Drying Model With Non-Isotropic Shrinkage Deformation Undergoing Simultaneous Heat and Mass Transfer

Modelling and simulation of pear drying

“…Among the various theoretical models proposed in literature for the drying of foods, the diffusion models that describe the non-steady state transfer according to Fick's second law, are the most common [1,21]. In the present work a diffusion model is also proposed to describe the drying of pears, which accounts for shrinkage and for the variation of the transfer properties along drying.…”

“…In the above model, the shrinkage effect is included in the variable q sh , since it relates the mass of dry solids to the total volume of moist material, which varies along drying [21].…”

“…where, D W is the effective diffusivity, q sh is the dry solids concentration (defined as the mass of dry solids divided by total volume), T s (t) is the surface temperature at R À max , T a (t) is the surface temperature at R þ max , W s (t) is the surface moisture at R À max and W e (t) is the surface moisture at R þ max , given by the sorption isotherms [19,21].…”

“…The model is composed of two partial differential equations, accounting for the variations of temperature (T) and dry basis moisture content (W) [9,12,13,21] oT ðr;tÞ ot…”

“…For the heat transfer coefficient, it was adopted the same relationship used by Yang, Sakai and Watanabe for the drying of potato [21] Nu ¼ 0:023ðReÞ 0:8 ðPrÞ 0:4 ; ð8Þ…”