Thermomechanics of Drying Processes

by Kowalski, Stefan Jan

• ISBN13: 9783540004127
• ISBN10: 3540004122
• Format: Hardcover
• Copyright: 2003-05-01
• Publisher: Springer Verlag

Summary

This book presents a systematic thermomechanical theory of drying. The book has an interdisciplinary character and combines the knowledge of Chemical Engineering and Mechanics of Continua. It contents a unified approach to the heat and mass transfer in drying processes as well as a precise analysis of all local drying effects. Methods for the improvement of quality of dried products and optimization of drying processes with respect to the strength of materials and drying time are presented. The book also presents the theory for fully coupled multiphase transport in deformable capillary porous media as well as computer simulations of drying processes. Finally the acoustic emission method is described as an experimental way of identification of material fractures during drying.

Table of Contents

Foreword	5	(3)
Preface	8	(3)
Contents	11	(2)
Nomenclature	13	(5)
Properties of dried materials
Classification of wet materials	18	(1)
Characterization of moisture bounding a solid skeleton	19	(1)
The equilibrium humidity	20	(2)
Mechanisms of moisture movement	22	(2)
Characterization of drying processes
Drying technique	24	(2)
Kinetics of drying processes	26	(2)
Mechanisms of heat and mass transfer	28	(3)
The equations of balance
Preliminaries	31	(3)
Balance equations: control volume approach	34	(10)
Second law of thermodynamics	44	(2)
Thermodynamic foundation of dried materials in elastic range
Postulate of local state	46	(1)
Equations of state	47	(9)
Phenomenological rate equations of heat and mass transfer	56	(12)
Physical relations for elastic materials under drying	68	(12)
Thermodynamics of viscoelastic materials under drying
Rheological properties of dried materials	80	(2)
Constitutive equations for a viscoelastic body	82	(8)
Analogy between viscoelasticity and elasticity	90	(6)
Plasticity in drying
Elastoplastic behavior of dried materials	96	(1)
Thermodynamical restrictions	97	(1)
Theory of plastic flow	98	(4)
Identification of the coefficients α and L in the plastic potential	102	(14)
Destruction of materials by drying
Preliminary remarks	116	(1)
Cohesion forces in drying processes	117	(3)
Theoretical strength of dried materials	120	(6)
Fracture of brittle dried materials	126	(5)
Fracture of partly ductile dried materials	131	(3)
A measure of damage	134	(3)
Conditions of stress generation and boundary conditions
Conditions of stress generation	137	(2)
Balance equations for a body with a discontinuity surface	139	(6)
Boundary conditions in the first and second period of drying	145	(9)
Receding of the evaporation zone	154	(3)
Approach to numerical analysis in drying
Set of governing equations	157	(4)
Galerkin's formulation of the numerical problem	161	(7)
Time integration	168	(4)
Numerical solution for two-dimensional problem	172	(18)
One-dimensional initial-boundary value problem
Distribution of temperature and moisture content in wet porous plates under drying	190	(8)
Drying induced stresses in an elastic saturated plate	198	(10)
Drying induced stresses in a viscoelastic saturated plate	208	(12)
Drying induced stresses in products of cylindrical and spherical symmetry
The phenomenon of stress reverse in a cylindrical sample	220	(17)
Determination of shrinkage factor on a spherical sample	237	(12)
Mechanical effects in dried materials examined on the basis of two-dimensional boundary value problems
Deformations and stresses dependent on material shape	249	(6)
Thermal effects in dried materials	255	(5)
Analysis of dried body response on drying conditions the response of dried body to drying conditions	260	(8)
Significance of the wet bulb temperature in drying	268	(8)
Control of drying processes	276	(6)
Mechanical properties dependent on moisture content	282	(3)
Concentration of stresses around grooves	285	(3)
Phase transition inside the dried body	288	(4)
Dried materials with anisotropic structure
Constitutive equations for anisotropic materials with variable moisture content	292	(4)
Experimental identification of mechano-sorptive strain in wood	296	(3)
Deformation and stresses in dried wood	299	(8)
Identification of wood fracture during drying	307	(20)
Experimental studies in drying
Determination of coefficients in physical relations	327	(8)
Determination of coefficients in rate equations	335	(7)
Application of acoustic emission in studies of dried materials	342	(13)
Index	355	(4)
References	359