Experimental and Numerical Investigation of Gypsum Calcination under Fire Exposure

• NCJ Number: 309924
• Author(s): Ethan A. Fowlie; Trevor Borth; Gregory E. Gorbett; Hayri Sezer; Shijin P. Kozhumal
• Date Published: May 2021
• Length: 11 pages
• Grant Number(s): 15PNIJ-23-GG-04204-RESS
• Agencies: NIJ-Sponsored
• Publication Type: Research (Applied/Empirical)
• Award: Experimental and numerical investigations for the development and validation of thermo-chemistry models and property databases for selected wall lining materials under fire exposure

Annotation

This study conducts an experimental and numerical investigation of gypsum calcination under fire exposure.

Abstract

This study compares experimental results of gypsum calcination to the results predicted by a one-dimensional unsteady computational model. Controlled laboratory-scale experiments are conducted with gypsum wallboard exposed to a uniform heat flux. During this exposure, the internal temperature profile is recorded using an array of 12 thermocouples, placed at different depths inside the gypsum board, and the depth of calcination is measured. This process is repeated for several different heat fluxes from a radiant burner placed at different distances from the gypsum board. The effects of heat flux and the duration of exposure on the depth of calcination are quantified. The transients in the internal temperature of the gypsum are coupled with the propagation of the dehydration front. The same constant heat flux is used as a boundary condition to predict the depth of calcination of the gypsum board using a validated in-house one-dimensional unsteady computational model that 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. As the species transport inside the porous gypsum board is extremely difficult to measure experimentally, the transport of water vapor has been analyzed numerically by considering the diffusion due to the concentration gradients, convection due to the pressure gradient, the water vapor generation during calcination, and its removal due to re-condensation. The internal temperature profile from the experiments is compared to the temperature profile predicted by the model. The percentage of dehydration predicted by the model is compared to the depth of calcination measured in the experiments. The nonlinearity in the propagation of dehydration front during gypsum calcination has been explored in the combined experimental and numerical study.