Intumescent coating, as a new generation of fire proof material, has obvious advantages over traditional fire protection materials. The applications of intumescent coating are widely ranged and it has become dominant in the fire engineering market. However, the present method of assessment in EN 13381 Part 4 is not suitable for applications of intumescent coating under realistic fire conditions, because intumescent coating behaviour is not only temperature dependent, but also fire exposure dependent. The failure of currently available method to give accurate predictions of intumescent coating thermal performance motivated this research. Against this background, a 1-0 mathematical model has been established to consider chemical kinetics, mass and energy conservation, and heat transfer through solid and gas phases. The model couples the degradation of three basic components (inorganic acid source, blowing agent, and charring material) with a variable volume system. Basic volatile mass transfer and simplified bubbling mechanisms have been described in assistance to calculate the non-linear distribution of temperature along the coating thickness. The model is presented in terms of Finite Difference Method (FOM) equations and is solved using FORTRAN programming. Then, an extensive sensitivity study has been carried out to identify most influential parameters among a large number of material input data required by the mathematical model. A. The activation energies of the blowing agent and the charring material, the maximum expansion coefficient and the final bubble size have been shown to have the most influence on the predicted steel temperature results. To assess the influence of different pore size distributions, Finite Element simulations (ABAQUS) were performed. The results of this numerical study indicate that, given the same porosity, the overall thermal conductivity of the porous structure is very close to that with uniform distribution of pores of the dominant size. This strongly suggests that, given the difficulty of obtaining precise pore size distribution, it is practically acceptable to treat an intumescent coating as having a uniform distribution of pores of the same size. A number of cone-calorimeter tests have been carried out with different coating thicknesses, steel substrate thicknesses, and external heat fluxes. The investigation focused on how to extract key parameters of the model from limited number of experimental tests, and how to make use of the model in different applications. The estimated input parameters are able to predict all the cone calorimeter tests to match the experimental measurement with reasonably good agreement, which demonstrates the feasibility of the modelling approach. Finally, to provide comprehensive validation, both standard and parametric furnace fire tests have been performed. The key parameters of chemical kinetics and intumescent char bubble size were determined experimentally. The TGA test data were used to obtain the major intumescent coating component fractions and the various chemical kinetics constants. The mathematical model described in this study is able to accurately predict both the standard fire test results and the parametric fire test results. The only requirement is that the final expansion coefficient of the intumescent coating should be provided as input data.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:498956 |
| Date | January 2009 |
| Creators | Yuan, Jifeng |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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