摘要:

A numerical simulation is described for solving the thermal conduction and mass diffusion equations in boards of hardwood timber, and the Einite-volume method used here has been applied to the drying of Eucalypt timber, an Australian hardwood. The predictions of the variation in the average moisture content with time agree well with both ex~erimental data from the literature and analvtical solutions of the-diffusion equation. The nume ical simulation treats the boundary conditions more accurately than the analytical solutions when the moisture movement is two dimensional, as it is through the cross-section of a timber board. This feature makes the simulation useful when describing the drying process under intermittent drying conditions. These conditions are encountered in the drying of timber in solar kilns, and this simulation may be used to predict the distributions of temperature andmoisture content inboards of timber which are being dried intermittently inside conventional kilns. The numerical simulation for intermittent drying has shown, inthe example studied here, chat the same overall change in average moisture concentration can be achieved with 12-hour active drying and 12-hour relaxationperiodaas forcontinuousdryingbyincreasingthedry-bulb temperature by 10°C for this timber. In spite of the higher dry-bulb temperature used in the active drying period of intermittent drying. the moisture concentration profiles within the board are predicted to be more uniform than with continuous drying, because the internal moisture diffusion process continues during the relaxation period. These mare uniform moisture concentration profiles in intermittent drying are likely to result in lower stress levels within the timber than with continuous drying.

ISSN:0737-3937    

DOI:10.1080/07373939508916983

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The presenr paper is to study the transient deformation characteristics of molded ceramics undergoing nonunifom drying. The linear viscoelasticity was assumed for the strain-stress analysis. Three dimensional equations of the strain-stress as well as heat and moisture transfer werc solved numerically by the Galerkln finlle element melhod using isoparametric parameters of twenty-nodes so to allow easily the application to any feature of ceramics. Both the analysis and experiments were carried out to be compared on the behavior of drying and deformation for a slab clay in preheating and constant drying rare periods. When the bottom surface of the slab uras shielded to model the nonuniform drying. a warp phenomrnon to the opposite side of the shielded surface was observed experimentally as drying by hot air heating proceeds. The behavior could be successively simulaled by the present theoretical model. The degree of warp became rcmarkabel with a rise in air temperature or nonuniformity of drying. The surface area exposed to the atmosphere was subjected to a comparatively large tensional stress through drying. The tensile sltresses on the top surface were significantly larger than on the bottom surface.

ISSN:0737-3937    

DOI:10.1080/07373939508916984

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373939508916985

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373939508916986

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In designing cascading rotary dryers, it is important to sire the flights correctly in order to ensure....

ISSN:0737-3937    

DOI:10.1080/07373939508916987

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373939508902368

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor