119,506 research outputs found
Portable water mist fire extinguishers as an alternative for Halon 1211
No full textThis paper assesses the suitability of portable water mist fire extinguishers as an alternative for Halon 1211 to supress flammable liquid fires. It reports the findings of full-scale fire tests to investigate the capability and limitation of portable water mist fire extinguishers in suppressing various types of fires including cooking oils, n-heptanes, diesel fuels and wood cribs. It discusses the impact of key water mist characteristics such as flow rate, spray angle and droplet size, discharge pressures, nozzle discharge angles, as well as the types of nozzles on fire suppression, and it presents a prototype water mist fire extinguisher for multipurpose fire protection.Dans ce document, on tente de d\ue9terminer si l'extincteur par brouillard d'eau du type portatif convient comme solution de rechange au halon 1211 pour \ue9teindre les feux de liquide inflammable. On y fait \ue9tat des r\ue9sultats d'essais au feu en vraie grandeur ayant pour but d'\ue9valuer les capacit\ue9s et les limites des extincteurs par brouillard d'eau portatifs dans la lutte contre divers types de feux, y compris les feux d'huile \ue0 friture, de n-heptane, de carburant diesel et de b\ufbcher. Y sont examin\ue9e l'incidence sur l'efficacit\ue9 extinctrice de caract\ue9ristiques cl\ue9s du brouillard d'eau comme le d\ue9bit, l'angle du jet, la grosseur des gouttelettes, les valeurs de pression de refoulement, les angles de projection \ue0 la buse et les types de buses, et pr\ue9sent\ue9 un prototype d'extincteur \ue0 brouillard d'eau con\ue7u pour la protection contre l'incendie \ue0 usages multiples.Peer reviewed: YesNRC publication: Ye
Halon alternative: water mist
No full textRecent research at Canada's Institute for Research in Construction (IRC) will have implications for the use of water-mist systems as a replacement for halon in certain circumstances. Following the ban on halon production by the Montreal Protocol, IRC's Fire Risk Management Program, in partnership with the Department of National Defence (DND), has been looking for alternative fire-suppression systems to use as replacements for existing equipment and in future designs. It is of primary importance that the use of such systems does not compromise the firefighting effectiveness currently provided by halon, have negative implications for the environment nor create unacceptable safety risks.De r\ue9cents travaux de recherche men\ue9s \ue0 l'Institut de recherche en construction auront, dans certains cas, des r\ue9percussions sur le remplacement des syst\ue8mes au halon par des syst\ue8mes d'extinction par brouillard d'eau. \uc0 la suite de l'interdiction impos\ue9e sur la production de halon par le Protocole de Montr\ue9al, on effectue dans le cadre du programme Gestion des risques d'incendie de l'Institut de recherche en construction, en collaboration avec le minist\ue8re de la D\ue9fense nationale, des recherches sur des syst\ue8mes d'extinction qui permettraient de remplacer les \ue9quipements d\ue9j\ue0 install\ue9s et qui seraient int\ue9gr\ue9s aux nouveaux syst\ue8mes d'extinction. Il est essentiel que de tels syst\ue8mes soient au moins aussi efficaces dans la lutte contre les incendies que les syst\ue8mes au halon, qu'ils ne nuisent pas \ue0 l'environnement et qu'ils ne cr\ue9ent pas de risques inacceptables au chapitre de la s\ue9curit\ue9.NRC publication: N
Flow of nitrogen-pressurized Halon 1301 in fire extinguishing systems
No full textHalon 1301 which is a halocarbon fire extinguishing agent (CBrF3) used by the U.S. Army for vehicle fire suppression is discussed. Halon 1301 is discharged under nitrogen pressure, and the Halon-nitrogen mixture is a two phase, two component mixture that obeys compressible fluid laws and exhibits choking effects. A computer model was developed to analyze the discharge of Halon and nitrogen from a storage bottle through pipes and nozzles. The model agrees well with data from Halon 1301 discharge tests. The discharge time depends mainly on nozzle area and pipe volume, for given initial conditions. Graphs were developed for estimating discharge times. A nozzle employing multiple concentric converging/diverging nozzles was developed which gave hemispherical coverage
Review of alternative streaming agents for halon 1211
No full textSince 1994, the National Research Council of Canada (NRC) and the Department of National Defence (DND) have established a research partnership under the Halon Alternatives Performance Evaluation (HAPE) program to respond to the production ban on ozone-depleting halons by the Montreal Protocol. Previous HAPE projects focused on Halon 1301 alternatives for total flooding fire suppression applications. It was recognized that there is a need for information on suitable alternative streaming agents to replace Halon 1211. A new project was initiated to review the information on alternative streaming agents. This involves the review of new technologies that are under development as well as the review of currently available halocarbon streaming agents. This paper provides summary of the project findings on alternative streaming agents for Halon 1211. Compared to systematic and extensive work carried out on total flooding agents worldwide, performance evaluation of streaming agents is lacking.En 1994, le Conseil national de recherches du Canada (CNRC) et le minist\ue8re de la D\ue9fense nationale (MDN) ont mis sur pied un partenariat de recherche pour \ue9valuer la performance des produits de remplacement du halon, un compos\ue9 responsable de l'appauvrissement de la couche d'ozone dont la production a \ue9t\ue9 bannie par le Protocole de Montr\ue9al. Les projets pr\ue9c\ue9dents men\ue9s dans le cadre de ce programme mettaient l'accent sur les produits de remplacement du halon 1301 pour des applications d'extinction d'incendie par noyage total. Toutefois, on a aussi identifi\ue9 la n\ue9cessit\ue9 d'obtenir plus d'information sur les agents de dispersion utilis\ue9s pour remplacer le halon 1211. Un nouveau projet a donc \ue9t\ue9 mis en ?uvre pour examiner de nouveau ces agents de remplacement. Ce projet comprend une \ue9valuation des nouvelles technologies qui sont en cours de d\ue9veloppement, de m\ueame qu'une \ue9valuation des agents de dispersion aux halocarbures actuellement disponibles. Cet article r\ue9sume les r\ue9sultats de l'\ue9valuation des agents de dispersion de remplacement du halon 1211. M\ueame si des travaux syst\ue9matiques et approfondis ont \ue9t\ue9 men\ue9s sur l'efficacit\ue9 des agents de dispersion de remplacement pour l'extinction par noyage total, on sait en fait tr\ue8s peu de choses sur la performance de ces agents.Peer reviewed: YesNRC publication: Ye
Use of computer modelling to evaluate the performance of halon alternatives - a literature review
No full textComputer modeling represents a relatively new methodology in the search for halon alternatives. The purpose of this report is to investigate the feasibility of using computer modeling to make the selection of halon alternatives more efficient and effective. This report reviews the current developments in computer modeling and the existing kinetic databases for hydrocarbon fuels and halon alternatives. The range of application of the computer models and their limitations are discussed in the report.This review shows that computer modeling is capable of accurately reproducing some aspects of fire phenomena, and that it is being regarded as another method for evaluating agent performance. Such a ?test? is better defined and much easier to carry out, in comparison with a full-scale fire test.La mod\ue9lisation repr\ue9sente une m\ue9thodologie relativement nouvelle qui est employ\ue9e dans la recherche de solutions de rechange \ue0 l?utilisation du halon. Le pr\ue9sent rapport a pour objet d?examiner la faisabilit\ue9 de l?utilisation de la mod\ue9lisation aux fins de la s\ue9lection de solutions de rechange au halon qui offrent une efficacit\ue9 et un rendement sup\ue9rieurs. On examine dans ce rapport les d\ue9veloppements actuels en mati\ue8re de mod\ue9lisation ainsi que les bases de donn\ue9es d?analyse cin\ue9tique existantes dans le domaine des solutions de remplacement des combustibles hydrocarbon\ue9s et du halon. On traite dans ce rapport de la gamme des applications des mod\ue8les et de leurs limites. Cet examen indique que la mod\ue9lisation peut reproduire avec pr\ue9cision certains aspects de ph\ue9nom\ue8nes li\ue9s aux incendies, et qu?elle est actuellement per\ue7ue comme une m\ue9thode suppl\ue9mentaire permettant d?\ue9valuer la performance des agents. Un pareil \uab test \ubb se r\ue9v\ue8le mieux d\ue9fini et beaucoup plus facile \ue0 ex\ue9cuter que l?essai de r\ue9action au feu en vraie grandeur.Peer reviewed: NoNRC publication: Ye
A literature review of the impact of thermal decomposition products generated by halon replacements on electronic equipment
No full textThis literature review provides information on the impact of thermal decomposition products generated during fire suppression by halon replacements on electronic facilities. It includes a review of the thermal decomposition products formed during fire suppression and the potential corrosive damageto electronic facilities caused by halon replacements. The factors that contribute to the corrosive damage to electronic facilities, such as the concentration of corrosive species, the exposure period, the nature of the combustible materials involved in the fire, the temperature and humidity in the compartment, and the type of equipment exposed, are identified. Previous experimental studies on the impact of HF corrosion to the electronic equipment, including laboratory-scale and full-scale tests, arealso reviewed and discussed. Based on this review, recommendations are provided for minimizing HF corrosive damage to the electronic equipment and some issues for further study are identified.Cette analyse documentaire fournit des donn\ue9es sur l?incidence qu?ont sur les installations \ue9lectroniques les produits de la d\ue9composition thermique g\ue9n\ue9r\ue9s, durant les op\ue9rations d?extinction des incendies, par les agents de substitution du halon. Elle inclut un examen des produits de d\ue9composition thermique qui sont form\ue9s pendant l?extinction et des dommages de nature corrosive aux installations \ue9lectroniques que peuvent potentiellement causer les agents de substitution du halon. Sont identifi\ue9s les facteurs qui contribuent aux dommages corrosifs des installations \ue9lectroniques, comme la concentration d?esp\ue8ces corrosives, la p\ue9riode d?exposition, la nature des mati\ue8res combustibles touch\ue9es par le feu, la temp\ue9rature et l?humidit\ue9 dans le compartiment, ainsi que le type de mat\ue9riel expos\ue9. Les \ue9tudes exp\ue9rimentales ant\ue9rieures portant sur l?incidence de la corrosion du mat\ue9riel \ue9lectronique caus\ue9e par le fluorure d?hydrog\ue8ne, y compris les essais en laboratoire et les essais en vraie grandeur, font \ue9galement l?objet d?un examen et d?une discussion. \uc0 la lumi\ue8re de cet examen, on fournit des recommandations en vue de la r\ue9duction au minimum de l?endommagement des mat\ue9riels \ue9lectroniques dus \ue0 la corrosion par le fluorure d?hydrog\ue8ne, et l?on identifie certaines questions \ue0 examiner comme compl\ue9ment d?\ue9tude.Peer reviewed: NoNRC publication: Ye
Numerical analysis of a 3-D printed porous trailing edge for broadband noise reduction
No full textLattice Boltzmann simulations were carried out to investigate the noise mitigation mechanisms of a 3-D printed porous trailing-edge insert, elucidating the link between noise reduction and material permeability. The porous insert is based on a unit cell resembling a lattice of diamond atoms. It replaces the last 20 % chord of a NACA 0018 at zero angle-of-attack. A partially blocked insert is considered by adding a solid partition between 84 % and 96 % of the aerofoil chord. The regular porous insert achieves a substantial noise reduction at low frequencies, although a slight noise increase is found at high frequencies. The partially blocked porous insert exhibits a lower noise reduction level, but the noise emission at mid-to-high frequency is slightly affected. The segment of the porous insert near the tip plays a dominant role in promoting noise mitigation, whereas the solid-porous junction contributes, in addition to the rough surface, towards the high-frequency excess noise. The current study demonstrates the existence of an entrance length associated with the porous material geometry, which is linked to the pressure release process that is responsible for promoting noise mitigation. This process is characterised by the aerodynamic interaction between pressure fluctuations across the porous medium, which is found at locations where the porous insert thickness is less than twice the entrance length. Present results also suggest that the noise attenuation level is related to both the chordwise extent of the porous insert and the streamwise turbulent length scale. The porous inserts also cause a slight drag increase compared to their solid counterpart. Wind Energ
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Direct P-Wave Seismic Noise Interferometry for Groundwater Monitoring: A Modelling Study
No full textIn this study, we monitor the depth variation of an unconfined aquifer by applying seismic noise interferometry to synthetic data modelled with a 2D finite-difference software. We consider two models with the same subsurface geological structure, but with different water table levels representing two monitoring periods. The receivers are placed at the topographic surface and collect the seismic signals generated by a source located at the bottom of the aquifer to simulate a pumping system. First, cross-correlation of seismic traces with a reference one is used to produce interferograms (i.e., virtual surveys) for both the tested models. Then, direct P-wave arrivals identified in the two interferograms are compared through the stretching technique in order to estimate the relative velocity changes (dv/v). Finally, the estimated dv/v values are related to theoretical ones obtained using a reference subsurface model to produce the water level depth in the considered monitoring period.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Applied Geophysics and Petrophysic
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