International Scientific Journal
NUMERICAL STUDY ON HYGROSCOPIC CAPILLARY-POROUS MATERIAL DRYING IN A PACKED BED
During the non-hygroscopic and/or hygroscopic capillary-porous materials drying the first part of the drying curve has the similar form. In the case of the hygroscopic capillary-porous material drying, the drying rate
drops more sharply as deep inside the material the sorption state is ensured, i. e. when the partial pressure of water vapor at this place becomes less than the partial pressure of free water. This drying period
disappears at the moment when all the material layer is in the hygroscopic regime (the second critical point appears). Results of modeling and numerical simulation for the case of the hygroscopic capillary-porous material drying
in a packed bed are shown in the paper. A mathematical model describing unsteady simultaneous one-dimensional heat and mass transfer between gas phase and dried material during drying process in a packed bed is described.
Heat and mass transfer between solid phase and gas phase takes place at the surface of the solids (assuming the state of thermodynamic equilibrium). Heat transfer (temperature gradient) inside the dried material is neglected.
Mass transfer coefficients inside dried material are defined based on experimental investigation of drying kinetics for an elementary packed bed of a given material, thus enabling better results in the drying rate evaluation for the
case of the great number of real (colloidal capillary-porous) materials. Verification of the model was done successfully on the basis of the available experimental data for the hygroscopic capillary-porous material (potato cubes) drying. Numerical analysis of the influence that relevant parameters have onto the drying process in the case of potato cubes (4.0 mm, 8.0 mm and 12.0 mm) was carried out and shown in this paper.
PAPER SUBMITTED: 2001-01-12
PAPER REVISED: 2001-05-03
PAPER ACCEPTED: 2001-05-07
PUBLISHED ONLINE: 2020-08-22
, VOLUME 4
, ISSUE Issue 2
, PAGES [89 - 100]