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A transient two-dimensional model of thermal and oxidative degradation of pmma | ||
| Iranian Journal of Science and Technology Transactions of Mechanical Engineering | ||
| شناسنامه علمی شماره، دوره 29، شماره 2، اردیبهشت 2005، صفحه 207-218 | ||
| شناسه دیجیتال (DOI): 10.22099/ijstm.2013.1019 | ||
| چکیده | ||
| In the present work, numerical computations of the flow and thermal fields have been carried out for a transient, two-dimensional model of thermal and oxidative degradation of polymethylmethacrylate (PMMA) subjected to a monochromatic, radiant heat flux. An external thermal radiation source is used to simulate the primary mode of energy transfer in a room fire. An incompressible SIMPLE code is used with a staggered grid arrangement. The equations for the fluid and solid (fuel) phases are solved simultaneously using a segregated technique. At the outlet of the computational domain, a convective boundary condition is compared with a traditional Neumann condition. The convective boundary condition is shown to be more effective in reducing the CPU time. A study in the effects of spatial resolution and different time steps are provided. A theory is developed to account for thermal and oxidative degradation. The theory is based on differences in polymer degradation behavior in inert and non-inert environments. A number of quantities such as surface temperature and mass flux of PMMA are calculated by an external source of 40 kW/m2. The predictions of the model are in a good agreement with the experimental results. It is found that an increase in gas-phase oxygen concentration obviously decreases the surface temperature and increases the gasification rate of PMMA. | ||
| کلیدواژهها | ||
| Thermal and oxidative degradation؛ polymers؛ PMMA؛ gasification rate؛ in-depth absorption | ||
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