A new methodology to calculate interface thermal resistance between intumescent coating and steel substrate

Interface thermal resistance (ITR) plays a very important role in heat transfer and thermomechanical coupling response from intumescent coating to steel substrate in fire. However, the dynamic ITR between intumescent coating and steel substrate during burning is seldom reported. In this paper, a new methodology is presented to calculate dynamic ITR between intumescent coating and steel substrate under high incident heat flux based on the interface conservation equation. The new methodology focuses on measuring the temperature distribution and thermal conductivity of intumescent coating and steel substrate, with fewer variables. In this way, the calculation of ITR can be simplified. Firstly, the temperature variation function curves inside the intumescent coating and the steel substrate were fitted separately based on the temperature measurement data. Secondly, the interface temperatures ($T_{\mathrm{ci}},T_{\mathrm{si}}$) were determined separately at the interface position by temperature variation function curves inside the intumescent coating or the steel substrate. Finally, the ITR calculation formula was deduced and the key parameters required for ITR calculation were obtained by cone calorimetry et al. An illustrative example was studied and validate the applicability of the new methodology.