Simulations of Thermal Performance for One- and Two-Dimensional Insulation and Aluminum Foil Fire Barriers

Nonbearing walls made of concrete frequently include one or two-dimensional gaps between sections to allow the concrete exert expansion or contraction due to temperature transients. These section gaps require the use of a thermal fire barrier to stop a fire from spreading during a period of time. In some applications, such as seismic structures, fire barriers are large and form substructures and partial enclosures. These type of fire barriers are often manufactured by layering alternating blankets of ceramic fiber insulation with bounding thin metallic foil sheets. In this case, the barrier must meet the specifications and effectiveness given by the ASTM standard E-119. This effectiveness is determined by the requirement of maintaining structural integrity by allowing some heat release while not permitting the fire flame to pass through. Little data is available on the thermal interaction of 2-D corners and splicing the layers for large barriers. It is expected that spatial and angular effects might either degrade performance or even cause “hot spots” in a barrier wall. Therefore, a numerical simulation of the barrier is accomplished by utilizing the spectral/gray and directional/modeled data of each one of the components and by taking into account two common geometrical building shapes. This simulation analysis is done by coupling of the discrete ordinates method in radiation heat transfer and the energy equation to previously published thermophysical experimental data used as a validation of the properties for fire barrier materials. Some of the effects of directional and surface properties and radiative heat transfer in fire barrier materials have been included in the numerical model. The Fluent®-based numerical model is able to match thermal performance of previous test systems. Initial calculations suggest that a fire barrier consisting of a 2D corner geometry exposed to a fire from either side would be thermally less robust than a slab of the same characteristic aspect ratio. This approximation has shown a preferential orientation for the barrier to be positioned when a fire or other high energy source is postulated.