Influence of gases dissolved in cooling water on heat transfer during stable film boiling

Results of investigations concerning the determination of the influence of the water quality on the heat transfer of quenched hot metal surfaces are presented. With an immersion quenching device, tests have been carried out for various cooling water qualities. Apparently there was no correlation between the water quality and the cooling process (Leidenfrost temperature). High concentrations of dissolved gases yield stable vapour films (low Leidenfrost temperatures are measured). Salt displaces the dissolved gases from the water; the Leidenfrost temperature rises: the higher the salt concentration, the lower the gas concentration and, therefore, the higher the Leidenfrost temperature. If salt concentrations are high or the cooling water is degassed, the vapour film falls apart just after Immersion. An extended model considering the Influence of the gases allows the correlation of the water quality/salt concentration and the heat transfer/Leidenfrost temperature.     

Nucleation of bubbles on a solidification front—experiment and analysis

The heterogeneous nucleation of bubbles on an advancing solidification front during the freezing of water containing a dissolved gas has been experimentally and analytically studied. The formation of bubbles resulting from supersaturation of liquids is commonly encountered in different fields such as heat transfer, manufacturing, and bioscience. In this work, the sizes of nucleating bubbles and the concentration profiles of dissolved oxygen and carbon dioxide gases in the water ahead of the solidification front have been measured. From successful comparisons between the measured and predicted critical radii of nucleating bubbles and distributions of dissolved gas content, the phenomena of heterogeneous nucleation in a binary weak solution during the freezing process are quantitatively confirmed. The results show that an increase in gas content at the solidification front in the liquid decreases the free-energy barrier and critical radii of bubbles that are formed on the solidification front. The sizes of the critical radii decrease and the number of nucleating bubbles increase in the early stage of solidification. As the solidification rates decrease at longer times, the content of the dissolved gas in the liquid on the advancing interface decreases and the critical radii of nucleating bubbles increase.     

Hydrophilic Actinide Complexation Studied By Solvent Extraction Radiotracer Technique

Abstract

Actinide migration in the ground is enhanced by the formation of water soluble complexes between the actinide ions ( central atoms) and inorganic and/or organic complex formers ( ligands) dissolved in the ground water. It is essentia! to risk analysis of a wet repository to know the concentration of the central atoms and the ligands in the ground water, and the stability of the complexes formed between them (the complex formation constant) from such data the concentration of all dissolved actinide species can be calculated, and-using additional data on sorption, diffusion, and ground water flow rate-the migration rate of the actinides in the ground can be predicted.

The important actinides in nuclear waste are U, Np, Pu and Am, all radioactive and with half-lives long enough to allow the determination of their macroscopic properties, usually at> 10^ninus7M. However, when dissolved in nature, their concentrations are hardly macroscopic; typical concentration values are<10^ninus7 M ( trace concentrations) Because the chemical behavior at trace concentrations often differ from that at macro concentrations (for example polynuclear complex formation), it is important to know the chemical behavior of actinides at trace concentrations in the ground water. One method commonly used for such investigations is the solvent extraction radiotracer ( SXRT) technique, by which the radioactive properties of the actinides are used for their detection.

This report describes the SXRT technique in some detail. A particular reason for this analysis is the claim that complex formation constants obtained by the SXRT technique differs even at same actinide concentration, or are less reliable than results obtained by alternative techniques. It is true that several difficulties are encountered in the application of the SXRT technique to actinide solutions, as for example redox instability, hydrophilic complexation by side reactions and sorption, but it is also shown that a careful application of the SXRT technique yields results as reliable as by any other technique.

The report contains a literature survey on solvent extraction studies of actinide complexes formed in aqueous solutions, particularly by using the organic reagent thenoyltrifluoroacetone (TTA) dissolved in benzene or chloroform (Tab. I). Hydrolysis constants obtained by solvent extraction are listed in Table IX. The last two tables contain all actinide complexes studied by SX with inorganic ligands (Tab. XI) and with organic ligands (Tab. XII).     

Field Experiments to Determine Gas Transfer at Gated Sills

Field experiments were conducted to determine the oxygenation potential of gated sill structures in the Ohio River Valley. The objective was to determine operational procedures for water quality improvement. Oxygenation potential is typically characterized by gas transfer efficiency, with high transfer efficiency indicating a greater input of oxygen into the water. Direct oxygen measurement can be unreliable in determining transfer efficiency, and this is due to upstream stratification, relatively high background concentrations, and changes in saturation concentration when the bubbles are exposed to hydrostatic pressures within the stilling basin. As a result, in situ methane was used as an independent dissolved gas tracer. Methane is naturally present in measurable quantities with little stratification, and it does not experience an appreciable increase in saturation concentration with bubble depth. Therefore, methane measurements better reflect the true transfer efficiency of a structure. This paper focuses on the factors that influence transfer efficiency and how to achieve high quality field data through the use of methane and oxygen measurements. In addition, results from six-gated sill structures in the Ohio River Valley are presented.     

Phase-field simulation of micropores constrained by a solid network

A 2D phase-field model has been developed in order to describe the morphology of a pore forming within interdendritic liquid channels and the geometrical effect of mechanical contacts with neighboring solid. The distribution of the solid, liquid and gas phases is calculated with a multiphase-field approach which accounts for the pressure difference between the liquid and gas phases, as well as diffusion of dissolved gases in the liquid. The model incorporates the perfect gas and Sievert’s laws to describe the concentration and partitioning of gas molecules or atoms at the pore/liquid interface. The results show that the presence of solid can substantially influence the volume and pressure of the pore. A pore constrained to grow in narrow liquid channels exhibits a substantially higher mean curvature, a larger pressure and a smaller volume as compared with a pore grown under unconstrained conditions.     

冶炼烟气中氟化氢和氯化氢气体脱除的研究现状与展望

结合目前国内冶金行业发展现状及环境污染问题,揭示了含氟化氢（HF）和氯化氢（HCl）废气治理与资源化利用的重要性和必要性。介绍了工业含氟、氯废气的主要来源及危害,分析了目前含氟和含氯废气单独处理的各种方法的原理及优缺点。湿法工艺因其高效、直接、操作简单的优点而广泛应用于冶炼烟气领域。然而,湿法吸收这两种气体也存在二次污染和水资源的浪费等问题。提出利用干法吸附协同净化这两种气体更经济、更环保、更高效的新思路。     

易燃气体实时检测报警系统设计

文章介绍了一个易燃气体的实时检测系统,通过安装在轧钢车间的易燃气体传感器采集空气中的实时气体浓度,并将数据传送给单片机完成数据的分析和处理,当易燃气体浓度超过标准值的时候将超标信息发送给用户的手机实现在线监测和报警功能。设计使用了Android操作系统的手机作来开发车间环境监控软件。经过多次调试和验证,本次开发能够很好的检测甲烷、一氧化碳等易燃气体。     

Permeability,diffusivity, and solubility of oxygen gas in liquid slag

An experimental procedure for measurement of the permeability of dissolved oxygen gas in liquid slag has been developed using an oxygen concentration cell. The small amount of oxygen gas which penetrated through the liquid oxide from a pure oxygen compartment to a pure argon compartment was determined by the galvanic cell. The permeabilities of oxygen through liquid PbO-SiO₂ and FeO-PbO-SiO₂ were found to be in the range 3 x 10^-8 to 3 x 1O^-7 moles/cm s. The permeabilities were little influenced by temperature but more influenced by the composition. In separate experiments, the oxygen pressure change at the bottom of a column of slag was detected by another galvanic cell. By this method, it is not necessary to quench the specimen to determine the concentration profile of dissolved oxygen and to determine its diffusivity. Liquid oxides in the PbO-SiO₂, CaO-SiO₂-Al₂O₃and FeO-PbO-SiO₂ systems were studied. The oxygen diffusion coefficients (5 x 10^-5 to 3 x 10^-3 cm²/s) were found to increase with temperature for a fixed composition of slag, and with an increase of network-modifier oxide content at constant temperature. The solubility of oxygen gas in PbO-SiO₂ melts was estimated to be 2 x 10^-4 to 2 x 10^-5 moles/cm³ from the determined diffusivities and permeabilities. The solubilities decreased with increasing temperature in the composition range studied. Physical solubilities of gases and metals in slags determined by other investigators are compared with the present results.     

Enrichment of Methane Concentration via Separation of Gases using Vortex Tubes

The objective of this work was to determine if a vortex tube can be used as a gas separation device. A vortex tube is a simple mechanical device that has no moving parts. It separates a compressed inlet fluid into two streams, one hot and the other cold. There are a variety of theories to explain this separation. It has been hypothesized that a mixture of compressed gases flown into the vortex tube may separate into individual gas streams by virtue of differential centrifugal forces acting on them. During previous studies by others, conflicting results have been obtained using this hypothesis. Further study of the gas separation process in a vortex tube was carried out. An attempt has been made to separate methane and nitrogen gases using vortex tubes. This particular separation or the resulting enrichment of Methane concentration has applications in the mining industry. Methane is emitted in an underground coal mine. It leaks from the coal seams and is extremely hazardous for workers because of its high explosivity in air. A conventional but costly means of circumventing this problem is methane drainage before mining. Yet another effective method is to blow large amount of air through the mine to locally dilute methane concentration. The mixture of methane and air is directly passed into the atmosphere. There are advantages to separating methane from air at the ventilation exhaust of the mine. First, methane being a greenhouse gas has strict EPA emission standards, and second, methane can be directly used for generating power. In this experimental work, a laboratory size setup was used to investigate the feasibility of using a fixed geometry vortex tube for separating methane and nitrogen from a mixture. It was found that there was partial gas separation leading to a higher concentration of methane at one exit in comparison to the inlet and a lower concentration at the other exit.     

Cancer--a matter of life and cell death

PURPOSE: To evaluate during various intervals of time the escape of long-acting gases contained in a plastic syringe closed with a stopcock or a plastic cap. METHODS: A 60-ml plastic syringe was filled or partially filled with a long-acting gas, either sulfur hexafluoride or perfluoropropane. The tip of the syringe was closed with either a stopcock or the syringe's plastic cap. After various intervals of time, the concentration of the long-acting gas in the syringe was measured by gas chromatography. RESULTS: The concentration of both long-acting gases was higher than 98% at 24 hours after filling when the syringe was closed with a stopcock; however, it was less than 41% when the syringe was filled and capped tightly with its plastic cap. CONCLUSION: The proportion of long-acting gases escaping in 24 hours from a filled syringe capped with a stopcock is clinically insignificant.     

Tunable diode laser measurements of CO,H<Subscript>2</Subscript>O,and temperature near 1.56 µm for steelmaking furnace pollution control and energy efficiency

Laser-based in-situ measurements of furnace gases show promise for improving energy efficiency and pollutant emissions for steelmaking furnaces such as electric arc furnaces (EAFs). A near-infrared (IR) tunable diode laser (1.56 μm) has performed in-situ off-gas analysis of gas temperature and carbon monoxide and water concentrations in the exhaust gas region above a laboratory burner, with response times less than 1 second. These laboratory experiments related spectroscopic data to gas temperature and concentration data. The applicable range of conditions tested is representative of those found in a commercial EAF and includes temperatures from 1250 to 1650 K, CO concentration from 0 to 10 pct, and H₂O concentration from 7 to 30 pct. Two-tone frequency modulation was used to increase the detection sensitivity. The method has been optimized and the measurement error has also been determined. Based on the results of the error analysis of the regression equations, the minimum accuracy of the technique has been estimated as 30 K for temperature, 0.8 pct for CO, and 3 pct for H₂O using 277 test data points. This accuracy is sufficient for EAF control. Initial full-scale trials are also reported.     

Antiproliferative effect of methyl-beta-cyclodextrin in vitro and in human tumour xenografted athymic nude mice

A nondestructive leak detection method developed at Technical Research Centre of Finland (VTT) was tested for both gas-flushed and vacuum flexible packages. In the method, a gas package containing 0.5 to 5.0% (vol/vol) hydrogen in nitrogen was positioned in a test chamber, a controlled vacuum was pulled in the chamber through a pipe connected to a hydrogen sensor, and leaking packages were detected by the sensor as increased H2 concentration. The H2 tracer gas (0.5 to 5.0%) was introduced into leaking finished vacuum packages at 200 kPa pressure. Within 1 to 4 s the developed test method was able to detect leaks down to 10 to 15 microns and 20 to 30 microns in diameter in commercially manufactured gas-flushed packages filled with roasted meat balls and vacuum packages filled with ground coffee, respectively. Before leak testing, the vacuum packages were charged with H2 for 30 s. The sensitivity and leak detection time of the test method were improved when the H2 concentration in the package was increased and when the free space in the test chamber was decreased. The evaluated H2 concentrations did not affect the sensory or microbiological quality of the roasted meat balls. This study clearly demonstrated that the hydrogen tracer gas leak detection method has potential to be further developed as a fast, nondestructive, on-line leak testing apparatus for flexible packages with or without a headspace.     

Degassing of static melts by insoluble purge gases

A model has been developed to describe the degassing of static melts by insoluble purge gases. In this treatment, both the diffusion of dissolved hydrogen through the melt to the purge gas bubbles and the chemical kinetics of the adsorption of hydrogen at the bubble surfaces are considered. The process is modeled as one in which a small diameter column of purge gas bubbles rises in the center of a large diameter cylindrical static melt. Three dimensionless groups appear in the analysis, and they determine the melt gas content as a function of time. The first dimensionless group,β, is defined as the ratio of the diameter of the bubble column to that of the melt. The second,N _D, is the ratio of the kinetic rate of incorporation of hydrogen into the bubble column to the rate of diffusion of hydrogen through the melt to the bubble column. The third, α, is determined by the equilibrium concentration of hydrogen in the melt, and is normally wholly determineda priori. The model has been used to analyze the degassing of liquid aluminum. The degassing rates predicted by this model are shown to be in good agreement with experimental observations in melts of greatly different sizes and using various gas flow rates.     

Simultaneous determination of epirubicin, doxorubicin and their principal metabolites in human plasma by high-performance liquid chromatography and electrochemical detection

A method is described which permits the trace analysis of 10 chlorobenzenes in aqueous samples. Chlorobenzenes were extracted from water samples by solid-phase extraction with a C18 cartridge and analysis was carried out by gas chromatography-mass spectrometry in the selected-ion monitoring mode. The recovery and precision of the method were evaluated by extraction of spiked reagent-grade water at concentration levels of 0.1, 1.0 and 10.0 micrograms/l. This method was applied to the determination of chlorobenzenes in tap, ground and river water. By preparing 200 ml of environmental water samples, the detection limits of the compounds studied were in the range of 0.010-0.042 microgram/l.     

The injection of solids using a reactive carrier gas

The injection of nonwettable powders into melts in the bubbling regime was studied experimentally using a cold-model system. Polyethylene powder was injected into a cylindrical vessel containing water, through a vertical top-submerged lance, with insoluble (air) and soluble (ammonia) carrier gases. The concentration of particles in the liquid and the penetration length of the particle-liquid jet into the bath were measured, as the carrier gas composition, the gas and solids flow rates, and the particle size were varied. It was found that the concentration of particles retained in the liquid was up to 10 times higher, and the penetration length of the jet was up to three times higher when the soluble carrier gas was used instead of the insoluble carrier gas. For both carrier gases, the dispersed particle concentration increased with increasing gas flow rate and increasing particle size, whereas the penetration length of the jet increased with increasing gas and solids flow rates.     

Gas embolism due to intravenous FC 80 liquid fluorocarbon

Lethal gas embolism always occurs after FC 80 liquid fluorocarbon is injected intravenously (0.1 ml/kg body mass) in dogs breathing room air but not in dogs breathing oxygenated FC 80 liquid fluorocarbon. Gas embolism is not prevented in dogs that have been injected intravenously with FC 80 when they are exposed to 2 ATA (atmospheres absolute) 20% 02-80% N2, 9 ATA 5% O2-95% He, or 1 ATA 100%, O2. In dogs that die of FC 80-induced gas embolism, free gas in the right atrium contains approximately 0.5 g FC 80/liter, and Po2 and Pco2 in the gas are in equilibrium with their corresponding tensions in right atrial blood. These observations are consistent with the hypothesis that PFC 80 in alveolar gas does not equilibrate with PFC 80 (55 mmHg) in blood. The total gas tension in pulmonary capillary blood containing FC 80 and its vapor thus exceeds the total tension of alveolar gases (atmospheric pressure). Bubbles of O2, CO2, N2, FC 80, and water vapor form in the regions of the pulmonary capillary bed where the total tension of gases dissolved in blood exceeds the absolute blood pressure.     

水合物法分离气体的促进剂及促进机理研究进展

目前添加促进剂后水合物形成机理并无统一定论,本文详细阐述了气体水合物形成的降低表面张力理论、临界胶束理论、毛细效应理论、模板效应理论和表面疏水效应理论等促进机理,综述了传统促进剂（THF、CP、SDS）、生物环保型促进剂（氨基酸、淀粉）,尤其是离子液体在气体水合物形成相平衡实验、动力学规律和促进机理方面的应用研究进展,阐述了离子液体半笼型水合促进剂在混合气体分离方面的研究现状,指出应从促进剂结构性质及其在水相中的聚集形态入手,研究促进剂?气体?水之间的分子间作用力,建立各类气体水合物促进剂的筛选体系。      

Modeling Total Dissolved Gas Concentration Downstream of Spillways

Dams are often operated to facilitate downstream juvenile anadromous fish migration over the spillways, but such operation can cause high dissolved concentrations of oxygen and nitrogen that can be harmful to fish. The concentration of total dissolved gas (TDG) in the flow changes with distance downstream of the spillway crest and depends on the geometric configuration of the spillway and on hydraulic and operating conditions. A model is presented that simulates the physical processes of gas transfer with the goal of having an accurate and more widely applicable TDG model for plunging spillway discharges. Bubble transfer is dominant in the stilling basin, while water surface transfer is dominant downstream. Sensitivity analyses suggest which physical processes are important for accurate total dissolved gas predictions. Instantaneous bubble coalescence and breakup based upon local turbulence conditions is an appropriate assumption. Vertical bubble profiles do not need to be simulated in this type of model. Water surface roughness provides a significant increase to surface transfer. Tailwater depth is important to downstream TDG concentrations. Finally, a 10% difference in air entrained at the plunge point causes relatively minor differences in TDG of 1.4 and 3.1% at low and high discharges, respectively.     

Oxygen Transfer Model for a Flow-Through Hollow-Fiber Membrane Biofilm Reactor

A mechanistic oxygen transfer model was developed and applied to a flow-through hollow-fiber membrane-aerated biofilm reactor. Model results are compared to conventional clean water test results as well as performance data obtained when an actively nitrifying biofilm was present on the fibers. With the biofilm present, oxygen transfer efficiencies between 30 and 55% were calculated from the measured data including the outlet gas oxygen concentration, ammonia consumption stoichiometry, and oxidized nitrogen production stoichiometry, all of which were in reasonable agreement. The mechanistic model overpredicted the oxygen transfer by a factor of 1.3 relative to the result calculated from the outlet gas oxygen concentration, which was considered the most accurate of the measured benchmarks. A mass transfer coefficient derived from the clean water testing with oxygen sensors at the membrane-liquid interface was the most accurate of the predictive models (overpredicted by a factor of 1.1) while a coefficient determined by measuring bulk liquid dissolved oxygen underpredicted the oxygen transfer by a factor of 3. The mechanistic model was found to be an adequate tool for design because it used the published diffusion and partition coefficients rather than requiring small-scale testing to determine the system-specific mass transfer coefficients.     

Distribution of dystrophin and dystrophin-associated protein 43DAG (beta-dystroglycan) in the central nervous system of normal controls and patients with Duchenne muscular dystrophy

The measurement of combustion gases produced by burning aircraft cabin materials poses a continuing limitation for smoke toxicity research. Because toxic effects of gases depend on both their concentrations and the duration of exposure, frequent atmosphere sampling is necessary to define the gas concentration-exposure time curve. A gas chromatographic (GC) method was developed for the simultaneous analyses of carbon monoxide (CO), hydrogen sulfide (H2S), sulfur dioxide (SO2), and hydrogen cyanide (HCN). The method used an MTI M200 dual-column gas chromatograph equipped with 4-m molecular sieve-5A and 8-m PoraPlot-U wall-coated capillary columns and two low-volume, high-sensitivity thermal conductivity detectors. Detectability (in parts per million [ppm]) and retention times (in seconds) for the gases were as follows: CO, 100 ppm, 28 s; H2S, 50 ppm, 26 s; SO2, 125 ppm, 76 s; and HCN, 60 ppm, 108 s. The method was effective for determining these gases in mixtures and in the combustion atmospheres generated by burning wool (CO, HCN, and H2S) and modacrylic fabrics (CO and HCN). Common atmospheric gaseous or combustion products (oxygen, carbon dioxide, nitrogen, water vapor, and other volatiles) did not interfere with the analyses. However, filtration of the combustion atmospheres was necessary to prevent restriction of the GC sampling inlet by smoke particulates. The speed, sensitivity, and selectivity of this method make it suitable for smoke toxicity research and for evaluating performance of passenger protective breathing equipment. Also, this method can potentially be modified to analyze these gases when they are liberated from biosamples.