Heat transfer in intumescent heat- and fire-insulating coatings

Abstract

The physicochemical and thermophysical processes that jointly occur in intumescent heat-and fire-insulating coatings are studied numerically with the use of a model based on the hypothesis that the gaseous products of thermal expansion of an initial material are transparent. It is found that with the radiative mechanism of heat transfer in a layer of intumescent-coating coke taken into account, the temperature at the surface of a structure to be protected is almost equal to a temperature reached at this surface if a nonintumescent coating is used.Intumescent heat-and fire-insulating coatings (IHFIC) are considered to be promising coatings for fire protection of various industrial and social objects [1, 2]. A model whose equations contain the coefficient of "radiative thermal conductivity" is used to analyze the effectiveness of these coatings [1]. Generally, this coefficient is written using Rosseland's approximation [3] in terms of the constant 7. This constant cannot be obtained only experimentally [1] and is found by comparing calculation results obtained with the use of model and experimental data. In this procedure of 7 determination, the model [1] is not closed, and the parameter 7 serves to match theoretical and experimental data.In the problem is considered within the framework of Rosseland's approximation for media with high optical density.The adopted assumptions do not impose strict restrictions on the range of variation of the parameters which determine the intensity of heat transfer in a layer of IHFIC coke with high porosity (up to 0, 95). In this formulation, the consideration omits minor factors allowance for which requires experimental data which cannot be obtained for the majority

Decomposition of Intumescent Coatings: Comparison between a Numerical Method and Experimental Results

“…Due to the thermal decomposition complexity of intumescent coating systems, the models presented so far are based on several assumptions, the most relevant being the consideration of one-dimensional heat transfer through material, temperature and space independent thermal properties and the assumption of a constant incident heat flux where the heat losses by radiation and convection are ignored [3]. Some authors also assume that the thermochemical processes of intumescence occur without energy release or energy absorption [6]. Results show that the insulation efficiency of the char depends on the cell structure, and the low thermal conductivity of intumescent chars results from the pockets of trapped gas within the porous char which act as a blowing agent to the solid material.…”