Numerical modelling of heat transfer through protected composite structural members

Abstract

Among many various types of passive fire protection materials (i.e. plaster boards, sprayed materials and intumescent coatings) thin film intumescent coatings have become the preferable option owing to their good advantages such as flexibility, good appearance (aesthetics), light weight to the structure and fast application. Despite their popularity, there is also a lack of good understanding of fire behaviour. In general, experimental methods are used to push this knowledge with labour and high-energy consumption and extremely expensive processes. With the development of computer technology, numerical models to predict the heat transfer phenomena of intumescent coatings have been developed with time. In this work, the numerical model has been established to predict the heat transfer performance including material properties such as thermal conductivity and dry film thickness of intumescent coating. The developed numerical model has been divided into different layers to understand the sensitivity of steel temperature to the number of layers of intumescent coating and mesh sizes. The temperature-dependent thermal conductivity of intumescent coatings can be calculated based on inverse solution of the equation for calculating temperatures in protected steel according to the Eurocodes (EN 1993-1-2 and EN 1994-1-2). However, as the temperature distribution in the intumescent coatings is highly non-uniform, that Eurocode equation does not give accurate coating thermal conductivity-temperature relationship for use in numerical heat transfer modelling when the coating is divided into a number of layers, each having its characteristic thermal conductivity values. The comparison study of steel temperature under Standard (ISO 834) and Fast fire conditions against Eurocode analytical solution has also been made by assuming both constant thermal conductivity and variable thermal conductivity. The obtained results show close agreement with the Eurocode solution choosing a minimum certain mesh, number of layer and best-fitted thermal conductivity of the intumescent coating.

Mechanical Properties of S235 Steel Protected with Intumescent Coatings Under High Temperatures: An Experimental Study

“…Active and passive fire protection measures are crucial in mitigating these weaknesses. Among passive measures, intumescent coatings are particularly valued for their ability to significantly delay structural steel from reaching critical temperatures [16][17][18][19][20]. This study aims to build on the foundational work on this topic by exploring how different thicknesses of intumescent coatings influence the thermal and mechanical performance of steel under varied high-temperature scenarios.…”

“…Reactive protection materials, however, are materials whose properties change along with the fire conditions. Among these, expanding (intumescent) coatings are widely used and preferred [16][17][18][19][20]. Intumescent coats expand and swell when exposed to heat and flames during a fire, forming a thick foam-like layer similar to charcoal.…”

Reformative Effects of Intumescent Coating on the Structural Characteristics of Cold-Formed Steel

“…Non-reactive protection materials retain their characteristics when exposed to fire at high temperatures and they are most commonly used in coatings and sprays. Reactive protection materials are known with their changeable characteristics with fire, and the most widely used and preferred type is the intumescent paint. − …”