Modeling thermal response of steel–concrete floor systems in a furnace

• Gas-fired furnace exposure on noncombustible sample governed by radiation exchange.
• Participating media results in 5% change in sample temperature in gas-fired furnace.
• Thermal model with radiation exchange bench-marked with heat flux data.
• Thermal model predicts steel I-beam temperature data within test repeatability.
• Radiation accounts for 70–80% of exposure with convection being 20–30%.

A methodology was developed to predict the thermal exposure from a furnace onto a floor assembly specimen. In furnaces with low conductivity wall linings and gas fired burners with complete combustion, the gas attenuation effects were determined to be small indicating that radiation between surfaces and convection are the dominant modes of heat transfer. This was modeled by assigning the internal furnace wall temperature to the furnace time–temperature exposure and performing a three-dimensional heat transfer analysis on the specimen. The furnace exposure model predicted heat transfer to the specimen surface that was within 5–14% of measured heat fluxes. The proposed furnace exposure methodology was used to predict the temperature rise of steel in a floor assembly where the test specimen can view itself as well as the furnace, making radiation exchange an important aspect of the problem. Predictions were within 5–10% of the measured values, which was within the experimental uncertainty.