Near-field BLEVE overpressure effects: The shock start model

International audienceThis paper presents the results of a small scale experimental study of BLEVE overpressure effects. Testing consisted of a sealed aluminum tube (0.6 L) filled with either water or propane, being heated by a flame until the internal pressure led to catastrophic failure and explosion. Three parameters were controlled during the experiments: the failing pressure, the weakened length on the tube and the fill level. BLEVEs were obtained with tests involving water and propane. Blast gages and optical techniques were used to characterize the shock wave escaping from the failing tube. The results obtained suggest that the lead shock was primarily generated by the vapor space. Overpressure results obtained were compared with the predictions of existing models and found to be in reasonable agreement except for overpressures measured vertically above the cylinder where the overpressures were highest. A prediction model based on only vapor space characteristics was developed. Images show that the shock was fully formed at some distance away from the vessel opening and this was due to the non-ideal opening of the vessel. The model developed was based on the characteristics of the shock when fully formed away from the tube. These characteristics were defined using a combination of imaging, pressure measurements, and predictions from shock tube theory

Pool evaporation of hazardous substances in industrial storage dikes : a study on spatial and temporal temperature variations and its consequences

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.Storage of hazardous products requires utilizing containment systems such as diking against the unintended release of these materials. In case of volatile compounds, the liquid contained by the dike will offer a large surface for evaporation. It is of major importance to calculate the evaporation rate since evaporation may create a toxic or flammable cloud. This study aimed to study the temperature distribution in a liquid pool during evaporation. Vertical and horizontal temperature distributions were recorded by a series of thermocouples and an infrared camera. Evaporation experiments were performed with acetone in a wind channel facility. Vertical experimental data highlight a thin cold liquid layer at surface which remains during the evaporation and the liquid level decrease. This influences strongly the evaporation rate. On the horizontal consideration, surface gradients were observed when cavity flow occurs. These gradients are not believed to influence significantly the overall evaporation rate. A focus was done on the error induced when considering only mean liquid temperature instead of a distributed profile on several correlations from literature.The authors are grateful to the Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA) pour their financial support to this project.am201

A Dutch guideline for the treatment of scoliosis in neuromuscular disorders

<p>Abstract</p> <p>Background</p> <p>Children with neuromuscular disorders with a progressive muscle weakness such as Duchenne Muscular Dystrophy and Spinal Muscular Atrophy frequently develop a progressive scoliosis. A severe scoliosis compromises respiratory function and makes sitting more difficult. Spinal surgery is considered the primary treatment option for correcting severe scoliosis in neuromuscular disorders. Surgery in this population requires a multidisciplinary approach, careful planning, dedicated surgical procedures, and specialized after care.</p> <p>Methods</p> <p>The guideline is based on scientific evidence and expert opinions. A multidisciplinary working group representing experts from all relevant specialties performed the research. A literature search was conducted to collect scientific evidence in answer to specific questions posed by the working group. Literature was classified according to the level of evidence.</p> <p>Results</p> <p>For most aspects of the treatment scientific evidence is scarce and only low level cohort studies were found. Nevertheless, a high degree of consensus was reached about the management of patients with scoliosis in neuromuscular disorders. This was translated into a set of recommendations, which are now officially accepted as a general guideline in the Netherlands.</p> <p>Conclusion</p> <p>In order to optimize the treatment for scoliosis in neuromuscular disorders a Dutch guideline has been composed. This evidence-based, multidisciplinary guideline addresses conservative treatment, the preoperative, perioperative, and postoperative care of scoliosis in neuromuscular disorders.</p

Experimental analysis of local void fractions measurements for boiling hydrocarbons in complex geometry

International audienceThe present paper is part of a research program on two-phase flows and heat transfer studies in tube bundles. An experimental study was carried out to analyse the void fraction for vertical two-phase flows. Boiling across a horizontal tube bundle for three hydrocarbons (n-pentane, propane and iso-butane) under saturated conditions is investigated. The experiments were performed on a tube bundle with 45 plain copper tubes of 19.05 mm outside diameter in a staggered configuration with a pitch to diameter ratio of 1.33. An optical probe has been developed to determine the local void fraction at the minimum cross section between the tubes. The void fraction for the three hydrocarbons was found to be significantly less than the homogeneous prediction, and correlated well with the Zuber and Findlay (1965) model. A statistical analysis using Probability Density Functions (PDF) was performed to characterise the flow regimes. Two different flow regimes have been identified in the bundle, namely a "bubbly" and an "annular-dispersed" flow. A transition zone was evidenced by analysing the bubble size distribution. A comparison with the only pre-existing map, established for adiabatic air-water flow, shows that the transitions between the flow regimes do not correspond to our results in boiling case

Associated risks from a chemical slick, experimental study of fire and explosion consequences

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Associated risks from a chemical slick, experimental study of fire and explosion consequences

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Consequences of liquid jet breakup resulting from interaction with overpressure wave from domino effect

International audienceStorage tanks located on industrial sites are potential source term for leakages, followed by various consequences depending on the nature of the commodity: atmospheric dispersion, BLEVE, UVCE, toxic dispersion. Indeed, because of economic and security purposes, chemical substances are stored with different conditions of pressure, temperature and state. This study explores the consequences of a sudden opening of a storage tank due to an external aggression as a consequence from a previous event. Fragmentation of jets and droplets following the trigger event are thus evaluated. Indeed, increasing the exchange surface impacts the evaporation rate and can be an issue in case of toxic or flammable vapor. Laboratory experiments consisted in generating shockwave with an open ended shock tube to breakup liquid droplets with different viscosities. Size of fragmented droplets are optically measured by direct shadowgraphy. Shockwave is measured using both overpressure sensors and Edgerton retroreflective shadowgraphy. In these experiments, secondary breakups of a droplet into an important number of smaller droplets because of the shockwave induced flow are performed. Results are discussed in terms of velocity and size of droplets. Comparisons are made with existing fragmentation models such as Pilch and Erdman (1987) to provide up to date data with situations encountered in industrial risk evaluation

A New Approach to Analyze Chemical Releases Behavior in Water Column: High Speed Imaging

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