Abstract: Abstract: The heat transfer and radiative heat transfer in the pore will reduce the fire resistance of the coating. Considering the existence of gas produced by the decomposition of the coating between the pores, this paper describes the expansion behavior of the coating under different heating conditions through the ideal gas state equation. A finite element heat transfer model was established, which took expansion size as output term and the enhancement effect of pores on effective thermal conductivity, to explore the fire performance of coatings with different thickness under different heating environments. The results show that the expansion size model can accurately predict the expansion behavior of the coating at different temperature fields, and the maximum expansion rate of the coating decreases with the increase of the dry film thickness.The finite element heat transfer model based on the expansion size and the effective thermal conductivity of the pores is in good agreement with the experimental results. In the high heating rate environment, the intumescent coating can significantly delay the heating of steel tube and reduce its maximum fire temperature. Under different heating conditions, the fire resistance and thickness of the coating change nonlinearly.

Key words: Key words: porous media, intumescent coating, expansion behavior, finite element simulation, temperature field