Numerical solution of the three-dimensional diffusion equation in leaching processes

A mathematical model is presented to account for the leaching of a solute during the heating of a parallelepiped solid with the diffusion coefficient being a function of temperature. The alternating direction implicit method developed by Douglas and Brian was chosen to solve the resulting equations. Details of the finite difference scheme are given with special reference to the variable diffusion coefficient and the third kind boundary condition. The model was applied to predict the retention of water soluble vitamins during the blanching of potato parallelepipeds.