Pool Fires: a Model for Assessing Meteorological Parameters Influence on Thermal Radiation (original) (raw)
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Thermal radiation from pool fires
Combustion and Flame, 1977
For an axisymmetric, horizontal, pool fire of specified flame shape, effective flame radiation (Schmidtl temperature and a gray flame absorption coefficient, this analysis computes (l) radiative energy fluxes to surfaces located external to the fire in any arbitrary orientation, (2) variations of radiative heat flux along the fuel surface, from fire center to fire edge, (3) the total radiative heat transfer from the flames to the fuel surface, (4) forward radiative heat transfer from the fire to the virgin fuel bed external to the fire, (5) the angular distribution of the radiative flux emitted by the pool fire and (6) the total radiative power output of the fire. The calculations agree with experimentally measured radiative fluxes at different locations on the pool surface and outside the fire. The radiative flux from the flames to the burning fuel surface is maximum at the center of the fuel bed and it decreases markedly toward the edge of the fire. The forward radiative heat transfer from the flames, to the virgin fuel bed external to the fire, is highest at the leading edge of the fire and it decays rapidly with increasing distance from it. Necessary conditions for validity of isotropic flame radiation are established.
Flame Radiation Characteristics of Open Hydrocarbon Pool Fires
Lecture Notes in Engineering and Computer …, 2011
The fundamental subject of fire research with problems involving hydrocarbon pool fires focuses on thermal radiation from the flame surface. Smoke obscuration and pool fire size are parameters of influence. The object is to establish the temperature and heat flux profiles, and assess the hazard consequences that may arise from these fire actions. This investigation, therefore, provides a correlation for the surface emissive power of flame based on observed data taken from five different experimental studies. It is shown in this study that due to spatial and temporal variations associated with trials conducted at different times and locations on free-burning pool fires, model predictions for surface emissive power of flame can be very different. The present correlation provides a reasonable prediction for liquefied natural gas and aviation fuels compared to those of Shokri and Beyler, and Mudan and Croce. However, the investigation reveals that a coefficient of variation between 6 and 17 per cent can be found by separately adopting the flame height models of Heskestad and Thomas for fire diameters up to 120 m. This highlights the need to exclusively utilize a given methodology, which gives a clear description of all sub-models used in the derivation of surface emissive powers of free-burning hydrocarbon pool fires. It is noted that the significance of thermal radiation model also broadens the means by which the acceptable separation distances between radiation source and targets _ people and structures can be determined.
Developments in Modelling of Thermal Radiation from Pool and Jet Fires
In the past decades, the standard approach in the modelling of consequences of pool and jet fires would be to describe these fires as tilted cylindrical shaped radiating flame surfaces, having a specific SEP (Surface Emissive Power). Some fine tuning on pool fires has been done by Rew and Hulbert in the late nineties to divide the flame in a clear and sooty part, and provide some typical-substance dependent-values for SEP clear and SEP soot. However, this approach still describes the pool-fire as a tilted and cylindrical shaped radiator. Unfortunately, in the real world, the typical pool fire dimensions, and consequently the flame shape, are being determined by local circumstances, such as the presence of a semi-rectangular bund around storage tanks. Other pool shape determining examples are ditches, drains or even elevated platforms that restrict the free spreading of a pool and lead to a specific pool shape. Of course the resulting pool surface will not only determine pool burning rate, but also the radiation behaviour. In order to predict the consequences of these " real world " situation, TNO extended the fire modelling in its consequence calculation software EFFECTS® with a more elaborated radiation calculation, additionally providing the possibility to determine heat load distribution on a receiving object. In case of a pool fire, the expected pool dimensions can be drawn (on top of a topographic map or aerial photo) and potential receiving objects can be defined, such as nearby installations, including typical vulnerability thresholds. This enables the possibility to evaluate potential domino effects of a fire. The same approach is also used for jet fires, now describing the jet as a truly cone shaped radiator, which can be pointed in any direction. The paper will provide a full description of the applied method, including some typical application examples 1. Fire modelling Fire modelling should be seen as an important part of consequence modelling, allowing to predict potential damage due to heat radiation of fires. Fire models themselves can be separated in models describing either jet fire, pool fire or fireball (BLEVE) phenomena. A jet fire model describes the fire phenomenon of a gaseous or two phase (e.g. Propane) continuous release. Such a jet fire model (sometimes referred to as " torch fire ") generally describes the size and shape of a cone or cylindrical shaped fire surface, and provides information about heat radiation versus distance or location. A high outflow velocity will also introduce a lift-off effect, causing the flame shape to start at certain distance from the actual release point. The flame tilt angle of the jet is highly influenced by the wind speed and will thus determine the resulting flame geometry and radiation pattern. A pool fire describes a flame surface on top of a burning liquid pool. The pool fire is usually described as a cylindrical shaped flame geometry, which will be tilted by the wind. Typical results of a pool fire model contain flame diameter, flame height and tilt, and heat radiation levels at various distances from the pool. Although a BLEVE (Boiling Liquid Expanding Vapour Explosion) is technically a description of an explosion (e.g. overpressure) phenomenon, the potential BLEVE of an LPG vessel is feared the most because of its fireball result. Dedicated BLEVE fireball models have been developed, describing the diameter and lift-off a the spherical flame and resulting heat load. These models all have in common that they use " Solid flame modelling " , describing the surface of the flame as a specific geometry, with a typical Surface Emissive Power (SEP) leading to a corresponding heat radiation footprint.
Predicting the emissive power of hydrocarbon pool fires
Journal of Hazardous Materials, 2007
The emissive power (E) of a flame depends on the size of the fire and the type of fuel. In fact, it changes significantly over the flame surface: the zones of luminous flame have high emittance, while those covered by smoke have low E values. The emissive power of each zone (that is, the luminous or clear flame and the non-luminous or smoky flame) and the portion of total flame area they occupy must be assessed when a two-zone model is used.
Experimental Investigation of Thermal Hazards and Toxic Emissions from Process Industry Pool Fires
SSRN, Elsevier, 2022
Thermal radiation and toxic gas emissions are the primary hazards of burning fires. Various types of fuels and flammable liquid chemicals are used in the process industry in day-today applications. Leakage and spillage of these flammable liquids may cause extremely hazardous pool fires during their handling process. A medium-scaled experimental investigation of diesel pool fires estimates the thermal impact at different locations and determines the toxic gas emissions. The most exciting finding is that a medium-scale burning of diesel pool fire produced an average heat flux of 7 kW/m 2 , which is undoubtedly (Hazardous to humans > 1.5 kW/m 2) as per the National Fire Protection Association: 921 (NFPA) guidelines. Also, the study highlighted the toxic gas emissions from pool fires and compared them with Occupational Safety and Health Administration (OSHA) standards.
Modeling of pool fires in cold regions
Fire Safety Journal, 2012
Fires and especially pool fires are among the most frequent accidents in process facilities. Flame impingement and thermal radiation are the main hazardous characteristics of pool fires. Pool fires have been the subject of numerous modeling and experimental studies covering a variety of areas such as fire and flame structure, emissive power, temperature distribution and fire characteristics. The effects of environmental parameters such as wind velocity, humidity and water/ice droplets in the air have not been studied extensively. Further, the effect of surrounding surface reflectivity has not been studied. This issue is very important for cold regions like the Arctic, where outdoor surfaces are covered with snow and ice for several months of the year. Furthermore, there is no comprehensive fire consequence modeling tool that includes pool fire development, environmental characteristics effects and thermal radiation. This study proposes a new comprehensive model for steady state and fully developed pool fires. This new model takes into account the effects of environmental variables such as temperature, the presence of droplets and surface reflectivity on thermal radiation and subsequently on the fire consequence assessment.
Estimation of heat release rate for gasoline pool fires
International Journal on Engineering Performance-Based Fire Codes, 2007
The heat release rate of liquid pool fires in full-scale burning tests and field tests were commonly adjusted by using different square trays of size 0.5 m. The heat release rates of gasoline pool fires under different ventilation factors were measured by the oxygen consumption method. Experimental data on the heat release rate of those gasoline fires were used to deduce empirical correlations. Results will be reported in this paper. Heat release rate per unit area of liquid gasoline was estimated to be 1670 kWm-2 in a room calorimeter. For tests with a square tray of 0.5 m by 0.5 m, the volume of gasoline was 58 litres for a burning duration of half an hour. The heat release rate was about 400 kW per tray.
Accurate calculations of heat release in fires
1998
Fire is often considered as the most hazardous accidental event which may affect safety in the chemical industries. The fire damage may be thermal or non thermal. As examples, the fire plume may transport a variety of toxic effluents, which may injure the staff of the industrial premises and the fire fighters, as well as the inhabitants in the neighbourhood. Intense radiation produced by big fires may cause serious burn injuries and generate "domino effects" to previously non affected equipment in the vicinity and result in related phenomena such as jetfires, fireballs, BLEVEs1 . Moreover, polluted extinction waters while unconfined may greatly affect the aquatic environment. Although several ambitious projects were recently carried out in the field, there is still much work to be performed to get validated techniques capable of predicting (and keeping under acceptable control) the consequences of indoor and outdoor large chemical fires.
Journal of Hazardous Materials, 2007
In a recent paper [P.K. Raj, Large LNG fire thermal radiation-modeling issues and hazard criteria revisited, Process Safety Progr., 24 (3) (2005)] it was shown that large, turbulent fires on hydrocarbon liquid pools display several characteristics including, pulsating burning, production of smoke, and reduced thermal radiation, with increasing size. In this paper, a semi-empirical mathematical model is proposed which considers several of these important fire characteristics. Also included in this paper are the experimental results for the variation of the fire radiance from bottom to top of the fire (and their statistical distribution) from the largest land spill LNG pool fire test conducted to date. The purpose of the model described in this paper is to predict the variation of thermal radiation output along the fire plume and to estimate the overall thermal emission from the fire as a function its size taking into consideration the smoke effects. The model utilizes experimentally measured data for different parameters and uses correlations developed from laboratory and field tests with different fuels. The fire dynamics and combustion of the fuel are modeled using known entrainment and combustion efficiency parameter values. The mean emissive power data from field tests are compared with model predictions. Model results for the average emissive powers of large, hypothetical LNG fires are indicated.
On various modeling approaches to radiative heat transfer in pool fires
Combustion and Flame, 2007
Six computational methods for solution of the radiative transfer equation in an absorbing-emitting, nonscattering gray medium were compared for a 2-m JP-8 pool fire. The emission temperature and absorption coefficient fields were taken from a synthetic fire due to the lack of a complete set of experimental data for computing radiation for large and fully turbulent fires. These quantities were generated by a code that has been shown to agree well with the limited quantity of relevant data in the literature. Reference solutions to the governing equation were determined using the Monte Carlo method and a ray-tracing scheme with high angular resolution. Solutions using the discrete transfer method (DTM), the discrete ordinates method (DOM) with both S 4 and LC 11 quadratures, and a moment model using the M 1 closure were compared to the reference solutions in both isotropic and anisotropic regions of the computational domain. Inside the fire, where radiation is isotropic, all methods gave comparable results with good accuracy. Predictions of DTM agreed well with the reference solutions, which is expected for a technique based on ray tracing. DOM LC 11 was shown to be more accurate than the commonly used S 4 quadrature scheme, especially in anisotropic regions of the fire domain. On the other hand, DOM S 4 gives an accurate source term and, in isotropic regions, correct fluxes. The M 1 results agreed well with other solution techniques and were comparable to DOM S 4. This represents the first study where the M 1 method was applied to a combustion problem occurring in a complex three-dimensional geometry. Future applications of M 1 to fires and similar problems are recommended, considering its similar accuracy and the fact that it has significantly lower computational cost than DOM S 4 .