Direct numerical simulation of the thermal dehydration reaction in a TGA experiment

Abstract

This work presents a detailed mathematical model of the coupled mass and heat transfer processes in salt hydrate grains in a TGA experiment. The purpose of developing this numerical model is to get a more fundamental understanding of the influence of parameters like particle size, nucleation rate and vapor pressure on the dehydration reaction in a TGA experiment. Such a model needs a detailed description of the fluid flow and water vapor distribution between the particles. The dehydration reaction of grains of TCMs is described by the nucleation and nuclei growth model presented in our earlier work. The flow around grains is solved by means of the finite volume method using OpenFOAM including heat and mass transfer. Direct numerical simulations of TGA-experiments under various conditions are performed. Such simulations provide direct insight into the physics of mass and heat transport processes coupled with detailed reaction kinetics at grain scale. The numerical results are compared to the experimental results. The developed CFD model can be a promising tool to calculate the overall kinetics for dehydration reactions under realistic heat storage conditions. To that end, the effect of buoyancy should also be included in the model to get a more accurate description of convection within the sample.