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Mathematical model of steam drying of wood chips and other hygroscopic porous media
Author(s) -
Fyhr Christian,
Rasmuson Anders
Publication year - 1996
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690420909
Subject(s) - superheated steam , wood drying , mass transfer , water content , condensation , moisture , materials science , porous medium , heat transfer , porosity , vapour pressure of water , thermodynamics , water vapor , composite material , chemistry , superheating , chromatography , geotechnical engineering , physics , organic chemistry , engineering
A model is presented that is focused on the drying kinetics of single wood chips as a function of time and external conditions, such as temperature, pressure and velocity of the superheated steam. A multiphase and 2‐D approach was used to model the coupled transport of water, vapor, air and heat in anisotropic hygroscopic porous media. The model was verified by drying experiments where measurements of the average moisture content, center temperature and pressure in a single wood chip could be performed simultaneously. A comparison between the calculations and the measurements showed that the drying behavior was well predicted. The drying can be divided into three stages: a heat‐up period when condensation on the surface initially increases the moisture content; a period of constant drying rate when the external heat transfer controls the drying rate; and a period of decreasing drying rate when the drying is controlled by internal mass transfer. Many interesting features of the drying could be assigned to the strong anisotropicity of wood, which makes a 2‐D model necessary.