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Focused fluid flow is common in sedimentary basins worldwide, where flow structures often penetrate through sandy reservoir rocks, and clay‐rich caprocks. To better understand the mechanisms forming such structures, the impacts of the viscoelastic deformation and strongly nonlinear porosity‐dependent permeability of clay‐rich materials are assessed from an experimental and numerical modeling perspective. The experimental methods to measure the poroviscoelastic and transport properties of intact and remolded shale have been developed, and the experimental data is used to constrain the numerical simulations. It is demonstrated that viscoelastic deformation combined with nonlinear porosity‐dependent permeability triggers the development of localized flow channels, often imaged as seismic chimneys. The permeability inside a channel increases by several orders of magnitude compared to the background values. In addition, the propagation time scale and the channel size strongly depend on the material properties of the fluid and the rock. The time‐dependent behavior of the clay‐rich rock may play a key role in the long‐term integrity of the subsurface formations. Key Points: Clay‐rich rocks exhibit bulk viscous deformation in laboratory experimentsFocused fluid flow might develop through clay‐rich rock with implications for injectivity and leakage riskModel simulations based on experimental parameters give estimates for expected leakage rates [ABSTRACT FROM AUTHOR]

Karst collapse sinkholes (KCS) are a peculiar karst morphology resulting from the collapse of the topographic surface caused by subsurface karstification. In the Southern Apennines these phenomena are not randomly distributed but concentrate in several zones, named High Sinkhole Concentration Areas (HSCA), showing peculiar geological, structural and hydrogeological conditions. Gas vents and mineral springs occur widely in these HSCA, and are often stricty related to the KCS. Starting from four representative areas, the aim of this study is to ascertain if there is a genetic link between peculiar mineralogical vs geochemical features of densely fractured/altered rocky masses in KCS, gas vents/springs occurrences and diffuse hypogenic karstification. By means of a multidisciplinary approach (geological/geomorphological, mineralogical and geochemical) we selected and analysed four different kinds of samples related to KCS, gas vent and spring occurrences: (i) altered to deeply altered limestones sampled in the sinkholes; (ii) unaltered limestones sampled in close proximity to sinkhole areas; (iii) gypsum‐rich crusts/patinae, precipitated near to gas vents; (iv) gypsum‐ and calcite‐rich precipitates occurring at springs or inside caves. Among neoformed non‐carbonate minerals, gypsum is virtually ubiquitous, halides (fluorite, halite, sylvite) also occur in small to trace amounts. The mineralogical assemblages of the different samples show similarities and may also be compatible with hypogenic speleogenesis and with a process of alteration of the carbonate bedrock by means of uprising mineralizing fluids along structural discontinuities. Stable isotopic compositions (S, O) display strong variability in δ34S and δ18O for sulfate in the different areas, but a deep‐seated sulfur source can be hypothesized for many of the studied KCS‐related samples. This study has important implications for the relationships between areas of high concentration of sinkholes, regional fault systems, mechanical characteristics of rocks and the high seismicity typical of these areas of the Southern Apennines. © 2018 John Wiley & Sons, Ltd. This study focuses on areas whit high concentration of karst collapse sinkholes. Here sinkholes occur along damage zones and mineral/thermal springs and/or gas vents are always present in the vicinity. Peculiar mineral associations together geochemical data testify that the rock alteration can be explained by the activity of volcanogenic H2S uprising along faults, causing hypogene karst processes. [ABSTRACT FROM AUTHOR]

The transport equations for momentum, enthalpy, and chemical species are solved to simulate the reactive flow of polyurethane foam in a refrigerator cavity. The chemical reactions are described by a mechanism with four reactions and eight species. The numerical findings are also supported by dimensional arguments, which lead to important design attributes. Results prove that the model can be used not only to predict the flow features during the expansion of a multi‐component foam, but also to determine the locations and the size of the air vents to avoid air bubbles trapped during the solidification process. It appears that the distribution of the vent holes must be evenly balanced around the cabinet cavity, where the larger holes must be located at positions far from the injector. To prevent the formation of large air voids, which cannot reach the vent holes by the action of gravity, there must be additional holes located on the lower surfaces of the cavity to purge the air trapped. [ABSTRACT FROM AUTHOR]

Summary: Lithium‐ion batteries (LIBs) are extensively applied in various portable electronic equipment because of their high energy density power. However, accidents related to LIBs frequently occur. This study focuses on failure results, characteristics, and phenomena. Lithium‐ion batteries under different states of charge (SOCs) (0%, 30%, 50%, 80%, 100%, and 120%) at high temperatures have been investigated with the thermal abuse test. During the experiments, several typical failure processes were captured. According to the phenomena, 2 failure modes (smoke and jet fire) and 3 stages (primary reaction, tempestuous reaction in the middle time period, and extinguishing reaction in the final stage) were observed. A substantial amount of gas was vented, and jet fire was detected in the middle period. Only gas vented when the SOC was lower than 50%, whereas vented gas and jet fire were detected simultaneously when the SOC exceeded 50%. The results indicated combustible behaviors and exothermic reactions related to the SOC. An increase in the SOC caused a decrease in the thermal runaway initial temperature and the maximum increase in temperature. A higher SOC determined intense chemical reactions in the cell at higher temperatures, which caused a significant amount of materials to spew out of the batteries as well as additional mass loss. Relationships between failure characteristics and internal reactions were analyzed. The SOC should be lower than 50% in transportation or storage. The intercalated lithium capacities were the main reason for the series of domino reactions, which caused runaway in the terminal. These studies can serve as a reference for safety applications, transportation, and loss prevention in LIBs. [ABSTRACT FROM AUTHOR]

To improve the discharging efficiency of a gas explosion in an end-vented duct containing an obstacle, a side vent in different positions was introduced to a duct with the internal dimensions of 100 × 100 × 1000 mm 3 . The flame propagation characteristics and overpressure profiles of a methane/air explosion were analyzed to study the influence of side venting position on a gas explosion in an end-vented duct containing an obstacle. The experiment results showed that, the explosion can be efficiently discharged by a side vent in a duct containing an obstacle, and the discharging effect can be enhanced significantly with shortening the distance between the side vent and the ignition point. Besides, the relative position of a side vent and an obstacle has significant influences on the venting effect of a side vent. For a side vent located in front of an obstacle, the explosion can be effectively discharged by the side vent before the flame reaches the obstacle, thus dropping the incentive of the obstacle on flame propagation, and resulting in a great venting effect. Whereas for a side vent located behind an obstacle, before the flame reaches the side vent, the flame propagation will be strongly motivated by the obstacle and maintained at a high speed to pass the side vent, which is not conducive for a side vent to discharge the explosion. In addition, when the explosion overpressure induced by an obstacle is much higher, the discharging effect of a side vent on explosion overpressure can be further enhanced, resulting in a greater venting efficiency. [ABSTRACT FROM AUTHOR]

Summary: A ground experiment is established to investigate the pressure control performance of thermodynamic vent system (TVS) with HCFC123. Different influence factors, including tank pressure control bands, circulation volume flow rates, and heat loads, are investigated separately. The variations of tank pressure and fluid temperature are analyzed in different operation process. To compare the performance of TVS with that of direct venting, the tank heat leakage is solved with a quasi‐steady heat transfer model. With the actual penetration heat into tank determined, the performance comparison is made between direct venting and TVS. The results show that the increase rate of tank pressure rises with the heat load during the pressurization process. While the bulk fluid is still subcooled, great tank pressure control and fluid cooling could be obtained by increasing the circulation flow rate in the mixing injection process. With the cold capacity generated by the throttling process, both the vapor and liquid should be well cooled. For the case of No.3 to 4, as the refrigeration capacity of TVS could not eliminate the accumulated heat load timely, the fluid has a temperature increase in the early stage of throttling process. While for the case of No.6, with the fluid being cooled sufficiently, both the vapor and liquid have received great temperature control. Compared with the direct venting, the recovery ratio of venting gas loss generated by TVS ranges from 30% to 145%, which shows the TVS has a large advantage on exhaust saving. [ABSTRACT FROM AUTHOR]

The W-shaped regenerative technology-based radiant tube, a commonly adopted indirect-heating equipment item, has been well geared into various industries. This paper effectively amplifies our previous research and experimentally presents the research object, the W-shaped regenerative radiant tube (RRT), with 100 Kw rated power capacity and the performance tuned. Accordingly, four configuration schemes with the geometrically modified regenerative radiant tube burner (RRTB) are proposed in contrast to the previous one, to ascertain how the configuration of secondary stage air vent influences the performances of W-shaped RRT. Furthermore, how the switching time as an important operational parameter affects the performances of W-shaped RRT is meantime researched. As the results bespeak, in contrast to the previous one, the RRTB proposed in the experiment outstrips the previous one in the gained familiar M-shaped axial tube wall temperature profile while higher heating capacity, better tube wall temperature uniformity and lower NOX emission with this novel RRTB. The switching time increase from 30 s to 60 s lowers the overall tube wall temperature and NOX emission, whereas the maximum tube wall temperature approaches to the RRTB when the switching time exceeds 60 s. The attained experimental results lay the theoretical foundation for guiding industrial production of such heating equipment item. [ABSTRACT FROM AUTHOR]

In this work, a series of vented explosions in a typical compressor compartment are simulated using FLACS code to analyze the explosion venting characteristics. The effects of relevant parameters on the pressure peaks (i.e., overpressure and negative pressure) are also numerically investigated, including vent area ratio of the compressor compartment, vent activation pressure, mass per unit area of vent panels, and volume blockage ratio of obstacles. In addition, the orthogonal experiment design and improved grey relational analysis are implemented to evaluate the impact degree of these relevant parameters. The results show that the pressure peaks decrease with the increase of vent area ratio. There is an approximately linearly increasing relationship between the pressure peaks and the vent activation pressure. The pressure peaks increase with the mass per unit area of vent panels. The pressure peaks increase with the volume blockage ratio of obstacles. Based on the grey relational grade values, the effects of these relevant parameters on the overpressure peak are ranked as follows: volume blockage ratio of obstacles > vent activation pressure > vent area ratio > mass per unit area of vent panels. These achievements provide effective guidance for the venting safety design of gas compressor compartments. [ABSTRACT FROM AUTHOR]

To reduce the huge losses caused by natural gas explosions in transport pipelines, a small simulation pipeline with internal dimensions of 100 mm × 100 mm × 1000 mm was constructed, and the effects of the side venting position in the pipeline on methane explosion characteristics were studied. The experimental results showed that the venting effect of a side vent on flame propagation and explosion overpressure is not linearly increasing with shortening the distance between the side vent and the ignition point. The venting effect is significantly influenced by both the side venting position and the effect of an end vent. As the flame propagates upstream a side vent, the flame propagation is mainly affected by an end vent, and little affected by the side vent. Whereas when the flame propagates downstream the side venting position, the flame propagation velocity becomes to be gradually reduced by side venting effect. Besides, after a side vent is opened, the explosion overpressure is released by the side vent immediately, and the duration time of explosion overpressure is sensitive with the side venting position, but not in direct proportion with the peak overpressure. This illustrates the overpressure development affected by a side vent is influenced by both the side venting position and the interaction between the side vent and the end vent. [ABSTRACT FROM AUTHOR]

Safety vent is crucial to protect its users from unpredictable explosions caused by the increasing internal pressure of lithium-ion batteries. In order to prevent the explosion of the battery, a safety vent rupture is required when the internal pressure reaches a critical value. In conventional manufacturing, the cap plate and safety vent are fabricated separately and are then welded. In the current study, a manufacturing process, which includes backward extrusion and coining process, is suggested to produce an integrated safety vent, which also has the benefit of increasing the production efficiency. In order to design a backward extrusion process, an upper-bound analysis, which assumed a condition for the end of stroke, is used for the prediction of the forming load. Furthermore, the shape parameters of the coining process were determined as the stress of the notch part with the analytical model, which considers the stress concentration factor. The rupture test was performed to measure the rupture pressure of the safety vent. The results satisfied the required pressure of 8.5±0.5 kgf/cm. Finally, the results predicted from the analytical models were compared with those of the experiment. It was shown that the predicted rupture pressure was in good agreement with the experimentally measured ones, with a maximum error rate of 3.8 %. [ABSTRACT FROM AUTHOR]

Investigations have been undertaken at a 16 ha landfill capping to assess performance of the geomembrane component some 20–25 years after installation. The site has been the subject of quite extensive monitoring together with hydrological and other studies. Although environmental monitoring has shown no major concerns, there have been discrepancies in calculated water balance, leading to the recent investigations reported here. The capping, which is an interim solution, comprises about 1 m of cover soils over 0.375 mm LDPE geomembrane and surrounded by a perimeter drain. A robust final capping system will be constructed at a later date. Various remedial works were undertaken between 2010 and 2014 at the cap perimeter drains, also at a series of gas vent/probe holes through the geomembrane, to address the discrepancies in water balance, and the opportunity was taken to investigate the condition of the geomembrane which revealed a series of unanticipated gaps in the geomembrane. These investigations were subsequently extended over the whole cap to characterise the nature and extent of those defects and assess likely causes. The series of investigations reported here represents a significant case history, one of relatively few, and which describes: the approaches adopted to pursue the series of investigations; the findings of that work; options considered to address the issues; lessons learnt and the intervention strategies which are under consideration in response. It also has implications for other landfill caps and highlights the importance of construction processes including construction quality assurance to ensure the integrity of geomembranes following placement is not adversely affected, also the need for good records management to assess system performance in service and plan future interventions. [ABSTRACT FROM AUTHOR]

Vented dust explosion tests have been conducted in an experimental test silo in order to analyse the effect of the length/diameter ratio (L/D). The modular design of the silo permitted the assembling of four different vessels with different geometries. The tests were carried out with wheat flour and maize starch, using three different vent area sizes. The silo was equipped with instrumentation which recorded the pressure generated by the explosion at various points in the silo, as well as the instant when the vent panel opened. The length/diameter ratio has been included in the empirical correlations currently employed in standards EN 14491 and NFPA 68 for calculating the size of vents. However, there are marked differences between the two standards when applied to certain situations, in part due to a different vent area correction for slenderness. The results obtained in this experimental test programme were compared with the standards, and indicated the advisability of applying an increase in vent area in elongated vessels when L/D > 1, as stated in EN 14491. However, this same standard appears to apply an excessively severe correction in some situations. [ABSTRACT FROM AUTHOR]

Sediment samplings were performed to investigate the microphytobenthic community and photosynthetic activity adaptations to gas emissions and higher temperature in the Aeolian Islands during a three-year period (2012–2014). Higher microphytobenthic densities were recorded at the vent stations and values were even more pronounced in relation with high temperature. The gross primary production estimates strongly depended on microphytobenthic abundance values reaching up to 45.79 ± 6.14 mgC m −2 h −1 . High abundances were coupled with low community richness and diversity. Motile diatom living forms were predominant at all stations and the greatest differences among vent and reference stations were detected on the account of the tychopelagic forms. Morphological deformities and heavily silicified diatom frustules were also observed. A significant influence of the gas emission and high temperature on the phototrophic community was highlighted suggesting the Aeolian Islands as a good natural laboratory for studies on high CO 2 and global warming effects. [ABSTRACT FROM AUTHOR]

After a brief review of the global gas flaring and venting in oil industries including the emission of air pollutants and greenhouse gases and the amount of energy resources wasted, the focus is on Iran as a major oil producing and the world's third largest gas flaring country. Gas flaring is also practiced in natural gas industries, petroleum refining and petrochemical plants, although the level of emission is very low compared with emissions from oil production. The historical emission of these gases globally and Iran specifically, geographic location of emission sources, composition of gases, environmental impacts of gas flaring and the current and future projects to mitigate emissions are evaluated and discussed. Emission factor, an indication of efficiency in oil production, varies widely among oil production sites around the world, from near zero to more than 50 standard cubic meters of flare gas per barrel of oil produced with an average value of about 5. Iran's emission factor has fluctuated from around 1 to more than 16 according to the data of 1980–2012 with higher emission factors for offshore oil production. Data also show an increasing trend during 2010–2012 which could be due to the several technical reasons in oil productions as well as economic sanctions imposed on Iran. In addition, there is a great amount of uncertainty and discrepancies among various data sources in the emission factors due to the lack of actual measurements of the volume and composition of flare gas and the uncertainties in the data sources. This requires regulatory measures, investment by oil companies and international collaboration. The economic and technological constraints in implementing or delaying the gas flare reduction projects are evaluated and addressed, with successful case studies and best practices reviewed. In particular, the techno-economic constraints in implementing gas flaring reduction projects caused by international sanctions on Iran are analyzed. It is shown that despite the great loss of energy resources due to gas flaring, its adverse impacts on the local and global environment and the availability of the technologies to reduce emissions, flaring is still practiced in many parts of the world, which can be avoided if the necessary regulatory policies and measures are established at national levels and international collaboration can facilitate the investment by providing the required finance and technologies. At present the international activities to implement gas flaring project activities under the Clean Development Mechanism (CDM) of the Kyoto Protocol of the United Nations Framework Convention on Climate Change (UNFCCC) are very limited, but could be very effective in reducing emissions, if implemented. Due to the global demand and continued use of oil and gas in the next decades, there is an urgent need for reducing gas flaring emissions. This is not only the responsibility of the oil and gas companies, but also the responsibility of the national governments and the global community. [ABSTRACT FROM AUTHOR]

We studied asphalt deposits, oil seepage and gas venting during a multidisciplinary cruise in the Bay of Campeche, southern Gulf of Mexico. We conducted multibeam bathymetric mapping with an autonomous underwater vehicle and performed seafloor observations as well as sampling with a remotely operated vehicle. While previous studies concentrated on the asphalt volcano Chapopote Knoll, we confirmed that asphalt deposits at the seafloor occurred across numerous other knolls and ridges in water depths between 1230 and 3150 m; this is evidence that the outflow of heavy oil is a common component of hydrocarbon seepage of Campeche Knolls. The outflow of heavy oil either created whips or sheets floating in the water that subsequently descend and pile-up as meter high stacks at the seafloor over time or spread at the seafloor forming flows ranging from meters to tens of meters in diameter. Unlike seafloor-covering asphalts known from other continental margins, those in our study include relatively fresh material. Seafloor observations documented how chemosynthetic communities develop on the asphalts, with bacterial mats and juvenile vestimentiferan tubeworms colonizing the most recent flows. Gas bubble emissions were an additional widespread component of hydrocarbon seepage at Campeche Knolls. The hydrocarbon gas had thermogenic origins, as indicated by the composition (C1/C2-ratio: 14 to 185) and stable carbon isotopic signature of methane (δ13C-CH4: -45.1 to -49.8 ‰). Gas emissions were detected by multibeam echosounder at water depths as great as 3420 m over Tsanyao Yang Knoll. Gas emissions occurred at sites without large asphalt deposits (Tsanyao Yang Knoll) as well as through old, fragmented asphalts (Mictlan Knoll, Chapopote Knoll). The gas emissions feed gas hydrate deposits at shallow seafloor depth. Gas hydrate formed mounds that were ~ 10 m wide by several meters high in soft sediments and filled the space within fragmented asphalts. The largest gas hydrate mounds supported dense colonies of 1-2 m long tubeworms that covered areas > 100 m². These tubesworms grow with their posterior tubes implanted in a 5 to 10 cm thick reaction zone composed of authigenic carbonates, detritus, and microbial mats that overlie gas hydrate layers that were at least 2 m thick in places. This association between gas hydrates and vestimentifera has been noted in gas seeps at lesser depths, but was developed to an unequaled extent in the Campeche Knolls. Previous studies have documented oil slicks on the ocean surface across many sites in the region. This study found liquid oil emissions in diverse settings. Sites with oil seepage are characterized by oil-soaked sediments, chemosynthetic fauna with associated heterotrophs, and bacterial coatings. Gas bubble emissions and oil seepage occurred independent of asphalt deposits or through old, fragmented asphalts, indicating that presently active hydrocarbon seepage overprints older asphalt deposits. Campeche Knolls are unique in several aspects including the occurrence of recent flows of heavy oil, deep-water hydrocarbon seepage, with many species that are new to science. [ABSTRACT FROM AUTHOR]

This article adopted the method of numerical simulation to study heat release rate change rule and oxygen concentration variation when different opening size was changed within a small space, where there was a constant source of power in the space and an opening at the top level in the corner. Meanwhile, the constitutive factor affecting the burning mechanism of fire was further explored. As simulation results showed, (1) with the increase of opening size and larger amplitude of heat release rate vibration, In the later periods of the experiment, the frequency of heat release rate vibration is basically consistent with the frequency oxygen concentration changing at the nearby fire source. (2) With the increase of opening size, the amplitude of oxygen concentration changing under the bottom of opening is smaller, replenishment of outside cold air at larger opening is more stable, and oxygen quality replenished in the experimental box is increased. Meantime, oxygen quality replenished in the experimental box and participating in oxygen quality is increased obviously with the opening increase, opening size impacts the fire source combustion in the later period of the experiment directly. The oxygen concentration would decrease after a certain period of time in the fire development, unstable combustion “Ghosting flame” and “Oscillating fire” would happen due to the lack of oxygen when oxygen concentration near the combustion source is lower than 0.14. [ABSTRACT FROM AUTHOR]

Effect of vent burst pressure on internal pressure and flame evolution is experimentally investigated during explosion venting of rich hydrogen-air mixtures with equivalence ratio of 2 in a cylindrical vessel with a neck. Experimental results show that four pressure peaks are observed at the vessel exit under low vent burst pressures, corresponding to the following four successive stages: the vent failure, the venting of the burned gases, the maximum production rate of burned gas in vessel and the suction of gases into vessel. But under high vent burst pressure, the second and third pressure peaks disappear and the first one becomes dominant. The fourth pressure peak due to suction is kept around several kilopascals. The pressure in vessel is always characterized by single pressure peak which increases with the increase of the vent burst pressure. Under low vent burst pressures, the oscillation of internal flame due to flame-acoustic interaction results in oscillation of pressure rise rate in about 2000 Hz, and the oscillation nearly disappears under high vent burst pressures. The external flame speed does not decrease monotonously as the increase of distance away from the vent, and the maximum length of external flame is nearly independent of vent burst pressure. [ABSTRACT FROM AUTHOR]

Numerical and physical requirements to simulations of sub-sonic release and dispersion of light gas in an enclosure with one vent are described and discussed. Six validation experiments performed at CEA in a fuel cell-like enclosure of sizes H × W × L = 126 × 93 × 93 cm with one vent, either W × H = 90 × 18 cm (vent A) or 18 × 18 cm (B) or 1 cm in diameter (C), with a vertical upward helium release from a pipe of internal diameter either 5 mm or 20 mm located 21 cm above the floor centre, were used in a parametric study comprising 17 numerical simulations. Three CFD models were applied, i.e. laminar, standard k-ɛ , and dynamic LES Smagorinsky–Lilly, to clarify a range of their applicability and performance. The LES model consistently demonstrated the best performance in reproduction of measured concentrations throughout the whole range of experimental conditions, including laminar, transitional and turbulent releases even with large CFL numbers. The laminar and the standard k-ɛ models were under performing in the reproduction of turbulent and laminar releases respectively, as expected, as well as in simulation of transitional flows. The laminar model demonstrated high sensitivity to the CFL (Courant–Friedrichs–Lewy) number even below the best practices limit of 40. Three different computational domains and grids were used in order to clarify the influence of mesh quality on the capability of simulations to reproduce the experimental data. It is concluded that physically substantiated choice of CFD model, the control of the CFL number (and released gas mass balance where appropriate), and the mesh quality can have a strong effect on the capability of simulations to reproduce experiments and, in general, on the reliability of CFD tools for application in hydrogen safety engineering. [ABSTRACT FROM AUTHOR]

The objective of this study was to quantitatively investigate some characteristics of the smoke transportation in multi-floor buildings. Eight experiments were conducted for worst scenario. The effects of an open window in the burning room on the smoke transportation are also analyzed. The time-dependent smoke densities at 39 locations in a half-scale building with an atrium were measured through a digital smoke detector system. The results indicate that the chimney effect plays an important role in the smoke transportation in multi-floor buildings with atriums. For the effects of the open window, the results suggest that the smoke densities at most locations in the building increase earlier when a window is open but have a smaller peak value than those results in the cases without any outer vents. It is suggested that a building without vertical atrium would be safer than those with long ones. More attention should be paid to those spaces when the fire protection systems are designed for buildings with atriums. The data of the time-dependent smoke densities at tens of locations in the building are useful for the validation of smoke transportation models. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Existing knowledge on the distribution of mud volcanoes (MVs) and other significant fluid/free gas-venting features (mud cones, mud pies, mud-brine pools, mud carbonate cones, gas chimneys and, in some cases, pockmark fields) discovered on the seafloor of the Mediterranean Sea and in the nearby Gulf of Cadiz has been compiled using regional geophysical information (including multibeam coverage of most deepwater areas). The resulting dataset comprises both features proven from geological sampling, or in situ observations, and many previously unrecognized MVs inferred from geophysical evidence. The synthesis reveals that MVs clearly have non-random distributions that correspond to two main geodynamic settings: (1) the vast majority occur along the various tectono-sedimentary accretionary wedges of the Africa-Eurasia subduction zone, particularly in the central and eastern Mediterranean basins (external Calabrian Arc, Mediterranean Ridge, Florence Rise) but also along its westernmost boundary in the Gulf of Cadiz; (2) other MVs characterize thick depocentres along parts of the Mesozoic passive continental margins that border Africa from eastern Tunisia to the Levantine coasts, particularly off Egypt and, locally, within some areas of the western Mediterranean back-arc basins. Meaningfully accounting for MV distribution necessitates evidence of overpressured fluids and mud-rich layers. In addition, cross-correlations between MVs and other GIS-based data, such as maps of the Messinian evaporite basins and/or active (or recently active) tectonic trends, stress the importance of assessing geological control in terms of the presence, or not, of thick seals and potential conduits. It is contended that new MV discoveries may be expected in the study region, particularly along the southern Ionian Sea continental margins. [ABSTRACT FROM AUTHOR]

Abstract: A nonlinear pulse combustor model with an exhaust decoupler and vent pipe was solved using the Poincaré–Lindstedt perturbation analysis method. The solutions included expressions for the pressure in the combustion chamber and the exhaust decoupler respectively. Experiments were made to validate the theoretical analysis; results showed that an exhaust decoupler and a vent pipe can affect the frequency of the pulse combustor and the pressure in the exhaust decoupler (both amplitude and phase). There are five main dimensionless parameters: dimensionless exhaust decoupler volume v, dimensionless vent pipe length l, dimensionless vent pipe area s and dimensionless enthalpy h t0, h d0. Following the values of these five parameters, the working domain of the pulse combustor was divided into three parts: the inphase zone, critical interval and antiphase zone. In the critical interval domain, the pulse combustor cannot work stable. To make a pulse combustor work at the antiphase zone (recommended in engineering applications), a large exhaust decoupler volume, and fairly long vent pipe with a proper cross-section area are required. [Copyright &y& Elsevier]

A study of vented explosions in a length over diameter (L/D) of 2 in cylindrical vessel connecting with a vent duct (L/D = 7) is reported. The influence of vent burst pressure and ignition locations on the maximum overpressure and flame speeds at constant vent coefficient, K of 16.4 were investigated to elucidate how these parameters affect the severity of a vented explosion. Propane and methane/air mixtures were studied with equivalence ratio, Φ ranges from 0.8 to 1.6. It is demonstrated that end ignition exhibited higher maximum overpressures and flame speeds in comparison to central ignition, contrary to what is reported in literature. There was a large acceleration of the flame toward the duct due to the development of cellular flames and end ignition demonstrated to have higher flame speeds prior to entry into the vent due to the larger flame distance. The higher vent flow velocities and subsequent flame speeds were responsible for the higher overpressures obtained. Rich mixtures for propane/air mixtures at Φ = 1.35 had the greatest flame acceleration and the highest overpressures. In addition, the results showed that Bartknecht's gas explosion venting correlation is grossly overestimated the overpressure for K = 16.4 and thus, misleading the impact of the vent burst pressure. [ABSTRACT FROM AUTHOR]

VENT-II is a computer program designed to provide detailed analysis of natural-draft and induced-draft combustion appliance vent systems (i.e., furnace or water heater). This program is capable of predicting house depressurization thresholds that lead to backdrafting and spillage of combustion appliances; however, validation reports of the program being applied for this purpose are not readily available. The purpose of this article is to assess VENT-II's ability to predict combustion gas spillage events due to house depressurization by comparing VENT-II simulated results with experimental data for four appliance configurations. The results show that VENT-II correctly predicts depressurizations resulting in spillage for natural draft appliances operating in cold and mild outdoor conditions but not for hot conditions. In the latter case, the predicted depressurizations depend on whether the vent section is defined as part of the vent connector or the common vent when setting up the model. Overall, the VENT-II solver requires further investigation before it can be used reliably to predict spillage caused by depressurization over a full year of weather conditions, especially where hot conditions occur. [ABSTRACT FROM AUTHOR]

Abstract: Gob gas ventholes (GGVs) are used to control methane inflows into a longwall mining operation by capturing the gas within the overlying fractured strata before it enters the work environment. Using geostatistical co-simulation techniques, this paper maps the parameters of their rate decline behaviors across the study area, a longwall mine in the Northern Appalachian basin. Geostatistical gas-in-place (GIP) simulations were performed, using data from 64 exploration boreholes, and GIP data were mapped within the fractured zone of the study area. In addition, methane flowrates monitored from 10 GGVs were analyzed using decline curve analyses (DCA) techniques to determine parameters of decline rates. Surface elevation showed the most influence on methane production from GGVs and thus was used to investigate its relation with DCA parameters using correlation techniques on normal-scored data. Geostatistical analysis was pursued using sequential Gaussian co-simulation with surface elevation as the secondary variable and with DCA parameters as the primary variables. The primary DCA variables were effective percentage decline rate, rate at production start, rate at the beginning of forecast period, and production end duration. Co-simulation results were presented to visualize decline parameters at an area-wide scale. Wells located at lower elevations, i.e., at the bottom of valleys, tend to perform better in terms of their rate declines compared to those at higher elevations. These results were used to calculate drainage radii of GGVs using GIP realizations. The calculated drainage radii are close to ones predicted by pressure transient tests. [Copyright &y& Elsevier]

The effect of gas supply method on the performance of a single-chamber solid oxide fuel cell micro-stack and single cells was studied, and a novel gas supply method with separated gas vents in the gas tube was proposed. The traditional gas supply method was also investigated for comparison. Results showed that the single cells could obtain a uniform open-circuit voltage and power output by using the separated gas supply method. For the traditional gas supply method, the cell at the outlet position yielded inferior performance compared to that of the inlet cell. The gas flow rate showed a significant effect on the performance of the cells. Finally, the stack operated with the separated gas supply method produced a higher power output than that operated with the traditional gas supply method. [ABSTRACT FROM AUTHOR]

Abstract: Global flaring and venting of gas associated with petroleum production is a significant source of greenhouse gas emissions and airborne pollutants that has proven difficult to mitigate. This work examines the technical and economic potential for flaring and venting mitigation in a mature oil and gas producing region of the world. Using detailed monthly production data spanning the years 2002–2008 for 18,203 active production facilities, combined with geographic information system pipeline data, reservoir gas composition data, and cost data derived from industry sources, a case study was constructed to explore the technical and economic viability of further mitigation of flaring and venting associated with upstream oil and gas production in Alberta, Canada. Calculations were performed to evaluate the feasibility of mitigation via collection and compression of gas into pipelines to connect into existing pipeline networks. Four main calculation scenarios were considered, and for each, a series of Monte-Carlo analyses were performed to evaluate uncertainties and sensitivities to key calculation parameters. In all scenarios, the results reveal potentially significant opportunities for economically viable flare and vent mitigation that would yield substantial reductions in CO2 equivalent emissions. Because of the highly skewed distribution of gas volumes flared and vented at individual facilities, the results also show that solutions for comparatively small numbers of the largest facilities can offer large reductions in overall emissions from the sector. These results suggest that in a concerted effort to minimize carbon emissions in the upstream oil and gas industry, there is potential for significant near-term reductions using existing technology while research and development continues on more advanced methods such as carbon capture and storage. [Copyright &y& Elsevier]

An air venting element on microchannel, which can be controlled externally and automatically, was demonstrated for manipulating liquid plugs in microfluidic systems. The element's open and closed statuses correspond to the positioning and movement of a liquid plug in the microchannel. Positioning of multiple liquid plugs at an air venting element enabled the merging and mixing of the plugs. Besides these basic functions, other modes of liquid plug manipulations including plug partitioning, multiple plug mixing, and spacing adjustment between liquid plugs, were realized using combination of multiple elements. The structure, operation, and some functions of the element were demonstrated with a microfluidic chip application. The performances of the element including its failure modes, threshold flow rate, and structural optimization were also discussed. [ABSTRACT FROM AUTHOR]

Abstract: Sizing of horizontal ceiling vent in a tall atrium is usually based on vent flow models with unidirectional flow. This is only good for natural vents with large pressure differences between inside and outside. For low pressure differential across the horizontal ceiling vent as experienced in some atrium fires, bidirectional smoke flow rates were observed. The extraction rate through the vent would be reduced, giving poor performance of the smoke exhaust system. Bidirectional flow across a ceiling vent will be discussed in this paper. Models available in the literature will be briefly reviewed first. A new model was developed on studying effects of bidirectional flow across a horizontal vent on the smoke layer interface height. A critical pressure difference between inside and outside across the vent can be estimated on inducing bidirectional flows. The approach is illustrated with an example sizing calculation for a cubic atrium commonly found in Hong Kong. [Copyright &y& Elsevier]

The article focuses on several U.S. metal casting research projects funded and monitored by the American Foundry Society Inc. It provides information and current status of projects on various topics including machinability test for cast iron, core gas venting guidelines, and effects of variation in purity of silicon carbide on cupola furnaces.

Abstract: The runaway and blowdown of a non tempered hybrid chemical system (30% cumene hydroperoxide) exposed to an external heat input was investigated using a 0.1l scale tool. The maximum temperature and the maximum temperature rise rate were showed to be sensitive to the vent size. An Antoine type correlation between the maximum temperatures and pressures was observed. These resulted from the presence of vapour, mainly generated by the reaction products. Increasing the initial filling ratio resulted in an earlier vent opening but did not have a significant influence on the blow-down. Three types of mass venting behaviour were observed, when changing the vent area to volume ratio (A/V): [•] for large A/V, two-phase venting occurred from the vent opening until the end of the second pressure peak; [•] for medium A/V, two-phase venting occurred before and after the turnaround. The data seem to indicate that gas only venting occurred at turn-around; [•] for low A/V, two-phase venting was observed only after the second pressure peak. Two-phase venting after the second pressure peak probably results from the boiling of the hot reaction products at low pressure. [Copyright &y& Elsevier]

Abstract: Stereoscopic particle image velocimetry (SPIV) was applied to a fire-induced doorway flow to provide the velocity field for computations of the mass flow rate of air into an enclosure. For a flow of uniform temperature and concentration, the technique met all of the requirements to provide the best estimate of the mass flow rate. Simultaneous measurements of vertical distributions of velocity and temperature were also conducted with conventional vent flow techniques, bi-directional probes and thermocouples. Correction factors for mass flow rate computations using the conventional techniques were determined based on comparisons to the SPIV results. An average correction factor of unity was determined for the bi-directional probe technique thus further confirming the utilization of velocity distributions acquired using the technique in mass flow rate computations. An average correction factor of 0.69 was determined for mass flow rates computed from vertical temperature distributions inside and outside the enclosure. This agrees with average correction factors determined in previous studies. The results from the present study suggest that the conventional techniques, which are practical and affordable for routine fire testing, may be applied with greater confidence for fires up to 500kW. [ABSTRACT FROM AUTHOR]

Abstract: To minimize the possibility of flash gas generation at the inlet of the expansion device in multi air-conditioners, an accumulator heat exchanger is usually adopted. In this study, the heat transfer rate and subcooling difference in an accumulator heat exchanger were measured under various operating and geometric conditions. The effect of the operating conditions on the performance of the accumulator heat exchanger was analyzed for R-22, R-134a, and R-410A. The performance of the accumulator heat exchanger was also analyzed by varying diverse geometric parameters: the inner volume and the ratio of the diameter to height of the accumulator, and the diameter, length, and bending diameter of the inner heat exchanger. In addition, the flow of the refrigerant-oil mixture inside the accumulator was visualized. Based on the measured data, a dimensionless correlation for predicting the subcooling difference across the accumulator heat exchanger was developed. [Copyright &y& Elsevier]

A zero-power ballast control system that could be used to float and submerge a device solely using a gas source was built and tested. This system could be used to convey sensors, data loggers, and communication devices necessary for water quality monitoring and other applications by periodically maneuvering up and down a water column. Operational parameters for the system such as duration of the submerged and buoyant states can be varied according to its design. The gas source can be of any origin, e.g., compressed air, underwater gas vent, gas produced by microbes, etc. The zero-power ballast system was initially tested using a gas pump and further tested using gas produced by Clostridium acetobutylicum. Using microbial gas production as the only source of gas and no electrical power during operation, the system successfully floated and submerged periodically with a period of 30 min for at least 24 h. Together with microbial fuel cells, this system opens up possibilities for underwater monitoring systems that could function indefinitely. [ABSTRACT FROM AUTHOR]

Abstract: In a closed landfill, Japan, remedial actions have been undertaken to address the inadequate leachate collection and drainage systems. Part of this process included installing many passive gas vents in the landfill to promote stabilization of landfilled waste. This study focused on the gas velocity in vents by conducting tracer tests to elucidate the gas flow via passive gas vents. The gas composition and gas temperature in the vents was also measured. As the gas vents pass through the waste layer, both landfill gas and air flows through the vents. Therefore, passive gas vents can be used to aerate landfilled waste as well as to collect and release landfill gas. Aerobic biodegradation occurs when air migrates through the waste layer if organic matter is present; this increases the temperature of the waste layer. Inflow of air into the gas vents can occur at a wide range of depths, even 10–20m below ground level. Air is induced not from the surface of the landfill, but horizontally along the waste layer. The driving force of air induction from outside is a buoyancy effect caused by the temperature rise due to aerobic biodegradation. [Copyright &y& Elsevier]

Abstract: Carbon dioxide (CO2), carbon monoxide (CO), and mercury (Hg) emissions were quantified for two eastern Kentucky coal-seam fires, the Truman Shepherd fire in Floyd County and the Ruth Mullins fire in Perry County. This study is one of the first to estimate gas emissions from coal fires using field measurements at gas vents. The Truman Shepherd fire emissions are nearly 1400t CO2/yr and 16kgHg/yr resulting from a coal combustion rate of 450–550t/yr. The sum of CO2 emissions from seven vents at the Ruth Mullins fire is 726±72t/yr, suggesting that the fire is consuming about 250–280t coal/yr. Total Ruth Mullins fire CO and Hg emissions are estimated at 21±1.8t/yr and >840±170g/yr, respectively. The CO2 emissions are environmentally significant, but low compared to coal-fired power plants; for example, 3.9×106 t CO2/yr for a 514-MW boiler in Kentucky. Using simple calculations, CO2 and Hg emissions from coal-fires in the U.S. are estimated at 1.4×107–2.9×108 t/yr and 0.58–11.5t/yr, respectively. This initial work indicates that coal fires may be an important source of CO2, CO, Hg and other atmospheric constituents. [Copyright &y& Elsevier]

Abstract: The Tiptop underground coal-mine fire in the Skyline coalbed of the Middle Pennsylvanian Breathitt Formation was investigated in rural northern Breathitt County, Kentucky, in May 2008 and January 2009, for the purpose of determining the concentrations of carbon dioxide (CO2), carbon monoxide (CO), and mercury (Hg) in the vent and for measuring gas-vent temperatures. At the time of our visits, concentrations of CO2 peaked at 2.0% and >6.0% (v/v) and CO at 600ppm and >700ppm during field analysis in May 2008 and January 2009, respectively. For comparison, these concentrations exceed the U.S. Occupational Safety & Health Administration (OSHA) eight-hour safe exposure limits (0.5% CO2 and 50ppm CO), although the site is not currently mined. Mercury, as Hg0, in excess of 500 and 2100μg/m3, in May and January, respectively, in the field, also exceeded the OSHA eight-hour exposure limit (50μg/m3). Carbonyl sulfide, dimethyl sulfide, carbon disulfide, and a suite of organic compounds were determined at two vents for the first sampling event. All gases are diluted by air as they exit and migrate away from a gas vent, but temperature inversions and other meteorological conditions could lead to unhealthy concentrations in the nearby towns. Variation in gas temperatures, nearly 300°C during the January visit to the fire versus <50°C in May, demonstrates the large temporal variability in fire intensity at the Tiptop mine. These preliminary results suggest that emissions from coal fires may be important, but additional data are required that address the reasons for significant variations in the composition, flow, and temperature of vent gases. [Copyright &y& Elsevier]

Abstract: Leachate accumulated at the Nakazono Landfill in Asahikawa, Japan due to an inadequate leachate collection and drainage system. To reduce the level of leachate in the landfill and promote the stabilization of waste, many passive gas vents were installed in addition to leachate collection vaults. This study evaluated the distribution and movement of leachate in the landfill by measuring leachate levels and conducting tracer tests in the gas vents. Water levels varied widely among gas vents and depended mainly on the vent’s original ground level and depth. Leachate velocity varied greatly; it was high in the upper layers of the saturated zone in a gas vent, but this was only a superficial velocity caused by inflow from unsaturated layers. A sharp decrease in total organic carbon observed in most gas vents after installation was likely due to the effect of aerobic biodegradation in the unsaturated waste layer. This effect was limited to a small aerobic zone around the gas vent. [Copyright &y& Elsevier]

Abstract: Direct methanol fuel cells have potentially high energy density if the balance of plant and fuel losses can be kept to a minimum. CO2 accumulation in the fuel tank can lower the efficiency and performance of closed-tank methanol fuel cells. This report discusses the implementation of a passive CO2 vent fabricated with poly(1-trimethyl silyl propyne) and 1,6-divinylperfluorohexane. The performance of the membrane as a selective vent for carbon dioxide in the presence of methanol has been studied at various operating conditions. First, the selectivity of the vent membrane improved with temperature. Second, the activation energy for permeation through the polymer membrane corresponded to diffusion controlled transport of CO2 and sorption controlled transport for methanol vapor. The activation energy for CO2 transport through the poly(1-trimethyl silyl propyne) and 1,6-divinylperfluorohexane membrane was less than that for a pure poly(1-trimethyl silyl propyne) membrane. Finally, the polymer had a high selectivity for carbon dioxide compared to both liquid and vapor phase methanol. [Copyright &y& Elsevier]

Abstract: About 120 gas seepage vents were documented along the west and southwest coast of the Hainan Island, South China Sea, in water depths usually less than 50m. The principal seepage areas include the Lingtou Promontory, the Yinggehai Rivulet Mouth, Yazhou Bay, the Nanshan Promontory and the Tianya Promontory. They occur along three major zones, reflecting the control by faults and lateral conduits within the basement. It is estimated that the total gas emission from these seepage vents is 294–956m3/year. The seepage gases are characterized by a high CH4 content (76%), heavy δ 13C1 values (−38 to −33‰) and high C1/C1–5 ratios (0.95–1.0), resembling the thermogenic gases from the diapiric gas fields of the Yinggehai Basin. Hydrocarbon–source correlation shows that the hydrocarbons in the sediments from seepage areas can be correlated with the deeply buried Miocene source rocks and sandstone reservoirs in the central depression. The 2D basin modeling results based on a section from the source rock center to the gas seepage sites indicate that the gas-bearing fluids migrated from the source rocks upward through faults or weak zones encompassed by shale diapirism or in up-dip direction along the sandstone-rich strata of Huangliu Formation to arrive to seabed and form the nearshore gas seepages. It is suggested that the seepage gases are sourced from the Miocene source rocks in the central depression of the Yinggehai Basin. This migration model implies that the eastern slope zone between the gas source area of the central depression and the seepage zone is also favorable place for gas accumulation. [Copyright &y& Elsevier]

It has recently been recognized that, in addition to low concentrations of widespread natural gas hydrate associated with bottom-simulating seismic reflectors, highly concentrated hydrate can occur in local seafloor fluid venting structures. Such structures extend upward into the regional gas hydrate stability field and sometimes allow gases to escape into the overlying ocean. These hydrate-choked chimneys are especially prospective as an energy resource because they contain high hydrate concentrations. Furthermore, they may be one of the most important conduits into the ocean-atmosphere system for deep methane. We present an analysis of two-dimensional seismic reflection data from offshore Korea that give a complete picture of gas migrating from a deep source zone to feed hydrate-choked vent structures at the seafloor. The gases migrate upward through networks of fractures imaged as steep amplitude striations in both diffuse and concentrated distributions. We present an example of a high-flux gas vent fed through fracture swarms emanating from a 10-15-km-wide catchment zone of source gases residing 3-4 km below the seabed. The geological context and the inferred distribution of hydrate within this feature are consistent with recent models in which seabed gas venting is a consequence of elevated pore fluid salinities that are produced by a high flux of gases migrating independently of the pore water. In contrast, a nearby vent that is not plumbed into the same high-flux system appears to be dominated more by gas-rich liquids. We present these two vent structures as type cases for high- and lowflux fluid escape systems in the seabed. Furthermore, we suggest that since the amount of gas trapped as hydrate within the vents is small compared with the amount in the underlying reservoir, the greatest risk for increased methane input to the atmosphere associated with climate-driven oceanic warming is not the melting of hydrate, but an increase in the number of deep reservoirs able to vent gases through the seabed that occurs as the regional gas hydrate stability zone thins. [ABSTRACT FROM AUTHOR]