Dielectric Properties of Agricultural Materials and their Applications

Stuart Nelson

• Publisher: Academic Press
• Year: 2015
• ISBN:
  9780128025451
• Topic: Physical Sciences
• Subtopic: Electromagnetism

Dielectric Properties of Agricultural Materials and Their Applications provides an understanding of the fundamental principles governing dielectric properties of materials, describes methods for measuring such properties, and discusses many applications explored for solving industry problems. The information in this reference stimulates new research for solving problems associated with production, handling, and processing of agricultural and food products. Anyone seeking a better understanding of dielectric properties of materials and application of radio-frequency and microwave electromagnetic energy for solution of problems in agriculture and related fields will find this an essential resource.

• Presents applications of dielectric properties for sensing moisture in grain and seed and the use of such properties in radio-frequency and microwave dielectric heating of agricultural materials
• Offers information for finding correlations between dielectric properties and quality attributes such as sweetness in melons, or other desired characteristics of agricultural products
• Identifies conditions for selective dielectric heating of materials such as insects in grain or biological organisms in soils
• Provides a solid understanding of dielectric properties and the variables that influence these properties

Chapter 1

Theory and Fundamental Principles

Dielectrics and dielectric properties of materials are defined, and the fundamental relationships of dielectric properties with electromagnetic energy are discussed. The dielectric constant and the dielectric loss factor are components of the complex relative permittivity, which is also explained. The dielectric constant is associated with the ability of a material to store energy in the electric field in the material, and the loss factor is associated with the ability of the material to absorb or dissipate energy, that is, to convert electric energy into heat energy. The variation in the dielectric properties of materials—with respect to the frequency of the fields to which they are subjected, the temperature of the materials, and the density of the materials—is discussed. Because water is an important component of agricultural materials, the dielectric behavior of water is included in the discussion.

Keywords

Density; dielectric constant; dielectric loss factor; dielectric properties; electromagnetic energy; frequency; permittivity; temperature

The dielectric properties of materials are those electrical characteristics that determine the interaction of materials with electric fields. In radio-frequency (RF) and microwave heating of foods, agricultural products, and other dielectric materials, it is the interaction of the materials with the electric field component of the electromagnetic waves that produces the desired heating effects (Nelson and Trabelsi, 2014). Strictly speaking, radio frequencies range from about 10 kHz to about 100 GHz. These are the frequencies practicable for radio transmission; they span that portion of the electromagnetic spectrum between the audio frequencies and the infrared region (IEEE, 1990). Thus, the RF range includes those frequencies used for microwave heating. However, because RF dielectric heating applications were developed first in the frequency range of about 3–40 MHz, and microwave heating applications came later, there is a tendency—particularly in the food industry—to refer to the lower frequency applications as RF dielectric heating, and to refer to dielectric heating at microwave frequencies, about 1 GHz and higher, as microwave heating. Fr...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Foreword
• Preface
• Acknowledgments
• Chapter 1. Theory and Fundamental Principles
• Chapter 2. Measurement of Dielectric Properties
• Chapter 3. General Agricultural Applications
• Chapter 4. Insect Control Applications
• Chapter 5. Seed Treatment Applications
• Chapter 6. Product Conditioning Applications
• Chapter 7. Grain and Seed Moisture Sensing Applications
• Chapter 8. Assessment of Soil Treatment for Pest Control
• Chapter 9. Quality Sensing in Fruits and Vegetables
• Chapter 10. Mining Applications
• Chapter 11. Dielectric Properties of Selected Food Materials
• Chapter 12. Sensing Moisture and Density of Solid Biofuels
• Chapter 13. Dielectric Properties Models for Grain and Seed
• Chapter 14. Development of Microwave Moisture-Sensing Instrumentation
• Chapter 15. Dielectric Properties Data
• Chapter 16. Closely Related Physical Properties Data for Grain and Seed
• Index