Response of stone wool-insulated building barriers under severe heating exposures

This article presents the experimental results of stone wool-layered sandwich constructions, with either steel or gypsum claddings, tested under four different heating exposures: 7kW/m(2) incident radiant heat flux exposure, 60kW/m(2) incident radiant heat flux exposure, parametric time-temperature curve exposure and ISO 834 standard time-temperature exposure. The test apparatus used were a movable radiant panel system, a mid-scale furnace (1.5m(3)) and a large-scale furnace (15m(3)). The results show that reduced-scale tests are capable of reproducing the heat transferred through the construction at large scale provided there is limited mechanical degradation. The results indicate that the availability of oxygen is fundamental to the fire behaviour of the sandwich composites tested. Reactions occurring in stone wool micro-scale testing, such as oxidative combustion of the binder or crystallisation of the fibres, have a limited effect on the temperature increase when wool is protected from air entrainment

Fires in Narrow Construction Cavities : Fire Dynamics and Material Fire Performance

There have recently been devastating fire incidents related to fire spread over ventilated façades. These incidents indicate gaps in our understanding of the fire behaviour of façades. This thesis takes a bottom-up approach to investigating fire behaviour in materials and elements associated with narrow cavities in modern constructions. Ventilated façade is a construction used as an example in this thesis, in which an air gap is introduced between the thermal insulation and the external cladding.Experimental and numerical studies were conducted of flame heights and heat fluxes to the surfaces inside cavities. An experimental programme comprising more than 75 individual tests was done with cavity widths between 2 cm and 10 cm, as well as four different heat release rates from the burner. The study showed increasing flame heights and heat flux as the cavity width is reduced. In this experimental study, the flame height increased up to 2.2 times compared to those near one wall. FDS version 6.7.0 software was then used to assess its capability to replicate the experimental results. One of the identified limitations of FDS was the required small mesh cell size. Furthermore, the thermal response of stone wool and expanded polystyrene when exposed to fire conditions was studied. Four types of stone wool with densities of 37 to 154 kg/m3 were investigated experimentally and numerically. Thermogravimetric analysis and micro combustion calorimetry were used to characterize the thermal decomposition of the stone wool’s organic content. A numerical heat conduction model was developed and showed capability of reproducing the temperatures inside stone wool with relatively low density. Suggestions are provided for improving the model’s performance for high density wools

Fully developed fires in “low-energy” and “energy-efficient” buildings

Buildings use approximately 40% of the total amount of the consumed energy in EU and USA. New design approaches and materials are used to reduce the energy consumption for space heating, ventilation, lightning and other domestic necessities. There is a need to investigate effect of these design features on the fire safety. Increased compartment size can contribute to the fire duration and non-uniform heating of the structural elements. Bigger window areas increase probability of a fuel controlled fire. Advanced glazing systems show better performance, when exposed to high temperatures. Building materials can contribute to the fire load inside a fire compartment. Boundary material properties influence the probability of a flashover and the fire room temperature. Vacuum insulation panel (VIP) is a state-of-the-art building insulation solution. Bench scale tests were conducted with the VIP samples, consisting of a flammable protective envelope and an incombustible siliceous core. 71-129kW/m2 HRR peak was estimated with the total burning time of approximately 75 seconds. The total released energy was estimated to be 1.6-4.1MJ/m2. Degradation of the core material and increased rate of the heat flow through the sample was observed after exposure to the high heat flux

CFD modeling of UMD-SBI fire for the MaCFP-3 Workshop

The purpose of this modelling exercise is to contribute to the structured effort of the MaCFP workshop in the fire research community to make progress in fire modelling, specifically Single Burning Item( SBI) Test [1] in this case, using Computational Fluid Dynamics (CFD) code Fire Dynamics Simulator (FDS) version 6.7.9

Simulation of a liquid methanol fire for the MaCFP Project

Simulations of a liquid Methanol fire with a pool diameter of 30 cm in Fire Dynamics Simulator v6.8.0 (FDS)Experimental data provided by NIST [1] (30 cm - Methanol pool fire case with a lip of 10 mm)Prescribed and Predicted mass loss rates (MLRs)Predicted MLR based on two methods:- Using an EXTERNAL_FLUX on the liquid pool- Using a hot solid object (at 1000° C) as the ignition sourc

CFD modeling of UMD-SBI fire for the MaCFP-3 Workshop

The purpose of this modelling exercise is to contribute to the structured effort of the MaCFP workshop in the fire research community to make progress in fire modelling, specifically Single Burning Item (SBI) Test [1] in this case. Experiments were performed at the University of Maryland (UMD) with the same black PMMA considered in the MaCFP-2 Workshop [2]

Simulation of a liquid methanol fire for the MaCFP Project

Computational fluid dynamics (CFD) is applied to simulate methanol pool fires with pool diameters of 30cm and 1m. The corresponding validation experiments were carried out at Waterloo University and the National Institute of Standards and Technology (NIST). Steady-state profiles of gas temperature, velocity, species concentrations, and radial and axial heat flux profiles were recorded during the experiments which provided the basis for the numerical analysis. During the experiments, the liquid layer height was maintained constant throughout.The CFD tool for fire simulations, Fire Dynamics Simulator v6.8.0 was used for performing the calculations [1]. The two-step simple chemistry combustion model was used to model the oxidation of methanol. FDS allows the user to prescribe the fuel mass flux into the domain and let FDS predict the energy release based on the evaporation of the liquid. Both methods have been incorporated in the study.Sensitivity studies have been performed and included: sensitivity to the mesh resolution for cell sizes ranging from 5 mm to 4 cm; changed temporal and spatial resolution of the radiation solver; and different turbulence models. The preliminary results from the study show that good agreement can be achieved with FDS using the default settings. However, there is still the possibility to improve the predictions from FDS, especially in the near field of the pool fire just above the surface of the liquid pool. Several modifications were done on the default models used in FDS which has led to improved predictions from the simulations.Upon comparing two different radiation solvers (grey gas model and wide band model), it was found that the predictions from the default grey gas model were superior further away from the flames. Based on the sensitivity study on the settings of the grey gas model showed that a spatial resolution of 800 angles was sufficient for good accuracy. Deardorff model and the dynamic Smagorinsky model were used to model turbulence. Upon comparison of the two models, no significant variation was found between their predictions.Furthermore, the puffing frequency of the flames during the steady burning period was estimated using the Fast-Fourier Transform algorithm on the signals of HRR, vertical velocity component and the flame height calculated within FDS

Experimental and numerical investigation on fire behaviour of foam/fabric composites

Upholstered furniture is a major contributor to the fuel load in a fire compartment. Modelling the fire behaviour of upholstered furniture would support performance based fire safety engineering, by allowing the specification of realistic fire scenarios. Modelling upholstered furniture composites in cone calorimeter test conditions is undertaken to validate fundamental assumptions about the fire behaviour of these combinations, without including complexities of a real sized system (e.g. constructional details of mattresses or sofas). Kinetic parameters were taken from micro combustion calorimeter tests and thermal properties were taken from literature and optimised using individual material cone calorimeter tests. A novel methodology of sample preparation was proposed for the cone calorimeter tests in an attempt to increase the one dimensionality of heat transfer. Modelling showed mixed results when compared with experiments. The results also indicated the models incapacity to capture material-material interactions, such as melting of polyester on the top of flexible polyurethane slab or shielding created by cotton residue to protect flexible polyurethane slab from heat exposure

Flame Heights and Heat Transfer in Façade System Ventilation Cavities

The design of buildings using multilayer constructions poses a challenge for fire safety and needs to be understood. Narrow air gaps and cavities are common in many constructions, e.g. ventilated façade systems. In these construction systems flames can enter the cavities and fire can spread on the interior surfaces of the cavities. An experimental program was performed to investigate the influence of the cavity width on the flame heights, the fire driven upward flow and the incident heat fluxes to the inner surfaces of the cavity. The experimental setup consisted of two parallel facing non-combustible plates (0.8 × 1.8 m) and a propane gas burner placed at one of the inner surfaces. The cavity width between the plates ranged from 0.02 m to 0.1 m and the burner heat release rate was varied from 16.5 kW to 40.4 kW per m of the burner length. At least three repeated tests were performed for each scenario. In addition, tests with a single plate were performed. The flame heights did not significantly change for Q′/W < 300 kW/m2 (where Q′ is the heat release rate per unit length of the burner and W is the cavity width). For higher Q′/W ratios flame extensions up to 2.2 times were observed. When the distance between the plates was reduced or the heat release rate was increased, the incident heat fluxes to the inner surface increased along the entire height of the test setup. The results can be used for analysing methodologies for predicting heat transfer and fire spread in narrow air cavities

Characterization of stone wool properties for fire safety engineering calculations

Prediction of the insulating capability of building products in fire conditions would support the product development process. Stone wool insulation is a widely used material in fire barrier constructions. Due to the combustion of its organic content, the temperature inside stone wool can rise above the temperature of the exposed boundary. This temperature rise is difficult to predict. An extensive test program was performed to obtain the thermal and reaction kinetic properties of stone wool. The test methods included modified slug calorimeter, thermogravimetric analysis, differential scanning calorimetry, micro-scale combustion calorimetry and bomb calorimetry. The thermal conductivity in elevated temperatures was similar for all the investigated products. Two positive mass loss rate and heat release rate peaks were observed in temperatures between 20°C and 700°C. Reaction kinetic parameters were obtained and used in a finite difference model predicting the temperature increase in stone wool upon linear heating