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Matthias Siemon Olaf Riese Burkhard Forell Dominic Krnung Walter Klein‐Heßling 《火与材料》2019,43(5):497-513
In the context of industrial buildings and power plants, electrical installations and cable trays represent a main fuel load and a potential initial fire source due to possible short circuits or comparable malfunction. Furthermore, a fire can spread from one tray to additional trays mounted above and/or horizontally on one tray. Because of the high significance of cable fires, several research projects have been carried out, investigating the fire behaviour of cables from small‐scale tests, eg, the cone calorimeter, up to large‐scale tests, analysing complete cable tray constructions. The goal of the work presented in this paper is the extension of the knowledge regarding the influence of geometrical parameters like the packing density and tray distance on the burning behaviour and fire spread of cable tray installations. The results are considered, together with test results from the literature, to quantify the main physical parameters describing the burning behaviour. In a next step, the general applicability of these parameters as input data for the parametrization of the source term of numerical simulations is shown. The test results show that the burning behaviour and the fire spreading highly depend on the cable arrangement of the cables on the cable tray, in combination with other boundary conditions. By applying the results as input for a fire simulation, the mass loss rate is considered appropriately. 相似文献
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Electrical cable trays are used in large quantities in nuclear power plants (NPPs) and are one of the main potential sources of fire. A malfunction of electrical equipment due to thermal stress for instance may lead to the loss of important safety functions of the NPPs. The investigation of such fires in a confined and mechanically ventilated enclosure has been scarce up to now and limited to nuclear industry. In the scope of the OECD PRISME‐2 project, the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) conducted more than a dozen fire tests involving horizontal electrical cable trays burning either in open atmosphere or inside mechanically ventilated compartments to investigate this topic. A semi‐empirical model of horizontal cable tray fires in a well‐confined and mechanically ventilated enclosure was developed. This model is partly based on the approach used in FLASH‐CAT and on experimental findings from IRSN cables fire tests. It was implemented in the two‐zone model SYLVIA. The major features of the compartment fire experiments could then be reproduced with acceptable error, except for combustion of unburned gases. The development of such a semi‐empirical model is a common practice in fire safety engineering concerned with complex solid fuels. 相似文献
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This paper presents a computational fluid dynamics (CFD)‐based modeling strategy for the prediction of cable tray fire development. The methodology is applied to a set of five horizontal trays (each 2.4‐m long and 0.45‐m wide) that are positioned with a 0.3‐m vertical spacing and set up against an insulated wall. Each tray contains 49 power PVC cables. Ignition is performed with an 80‐kW propane burner centrally positioned at 0.2 m below the lowest tray. A collection of four groups of cables per tray (made of one homogeneous material) is considered. These groups are separated by longitudinal slots of air to “mimic” their relatively “loose arrangement.” The thermal properties and surface ignition temperature are estimated from cone calorimetry (CC). When the ignition temperature is reached, the cables burn according to a prescribed heat release rate per unit area (HRRPUA) profile obtained from CC, as is or in a modified shape. A realistic flame pattern is predicted. Furthermore, using only data from CC, the peak HRR is underpredicted, and the time to reach the peak is overpredicted. The proposed “design” for the modified HRRPUA CC‐profile significantly improves the results. 相似文献
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Electrical cabinet fire is one of the main fire hazards in nuclear power plants. As part of the OECD PRISME‐2 programme, four fire tests were carried out to investigate the fire spread from an open‐doors electrical cabinet to overhead cable trays and adjacent cabinets in a confined and mechanically ventilated facility. These tests, named CFS‐5 to CFS‐7 and CORE‐6, used same both cabinet (fire source) and three overhead cable trays. The trays were filled with a halogenated flame‐retardant cable‐type for CFS‐5 and one halogen‐free for the three other tests. Moreover, fire dampers were used for CFS‐7 test while CORE‐6 test implemented two additional cabinets adjacent to the fire source. Measurements such as flame and gas temperature, gas concentration, mass loss rate, and heat release rate were performed for investigating the fire spread. Cabinet fire spread to the cable trays for CFS‐5 and CFS‐6 tests. Three fast and short cable tray fires were shown for CFS‐5, while a slow and long cable tray fire was highlighted for CFS‐6. In contrast, the fire dampers shutdown for CFS‐7 test prevented ignition of the overhead cables. Furthermore, for CORE‐6 test, cabinet fire spread to the adjacent cabinets, but the upper cables were not ignited. 相似文献
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Cable fires are one of the main fire hazards present in nuclear power plants (NPPs). Therefore, as part of the Organisation for Economic Co‐operation and Development (OECD) PRISME‐2 project, cable tray fire tests were performed both in open atmosphere conditions and in a confined and mechanically ventilated facility, called DIVA. These tests aim at showing the effects of a confined and ventilated environment on fire characteristics and consequences. This study deals with five fire tests, which used halogenated (poly [vinyl chloride] or PVC) cable types. Two tests were carried out in open atmosphere and three tests in the DIVA facility. The latter used a ventilation renewal rate (VRR) of either 4 or 15 h?1. The confined and ventilated conditions reduced the mass loss rate and heat release rate than did those obtained in open atmosphere. Furthermore, the three confined tests produced unburnt gases, which ignited in the fire room. Two explosions were highlighted for the tests that used a VRR of 4 h?1. These explosions indeed led to fast flame propagations over the entire upper part of the fire room and steep overpressures of almost 150 hPa. The low‐qualified PVC cables and the ventilation set‐up used in this study strongly contributed to the occurrence of these explosions. 相似文献
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Fire hazard in nuclear power plants (NPPs) is particularly often investigated as potential cause of safety equipment failure and confinement loss. Many fire events recorded in NPPs involve electric cables, widely used throughout facilities. IRSN is developing the CALIF3S/ISIS computational fluid dynamics software devoted to fire simulation in large‐scale confined and mechanically ventilated compartments. This paper presents two aspects of the CALIF3S/ISIS code ability to simulate fires. The first one concerns vertical and horizontal spreading of a cable tray fire in open atmosphere using an approach based on the FLASH‐CAT cable fire spread model. Resorting to the suitable parameters of the FLASH‐CAT model based on video fire analyses of tests enables to properly compute the heat release rate of the fire. The second aspect concerns the ability to simulate the evolution and consequences of fires in confined and mechanically ventilated compartments. For these cases, the heat release rate measured during the corresponding experiment is used as input data for the calculations. The predicted evolutions of pressure or gas temperatures are in relatively good accordance with the experiments. The major discrepancy concerns gas concentrations in the fire room which is attributed to a lack of information about the properties of the fuel material. 相似文献
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Archibald Tewarson 《火与材料》2003,27(3):131-149
Eight free burning and two sprinklered fire tests were performed with electrical cable trays and live digital switch racks in a large enclosure to simulate telecommunications central office (TCO) fires started by electrical overheating. Very‐slow‐growing (non‐flaming), slower‐growing (partially flaming) and low‐intensity‐faster‐growing (flaming) fires releasing gray‐white, gray, and black smoke, respectively, were observed in the tests. Under quiescent conditions present in the unvented enclosure fire tests for cables, very‐slow‐growing fires were detected in about 1452 s, whereas the slower‐growing fires were detected in about 222 s by commercial fire detectors. Under ventilation conditions typical of TCOs, detection times were very similar for the five types of commercial TCOs fire detectors used in the tests. The average detection times for slower‐growing fires (cable fires) and low‐intensity‐faster‐growing fires (digital switch rack fires) were 242±17% and 249±11%s respectively. The TCO procedures to reduce smoke damage from fires (on fire detection, inlet ventilation flow is turned off and exhaust flow is turned on) were found to be beneficial. The extent of smoke damage decreased significantly with an increase in the exhaust flow rate. The chloride ion mass deposition suggested that equipment recovery would be possible in the smoke environment if the cable vapor concentration could be reduced below about 3 g/m3. The metal corrosion rate was found proportional to the 0.6th power of the smoke concentration, similar to that found for the corrosion of metal surfaces exposed to aqueous solutions of HCl and HNO3 and for acid rain with no protective layer at the surface. Sprinkler water was found to wash down the smoke deposits on the surfaces with little indication of corrosion enhancement. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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T. L. Domingues A. R. Secchi T. F. Mendes 《American Institute of Chemical Engineers》2010,56(9):2323-2330
The main objective of this work is to establish appropriated ways for estimating the overall efficiencies of industrial distillation columns with valve trays with downcomer and dualflow trays. The knowledge of efficiencies has fundamental importance in the design and performance evaluation of distillation columns. Searching in the literature, a tree of alternatives was identified to compose the tray efficiency model, depending on the mass transfer models, the liquid distribution and vapor flow models on the tray, the liquid entrainment model, the multicomponent mixture equilibrium model, the physical properties models, the height of froth on the tray model and the efficiency definition. In this work, different methods to predict the overall efficiency of distillation columns with valve and dualflow trays were composed and compared with data from three commercial distillation columns under different operating conditions. The models were inserted in the Aspen Plus 12.1 simulator, in Fortran language, together with tray geometrical data, fluid properties and operating data of the distillation columns. For each column, the best thermodynamic package was chosen by checking the temperature profile and overhead and bottom compositions obtained via simulation against the corresponding actual data of industrial columns. A modification in the fraction of holes evaluation that is jetting parameter of the Garcia's hydraulic model of dispersion above the tray was proposed. This modification produced better results than the original model to predict the fraction of holes that are jetting and in the efficiency of dualflow trays and similar results to Garcia model in the efficiency evaluation of valve trays. © 2010 American Institute of Chemical Engineers AIChE J, 2010 相似文献
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针对窑炉电助熔应用不同的电源电缆布置方式,通过专用仪表对电缆电流进行测量并分析对比数据,阐述了电缆错相布置对电缆电流平衡分布的积极意义。举例分析减少电源电缆铜损的可行性,论证玻璃钢桥架和电气绝缘板等电缆支撑方式的必要性,同时对比、分析不同电缆线径和不同电缆数量在实际应用中的效果差异。 相似文献
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Yi Tan Volker Wachtendorf Tobias Kukofka Patrick Klack Jörg Ruder Xuebao Lin Bernhard Schartel 《应用聚合物科学杂志》2021,138(14):app50149
The durability of flame retardancy is a challenge for cables over long lifetimes. The degradation of flame retardance is investigated in two kinds of exposures, artificial weathering and humidity. In this basic study, typical mineral flame retardants in two polymers frequently used in cable jackets are investigated to get the fundamental picture. Aluminum hydroxide (ATH) and magnesium hydroxide (MDH) are compared in ethylene-vinyl acetate (EVA), and further in EVA and linear low-density polyethylene (LLDPE) cables containing the same ATH. The changes in chemical structure at the surface are studied through attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), the formation of cracks, and changes in color are investigated. The cone calorimeter and a bench scale fire testing cable module are utilized to evaluate the fire behavior of the cables. Although the flame retardancy deteriorated slightly, it survived harsh exposure conditions for 2000 h. Compared to EVA/MDH and LLDPE/ATH, the fire behavior of EVA/ATH is the least sensitive. Taken together, all of the results converge to estimate that there will be no problem with flame retardancy performance, for materials subjected to natural exposure for several years; the durability of fire retardancy is questionable for longer periods, and thus requires further investigation. 相似文献
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Cable fires are one of the main fire hazards in nuclear power plants. As part of the cable fire spreading (CFS) campaign of the OECD PRISME‐2 programme, 3 real‐scale cable tray fire tests were performed in open atmosphere (1 CFS support test, named CFSS‐2) and in a confined and mechanically ventilated facility (2 CFS tests, named CFS‐3 and CFS‐4). This study aims at investigating the effects of confined and ventilated conditions on cable tray fires that used a halogen‐free flame retardant cable‐type. The CFS‐3 and CFS‐4 tests involved 2 ventilation renewal rates of 4 and 15 h?1, respectively. The confined conditions lead to decrease the fire growth rate and the peaks of mass loss rate and heat release rate, compared with open atmosphere. The reductions are larger for the lower ventilation renewal rate. Furthermore, it is shown that the CFS‐4 test may be classified as a well‐ventilated fire and the CFS‐3 test as an under‐ventilated fire. For this last one, its fire characteristics and its consequences in the fire room highlight an oscillatory behaviour, with the same low frequency, for about 30 minutes. These oscillations arise from successive combustions of unburnt gases. 相似文献
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介绍了导向浮阀塔板的结构特点、实验研究和工业应用情况。由于导向浮阀塔板上的液面梯度较小,液体返混较小,并可消除塔板上的液体滞止区,因而具有优秀的操作性能。导向浮阀塔板已在近百个塔内工业应用,均获得显著的经济效益。 相似文献
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基于欧拉-欧拉模型,采用CFX软件对筛板式填料的气液两相并流流动进行了模拟。将模拟所得的压降与填料的出厂特性值进行了对比,发现在液气动能参数较小的情况下,两者吻合较好。分析了该流场内的速度分布和压力分布的特点,射流卷吸作用使流场内两相流体混合,但涡旋使筛板下方压强减小,射流撞击使筛板上方压强增加。对不同结构的矩形筛板式填料的压降进行研究,结果表明:筛板孔径和液相流量是影响筛板压降的重要因素,开孔直径越小,液相流量对单板压降的影响越大;上层筛孔投影与下层筛孔相交的结构更能有效降低单板压降。液相流量较大时,两个不同板间距的单板压降曲线将相交于一点,气相流量低于此交点时,板间距越小,单板压降越大;气相流量高于此交点时,则相反。 相似文献