Moisture diffusivity and drying kinetic equation of convective drying of grapes

Mathematical modeling of drying process of unripe banana slices

“…As denoted by Azzouz et al (2002) the effective mass diffusivity varies with moisture content as a third order polynomial function, on the drying of grapes of two varieties, in this case the expression of the mass diffusivity of water is written under the following form:…”

“…The expression of the coefficient of water diffusion in grape proposed by Azzouz et al (2002) The authors concluded that the moisture diffusivity is nearly constant at high moisture content, but it decreases sharply as the moisture content decreases. The effect of the temperature is not obvious; the results of the proposed method are presented in Table 3.5.…”

“…6.20 both approaches show the same behavior, it is interesting to notice that both models present a deviation in the same moisture content (dimensionless) range which corresponds to the first 100 min of drying. The literature recommends incorporating the shrinkage phenomenon in the mathematical model considering porous materials (AZZOUZ et al, 2002;QUIROZ;HASSINI et al, 2007). Azzouz et al, (2002) in the study of the drying of grapes, two models of diffusion have been performed to evaluate the effective diffusivity, a simplified one based on Fick's law (analytical method) and a second one that takes account a variable diffusivity (numerical method).…”

“…The literature recommends incorporating the shrinkage phenomenon in the mathematical model considering porous materials (AZZOUZ et al, 2002;QUIROZ;HASSINI et al, 2007). Azzouz et al, (2002) in the study of the drying of grapes, two models of diffusion have been performed to evaluate the effective diffusivity, a simplified one based on Fick's law (analytical method) and a second one that takes account a variable diffusivity (numerical method). Results confirm that the utilization of the analytic method is not justified in the case of the grape which is strongly deformable; in fact, an important gap exists between the coefficient of diffusion identified by the numeric method and the one obtained analytically.…”

“…The drying of grapes performed by Azzouz et al, (2002) -KOURIS, 1996). In this study the expression of D e is written under a polynomial law.…”