Drying and Storage of Cereal Grains

Finite Element Analysis and Computational Fluid Dynamics have been introduced in modelling and simulation of drying and storage systems, these techniques are expected to dominate the future research and development of drying and storages, and should reduce losses and improve the quality of agricultural products, enhancing food security globally.

Drying and Storage of Cereal Grains, Second Edition, covers the wide spectrum of drying and storage methods applied to economically important cereal produce, providingnumerical examples for better understanding the complexity in drying and storage systems through modelling and simulation, aiding design and management of drying and storage systems. Chapters 1 to 8 look at air and grain moisture equilibria, psychrometry, physical and thermal properties of cereal grains, principles of air flow, and provide detailed analyses of grain drying.Chapters 9 to 13 focus on temperature and moisture in grain storages, and provide comprehensive treatment of modern grain storage systems. The book also includes a number of unsolved problems at the end of each chapter for further practice.

This revised second edition includes new sections on -

• heat of sorption
• finite element modeling of single kernel
• CFD modeling  of fluidized bed drying
• exergy analysis and neural network modeling
• numerical solution of two dimensional temperature and moisture  changes in stored grain

This book will provide students in agricultural engineering and food engineering with a wide spectrum of drying and storage studies previously unavailable in a single monograph. It will also serve as an excellent reference for practicing agricultural engineers, food engineers and food technologists.

B K Bala, Department of Agro Product Processing Technology, Jessore University of Science and Technology, Bangladesh.

Foreword to the first edition iii

Foreword to the second edition iv

Chapter 1: Principles of Drying 1

1.1 Introduction 1

1.2 Losses of Crops 2

1.3 Importance of Drying 3

1.4 Principles of Drying 4

Chapter 2: Moisture Contents and Equilibrium Moisture

Content Models 6

2.1 Introduction 6

2.2 Moisture Content Representation 6

2.3 Determination of Moisture Content 10

2.4 Grain Sampling 17

2.5 Equilibrium Moisture Content 18

2.6 Determination of Static Equilibrium Moisture Content 23

2.7 Static Equilibrium Moisture Content Models 27

2.8 Net Isosteric Heat of Sorption 30

Chapter 3: Psychrometry 43

3.1 Introduction 43

3.2 Psychrometric Terms 44

3.2.1 Humidity Ratio 44

3.2.2 Relative Humidity 45

3.2.3 Specific Volume 45

3.2.4 Vapour Pressure 46

3.2.5 Dry Bulb Temperature 46

3.2.6 Dew Point Temperature 46

3.2.7 Wet Bulb Temperature 46

3.2.8 Enthalpy 47

3.2.9 Adiabatic Wet Bulb Temperature 48

3.2.10 Psychrometric Wet Bulb Temperature 51

3.3 Construction of Psychrometric Chart 53

3.4 Use of Pschrometric Chart 54

3.4.1 Sensible Heating and Cooling 55

3.4.2 Heating with Humidification 56

3.4.3 Cooling with Humidification 57

3.4.4 Cooling with Dehumidification 57

3.4.5 Drying 59

3.4.6 Mixing of Air Streams 61

3.4.7 Heat Addition with Air Mixing 64

3.4.8 Drying with Recirculation 65

Chapter 4: Physical and Thermal Properties of Cereal Grains 78

4.1 Introduction 78

4.2 Structure of Cereal Grains 78

4.3 Physical Dimensions 80

4.4 1000 Grain Weight 80

4.5 Bulk Density 81

4.6 Shrinkage 81

4.7 Friction 83

4.8 Specific Heat 87

4.9 Thermal Conductivity 90

4.10 Latent Heat of Vaporization of Grain Moisture 95

4.11 Heat Transfer Coefficient of Grain Bed 99

Chapter 5: Air Flow Resistance and Fans 116

5.1 Air Flow Resistance 116

5.1.1 Non-Linear Air Flow Analysis 118

5.2 Fans 128

5.2.1 Fan Performance 131

5.2.2 Centrifugal Fan Laws 137

5.2.3 Fan Selection 137

5.2.4 Effect of Change in Fan Speed 138

5.2.5 Effect of Change in Speed and System Resistance 139

5.2.6 Fans in Series and Parallel 140

5.3 Duct Design for On-Floor Drying and Storage System 144

Chapter 6: Thin Layer Drying of Cereal Grains 150

6.1 Theory 150

6.2 Thin Layer Drying Equations 153

6.2.1 Empirical Drying Equations 154

6.2.2 Theoretical Drying Equations 155

6.2.3 Semi-theoretical Drying Equations 159

6.3 Development of Thin Layer Drying Equations 164

6.3.1 Drying Rate 167

6.4 Drying Parameters 167

6.4.1 Drying Rate Constant and Diffusion Coefficient 169

6.4.2 Dynamic Equilibrium Moisture Content 178

6.5 Finite Element Modeling of Single Kernel Drying 185

6.5.1 Finite Element Model Formulation 186

6.5.2 Finite Difference Solution in Time 192

6.5.3 Discretization of the Domain 193

Chapter 7: Deep Bed and Continuous Flow Drying 205

7.1 Introduction 205

7.2 Deep Bed Drying Models 205

7.2.1 Logarithmic Models 206

7.2.2 Partial Differential Equation Models 206

7.2.3 Comparison of Deep Bed Drying Models 208

7.3 Development of Models for Deep Bed Drying 209

7.3.1 Logarithmic Model 209

7.3.2 Partial Differential Equation Model 217

7.3.3 Method of Solution 222

7.3.4 Condensation Procedure 224

7.3.5 Sensitivity Analysis 233

7.3.6 Comparison of Simulated Drying with Experimental Results 233

7.3.7 Comparison of Direct, Indirect and Recirculating Direct Fired Drying 235

7.4 Development of Models for Continuous Flow Drying 237

7.4.1 Cross Flow Model 238

7.4.2. Fluidized Bed Drying Model 246

7.5 CFD Modeling of Fluidized Bed Drying 253

7.5.1Continuity equation 254

7.5.2 Momentum conservation equations 255

7.5.3 Energy conservation equation 256

7.5.4 User-Defined Scheme (UDS) 256

7.5.5 CFD Analysis 256

Chapter 8: Grain Drying Systems 270

8.1 Introduction 270

8.2 Solar Drying Systems 270

8.3 Batch Drying Systems 275

8.4 Continuous Flow Drying Systems 277

8.5 Safe Temperature for Drying Grain 280

8.6 Hydro-Thermal Stresses during Drying 281

8.7 Energy and Exergy Analysis 283

8.8 Neural Network Modeling 286

8.8.1 Structure of ANN model 287

8.8.2 Training of ANN model 288

8.9 Selection of Dryers 290

Chapter 9: Principles of Storage 297

9.1 Introduction 297

9.2 Principles of Storage 298

9.3 Interrelations of Physical, Chemical and Biological Variables in the Deterioration of Stored Grains 301

9.4 Computer Simulation Modelling for Stored Grain Pest Management 303

Chapter 10: Temperature and Moisture Changes during Storage 307

10.1 Introduction 307

10.2 Qualitative Analysis of Moisture Changes of Stored Grains in Cylindrical Bins 307

10.3 Temperature Changes in Stored Grains 309

10.4 Temperature Prediction 311

10.4.1 The Differential Equation of Heat Conduction in Cylindrical Co-Ordinate System 311

10.4.2 Numerical Method 313

10.5 Numerical Solution of one-dimensional heat flow 313

10.6 Numerical Solution of two-dimensional heat flow and Moisture Flow 320

10.6.1 Heat Transfer The Differential Equation of Heat Conduction in Cylindrical Co-Ordinate System 311

10.4.2 Numerical Method 313

10.7 Simultaneous Momentum, Heat and Mass Transfer 340

10.7.1 The Energy Balance Equation 341

10.7.2 The Mass Balance Equation 341

10.7.3 The Momentum Balance Equation 342

10.4.4 Finite Difference Formulation 343

10.8 CFD Modelling of Grain Storage Systems 350

10.8.1 Continuity Equation 351

10.8.2 Momentum Conservation Equation 351

10.8.3 Energy Conservation Equation 351

10.4.4 User Defined Function 353

Chapter 11: Fungi, Insects and Other Organisms Associated with Stored Grain 358

11.1 Introduction 358

11.2 Fungi 359

11.2.1 Field Fungi 361

11.2.2 Intermediate Fungi 361

11.2.3 Storage Fungi 361

11.3 Insects 364

11.3.1 Insect Species 365

11.3.2 Grain Temperature and Moisture Content 366

11.4 Mites 367

11.5 Rodents 367

11.6 Respiration and Heating 369

11.7 Control Methods 371

Chapter 12: Design of Grain Storages 373

12.1 Introduction 373

12.2 Structural Requirements 373

12.2.1 Janssen’s Equation 374

12.2.2 Rankine’s Equation 377

12.2.3 Airy’s Equation 379

12.3 Construction Materials 256

Chapter 13: Grain Storage Systems 394

13.1 Introduction 394

13.2 Traditional Storage Systems 395

13.3 Modern Storage Systems 395

13.3.1 Bagged Storage Systems 396

13.3.2 Silo Storage Systems 396

13.3.3 Airtight Grain Storage 398

13.3.4 Aerated Storage Systems 406

13.3.5 Low Temperature Storage System (Grain Chilling by Refrigeration) 412

13.3.6 Controlled Atmosphere Storage Systems 416

13.3.6 Damp Grain Storage Systems 420

Appendix - A Finite Difference Approximation 434

Appendix - B Gaussian Elimination Method 436

Appendix - C Finite Element Method 438

Appendix - D Computational Fluid Dynamics 441

Index

The New copy of this book will include any supplemental materials advertised. Please check the title of the book to determine if it should include any access cards, study guides, lab manuals, CDs, etc.

The Used, Rental and eBook copies of this book are not guaranteed to include any supplemental materials. Typically, only the book itself is included. This is true even if the title states it includes any access cards, study guides, lab manuals, CDs, etc.