Externally venting flames (EVF) may emerge through openings in fully developed under-ventilated compartment fires, significantly increasing the risk of fire spreading to higher floors or adjacent buildings. Several fire engineering correlations have been developed, aiming to describe the main characteristics of EVF that affect the fire safety design aspects of a building, such as EVF geometry, EVF centreline temperature and EVF-induced heat flux to the fac¸ade elements. This work is motivated by recent literature reports suggesting that existing correlations, proposed in fire safety design guidelines (e.g. Eurocodes), cannot describe with sufficient accuracy the characteristics of EVF under realistic fire conditions. In this context, a wide range of EVF correlations are comparatively assessed and evaluated. Quantification of their predictive capabilities is achieved by means of comparison with measurements obtained in 30 different large-scale compartment-fac¸ade fire experiments, covering a broad range of heat release rates (2.8 MW to 10.3 MW), ventilation factor values (2.6 m 5/2 to 11.53 m 5/2 ) and ventilation conditions (no forced draught, forced draught). A detailed analysis of the obtained results and the respective errors corroborates the fact that many correlations significantly under-predict critical physical parameters, thus resulting in reduced (non-conservative) fire safety levels. The effect of commonly used assumptions (e.g. EVF envelope shape or model parameters for convective and radiative heat transfer calculations) on the accuracy of the predicted values is determined, aiming to highlight the potential to improve the fire engineering design correlations currently available.Total area of vertical openings on all walls of the compartment c (4.67)Empirical factor (Eq. 19) C p (1005 J/kg K) Specific heat of air at ambient conditions D v (m)Effective diameter of the opening d eq (m)Characteristic length scale of an external structural element E b (kW/m 2 ) Black body emissive power g (9.81 m/s 2 )Gravitational acceleration H 0 (m)Opening height H u (13,100 kJ/kg O 2 )Heat release of cellulosic fuels for each kilogram of oxygen consumed h eq (m)Weighted average of openings heights on all walls k (m -1 ) Extinction coefficient k fuel (m -1 ) Extinction coefficient for the combustion products of a specific fuel L L_0.05 (m) Flame height at the ''continuous flame'' (5% flame intermittency limit) L L_0.50 (m) Flame height at the ''intermittent flame'' (50% flame intermittency limit) L L_0.95 (m) Flame height at the ''far-field flame'' (95% flame intermittency limit) L L (m) Height of EVF L H (m) Projection of EVF L f (m) Flame length l (-) Characteristic length scale (Eq. 9) l x (m) Length along the EVF centerline, originating at the opening _ m a (kg/s) Air mass flow rate (entering the fire compartment) _ m f (kg/s) Fuel mass flow rate _ m O2 (kg/s) Oxygen mass flow rate _ m g (kg) Mass flow rate of unburnt gases venting outside the fire compartment _ Q (MW) Heat Release Rate _ Q ex (MW) Excess Heat Rele...
In a compartment fire, Externally Venting Flames (EVF) may significantly increase the risk of fire spreading to adjacent floors or buildings; EVF-induced risks are constantly growing due to the ever-increasing trend of using combustible materials in building facades. The main aim of this work is to investigate the fundamental physical phenomena associated with Externally Venting Flames (EVF) and the factors influencing their dynamic development. In this context, a series of fire tests is conducted in a medium-scale compartment-façade configuration; an n-hexane liquid pool fire is employed, aiming to realistically simulate an "expendable" fire source. A parametric study is performed by varying the fire load density (127.75, 255.5 and 511 MJ/m 2) and opening factor (0.071 and 0.033 m 3/2). Emphasis is given to characterization of the thermal field developing adjacent to the façade wall. Experimental results suggest that the three characteristic EVF phases, namely "internal flaming", "intermittent flame ejection" and "consistent external flaming", are mainly affected by the opening dimensions, whereas the fuel load has a notable impact on the fuel consumption rate and heat flux to the façade. Fuel consumption rates were found to increase with increasing fire load and opening area, whereas the global equivalence ratio increases with decreasing opening factor. The obtained extensive set of experimental data can be used to validate CFD fire models as well as to evaluate the accuracy of available fire design correlations.
A full-scale compartment fire test was performed to assess gypsum plasterboards and wood based panels as cladding materials for the fire protection of light and massive timber elements.The test compartment was constructed using both the Timber Frame and the Cross Laminated Timber techniques; a wood crib was used to achieve realistic fire conditions. Temperature measurements and optical inspection evidence suggested that gypsum plasterboards offered adequate fire protection since they did not fail and no charring was observed in the timber elements. A free standing wall inside the test compartment, protected by wood-based panels, partially collapsed. Measured values of characteristic failure times, such as time to failure of fire protection cladding and time to onset of charring, were compared to relevant Eurocode correlations, achieving good levels of agreement. The obtained set of measurements, describing the time evolution of a large variety of physical parameters, such as gas and wall layer temperatures, can be used for validation of relevant advanced fire simulation tools.
In a compartment fire, Externally Venting Flames (EVF) may significantly increase the risk of fire spreading to adjacent floors or buildings, especially when combustible insulation materials are installed on the building façade. An increasing number of recent reports suggest that existing fire engineering design methodologies cannot describe with sufficient accuracy the characteristics of EVF under realistic fire load conditions. In this context, a series of fire safety engineering design correlations used to describe the main EVF thermal characteristics, namely EVF centreline temperature and EVF-induced heat flux on the exposed façade surface, are comparatively assessed. Towards this end, measurements obtained in a medium-and a large-scale compartment-façade fire test are employed; aiming to broaden the scope of the validation study, predictions of the investigated correlations are further compared to measurements obtained in 6 large-scale fire tests found in the literature. It is found that the correlation proposed in EN1991-1-2 (Eurocode 1) for the estimation of the EVF centreline temperature is under-predicting the measured values in large-scale fire tests. In addition, it is concluded that estimation of the local flame emissivity should take into account the specific fuel type used in each case.
This work aims to investigate the burning behavior of liquid fuel pool fires in corridor-like enclosures and to identify key factors influencing fire development. A series of experiments is conducted in a 3 m long medium-scale corridor-facade configuration using ethanol pool fires. To minimize lip effects, a novel fuel supply system has been developed. The influence of fuel surface area and ventilation factor on the fire development is investigated by using two different pan sizes and eight opening dimensions. Experimental results indicate that in corridor-like enclosures the steady-state fuel burning rate in ventilation-controlled conditions corresponds to about 2/3 of that observed in cubic-like enclosures, because the temperature distribution in the enclosure changes from uniform, in cubic-like enclosures, to layered, in corridors. The ventilation coefficient, used to calculate the inflow rate in corridor-like enclosures during post-flashover conditions, is found to decrease as the ventilation factor increases. Subsequently, the heat released inside the corridor was found less than that in cases of burning in cubic-like enclosures. The series of data obtained in the present work can be used for validating engineering correlations and evaluation of CFD models.
In a fully developed under-ventilated compartment fire, flames may spill out of external openings (e.g. windows); Externally Venting Flames (EVF) pose a significant risk of fire spreading to adjacent floors or buildings. The main aim of this work is to comparatively assess a range of fire engineering design correlations used to describe the external dimensions of the EVF envelope. The predictive accuracy of each correlation is evaluated through comparison with experimental data obtained in a medium-scale compartment-façade fire facility, using typical fire loads suggested in the Eurocode. A series of fire tests is performed, employing a ¼ scale model of the ISO 9705 room, equipped with an additional extended façade. An "expendable" fuel source (n-hexane) is utilized to effectively simulate realistic building fire conditions. An extensive sensor network is used to monitor the dynamic behaviour of a broad range of important EVF physical parameters and a dedicated image processing tool is developed to allow estimation of the EVF envelope main dimensions (e.g. height, width, projection). Digital camera imaging is used to determine the main geometrical characteristics of the EVF envelope. Comparison of fire engineering design correlation predictions with experimental data reveals that correlations for the estimation of EVF height err on the safe side in under-ventilated fire conditions; decreasing the fire load results in under-prediction of EVF height and projection. It is shown that EVF projection and width strongly depend on both excess heat release rate and height. In addition, the necessity to derive appropriate criteria for the identification of the EVF projection is demonstrated. The obtained extensive set of experimental data, covering three different fire load levels, can be also used to validate numerical simulation tools or evaluate the accuracy of other available fire design correlations.
Modern day energy codes are driving the design and multi-layered configuration of exterior wall systems with a significant emphasis on achieving high performance insulation towards improving energy performance of building envelopes. Use of highly insulating polyisocyanurate (PIR) based materials enhanced with eco-friendly lamellar inorganic fillers reinforces energy performance requirements, environmental challenges and cost reduction without compromising the overall building fire safety. The current work assessed the fire behaviour of PIR modified with three layered fillers, namely MgAlCO3 (PIR-LDH1), MgAl Stearate (PIR-LDH2) and Zirconium Phosphate octadecylamine (PIR-ZrP3). For each of the fillers, three loadings (2, 4 and 6 % by weight) were used.Optical analysis by X-ray diffraction patterns (XRD), cone calorimeter (CC), thermogravimetric (TGA) analysis, post-burning morphological evaluation using field emission scanning electron microscope (FESEM) and diffuse reflectance infrared spectroscopy (DRIFT) analysis, were performed. The results indicated that fire reaction properties and thermal stability of foam samples were enhanced with three different types of lamellar inorganic smart fillers. The initial degradation temperature of PIR-layered filler samples was increased, demonstrating that incorporation of flame retardants decelerated the degradation of PIR foam and contributed to significant char formation, from 19.5% in pure PIR samples to 33% in PIR-6%LDH1 samples. Increasing the filler content also resulted in improved char properties and decreased peak Heat Release Rates (HRR) in the cone calorimeter.Due to the development of a stable char layer, samples containing 6% of ZrP3 did not ignite at 20kW/m 2 and a reduction of up to 40% in the peak HRR was achieved in PIR-2%ZrP3 samples.
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