Preface

The transformation of a raw material in to a commodity or specialty product implies a series of steps in which the feedstock is subjected to physical and chemical changes. The stages in which only physical changes occur are known as unit operations, and may involve heat, mass, or both transport processes, as well as the presence of gaseous, liquid, or solid phases.

Drying operations have been widely employed in the industry to eliminate water from the process materials. Additionally, it also refers to the elimination of organic solvents and liquids from solids. It allows for the pretreatment of feedstocks with different moisture content, such as wet solids, gels, suspensions, and solutions, for their physical or chemical transformation. Drying processing also enables the post-treatment of products for their final presentation and packaging. In some industries, such as alimentary and pharmaceutical, drying is used as a preservation method of products since the enzymatic and microbial activity that causes undesirable chemical changes in organic matter is reduced with the decrease of water content.

From a process approach, the development of drying equipment requires the understanding and mathematical interpretation of the heat and mass transport phenomena for their proper design, construction, and operation, as well as an energy analysis that allows for the improvement of the process.

Under this scenario, *Current Drying Processes* presents recent advances in the development of drying operations for organic and inorganic materials dealing with the theoretical and experimental aspects of the most widely used technologies today, namely solar, convective, fluidized, and ultrasonic drying. The chapters present the elementary principles of each drying technology, such as energy transfer, hydrodynamics, and drying kinetics, as well as the importance of simulation and statistical methods for the analysis and improvement of the processes.

**II**

**Section 3**

*by Chang Peng and Saeed Moghaddam*

Novel Drying Technologies **109**

**Chapter 6 111**

The Study of Fabric Drying Using Direct-Contact Ultrasonic Vibration

**Israel Pala-Rosas** ESIQIE, Instituto Politécnico Nacional, México

Section 1

Solar Drying

**1**
