Shrinking core model for the reaction-diffusion problem in thermo-chemical heat storage

In this work, we develop a kinetic model to study the dehydration reaction of Li2SO4.H2O single particles involving interaction between the intrinsic chemical reaction and the bulk diffusion. The mathematical framework of the model is based on the shrinking core model. A variable-grid, finite-difference method with fully implicit formulation is used for solving the model. It is found that the Damkӧhler number 0 0 (k r ) / (D c ) Da  r e plays an important role in determining the nature of the diffusion/reaction dynamics. A very small Da value means that the overall reaction is controlled by the intrinsic chemical reaction at the interface, while a very large Da value means that the overall reaction is controlled by the diffusion of water through the product phase. Moreover, the numerical results of fractional conversion calculated in the model are in good agreement with the theoretical analysis under extreme cases in which either diffusion (large Da) or reaction (small Da) dominates the dehydration process. With consideration of numerical solutions at various Da values, it is concluded that both intrinsic reaction and mass diffusion are important in determining the reaction kinetics within a range of Da values between 0.1 and 10.