scholarly journals Horizontal cable tray fire in a well‐confined and mechanically ventilated enclosure using a two‐zone model

2019 ◽  
Author(s):  
William Plumecocq ◽  
Laurent Audouin ◽  
Pascal Zavaleta
Keyword(s):  
Zone Model ◽  
Mechanically Ventilated ◽  
Tray Fire

Pulmonary Blood Flow Redistribution with Low Levels of Positive End-expiratory Pressure 

1998 ◽  
Vol 88 (5) ◽  
pp. 1291-1299 ◽  
Author(s):  
Harry J. Kallas ◽  
Karen B. Domino ◽  
Robb W. Glenny ◽  
Emily A. Anderson ◽  
Michael P. Hlastala
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Zone Model ◽  
Structural Factors ◽  
Positive End Expiratory Pressure ◽  
Mechanically Ventilated ◽  
Anesthetized Dogs ◽  
Low Levels ◽  
Ventilation And Perfusion ◽  
Lung Zone

Background Recent studies have questioned the importance of the gravitational model of pulmonary perfusion. Because low levels of positive end-expiratory pressure (PEEP) are commonly used during anesthesia, the authors studied the distribution of pulmonary blood flow with low levels of PEEP using a high spatial resolution technique. They hypothesized that if hydrostatic factors were important in the distribution of pulmonary blood flow, PEEP would redistribute flow to more dependent lung regions. Methods The effects of zero cm H2O PEEP and 5 cm H2O PEEP on pulmonary gas exchange were studied using the multiple inert gas elimination technique; the distribution of pulmonary blood flow, using fluorescent-labeled microspheres, was also investigated in mechanically ventilated, pentobarbital-anesthetized dogs. The lungs were removed, cleared of blood, dried at total lung capacity, and then cubed to obtain approximately 1,000 small pieces of lung (approximately 1.7 cm3). Results Positive end-expiratory pressure increased the partial pressure of oxygen by 6 +/- 2 mmHg (P < 0.05) and reduced all measures of ventilation and perfusion heterogeneity (P < 0.05). By reducing flow to nondependent ventral lung regions and increasing flow to dependent dorsal lung regions, PEEP increased (P < 0.05) the dorsal-to-ventral gradient. Redistribution of blood flow with PEEP accounted for 7 +/- 3%, whereas structural factors accounted for 93 +/- 3% of the total variance in blood flow. Conclusions The increase in dependent-to-nondependent gradient with PEEP is partially consistent with the gravitationally based lung zone model. However, the results emphasize the greater importance of anatomic factors in determining the distribution of pulmonary blood flow.

Applicability of FLASH-CAT Model to Cable Tray Fire Modeling in Zone Model BRI2002

2020 ◽  
Author(s):  
Koji Shirai ◽  
Koji Tasaka ◽  
Toshiko Udagawa
Keyword(s):  
Mass Loss ◽  
Large Scale ◽  
Fire Test ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Zone Model ◽  
Gas Temperature ◽  
Fire Source ◽  
Gas Burner ◽  
Tray Fire

Abstract To clarify the heat and smoke propagation in multi-compartments under the spread of cable fire, a large-scale multi-compartment fire test (hereinafter the CFS-2 test) was performed by the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) in France within the framework promoted by the Nuclear Energy Agency (NEA) in Organization for Economic Co-operation and Development (OECD) program PRISME2 (OECD/NEA, 2017). In the CFS-2 test, two rooms of a large-scale facility were adopted and these rooms have an identical volume (120 m3) enclosed with fire walls and were connected by a doorway (0.8 m in width and 2.17 m in height). As a fire source, five-layer cable trays (tray length of 2.4m, tray width of 0.45m and separation distance between trays of 0.3 m) with a fire-retardant PVC cable (77 kg) were used and ignited by a propane gas burner. The power level of the propane gas burner was set to around 80 kW. Moreover, all rooms were mechanically ventilated, and the renewal rate was 15 times per hour (3600 m3/h). During the fire test, the mass loss rate of fuel, gas and soot mass concentration, gas temperature, and etc. were measured. The measured peak values of the HRR, the mass loss rate and gas temperature were about 800 kW, 58 g/s and greater than 600 °C, respectively (Zavaleta, 2017). As a fire model predicting fire characteristics in a compartment, a two-zone model, which divides the fire room into the hot smoke upper layer and lower layer consisting of cool fresh air, is widely used due to the advantages of the brevity of the calculation routine and the reliability of the calculation results. Among them, the BRI2 series, developed in Japan, is now reaching the current BRI2002 software (Wakamatsu, 2004) after several upgrades to improve the calculation precision. The Central Research Institute of Electric Power Industry (CRIEPI) introduced the cable tray fire source model based on the FLASH-CAT (Flame Spread over Horizontal Cable Trays) developed by National Institute of Standards and Technology (NIST) (McGrattan, 2012) into the zone code BRI2002. By comparing the numerical results with the experimental values measured during the CFS-2 test, the methodology for ignition time delay of each tray and horizontal flame propagation speed for each tray were discussed.

Cable tray fire tests with halogenated electric cables in a confined and mechanically ventilated facility

2019 ◽  
Vol 43 (5) ◽  
pp. 543-560 ◽  
Author(s):  
Pascal Zavaleta ◽  
Sylvain Suard ◽  
Laurent Audouin
Keyword(s):  
Fire Tests ◽  
Mechanically Ventilated ◽  
Electric Cables ◽  
Tray Fire

Cable tray fire tests in a confined and mechanically ventilated facility

2017 ◽  
Vol 42 (1) ◽  
pp. 28-43 ◽  
Author(s):  
Pascal Zavaleta ◽  
Laurent Audouin
Keyword(s):  
Fire Tests ◽  
Mechanically Ventilated ◽  
Tray Fire

A modified zone model on vertical cable tray fire in a confined compartment in the nuclear power plant

2018 ◽  
Vol 36 (6) ◽  
pp. 472-493 ◽  
Author(s):  
Xianjia Huang ◽  
Zhaoying Ren ◽  
He Zhu ◽  
Lan Peng ◽  
Chihonn Cheng ◽  
...  
Keyword(s):  
Flame Spread ◽  
Nuclear Power ◽  
Fire Hazard ◽  
Computing Time ◽  
Temporal Variations ◽  
Zone Model ◽  
Measured Temperature ◽  
Upward Flame Spread ◽  
Line Spacing ◽  
Tray Fire

Room fire with vertical cable tray involves upward flame spread along the cable. Assessing the vertical cable tray fire hazard in confined spaces has been challenging because of the strong coupling between flame spread and heat transfer. Long computing time is required in using sophisticated field model with computational fluid dynamics. Therefore, developing an appropriate zone model in a cable room fire with experimental validation is required for engineering applications. In this study, a vertical cable tray fire in a confined compartment was simulated using a modified zone model along three new areas on having temporal variations of the fire position, upward-spreading cable flame considered as a burning source moving at a constant speed, and validated through full-scale experiments on vertical cable tray fire with two typical cable-line spacing. The modified zone model can predict accurately the upper-layer temperature in the compartment. The accuracy is at least 25% higher than the model with fixed fire position. The measured temperature at different heights started to decrease at different times, which was due to the vertical spreading of the cable flame. For interface height, the relative error and normalized Euclidean distance in the time-varying fire position model can be improved by 50%.

A Method Evaluating Fire Hazard of Multiple-Layer Cable Tray and its Validation

2017 ◽  
Author(s):  
Xianjia Huang ◽  
Kun Bi ◽  
Jun Xiao ◽  
Lan Peng ◽  
He Zhu ◽  
...  
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Zone Model ◽  
Fire Source ◽  
Multiple Layer ◽  
Cat Model ◽  
Tray Fire

Multi-layer cable tray fire has special burning characteristics that the cable flame spreads horizontally along cable tray and propagates vertically from bottom layer to upper layer at the same time. With respect of accuracy and speed of calculation, simulation of multi-layer cable tray fire remains a challenge for fire models. In this paper, a method is proposed to simulate multi-layer cable tray fire. By developing a more accurate fire source description, this method can provide accurate simulation for multi-layer cable tray fire rapidly. In this method, Firstly, the heat release rate of each burning cable tray is evaluated by FLASH-CAT model. Based on the results from FLASH-CAT, a more accurate fire source definition for multiple lay cable tray is developed for zone model. Taking account of each burning cable tray considered as one fire source point, zone model is applied to predict the fire dynamics process. In order to validate this method, four-layer cable tray fire experiments and replicated experiments were carried out in a confined compartment. The histories of mass loss rate of cable tray and temperatures at the middle of compartment were recorded during the cable fire. From the replicated experimental results of total mass loss rate, it is concluded that the four-layer cable tray fire experiment has good repetition in this scenario. Vertical temperature profile shows that the fire circumstance generated by multiple-layer cable tray burning can be divided into upper hot layer and lower cool layer, which conforms to the basic assumption of zone model. As a consequence, the zone model can be applied to simulating multiple-layer cable tray fire. By comparing the experimental total heat release rate with predictions, it is found that characteristics of multiple-layer cable tray fire are well captured. On account of good prediction on overall heat release rate for multi-layer cable tray fire, predicted heat release rate for each burning cable layer by FLASH-CAT model is believed to be reliable. Then, each burning cable layer is set as one fire source and the heat release rate of each burning cable layer is input into zone model, respectively. The comparisons between simulations and experimental data show that the predicted upper layer temperature and lower layer temperature agree well with experimental data. As a result, it can be concluded that this method provides reliable prediction for multiple-layer cable tray fire rapidly.

Applicability of FLASH-CAT Model to Cable Tray Fire Modeling in Zone Model BRI2002

2021 ◽  
Author(s):  
KOJI SHIRAI ◽  
Koji Tasaka ◽  
Toshiko Udagawa
Keyword(s):  
Fire Modeling ◽  
Zone Model ◽  
Cat Model ◽  
Tray Fire
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