Tobacco Science & Technology, 2009, 11, p. 5-10, ISSN.1002-0861
Dynamics analysis of multiple heat transfer impacts on intensive mass transfer during thin layer drying processing of cut tobacco
In order to find out the influences of multiple heat transfer process on cut tobacco drying, the effects of hot air temperature (60°-100°) and thin plate temperature (50°-90°) on the drying kinetics of three kinds of cut tobacco were investigated in a fixed bed at constant air velocity. The apparent activation energies ( Ea ) of tobacco shreds from Enshi tobacco, Yibin tobacco and Brazil tobacco were obtained by Fick's second law and Arrhenius formula. They were 8.31kJ/mol, 12.11kJ/mol and 21.13kJ/mol, respectively. The model of the relationship between effective diffusion coefficient of tobacco shreds and thin plate temperature was established with dimensionless analysis method, and the exponential terms in the dimensionless relation might be explained physically as intensified factors of thin plate temperature, which reflected the intensified effect of thin plate temperature on mass transfer to tobacco shreds, and the intensified factors for the three tobacco shreds were: Enshi, 10.08; Yibin, 12.21; Brazil, 10.82. The results showed that the established model can characterize the effect of conductive heat transfer on drying kinetic parameters of tobacco shreds.