The variable nature of Biot numbers in food drying

摘要

We will try to express our comments in the most concise way. Giner (2012) refuted our observation on the problem of representing the boundary condition to mass transfer equation in terms of ?p_v/?x, where p_v is the water vapor pressure and x is any spatial coordinate within a solid phase, by introducing the flux of a specie i (j_i) as function of chemical potential,j_i=Dc_1/RT ?μ/?x with μ_i= μ_(io) + RT In a_i (1) where D is the mass diffusivity, c_i denotes the concentration of species i,μ_i, is the chemical potential, R is the universal gas constant, T is the absolute temperature and a,- is the thermodynamic activity of specie i. Giner (2012) explained that because thermodynamic activity of water (a_w) can be approximated by p_v/p_s, the insertion of this definition in Eq.