MODELING OF HEAT-TRANSFER, GAS-FLOW AND S TRESS IN POROUS MATERIAL WITH THERMAL-DECOMPOSITION

The governing equations of heat transfer and gas flow within a cylindr ical porous material which causes thermal decomposition are simplified to derive approximate models for evaluating the inner gas pressure an d the effort of the convection heat transfer, respectively. The combin ation of these models with the existing previous stress model gives a model for not only evaluating the thermal stress but also stress due t o gas pressure. The models are adapted for a green carbon rod during c arbonization. The numerical results reveal the following useful facts: 1) Both the gas pressure and the stress due to the gas pressure appro ximately increase in proportion to specimen diameter and the square ro ot of heating rate. 2) The releases of gaseous tar and H-2 promote the convection heat transfer rate within the specimen because they change the thermophysical properties of the gas phase as well as increase th e gas Row rate. 3) The release of H-2 essentially raises the gas press ure and the stress due to the gas pressure and moreover has a particul arly strong influence on the overall-stress peak at about 1000 K.