Water Curtain Research Articles

Determination of groundwater flow regimes in underground storage caverns using tritium and helium isotopes

Understanding groundwater flow and chemical transport is crucial for operating underground storage caverns. Groundwater flow in the study area is mainly affected by cavern operating conditions, and groundwater chemistry in the study area is modified by disinfection activities for removing possible biological clogging and by mixing with cement pore water. It is significant to discern these two effects because wells affected by the disinfection activities, in particular, may have hydrological connections with water curtains in which disinfectant water was injected to remove the biological clogging. Concentration of tritium (3H) and helium isotopes (4He), and groundwater chemical compositions were used to confirm that there are hydrological connectivities between the water curtain and the well. Groundwater along the fault areas contains low total dissolved solid (TDS) and high 3H, suggesting that the faults may act as fast flow conduits, which is not inconsistent with previous studies. Certain diagnostic conditions (high concentrations of Na+, Cl− and TDS and high pH) are presumed by the effect of disinfection activity, indicating that there are hydrological connections between the water curtain and the wells. This hypothesis is valid in YK2U and YK2L, but is not in YK12L, implying a closed system or an immobile water to explain the isotopic results.

Attenuation of solar radiation by a water mist from the ultraviolet to the infrared range

A model is developed for the hemispherical transmittance of direct and scattered solar radiation from a cloudless atmosphere by a mist layer of water droplets in order to investigate the potential of water misting systems to serve as a protection from solar irradiation with particular emphasis on harmful UV radiation. The proposed model is based on published spectral experimental data for solar irradiation, Mie theory for interaction of the radiation with single spherical droplets, and radiative transfer theory. Known limiting solutions are employed to simplify the Mie calculations. The modified two-flux approximation is used to account for both direct and diffuse irradiation in lieu of a numerical solution for the full radiative transfer equation in anisotropically scattering media. The role of the governing parameters of a disperse water curtain of water droplets, water content, and droplet size for sample conditions is studied in some detail, particularly in the near-ultraviolet part of the spectrum where radiation can result in human tissue damage.

Forced dispersion of LNG vapor with water curtain

Installation of effective safety measures to prevent and mitigate an accidental LNG release is critical. Water curtains are usually inexpensive, simple and reliable and currently have been recognized as an efficient technique to control and mitigate various hazards in the process industries including LNG industry. Actions of a water spray consist of a combination of several physical mechanisms. Detailed analysis of the complex mechanisms and the effects of water spray features to control and mitigate potential LNG vapor cloud are still unclear. This paper discusses the experimental research conducted by MKOPSC to study the physical phenomena involved and the effect of different types of water curtains parameters when applied for LNG vapor. The data from medium scale out-door experiments at the Brayton Fire Training School (BFTF), Texas, are summarized here to understand the relative importance of induced mechanical mixing effects, dilution with air, and heat transfer between water droplets and the LNG vapor. Field test results have determined that water curtains can reduce the concentration of the LNG vapor cloud. Due to the water curtain mechanisms of entrainment of air, dilution of vapor with entrained air, transfer of momentum and heat to the gas cloud, water curtain can disperse LNG vapor cloud to some extent.

Water Mist and Radiation Interactions: Application to a Water Curtain Used as a Radiative Shield

A numerical simulation has been carried out on a water curtain used as a radiative shield against a source of thermal radiation. An Eulerian-Lagrangian code for the dynamics of the mist is combined to a Monte Carlo simulation of the radiative transfer in the air-droplet medium. Various attenuation efficiencies have been evaluated through comparisons on an academic reference case where multiple injections are generated on a line in order to build a water curtain. The aim of this study is to pinpoint more efficient configurations improving the radiative attenuation in saving the used water amount.

Higher Precision Forming by Laser Peening under Pre-Bending Die

The mechanism of laser peening forming was analyzed and the precision of laser peening forming was tested by experiments. In the experiments, the parameters of Nd: Glass laser were as following: the wavelength 1.06μm, the pulse duration 23 ns, the output power 32 J. The material of sample was aeronautic aluminum alloy LY12CZ, and its size was 150mm×90mm×3.5mm. The sample surface was coated with black paint and flowing water curtain served as overlay. The curvature radius of pre-bending die was 500mm. The shape of deformed plate after laser peening was measured. The experimental data indicate that the curvature radius of specimen after laser peening under elastic pre-bending state is 1872.13mm, and the maximum difference value in the R direction is 0.79mm. Comparing with the traditional forming processes, it is a high-precision forming technology.

Multivariate statistical analysis for groundwater mixing ratios around underground storage caverns in Korea

Understanding groundwater flow and chemistry is crucial to operate underground storage caverns because the groundwater flow and chemistry is mainly affected by the cavern operating conditions. Both classical (for example, graphical Durov diagram) and multivariate statistical methods [principal component analysis, (PCA) and cluster analysis, (CA)] were used to trace an effect of the injection of a sodium hypochlorite (NaOCl) disinfectant solution into the water curtain on the chemical compositions of groundwater and to calculate groundwater mixing ratio around liquefied petroleum gas underground storage caverns. Based on both hydrochemical analysis and statistical analysis, the groundwater samples in the study area were divided into four groups. Both CA and an end member mixing (EMM) calculation using the PCA results indicate that the chemical compositions of seepage water have been mostly influenced by waters from the water curtains. The propane seepage water is most influenced by the monitoring wells in the water curtain, with the largest mixing portion (34.2%), which indicates that a good performance of the water curtains in the propane area. The EMM model from the PCA results is used to calculate the mixing ratio and to identify the chemical evolution of groundwater evolution, providing clues to the groundwater flow and transport system around the underground storage caverns.

The solid particle erosion behaviour of dental enamel using a novel air abrasion system

The erosion rate of the enamel of human premolars, molars and canines was measured at various angles of attack using a dental air abrasion unit equipped with a novel particle containment system consisting of a conical water spray surrounding the central air/particle jet. This water curtain minimised the amount of airborne abrasive particles and erosion debris. No statistically significant difference in erosion rate was found between samples blasted with or without the particle containment system. The dental enamel was found to behave in a brittle erosive manner, exhibiting a maximum in erosion rate with the abrasive jet oriented perpendicular to the surface. The observed dependency of erosion rate on the type of tooth could be explained on the basis of differing hardness. Artificial dental block samples showed significantly lower erosion rates compared to human dental enamel, implying that they are not suitable for simulating the solid particle erosion behaviour of teeth.

Experimental study of water curtain performance for gas storage in an underground cavern

An artificial water curtain system is composed of a network of underground galleries and horizontal boreholes drilled from these galleries. Pre-grouting measures are introduced to keep the bedrock saturated all the time. This system is deployed over an artificial or natural underground cavern used for the storage of gas (or some other fluids) to prevent the gas from escaping through leakage paths in the rock mass. An experimental physical modeling system has been constructed to evaluate the performance of artificial water curtain systems under various conditions. These conditions include different spacings of caverns and cavern radii located below the natural groundwater level. The principles of the experiment, devices, design of the physical model, calculation of gas leakage, and evaluation of the critical gas pressure are presented in this paper. Experimental result shows that gas leakage is strongly affected by the spacing of water curtain boreholes, the critical gas pressure, and the number and proximity of storage caverns. The hydraulic connection between boreholes is observed to vary with depth or location, which suggests that the distribution of water-conducting joint sets along the boreholes is also variable. When designing the drainage system for a cavern, drainage holes should be orientated to maximize the frequency at which they encounter major joint sets and permeable intervals studying in order to maintain the seal on the cavern through water pressure. Our experimental results provide a significant contribution to the theoretical controls on water curtains, and they can be used to guide the design and construction of practical storage caverns.

FIRE SAFETY ASPECTS OF REFUGE FLOORS IN SUPERTALL BUILDINGS WITH COMPUTATIONAL FLUID DYNAMICS

High-rise buildings in many big cities in the Far East, including Hong Kong, call for refuge floors as a matter of both practicality and compliance with regulations. Even though many countries’ fire codes are not clear in spelling out the necessity for refuge floors, it is accepted within construction that such floors are essential in resisting fire, allowing users a means of escape and allowing emergency services a means of access to stricken buildings. This paper discusses the reasons behind providing refuge floors, while also considering related fire safety provisions, such as their enclosure behind fire‐resistant construction or the protection of their openings behind a water curtain. Our discussion takes a tall building with balconies as a test example of refuge floors, running a hazard assessment based on Computational Fluid Dynamics assuming a fire of the broadly accepted level of 2 MW. The paper concludes that the design of the building's façade finally determines whether or not a refuge floor and associated fire safety provisions, such as a water curtain, can be waived. As the flat modelled used to store a high amount of combustibles up to 1135 MJm−2, the breaking of large area of glass window could lead to a major conflagration. The consequences of a scenario with a fire of 25 MW are also discussed. Santrauka Daugelio Tolimųjų Rytų didžiųjų miestų aukštuminiuose pastatuose, taip pat ir Honkongo, reikalingi saugos aukštai, paisant praktiškumo ir atitikimo reikalavimus. Netgi jei daugelio šalių gaisrinės saugos normos aiškiai nereglamentuoja būtinybės įrengti saugos aukštų, konstrukciniu požiūriu tokie aukštai yra būtini gaisrinei saugai, užtikrinant pastato naudotojams evakuacijos galimybę ir avarinėms tarnyboms patekimą į pastatą. Straipsnyje aptariamos saugos aukštų įrengimo priežastys, taip pat įvertinamos susijusios tokios gaisrinės saugos priemonės, kaip atsparių ugniai konstrukcijų įrengimas arba angų apsauga vandens užuolaida. Nagrinėjamas aukštuminis pastatas su balkonais, kaip eksperimentinis saugos aukštų pavyzdys, įvertinant pavojų. Tai daroma naudojant skysčių dinamikos modeliavimą ir plačiai pripažintą 2 MW galios gaisrą. Straipsnyje daromos išvados, kad pastato fasado projektiniai sprendiniai daro įtaką, ar saugos aukštai ir susijusios tokios gaisrinės saugos priemonės, kaip vandens užuolaida, gali būti nenumatomi. Jei pastate numatoma saugoti daug degiųjų medžiagų viršijant 1135 MJm–2 gaisro apkrovą, didelio ploto langų išdužimas gali veikti visuminį užsidegimą. Aptariami ir 25 MW galios gaisro scenarijaus padariniai.

Use of water spray curtain to disperse LNG vapor clouds

Effective safety measures to prevent and mitigate the consequences of an accidental release of flammable LNG are critical. Water spray curtain is currently recognized as an effective technique to control and mitigate various hazards in the industries. It has been used to absorb, dilute and disperse both toxic and flammable vapor cloud. It is also used as protection against heat radiation, in case of fighting vapor cloud fire. Water curtain has also been considered as one of the most economic and promising LNG vapor cloud control techniques. Water curtains are expected to enhance LNG vapor cloud dispersion mainly through mechanical effects, dilution, and thermal effects. The actual phenomena involved in LNG vapor and water curtain interaction were not clearly established from previous research. LNG spill experiments have been performed at the Brayton Fire Training Field at Texas A&M University (TAMU) to understand the effect of water curtain in controlling and dispersing LNG vapor cloud. This paper summarizes experimental methodology and presents data from two water curtain tests. The analysis of the test results are also presented to identify the effectiveness of these two types of water spray curtains in enhancing the LNG vapor cloud dispersion.

Experimental study of effective water spray curtain application in dispersing liquefied natural gas vapor clouds

AbstractThe installation of new liquefied natural gas (LNG) storage facilities in the United States to meet the demand of natural gas has brought increasing attention to LNG safety issues. Because of its highly flammable nature, one of the major hazards LNG poses is the formation of a flammable vapor cloud from any accidental release, which may result in a massive fire. The safety measures to prevent and mitigate an accidental LNG release are critical to protect employees and the public from injury or harm. The water spray curtain is currently a recognized technique to control and mitigate many toxic and flammable vapors. Much theoretical and experimental work has been carried out to determine the effectiveness of the water spray curtain in dispersing heavier vapor. However, LNG vapor dispersion behaves differently from other dense gases due to its low molecular weight and extremely low temperature. Previous studies show that water spray curtains can enhance LNG vapor dispersion from small spills. However, to develop comprehensive and structured engineering guidelines for the design of an effective water spray curtain for controlling LNG vapor many key questions still remain unanswered. In this context, it is essential to carry out research to understand the effects of water curtain on LNG vapor clouds. An experimental methodology to study the LNG vapor dispersion behaviors with the application of water spray curtain is presented in this article. This field experiment involved the fundamental study of forced dispersion, dilution due to air entrainment, and heat exchange to determine the effectiveness of water spray in reducing the LNG vapor “exclusion zone.” This article discusses and outlines the experimental method and some results based on gas concentration data analysis to emphasize the observed effectiveness of water spray curtain on LNG vapor dispersion. © 2008 American Institute of Chemical Engineers Process Saf Prog 2008

Multivariate statistical analysis of underground gas storage caverns on groundwater chemistry in Korea

AbstractAn understanding of groundwater flow and chemistry is important to operate underground storage caverns. Groundwater flow is mainly affected by cavern operating conditions. Groundwater chemistry is modified by disinfection activities for removing possible biological clogging and by mixing with cement pore water. It is important to discern these two effects, because wells affected by the disinfection activities may have hydrological connections with water curtains used to inject the disinfectant. However, it is difficult to separate these two effects using graphical methods because of their similar chemical characteristics. Instead, multivariate statistical analysis, such as principal component analysis (PCA) and factor analysis (FA), can be used. Groundwater samples for chemical analysis were obtained from four surveys in 1999–2000. Based on the results from PCA and FA, it appears that there were temporal variations of seepage water into the propane area when the cavern operation fluctuated, but we could not observe such variation in the butane area. These changes may occur mainly at depth, where water flow is slow and water renewal in the cavern surrounding is limited. Copyright © 2008 John Wiley & Sons, Ltd.

Model scale tunnel tests with water spray

A model scale study (1:23) was carried out in order to improve the basic understanding of water spray systems in longitudinal tunnel flow. The water spray system consisted of commercially available axial-flow hollow cone nozzles. Tests with both a deluge system made of 12 nozzles placed directly above the fire source and a water curtain system consisting of four nozzles placed either downstream or upstream of the fire source were carried out. A wood crib was used to simulate the fire source, which was designed to correspond to a HGV (heavy goods vehicle) fire load in large scale. A second wood crib was used as a target pile and was placed downstream the ignited wood crib. The parameters varied were the water flow rate and water pressure, the longitudinal ventilation rate and the arrangement of the nozzle system. Possible fire spread between wood cribs, with a free distance corresponding to 15 m in large scale, was investigated.

Experimental Study on Blocking Fire and Smoke by Water Curtain

Experimental Study on Blocking Fire and Smoke by Water Curtain

Numerical Investigation on the Effectiveness of Water Spray Deluge in Providing Cooling, Smoke Dilution and Radiation Attenuation in Fires

The effectiveness of water spray is influenced by nozzle type, spray momentum and orientation as well as water droplet size. It is also subject to the influence of environment conditions, most notably wind condition in open fires and ventilation in enclosures. The present study is focused on the effect of such external parameters on the effectiveness of water spray systems when used as water curtains to provide cooling and smoke dilution; and create an “escape” corridor for crews on offshore oil and gas production facilities. In such applications, water spray is more frequently referred to as “water deluge”. A related study has also been carried out to investigate the attenuation of thermal radiation by water deluge on an oil tank fire. Overall the present study has led to some useful conclusions and demonstrated the potential of numerical modeling techniques as an effective means to aid the design of water curtains and surface water deluge systems.

Visakhapatnam underground LPG storage cavern, India

One of the world's deepest underground liquefied petroleum gas (LPG) storage cavern projects has been built near the city of Visakhapatnam in India. Storage is based on the hydraulic containment principle using water pressure. This paper discusses the design aspects and various phases involved in construction. The general outline, significance of the facility and basic principles of storage are described, including the initial exploration works, complementary site investigations, basic engineering design and the design changes made during construction. Health, safety and environment as well as quality aspects are considered. The sequence and methods adopted to construct diaphragm walls for the foreshafts, sinking for the rock shafts, installation of the water curtain tunnel and excavation for the main storage cavern are described. The scope and construction methodologies are explained and the challenges and complexities of the underground project, a first for south Asia, are considered. Achievements and areas where there is scope for improvements are discussed. Finally, the advantages of such projects, critical success factors and special issues needing attention are presented.

Water Motion in a Water Curtain Head for Cleaning a Large Glass Plate

Water motion in a water curtain head, which generates a thin and wide water screen to clean a large, thin and flat glass plate, is studied using numerical calculations based on fluid dynamics and experimental observation of the motion of colored water and small air bubbles in the water channel of the water curtain head. The colored water motion, the observed position of the remaining small air bubbles, and the time required to completely remove the air bubbles were in agreement with the behavior derived from the calculations, such as the water flow pattern and the region having low pressure. In conclusion, the most important factor for the design of the water curtain head is the direction of the water recirculation, which is governed by the distance between the small water-ejection pipes arranged along the wall of the water channel. The entire design of a very wide water curtain head can be performed by considering the water flow in a local region.

Absorptance and transmittance of water spray/mist curtains

Water spray is a highly effective fire-protection agent, because evaporating droplets extract energy from the flame and combustion products as well as attenuate thermal radiation by absorption and scattering. The main objective of this paper is to characterize radiative transfer in a homogeneous water spray curtain (layer) and to calculate spectral transmittances and absorptances of a curtain. The spectral and total absorptances and transmittances reported in the paper provide fundamental understanding of radiation attenuation by water curtains. The empirical equation developed for the scaled spectral extinction coefficient of water sprays may be useful for modeling radiative transfer in spray curtains using CFD. Since the spray acts as a shield that attenuates radiation such global radiation characteristics can readily be used in simple, preliminary design analyses for mitigating and controlling fires.

Production of red mold rice using a modified Nagata type koji maker

In this research, a commercial koji maker with a rotary perforated bed of 5-m diameter was modified for red mold rice production. Monascus purpureus BCRC 31499 was selected for its high production capacities of monacolin K and red pigment. The selected strain was first cultivated in a 120-l submerged type fermentor at 34 degrees C and 2 vvm aeration rate with 60 rpm agitation for 5 days using 20% liquefied rice porridge as carbon source. The high concentration red mold rice broth (>3.5 g/ml) was harvested for inocula and well mixed with cooked rice to an initial concentration of 2% v/w. The inoculated cooked rice then was directed into the modified koji maker, in which temperature and humidity profiles were kept at varied levels at different stages, respectively. Air was circulated to remove fermentation heat while the perforated bed rotated slowly for providing mild agitation. Lag phase of the Monascus sp. in the modified koji maker was determined to be 16 h by the time the koji temperature raised rapidly. Water was added into the koji bed by a water curtain at the 36th hour to keep the moisture content of the rice koji at 50% or above. At the final stage, temperature was adjusted to 34 degrees C to direct red pigment production. After 7 days, 1,200-kg high quality red mold rice was harvested per batch. Labor costs, space, and fermentation time were reduced tremendously compared with those made by traditional methods.

Effect of shielding conditions of local dry cavity on weld quality in underwater Nd:YAG laser welding

During underwater laser beam welding (LBW), the welding quality is severely influenced by the shielding condition of the local dry cavity. In this paper, the stability of the local dry cavity and the effect of shielding condition on the weld quality during laser welding of Type 304 stainless steel were investigated. Firstly, welding experiments under various water depths without any way to exclude water from the welding zone were performed. It was found that one kind of laser-induced plasma having strong shielding effect to the incident laser beam forms when the laser irradiates the water directly if the water depth is larger than 3 mm. This shielding effect will lead to the impossibility of deep penetration welding in water. So in the welding, a water curtain nozzle was used to form a local dry cavity. The effect of the shielding conditions, e.g. water flow rate, gas flow rate and water flow angle, on the stability of the local dry cavity was studied. The welding results under various shielding conditions show the relationship between the shielding condition and the quality of the weld bead.