摘要:

A two-dimensional finite element model of isothermal wood drying based on the waterpotential concept is presented. An original algorithm iS used to update moisture content and water potential during the computations. The moisture content water potential relationship and the effective water Conductivty functions obtained during independent experiments are used as model parameters. In order to assess the possibilities and limitations of this approach. the calculated drying curves and moisture content profiles are compared to results obtained during convective drying of aspen sapwood at 20, 35, and 50°C, from full saturation to a final moisture content of about 10 %. The experimental and calculated results are in reasonable agreement although differences are observed at intermediate drying times. These differences could be attributed to the description of the convective boundary condition or to possible thermal effects.

ISSN:0737-3937    

DOI:10.1080/07373939208916511

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Energy consumption was quantified in the drying of 2.5 cm thick red oak lumber ina 1.2 m3steam heated experimental dry kiln. The aluminum pre-fab kiln is located indoors and was wrapped with 5 cm thick extruded polystyrene (R=10) for the experimental drying. Transmission loss accounted for about 80% of the energy/kilogram of water removed from the wood. The maximum value was for the 60°C DBT due to comparatively high transmission loss combined with maximum venting loss. Batch venting reduced average energy consumption per kiln run by over 6% compared to the conventional kiln schedule.

ISSN:0737-3937    

DOI:10.1080/07373939208916512

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Since the only measured value that is derived from the wood for controlling the kiln drying process is the mean moisture content, it is essential to develop new techniques for the measurement of additional process parameters. When the drying rate, which could be such an additional parameter, is seen in conjunction with other process variables, conclusions on the instantaneous drying behaviour of the wood are possible. A simple and practical way for determining the drying rate is based on the relationship between the drying rate and the heat-flux for evaporation. A measurement of the heat-flux by means of a heat-flux sensor allows the calculation of the drying rate.

ISSN:0737-3937    

DOI:10.1080/07373939208916513

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Infrared thermography is used to visualize moisture evaporation from wooden surfaces. The initial moisture flux is shown to be dependent upon the growth ring structure as well as the heartwood and sapwood portions of a board.

ISSN:0737-3937    

DOI:10.1080/07373939208916514

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The computer tomography(CT image of wood was analyzed to estimate the moisturecontent from CT number. Comparing moisture contents, densities and CT numbers, moisture distributions were nondestructively determined by CT numbers detected with the scanner.

ISSN:0737-3937    

DOI:10.1080/07373939208916515

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The mechanism for the induction of liquid tension which caused cell collapse was investigated using water saturated Balsa wood. We determined that the water-tightness of cell wall and free water without fine bubbles were necessary to induce large liquid tension in lumina. After cell collapse reached a maximum limit, part of the deformation of cells recovered upon the removal of liquid tension. True collapse intensity, which did not allow recovery, was obtained at ambient pressures above 7 kgf/cm2. Cells which had air eliminated from their lumina were depressed by hydrostatic compressed air. This deformation was similar to that of collapse in drying. We estimated that the maximum value of liquid tension induced in cell lumina of Balsa wood was 13–14 kgf/cm2

ISSN:0737-3937    

DOI:10.1080/07373939208916516

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The objective of this work is to investigate some of the important aspects in the design of a steam band dryer for wood fuels. For this purpose the drying of the material in a bench-scale fixed bed dryer has been studied.

ISSN:0737-3937    

DOI:10.1080/07373939208916517

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Depending on the temperature, moisture of the surrounding atmosphere may condensate or not. A piece of wood may thus be in contact either with liquid water during the night for a given time, or with air during daylight at a given relative humidity. A sorption-desorption history of moisture may thus occur, with a moisture content in the wood which may vary to a high extent below or beyond the fiber saturation point. A model based on a finite difference model is able to describe the process : the kinetics of the sorption-desorption history is in good agreement with the experiments ; moreover, a fuller insight into the nature of the process is gained with the profiles of moisture content in various places of the wood sample.

ISSN:0737-3937    

DOI:10.1080/07373939208916518

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373939208916519

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0737-3937    

DOI:10.1080/07373939208916520

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor