In this study, researchers use a 3D mathematical model to examine heat and mass transfer mechanisms in gypsum board exposed to fire.
This study investigates the influence of linearly varying surface heat flux on the depth of dehydration of the gypsum board. An in-house three-dimensional mathematical model based on the finite volume method was developed to consider the three-dimensional nature of the dehydration phenomenon of gypsum board exposed to fire. The three-dimensional transient computational model solves the mass, species, momentum, and energy conservation equations assuming local thermodynamic equilibrium. The dehydration of the gypsum board, coupled with the heat and mass transport through it, has been modeled by considering the gypsum board as a homogeneous porous material. The model is capable of predicting the depth of calcination, internal temperatures, species transport of water vapor and air, and degree of dehydration of gypsum boards exposed to varying heat fluxes. The rate of dehydration during calcination varies with the surface heat flux on the gypsum board causing lateral gradients inside the gypsum board when exposed to non-uniform heat flux. The temperatures and vapor pressure inside the porous gypsum board and its degree of dehydration have been analyzed during the dehydration process. The effect of three-dimensionality in the dehydration process has been quantified by comparing the numerical predictions when subjected to controlled non-uniform heat fluxes and different uniform heat fluxes within that range. When exposed to fire, gypsum wallboard (drywall) experiences calcination. In forensic fire investigations, a quantitative study of the depth of calcination caused by a fire is quite useful. The heat and mass transfer brought on by the incident heat flux determines the rate and depth of calcination through the board. (Published Abstract Provided)