The effect of biological material´s tissue shrinking on moisture diffusivity during Hot-air-drying

In this study, a mathematical model is developed to determine the local moisture diffusion coefficient during the drying process. The mathematical model´s theoretical basis is as follows: the volume of the sample reduces, with water loss of the biological porous material. The dimensions (sample´s length, width and thickness) shrinkage accompany with the volume reduction. The dimensions´ shrinkage results in cross section area decrease. For example, x direction´s length shrinkage makes y direction´s and z direction´s cross section area less; y direction´s length shrinkage leads to z direction´s and x direction´s cross section area less; and z direction´s length reduction changes x direction´s and y direction´s cross section area less. The cross section area less causes the pore area less and thus reducing water moisture diffusion ability. The moisture diffusivity is assumed to be proportional to pore area. Based on this theory, banana´s local moisture diffusivity has been calculated and the results show the local diffusivity is reasonable.