Numerical investigation of gypsum board calcination under uniform heat flux

A comprehensive one-dimensional unsteady computational model is developed to solve the mass, species, momentum, and energy conservation equations assuming local thermodynamic equilibrium in the homogeneous porous material. The endothermic dehydration of chemically bound water in calcium sulfate dihydrate, and variable thermo-physical properties are considered in the present model. The mass transfer of water vapor due to the diffusion and pressure gradients, caused by the increased vapor concentration during the evaporation, are calculated using Fick's Law and Darcy's law respectively. The governing equations are discretized using a cell centered finite volume method. An implicit scheme is used for the time integration. The numerical model is validated by comparing the predictions with the experimental measurements from the available literature. The process of calcination is analyzed for different heat flux, duration of exposure, and surface temperature. The evolution of temperature profile and the movement of the dehydration front inside the gypsum board are analyzed. The dehydration process significantly influences the temperature profile inside the gypsum plasterboard. Also, the water vapor released due to the dehydration influences the heat transfer through the porous material. The effects of the heat flux and the duration of exposure on the gypsum board calcination are explored.