Drying of solids: The infinite slab condition

Fourier's second law was solved using convective boundary conditions withou t considering the shrinkage of the solid. The solutions for a finite and an infinite slab were compared to determine the dimensions for a slab to be c onsidered as infinite. The solutions obtained for Bi = 0.1 and Bi = 100 cor respond to heat and mass transfer-controlled processes, respectively, durin g drying. The results show that the finite slab cannot be considered as inf inite, even for R-2/R-1 > 20 The relative error obtained when the finite sl ab was assumed to be infinite was not significant for small Fourier numbers , but it increased as the Fourier number increased; errors were also higher for higher Blot numbers. When the numerical solution of a drying model was obtained for finite and infinite slabs, significant differences in drying kinetics and temperature evolution were observed.