ISSN:0737-3937    

DOI:10.1080/07373939108916745

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The aim of this paper is to summarize ten years of work in order to model the drying of solids. Nowadays there is a general agreement amongst the various researchers worldwide. If the porous medium is viewed at the so-called “macroscopic” scale (that is to say when it is viewed as a continuous and homogeneous equivalent medium) a set of three partial derivative equations is derived, three state variables being necessary to thermodynamically describe the medium (temperature, moisture content and total pressure in the gaseous phase for example).

ISSN:0737-3937    

DOI:10.1080/07373939108916746

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

From the mathematical formulation presented in part I, a numerical code is developed to simulate heat and: mass transfers in porous media. The aim of this· tool is to understand and to improve each process related to drying. The association of a comprehensive set of equations with a efficient 2-D computer code allows us to predict the comportment of several porous media even if submitted to severe drying conditions. A few runs have been selected with special attention paid to the effect of internal gaseous pressure:

ISSN:0737-3937    

DOI:10.1080/07373939108916747

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

TThis paper is essentially devoted to the study of the interfacial coefficient problem and to a characterization of the falling rate period.By means of a 2D numerical simulation, it is shown that the falling rate period is characterized by strong humidity heterogeneities at the interface. These heterogeneities affect significantly the interfacial mass transfer coefficient to be used in the traditional ID approach of drying. In this paper. the heterogeneities are due to the coupling between external and internal transfer in a boundary layer flow leading edge region.0ther phenomena that may also cause the occurence of humidity heterogeneities at the interface are discussed.

ISSN:0737-3937    

DOI:10.1080/07373939108916748

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A model is formulated to describe the drying of a slab of porous material in a combined microwave and convective environment. The model describes the evolution of temperature, pressure, moisture and power distributions that occur during the drying process. The microwave internal heat source is calculated from electromagnetic theory with varying dielectric properties. The inclusion of pressure in the model allows the physical phenomena of “water pumping”, often observed in microwave drying systems, to be accounted for. The influence of sample size; on the drying kinetics 1s examined and found to be an important parameter during the drying process. In particular the effect of resonance on the moisture and temperature profiles and the need for careful consideration of surface mass transfer coefficients are investigated. Simulation results are presented for the combined microwave and convective drying of a homogeneous, isotropic porous material.

ISSN:0737-3937    

DOI:10.1080/07373939108916749

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

An attempt is proposed to modelize the coupling effects between heat transport, mass transport and solid shrinkage during the drying of like gels products.

ISSN:0737-3937    

DOI:10.1080/07373939108916750

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The process of drying parallelepipedic samples of wood is studied, by considering 3-dimensional transport of water along the 3 principal axes of diffusion, as well as evaporation out of the surface. During a large part of the process, the water content is considerably higher than the value associated with the fiber saturation point. A numerical model with finite differences, based on the assumption that the transport of water is controlled by transient diffusion through the sample and evaporation from the surface, is successfully tested with a beam in the following two cases : the initial concentration of water is uniform, or not. The model is capable of predicting not only the kinetics of drying, but also the profiles of concentration developed through the samples at various times. The principal diffusivities are determined by using a short test technique in transient condition.

ISSN:0737-3937    

DOI:10.1080/07373939108916751

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373939108916752

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373939108916753

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373939108916754

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor