for High Concentration Suspensions ......... 315

12.3.3 Centrifugation .................................................................................. 316

12.3.3.1 Rate Separation ................................................................ 316

12.3.3.2 Liquid-Liquid Separation ................................................ 317

12.3.3.3 Particle Gas Separation ................................................... 318

Exercises ................................................................................................................... 319

Bibliography ............................................................................................................. 319

Chapter 13 Materials Handling and Conveying ......................................................................... 321

13.1 Introduction .................................................................................................... 321

13.2 Principles of Materials Handling ................................................................... 322

13.3 Classification of Materials Handling Equipment ........................................... 322

13.4 Belt Conveyors ............................................................................................... 323

13.4.1 The Capacity of the Conveyor Belt Needed..................................... 325

13.4.2 Belt Width ........................................................................................ 325

13.4.3 Belt Speed ........................................................................................ 326

13.4.4 Belt Tension ...................................................................................... 326

13.4.5 Selection of Belt Carcass ................................................................. 327

13.4.6 Selection of Driving and Other Pulleys ........................................... 327

13.4.7 Motor Power ..................................................................................... 327

13.4.8 Selection of Idlers ............................................................................ 328

13.5 Chain Conveyors ............................................................................................ 329

13.5.1 Trolley Chain Conveyor ................................................................... 329

13.5.2 Scraper Chain Conveyor .................................................................. 330

13.5.3 Apron Chain Conveyor .................................................................... 330

13.6 Screw Conveyors ......................................................................................... 331

13.6.1 Power Requirement for Screw Conveyors ..................................... 332

13.7 Bucket Conveyors ........................................................................................ 333

13.8 Pneumatic Conveyors .................................................................................. 334

13.9 Hydraulic Conveyors ................................................................................... 337

13.10 Gravity Conveyors ....................................................................................... 338

13.11 Cranes.......................................................................................................... 338

13.12 Lift and Carrying Trucks and Cart ............................................................. 338

13.13 Robotic Handling System ........................................................................... 338

Exercises ...................................................................................................................348

Bibliography .............................................................................................................349

Chapter 14 Process Dynamics and Control ................................................................................ 351

14.1 Introduction ................................................................................................. 351

14.2 Feedback Control Systems .......................................................................... 351

14.3 Block Diagrams ........................................................................................... 351

14.4 Dynamic Behavior of First- and Second-Order Systems ............................ 352

14.4.1 First-Order System ........................................................................ 352

14.4.2 Step Input ....................................................................................... 353

14.4.3 Ramp Input .................................................................................... 354

14.4.4 Sinusoidal Input ............................................................................. 354

14.4.5 Second-Order System .................................................................... 355

14.5 The Laplace Transform ............................................................................... 356

14.6 Transfer Function ........................................................................................ 358

14.6.1 Routh-Hurwitz Stability Criterion ................................................ 359

14.7 Transient Response...................................................................................... 361

14.7.1 Performance of Second-Order System .......................................... 361

14.7.2 Performance Indices ...................................................................... 362

14.8 Frequency Response .................................................................................... 362

14.8.1 Bode Plot ....................................................................................... 363

14.8.1.1 First-Order Process K

(?s+1) ............................................... 363

14.8.1.2 Integrating Process G(s) Ks

= ........................................364

14.8.1.3 Second-Order Process G(s) K

2s2 2 s 1 = + ? + ........................364

14.8.1.4 Process Zero s +1 ........................................................365

14.8.1.5 Time Delay e?j- ...........................................................366

14.8.1.6 Bode Stability Criterion ................................................ 367

14.8.1.7 Gain Margin and Phase Margin ................................... 367

14.8.2 Nyquist Criterion ...........................................................................368

14.8.2.1 Gain Margin and Phase Margin ...................................369

14.9 Frequency Response of Controllers ............................................................369

14.9.1 Proportional Controller .................................................................369

14.9.2 Proportional-Integral Controller ...................................................369

14.9.3 Ideal Proportional-Derivative Controller...................................... 370

14.9.4 Proportional-Derivative Controller with Filter ............................. 370

14.9.5 Parallel PID Controller .................................................................. 370

14.9.6 Series PID Controller .................................................................... 371

14.9.7 Series PID Controller with a Derivative Filter .............................. 371

Exercises ................................................................................................................... 373

Bibliography ............................................................................................................. 374

Chapter 15 Emerging Technologies ............................................................................................ 375

15.1 Introduction .................................................................................................... 375

15.2 Neural Network Modeling ............................................................................. 375

15.2.1 Structure of ANN Model of a Dryer ................................................ 376

15.2.2 Training of ANN Model .................................................................. 377

15.3 Energy and Exergy Analysis of Drying Process ........................................... 378

15.3.1 Drying Efficiency ............................................................................. 378

15.3.2 Exergy Analysis through the Analysis of Second Law

of Thermodynamics ......................................................................... 378

15.3.3 Exergy Calculation for Dryer ........................................................... 379

15.4 Finite Element Modeling of Single Kernel ....................................................380

15.5 Computational Fluid Dynamics (CFD) Modeling ......................................... 385

15.5.1 CFD Model Formulation ................................................................. 385

15.5.1.1 Continuity Equation ........................................................386

15.5.1.2 Momentum Conservation Equations ............................... 386

15.5.1.3 Energy Conservation Equation ........................................ 386

15.5.1.4 User-Defined Function .....................................................386

15.5.2 CFD Analysis ................................................................................... 387

15.5.2.1 Preprocessing ................................................................... 387

15.5.2.2 Processing ........................................................................ 388

15.5.2.3 Post-processing ................................................................ 388

15.6 Optimal Design Using Genetic Algorithm ....................................................390

15.6.1 Optimal Design of Agro-Product Processing Systems ....................390

15.6.2 Genetic Algorithm ...........................................................................390

15.6.2.1 Basic Principles of Genetic Algorithm ............................ 391

15.6.2.2 Fitness Function ............................................................... 391

15.6.2.3 Genetic Algorithm Procedure for Optimal

Drying Parameters ........................................................... 391

Key to Symbols ........................................................................................................ 393

Bibliography ............................................................................................................. 394

Index ..............................................................................................................................................397

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