WorldWideScience
1

Influence of Barometric Pressure Changes on Ventilation Conditions in Deep Mines  

Science.gov (United States)

Barometric air pressure and its changes have a critical impact on ventilation conditions in the underground workings of deep mines. Changes in pressure are particularly important because they are responsible for the transient states of ventilation conditions, therefore, assessing the scale of pressure change is essential. Unfortunately, previously for many years in the Polish mining industry barometric pressure was recorded only on tapes of mechanical barographs by the ventilation department on the surface and therefore such dependencies of methane concentration due to barometric pressure changes have not been properly documented. Today, after the implementation in mines of instruments enabling the monitoring of absolute pressure in the workings of mines (Wasilewski, 2009) the conditions have been created to study the influence of pressure changes on changes of air parameters in the mine workings. Barometric pressure changes were observed and recorded over a course of approximately two years using monitoring system that utilized high accuracy pressure sensors on the surface and in selected workings of an underground mine. This paper presents a statistical analysis of the data that we generated from assessing pressure changes on the surface and at selected underground points in the mine. In the article, which presents the results of the first part of the study, some examples of when significant changes in pressure prior to the tragic events, which were not accompanied by changes in the methane concentration in mine workings, will also be shown. Interestingly, we found that the relationship between methane ignitions and explosions in longwall gob mined via the cave-in method is associated with changes in the barometric pressure. Several instances of methane ignitions and explosions in the gob of cave-in longwalls in recent years were compared with background barometric pressure changes. Research carried out in within the strategic project "Improving work safety in the mines" allowed to record air parameters changes inside the gob of longwalls and show the influence of pressure changes on changes in methane and oxygen concentration in the gob, which will be shown in the second part of the article to be published in the near future.

Wasilewski, Stanis?aw

2014-10-01

2

New insights from well responses to fluctuations in barometric pressure  

Science.gov (United States)

Hydrologists have long recognized that changes in barometric pressure can produce changes in water levels in wells. The barometric response function (BRF) has proven to be an effective means to characterize this relationship; we show here how it can also be utilized to glean valuable insights into semi-confined aquifer systems. The form of the BRF indicates the degree of aquifer confinement, while a comparison of BRFs between wells sheds light on hydrostratigraphic continuity. A new approach for estimating hydraulic properties of aquitards from BRFs has been developed and verified. The BRF is not an invariant characteristic of a well; in unconfined or semi-confined aquifers, it can change with conditions in the vadose zone. Field data from a long-term research site demonstrate the hydrostratigraphic insights that can be gained from monitoring water levels and barometric pressure. Such insights should be of value for a wide range of practical applications. ?? 2010 The Author(s). Journal compilation ?? 2010 National Ground Water Association.

Butler, J.J.; Jin, W.; Mohammed, G.A.; Reboulet, E.C.

2011-01-01

3

Impact of changes in barometric pressure on landfill methane emission  

Science.gov (United States)

methane emissions were measured continuously using the eddy covariance method from June to December 2010. The study site was located at the Bluff Road Landfill in Lincoln, Nebraska, USA. Our results show that landfill methane emissions strongly depended on changes in barometric pressure; rising barometric pressure suppressed the emission, while falling barometric pressure enhanced the emission, a phenomenon called barometric pumping. There was up to a 35-fold variation in day-to-day methane emissions due to changes in barometric pressure. Wavelet coherence analysis revealed a strong spectral coherency between variations of barometric pressure and methane emission at periodicities ranging from 1 day to 8 days. Power spectrum and ogive analysis showed that at least 10 days of continuous measurements was needed in order to capture 90% of the total variance in the methane emission time series at our landfill site. From our results, it is clear that point-in-time measurements taken at monthly or longer time intervals using techniques such as the trace plume method, the mass balance method, or the closed-chamber method will be subject to large variations in measured emission rates because of the barometric pumping phenomenon. Estimates of long-term integrated methane emissions from landfills based on such measurements could yield uncertainties, ranging from 28.8% underestimation to 32.3% overestimation. Our results demonstrate a need for continuous measurements to quantify annual total landfill emissions. This conclusion may apply to the study of methane emissions from wetlands, peatlands, lakes, and other environmental contexts where emissions are from porous media or ebullition. Other implications from the present study for hazard gas monitoring programs are also discussed.

Xu, Liukang; Lin, Xiaomao; Amen, Jim; Welding, Karla; McDermitt, Dayle

2014-07-01

4

Barometric pressure transient testing applications at the Nevada Test Site. Nuclear chimney analysis. Final report  

International Nuclear Information System (INIS)

Investigations of barometric pressure testing of NTS nuclear chimneys were reviewed. This review includes the models used in the interpretation, methods of analysis, and results. Analytic and semi-analytic models were presented and applied to both historical data and new data taken for this current project. An interpretation technique based on non-linear least squares methods was used to analyze this data in terms of historic and more recent chimney models. Finally, a detailed discussion of radioactive gas transport due to surface barometric pressure fluctuations was presented. This mechanism of transport, referred to as ''barometric pumping,'' is presented in terms of conditions likely to be encountered at the NTS. The report concludes with a discussion of the current understanding of gas flow properties in the alluvial and volcanic areas of the NTS, and suggestions for future efforts directed toward increasing this understanding are presented

5

Strain gage barometric transmitter  

Science.gov (United States)

A strain gage barometric transmitter for measuring the atmospheric pressure in severe environmental conditions is described. This equipment specifications are presented and its performance assessed. It is shown that this barometric sensor can measure the atmospheric pressure with a precision of 0.5 mb during a 6 month period.

Viton, P.

1977-01-01

6

Barometric pressure transient testing applications at the Nevada Test Site: formation permeability analysis. Final report  

International Nuclear Information System (INIS)

The report evaluates previous investigations of the gas permeability of the rock surrounding emplacement holes at the Nevada Test Site. The discussion sets the framework from which the present uncertainty in gas permeability can be overcome. The usefulness of the barometric pressure testing method has been established. Flow models were used to evaluate barometric pressure transients taken at NTS holes U2fe, U19ac and U20ai. 31 refs., 103 figs., 18 tabs

7

Barometric pressure transient testing applications at the Nevada Test Site: formation permeability analysis. Final report  

Energy Technology Data Exchange (ETDEWEB)

The report evaluates previous investigations of the gas permeability of the rock surrounding emplacement holes at the Nevada Test Site. The discussion sets the framework from which the present uncertainty in gas permeability can be overcome. The usefulness of the barometric pressure testing method has been established. Flow models were used to evaluate barometric pressure transients taken at NTS holes U2fe, U19ac and U20ai. 31 refs., 103 figs., 18 tabs. (ACR)

Hanson, J.M.

1984-12-01

8

Estimating large-scale fracture permeability of unsaturatedrockusing barometric pressure data  

Energy Technology Data Exchange (ETDEWEB)

We present a three-dimensional modeling study of gas flow inthe unsaturated fractured rock of Yucca Mountain. Our objective is toestimate large-scale fracture permeability, using the changes insubsurface pneumatic pressure in response to barometric pressure changesat the land surface. We incorporate the field-measured pneumatic datainto a multiphase flow model for describing the coupled processes ofliquid and gas flow under ambient geothermal conditions. Comparison offield-measured pneumatic data with model-predicted gas pressures is foundto be a powerful technique for estimating the fracture permeability ofthe unsaturated fractured rock, which is otherwise extremely difficult todetermine on the large scales of interest. In addition, this studydemonstrates that the multi-dimensional-flow effect on estimatedpermeability values is significant and should be included whendetermining fracture permeability in heterogeneous fracturedmedia.

Wu, Yu-Shu; Zhang, Keni; Liu, Hui-Hai

2005-05-17

9

Barometric pressure forcing on radon-222 and temperature in fumarolic gases: a tool to describe flow-rate dynamics  

Science.gov (United States)

We propose two conceptual models for the dynamics of fumarolic gases, during their ascent through the volcano plumbing, based on radon-222 and temperature data collected on fumaroles of La Soufrière volcano (Guadeloupe,FWI) together with local barometric pressure, and on a new interpretation of older data collected on Merapi volcano (1), Indonesia. All these in-situ measurements prove that the diurnal (24h, S1 barometric wave) and semidiurnal (12h, S2 barometric wave) variations in radon concentration are clearly observable, and positively or negatively correlated with barometric pressure variation. Two models are used to interpret this correlation. The first model, called “Accumulation mode”, is characterized by an initial and negligible deep radon-222 source and by a major contribution of radon-222 from conduit walls and connected fractures (emanation and exhalation mechanisms) during the gas ascent through the fumarolic system. This model is substantiated by a positive correlation between radon and pressure in the Merapi fumaroles. The second model, or “Decay mode”, is exemplified by a negative correlation between radon and pressure as measured in fumaroles at La Soufrière volcano. It is characterized by radioactive decay of a strong initial radon-222 source generated by a deeper reservoir (hydrothermal system or magmatic chamber) whereas contribution by conduit walls and connected fractures to the total radon-222 activity in the fumarole is comparatively minor during the transit time of the gas. In these two modes, it is possible to infer that, for transit times longer than ca. 21 days, the barometric pressure does not modulate the radon signal. Thus, the simultaneous monitoring of radon-222, temperature and barometric pressure provides a precise fumarole flowmeter. In addition, it is a tool to decipher shallow versus deep feeding of volcanic fumaroles that should prove useful for volcano monitoring. (1)Zimmer, M. & Erzinger, J. Continuous H2O, CO2, 222Rn and temperature measurements on Merapi Volcano, Indonesia. J. Volcanol. Geoth. Res. 125, 25-38 (2003).

Richon, P.; Salaun, A.; Boudon, G.; Villemant, B.; Crispi, O.; Sabroux, J.

2010-12-01

10

Barometric pressure, dry bulb temperature and vapor pressure at the lowest terrestrial site on earth, Dead Sea basin, Neve Zohar, Israel  

Science.gov (United States)

The Dead Sea basin is located at the lowest terrestrial site on the earth and, thereby, has the tallest atmospheric air column above its surface. Consequently, the Dead Sea basin is expected, a priori, to have the highest terrestrial barometric pressure and, thereby, the highest molecular oxygen density on the earth. The barometric pressure and dry bulb temperature have been monitored continuously at Neve Zohar, located on the western shore of the Dead Sea, since January 1995. The monthly average daily barometric pressure values exceed normal atmospheric pressure by a maximum of 4.83 hPa (4.77%) and a minimum of 33.1 hPa (3.26%) for December and July, respectively. This increase in barometric pressure can serve as a simple way to improve arterial oxygenation in hypoxemic patients. As a result, a number of research projects have been initiated on the treatment of patients suffering from pulmonary and cardiac diseases at the Dead Sea basin. The hourly barometric pressure data with regard to both its diurnal and monthly variation and the correlation between barometric pressure and dry bulb temperature will be analyzed.

Kudish, A. I.; Evseev, E. G.

2006-03-01

11

Energy expenditure estimation during normal ambulation using triaxial accelerometry and barometric pressure.  

Science.gov (United States)

Energy expenditure (EE) is an important parameter in the assessment of physical activity. Most reliable techniques for EE estimation are too impractical for deployment in unsupervised free-living environments; those which do prove practical for unsupervised use often poorly estimate EE when the subject is working to change their altitude by walking up or down stairs or inclines. This study evaluates the augmentation of a standard triaxial accelerometry waist-worn wearable sensor with a barometric pressure sensor (as a surrogate measure for altitude) to improve EE estimates, particularly when the subject is ascending or descending stairs. Using a number of features extracted from the accelerometry and barometric pressure signals, a state space model is trained for EE estimation. An activity classification algorithm is also presented, and this activity classification output is also investigated as a model input parameter when estimating EE. This EE estimation model is compared against a similar model which solely utilizes accelerometry-derived features. A protocol (comprising lying, sitting, standing, walking, walking up stairs, walking down stairs and transitioning between activities) was performed by 13 healthy volunteers (8 males and 5 females; age: 23.8 ± 3.7 years; weight: 70.5 ± 14.9 kg), whose instantaneous oxygen uptake was measured by means of an indirect calorimetry system (K4b(2), COSMED, Italy). Activity classification improves from 81.65% to 90.91% when including barometric pressure information; when analyzing walking activities alone the accuracy increases from 70.23% to 98.54%. Using features derived from both accelerometry and barometry signals, combined with features relating to the activity classification in a state space model, resulted in a VO(2) estimation bias of -0.00 095 and precision (1.96SD) of 3.54 ml min(-1) kg(-1). Using only accelerometry features gives a relatively worse performance, with a bias of -0.09 and precision (1.96SD) of 5.99 ml min(-1) kg(-1), with the largest errors due to an underestimation of VO(2) when walking up stairs. PMID:23110944

Wang, Jingjing; Redmond, Stephen J; Voleno, Matteo; Narayanan, Michael R; Wang, Ning; Cerutti, Sergio; Lovell, Nigel H

2012-11-01

12

Some Connections Between the Solar Wind, Barometric Pressure, Geomagnetism, and Seismic Background Noise  

Science.gov (United States)

All three of the original papers on seismic hum note the curious fact that some of the measured peaks in the noise spectrum do not correspond to known seismic S or T modes. We have previously noted (Thomson et al, Proc. IEEE, 2007) the presence of high--Q peaks in barometric pressure data. Similarly, (Ghosh et al, JGR 2009) peaks were noted in solar wind density at the ACE spacecraft and evidence given that solar modes can coexist with turbulence in the solar wind. Here we show that fluctuations in the solar wind density and velocity measured at ACE are coherent with those measured on the microbarograph at BFO and elsewhere. This coherence is strongest at the frequences of solar normal modes with the described peak at 404 uHz probably being P0,2. There are many similar examples. We also examine the canonical coherence between geomagnetic and seismic data and again find that it is generally very high with peaks approaching the 100% significance level at the frequencies of low--degree solar modes. Many of these frequencies occur between those of seismic normal modes and thus explain the curious peaks noted in the original papers. Moreover, at frequencies where solar and seismic normal mode frequencies coincide, as 0S18 (2672.5 uHz) and P3,17 (2671.0 uHz) the coupling appears to be more efficient. This coupling occurs largely on the horizontal seismic components and, because the horizontal sensors of STS-1s are insensitive to magnetic fields, must be seismic and not instrumental.

Eakins, J. A.; Vernon, F. L.; Thomson, D. J.

2010-12-01

13

The Influence od Air Temperature and Barometric Pressure on Radon and Carbon Dioxide Levels in Air of a Karst Cave  

International Nuclear Information System (INIS)

Radioactive noble gas radon (222Rn) is created in minerals by radioactive transformation of 226Ra within the 238U natural decay chain. It migrates through the ground, accumulates in underground rooms (e. g., karst caves) and eventually enters the atmosphere. It is always present in our living and working environment. Because of its harmful health effect, it presents a serious social concern but is, on the other hand, a useful tool in several scientific disciplines. It is thus used as a tracer in exploring movement of air masses and an indicator of tectonic faults. Another minor constituent of air is carbon dioxide. Similar as radon, it is dangerous at high levels, but its presence in air of karst caves is indispensable for their life, because it governs speleogenetic processes. In the cave air, its concentration is determined by the inflow of outside air, biogenic activity of soil, degradation of organic matter and carbonate, degassing from water, and human activity. Therefore, ventilation of the cave is crucial for its conservation. Based on temporal variations of radon and carbon dioxide levels, ventilation regime in the cave can be estimated. Radon has been surveyed in all the twenty show caves and in thirty other caves in Slovenia, with emphasis on the Postojna Cave. In the present study, in addition to radon, monitoring of carbon dioxide was introduced for the first time. The Kostanjevica Cave, situated in southern Slovenia in an isolated island of karst, was selected because it is crossed by a tectonic fault at which measurements of three-dimensional micro displacements are underway. Because of the fault, high levels of radon and carbon dioxide were expected. In this paper, measurements are described and both the spatial and time variations of radon and carbon dioxide levels are presented and commented on. Continuous radon monitoring was carried out with the RadonScout devices (Sarad, Germany) from April to December 2009, with several interruptions because of the instrument failures. At several points along the guided tourist route, instantaneous concentrations of radon and carbon dioxide were measured monthly from August 2009 to March 2010. Outdoor air temperature and barometric pressure for the nearby meteorological station were obtained from the Office of Meteorology of the Environmental Agency of the Republic of Slovenia. Change of ventilation regime in the cave is reflected in seasonal variation of radon concentration. It is high in summer (1800 - 2200 Bq m-3) and substantially reduced in winter (20 - 500 Bq m-3), when temperature in the cave is higher than outside and radon is diluted by the inflow of outside air, caused by natural air draught. This draught is minimal or reversed in summer. Concentrations of both gases, radon and CO2, are well correlated. (author)

14

No More Snow Pits? Potential to Retrieve Bulk Snow Pack Structure from Transient Barometric Pressure Waves measured from a Prototype Embedded Wireless Sensor Network  

Science.gov (United States)

Networked micro-sensors have the capacity to enable improvements in ground-based data collection at resolutions that are currently unresolved. Crossbow® Environmental Motes (MEP410 Models) were embedded in an accumulated snow pack in a meadow at Niwot Ridge Long-Term Ecological Research (LTER) C1 site. Motes were mounted to a custom designed deployment structure that constitutes an adaptive sensor "tower" at a maximum height of 142 with sensors deployed at depths of 122cm, 71cm, and 17cm from the ground. Barometric pressures measured from this embedded wireless network indicate low frequency fluctuations over the study period with higher frequency components varying as a function of depth. Mean pressure measured over the analysis period were 707.82 mb (122cm), 702.48 mb (71cm), and 704.09mb (17cm). Results indicate filtering of high frequency components of pressure measured at depth with reduced amplitude and time-lag (phase shift) modulated by changes in snow pack permeability related to density changes.

Lampkin, D. J.

2007-12-01

15

Reservoir response to tidal and barometric effects  

Energy Technology Data Exchange (ETDEWEB)

Solid earth tidal strain and surface loading due to fluctuations in barometric pressure have the effect, although extremely minute, of dilating or contracting the effective pore volume in a porous reservoir. If a well intersects the formation, the change in pore pressure can be measured with sensitive quartz pressure gauges. Mathematical models of the relevant fluid dynamics of the well-reservoir system have been generated and tested against conventional well pumping results or core data at the Salton Sea Geothermal Field (SSGF), California and at the Raft River, Geothermal Field (RRGF), Idaho. Porosity-total compressibility product evaluation based on tidal strain response compares favorably with results based on conventional pumping techniques. Analysis of reservoir response to barometric loading using Auto Regressive Integrated Moving Average (ARIMA) stochastic modeling appears also to have potential use for the evaluation of reservoir parameters.

Hanson, J.M.

1980-05-29

16

Variations in cosmic radiation intensity associated with the barometric effect  

Directory of Open Access Journals (Sweden)

Full Text Available The barometric effect for the Mexico City neutron monitor is obtained from cosmic ray intensity data obtained during the years 1990-1997, more than half a solar cycle, by correlation between the neutron intensity and the atmospheric pressure. In order to eliminate other factors of solar or geomagnetic origin we use only geomagnetically quiet days (kp<20°. The evolution of the barometric coefficient from maximum (1990 to minimum (1997 solar activity is discussed.

José Fco. Valdés-Galicia

2000-05-01

17

16 CFR 1203.8 - Conditioning environments.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Conditioning environments. 1203.8 Section...HELMETS The Standard § 1203.8 Conditioning environments. Helmets shall...13. The barometric pressure in all conditioning environments shall be 75 to...

2010-01-01

18

Barometric pumping with a twist: VOC containment and remediation without boreholes  

Energy Technology Data Exchange (ETDEWEB)

A large national cost is incurred in remediating near-surface contamination such as surface spills, leaking buried pipelines, and underground storage tank sites. Many of these sites can be contained and remediated using enhanced natural venting, capitalizing on barometric pumping. Barometric pumping is the cyclic movement experienced by soil gas due to oscillations in atmospheric pressure. Daily variations of 5 millibars are typical, while changes of 25 to 50 millibars can occur due to major weather front passage. The fluctuations can cause bulk vertical movement in soil gas ranging from centimeters to meters, depending on the amplitude of the pressure oscillation, soil gas permeability, and depth to an impermeable boundary such as the water table. Since the bulk gas movement is cyclic, under natural conditions no net advective vertical movement occurs over time. Science and Engineering Associates, Inc., is developing an engineered system to capitalize on the oscillatory flow for soil contaminant remediation and containment. By design, the system allows normal upward movement of soil gas but restricts the downward movement during barometric highs. The earth`s surface is modified with a sealant and vent valve such that the soil gas flow is literally {open_quotes}ratcheted{close_quotes} to cause a net upward flow over time. A key feature of the design is that it does not require boreholes, resulting in a very low cost remediation effort and reduced personnel exposure risk. In the current phase (Phase I) the system`s performance is being evaluated. Static and transient analysis results are presented which illustrate the relative magnitude of this advective movement compared to downward contaminant diffusion rates. Calculations also indicate the depth of influence for various surface and soil configurations. The system design will be presented, as well as a cost assessment compared to conventional techniques.

Lowry, W.; Dunn, S.D.; Walsh, R. [Science and Engineering Associates, Inc., Santa Fe, NM (United States)] [and others

1995-10-01

19

Field measurements of tracer gas transport by barometric pumping  

International Nuclear Information System (INIS)

Vertical gas motions induced by barometric pressure variations can carry radioactive gases out of the rubblized region produced by an underground nuclear explosion, through overburden rock, into the atmosphere. To better quantify transit time and amount of transport, field experiments were conducted at two sites on Pahute Mesa, Kapelli and Tierra, where radioactive gases had been earlier detected in surface cracks. At each site, two tracer gases were injected into the rubblized chimney 300-400 m beneath the surface and their arrival was monitored by concentration measurements in gas samples extracted from shallow collection holes. The first ''active'' tracer was driven by a large quantity of injected air; the second ''passive'' tracer was introduced with minimal gas drive to observe the natural transport by barometric pumping. Kapelli was injected in the fall of 1990, followed by Tierra in the fall of 1991. Data was collected at both sites through the summer of 1993. At both sites, no surface arrival of tracer was observed during the active phase of the experiment despite the injection of several million cubic feet of air, suggesting that cavity pressurization is likely to induce horizontal transport along high permeability layers rather than vertical transport to the surface. In contrast, the vertical pressure gradients associated with barometric pumping brought both tracers to the surface in comparable concentrations within three months at Kapelli, whereas 15 months elapsed before surface arrival at Tierra. At Kapelli, a quasisteady pumping regime was established, with tracer concentrations in effluent gases 1000 times smaller than concentrations thought to exist in the chimney. Tracer concentrations observed at Tierra were typically an order of magnitude smaller. Comparisons with theoretical calculations suggest that the gases are traveling through ?1 millimeter vertical fractures spaced 2 to 4 meters apart. 6 refs., 18 figs., 3 tabs

20

A Graphical Method for Estimation of Barometric Efficiency from Continuous Data - Concepts and Application to a Site in the Piedmont, Air Force Plant 6, Marietta, Georgia  

Science.gov (United States)

A graphical method that uses continuous water-level and barometric-pressure data was developed to estimate barometric efficiency. A plot of nearly continuous water level (on the y-axis), as a function of nearly continuous barometric pressure (on the x-axis), will plot as a line curved into a series of connected elliptical loops. Each loop represents a barometric-pressure fluctuation. The negative of the slope of the major axis of an elliptical loop will be the ratio of water-level change to barometric-pressure change, which is the sum of the barometric efficiency plus the error. The negative of the slope of the preferred orientation of many elliptical loops is an estimate of the barometric efficiency. The slope of the preferred orientation of many elliptical loops is approximately the median of the slopes of the major axes of the elliptical loops. If water-level change that is not caused by barometric-pressure change does not correlate with barometric-pressure change, the probability that the error will be greater than zero will be the same as the probability that it will be less than zero. As a result, the negative of the median of the slopes for many loops will be close to the barometric efficiency. The graphical method provided a rapid assessment of whether a well was affected by barometric-pressure change and also provided a rapid estimate of barometric efficiency. The graphical method was used to assess which wells at Air Force Plant 6, Marietta, Georgia, had water levels affected by barometric-pressure changes during a 2003 constant-discharge aquifer test. The graphical method was also used to estimate barometric efficiency. Barometric-efficiency estimates from the graphical method were compared to those of four other methods: average of ratios, median of ratios, Clark, and slope. The two methods (the graphical and median-of-ratios methods) that used the median values of water-level change divided by barometric-pressure change appeared to be most resistant to error caused by barometric-pressure-independent water-level change. The graphical method was particularly resistant to large amounts of barometric-pressure-independent water-level change, having an average and standard deviation of error for control wells that was less than one-quarter that of the other four methods. When using the graphical method, it is advisable that more than one person select the slope or that the same person fits the same data several times to minimize the effect of subjectivity. Also, a long study period should be used (at least 60 days) to ensure that loops affected by large amounts of barometric-pressure-independent water-level change do not significantly contribute to error in the barometric-efficiency estimate.

Gonthier, Gerard J.

2007-01-01

21

Determination of Barometric Altimeter Errors for the Orion Exploration Flight Test-1 Entry  

Science.gov (United States)

The EFT-1 mission is the unmanned flight test for the upcoming Multi-Purpose Crew Vehicle (MPCV). During entry, the EFT-1 vehicle will trigger several Landing and Recovery System (LRS) events, such as parachute deployment, based on onboard altitude information. The primary altitude source is the filtered navigation solution updated with GPS measurement data. The vehicle also has three barometric altimeters that will be used to measure atmospheric pressure during entry. In the event that GPS data is not available during entry, the altitude derived from the barometric altimeter pressure will be used to trigger chute deployment for the drogues and main parachutes. Therefore it is important to understand the impact of error sources on the pressure measured by the barometric altimeters and on the altitude derived from that pressure. There are four primary error sources impacting the sensed pressure: sensor errors, Analog to Digital conversion errors, aerodynamic errors, and atmosphere modeling errors. This last error source is induced by the conversion from pressure to altitude in the vehicle flight software, which requires an atmosphere model such as the US Standard 1976 Atmosphere model. There are several secondary error sources as well, such as waves, tides, and latencies in data transmission. Typically, for error budget calculations it is assumed that all error sources are independent, normally distributed variables. Thus, the initial approach to developing the EFT-1 barometric altimeter altitude error budget was to create an itemized error budget under these assumptions. This budget was to be verified by simulation using high fidelity models of the vehicle hardware and software. The simulation barometric altimeter model includes hardware error sources and a data-driven model of the aerodynamic errors expected to impact the pressure in the midbay compartment in which the sensors are located. The aerodynamic model includes the pressure difference between the midbay compartment and the free stream pressure as a function of altitude, oscillations in sensed pressure due to wake effects, and an acoustics model capturing fluctuations in pressure due to motion of the passive vents separating the barometric altimeters from the outside of the vehicle.

Brown, Denise L.; Munoz, Jean-Philippe; Gay, Robert

2011-01-01

22

Detecting the vulnerability of groundwater in semi-confined aquifers using barometric response functions  

Science.gov (United States)

The use of barometric response functions (BRFs) for detecting the presence of fully penetrating, highly conductive bodies within aquifer confining layers that present potential pathways for contaminants is explored. BRFs are determined from borehole water level (WL) and barometric pressure (Bp) records. Past studies have shown that confining layer properties can be estimated from BRFs, providing a potential link between BRFs and the concept of groundwater vulnerability. Existing analytical models that predict the BRF from system properties assume homogeneity within the aquifer and its confining layer, conditions which are seldom satisfied in nature. The impact of partially and fully penetrating, high diffusivity heterogeneities within a confining layer (representing potential high flow pathways for contaminants) on the BRF is investigated through a suite of three-dimensional, transient numerical simulations of the confining layer-aquifer system. The results are interpreted through comparison with a modified pre-existing analytical model for the BRF. Comparison of numerically and analytically calculated BRFs reveals that the key effect of a localised, fully penetrating, high diffusivity heterogeneity within a low diffusivity confining layer is to reduce the BRF gain with only minor changes to the phase. This impact on the BRF decreases with increasing distance from the heterogeneity. The importance of heterogeneity size is secondary to distance from the borehole and partially penetrating heterogeneities affect the BRF to only a minor extent. Data from a study of the Chalk Aquifer (E. Yorkshire, England) which is semi-confined by heterogeneous glacial sediments display variations in BRFs which are qualitatively similar to those shown by the numerical results. It is suggested that the variation in BRFs estimated from borehole records across a semi-confined aquifer could be used to assess the degree of spatial continuity of low diffusivity lithologies within the confining layer which protect the aquifer against surface sourced contamination, and thus provide a tool to improve groundwater vulnerability assessment.

Odling, N. E.; Perulero Serrano, R.; Hussein, M. E. A.; Riva, M.; Guadagnini, A.

2015-01-01

23

Observando as marés atmosféricas: uma aplicação da placa Arduino com sensores de pressão barométrica e temperatura / Observing the atmospheric tides: an application of the Arduino board with sensors for barometric pressure and temperature  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Apresentamos uma montagem experimental simples para o estudo da maré atmosférica, baseada no uso da placa Arduino Uno. Com essa montagem, o professor de física no Ensino Médio poderá apresentar para seus alunos as oscilações barométricas, um efeito fundamentalmente de origem térmica devido ao aqueci [...] mento da atmosfera produzido pela radiação solar. Apresentamos também uma comparação entre a maré atmosférica e o efeito gravitacional da maré oceânica, destacando as diferenças entre os dois fenômenos. Abstract in english We present a simple experimental apparatus for studying the atmospheric tide based on the use of Arduino Uno board. With this apparatus, the physics teacher in high school can present to your students barometric oscillations, an effect mainly of thermal origin, due to the warming of the atmosphere p [...] roduced by solar radiation. We also present a comparison between atmospheric tide and the gravitational effect of ocean tide, with emphasis on the differences between the two phenomena.

Luiz Raimundo Moreira de, Carvalho; Helio Salim de, Amorim.

2014-09-01

24

Capillary pressure studies under low gravity conditions.  

Science.gov (United States)

For the understanding of short-time adsorption phenomena and high-frequency relaxations at liquid interfaces particular experimental techniques are needed. The most suitable method for respective studies is the capillary pressure tensiometry. However, under gravity conditions there are rather strong limitations, in particular due to convections and interfacial deformations. This manuscript provides an overview of the state of the art of experimental tools developed for short-time and high-frequency investigations of liquid drops and bubbles under microgravity. Besides the brief description of instruments, the underlying theoretical basis will be presented and limits of the applied methods under ground and microgravity conditions will be discussed. The results on the role of surfactants under highly dynamic conditions will be demonstrated by some selected examples studied in two space shuttle missions on Discovery in 1998 and Columbia in 2003. PMID:20350720

Kovalchuk, V I; Ravera, F; Liggieri, L; Loglio, G; Pandolfini, P; Makievski, A V; Vincent-Bonnieu, S; Krägel, J; Javadi, A; Miller, R

2010-12-15

25

A theoretical and experimental investigation of a small-scale solar-powered barometric desalination system  

Energy Technology Data Exchange (ETDEWEB)

This paper describes and evaluates a theoretical and experimental study of a solar-powered barometric desalination system in which drinking water can be distilled from seawater. The paper describes the system and the experimental apparatus used to test a simple design theory. Experimental results are provided and compared with the given theory. A good correlation between theory and experiment indicates that the distillate production rate depends on the heat exchanger effectiveness of the condenser, solar insolation and evaporator pressure. Results are used to provide an outline specification for a device able to provide fresh water to a small family group. (author)

Eames, I.W.; Maidment, G.G.; Lalzad, A.K. [South Bank University, London (United Kingdom). Department of Engineering Systems

2007-08-15

26

A Sensor Fusion Method for Tracking Vertical Velocity and Height Based on Inertial and Barometric Altimeter Measurements  

Directory of Open Access Journals (Sweden)

Full Text Available A sensor fusion method was developed for vertical channel stabilization by fusing inertial measurements from an Inertial Measurement Unit (IMU and pressure altitude measurements from a barometric altimeter integrated in the same device (baro-IMU. An Extended Kalman Filter (EKF estimated the quaternion from the sensor frame to the navigation frame; the sensed specific force was rotated into the navigation frame and compensated for gravity, yielding the vertical linear acceleration; finally, a complementary filter driven by the vertical linear acceleration and the measured pressure altitude produced estimates of height and vertical velocity. A method was also developed to condition the measured pressure altitude using a whitening filter, which helped to remove the short-term correlation due to environment-dependent pressure changes from raw pressure altitude. The sensor fusion method was implemented to work on-line using data from a wireless baro-IMU and tested for the capability of tracking low-frequency small-amplitude vertical human-like motions that can be critical for stand-alone inertial sensor measurements. Validation tests were performed in different experimental conditions, namely no motion, free-fall motion, forced circular motion and squatting. Accurate on-line tracking of height and vertical velocity was achieved, giving confidence to the use of the sensor fusion method for tracking typical vertical human motions: velocity Root Mean Square Error (RMSE was in the range 0.04–0.24 m/s; height RMSE was in the range 5–68 cm, with statistically significant performance gains when the whitening filter was used by the sensor fusion method to track relatively high-frequency vertical motions.

Angelo Maria Sabatini

2014-07-01

27

Pressure capability of BWR containment vessel under severe accident conditions  

International Nuclear Information System (INIS)

In the case of a severe accident of a LWR, excessive internal pressure loading beyond design pressure is possible to act on a containment vessel statically or dynamically. In the present paper, three kinds of limit pressures are calculated from finite element analyses in order to determine the pressure capability of a Mark II type BWR containment vessel under a severe accident condition. Three kinds of limit pressures calculated are as follows: (1) the limit pressure for the global collapse of a containment vessel, (2) the limit pressure for the bifurcation buckling of a torispherical head of a containment vessel under statically applied internal pressure, and (3) the limit pressure for the bifurcation buckling of a torispherical head of a containment vessel under dynamically applied internal pressure. The safety margin of a containment vessel is discussed by comparing the calculated limit pressures with the design pressure. (author)

28

Initial conditional effect on pressure waves in an axisymmetric jet  

Science.gov (United States)

A pair of microphones (separated axially by 5.08 cm and laterally by 1.3 cm) are placed on either side of the jet centerline to investigate coherent pressure fluctuations in an axisymmetric jet at Strouhal numbers less than unity. Auto-spectra, transfer-function, and coherence measurements are made for a tripped and untripped boundary layer initial condition. It was found that coherent acoustic pressure waves originating in the upstream plenum chamber propagate a greater distance downstream for the tripped initial condition than for the untripped initial condition. In addition, for the untripped initial condition the developmet of the coherent hydrodynamic pressure waves shifts downstream.

Miles, Jeffrey H.; Raman, Ganesh

29

Initial condition effect on pressure waves in an axisymmetric jet  

Science.gov (United States)

A pair of microphones (separated axially by 5.08 cm and laterally by 1.3 cm) are placed on either side of the jet centerline to investigate coherent pressure fluctuations in an axisymmetric jet at Strouhal numbers less than unity. Auto-spectra, transfer-function, and coherence measurements are made for a tripped and untripped boundary layer initial condition. It was found that coherent acoustic pressure waves originating in the upstream plenum chamber propagate a greater distance downstream for the tripped initial condition than for the untripped initial condition. In addition, for the untripped initial condition the development of the coherent hydrodynamic pressure waves shifts downstream.

Miles, Jeffrey H.; Raman, Ganesh

1988-05-01

30

Barometric tides from ECMWF operational analyses  

Directory of Open Access Journals (Sweden)

Full Text Available The solar diurnal and semidiurnal tidal oscillations in surface pressure are extracted from the operational analysis product of the European Centre for Medium Range Weather Forecasting (ECMWF. For the semidiurnal tide this involves a special temporal interpolation, following Van den Dool et al. (1997. The resulting tides are compared with a "ground truth" tide data set, a compilation of well-determined tide estimates deduced from many long time series of station barometer measurements. These comparisons show that the ECMWF (analysis tides are significantly more accurate than the tides deduced from two other widely available reanalysis products. Spectral analysis of ECMWF pressure series shows that the tides consist of sharp central peaks with modulating sidelines at integer multiples of 1 cycle/year, superimposed on a broad cusp of stochastic energy. The integrated energy in the cusp dominates that of the side-lines. This complicates the development of a simple empirical model that can characterize the full temporal variability of the tides.

Key words. Meteorology and atmospheric dynamics (waves and tides

R. D. Ray

31

Parametric study of electric arcs in aeronautical condition of pressure  

Science.gov (United States)

This work deals with the characterization of DC electric arcs in aeronautical conditions of pressure (104 Pa-105 Pa). Characteristics of electric arcs such as the mean electric field in the arc column, the anode and cathode voltage drops, the length for which the arc extinguishes naturally and the mean energy dissipated per arc have been measured for three current values: 7, 70 and 300 A. The decrease of pressure leads to an increase in the arc length which can be two times longer in pressure conditions reached during a flight than in atmospheric pressure conditions. This is correlated with the variation of the mean electric field with pressure. Consequently, the energy dissipated per arc is also amplified.

Landfried, Romaric; Savi, Laurent; Leblanc, Thierry; Teste, Philippe

2014-08-01

32

High-temperature superconductors under the conditions of high pressure  

International Nuclear Information System (INIS)

The available experimental data on the high pressure impact upon the high-temperature superconductors (HTSC) have been assessed and generalized. Special attention was paid to the crystal structure and transition temperature variations in the HTSC under the conditions of both three- and one-dimensional compression. The correlation between the metallic atoms substitution and the high pressure effects in La-Sr-Cu-O and Y-Ba-Cu-O systems is considered. The critical current evolution under the conditions of high pressure is discussed. 64 refs.; 15 figs.; 3 tabs

33

Modelling of radionuclide migration after underground nuclear explosions by barometric pumping  

International Nuclear Information System (INIS)

During and shortly after a nuclear explosion several noble gas isotopes (131mXe, 133mXe, 133Xe and 135Xe) besides many other fission products are produced. If the explosion is emplaced underground for clandestine test purposes these isotopes, all other fission and activation products are injected into the surrounding rocks. Only the noble gases are able to migrate upwards to the surface through suitable pathways in a fractured permeable medium due to cyclical changes in barometric surface pressure. Possible pathways are cracks, faults or high-permability layers. Times of arrival are much shorter than is expected by diffusion-process alone and may be of orders of magnitude more significant to allow verifying the Comprehensive Nuclear Test Ban Treaty (CTBT). This work calculates time of arrival and shifts in abundance of the radioxenons due to its different molecular diffusion lengths

34

Bulging of pressure tubes at hot spots under LOCA conditions  

International Nuclear Information System (INIS)

During certain postulated loss-of-coolant accidents (LOCA) in a CANDU reactor, some fuel channels can become highly voided within a very short time. Although the pressure tubes are heated mainly by convection and thermal radiation during the LOCA transient, additional heat flow occurs through the bearing pads that are in contact with the pressure tribe. This contact can lead to local hot spots and associated thermal stresses in the pressure tube wall. The two factors that affects the behavior of the pressure tubes during LOCA conditions are the internal pressure and the local heating. Although the effect of internal pressure and of axially uniform temperature has been studied elsewhere, the effect of the local heating on the pressure tube behavior has not been modelled before. This paper shows that the bulging of a pressure tube at a hot spot is the result of the thermal stresses that are developed in a pressure tube during a LOCA transient. To isolate the local heating effect from the internal pressure, a series of single-effect experiments was performed. In these experiments, sections of a CANDU pressure tube were subjected to local heating only. The thermal profile and the local deformation were measured function of time. To quantify the effect of the thermal stresses on the bulging of pressure tubes at hot spots and to develop numerical tools that can predict such bulging, finite element analyses were performed rising the ABAQUS finite element computer code. Use oABAQUS finite element computer code. Use of the measured thermal profiles in the ABAQUS finite element analysis, resulted in very good agreement between the predicted and measured displacements. (author)

35

Pohorje eclogites revisited: Evidence for ultrahigh-pressure metamorphic conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Kyanite eclogites from the Pohorje Mountains, Slovenia, are providing the first evidence of ultrahigh-pressureEo-Alpine metamorphism in the Eastern Alps. Polycrystalline quartz inclusions in garnet, omphacite and kyaniteare surrounded by radial fractures and exhibit microtextures diagnostic for the recovery after coesite breakdown.The non-stoichiometric supersilicic omphacites found in Pohorje eclogites contain up to 5 mol % of Ca-Eskola molecule.Such clinopyroxenes are known to be stable exclusively at high-pressure conditions exceeding 3 GPa. Theirbreakdown during decompression resulted in exolution of quartz rods and needles that are oriented parallel toomphacite c-axis. The absence of coesite is a consequence of near-isothermal decompression during the first stagesof exhumation.Pressure and temperature conditions for the formation of the peak metamorphic mineral assemblages have beenassessed through a consideration of a Fe2+-Mg partitioning between garnet and omphacite pairs, based on differentcalibrations; b the equilibrium between garnet + clinopyroxene + phengite ± kyanite ± quartz/coesite assemblage.Estimated peak pressure and temperature conditions of 3.0-3.1 GPa and 750-783 °C are well within the coesite, i.e.the ultrahigh-pressure stability field.

Mirijam Vrabec

2010-06-01

36

Oxide ceramics under extreme pressure and radiation conditions  

Energy Technology Data Exchange (ETDEWEB)

This experimental study tackles the question how oxide ceramics (ZrO{sub 2} and HfO{sub 2}) respond to the simultaneous exposure to two extreme conditions, pressures up to several ten GPa and irradiation with highly energetic (MeV-GeV) heavy ion projectiles. The combination of these two extreme conditions influences the materials in ways none of those two conditions alone could. In both materials, the exposure to high-fluence irradiations at ambient pressure result in a crystalline-to-crystalline phase transformation from the monoclinic into the first high temperature tetragonal phase. For heavy ions such as Xe, Au, Pb, and U this structural change requires a double impact process. For light ions such as Ni and Cr, the transferred energy does not suffice to induce any transformation indicating an energy loss threshold in ZrO{sub 2} as well as in HfO{sub 2}. If the irradiation is performed under high pressure, the monoclinic-to-tetragonal transformation occurs already at a fluence that is more than one order of magnitude lower, suggesting a single-hit process. Although the ZrO{sub 2} and HfO{sub 2} behave much alike as no two other compound materials, their response to the combination of pressure and ion irradiation differs. X-ray diffraction analysis of the irradiated, pressurized samples and Raman and TEM measurements at ambient conditions revealed that the monoclinic-to-tetragonal transformation in ZrO{sub 2} around 10 GPa is not direct but includes a detour into the cubic high-temperature phase, before the tetragonal structure becomes stable under decompression. For HfO{sub 2}, high fluence irradiation at 10 GPa results in the intensification of the first high pressure phase which is afterwards stabilized to ambient conditions. At higher pressures, additional ion irradiation forces both ceramics to perform a transition into their second high pressure phase (orthorhombic-II) far away from its stability field. This study demonstrates that the combination of ion irradiation and high pressure can serve as a trigger for transitions into different phases and as stabilization mechanism of usually unstable structures.

Schuster, Beatrice

2011-09-15

37

Oxide ceramics under extreme pressure and radiation conditions  

International Nuclear Information System (INIS)

This experimental study tackles the question how oxide ceramics (ZrO2 and HfO2) respond to the simultaneous exposure to two extreme conditions, pressures up to several ten GPa and irradiation with highly energetic (MeV-GeV) heavy ion projectiles. The combination of these two extreme conditions influences the materials in ways none of those two conditions alone could. In both materials, the exposure to high-fluence irradiations at ambient pressure result in a crystalline-to-crystalline phase transformation from the monoclinic into the first high temperature tetragonal phase. For heavy ions such as Xe, Au, Pb, and U this structural change requires a double impact process. For light ions such as Ni and Cr, the transferred energy does not suffice to induce any transformation indicating an energy loss threshold in ZrO2 as well as in HfO2. If the irradiation is performed under high pressure, the monoclinic-to-tetragonal transformation occurs already at a fluence that is more than one order of magnitude lower, suggesting a single-hit process. Although the ZrO2 and HfO2 behave much alike as no two other compound materials, their response to the combination of pressure and ion irradiation differs. X-ray diffraction analysis of the irradiated, pressurized samples and Raman and TEM measurements at ambient conditions revealed that the monoclinic-to-tetragonal transformation in ZrO2 around 10 GPa is not direct but includes a detour into the cubic high-temperature phase, before the tetragonal structure becomes stable under decompression. For HfO2, high fluence irradiation at 10 GPa results in the intensification of the first high pressure phase which is afterwards stabilized to ambient conditions. At higher pressures, additional ion irradiation forces both ceramics to perform a transition into their second high pressure phase (orthorhombic-II) far away from its stability field. This study demonstrates that the combination of ion irradiation and high pressure can serve as a trigger for transitions into different phases and as stabilization mechanism of usually unstable structures.

38

Touch mode micromachined capacitive pressure sensor with signal conditioning electronics  

DEFF Research Database (Denmark)

In the last decades, pressure sensors have been one of the greatest successes of the MEMS industry. Many companies are using them in a variety of applications from the automotive to the environmental field. Currently piezoresistive pressure sensors are the most developed, and a well established technology to design and fabricate these sensors has been implemented. Capacitive pressure sensing, on the other hand, is still an open and really promising field. Results Capacitive microsensors were designed and fabricated (Fig. 1) and an analytical model for touch mode regime, which fitted accurately the measurements done on the devices, was investigated. Fabrication was carried on at Danchip cleanrooms where fusion bonding was used in order to obtain a thin silicon plate on top of a sealed vacuum cavity (Fig. 2). A viable signal conditioning scheme for capacitive pressure sensing was simulated and implemented. A measurement setup was arranged and tested for accuracy and reliability with respect to hysteresis. Finally, designs with different radii of the top plate were characterized by a capacitance versus pressure curve at different frequencies and temperatures (Fig. 3). Industrial possibilities Energy saving systems is one of the key challenges nowadays. In this context, house heating is a priority for environmental issues. For this reason, the possibilities of using a low power consumption technique, such as capacitive pressure sensing, in harsh environments is a concrete market opportunity. Our aim is therefore to develop new technologies based on capacitive sensing to be able to fulfil future requirements in this field.

Fragiacomo, Giulio; Eriksen, Gert F.

2010-01-01

39

A NEW METHOD FOR PRESSURE SENSOR EQUILLIBRATION AND CONDITIONING  

Directory of Open Access Journals (Sweden)

Full Text Available PAPAIOANNOU, G.; PROTOPAPPAS, V.C.; TSOPELAS, P.; MITROGIANNIS, C.; NIANIOS, G.; TASHMAN, S. A New Method for Pressure Sensor Equillibration and Conditioning. Brazilian Journal of Biomotricity, v. 2, n. 3, p. 176-195, 2008. Assessing pressure and contact stress distributions between two adjacent surfaces is a well established research area in biomechanics. Typical applications of measuring the interface pressure include human-machine interfaces in ergonomics, joint congruency studies in orthopaedics, in-vitro cadaveric experimentation and the design of Orthotic-Prosthetic devices. Tekscan pressure sensors are widely used in both in-vivo and in-vitro experiments. An all-round efficient equilibration and calibration approach of the Tekscan sensor system is yet to be clearly defined in the literature and is attempted here for one type of Tekscan sensors. The response of individual sensels from two 5315 Tekscan sensors for quasi-static, repeated constant and dynamic loading was investigated with the use of two methods, namely the “Bladder Method” and the “Pin Method”. In the first method, uniform pressure was applied by a bladder-equilibrator, whereas in the second loads were applied in a sensel-by-sensel approach by means of a pin attached to a frame installed on a material testing machine. The “Pin Method”, although far more laborious, is a better method for equilibration and calibration of sensors, particularly when saturation is prevalent. The pin-method also provides a better characterization of the sensor drift. It was shown that when test conditions resulted in some of the sensels being saturating due to high pressure, the loss of load data from the sensor mat could be estimated using the individual sensel output.

George Papaioannou

2008-09-01

40

A multigrid fluid pressure solver handling separating solid boundary conditions.  

Science.gov (United States)

We present a multigrid method for solving the linear complementarity problem (LCP) resulting from discretizing the Poisson equation subject to separating solid boundary conditions in an Eulerian liquid simulation’s pressure projection step. The method requires only a few small changes to a multigrid solver for linear systems. Our generalized solver is fast enough to handle 3D liquid simulations with separating boundary conditions in practical domain sizes. Previous methods could only handle relatively small 2D domains in reasonable time, because they used expensive quadratic programming (QP) solvers. We demonstrate our technique in several practical scenarios, including nonaxis-aligned containers and moving solids in which the omission of separating boundary conditions results in disturbing artifacts of liquid sticking to solids. Our measurements show, that the convergence rate of our LCP solver is close to that of a standard multigrid solver. PMID:22411885

Chentanez, Nuttapong; Müller-Fischer, Matthias

2012-08-01

41

Photoelectron spectroscopy under ambient pressure and temperature conditions  

International Nuclear Information System (INIS)

We describe the development and applications of novel instrumentation for photoemission spectroscopy of solid or liquid surfaces in the presence of gases under ambient conditions of pressure and temperature. The new instrument overcomes the strong scattering of electrons in gases by the use of an aperture close to the surface followed by a differentially-pumped electrostatic lens system. In addition to the scattering problem, experiments in the presence of condensed water or other liquids require the development of special sample holders to provide localized cooling. We discuss the first two generations of Ambient Pressure PhotoEmission Spectroscopy (APPES) instruments developed at synchrotron light sources (ALS in Berkeley and BESSY in Berlin), with special focus on the Berkeley instruments. Applications to environmental science and catalytic chemical research are illustrated in two examples.

42

Photoelectron Spectroscopy under Ambient Pressure and Temperature Conditions  

International Nuclear Information System (INIS)

We describe the development and applications of novel instrumentation for photoemission spectroscopy of solid or liquid surfaces in the presence of gases under ambient conditions or pressure and temperature. The new instrument overcomes the strong scattering of electrons in gases by the use of an aperture close to the surface followed by a differentially-pumped electrostatic lens system. In addition to the scattering problem, experiments in the presence of condensed water or other liquids require the development of special sample holders to provide localized cooling. We discuss the first two generations of Ambient Pressure PhotoEmission Spectroscopy (APPES) instruments developed at synchrotron light sources (ALS in Berkeley and BESSY in Berlin), with special focus on the Berkeley instruments. Applications to environmental science and catalytic chemical research are illustrated in two examples

43

Photoelectron Spectroscopy under Ambient Pressure and Temperature Conditions  

Energy Technology Data Exchange (ETDEWEB)

We describe the development and applications of novel instrumentation for photoemission spectroscopy of solid or liquid surfaces in the presence of gases under ambient conditions or pressure and temperature. The new instrument overcomes the strong scattering of electrons in gases by the use of an aperture close to the surface followed by a differentially-pumped electrostatic lens system. In addition to the scattering problem, experiments in the presence of condensed water or other liquids require the development of special sample holders to provide localized cooling. We discuss the first two generations of Ambient Pressure PhotoEmission Spectroscopy (APPES) instruments developed at synchrotron light sources (ALS in Berkeley and BESSY in Berlin), with special focus on the Berkeley instruments. Applications to environmental science and catalytic chemical research are illustrated in two examples.

Ogletree, D. Frank; Bluhm, Hendrik; Hebenstreit, Eleonore B.; Salmeron, Miquel

2009-02-27

44

Continuous positive airway pressure setups evaluated at simulated exercise conditions  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english INTRODUCTION: Studies have shown increases in airway opening pressure (Pao) swings and work of breathing (WOB) by different continuous positive airway pressure (CPAP) devices at rest, but few address this issue during exercise. The aim of the present work was to analyze the imposed WOB (WOBi), the a [...] pparent resistance (Rapp) and swings of Pao (deltaP) of 3 CPAP assemblies at simulated exercise conditions. METHODS: The CPAP measures were obtained from: a commercial CPAP (Assembly 1), a high flow CPAP (Assembly 2) and the parallel association of these devices (Assembly 3). In each assembly the spring-loaded positive end-expiratory pressure (PEEP) valve was set to fully opened (mode A) or at the same CPAP pressure (mode B). The exercise protocol simulation, performed manually by a calibrated syringe and a metronome, employed a respiratory frequency of 30 bpm, tidal volume of 2.7 L and inspiratory-to-expiratory ratio of 1. The setups were evaluated at CPAP settings of 5, 10 and 15 cmH2O. RESULTS: The lowest deltaP as well as Rapp and WOBi were obtained with Assembly 3 in mode A with an adjusted CPAP of 10 cmH2O (deltaP=8.1 (0.5) cmH2O, WOBi=1.4 (0.14) cmH2O/L/s, Rapp= 1.3 (0.07) J/s) showed as median (interquartile range). CONCLUSION: For the conditions studied, the best CPAP setup was obtained with mode A.

Marcelo Vieira Leão, Nunes; Antonio, Giannella-Neto; Frederico Caetano Jandre de Assis, Tavares.

2014-06-01

45

Characterization of contaminant transport by gravity, capillarity and barometric pumping in heterogeneous vadose regimes. 1998 annual progress report  

International Nuclear Information System (INIS)

'The intent of this research program is to obtain an improved understanding of vadose zone transport processes and to develop field and modeling techniques required to characterize contaminant transport in the unsaturated zone at DOE sites. For surface spills and near-surface leaks of chemicals, the vadose zone may well become a long-term source of contamination for the underlying water table. Transport of contaminants can occur in both the liquid and gas phases of the unsaturated zone. This transport occurs naturally as a result of diffusion, buoyancy forces (gravity), capillarity and barometric pressure variations. In some cases transport can be enhanced by anisotropies present in hydrologic regimes. This is particularly true for gas-phase transport which may be subject to vertical pumping resulting from atmospheric pressure changes. For liquid-phase flows, heterogeneity may enhance the downward transport of contaminants to the water table depending on soil properties and the scale of the surface spill or near-surface leak. Characterization techniques based upon the dynamics of transport processes are likely to yield a better understanding of the potential for contaminant transport at a specific site than methods depending solely on hydrologic properties derived from a borehole. Such dynamic-characterization techniques can be useful for evaluating sites where contamination presently exists as well as for providing an objective basis to evaluate the efficacy of proposed as well as implemented clean-up technologies. The real-time monitoring of processes that may occur during clean-up of tank waste and the mobility of contaminants beneath the Hanford storage tanks during sluicing operations is one example of how techniques developed in this effort can be applied to current remediation problems. In the future, such dynamic-characterization methods might also be used as part of the site-characterization process for determining suitable locations of new DOE facilities that have the potential of introducing contamination into the vadose zone. This report summarizes work and accomplishments at the midpoint of the 3-year project. The authors have pursued the concept of a vadose-zone observatory (VZO) to provide the field laboratory necessary for carrying out the experiments required to achieve the goals of this research. The approach has been: (1) to carry out plume release experiments at a VZO allowing the acquisition of several different kinds of raw data that, (2) are analyzed and evaluated with the aid of highly detailed, diagnostic numerical models. Because the soil properties of a single VZO are unlikely to cover the full range of conditions encountered at all DOE facilities, the authors anticipate studying at least two and possibly three sites spanning a wide range of hydrologic and geologic properties.'

46

Barometric pumping with a twist: VOC containment and remediation without boreholes. Phase I  

Energy Technology Data Exchange (ETDEWEB)

The majority of the planned remediation sites within the DOE complex are contaminated with volatile organic compounds (VOCs). In many instances the contamination has not reached the water table, does not pose an immediate threat, and is not considered a high priority problem. These sites will ultimately require remediation of some type, either by active vapor extraction, bioremediation, or excavation and ex-situ soil treatment. The cost of remediating these sites can range from $50 K to more than $150 K, depending on site characteristics, contaminants, and remediation method. Additionally, for many remediated sites, residual contamination exists which could not practically be removed by the applied remediation technology. These circumstances result in modest sites with contamination of limited risk, but by regulation they must still be controlled. A remediation solution being developed by Science and Engineering Associates, Inc. (SEA) for the Department of Energy serves as an in-situ containment and extraction methodology for sites where most or all of the contamination resides in the vadose zone soil. The approach capitalizes on the advective soil gas movement resulting from barometric pressure oscillations.

NONE

1996-08-01

47

Micromachined capacitive pressure sensor with signal conditioning electronics  

DEFF Research Database (Denmark)

Micromachined capacitive pressure sensors for harsh environment together with interfacing electronic circuits have been studied in this project. Micro-electromechanical systems (MEMS) have been proposed as substitutes for macro scale sensor’s systems in many different fields and are the only possible solution in many cases where, for example, the dimensions of the sensing element is the limiting factor. Furthermore, MEMS can significantly reduce costs and power consumption being the best candidate for consumer electronics such as mobile phones and cameras, or for the automotive industry where a great deal of sensors are used. Pressure sensors are among the most successful MEMS and are used in a huge variety of applications. In this project an absolute capacitive pressure sensor has been developed with the aim to integrate it in pump control systems to improve the efficiency of the pump. The developed MEMS consist of hermetically sealed vacuum cavities surrounded by two heavily doped silicon layers which constitute the plates of a capacitor. The top plate is also the sensing element being a thin diaphragm that deflects when pressure is applied, thus increasing the capacitance (i.e. the output signal) of the device. Fusion bonding of two wafers has been used in order to obtain the cavities, this is also the only non-standard cleanroom process involved in the fabrication of the transducers. The device developed can measure absolute pressures from 0 to 10 bar with sensitivity up to 80 pF/bar. As a part of the project a suitable interfacing circuit has been developed. Different solutions have been studied in order to optimize size, costs, sensitivity and stability. A comparative analysis between them has been carried out and suggestion for the final product has been proposed. Both the electronic conditioning circuits and the MEMS have been fully described with mathematical models and simulated with electrical networks software for the circuit part and finite element for the sensor part. A good matching between analytical models and simulations results has been achieved. Furthermore, the experimental results are in good agreement with the models proposed. Finally a demonstrator has been fabricated under the constraints of a previously designed case in order to contain costs; modification or re-design of the packaging is in fact one of the major costs for the MEMS industry. This demonstrator has been characterized and presented at Grundfos Direct Sensors A/S and constitute the preliminary work for a new product which is intended target the low power or wireless pressure sensor for harsh environment market.

Fragiacomo, Giulio

2012-01-01

48

Evaluating road surface conditions using dynamic tire pressure sensor  

Science.gov (United States)

In order to best prioritize road maintenance, the level of deterioration must be known for all roads in a city's network. Pavement Condition Index (PCI) and International Roughness Index (IRI) are two standard methods for obtaining this information. However, IRI is substantially easier to measure. Significant time and money could be saved if a method were developed to estimate PCI from IRI. This research introduces a new method to estimate IRI and correlate IRI with PCI. A vehicle-mounted dynamic tire pressure sensor (DTPS) system is used. The DTPS measures the signals generated from the tire/road interaction while driving. The tire/road interaction excites surface waves that travel through the road. DTPS, which is mounted on the tire's valve stem, measures tire/road interaction by analyzing the pressure change inside the tire due to the road vibration, road geometry and tire wall vibration. The road conditions are sensible to sensors in a similar way to human beings in a car. When driving on a smooth road, tire pressure stays almost constant and there are minimal changes in the DTPS data. When driving on a rough road, DTPS data changes drastically. IRI is estimated from the reconstructed road profile using DTPS data. In order to correlate IRI with PCI, field tests were conducted on roads with known PCI values in the city of Brockton, MA. Results show a high correlation between the estimated IRI values and the known PCI values, which suggests that DTPS-based IRI can provide accurate predictions of PCI.

Zhao, Yubo; Wu, H. Felix; McDaniel, J. Gregory; Wang, Ming L.

2014-03-01

49

STOCHASTIC ACCELERATION OF SUPRATHERMAL PARTICLES UNDER PRESSURE BALANCE CONDITIONS  

Energy Technology Data Exchange (ETDEWEB)

The acceleration of suprathermal charged particles in the heliosphere under pressure balance conditions including for the first time the radial spatial particle diffusion and convection in the solar wind is investigated. The physical conditions are derived for which the stationary phase space distribution of suprathermal particles approaches the power-law distribution f{proportional_to}p {sup -5}, which is often seen in spacecraft observations. For separable source distributions in momentum and position we analytically solve the stationary particle transport equation for a radially constant solar wind speed V {sub 0} and a momentum-independent radial spatial diffusion coefficient. The resulting stationary solution at any position within the finite heliosphere is the superposition of an infinite sum of power laws in momentum below and above the (assumed mono-momentum) injection momentum p{sub I} . The smallest spatial eigenvalue determines the flattest power law, to which the full stationary solution approaches at large and small enough momenta. Only for the case of a reflecting inner and a free-escape outer spatial boundary, does one small eigenvalue exist, yielding the power-law distribution f{proportional_to}p {sup -5} at sufficiently large momentum values. The other three spatial boundary conditions imply steeper momentum spectra. Momentum spectra and radial profiles of suprathermal particles are calculated by adopting a uniform outer ring spatial source distribution.

Antecki, T.; Schlickeiser, R. [Institut fuer Theoretische Physik, Lehrstuhl IV: Weltraum und Astrophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Zhang, M., E-mail: ta@tp4.rub.de, E-mail: rsch@tp4.rub.de, E-mail: mzhang@fit.edu [Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL 32901 (United States)

2013-02-10

50

Hulls and structural material waste conditioning by high pressure compaction  

International Nuclear Information System (INIS)

Since 1986 KfK is developing a conditioning process. Main subjects of the investigations were the development of the production technique and the planning of the most important equipments of the process under remote conditions. The process is based on an extensive program of experiments. Inactive bulks of hulls and structural material components were compacted using maximum axial pressure load of about 300 MPa. The product density as function of press force was experimentally determinated. The mechanical loads of the press and tools were estimated for the design of these equipments. The hydraulic press consists a horizontal four-cylinder press. The maximum force of the press is 25 MN. The main advantage is the modular design of the press which is open on all sides. Especially the free accessibility from top is ensured. The report also represents relevant radiological data of the alternative product. Co-60 is the dominating activity of the product due to the effects of the heat production. An amount of 10 kg hull waste or 25 kg top and bottom pieces of the spent fuel assemblies per package is already beyond the Co-60 limit of the KONRAD regulations. The nuclear thermal power of a filled container is approximately sixty times lower compared with a vitrified HLW-container. Since the product shows thermal stability beyond 2000C, this it is suited for a combined disposal together with vitrified HLW-containers in salt bore holes of a geological disposal. The preliminary cost evaluation is based on a reprocessing throughput of 500 tHM per year and volume reduction factor of 5.3. Accordingly there are produced 300 waste packages with hulls only or 625 units with hulls and top and bottom pieces which require 1.6 or 2.3 millions DM respectively

51

Pressurized heavy water reactor fuel behaviour in power ramp conditions  

Science.gov (United States)

In order to check and improve the quality of the Romanian CANDU fuel, an assembly of six CANDU fuel rods has been subjected to a power ramping test in the 14 MW TRIGA reactor at INR. After testing, the fuel rods have been examined in the hot cells using post-irradiation examination (PIE) techniques such as: visual inspection and photography, eddy current testing, profilometry, gamma scanning, fission gas release and analysis, metallography, ceramography, burn-up determination by mass spectrometry, mechanical testing. This paper describes the PIE results from one out of the six fuel rods. The PIE results concerning the integrity, dimensional changes, oxidation, hydriding and mechanical properties of the sheath, the fission-products activity distribution in the fuel column, the pressure, volume and composition of the fission gas, the burn-up, the isotopic composition and structural changes of the fuel enabled the characterization of the behaviour of the Romanian CANDU fuel in power ramping conditions performed in the TRIGA materials testing reactor.

Ionescu, S.; U??, O.; Pârvan, M.; Ohâi, D.

2009-03-01

52

Phase stability limit of c-BN under hydrostatic and non-hydrostatic pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

Phase stability limit of cubic boron nitride (c-BN) has been investigated by the crystal structure search technique. It indicated that this limit is ?1000 GPa at hydrostatic pressure condition. Above this pressure, c-BN turns into a metastable phase with respect to rocksalt type boron nitride (rs-BN). However, rs-BN cannot be retained at 0 GPa owing to its instability at pressure below 250 GPa. For non-hydrostatic pressure conditions, the phase stability limit of c-BN is substantially lower than that under hydrostatic pressure conditions and it is also dramatically different for other pressure mode.

Xiao, Jianwei; Du, Jinglian; Wen, Bin, E-mail: wenbin@ysu.edu.cn; Zhang, Xiangyi [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Melnik, Roderick [M2NeT Lab, Wilfrid Laurier University, Waterloo25, 75 University Ave. West, Ontario, Canada N2L 3C5 (Canada); Kawazoe, Yoshiyuki [New Industry Creation Hatchery Center, Tohoku University, 6-6-4 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579, Japan and Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, 1, Lavyrentyev Avenue, Novosibirsk 630090 (Russian Federation)

2014-04-28

53

An alternative method to Mariotte reservoir system for maintaining constant hydraulic pressure  

International Nuclear Information System (INIS)

Some studies being done to evaluate the suitability of the Yucca Mountain area as a potential radioactive waste repository require the application of a constant water pressure as a boundary condition to study water flow through porous media. The Mariotte reservoir system is commonly used to supply such a boundary condition. Several problems with the Mariotte reservoir system were discovered when it was used to apply a constant water pressure as a boundary condition for a prolonged period. The constant-pressure boundary condition is required for some lab. experiments to study water flow through porous media. The observed problems were caused by temperature and barometric-pressure fluctuations while the flow rates were very small and caused erroneous water flow-rate measurements. An alternative method was developed and used where the water pressure is controlled by regulating its level by using water-level sensing electrodes. The new method eliminated the effects of temperature and barometric-pressure fluctuations and maintained an acceptable accuracy of the estimated water flow rate without compromising the advantage of the Mariotte reservoir

54

Touch mode micromachined capacitive pressure sensor with signal conditioning electronics  

OpenAIRE

In the last decades, pressure sensors have been one of the greatest successes of the MEMS industry. Many companies are using them in a variety of applications from the automotive to the environmental field. Currently piezoresistive pressure sensors are the most developed, and a well established technology to design and fabricate these sensors has been implemented. Capacitive pressure sensing, on the other hand, is still an open and really promising field. Results Capacitive microsensors...

Fragiacomo, Giulio; Eriksen, Gert F.; Christensen, Carsten; Thomsen, Erik Vilain

2011-01-01

55

Comparing temporal and spatial change of pore water pressure and slope stability between wet soil condition and unsaturated soil condition  

Science.gov (United States)

Intense rainfall event during short duration is the most significant reason of landslide in South Korea. Typically, it increases pore water pressure in soil and reduces soil effective stress, which cause landslide. In rainfall-induced landslide, saturation rate of soil at initial condition can affect whether landslide occurs. The objective of this study is to compare temporal and spatial pore water pressure and slope stability between in wet soil and in unsaturated soil under same rainfall condition. Two different infiltration models of TRIGRS 2 (Fortran Program for Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Analysis) were employed to analyze difference of pore water pressure and soil stability under different soil initial conditions. The study site was two small watersheds of Mt. Umyeon in South Korea, where several landslides occurred under an extreme rainfall event on July 27, 2011. Topographical data were generated based on 1 m x 1 m-LiDAR data, and parameters of soil and water characteristics were measured in-situ for TRIGRS 2 simulation. In addition, soil water characteristic curve of the site for the unsaturated soil condition was estimated by the pressure plate method and the filter paper method. The simulation results showed that pore water pressure differently responded between the different water conditions of soil. Ground water table rise appeared relatively faster and higher in the wet soil condition than in the unsaturated soil condition. Moreover, in the wet soil condition, pore water pressure increased with depth while in the unsaturated soil condition, vertical distribution of pore water pressure varied in time. In terms of slope stability, lower factor of safety (FS) were estimated in the wet soil condition than in the unsaturated soil condition. Comparing with landslide initiation positions in reality, FS were calculated more reasonably in the wet soil condition while FS were under-estimated in the unsaturated soil condition. These results indicate that estimating accurate initial water condition of landslide site is important for assessing landslide susceptibility.

Kim, Dongyeob; Im, Sangjun; Lee, Eun Jai; Ahn, Byungkyu

2013-04-01

56

Study of graphite strength properties under conditions of hydrostatic pressure  

International Nuclear Information System (INIS)

Three graphite grades are studied under compression, tension and hydrostaic pressure. It is shown that an increase in the ultimate strength and higher arrangement of strain curves are observed beginning with a certain value of hydrostatic pressure under compression. Several different types of coatings have been tested under compression and none of them gave a reliable protection against of oil in pores and cracks of a specimen as a result of which the strength values in this case are lower that under atmospheric pressure

57

Single particle studies of black liquor gasification under pressurized conditions  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this project is to provide experimental data relevant to pressurized black liquor gasification concepts. Specifically, the following two goals will be achieved: Data on swelling, char yields and component release during pressurized pyrolysis of small samples of black liquor will be obtained. The reactivity and physical behavior of single black liquor droplets during simultaneous pyrolysis and gasification will be investigated. The structure and composition of black liquor char during formation and conversion will be studied. (orig.)

Whitty, K.; Backman, R.; Hupa, M.; Backman, P.; Ek, P.; Hulden, S.T.; Kullberg, M.; Sorvari, V.

1997-10-01

58

Intelligent fiber optic pressure sensor for measurements in extreme conditions  

International Nuclear Information System (INIS)

Application of a fiber optic Fabry-Perot interferometer (FFPI) for measurements of pressure and speed of pressure variation in water reactors of nuclear power plants contributes to improving their safety and long-term metrological stability, which demands for intelligent sensors. It is shown that the manufacturing of a FFPI sensitive element based on a molecular layering nano-technology provides for substantial enhancement of the quality of the gauge. The algorithm of self-calibration of the pressure sensor based on the fact that the length of the FFPI cavity depends on the pressure at a constant spectrum of an optical source is considered. By means of fast tuning of the spectrum of an optical source it is possible to make self-calibration in the course of continuous work of the pressure gauge. It is also shown that the intelligent FFPI pressure sensor maintains metrological characteristics when the total dose of high-neutron/ gamma radiation is over 2 MGy. (authors)

59

CONDITIONS LEADING TO SUDDEN RELEASE OF MAGMA PRESSURE  

Energy Technology Data Exchange (ETDEWEB)

Buildup of magmatic pressures in a volcanic system can arise from a variety of mechanisms. Numerical models of the response of volcanic structures to buildup of pressures in magma in dikes and conduits provide estimates of the pressures needed to reopen blocked volcanic vents. They also can bound the magnitude of sudden pressure drops in a dike or conduit due to such reopening. Three scenarios are considered: a dike that is sheared off by covolcanic normal faulting, a scoria cone over a conduit that is blocked by in-falling scoria and some length of solidified magma, and a lava flow whose feed has partially solidified due to an interruption of magma supply from below. For faulting, it is found that magma would be able to follow the fault to a new surface eruption. A small increase in magma pressure over that needed to maintain flow prior to faulting is required to open the new path, and the magma pressure needed to maintain flow is lower but still greater than for the original dike. The magma pressure needed to overcome the other types of blockages depends on the details of the blockage. For example, for a scoria cone, it depends on the depth of the slumped scoria and on the depth to which the magma has solidified in the conduit. In general, failure of the blockage is expected to occur by radial hydrofracture just below the blocked length of conduit at magma pressures of 10 MPa or less, resulting in radial dikes. However, this conclusion is based on the assumption that the fluid magma has direct access to the rock surrounding the conduit. If, on the other hand, there is a zone of solidified basalt, still hot enough to deform plastically, surrounding the molten magma in the conduit, this could prevent breakout of a hydrofracture and allow higher pressures to build up. In such cases, pressures could build high enough to deform the overlying strata (scoria cone or lava flow). Models of such deformations suggest the possibility of more violent eruptions resulting from sudden shear failure of a scoria cone with material accelerations near 100 m/s{sup 2}.

B. Damjanac; E.S. Gaffney

2005-08-26

60

Beat Pressure and Comparing it with Ascending Aorta Pressure in Normal and Abnormal Conditions  

CERN Document Server

Lumped method (Electrical analogy) is a quick and easy way to model human cardiovascular system. In this paper Lumped method is used for simulating a complete model. It describes a 36-vessel model and cardiac system of human body with details that could show hydrodynamic parameters of cardiovascular system. Also this paper includes modeling of pulmonary, atrium, left and right ventricles with their equivalent circuits. Exact modeling of right and left ventricles pressure with division of ascending aorta into 27 segments increases the accuracy of our simulation. In this paper we show that a calculated pressure for aorta from our complex circuit is near to measured pressure by using advanced medical instruments. Also it is shown that pressure graph from brachial is so near to aortic pressure because of this its pressure signal is usable instead of aortic pressure. Furthermore, obstruction in ascending aorta, brachial and its effects has been showed in different figures.

Ghasemalizadeh, Omid; Firoozabadi, Bahar; Sajadi, Behrang; Zolfonoon, Ali

2014-01-01

61

Analysis of air-conditioning and drying processes using spreadsheet add-in for psychrometric data  

Directory of Open Access Journals (Sweden)

Full Text Available A spreadsheet add-in for the psychrometric data at any barometric pressure and in the air-conditioning and drying temperatureranges was developed using appropriate correlations. It was then used to simulate and analyse air-conditioning and dryingprocesses in the Microsoft Excel environment by exploiting its spreadsheet and graphic potentials. The package allowsone to determine the properties of humid air at any desired state, and to simulate and analyse air-conditioning as well asdrying processes. This, as a teaching tool, evokes the intellectual curiosity of students and enhances their interest and abilityin the thermodynamics of humid-air processes.

E.O. Diemuodeke

2010-01-01

62

Pressurizer and steam generator behavior under PWR transient conditions  

International Nuclear Information System (INIS)

Experiments were conducted in the Loss-of-Fluid Test (LOFT) pressurized water reactor (PWR), at the Idaho National Engineering Laboratory, in which transient phenomena arising from accident events with and without reactor scram were studied. The LOFT PWR is a fully operational, 50-MW(t) facility and is related to a commercial PWR through volumetric scaling principles. The main purpose of the LOFT facility is to provide data for the development of computer codes for PWR transient analyses. Significant thermal-hydraulic differences were observed between the measured and calculated results for those transients in which the pressurizer and steam generator strongly influence the dominant transient phenomena. Pressurizer and steam generator phenomena that occurred during four specific PWR transients in the LOFT facility are discussed

63

Behaviour of polymer muds under high pressure – high temperature conditions  

OpenAIRE

A well is classified as a HPHT (High Pressure High Temperature) well if the static bottomhole temperatures are greater than 350 °C and when the formation pressures exceed 1800 kg/m3 ECD. Mud weights as high as 2400 kg/m3 may be required to maintain a proper well control. The temperature of the drilling fluid when circulating in the well may range from 0 °C to 150 °C and it is important that the drilling fluid maintain acceptable rheological properties within the whole range. The rheologica...

Larsen, Ha?vard

2007-01-01

64

Tribological performance of ashless antiwear additives under extreme pressure conditions  

Science.gov (United States)

Zinc diakyl dithiophosphate (ZDDP) has been used in engine oil for several decades as an antiwear additive. However, ZDDP is the primary source of P, S and Zn in the exhaust, which results in frequent maintenance or replacement of exhaust gas treatment systems. The use of ashless additives is more desirable because of recent environmental regulations. The main goal of this research was to develop a fundamental understanding of how ashless compounds protect the tribological surface in comparison to ZDDP. X-ray absorption near edge structure spectroscopy (XANES) has been performed on tribo and thermal films in order to investigate the chemical properties of films generated from ashless antiwear additives like chemical structure as well as chemical composition. In order to achieve this objective, three approaches were used. First, the relationships between ashless thiophosphates and wear properties under extreme pressure were examined. Ashless antiwear additives properly form their tribofilms on the sliding steel surface, reacting with iron (Fe) which is originated from the substrate. The tribofilms consist of iron phosphates, iron sulfides, and iron sulfates that have lower reduced modulus and hardness compared to tribofilms from ZDDP. However, they are still sufficiently stiff to prevent asperity contact and provide antiwear behavior. In addition, the thickness of protective tribofilms formed with ashless thiophosphates was found to be thicker than the ones formed when ZDDP was used under identical tribological conditions. Secondly, in order to understand the mechanism of tribofilm generation of metal free additives, a fundamental understanding of thermal decomposition of ashless antiwear chemistries and their influence on thermal film formation was derived. The decomposed P- and S- containing products of ZDDP reacted with the metal surface and their own metal cations forming thermal films. In case of metal free dithiophosphates, sulfur species initially formed on the surface very fast, and then, phosphate species formed and diffused into the thermal film. It was one of the reasons why DDP-2 had better antiwear protection. While, DDP-1 with low thermal stability suffered from the oxidation and hydrolysis of thermal film and oil, which was related with poor wear performance. The amine phosphate showed the cross-link of phosphates and the oxidation of thermal film (iron nitrate or nitrite), resulting in its stick-slip behavior and big wear volume. The distinction of wear performance of different chemistries could be interpreted by these different mechanisms of formation of thermal films. Thirdly we examined how ashless fluorinated compounds may influence the formation and the characteristics of tribofilms and in proxy the wear properties. While the general form of the tribofilms were essentially the same with and without the presence of PTFE, an important distinction was the presence of a layer of PTFE on the surface of the tribofilm that prevented its oxidation of the tribofilm and yielded better wear performance.

Kim, Bohoon

65

Systems and methods of monitoring acoustic pressure to detect a flame condition in a gas turbine  

Science.gov (United States)

A method may detect a flashback condition in a fuel nozzle of a combustor. The method may include obtaining a current acoustic pressure signal from the combustor, analyzing the current acoustic pressure signal to determine current operating frequency information for the combustor, and indicating that the flashback condition exists based at least in part on the current operating frequency information.

Ziminsky, Willy Steve (Simpsonville, SC); Krull, Anthony Wayne (Anderson, SC); Healy, Timothy Andrew (Simpsonville, SC), Yilmaz, Ertan (Glenville, NY)

2011-05-17

66

Cable testing under hydrogen burn heat flux and pressure conditions  

International Nuclear Information System (INIS)

A series of tests has been conducted in the Severe Combined Environment Test Chamber (SCETCh) at Sandia National Laboratories (SNL) which simulated the effects of a loss-of-coolant accident (LOCA) and hydrogen deflagration environment on Class 1E nuclear qualified power and control cable. The test environment simulated HECTR predictions of heat flux, moisture, oxygen, and total pressure during a hydrogen burn in a large dry containment resulting from a small-break LOCA involving a 75% core metal-water reaction. None of the cable specimens failed

67

The impact of hepatic pressurization on liver shear wave speed estimates in constrained versus unconstrained conditions  

International Nuclear Information System (INIS)

Increased hepatic venous pressure can be observed in patients with advanced liver disease and congestive heart failure. This elevated portal pressure also leads to variation in acoustic radiation-force-derived shear wave-based liver stiffness estimates. These changes in stiffness metrics with hepatic interstitial pressure may confound stiffness-based predictions of liver fibrosis stage. The underlying mechanism for this observed stiffening behavior with pressurization is not well understood and is not explained with commonly used linear elastic mechanical models. An experiment was designed to determine whether the stiffness increase exhibited with hepatic pressurization results from a strain-dependent hyperelastic behavior. Six excised canine livers were subjected to variations in interstitial pressure through cannulation of the portal vein and closure of the hepatic artery and hepatic vein under constrained conditions (in which the liver was not free to expand) and unconstrained conditions. Radiation-force-derived shear wave speed estimates were obtained and correlated with pressure. Estimates of hepatic shear stiffness increased with changes in interstitial pressure over a physiologically relevant range of pressures (0–35 mmHg) from 1.5 to 3.5 m s?1. These increases were observed only under conditions in which the liver was free to expand while pressurized. This behavior is consistent with hyperelastic nonlinear material models that could be used in taterial models that could be used in the future to explore methods for estimating hepatic interstitial pressure noninvasively. (paper)

68

A fórmula barométrica como instrumento de ensino em Química / The barometric formula as resource for teaching Chemistry  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese [...] Abstract in english The barometric equation is revisited. Restrictions imposed for its derivation are investigated. Results are discussed and related to simple themes of ordinary life. The theoretical models fit to experimental data. Correction for temperature effect improves the fitting in comparison to the barometric [...] formula. The scope for application of the model is discussed.

Otávio Luiz, Bottecchia.

1965-19-01

69

Mechanistic modeling of thermal-mechanical deformation of CANDU pressure tube under localized high temperature condition  

International Nuclear Information System (INIS)

Thermal strain deformation is a pressure tube failure mechanism. The main objective of this paper is to develop mechanistic models to evaluate local thermal-mechanical deformation of a pressure tube in CANDU reactor and to investigate fuel channel integrity under localized contact between fuel elements and pressure tube. The consequence of concern is potential creep strain failure of a pressure tube and calandria tube. The initial focus will be on the case where a fuel rod contacts the pressure tube at full power with highly cooling condition

70

Barometric gas transport along faults and its application to nuclear test-ban monitoring  

International Nuclear Information System (INIS)

Underground nuclear explosions produce a unique but evanescent set of radionuclide gases that potentially can be used in the context of an on-site, test-ban monitoring program to differentiate them from other detected events such as earthquakes or mining activity. In Part I of this report we describe an experiment to evaluate the upward transport of gases from an underground explosion using two gas tracers with very different diffusivities that were released in a 400-m-deep, chemical explosive detonation. The less diffusive (more massive) tracer was detected on a nearby geologic fault 50 days following the detonation while the more diffusive tracer was detected 375 days after release. Computer simulations indicate that the arrival time and the chromatographic behavior of transport are characteristic of barometrically induced flow in a fractured, porous matrix regime. For a hypothetical 1-kiloton fission explosion subject to the same weather and gas transport conditions of the chemical explosion, simulations predict the detectability of argon-37 after 80 days in spite of depletion by radioactive decay. Largely because of the earlier arrival of xenon-133, owing to its lower binary gas diffusivity, the exceedingly short lived isotope should also be detectable - arriving about 30 days earlier than argon. In Part II we consider that our prediction of the detectability of argon and xenon is based upon the small volume (0.00001 m3) sampling technique of the NPE tracer-gas sampling study while actual sampling for radionuclides would involve drawing much larger volume (possibly 0.1-1 m3) gas samples from the near-surface. Extraction of such a large volume of gas from 1-5 meter depths in the soil raises the possibility of significant atmospheric infiltration, leading to substantial dilution of the extracted gas sample. However, an infiltration experiment suggests that significant dilution would not, in fact, occur at the most prolific sampling stations of the earlier gas-tracer study. Of the soil gas being extracted at the shallowest sample site, less than 10% of the gas in the sample volume can be attributed to the infiltration of atmospheric gas. (author)

71

Reasoning under time pressure. A study of causal conditional inference.  

Science.gov (United States)

In this study, we examine the role of beliefs in conditional inference in two experiments, demonstrating a robust tendency for people to make fewer inferences from statements they disbelieve, regardless of logical validity. The main purpose of this study was to test whether participants are able to inhibit this belief effect where it constitutes a bias. This is the case when participants are specifically instructed to assume the truth of the premises. However, Experiment 1 showed that the effect is no less marked than when this instruction is given, than when it is not, although higher ability participants did show slightly less influence of belief (Experiment 2). Contrary to the findings with syllogistic reasoning, use of speeded tasks had no effect on the extent of the belief bias (both experiments), although it did considerably reduce the numbers of inferences that were drawn overall. These findings suggest that the belief bias in conditional inference is less open to volitional control than that associated with syllogistic reasoning. PMID:19261582

Evans, Jonathan St B T; Handley, Simon J; Bacon, Alison M

2009-01-01

72

Experimental and Analytical Investigation of Automotive Ejector Air-Conditioning Cycles Using Low-Pressure Refrigerants  

OpenAIRE

In recent years, ejectors have received much attention because of their ability to reduce throttling losses and increase the efficiency of stationary and mobile air-conditioning systems. While much of the initial research was carried out with high pressure fluids, such as carbon dioxide, it was soon discovered that ejectors can also offer significant advantages in systems that utilize low pressure working fluids. Because throttling losses are generally less significant for low pressure refrig...

Lawrence, Neal; Elbel, Stefan

2012-01-01

73

Thermal stability of extractants and pressurization during heating in adiabatic conditions  

International Nuclear Information System (INIS)

Thermal decomposition of extractants used in nuclear extraction, in the confined spaces can lead to rapid pressurization. To explore the behavior of extractants (TBP, TiAP, TODGA), at high temperature, experiments were conducted in an adiabatic calorimeter in closed-vent conditions. It was found that, amides decomposition would lead to more pressurization than phosphate based extractants and TiAP generates less pressure during decomposition than TBP. The results of these experiments are presented in this paper. (author)

74

Antiferromagnetic critical pressure in URu2Si2 under hydrostatic conditions  

OpenAIRE

The onset of antiferromagnetic order in URu2Si2 has been studied via neutron diffraction in a helium pressure medium, which most closely approximates hydrostatic conditions. The antiferromagnetic critical pressure is 0.80 GPa, considerably higher than values previously reported. Complementary electrical resistivity measurements imply that the hidden order-antiferromagnetic bicritical point far exceeds 1.02 GPa. Moreover, the redefined pressure-temperature phase diagram sugge...

Butch, Nicholas P.; Jeffries, Jason R.; Chi, Songxue; Lea?o, Juscelino B.; Lynn, Jeffrey W.; Maple, M. Brian

2010-01-01

75

Cable condition monitoring in a pressurized water reactor environment  

International Nuclear Information System (INIS)

Oconee Nuclear Station is the first nuclear plant designed, engineered and constructed by Duke Power Company. Even though the accelerated aging method was available to determine the life expectancy of the cable used in the reactor building, no natural aging data was available at that time. In order to be able to verify the condition of the reactor building cable over the life of the plant, an on-going cable monitoring plan was instituted. Various types of cable were selected to be monitored, and they were installed in cable life evaluation circuits in the reactor building. At five year intervals over the life of the plant, cable samples would be removed from these cable life evaluation circuits and tested to determine the effects of the reactor building environment on the integrity of the cable. A review of the cable life evaluation circuits and the results of the evaluation program to date is presented

76

Structure and properties of loaded silica contacts during pressure solution: impedance spectroscopy measurements under hydrothermal conditions  

OpenAIRE

In order to investigate directly the structure and properties of grain boundaries in silicatematerials undergoing pressure solution, in situmeasurements of these properties are required. We report electrical impedance spectroscopy measurements, performed, under hydrothermal conditions, on individual glass–glass and glass-quartz contacts undergoing pressure solution. Resulting estimates of the average grain boundary diffusivity product (Z ¼ DdavC ) for silica transport ...

Noort, R.; Spiers, C. J.; Peach, C. J.

2011-01-01

77

Jump conditions for pressure anisotropy and comparison with the Earth's bow shock  

Directory of Open Access Journals (Sweden)

Full Text Available Taking into account the pressure anisotropy in the solar wind, we study the magnetic field and plasma parameters downstream of a fast shock, as functions of upstream parameters and downstream pressure anisotropy. In our theoretical approach, we model two cases: a the perpendicular shock and b the oblique shock. We use two threshold conditions of plasma instabilities as additional equations to bound the range of pressure anisotropy. The criterion of the mirror instability is used for pressure anisotropy p perp /pparrallel > 1. Analogously, the criterion of the fire-hose instability is taken into account for pressure anisotropy p perp /pparrallel < 1. We found that the variations of the parallel pressure, the parallel temperature, and the tangential component of the velocity are most sensitive to the pressure anisotropy downstream of the shock. Finally, we compare our theory with plasma and magnetic field parameters measured by the WIND spacecraft.

D. F. Vogl

2001-01-01

78

A study on the manufacturing conditions of metal matrix composites by low pressure infiltration process  

International Nuclear Information System (INIS)

Metal fiber preform reinforced aluminum alloy composite as made by the infiltration of molten metal under low pressure casting process. The infiltration behavior of filling pattern and the velocity profile with low-pressure casting process was investigated. The thermocouple was inserted into the preform in order to observe the infiltration behavior. The infiltration of applied pressure time, 1, 2 and 5 s under constant pressure of 0.4 MPa was completely filled during 0.4 s. In these conditions, molten aluminum alloy has successfully infiltrated to FeCrSi metal fiber preform by low-pressure casting process. It was observed the porosity of composites for reliability of composites. The automobile piston was developed with FeCrSi reinforced aluminum alloy that is 0% porosity by the optimal applied pressure and applied pressure time

79

A study on the manufacturing conditions of metal matrix composites by low pressure infiltration process  

Energy Technology Data Exchange (ETDEWEB)

Metal fiber preform reinforced aluminum alloy composite as made by the infiltration of molten metal under low pressure casting process. The infiltration behavior of filling pattern and the velocity profile with low-pressure casting process was investigated. The thermocouple was inserted into the preform in order to observe the infiltration behavior. The infiltration of applied pressure time, 1, 2 and 5 s under constant pressure of 0.4 MPa was completely filled during 0.4 s. In these conditions, molten aluminum alloy has successfully infiltrated to FeCrSi metal fiber preform by low-pressure casting process. It was observed the porosity of composites for reliability of composites. The automobile piston was developed with FeCrSi reinforced aluminum alloy that is 0% porosity by the optimal applied pressure and applied pressure time.

Park, Won Jo; Hessian, Md Anowar; Park, Sung Ho [Gyeongsang National University, Tongyoung (Korea, Republic of); Huh, Sun Chul [Gyeongsang National University, JinJu (Korea, Republic of)

2007-10-15

80

PRESBC: pressure boundary conditions for the K-FIX code. Supplement III  

Energy Technology Data Exchange (ETDEWEB)

Recommended pressure boundary condition modifications are described for the computer code K-FIX, which has been published in the report LA-NUREG-6623 and released to the National Energy Software Center in April 1977.

Travis, J.R.; Rivard, W.C.

1980-07-01

81

Individual Pressure Vessel (PV) and Common Pressure Vessel (CPV) Nickel-Hydrogen Battery Performance Under LEO Cycling Conditions  

Science.gov (United States)

LEO life cycle testing of Individual Pressure Vessel (PV) and Common Pressure Vessel (CPV) nickel-hydrogen cell packs have been sponsored by the NASA Aerospace Flight Battery Program. The cell packs have cycled under both 35% and 60% depth-of- discharge and temperature conditions of -5 C and +lO C. The packs have been on test since as early as 1992 and have generated a substantial database. This report will provide insight into performance trends as a function of the specific cell configuration and manufacturer for eight separate nickel-hydrogen battery cell packs.

Miller, Thomas B.; Lewis, Harlan L.

2004-01-01

82

Antiferromagnetic critical pressure in URu2Si2 under hydrostatic conditions  

Science.gov (United States)

The onset of antiferromagnetic order in URu2Si2 has been studied via neutron diffraction in a helium pressure medium, which most closely approximates hydrostatic conditions. The antiferromagnetic critical pressure is 0.80 GPa, considerably higher than values previously reported. Complementary electrical resistivity measurements imply that the hidden-order-antiferromagnetic bicritical point falls between 1.3 and 1.5 GPa. Moreover, the redefined pressure-temperature phase diagram suggests that the superconducting and antiferromagnetic phase boundaries actually meet at a common critical pressure at zero temperature.

Butch, Nicholas P.; Jeffries, Jason R.; Chi, Songxue; Leão, Juscelino Batista; Lynn, Jeffrey W.; Maple, M. Brian

2010-08-01

83

Flash-type barometric desalination plant powered by waste heat from electricity power stations in Cyprus  

International Nuclear Information System (INIS)

This paper describes and evaluates the results of a study into the problems of freshwater production and shortages on the island of Cyprus. The use of a novel barometric flash-type desalinator, driven by otherwise waste-heat from the island's power-stations, is proposed as a means of increasing freshwater supplies. Mathematical models are described and used to investigate the thermodynamic performance and economic viability of the proposed system. Although water and electricity-supply data for the island of Cyprus were used for the purposes of this investigation, the overall findings are thought to have a wider applicability

84

Shocked Zircons from Araguainha Impact Structure, Brazil: Textural Evidences for High Pressure (>40 GPa) Conditions?  

Science.gov (United States)

Shocked zircons from impact melt breccia from Araguainha Dome (Brazil) were studied to estimate P-T impact conditions. The granulation texture and PDF indicate conditions of pressure higher than 40 GPa and a post-shock temperature of about 1500°C.

Hauser, N.; Matteini, M.; Brown, M.; Novais, E.; Cuadros, F. A.; Pereira, L.; Velsic Maziviero, M.

2014-09-01

85

Unsteady Pressure Measurements around Rotor of an Axial Flow Fan under Stable and Unstable Operating Conditions  

Science.gov (United States)

This study presents some measurement results on the unsteady pressure fields around rotor under stable and unstable operating conditions of an axial flow fan. The unsteady static pressure of rotor passage was measured by using high frequency pressure transducers mounted on the casing wall. The measurements on the unsteady total pressure at rotor inlet and outlet were also conducted with specially designed high frequency total pressure probe. Double Phase-Locked Ensemble Averaging Technique was used for analysis of pressure fluctuations around the rotor at rotating stall onset point. From the results, the unsteady pressure fields during stable and unstable operations of the axial fan were investigated and compared with each other. Particularly one period of rotating stall could be divided into two regions, stalled flow and unstalled flow region respectively. Furthermore the former could be also classified into two zones, bubbled and disturbed region by their features. The flow characteristics for each zone were described in detail and the static and total pressure fields were also analyzed in terms of the pressure distribution along pressure side and suction side on the blade tip profile.

Shin, You Hwan; Kim, Kwang Ho; Kang, Chang Sik

86

Detectability and significance of 12 hr barometric tide in radon-222 signal, drip water flow rate, air temperature and carbon dioxide concentration in an underground tunnel  

Energy Technology Data Exchange (ETDEWEB)

Searching for small periodic signals, such as the 12 hr (S{sub 2}) barometric tide, and monitoring their amplitude as a function of time, can provide important clues on the complex processes affecting fluid transport in unsaturated fractured media under multiple influences. Here, first, we show that a modified spectrogram analysis (MSA) is more efficient than simple Fourier transform to reveal weak periodic signals. Secondly, we show how transient periodic signals can be monitored as a function of time using spectrograms. These methods are applied to time-series of radon and carbon dioxide concentration, drip water flow rates and air temperature measured during several years in the Roselend dead-end tunnel, located in the French Alps near an artificial lake. A weak S{sub 2} line is evidenced in radon concentration, with enhanced amplitude during transient radon bursts. Similarly, the S{sub 2} line is observed using MSA in drip water flow rates which sample mainly fracture flow, as suggested by a hydrochemical analysis, while it is not seen in drip water flow rates sampling matrix flow. In the absence of a strong 24 hr line, the presence of a S{sub 2} line suggests sensitivity to barometric pressure, and thus a significant advective contribution in radon and some drip water transport. No S{sub 2} line is observed in the carbon dioxide time-series. The temporal structure of the S{sub 2} component, however, is not similar in the radon concentration and the drip water flow rates, suggesting, in particular, that drip water does not play a significant role in the generation of radon bursts. Temperature time-series exhibit a significant S{sub 2} contribution, induced by atmospheric pressure, spatially organised in the tunnel, decreasing vertically upwards. A remarkable transient temperature inversion during radon bursts suggests that the additional advective air contributions responsible for the radon bursts occur from the non-saturated rocks below the tunnel. (authors)

Richon, P.; Pili, E. [CEA Bruyeres le Chatel, Dept Analyse Surveillance Environm, 91 (France); Richon, P. [Inst Phys Globe, Equipe Geol Syst Volcan, UMR 7154, F-75252 Paris 05 (France); Perrier, F. [Univ Paris Diderot, Equipe Geomagnetisme, UMR 7154, Inst Phys Globe, F-75252 Paris 05 (France); Sabroux, J. Ch. [CEA Saclay, Inst Radioprotect and Surete Nucl, 91 - Gif-sur-Yvette (France)

2009-03-15

87

Detectability and significance of 12 hr barometric tide in radon-222 signal, drip water flow rate, air temperature and carbon dioxide concentration in an underground tunnel  

International Nuclear Information System (INIS)

Searching for small periodic signals, such as the 12 hr (S2) barometric tide, and monitoring their amplitude as a function of time, can provide important clues on the complex processes affecting fluid transport in unsaturated fractured media under multiple influences. Here, first, we show that a modified spectrogram analysis (MSA) is more efficient than simple Fourier transform to reveal weak periodic signals. Secondly, we show how transient periodic signals can be monitored as a function of time using spectrograms. These methods are applied to time-series of radon and carbon dioxide concentration, drip water flow rates and air temperature measured during several years in the Roselend dead-end tunnel, located in the French Alps near an artificial lake. A weak S2 line is evidenced in radon concentration, with enhanced amplitude during transient radon bursts. Similarly, the S2 line is observed using MSA in drip water flow rates which sample mainly fracture flow, as suggested by a hydrochemical analysis, while it is not seen in drip water flow rates sampling matrix flow. In the absence of a strong 24 hr line, the presence of a S2 line suggests sensitivity to barometric pressure, and thus a significant advective contribution in radon and some drip water transport. No S2 line is observed in the carbon dioxide time-series. The temporal structure of the S2 component, however, is not similar in the radon concenowever, is not similar in the radon concentration and the drip water flow rates, suggesting, in particular, that drip water does not play a significant role in the generation of radon bursts. Temperature time-series exhibit a significant S2 contribution, induced by atmospheric pressure, spatially organised in the tunnel, decreasing vertically upwards. A remarkable transient temperature inversion during radon bursts suggests that the additional advective air contributions responsible for the radon bursts occur from the non-saturated rocks below the tunnel. (authors)

88

The Role of the Velocity Distribution in the Dsmc Pressure Boundary Condition for Gas Mixtures  

Science.gov (United States)

A prescribed pressure is the most common flow boundary condition used in flow simulations. In the Direct Simulation Monte Carlo (DSMC) method, boundary pressure is controlled by the number flux of the simulating molecules entering the domain. In the conventional DSMC algorithm, this number flux is calculated iteratively using sampled values of velocity and number density by means of an expression derived from the Maxwell distribution function. It is known that this procedure does not work well for low speed flows which are of interest in most micro-flow applications and the statistical scatter of the DSMC results is generally stated to be the main reason. However, the Maxwell distribution used in the pressure boundary treatment is valid for equilibrium conditions, and therefore, current implementations of the DSMC pressure boundary treatment are limited to boundaries with sufficiently small rarefaction effects. This is not the case for some practical problems in which highly rarefied flows through the boundaries lead to considerable nonequilibrium effects. In this study, an expression for the species number flux is derived using the Chapman-Enskog velocity distribution to improve the pressure boundary condition. The resulting algorithm is then used for modeling a micro-channel binary gas mixture flow with prescribed pressure boundary conditions.

Ahmadzadegan, Amir; Wen, John; Renksizbulut, Metin

2012-12-01

89

Simulation of subcooled boiling at low pressure conditions with RELAP5-3D computer program  

International Nuclear Information System (INIS)

Simulation of subcooled boiling was carried out using RELAP5 thermal hydraulic computer programs. Both 1D and 3D analyses were carried out with RELAP5/MOD3.2 and RELAP5-3D code. Experimental data from the subcooled boiling experiment at low pressure conditions of Bartel, and Zeitoun and Shoukri were simulated. The RELAP5/MOD3.2 was executed to determine the axial void faction distribution. The predictions of void fraction distributions at low-pressure conditions were underestimated. The same model was used to simulate high pressure subcooled boiling data. High pressure subcooled boiling experiments of Bartolomey and Sabotinov were simulated. The axial void fraction distribution results of RELAP5/MOD3.2 were in a good agreement with the experimental data. (author)

90

A SUGGESTION FOR THE PERMANENT SUPPORT DRIVE IN CONDITIONS OF CONSIDERABLE UNDERGROUND PRESSURE  

Directory of Open Access Journals (Sweden)

Full Text Available In the conditions of considerable underground pressures 12 different technologies were applied during the drift driving in the lignite mine »Titovo Velenje«. The drift is driven largely through marly clays and tuffs with sandstone. The most of applied technologies of performance, especially in the areas with considerable pressures, have not given satisfactory results in view considering the realized dynamics of works, stability maintenance and the cross-section clearance diagram of the drift. The analysis of the used driving technologies and underground pressures serves fur the construction of permanent support, differing basically from standing rigid classical supports. The characteristics of a conceived support, in conditions of considerable underground pressures, enable the construction of a drift with the complete profile, the maintenance of planned working dynamics, the stability and safety of the drift which decreases the cost price for the built meter of the drift.

Darko Vrkljan

1989-12-01

91

Prediction of pressure fluctuation of a hydraulic turbine at no-load condition  

Science.gov (United States)

In order to study characteristics of pressure fluctuation of a turbine during the starting period, a turbine with guide vanes device at no-load condition was investigated using RNG k-epsilon turbulence model. The inner flow distribution and pressure fluctuation characteristics were analyzed. Results show that the pressure fluctuations in the region between the runner and guide vanes are different around the runner inlet. The dominant frequency of pressure fluctuation in the vaneless space close to the casing outlet is the blade passing frequency, while the dominant frequency at the rest region is the twice of the blade passing frequency. The increase of amplitude of pressure fluctuation close to the casing outlet can be attribute to the large scale stall at suction side of the runner inlet.

Chen, T. J.; Wu, X. J.; Liu, J. T.; Wu, Y. L.

2015-01-01

92

Lumped-parameter modeling of PWR downcomer and pressurizer for LOCA conditions  

International Nuclear Information System (INIS)

Two lumped-parameter models, one for a PWR downcomer and the other for a pressurizer, are presented. The models are based on the transient, nonhomogeneous, drift-flux description of two-phase flow, and are suitable for simulating a hypothetical LOCA condition. Effects of thermal nonequilibrium are incorporated in the downcomer model, whereas the pressurizer model can track the interfaces among various flow regimes. Semiimplicit numerical schemes are used for solution. Encouraging results have been obtained for both the models. (author)

93

Snapback testing of the HDR reactor pressure vessel and a primary steam pipe under operating conditions  

International Nuclear Information System (INIS)

A remotely operated snapback excitation system was used for vibration tests under different operating conditions (temperature 20-2850C, internal pressure 0-70 bar). The measured acceleration-, displacement- and strain time histories were analyzed to identify the influence of temperature and internal pressure on the vibration behavior of a real system in its real environment. Additionally, the measurement results were compared with results of pretest calculations of the test load cases. (orig./HP)

94

Analysis of Pressure Fluctuations in a Natural Gas Engine Under Lean Burn Conditions  

OpenAIRE

Abstract We have investigated the cycle-to-cycle pressure fluctuations in a natural gas engine under lean burn conditions. In particular, we have examined the dynamics of the indicated mean effective pressure (IMEP) variations for four different values of the equivalence ratio. For each equivalence ratio, we used a continuous wavelet transform to identify the dominant spectral modes and the number of cycles over which these modes may persist. Our results reveal that when the mixtur...

Sen, A. K.; Litak, G.; Yao, B. -f; Li, G. -x

2009-01-01

95

Virial coefficients and osmotic pressure in polymer solutions in good-solvent conditions  

OpenAIRE

We determine the second, third, and fourth virial coefficients appearing in the density expansion of the osmotic pressure of a monodisperse polymer solution in good-solvent conditions. Using the expected large-concentration behavior, we extrapolate the low-density expansion outside the dilute regime, obtaining the osmotic pressure for any concentration in the semidilute region. Comparison with field-theoretical predictions and experimental data shows that the obtained expres...

Sergio Caracciolomilan U Infn, Milan; Bortolo Matteo Mognettimilan U Infn, Milan; Andrea Pelissettorome U Infn, Rome

2014-01-01

96

On Static Pressure Fluctuation between Sirocco Fan Blades in a Car Air-Conditioning System  

Science.gov (United States)

In this study, special attention is directed to static pressure fluctuation in a sirocco fan for a car air-conditioning system, because it is expected that there is a close connection between the fluid noise and the pressure fluctuation. The final purpose of this study is to clarify the relationship between the static pressure fluctuation between fan blades and the sound noise emitted to the outside of the fan, and to develop an air-conditioning system with highly low noise level. For this purpose, first of all, a new micro probe for the measurement of static pressure fluctuation has been developed. This new micro probe is composed of an L-type static pressure tube (the outer diameter is 0.5 mm and the inner diameter is 0.34 mm) and a very small pressure transducer. This probe exhibits a flat frequency response until approximately 2,000 Hz, and it is set between the blades of the fan rotating at 1,500 rpm. The measurements of the static pressure fluctuation between the blades have been performed, and the intensity of sound source was quantified from the second derivative of the phase-averaged static pressure fluctuation signals on the basis of Ribner's formula (Ribner 1962). The experiments have been made in two different modes, i.e., the cooling mode (FACE MODE) and the heating mode (FOOT MODE). It is shown that the static pressure increases rapidly as the blade approaches to the nose of the casing. It is also found that the sound source for FACE MODE shows the larger value than that for FOOT MODE as a whole. In particular, the largest intensity of sound source is observed when the blade approaches to the nose. From these results, it is confirmed that the present new static pressure probe is useful to specify the distributions of sound source in a sirocco fan.

Sakai, Yasuhiko; Kato, Takaaki; Moriguchi, Yuu; Sakai, Masaharu; Ito, Kouji; Mitsuishi, Yasushi; Nagata, Kouji; Kubo, Takashi

97

LHe Flow Regime/Pressure Drop for D0 Solenoid at Steady State Conditions  

Energy Technology Data Exchange (ETDEWEB)

This paper describes in a note taking format what was learned from several sources on two phase liquid helium flow regimes and pressure drops as applied to the D-Zero solenoid upgrade project. Calculations to estimate the steady state conditions for the D-Zero solenoid at 5, 10 and 15 g/s are also presented. For the lower flow rates a stratified type regime can be expected with a pressure drop less than 0.5 psi. For the higher flow rate a more homogeneous flow regime can be expected with a pressure drop between 0.4 to 1.5 psi.

Rucinski, R.; /Fermilab

1993-03-03

98

Cutting and conditioning of the reactor pressure vessel in the NPP Wuergassen  

International Nuclear Information System (INIS)

NPP Wuergassen was shutdown in 1995 after 23 years of operation. Since 1997 the nuclear power plant is being dismantled. The cutting of the reactor pressure vessel internals was performed between 2003 and 2008. After decontamination the cylindrical parts of the reactor pressure vessel were dissected, the process was finalized in 2010. AREVA has now a 30 years-experience concerning repair, replacement and dismantling of reactor components. In the contribution the authors describe the process planning, manufacture and testing of appropriate remote handled tools, decontamination, dissection of the pressure vessel (320 t), conditioning, packaging and transport of the radioactive waste including radiation protection monitoring.

99

A SiC high-temperature Pressure Sensor Operating in Severe Condition  

OpenAIRE

The tranditional MEMS pressure sensor based on Silicon (Si) material has not been suitable for operating in severe condition such as high-temperature (>500°C). However, as an alternative material, Silicon Carbide (SiC) can be used in hash environment due to its unique properties. Hence this paper presents a touch mode capacitive pressure sensor with double-notches structure, which employs a special SiC-AlN-SiC sandwich structure to achieve high-accuracy pressure measurement in high-temperatu...

Guoqing Hu; Huiyong Yu; Haojie Lv

2012-01-01

100

Effects of pressure condition for LOCA acceleration test profile on equipment integrity  

International Nuclear Information System (INIS)

All equipment related to safety in nuclear power plants must perform their safety functions under defined condition, including postulated DBA condition as well as normal environmental condition. LOCA (Loss of Coolant Accident) of the DBA is the severest condition of high temperature, high pressure and sprayed chemicals during approximately 6 months. Since the perfect qualification of equipment in such LOCA test requires a long time and highly reliable test facility, the realistic LOCA simulation test for equipment qualification is performed with modified shortened test profile enveloping temperature and pressure condition of specific NPP. The detailed process for modification of this LOCA test profile are proposed by Park et al. (2006), based on the Arrhenius equation. However, the shortened test profile may cause quite unfavorable effects on equipment integrity during and after LOCA test. In this paper, we have found that failure possibility of limit switch during LOCA test may be greatly increased due to elevated test pressure in the modified test profile. Therefore, we suggest the refined modification method of LOCA test profile, which is applicable for pressure-vulnerable equipment. (author)

101

Flow instability research on steam generator with straight double-walled heat transfer tube for FBR. Pressure drop under high pressure condition  

International Nuclear Information System (INIS)

For the Steam Generator (SG) with straight double-walled heat transfer tube that used in sodium cooled Faster Breeder Reactor, flow instability is one of the most important items need researching. As the first step of the research, thermal hydraulics experiments were performed under high pressure condition in JAEA with using a straight tube. Pressure drop, heat transfer coefficients and void fraction data were derived. This paper evaluates the pressure drop data with TRAC-BF1 code. The Pffan's correlation for single phase flow and the Martinelli-Nelson's two-phase flow multiplier are found can be well predicted the present pressure drop data under high pressure condition. (author)

102

Determination of optimal conditions for pressure oxidative leaching of Sarcheshmeh Molybdenite concentrate using Taguchi method  

Directory of Open Access Journals (Sweden)

Full Text Available The present research work is based on finding the optimum conditions for pressure oxidative leaching of the molybdenite concentrate to produce technical-grade molybdic oxide (MoO3 with high recovery through further treatment of the filtrate solution. The Taguchi method was used to design and minimize the number of experiments. By using Taguchi orthogonal (L25 array, five parameters (time, temperature, oxygen pressure, pulp density and acid concentration at five levels were selected for 25 experiments. The experiments were designed and carried out in a high-pressure reactor in the presence of nitric acid as solvent and oxidizing agent for the molybdenite concentrate and its ReS2 content. The optimum conditions for pressure leaching of molybdenite were obtained through using Signal to Noise analysis and modified by using Minitab software prediction tool. Furthermore, the optimum condition for an economical pressure leaching of rhenium sulfide (ReS2 was achieved with the same process. Analysis of variance (ANOVA showed that the pulp density is of paramount importance in this process.

Khoshnevisana A.

2012-01-01

103

Analysis of the DHLW cask under normal and hypothetical accident-condition loads with initial pressure  

International Nuclear Information System (INIS)

The paper describes analyses performed for the Defense High-Level Waste (DHLW) cask design that establish an upper limit of 700 lbf/in2 (1 lbf/in2(g) = 6.895x103 Pa) for the cask maximum normal operating pressure (MNOP). Analyses of the cask with this MNOP as an initial condition show that for both normal and hypothetical accident conditions of transport, the stresses are within allowable values. (author)

104

Scram simulation of a control rod drive mechanism of a pressurized water reactor under seismic conditions  

International Nuclear Information System (INIS)

Control rod drop verification experiments of Mitsubishi pressurized water reactor under seismic conditions are performed to confirm the insertion function of control rods into the core. To evaluate these tests, computer simulations are performed. The scram time of control rods under seismic conditions was confirmed to meet the scram function. The behavior of the dropping control rods and the scram time obtained by the computer simulation show a very good correspondence with the results of verification experiments. (author)

105

Study on condensing heat transfer test under high temperature and high pressure conditions  

International Nuclear Information System (INIS)

The condensing heat transfer test of the saturated vapor with vertical upward vapor flow has been done under high temperature and high pressure conditions. (1) Flooding may be occurred at higher vapor velocity. (2) Vertical vapor flow has the effect which increases the condensing heat transfer under laminar film conditions. (3) The measured heat transfer coefficients are larger than that of Nusselt model due to vertical vapor flow. (author)

106

The lubrication characteristics of the vane tip under pressure boundary condition of oil hydraulic vane pump  

International Nuclear Information System (INIS)

The lubrication mode of line contacts between the vane and the camring in an oil hydraulic vane pump has been investigated. First, the variations of the radial force of a vane were calculated from previous measurements of dynamic internal pressure in four chambers surrounding a vane. Next, the lubrication modes were distinguished with Hooke's chart, which is an improvement over Johnson's chart. Finally, the influence of the boundary conditions in the lubrication region on the fluid film lubrication was examined by calculating the film pressure distributions. The results showed that the lubrication mode of the vane tip exists in the rigid-variable-viscosity region, and that discharge pressure higher than 7 MPa greatly affects the oil film pressure in the small and the large arc section because of the Piezo-viscous effect

107

Methodology for assessing channel thermalhydraulics and resultant pressure tube response for severe conditions in CANDU  

International Nuclear Information System (INIS)

In certain postulated accident scenarios included in the design basis of CANDU reactors, channel flows may become low, boil, and stratify. This condition causes the fuel elements and the part of the pressure tube exposed to steam to heat up non-uniformly. For sufficiently steep temperature gradients around the pressure tube circumference and at sufficiently high temperature and pressure, the tube strains non-uniformly outward. During this straining, the tube may rupture before it can contact the surrounding calandria tube and transfer its stored heat to the moderator and cool down. To reduce uncertainties in the assessments of these accidents, a detailed study of the behaviour of the pressure tube needs to be performed. This paper presents an analysis of pressure tube integrity over a range of system parameters relevant to large and small break loss of coolant accidents. This paper addresses pressure tube heatup induced only by channel thermalhydraulics. Other heatup mechanisms such as fuel element pressure tube contact are the subject of a separate study. Some of the results of the analysis are presented

108

Analysis of boron injection transients in pressurized water reactors at natural circulation conditions  

International Nuclear Information System (INIS)

The objective of this paper is to analyze boron injection transients at natural circulation conditions in anticipation of preoperational testing in commercial Pressurized Water Reactors (PWRs). The results of the analysis are expected to aid in identifying important phenomena affecting the mixing process and to help to define the measurements needed to assess the results of such tests

109

Effect of Low Pressure End Conditions on Steam Power Plant Performance  

Directory of Open Access Journals (Sweden)

Full Text Available Most of the electricity produced throughout the world today is from steam power plants and improving the performance of power plants is crucial to minimize the greenhouse gas emissions and fuel consumption. Energy efficiency of a thermal power plant strongly depends on its boiler-condenser operating conditions. The low pressure end conditions of a condenser have influence on the power output, steam consumption and efficiency of a plant. Hence, the objective this paper is to study the effect of the low pressure end conditions on a steam power plant performance. For the study each component was modelled thermodynamically. Simulation was done and the results showed that performance of the condenser is highly a function of its pressure which in turn depends on the flow rate and temperature of the cooling water. Furthermore, when the condenser pressure increases both net power output and plant efficiency decrease whereas the steam consumption increases. The results can be used to run a steam power cycle at optimum conditions.

Ali Syed Haider

2014-07-01

110

Experimental study of the APR+ reactor core flow and pressure distributions under 4-pump running conditions  

International Nuclear Information System (INIS)

Highlights: • Experimental facility with a 1/5 scale was designed to perform various hydraulic tests of an APR+ reactor. • Two kinds of experiments, balanced and unbalanced flows under 4-pump running conditions were carried out. • The core inlet flow rates and exit pressure distributions were measured and analyzed at 257 discrete points. • The coolant mixing characteristics were investigated with the sectional pressure loss coefficients. - Abstract: The core inlet flow rates and exit pressure distributions of an APR+ (Advanced Power Reactor Plus) reactor were evaluated experimentally with the ACOP (APR+ Core Flow and Pressure) test facility. The ACOP test facility was constructed with a linear reduced scale of 1/5 referring to the APR+ reactor. The major flow path from the clod leg to hot leg was preserved with a principle of similarity. The core region was simulated using 257 core simulators, which are representative of the real HIPER fuel assemblies that APR+ reactor adopted. The core inlet flow rates and pressure distributions along the main flow path, which are significant information as an input data to evaluate the core thermal margin and reactor safety, were obtained by differential pressures measured at core simulators representing 257 fuel assemblies, and the static or differential pressures at 584 points, respectively. Two kinds of experiments, 4-pump balanced and unbalanced flow conditions, were conducted to examine the hydraulic characteristics of the reactor coolant flow. The mass balance and overall pressure drop were carefully examined to check the reliability of the obtained values. The inlet flow rates of the two test results showed similar distributions, which met the hydraulic performance requirement. The details of these experiments, the facility, and a data analysis are also described in this paper

111

Quantitative analysis of water dispersion conditions and pressure transmission characteristics of a wet kneaded mass.  

Science.gov (United States)

In our previous paper [Watano S. et al., J. Powder Technology Japan, 37, 362-370 (2000)], a novel compaction tester was developed to quantitatively evaluate the water dispersion condition of a wet kneaded mass prepared by a paddle type kneader. It has been demonstrated that the physical properties of pellets prepared by extrusion granulation after the kneading can be well predicted by the pressure transmission obtained through the compaction tester. This paper describes a more detailed investigation of the water dispersion, its mechanism and pressure transmission characteristics of wet kneaded masses prepared under various operating conditions. First, kneading by a paddle type kneader was conducted to prepare wet masses under various binder contents using different additional methods and different starting materials. Secondly, water dispersion and pressure transmission characteristics of wet masses were investigated. After the wet kneading, the wet kneaded masses were extruded through a dome type extruder and were dried by a fluidized bed to prepare dry pellets. The relationship between water dispersion and pressure transmission can be expressed by a single line, regardless of binder content or methods of addition. This implies that these parameters have no effect on the water dispersion condition of the wet kneaded mass prepared by a high shear paddle type kneader. Different water dispersion characteristics and the mechanism obtained by different starting materials can also be evaluated by the pressure transmission data. Properties of dry pellets can also be predicted by the pressure transmission. It can be concluded that the developed compaction tester can quantitatively evaluate the water dispersion condition of a wet kneaded mass and also predict properties of the final extruded products. PMID:11201227

Watano, S; Furukawa, J; Osako, Y; Yasutomo, T

2001-01-01

112

Experimental study of the pressure fluctuations on propeller turbine runner blades: part 2, transient conditions  

Science.gov (United States)

Transient conditions such as load rejection will often lead to high amplitude pressure fluctuations that will affect a turbine residual-life. If Computational Fluid Dynamic offers a promising tool to study the flow dynamic under transient regime, focused validation data on the runner are still lacking to assess the accuracy of different simulation strategies. Hence within the framework of the AxialT project of the International Consortium on Hydraulic Machines, exploratory measurements of the pressure field on the runner blades of a propeller turbine model were performed in transient conditions. The model was setup on the test stand of the LAMH of Laval University. The test stand control procedures were adapted to mimic transient condition such as load rejection or the transition from a normal operating condition to a speed-no-load condition. The pressure on the runner blades were measured using miniature piezo-resistive transducer linked to a high frequency telemetric system. Using specifically adapted data processing routines, it was possible to characterize the variations of the energy content during the transient runs. Specifically, the main fluctuations appear to occur in the sub-synchronous range in both cases.

Houde, S.; Fraser, R.; Ciocan, G.; Deschênes, C.

2012-11-01

113

Experimental study of the pressure fluctuations on propeller turbine runner blades: part 2, transient conditions  

International Nuclear Information System (INIS)

Transient conditions such as load rejection will often lead to high amplitude pressure fluctuations that will affect a turbine residual-life. If Computational Fluid Dynamic offers a promising tool to study the flow dynamic under transient regime, focused validation data on the runner are still lacking to assess the accuracy of different simulation strategies. Hence within the framework of the AxialT project of the International Consortium on Hydraulic Machines, exploratory measurements of the pressure field on the runner blades of a propeller turbine model were performed in transient conditions. The model was setup on the test stand of the LAMH of Laval University. The test stand control procedures were adapted to mimic transient condition such as load rejection or the transition from a normal operating condition to a speed-no-load condition. The pressure on the runner blades were measured using miniature piezo-resistive transducer linked to a high frequency telemetric system. Using specifically adapted data processing routines, it was possible to characterize the variations of the energy content during the transient runs. Specifically, the main fluctuations appear to occur in the sub-synchronous range in both cases.

114

Numerical simulation of pressure fluctuation in 1000MW Francis turbine under small opening condition  

International Nuclear Information System (INIS)

In order to study the cause of abnormal vibration in large Francis turbine under small opening condition, CFD method was adopted to analyze the flow filed and pressure fluctuation. Numerical simulation was performed on the commercial CFD code Ansys FLUENT 12, using DES method. After an effective validation of the computation result, the flow behaviour of internal flow field under small opening condition is analyzed. Pressure fluctuation in different working mode is obtained by unsteady CFD simulation, and results is compared to study its change. Radial force fluctuation is also analyzed. The result shows that the unstable flow under small opening condition leads to an increase of turbine instability in reverse pump mode, and is one possible reason of the abnormal oscillation.

115

Impacts of static pressure set level on HVAC energy consumption and indoor conditions  

Energy Technology Data Exchange (ETDEWEB)

Air static pressure must be maintained at a certain level leaving the air-handling unit (AHU) to force a suitable amount of air through the terminal boxes. However, an excessive static pressure level is often used due to (1) lack of a control device in a constant-volume (CV) system, (2) a malfunctioning control device in a variable-air-volume (VAV) system, and (3) fear of failure to maintain room temperature. High static pressure often develops excessive damper leakage in older mixing boxes. This results in an appropriate mixing of hot and cold air for dual-duct systems, excessive reheat in single-duct systems, and an excessive amount of air entering the space. Consequently, the actual fan power and heating and cooling energy consumption all become significantly higher than the design values. Even worse, the system may not be able to maintain room conditions due to unwanted simultaneous heating and cooling and may be noisy due to the excessive static pressure. This paper proposed to control the hot duct pressure and the variable-frequency drives (VFDs) to control the fan static, i.e., the cold duct pressure for dual-duct air-handling units. Both a theoretical analysis and results from a case study are presented in this paper.

Liu, M.; Zhu, Y.; Claridge, D.E. [Texas A and M Univ., College Station, TX (United States). Energy Systems Lab.; White, E. [UTMB, Galveston, TX (United States). Energy Management Operation

1997-12-31

116

Improvement of the RELAP5 subcooled boiling model for low pressure conditions  

International Nuclear Information System (INIS)

The RELAP5/MOD3.2.2 Gamma code was assessed against low pressure subcooled boiling experiments performed by Zeitoun and Shoukri [1] in a vertical annulus. The predictions of subcooled boiling bubbly flow showed that the present version of the RELAP5 code underestimates the void fraction growth along the tube. To improve the void fraction prediction at low pressure conditions a set of model changes is proposed, which includes modifications of bubbly-slug transition criterion, drift-flux model, interphase heat transfer coefficient and wall evaporation modeling. The improved experiment predictions with the modified RELAP5 code are presented and analysed. (author)

117

Virial coefficients and osmotic pressure in polymer solutions in good-solvent conditions  

CERN Document Server

We determine the second, third, and fourth virial coefficients appearing in the density expansion of the osmotic pressure of a monodisperse polymer solution in good-solvent conditions. Using the expected large-concentration behavior, we extrapolate the low-density expansion outside the dilute regime, obtaining the osmotic pressure for any concentration in the semidilute region. Comparison with field-theoretical predictions and experimental data shows that the obtained expression is quite accurate. The error is approximately 1-2% below the overlap concentration and rises at most to 5-10% in the limit of very large polymer concentrations.

Caracciolo, S; Pelissetto, A; Caracciolo, Sergio; Mognetti, Bortolo Matteo; Pelissetto, Andrea

2006-01-01

118

Hydrostaticity and hidden order: effects of experimental conditions on the temperature-pressure phase diagram of URu2Si2  

Science.gov (United States)

The pressure-dependence of the hidden order phase transition of URu2Si2 is shown to depend sensitively upon the quality of hydrostatic pressure conditions during electrical resistivity measurements. Hysteresis in pressure is demonstrated for two choices of pressure medium: the commonly-used mixture of 1:1 Fluorinert FC70/FC77 and pure FC75. In contrast, no hysteresis is observed when the pressure medium is a 1:1 mixture of n-pentane/isoamyl alcohol, as it remains hydrostatic over the entire studied pressure range. Possible ramifications for the interpretation of the temperature-pressure phase diagram of URu2Si2 are discussed.

Butch, N. P.; Jeffries, J. R.; Zocco, D. A.; Maple, M. B.

2009-06-01

119

Valve inlet fluid conditions for pressurizer safety and relief valves in combustion engineering-designed plants. Final report  

International Nuclear Information System (INIS)

The purpose of this study is to assemble documented information for C-E designed plants concerning pressurizer safety and power operated relief valve (PROV) inlet fluid conditions during actuation as calculated by conventional licensing analyses. This information is to be used to assist in the justification of the valve inlet fluid conditions selected for the testing of safety valves and PORVs in the EPRI/PWR Safety/Relief Valve Test Program. Available FSAR/Reload analyses and certain low temperature overpressurization analyses were reviewed to identify the pressurization transients which would actuate the valves, and the corresponding valve inlet fluid conditions. In addition, consideration was given to the Extended High Pressure Liquid Injection event. A general description of each pressurization transient is provided. The specific fluid conditions identified and tabulated for each C-E designed plant for each transient are peak pressurizer pressure, pressure ramp rate at actuation, temperature and fluid state

120

Analysis of brittle fracture conditions in WWER reactor pressure vessel under thermal shock  

International Nuclear Information System (INIS)

The principal steps are shown of computer assessment of the resistance of the WWER pressure vessels to brittle fracture during transients due to thermal shocks in emergency cooling. A pipe with inner diameter of 20 mm was used to show that a typical WWER-440 pressure vessel is always free from brittle fracture. Calculations were made of temperature and stress fields during emergency cooling. An analysis of brittle fracture conditions was performed in accordance with the INTERATOMEHNERGO, an international corporation for cooperation in the nuclear field, standard. Graphs are presented of the typical temperature distribution along the pressure vessel perimeter, of temperature and stress field distribution through vessel thickness, of stress intensity factor dependence on crack depth for different time intervals during pipe failure, and the time and temperature dependence of the stress intensity factor for different crack depths. (J.B.). 7 figs

121

The Rheological Properties of Oil-Based Mud under High Pressure and High Temperature Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available

Designing a proper drilling fluid that can function properly under the conditions of High-Pressure, High-Temperature (HP/HT operations is very challenging. Among these challenges is the alteration of the rheological properties of drilling fluid due to the high temperature and high pressure (Ibeh et. al, 2007. This work investigates the rheological behavior of oil-based drilling fluids with different properties at Ultra-HP/HT conditions using a state-of-the-art viscometer capable of measuring drilling fluids properties up to 600°F and 40,000 psi. For this purpose, two actual oil based mud samples used by industry with the same mud weight (12.5 ppg were chosen to carry out a matrix of experiments. The results of this study led to concluding that the viscosity, yield point and gel strength decrease with increasing temperature (until the mud sample fails, for oil-based mud with regular formulation. This behavior is the result of the thermal degradation of the solid, polymers, and other components of the mud samples and the expansion of the molecular distances which will lower the resistance of the fluid to flow and, hence, its viscosity, yield point, and gel strength. Moreover, it is concluded that the viscosity and yield point increase as the pressure increases. Pressure’s effect on these parameters, however, is more apparent at low temperature (below failure point, for oil-based mud with regular formulation.

Key words: High pressure high temperature; Oil-based mud; Rheology; Rheological properties

Mahmood Amani

2012-07-01

122

Critical heat flux for vertical annulus flow channel under low flow and high pressure conditions  

International Nuclear Information System (INIS)

It is important to understand correctly a CHF under low flow condition for the estimation of the reactor safety and performance in the LWRs. The CHF experiments have been carried out for an internally heated vertical annulus in RCS loop facility at Korea Atomic Energy Research Institute. The experimental conditions cover ranges of pressure from 1.82 to 12.08 MPa, mass flux from 300 to 550 kg/(m2·s) and inlet subcooling of 81 and 210 kJ/kg. The CHF data decrease with increasing pressure at high value of mass flux. For mass flux of about 300 kg/(m2·s), the CHF is little influenced by pressure, except the CHF data at 12.08 MPa. For a fixed inlet subcooling, the CHF data are correlated well by using the dimensionless heat flux and dimensionless mass flux, except the data group of 12.08 MPa. All of the CHF data lie in the annular mist flow region and the CHF mechanism is dryout of liquid film. It seems that the Doerffer correlation and Katto correlation overestimate the CHF for low pressure and lower value of mass flux within the present experimental ranges. The Bowring correlation gives a better prediction than the other two correlation. (author)

123

A modified resistance equation for modeling underwater spark discharge with salinity and high pressure conditions  

International Nuclear Information System (INIS)

This work investigates the performance of underwater spark discharge relating to bubble growth and decay under high pressure and with salinity conditions by introducing a modified form of the resistance equation. Here, we study salinity influence on circuit parameters by fitting the experimental data for which gap resistance is much larger in conductive water than in dielectric water. Accordingly, the resistance equation is modified by considering the influence of both plasma and its surrounding liquid. Thermal radiation effect of the bubble is also studied by comparing two different radiation models. Numerical results predict a larger bubble pressure for saline water but a reduced size and a smaller bubble cycle at a greater water depth. Such study may be useful in many saltwater applications, including that for deep sea conditions

124

Numerical solution of Stokes equations with pressure and filtration boundary conditions  

Energy Technology Data Exchange (ETDEWEB)

A numerical algorithm is presented for two-dimensional Stokes equations (plane and axisymmetric case) with pressure and filtration boundary conditions. The numerical procedure is based on a divergence-free finite element method and is applicable to multiply connected domains. Comparisons between two types of finite elements are performed in order to choose the better one. The numerical method is tested on flows with known numerical and analytical solutions and on different grids. Stress boundary conditions are briefly discussed and compared with pressure ones. The influence of a closely placed outlet on the accuracy of numerical results is studied. Numerical examples are presented, including flow past a system of bodies in a channel, flows in branched channels with or without particles, and in channels of arbitrary shape with filtrating walls. 29 refs., 10 figs., 7 tabs.

Shopov, P.J.; Iordanov, Y.I. (Institute of Mathematics, Sofia (Bulgaria))

1994-05-01

125

Inelastic X-ray scattering experiments at extreme conditions: high temperatures and high pressures  

Directory of Open Access Journals (Sweden)

Full Text Available In this article, we review the present status of experimental techniques under extreme conditions of high temperature and high pressure used for inelastic X-ray scattering (IXS experiments of liquid metals, semiconductors, molten salts, molecular liquids, and supercritical water and methanol. For high temperature experiments, some types of single-crystal sapphire cells were designed depending on the temperature of interest and the sample thickness for the X-ray transmission. Single-crystal diamond X-ray windows attached to the externally heated high-pressure vessel were used for the IXS experiment of supercritical water and methanol. Some typical experimental results are also given, and the perspective of IXS technique under extreme conditions is discussed.

S.Hosokawa

2008-03-01

126

A modified resistance equation for modeling underwater spark discharge with salinity and high pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

This work investigates the performance of underwater spark discharge relating to bubble growth and decay under high pressure and with salinity conditions by introducing a modified form of the resistance equation. Here, we study salinity influence on circuit parameters by fitting the experimental data for which gap resistance is much larger in conductive water than in dielectric water. Accordingly, the resistance equation is modified by considering the influence of both plasma and its surrounding liquid. Thermal radiation effect of the bubble is also studied by comparing two different radiation models. Numerical results predict a larger bubble pressure for saline water but a reduced size and a smaller bubble cycle at a greater water depth. Such study may be useful in many saltwater applications, including that for deep sea conditions.

Zhao, Pengfei; Roy, Subrata, E-mail: roy@ufl.edu [Applied Physics Research Group, Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2014-05-07

127

A SiC high-temperature Pressure Sensor Operating in Severe Condition  

Directory of Open Access Journals (Sweden)

Full Text Available The tranditional MEMS pressure sensor based on Silicon (Si material has not been suitable for operating in severe condition such as high-temperature (>500°C. However, as an alternative material, Silicon Carbide (SiC can be used in hash environment due to its unique properties. Hence this paper presents a touch mode capacitive pressure sensor with double-notches structure, which employs a special SiC-AlN-SiC sandwich structure to achieve high-accuracy pressure measurement in high-temperature environment. In order to get the relation of capacitance and external pressure, the large deflection theory is applied in simulation analysis of the diaphragm deformation. At the same time, the sandwich structure and technical process of the sensor are studied in the paper. The results showed that the sensor has excellent high-temperature performance due to application of SiC and AlN materials, and the sensor has higher sensitivity and longer linear range than traditional single-cavity structure. Consequently, the sensor can be applied to accuracy pressure measuremet in high-temperature and harsh environment.

Guoqing Hu

2012-12-01

128

The effect of pressure on the electrical conductivity of olivine under the hydrogen-rich conditions  

Science.gov (United States)

The influence of pressure on the hydrogen-assisted electrical conductivity in olivine has been studied under conditions of 4-10 GPa and 873-1273 K. Synthetic polycrystalline olivine samples with the water content of 160 ppm wt (Paterson calibration) were used and the electrical conductivity was determined from the results of the impedance spectroscopy. We found that the pressure reduces the hydrogen-assisted electrical conductivity, but its magnitude is small: between 4 and 10 GPa, the difference is a factor of ?2.5 for the same water content and temperature. The pressure dependence is characterized by a negative activation volume and the negative dependence of the pre-exponential factor on pressure. Such anomalous behavior is explained by a model where hydrogen-related defect is considered as a weak inclusion in a strong matrix. We use these new data to calculate the electrical conductivity contrast at the 410-km discontinuity. We found that if the water content of the mantle does not change with depth, there should be a large (a factor of ?10) drop in conductivity from above to below the 410-km discontinuity. In contrast, geophysically inferred electrical conductivity increases at 410-km suggesting the increase in water content from above to below the 410-km discontinuity. The present results are used to compare several previous results obtained at different pressures. It was shown that our results agree well with most of previous studies but not with (Yoshino et al., 2009). Possible causes for this discrepancy are discussed.

Dai, Lidong; Karato, Shun-ichiro

2014-07-01

129

Numerical simulation of magnetohydrodynamic pressure drop in a curved bend under different conditions  

International Nuclear Information System (INIS)

This paper presents a detailed study of liquid-metal flow in a curved bend, under the conditions, when the liquid metal flows first parallel and then perpendicular to the magnetic field, while a constant magnetic field also acts in the transverse direction. The duct has conducting vanadium walls, and liquid metals (lithium, sodium, potassium) have been used as coolants. Magneto hydrodynamic (MHD) equations have been developed in three dimensions in the modified toroidal coordinate system. These coupled sets of equations then have been solved using finite difference techniques and an extended SIMPLER algorithm approach. Calculation of MHD pressure drop has been made for three different liquid metals, lithium, sodium and potassium. The results for curved bend indicate an immense axial MHD pressure drop. The axial MHD pressure drop increases for an increase in both kinds of magnetic field for all three liquid metals. It is found that the MHD pressure drop increases as the liquid metal flows more and more transverse to the magnetic field. The MHD pressure drop is found to be maximum for sodium and minimum for lithium. (author)

130

The topological strong spatial mixing property and new conditions for pressure approximation  

OpenAIRE

In the context of stationary $\\mathbb{Z}^d$ nearest-neighbour Gibbs measures $\\mu$ satisfying strong spatial mixing, we present a new combinatorial condition (the topological strong spatial mixing property (TSSM)) on the support of $\\mu$ sufficient for having an efficient approximation algorithm for topological pressure. We establish many useful properties of TSSM for studying strong spatial mixing on systems with hard constraints. We also show that TSSM is, in fact, necessa...

Bricen?o, Raimundo

2014-01-01

131

Energy decay for the damped wave equation under a pressure condition  

CERN Document Server

We establish the presence of a spectral gap near the real axis for the damped wave equation on a manifold with negative curvature. This results holds under a dynamical condition expressed by the negativity of a topological pressure with respect to the geodesic flow. As an application, we show an exponential decay of the energy for all initial data sufficiently regular. This decay is governed by the imaginary part of a finite number of eigenvalues close to the real axis.

Schenck, Emmanuel

2009-01-01

132

Inelastic X-ray scattering experiments at extreme conditions: high temperatures and high pressures  

OpenAIRE

In this article, we review the present status of experimental techniques under extreme conditions of high temperature and high pressure used for inelastic X-ray scattering (IXS) experiments of liquid metals, semiconductors, molten salts, molecular liquids, and supercritical water and methanol. For high temperature experiments, some types of single-crystal sapphire cells were designed depending on the temperature of interest and the sample thickness for the X-ray transmission. Single-crystal d...

Hosokawa, S.

2008-01-01

133

Microstructure and spectroscopy studies on cubic boron nitride synthesized under high-pressure conditions.  

OpenAIRE

High-resolution electron microscopy (HREM) studies of the microstructure and specific defects in hexagonal boron nitride (h-BN) precursors and cubic boron nitride (c-BN) crystals made under high-pressure high-temperature conditions revealed the presence of half-nanotubes at the edges of the h-BN particles. Their sp 3 bonding tendency could strongly influence the nucleation rates of c-BN. The atomic resolution at extended dislocations was insufficient to allow us to determin...

Manfredotti, Claudio; Vittone, Ettore

2002-01-01

134

A structural evaluation of the Shippingport reactor pressure vessel for transport impact conditions  

International Nuclear Information System (INIS)

The Shippingport Atomic Power Station in Shippingport, Pennsylvania, is being decommissioned and dismantled. This government-leased property will be returned, in a radiologically safe condition, to its owner. All radioactive material is being removed from the Shippingport Station and transported for burial to the DOE Hanford Reservation in Richland, Washington. The reactor pressure vessel (RPV) will be transported by barge to Hanford. This paper describes an evaluation of the structural response of the RPV to the normal and accident impact test conditions as required by the Code of Federal Regulations. 3 refs., 5 figs., 3 tabs

135

Consideration of loading conditions initiated by thermal transients in PWR pressure vessels  

International Nuclear Information System (INIS)

This report describes the present state of PWR-plants in the Federal Republic of Germany with respect to - the design of the primary pressure boundary - the analysis of thermal transients and resulting loads - the material conditions and neutron fluence - the requirements for protection against fast fracture. The experimental and analytical research and development programs are delineated together with some foreign R and D programs. It is shown that the parameters investigated (loading condition, crack shape and orientation etc.) cover a broad range. Extensive analytical investigations are emphasized. (orig./RW)

136

A test facility for heat transfer, pressure drop and stability studies under supercritical conditions  

International Nuclear Information System (INIS)

Supercritical water (SCW) exhibits excellent heat transfer characteristics and high volumetric expansion coefficient (hence high mass flow rates in natural circulation systems) near pseudo-critical temperature. SCW is being considered as a coolant in some advanced nuclear reactor designs on account of its potential to offer high thermal efficiency, compact size, elimination of steam generator, separator and dryer, making it economically competitive. The elimination of phase change results in elimination of the Critical Heat Flux (CHF) phenomenon. Cooling a reactor at full power with natural instead of forced circulation is generally considered as enhancement of passive safety. In view of this, it is essential to study natural circulation, heat transfer and pressure drop characteristics of supercritical fluids. Carbon-dioxide can be considered to be a good simulant of water for natural circulation at supercritical conditions since the density and viscosity variation of carbon-dioxide follows a parallel curve as that of water at supercritical conditions. Hence, a supercritical pressure natural circulation loop (SPNCL) has been set up in Hall-7, BARC to investigate the heat transfer, pressure drop and stability characteristics of supercritical carbon-dioxide under natural circulation conditions. The details of the experimental facility are presented in this report. (author)

137

High-pressure behavior of cristobalite under quasi-hydrostatic conditions  

Science.gov (United States)

Cristobalite is a high-temperature, low-pressure polymorph of SiO2. It is comprised of a framework of SiO4 tetrahedra, like many other low-pressure silica polymorphs, e.g. quartz tridymite, or coesite. Its cubic form known as ?-cristobalite crystallizes above 1470 ° C and at atmospheric pressure. The tetragonal ?-phase is a metastable polymorph which appears upon cooling of the cubic ?-cristobalite to ambient temperature and it can be found in natural acidic volcanic rocks. High-pressure behavior of ?-cristobalite is of interest form the geological standpoint because it was experimentally observed that under elevated pressures and at ambient temperature this polymorph with 4-fold coordinated silicon can transform to seifertite - a lower mantle phase with octahedrally coordinated Si. The transformational sequence is as follows. The tetragonal ?-cristobalite transforms to a monoclinic cristobalite II near ~1.5 GPa upon hydrostatic compression. The structure of this higher-pressure polymorph was recently solved. Above ~10 GPa cristobalite II is found to transforms to cristobalite X-I. Apart from the recent determination of the unit cell parameters, the structure of the cristobalite X-I still remains unknown. Further compression of cristobalite X-I above pressures exceeding ~35 GPa leads to formation of cristobalite X-II, which is the polymorph reported to have the structure of seifertite. However, there is a large discrepancy among various experimental observations regarding the pressure at which this transition takes place. Motivated by the recent studies, we aim at understanding how the structure of this "bridging phase", cristobalite X-I, is evolving under pressure and how it transforms to the seifertite phase. We performed in-situ single crystal Raman spectroscopy and X-ray diffraction up to 82 GPa in steps of 3-5 GPa. We used diamond-anvil cells with 250 ?m diamond culet size and neon as the pressure-transmitting medium. In-situ Raman spectra indicated the phase transition to cristobalite II near 1.5 GPa and the formation of the X-I phase above 10 GPa, in agreement with previous studies. This high-pressure phase persists up the highest pressures achieved and it is not quenchable - upon decompression it retransforms into a phase with Raman spectra very similar to that of the starting ?-cristabolate. Single crystal X-ray diffraction data were collected at Extreme Conditions Beamline P02.2 at Petra III. We confirmed the phase transition to cristobalite II and further above 10 GPa to the phase X-I. Indexing of the diffraction patterns of the phase X-I collected at 17 GPa yields a primitive monoclinic unit cell with a = 6.5899(9) Å, b = 4.0493(6) Å, c = 6.841(8) Å, ? = 98.15(3)° and the most likely space groups P21/c or P21/n. A preliminary structure analysis reveals that all Si atoms are octahedrally coordinated at this pressure. Single-crystal X-ray diffraction data from experiments at higher pressures are currently being analyzed.

Cernok, Ana; Bykova, Elena; Liermann, Hanns-Peter; Dubrovinsky, Leonid

2014-05-01

138

Using weather data from the internet to study how atmospheric pressure varies with altitude  

Science.gov (United States)

This article presents a simple and motivating activity for schools and colleges that is based on active learning and the use of new technologies to study the variation in atmospheric pressure with height at the lowest altitudes. Students can learn how barometric pressure decreases with height by plotting the atmospheric pressure versus altitude using data obtained from the internet. Using similar methods to those of scientific researchers, the students can learn a practical rule to correct barometric pressure data with altitude, something that is usually expressed at sea level in weather maps.

Moya, A. A.

2014-11-01

139

A new theoretical solution of the effect of atmospheric pressure on water level  

Science.gov (United States)

Based on the partial differential equation governing the effect of atmospheric pressure on water level of confined well, deriving the boundary condition and considering the seepage water between well and aquifer, the author obtained the analytical solution of water level change in time domain under the action of an atmospheric pressure history with the Laplace transform method. This solution is composed of two terms:stable and retarded terms. The stable term is the multiplication of barometric efficiency and simultaneous atmospheric pressure, and it implies the value of water level after infinite time when the atmospheric pressure is a constant from the time in question. The retarded term is the transient process due to the time lag of water exchange between well and aquifer. From the solution, it is obtained that the interference of atmospheric pressure on water level is the integral superimposition of the contribution of all atmospheric pressure changes before the time in question. So that, we further found out the response function of pulsive atmospheric pressure history. Calculation shows: (1) The pulsive response function starts from zero and tends to a steady value, which is proportional to the barometric efficiency, when the time tends to infinity; (2) The retarded time depends on the mechanical property of aquifer and the radius of well. The larger the seepage coefficient, the smaller the radius of well and the thicker the aquifer, then the shorter the retarded time gets. This solution can be used as the theoretical basis for further analysis of the atmospheric effect and practical correcting method in the future.

Zhao, Peng-Jun

1995-05-01

140

Experimental investigation of symmetric and asymmetric heating of pressure tube under accident conditions for Indian PHWR  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer Circumferential temperature gradient for asymmetric heat-up was 400 Degree-Sign C. Black-Right-Pointing-Pointer At same pressure ballooning initiates at lower temperature in asymmetrical heat-up. Black-Right-Pointing-Pointer At 1 MPa ballooning initiated at 408 Degree-Sign C and with expansion rate of 0.005 mm/s. Black-Right-Pointing-Pointer At 2 MPa ballooning initiation at 330 Degree-Sign C and with expansion rate of 0.0056 mm/s. Black-Right-Pointing-Pointer For symmetrical heat-up strain rate was 10 times faster than asymmetric heat-up. - Abstract: In pressurized heavy water reactor (PHWR), under postulated scenario of small break Loss of Coolant Accident (LOCA) coincident with the failure of Emergency Core Cooling System (ECCS), a situation may arise under which reduction in mass flow rate of coolant through individual reactor channel can lead to stratified flow. Such stratified flow condition creates partial uncover of fuel bundle, which creates a circumferential temperature gradient over PT. The present investigation has been carried out to study thermo-mechanical behaviour of PT under asymmetric heating conditions for a 220 MWe PHWR. A 19-pin fuel simulator has been developed in which preferential heating of elements could be done by supplying power to the selected pins. The asymmetric heating of PT has been carried out at pressure 2 MPa and 1 MPa, respectively, by supplying power to upper region heating elements thus creating an half filled stratified flow conditions. The temperature difference up to 425 Degree-Sign C has been observed along top to bottom periphery of PT. A comparison is made between thermo-mechanical behaviour of PT under asymmetrical and symmetrical heat-up, expected from a large break LOCA condition. The radial expansion rate during symmetrical heating is found to be much faster as compared to that for asymmetric ballooning of PT at the same internal pressure. Integrity of PT is found to be maintained under both loading conditions. Heat sink around of test section, simulating moderator is found to be helpful in arresting the rise in temperature for both fuel pins and PT, thus establishing moderator as an effective heat sink under accident conditions.

Yadav, Ashwini K., E-mail: ashwinikumaryadav@gmail.com [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee-247667 (India); Majumdar, P., E-mail: pmajum@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai-400085 (India); Kumar, Ravi, E-mail: ravikfme@iitr.ernet.in [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee-247667 (India); Chatterjee, B., E-mail: barun@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai-400085 (India); Gupta, Akhilesh, E-mail: akhilfme@iitr.ernet.in [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee-247667 (India); Lele, H.G., E-mail: hglele@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)

2013-01-15

141

AMPTRACT: an algebraic model for computing pressure tube circumferential and steam temperature transients under stratified channel coolant conditions  

International Nuclear Information System (INIS)

In a number of postulated accident scenarios in a CANDU reactor, some of the horizontal fuel channels are predicted to experience periods of stratified flow. During this time, the upper fuel elements and part of the pressure tube become exposed to superheated steam and heat-up. The stratified channel coolant condition can lead to a circumferential temperature gradient around the pressure tube. At sufficiently high temperature and channel pressure, the temperature gradient may result in non-uniform (and localized) pressure tube strain. To study pressure tube strain and integrity under stratified flow channel conditions, it is, therefore, necessary to determine the pressure tube circumferential temperature distribution. This paper presents an algebraic model, called AMPTRACT (Algebraic Model for Pressure Tube Transient Circumferential Temperature), developed to give the transient temperature distribution in a closed form. AMPTRACT models the following modes of heat transfer: radiation from the outermost elements to the pressure tube and from the pressure to calandria tube, convection between the fuel elements and the pressure tube and superheated steam, and circumferential conduction from the exposed to submerged part of the pressure tube. An iterative procedure is used to solve the mass and energy equations in closed form for axial steam and fuel-sheath transient temperature distributions. The one-dimensional conduction equation is then solved to obtain the pressure tun is then solved to obtain the pressure tube circumferential transient temperature distribution in a cosine series expansion

142

Pneumatic burst test under 'upper shelf conditions' of a pressure vessel containing an axial defect  

International Nuclear Information System (INIS)

In a programme of burst tests carried out in the 1960's on model steel pressure vessels with through thickness axial cracks, pressurised with water, some vessels when tested at temperatures in the upper part of the Charpy transition range underwent intermittent crack propagation. Each jump in crack length was accompanied by a drop in pressure, followed by a further crack extension on again raising the pressure. This behavior became more pronounced at higher temperatures and crack lengths and was suspected to be due to the low compressibility of the pressurising water and bulging of the pressure vessel shell local to the crack. Consequently, Test V15T1 was carried out using gas as the pressurising medium in order to demonstrate unambiguously that unstable crack propagation can continue if the loading is such as to give constant or increasing stress conditions as the crack propagates, even at temperatures corresponding to ''upper shelf'' Charpy values. Analyses of the test are given using two fracture assessment methods. (author)

143

SAG behaviour of the CANDU pressure tubes under reactor operating conditions  

International Nuclear Information System (INIS)

In the past few years significant advances in the mathematical modelling of the fuel channel behaviour have been made. This is particularly important for a proper prediction of the pressure tube structural integrity during their service life in the reactor. The present paper describe a computational technique of the stress and strain distribution in the pressure tube, in order to simulate the response of the fuel channel assemblies to different operating conditions. Numerical analysis of deformations and stresses are performed using TPSAG code, specialized in thermo-mechanical calculations by the finite element method.The developed computational technique is based on the equivalence of the pressure tube and calandria tube with rods having the same length; this permits to transform the problem of the stress-strain fields calculation in a two-dimensional problem. The Von Misses criterion was used for calculation of the effective stresses and strains and, also, the small deformation approximation was applied in the first order. The thermo-mechanical analysis on the fuel channel assemblies (pressure tube/ garter spring/calandria tube) permits the prediction of the time dependencies of both axial deformation and vertical deflection of the fuel channels. The calculated values are in good agreement with the measured data reported for various channels in different Candu reactors. (author)

144

Improved rat liver decellularization by arterial perfusion under oscillating pressure conditions.  

Science.gov (United States)

One approach of regenerative medicine to generate functional hepatic tissue in vitro is decellularization and recellularization, and several protocols for the decellularization of livers of different species have been published. This appears to be the first report on rat liver decellularization by perfusion under oscillating pressure conditions, intending to optimize microperfusion and minimize damage to the ECM. Four decellularization protocols were compared: perfusion via the portal vein (PV) or the hepatic artery (HA), with (+P) or without (-P) oscillating pressure conditions. All rat livers (n?=?24) were perfused with 1% Triton X-100 and 1% sodium dodecyl sulphate, each for 90?min with a perfusion rate of 5?ml/min. Perfusion decellularization was observed macroscopically and the decellularized liver matrices were analysed by histology and biochemical analyses (e.g. levels of DNA, glycosaminoglycans and hepatocyte growth factor). Livers decellularized via the hepatic artery and under oscillating pressure showed a more homogeneous decellularization and less remaining DNA, compared with the livers of the other experimental groups. The novel decellularization method described is effective, quick (3?h) and gentle to the extracellular matrix and thus represents an improvement of existing methodology. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25185781

Struecker, Benjamin; Butter, Antje; Hillebrandt, Karl; Polenz, Dietrich; Reutzel-Selke, Anja; Tang, Peter; Lippert, Steffen; Leder, Anne; Rohn, Susanne; Geisel, Dominik; Denecke, Timm; Aliyev, Khalid; Jöhrens, Korinna; Raschzok, Nathanael; Neuhaus, Peter; Pratschke, Johann; Sauer, Igor M

2014-09-01

145

Core void fraction distribution under high-temperature high-pressure boil-off conditions  

International Nuclear Information System (INIS)

The prediction of void fraction distributions in a core under boil-off conditions is important for analyzing the core cooling performance during reactor accidents. In this work, boil-off experiments were conducted under high-temperature high-pressure conditions using PWR-type and tight-lattice type (p/d = 1.11) simulated fuel assembly test sections of the Two-Phase flow Test Facility (TPTF). Several existing void fraction correlations and models were assessed against the experimental data. As a result, it has become clear that: 1) while the Chexal-Lellouche model predicts best the present experimental data, the model has a tendency to underestimate void fraction at higher pressures; 2) no significant problems are found in the applicability of the tested correlations and models to the tight-lattice geometry; and 3) void fractions measured by single-beam gamma densitometers tend to be larger than those measured by differential pressure transducers due to the radial void fraction distribution. (author)

146

Measurements in Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions  

Science.gov (United States)

Detailed velocity measurements were made along a flat plate subject to the same dimensionless pressure gradient as the suction side of a modern low-pressure turbine airfoil. Reynolds numbers based on wetted plate length and nominal exit velocity were varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low and high inlet free-stream turbulence intensities (0.2% and 7%) were set using passive grids. The location of boundary-layer separation does not depend strongly on the free-stream turbulence level or Reynolds number, as long as the boundary layer remains non-turbulent prior to separation. Strong acceleration prevents transition on the upstream part of the plate in all cases. Both free-stream turbulence and Reynolds number have strong effects on transition in the adverse pressure gradient region. Under low free-stream turbulence conditions transition is induced by instability waves in the shear layer of the separation bubble. Reattachment generally occurs at the transition start. At Re = 50,000 the separation bubble does not close before the trailing edge of the modeled airfoil. At higher Re, transition moves upstream, and the boundary layer reattaches. With high free-stream turbulence levels, transition appears to occur in a bypass mode, similar to that in attached boundary layers. Transition moves upstream, resulting in shorter separation regions. At Re above 200,000, transition begins before separation. Mean velocity, turbulence and intermittency profiles are presented.

Volino, Ralph J.; Hultgren, Lennart .

2000-01-01

147

Structural integrity assessment of the reactor pressure vessel under the external reactor vessel cooling condition  

Energy Technology Data Exchange (ETDEWEB)

Since the suggestion of External Reactor Vessel Cooling (ERVC), the effects of malting and cooling on the response of structural integrity of the Reactor Pressure Vessel (RPV) under core melting accident conditions have been investigated. This paper describes the vessel response according to the ERVC condition and analysis method. The steady state and transient analysis for the temperature and stress field were performed using ABAQUS. Especially, transient analyses were studied for the variable boundary conditions. To obtain an analogy with real phenomena, the material properties were determined by combining and modifying the existing results considering phase transformation and temperature dependency. The results show that the vessel can be melted if there is no external cooling. Finally, the potential for vessel damage is discussed using the Larson-Miller curve and damage rule. (author)

Kim, Jong-Sung; Jin, Tae-Eun [Korea Power Engineering Company, Inc. (Korea, Republic of)

1998-12-31

148

Determination of the optimum fuel loading strategy in a pressurized water reactor under aperiodic operating conditions  

International Nuclear Information System (INIS)

Starting from a simple model of the burnup behaviour of a pressurized water reactor, a method is described for approximate calculation of the fraction of reload fuel assemblies as a function of full power operating time in the aperiodic mode of operation. A corresponding computational method has been coupled with the algorithm of dynamic optimization. The resulting model for determining optimum fuel loading strategies in the aperiodic mode of operation of a pressurized water reactor (NIPO) allows to take into account outages caused by fuel reloading and burnup enhancement, modified auxiliary power during the latter, and different start-up conditions of the core. Outages caused by fuel reloading and inspection, nuclear fuel cost, load factor during core cycle, mode of operation during burnup enhancement are varying with the cycle index. (author)

149

Dynamic response of berea sandstone shock-loaded under dry, wet and water-pressurized conditions  

International Nuclear Information System (INIS)

A single-stage light-gas gun was used to perform shock-recovery experiments on Berea sandstone under dry, wet and hydrostatically water-pressurized conditions. The samples were impacted by flyer-plates to achieve stress levels in the range 1.3 to 9.8 GPa. The microstructure of the shocked samples was analyzed using scanning electron microscopy (SEM), laser particle analysis and X-ray computed microtomography (XCMT). The dry samples show strongly fragmented and irregularly fractured quartz grains with a considerably reduced porosity, whereas the wet and water-pressurized specimens show less grain damage and less porosity reduction. During shock compression the water in the pores distributes the stresses and therefore the contact force between the grains is reduced. The interaction between the grains during the shock process was modeled by explicitly treating the grain-pore structure using Smooth Particle Hydrodynamics (SPH) and the Discrete Element Method (DEM)

150

Crack initiation and growth under fully plastic conditions with applications to pressure vessel steels  

International Nuclear Information System (INIS)

This paper describes progress made in a three year research program, sponsored by the Electric Power Research Institute to develop a methodology for fracture under large scale plasticity conditions. The ultimate goal in the development of such a methodology is to establish an improved basis for analyzing the effects of flaws (postulated or detected) on the safety margins of pressure boundary components of light water-cooled-type nuclear steam supply systems. The primary application emphasis is for reactor pressure vessels. Additionally, application to thinner section components such as piping can be foreseen. The program undertaken consists of four distinct phases of study. This paper summarizes the results of extensive experimental and analytical investigations undertaken to evaluate potential criteria for crack initiation and growth, the selection of final criteria and the development of a methodology for analyzing crack growth and stability in flawed structures. (orig.)

151

Dissolution of borosilicate glasses under repository conditions of pressure and temperature  

International Nuclear Information System (INIS)

This paper described laboratory experimental work in progress in the UK to examine the mechanisms of fluid buffered interactions of materials at possible repository temperatures and pressures and aims at proposing limiting temperature values for a disposal facility from the geochemist's viewpoint. At present work is concentrated on reconnaissance experiments on dissolution rates of the vitrified waste form and the changes in near-field granite surface chemistry and fissure properties which will have a bearing on nuclide adsorption immediately after release. The major conclusions: in all of the experiments the fluid state remained as liquid since temperatures never exceeded 3740C, under these subcritical conditions pressure decreases dissolution rate; the ability to extrapolate dissolution rate from values of 1000C to about 2000C, together with the maintenance of physical integrity indicate that the glasses studied are likely to be stable and predictable in leach behavior to temperatures well in excess of those currently being considered for disposal; Glass 209 dissolves more slowly over a wide pressure and temperature spectrum than does glass 189, although the latter is easier to fabricate; dissolution rate decreases with increasing time. The principal conclusions of this study so far is that experimental application of realistic repository hydrothermal PT conditions indicate for the first time that current formulations of borosilicate that current formulations of borosilicate glass would appear to provide for an adequate waste disposal medium which would maintain stability and predictable behavior over a wider pressure and temperature spectrum than previously realized, allowing sme latitude in both pre-disposal storage period and eventual loading at the time of disposal

152

Thermal response of a modular high temperature reactor during passive cooldown under pressurized and depressurized conditions  

International Nuclear Information System (INIS)

The concept of inherent safety features of the modular HTR design with respect to passive decay heat removal through conduction, radiation and natural convection was first introduced in the German HTR-module (pebble fuel) design and subsequently extended to other modular HTR design in recent years, e.g. PBMR (pebble fuel), GT-MHR (prismatic fuel) and the new generation reactor V/HTR (prismatic fuel). This paper presents the numerical simulations of the V/HTR using the thermal-hydraulic code THERMIX which was initially developed for the analysis of HTRs with pebble fuels, verified by experiments, subsequently adopted for applications in the HTRs with prismatic fuels and checked against the results of CRP-3 benchmark problem analyzed by various countries with diverse codes. In this paper, the thermal response of the V/HTR (operating inlet/outlet temperatures 490/1000 deg. C) during post shutdown passive cooling under pressurized and depressurized primary system conditions has been investigated. Additional investigations have also been carried out to determine the influence of other inlet/outlet operating temperatures (e.g. 490/850, 350/850 or 350/1000 deg. C) on the maximum fuel and pressure vessel temperature during depressurized cooldown condition. In addition, some sensitivity analyses have also been performed to evaluate the effect of varying the parameters, i.e. decay heat, graphite conductivity, surface emissivity, etc., on the maximum fuel and pressure vessel temn the maximum fuel and pressure vessel temperature. The results show that the nominal peak fuel temperatures remain below 1600 deg. C for all these cases, which is the limiting temperature relating to radioactivity release from the fuel. The analyses presented in this paper demonstrate that the code THERMIX can be successfully applied for the thermal calculation of HTRs with prismatic fuel. The results also provide some fundamental information for the design optimization of V/HTR with respect to its maximum thermal power, operating temperatures, etc

153

The characterization of InN growth under high-pressure CVD conditions  

International Nuclear Information System (INIS)

Gaining insight into the gas phase and surface chemistry processes that govern the growth of InN and indium-rich group III-nitrides alloys is of crucial importance for understanding and controlling their materials properties. High-pressure chemical vapor deposition (HPCVD) has been shown to be a valuable method for achieving this goal. First results show that InN layers can be grown under HPCVD conditions at 850-900 C in the laminar flow regime of the HPCVD reactor at pressures around 15 bar and ammonia to TMI precursor flow ratio below 200. This is a major step towards the growth of indium rich group III-nitride heterostructures due to the close processing windows. The ex situ InN layers analysis shows that the absorption edge in the InN depends strongly on the precursor flow ratio, indicating that the debated InN properties are strongly influenced by the indium-to-nitrogen stoichiometry. By controlling the InN point defect chemistry we showed that the absorption edge shifts from 1.8 eV down to 0.7 eV. The results show a close relation between absorption edge shift in InN and In-N stoichiometry. In order to study the growth under high-pressure CVD conditions, real-time optical characterization techniques have been developed and applied to analyze gas phase constituents as well as the film nucleation and steady state growth at elevated pressures. Principal angle reflection and laser light scattering are employed to study surface chemistry processes at a sub-monolayer ce chemistry processes at a sub-monolayer level, showing their superiority in optimizing and controlling the growth process. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

154

Sulphation of oil shale ash under atmospheric and pressurized combustion conditions  

International Nuclear Information System (INIS)

One of the main problems in conventional combustion boilers firing pulverized oil shale is the corrosion and fouling of heating surfaces, which is caused by sulphur compounds. Another major problem, from the environmental point of view, are the high SO2 emissions. Consequently, the amount of sulphur in flue gases must be reduced. One alternative to lower the SO2, concentration is the use of new technologies, such as pressurized fluidized bed combustion (PFBC). In FBC processes, the sulphur components are usually removed by the addition of limestone (CaCO3) or dolomite (CaCO3 x MgCO3) into the bed. The calcium in these absorbents react with SO2, producing solid CaSO4. However, when burning oil shale, there would be no need to add limestone or dolomite into the bed, due to the initially high limestone content in the fuel (molar ratio Ca/S =10). The capture of sulphur by oil shale ashes has been studied using a pressurized thermogravimetric apparatus (PTGA). The chosen experimental conditions were typical for atmospheric and pressurized fluidized bed combustion. Four different materials were tested - one cyclone ash from an Estonian oil shale boiler, two size fractions of Estonian oil shale and, one fraction of Israeli oil shale. The cyclone ash was found to be the poorest sulphur absorbent. In general, the results from the sulphur capture experiments under both atmospheric and pressurized fluidized bed conditions showed that the oil shale can capture not only its own sulphur but also significant amounts of additional sulphur from another fuel if the fuels are mixed together. (author)

155

Microstructural Changes in SA508 Gr.4N Pressure Vessel Steel with Heat Treatment Conditions  

International Nuclear Information System (INIS)

Low carbon low alloy steels, are used for nuclear reactor pressure vessels, which determine the safety and the life span of nuclear power plant. In addition, they are utilized for long period under very severe conditions such as high pressure, high temperature, and neutron irradiation and corrosion, so that they are requested high strength and toughness, weldability, neutron irradiation resistance. These mechanical properties can be affected by grain size and carbide precipitation behavior that depend on chemical composition and heat treatment condition. It is well known that SA508 Gr.4N steel with higher Ni and Cr contents has excellent mechanical properties due to its enhanced hardenability. However more verification is needed, in order to use for the nuclear plant. This study was initiated to evaluate the effects of metallurgical variables on mechanical properties of SA508 Gr.4N steel as a candidate for the advanced RPV materials. In order to control grain size and carbide morphology, austenitizing and tempering condition were changed. Also SA508 Gr.3 steel was used to compare microstructure and mechanical properties to those of SA508 Gr.4N steel

156

Structural and mechanical properties of dolomite rock under high pressure conditions: A first-principles study  

Energy Technology Data Exchange (ETDEWEB)

The structural behaviour of carbonate minerals under lower mantle pressures, experimentally investigated by means of X-ray diffraction and infrared spectra measurements can be interpreted and difficulties surmounted by first principles quantum mechanical simulations based on density functional theory (DFT). This work is devoted to structural and mechanical properties of CaMg(CO{sub 3}){sub 2}-dolomite mineral. From Birch-Murnaghan equation of state (BM-EoS) applied to the energy-volume data of the dolomite polymorph, we obtain a bulk modulus of 93.7 GPa with a pressure derivative of 4.7, which show suitable agreement with experimental data. Under hydrostatic pressure the mineral system shows an anisotropic compression behaviour and is found to be more compressible in the z direction. The investigation of dolomite mineral structural phase stability under hydrostatic pressure has confirmed previously range-determined but still debated values of structural phase transition. Two phases transitions were encountered when increasing pressure. The first one occurring from dolomite to the orthorhombic calcite-III-like structure was predicted at {proportional_to}34 GPa; and the second one between the calcite III and the aragonite II at {proportional_to}52.5 GPa. This approach overestimates the transition pressure value when confronted to experimental findings. On the other hand the mechanical behaviour of this mineral under ambient and high pressure conditions was studied. To this end we used a stress-strain ab initio based model to calculate the elastic constants of CaMg(CO{sub 3}){sub 2}-dolomite. Based on the trigonal symmetry (space group R3) we found 196.6, 64.4, 54.7, 22.4, 110 and 41.6 GPa for C{sub 11}, C{sub 12}, C{sub 13}, C{sub 14}, C{sub 33} and C{sub 44}, respectively. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Bakri, Z.; Zaoui, A. [Universite Lille Nord de France, LGCgE (EA 4515), Lille 1, Polytech' Lille, Cite Scientifique, Avenue Paul Langevin, 59655 Villeneuve d' Ascq (France)

2011-08-15

157

Mechanical behavior of irradiated fuel-pin cladding evaluated under transient heating and pressure conditions  

International Nuclear Information System (INIS)

Fast breeder fuel-pin cladding has been tested under experimental conditions simulating the temperature and pressure history characteristic of anticipated transient events. Irradiation induces severe reductions in both strength and ductility. Ductility losses are independent of the rate of temperature increase and saturate by a fluence of approx. 2 x 1022 n/cm2 (E > 0.1 MeV). Losses in strength are dependent on the rate of temperature increase but saturate at a fluence of approx.5 x 1022 n/cm2. Evidence is presented to show that fission products are probably responsible for the degradation in mechanical properties

158

Conditioning of waste from the dismantling of reactor pressure vessel components and of core components  

International Nuclear Information System (INIS)

When power reactors are shut down, the treatment of the core components and of the reactor pressure vessel components constitutes a particular task. Due to its special radiological characteristics, this waste must basically be handled using remote-control equipment with regard to the treatment. For its conditioning in a manner appropriate for the final storage, the waste must be dried and packed into suitable packing drums. The solution implemented by GNS and DSD in order to treat this waste from the Wuergassen nuclear power plant is described in the present contribution. (orig.)

159

Hydrostaticity and hidden order: effects of experimental conditions on the temperature-pressure phase diagram of URu2Si2  

OpenAIRE

The pressure-dependence of the hidden order phase transition of URu2Si2 is shown to depend sensitively upon the quality of hydrostatic pressure conditions during electrical resistivity measurements. Hysteresis in pressure is demonstrated for two choices of pressure medium: the commonly-used mixture of 1:1 Fluorinert FC70/FC77 and pure FC75. In contrast, no hysteresis is observed when the pressure medium is a 1:1 mixture of n-pentane/isoamyl alcohol, as it remains hydrostatic...

Butch, Nicholas P.; Jeffries, Jason R.; Zocco, Diego A.; Maple, M. Brian

2009-01-01

160

Experimental Investigation of Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions  

Science.gov (United States)

Modern low-pressure turbine airfoils are subject to increasingly stronger pressure gradients as designers impose higher loading in an effort to improve efficiency and to reduce part count. The adverse pressure gradients on the suction side of these airfoils can lead to boundary-layer separation, particularly under cruise conditions. Separation bubbles, notably those which fail to reattach, can result in a significant degradation of engine efficiency. Accurate prediction of separation and reattachment is hence crucial to improved turbine design. This requires an improved understanding of the transition flow physics. Transition may begin before or after separation, depending on the Reynolds number and other flow conditions, has a strong influence on subsequent reattachment, and may even eliminate separation. Further complicating the problem are the high free-stream turbulence levels in a real engine environment, the strong pressure gradients along the airfoils, the curvature of the airfoils, and the unsteadiness associated with wake passing from upstream stages. Because of the complicated flow situation, transition in these devices can take many paths that can coexist, vary in importance, and possibly also interact, at different locations and instances in time. The present work was carried out in an attempt to systematically sort out some of these issues. Detailed velocity measurements were made along a flat plate subject to the same nominal dimensionless pressure gradient as the suction side of a modern low-pressure turbine airfoil ('Pak-B'). The Reynolds number based on wetted plate length and nominal exit velocity, Re, was varied from 50;000 to 300; 000, covering cruise to takeoff conditions. Low, 0.2%, and high, 7%, inlet free-stream turbulence intensities were set using passive grids. These turbulence levels correspond to about 0.2% and 2.5% turbulence intensity in the test section when normalized with the exit velocity. The Reynolds number and free-stream turbulence level do not have a significant effect on the location of boundary-layer separation unless they are high enough to induce transition upstream of separation. The location and extent of the transition zone, in contrast, depend strongly on Re and TI. The beginning of reattachment closely follows the onset of transition. Under low free-stream turbulence conditions the boundary layer is laminar at separation and then begins to exhibit fluctuations in a finite frequency band in the shear layer over the separation bubble. These fluctuations are due to instability waves. The fluctuations grow in magnitude, higher harmonics are generated, and finally lead to a breakdown to turbulence. Transition begins in the shear layer, but quickly spreads to the near wall region and causes the boundary layer to reattach. The transition is rapid and the resulting turbulence contains a full range of high and low frequencies. Under high free-stream turbulence conditions, slowly growing low-frequency fluctuations are induced in the pretransitional boundary layer by the free-stream. The separation bubbles are considerably thinner than in the low TI cases, resulting in thinner boundary layers at the end of the test wall. At Re=50,000 and 100,000, the pre-transitional boundary layer separates at about the same location as in the low TI cases. Transition occurs through a bypass mode, begins upstream of the corresponding low-TI location, and proceeds in a manner similar to that of an attached boundary layer. Under high TI at Re=200,000 and 300,000, transition begins before separation. The boundary layer may separate, but if it does the separation bubble is very short and does not significantly affect the downstream development of the boundary layer. A comparison is made to previous work in a simulated cascade.

Hultgren, Lennart S.; Volino, Ralph J.

2002-01-01

161

An assessment of the Tongonan geothermal reservoir, Philippines, at high-pressure operating conditions  

Energy Technology Data Exchange (ETDEWEB)

An evaluation of the Tongonan geothermal reservoir was conducted to improve the power recovery through reservoir and process optimization. The performance of the existing production wells was reviewed and the response of the field based on the anticipated production levels was simulated at various operating conditions. The results indicate that the Tongonan geothermal reservoir can be exploited at a high pressure operating condition with substantial improvement in the field capacity. The authors calculate that the Upper Mahiao and the Malitbog sectors of the Tongonan field are capable of generating 395 MWe at 1.0 MPa abs., on top of the existing 112.5 MWe plant, compared with 275 MWe if the field is operated at 0.6 MPa abs. The total capacity for the proposed Leyte A 640 MWe expansion can be generated from these sectors with the additional power to be tapped from Mahanagdong and Alto Peak sectors.

Sarmiento, Z.F.; Aquino, B.G.; Aunzo, Z.P.; Rodis, N.O.; Saw, V.S. [PNOC-Energy Development Corp., Fort Bonifacio (Philippines)

1993-10-01

162

Finite Element Simulation of Photoacoustic Pressure in a Resonant Photoacoustic Cell Using Lossy Boundary Conditions  

DEFF Research Database (Denmark)

The finite-element method (FEM) is used to simulate the photoacoustic signal in a cylindrical resonant photoacoustic cell. Simulations include loss effects near the cell walls that appear in the boundary conditions for the inhomogeneous Helmholtz equation governing the acoustic pressure. Reasonably good agreement is obtained between theoretical results and experimental data. However, it was anticipated that loss mechanisms other than viscous and thermal boundary losses occur and should be included. Nevertheless, the feasibility to use FEM together with the derived boundary conditions to simulate the photoacoustic signal was demonstrated and good agreement with experiments for the actual resonance frequency and the quality factor of the cell was obtained despite its complicated geometry.

Duggen, Lars; Lopes, Natasha

2011-01-01

163

Possibilities of crack mouth opening displacement (CMOD) measurement under boiling and pressurized water reactor conditions  

International Nuclear Information System (INIS)

Fracture mechanics investigations carried out so far in laboratory conditions cover only part of the material stresses, as effects which occur in nuclear powerstations, in particular, such as corrosion and radioactive radiation are largely left out of account. Therefore experiments including these effects were recently carried out in autoclaves, test rigs simulating reactors (HRD experimental plant) and in experimental reactors. An important parameter of experimental fracture mechanics is the measurement of crack opening displacement (COD). The crack opening is measured with socalled clip gauges (transmitters based on strain gauges, which convert mechanical deformation of springs into electrical signals) on standard samples in the laboratory. It was therefore sensible to use these high temperature strain gauges (HTD) for the development of a measuring system for travel for pressurized water and boiling water reactor conditions. (orig.)

164

The osmotic pressure of highly concentrated monoclonal antibody solutions: effect of solution conditions.  

Science.gov (United States)

The behavior of monoclonal antibodies at high concentrations is important in downstream processing, drug formulation, and drug delivery. The objective of this study was to evaluate the osmotic pressure of a highly purified monoclonal antibody at concentrations up to 250 g/L over a range of pH and ionic strength, and in the presence of specific excipients, using membrane osmometry. Independent measurements of the second virial coefficient were obtained using self-interaction chromatography, and the net protein charge was evaluated using electrophoretic light scattering. The osmotic pressure at pH 5 and low ionic strength was >50 kPa for antibody concentrations above 200 g/L. The second virial coefficients determined from the oncotic pressure (after subtracting the Donnan contribution) were in good qualitative agreement with those determined by self-interaction chromatography. The second virial coefficient decreased with increasing ionic strength and increasing pH due to the reduction in intermolecular electrostatic repulsion. The third virial coefficient was negative under all conditions, suggesting that multi-body interactions in this system are attractive. The virial coefficients were essentially unaffected by addition of sucrose or proline. These results have important implications for the analysis of protein-protein interactions in downstream processing at high protein concentrations. PMID:23996891

Binabaji, Elaheh; Rao, Suma; Zydney, Andrew L

2014-03-01

165

Pressurizer  

International Nuclear Information System (INIS)

A thin walled tube is welded on to the coupling of the overpressure protection in the lid of the pressurizer. The tube opening is located above the highest possible water level in the pressurizer occurring at different regimes of the nuclear power plant. The advantage of the configuration is that an elastic steam cushion is always preserved in the pressurizer during an accident. (Ha)

166

Frictional Behavior of Anorthite and Quartz at High Pressure and High Temperature Conditions  

Science.gov (United States)

Most of earthquakes in the crust occurred at the depth of 5 to 20km, and the distribution of mainshocks matches the base of this zone, where is considered to be consistent with brittle-ductile transition zone. The lower boundary on seismicity results from a switch from velocity weakening to velocity strengthening of friction with increasing temperature. The physical properties of rocks associated with elevated temperatures were determined by many frictional experiments. In these experimental studies, quartz, which controls the rock strength at brittle-ductile transition zone, was generally used. On the other hand, frictional experiment with feldspar is very few in spite of dominant phase in the crust, because feldspar behaves in a brittle manner at greenshist facies. However, recent studies indicate fine-grained plagioclase (1um) contributed deformation process largely at the Hatagawa fault zone, northeast Japan, where is considered to have been brittle-ductile transition zone in the past. In order to understand the source processes of earthquakes, it is important to evaluate the physical properties of fine grained plagioclace as well as those of quartz. In this study, we conducted frictional experiments by using anorthite and quartz gouges under high pressure and high temperature in a triaxial apparatus, and compared frictional behaviors of two minerals with elevated temperature. Temperature varied from room temperature to 800°C. Fine- (1-10um,1um) and coarse-grained (50um, 100um) samples were prepared to evaluate the effect of different grain size as observed Hatagawa fault zone. The samples were put between upper and lower sawcut cylinders (20mm diameter x 40mm long). The sawcut was oriented at 30° to the loading axis. These were jacketed with thin sleeves of annealed Cu. Pore fluids accelerated deformation process of Hatagawa mylonite at higher temperature than 600°C under the same effective confining pressure (Masuda et al., presented in this meeting). Therefore, results of frictional experiments under the dry and the wet conditions were compared. In the dry conditions, experiments were conducted under the confining pressure up to 150MPa. In the wet conditions, pore water pressure was applied up to 50MPa.

Arai, T.; Masuda, K.; Fujimoto, K.; Shigematsu, N.; Ohtani, T.; Sumii, T.; Okuyama, Y.

2002-12-01

167

Surveillance of prestressed concrete pressure vessels under commissioning and operational conditions at Hunterston 'B' Power Station  

International Nuclear Information System (INIS)

Monitoring procedures were established to satisfy the Statutory requirements set by the Licensing Authority (The Nuclear Installations Inspectorate), and to demonstrate the continuing safety of the Prestressed Concrete Pressure Vessels (P.C.P.V.) under operational conditions to the Purchaser and Operator (South of Scotland Electricity Board), and the N.I.I. For the long term, 80 vibrating wire strain gauges have been selected as indicating the general behaviour of each vessel under commissioning and operational conditions. A programme of tendon check loading has been set up, allowing an estimate of the prestress obtaining in the vessel to be made. Also, strands are withdrawn for visual and metallurgical examination. Regular temperature scans are carried out using the thermocouples installed in the vessel concrete and on the liner and penetrations. The results of these and other monitoring procedures are discussed. It is concluded that the Prestressed Concrete Pressure Vessels at Hunterston 'B' Power Station are performing in a predictable and satisfactory manner. (orig.)

168

CFD simulation of pressure and discharge surge in Francis turbine at off-design conditions  

International Nuclear Information System (INIS)

A hybrid 1D-3D CFD model is developed for the numerical simulation of pressure and discharge surge in hydraulic power plants. The most essential part – the turbine itself – is simulated directly using 3D unsteady equations of turbulent motion of fluid-vapor mixture, while the rest of the hydraulic system is simulated in frames of 1D hydro-acoustic model. Thus the model accounts for the main factors responsible for excitation and propagation of pressure and discharge waves in hydraulic power plant. Boundary conditions at penstock inlet and draft tube outlet are discussed in detail. Then simulations of dynamic behavior at part load and full load operating points are performed. It is shown that the numerical model is able to capture self-excited oscillations in full load conditions. The influence of penstock length and flow structure behind the runner are investigated. The presented approach seems to be a promising tool for prediction and investigation the dynamic behavior in hydraulic power plants.

169

The Influence of Collar on Surge Pressure Caused by the Drilling Fluid Viscous Force under Pumping Condition  

Directory of Open Access Journals (Sweden)

Full Text Available The study of surge pressure is of significant importance for the safety of drilling process because field practice shows that the surge pressure caused by fluid viscous force can cause a great damage to the drilling operation. The accurate calculation of surge pressure is directly related to the safety of the drilling process. However, the existing surge pressure models rarely take the impact of the collar into consideration and thus will inevitably affect the precision of the surge pressure calculation. In this study, based on the pumping condition, a steady-state calculation model for surge pressure caused by drilling fluid viscous force is developed considering the presence of collar. In the end a case study is presented to demonstrate the importance of collar during the calculation of surge pressure.

Jun Li

2013-02-01

170

Direct ion flux measurements at high-pressure-depletion conditions for microcrystalline silicon deposition  

International Nuclear Information System (INIS)

The contribution of ions to the growth of microcrystalline silicon thin films has been investigated in the well-known high-pressure-depletion (HPD) regime by coupling thin-film analysis with plasma studies. The ion flux, measured by means of a capacitive probe, has been studied in two regimes, i.e., the amorphous-to-microcrystalline transition regime and a low-to-high power regime; the latter regime had been investigated to evaluate the impact of the plasma power on the ion flux in collisional plasmas. The ion flux was found not to change considerably under the conditions where the deposited material undergoes a transition from the amorphous to the microcrystalline silicon phase; for solar-grade material, an ion-to-Si deposition flux of ?0.30 has been determined. As an upper-estimation of the ion energy, a mean ion energy of ?19 eV has been measured under low-pressure conditions (4 to an H2 plasma resulted in an increase of the ion flux by about 30% for higher power values, whereas the electron density, deduced from optical emission spectroscopy analysis, decreased. The electron temperature, also deduced from optical emission spectroscopy analysis, reveals a slight decrease with power. Although the dominant ion in the HPD regime is SiH3+, i.e., a change from H3+ in pure hydrogen HPD conditions, the measured larger ion loss can be explained by assuming steeper electron density profiles. These results, therefore, confirm the results reported so far: the ion-to-Si deposition flux is relatively large but has neither influence on the microcrystalline silicon film properties nor on the phase transition. Possible explanations are the reported high atomic hydrogen to deposition flux ratio, mitigating the detrimental effects of an excessive ion flux

171

Assessment of the Swelling Pressure of the Green Clay of Tangier (Morocco) Compared with the Soil-Moisture Conditions  

OpenAIRE

The swelling phenomenon appears seriously when changing the soil-moisture conditions. The swelling pressure induced by the expansive soil can causes unfavourable problems or instability for the civil structures. So, understanding the soil behavior is considered a valuable work for engineers and consultants in the geotechnical and civil engineering sectors. In reality, the assessment of the swelling pressure of expansive soil depends, first of all, of test conditions related to the change of s...

El Bahlouli Tarik; Bahi Lahcen

2014-01-01

172

Sudden pore pressure rise and rapid landslide initiation induced under extreme rainfall conditions - a case study  

Science.gov (United States)

Since July 19 to 26, 2009, western Japan had a severe rainstorms and caused floods and landslides. Most of the landslides are debris slide - debris flows. Most devastated case took place in Hofu city, Japan. On July 21, extremely intense rainstorm caused numerous debris flows and mud flows in the hillslopes Some of the debris flows destroyed residential houses and home for elderly people, and finally killed 14 residents. Debris flow distribution map was prepared soon based on airphoto interpretation. Japanese Meteorological Agency runs nation-wide ground-based rain gauge network as well as radar rain gauges, which provide hourly to 10 minutes precipitation distribution real-time with spatial resolution of about 5 km. Distribution of daily (cumulative) precipitation of July 21 shows (1) The cumulative precipitation from 6 am -- 12 am of the day was evaluated that their return period could be 200 - 600 years statistically. In 2009, another extraordinary rainfall, of which intensity was evaluated as less than 100 years more more, caused floods in another city claiming many residents lives on the way to evacuation area. Those frequent extraordinary extreme rainfall is not concluded as the consequence of global warming nor climate change, however, those frequency of extreme rainfall events affecting societies are obviously increasing in Japan, too. As for the Hofu city case, it was proved that debris flows took place in the high precipitation area and covered by covered by weathered granite sands and silts which is called "masa". This sands has been proved susceptible against landslides under extreme rainfall conditions. However, the transition from slide - debris flow process is not well revealed, except authors past experiment on the similar masa samples in June 1999 Hiroshima debris flow case. Authors have embedded pore pressure control system for the undrained ring shear apparatus. Strongly weathered sandy soils were sampled just on the smooth and flat granitic sliding surface of one of the upstream small-scale landslides. Those contained finer grains and lower permeability rather than the one sampled in the Hiroshima case. Sample was consolidated by smaller stress corresponding to the site condition, and saturated by overnight circulating de-aired water. Normal stress and shear stress corresponding the slope condition was given, then, pore pressure (back pressure) was raised artificially at constant rate. When the effective stress reached the failure line, suddenly measured pore pressure monitored at about 2 mm above the shear plane, quickly increased. This sudden change abruptly accelerate the shear displacement. Stress condition soon reached the steady state and remained there thereafter. The reason of the excess pore pressure generation was the negative dilatancy, following a slight positive dilatancy. Most of the negative dilatancy could be explained by collapse of loose soil skelton as well as grain crushing during deformation and shearing.

Fukuoka, Hiroshi; Wang, Fawu; Wang, Gonghui

2010-05-01

173

Intraocular pressure vs intracranial pressure in disease conditions: A prospective cohort study (Beijing iCOP study)  

OpenAIRE

Abstract Background The correlation between intracranial pressure (ICP) and intraocular pressure (IOP) is still controversial in literature and hence whether IOP can be used as a non-invasive surrogate of ICP remains unknown. The aim of the current study was to further clarify the potential correlation between ICP and IOP. Methods The IOP measured with Goldmann applanation tonometer was carried out on 130 patients whose ICP was determined via lumber puncture. Th...

Li Zhen; Yang Yingxin; Lu Yan; Liu Dachuan; Xu Erhe; Jia Jianping; Yang Diya; Zhang Xiaojun; Yang Huiqing; Ma Daqing; Wang Ningli

2012-01-01

174

Use of a CFD-tool for assessment of the reactor pressure vessel integrity in pressure thermal shock conditions  

International Nuclear Information System (INIS)

Integrity evaluation methods for nuclear Reactor Pressure Vessels (RPVs) under Pressurised Thermal Shock (PTS) loading are applied by French Utility. They are based on the analysis of the behaviour of relatively shallow cracks under PTS loading conditions due to the emergency cooling during SBLOCA transients. This paper explains the Research and Development program started at E.D.F about the cooling phenomena of a PWR vessel after a Pressurised Thermal Shock. The numerical results are obtained with the EDF Thermal Hydraulic code (CodeSaturne) coupled with the thermal-solid code SYRTHES to take into account the conjugate heat transfer on the cooling of the vessel. We first explain the numerical program concerning the qualification task of this CFD-Tool for Safety Injection studies. We have investigated several configurations. Two experiment test cases have been studied and we present a comparison between experimental and numerical results in terms of temperature field in cold leg but also in a down comer. Then, for the Thermal-Hydraulic reactor study, the geometries used represent a three and a four loop PWR. In these calculations, the simulated mesh takes into account as much as possible of the exact geometry of the lower plenum. Numerical results are given in terms of temperature field in the cold legs and in the down comer, as well as in the solid part formed by cladding and base metal. On the whole, the main purpose of the numerical thermalhydraulic studose of the numerical thermalhydraulic studies is to accurately estimate the distribution of fluid temperature in the down comer and the heat transfer coefficients on the inner RPV surface for a fracture mechanics computation which will subsequently assess the associated RPV safety margins. Lastly, a parametric study has been carried out in order to assess the relative importance or influence of some physical data. Two cases are suited. The first part of this paper reports the effects of the thermal coupling between the RPV and the fluid flow. To this end, two computations have been realised the first one taking account of the thermal coupling, the other one neglecting the thermal feedback of the wall to the fluid during the transient. In the second study, the safety injection temperature is increased from the usual value of 9 degree C in the previous calculations up to 35 degree C. (authors)

175

Comparison of three mineral candidates in middle and low-pressure condition. Experimental study  

Energy Technology Data Exchange (ETDEWEB)

''Greenhouse Effect'', which is scientifically proven to be main caused by the increasing concentration of CO{sub 2}, has become a topic of national and international concern. Mineral carbonation, such as carbonation of alkaline silicate Ca/Mg minerals, analogous to natural weathering processes, is a potentially attractive route to mitigate possible global warming on the basis of industrial imitation of natural weathering processes. In this paper, three typical natural mineral candidates in China, serpentine, olivine and wollastonite, were selected as carbonation raw materials for direct mineral carbonation experiments under middle and low-pressure. A series number of experiments were carried out to investigate the factors that influence the conversion of carbonation reaction, such as reaction temperature, reaction pressure, particle size, solution composition and pretreatment. The solid products from carbonation experiments were filtered, collected, dried and analyzed by X-ray diffraction (XRD) and field scanning electron microscopy equipped with energy dispersive X-ray analysis (FSEM-EDX) to identify the reaction of mineral carbonation. And the method of mass equilibrium after heat decomposition was used to calculate the mineral carbonation conversion. All the XRD and FSEM analysis validate that carbonation reaction was occurred during the experiments and mineral carbonation is one of the potential techniques for carbon dioxide sequestration. The data of mass equilibrium after heat decomposition was collected and then the conversion formula was used to calculate the carbonation conversion of all the three mineral candidates. The mass equilibrium results show that, for all of the three mineral materials, the carbonation conversion increases with the increasing of reaction temperature. But once the temperature increases above 150 C, the conversion of serpentine decreases a little. Reaction pressure is also an important factor to mineral carbonation process. For all of the three mineral materials, the carbonation conversion increases with the increasing of reaction pressure. Decrease of mineral particle sizes and use of heat treatment before carbonation experiments can effectively improve the carbonation conversion of mineral carbonation. And the addition of NaHCO{sub 3}, which had a buffering effect that kept the solution pH in a certain range, can also improve the carbonation conversion. In this paper, a highest carbonation conversion of 89.5% was obtained under the condition of T = 150 C, P{sub CO{sub 2}} = 4.0 MPa, particle sizes <37 {mu}m in 1 h using wollastonite as the raw material. Compared with serpentine and olivine, wollastonite is the most promising material for carbon dioxide mineral carbonation under middle and low-pressure.

Yan, Heng; Zhang, Jun-ying; Zhao, Yong-chun; Wang, Zhi-lang; Pan, Xia; Xu, Jun; Zheng, Chu-guang [Huazhong Univ. of Science and Technology, Wuhan (China). State Key Lab. of Coal Combustion

2013-07-01

176

QUAVER - A programme to evaluate monopole and dipole boundary conditions in pressure tube reactor lattices  

International Nuclear Information System (INIS)

In order to apply source-sink theory to pressure tube reactor lattices it is necessary to calculate boundary conditions at the fuel channel/moderator interfaces to be satisfied by the neutron flux. A method is described for evaluating the necessary coefficients using multi-group diffusion theory in a cylindricalised lattice cell for both monopole and dipole components of flux. Provision is made for in or out leakage of neutrons in each group at the cell boundary so that allowance can be made for effects of cell environment on the channel boundary conditions. The programme QUAVER (written in EGTRAN) is described for use on the English Electric KDF9 Computer. QUAVER outputs the boundary condition matrices on cards for use in source-sink core calculations, and includes a facility for the condensation of the primary group output to a secondary group structure. The numerical method and the data input specification are described together with full details of a sample calculation. (author)

177

High-pressure refrigeration system with CO2 in automobile air-conditioning  

Energy Technology Data Exchange (ETDEWEB)

Due to high consumer acceptance of automobile air conditioning systems, the discussion of the effects of refrigerants on global warming is becoming more important to an environmentally-aware public. The consumption of fossil fuels to operate air conditioning systems, combined with refrigerant emissions, contribute to the greenhouse effect. Substitution of conventional refrigerants with CO2 reduces the load on heat-adsorbing gases in our atmosphere by providing an environment-friendly alternative. Because the amount of engine power devoted to air conditioning systems is limited, carbon dioxide makes an attractive substitute for HFC refrigerants in vehicle applications. In this paper, TEWI-figures for a vehicle with A/C System are considered, and the reduction potential due to CO2 as refrigerant as a motive for phasing out current technology is shown. This includes a comparison of COP`s between a conventional cold vapor cycle and the transcritical refrigerant cycle using CO2 to evaluate benefits and disadvantages. The high pressure refrigerant cycle has to be seen in the light of the requirement profile for introduced MACS. Furthermore, assorted results from the European RACE (Refrigeration and Automotive Climate systems under Environmental aspects) project are presented. The theory of the refrigerant cycle, tests results, packaging in a vehicle, and first experiences of component development are discussed, as well as difficulties in adapting this `Green Technology` to a car. 7 refs.

Wertenbach, J.; Kauf, F. [Daimler-Benz, Stuttgart (Germany)

1998-12-31

178

High-pressure phase transitions in BiFeO3: hydrostatic vs. non-hydrostatic conditions  

OpenAIRE

We report high-pressure x-ray diffraction experiments on BiFeO3 (BFO) single crystals in diamond-anvil cells up to 14 GPa. Two data sets are compared, one in hydrostatic conditions, with helium used as pressure-transmitting medium, and the other in non-hydrostatic conditions, with silicon oil as pressure-transmitting medium. It is shown that the crystal undergoes different phase transitions in the two cases, highlighting the high sensitivity of BFO to non-hydrostatic stress....

Guennou, Mael; Bouvier, Pierre; Haumont, Raphae?l; Garbarino, Gaston; Kreisel, Jens

2011-01-01

179

Ultrasound propagation in air-filled cylindrical pores under pressurized conditions  

Science.gov (United States)

Ion-track membranes (ITM) are known as polymer films with straight pore channels the size, shape, orientation and density of which can be precisely controlled. Previous ultrasonic studies of ITM using air-coupled and wide-band ultrasound pulses (0.1-5.0 MHz) revealed the possibility to isolate and study ultrasound propagation in these pores. Hence a novel ultrasonic technique has been established to determine pore characteristics of ITM using this pore propagation mode. In this work, we present a modification of the technique based on the use of pressurized air. This is achieved by enclosing transducers and samples in a pressurized chamber (1-9 bar). The main objective of this study is to reduce the attenuation of the ultrasound waves propagating in the pores and to increase the coupling of the ultrasonic energy into this pore propagation mode at the membrane surface in order to extend the applicability range of the existing technique to the characterization of ITM with small pores (diameter air-coupled ultrasound at room conditions may present some drawbacks.

Gómez Álvarez-Arenas, T. E.; Acosta, V.; Apel, P. Yu.; Orelovitch, O. L.

2012-05-01

180

Experimental examination of heat removal limitation of screw cooling tube at high pressure and temperature conditions  

International Nuclear Information System (INIS)

For development of high heat flux components for fusion machines, JAERI has developed high performance cooling tubes using pressurized water flow. A cooling tube with triangular fins on its inner surface has been tested. Because the fins can be machined by a simple mechanical threading, this tube is called a screw tube. The present study is intended to investigate heat transfer characteristics of the screw tube with M10 thread of 1.5-mm-pitch, which has the highest critical heat flux (CHF) in the previous experimental campaign compared with the tubes with various threads of different pitches. In addition, another CHF tests have been performed to examine the reduction of the heat removal performance of the screw tube caused with the increase of cooling water temperature up to 100 deg. C at the local pressure of 2 and 4 MPa. The results of CHF experiments are compared with an existing correlation for a smooth tube to evaluate its heat removal limitation at higher temperature condition compared with the previous ones

181

Investigation of LPP combustors under elevated pressure conditions; Untersuchungen zu LPP-Flugtriebwerksbrennkammern unter erhoehtem Druck  

Energy Technology Data Exchange (ETDEWEB)

The development of new combustor concepts for aero engines to meet future emissions regulations in based on a detailed knowledge of the combustion process and the velocity field. In the presented thesis, non intrusive measurements were performed in a model combustion chamber under almost realistic pressure and temperature conditions. The species OH, NO, unburned hydrocarbons and fuel droplets were detected in 2 dimensions with the Laser Induced Fluorescence (LIF). The velocity field was measured with the Particle Image Velocimetry technique (PIV). [German] Die Weiterentwicklung neuer Brennkammerkonzepte zur Erfuellung zukuenftiger Schadstoffemissionsrichtlinien erfordert genaue Kenntnisse der ablaufenden Verbrennungs- und Stroemungsvorgaenge in der Brennkammer. Bei den in der Arbeit vorgestellten Untersuchungen wurden in einer LPP-Modellbrennkammer unter annaehernd realistischen Eintrittsbedingungen die Spezies OH, NO, unverbrannte Kohlenwasserstoffe sowie noch fluessiger Brennstoff zweidimensional anhand der Laserinduzierten Fluoreszenz (LIF) nachgewiesen. Das Stroemungsfeld wurde mit Hilfe der Particle Image Velocimetry (PIV) gemessen.

Fink, R.

2001-05-01

182

High Pressure Compression-Molding of ?-Cellulose and Effects of Operating Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Commercial ?-cellulose was compression-molded to produce 1A dog-bone specimens under various operating conditions without any additive. The resulting agromaterials exhibited a smooth, plastic-like surface, and constituted a suitable target as replacement for plastic materials. Tensile and three-points bending tests were conducted according to ISO standards related to the evaluation of plastic materials. The specimens had strengths comparable to classical petroleum-based thermoplastics. They also exhibited high moduli, which is characteristic of brittle materials. A higher temperature and higher pressure rate produced specimens with higher mechanical properties while low moisture content produced weaker specimens. Generally, the strong specimen had higher specific gravity and lower moisture content. However, some parameters did not follow the general trend e.g., thinner specimen showed much higher Young’s Modulus, although their specific gravity and moisture content remained similar to control, revealing a marked skin-effect which was confirmed by SEM observations.

Antoine Rouilly

2013-05-01

183

Characterization of transient discharges under atmospheric pressure conditions applying nitrogen photoemission and current measurements  

CERN Document Server

Plasma parameters of three transient discharges (filamentary and homogeneous dielectric barrier discharges in air, and the spark discharge of an argon plasma coagulator) operated at atmospheric pressure conditions are determined applying a combination of diagnostics methods, namely numerical simulation, current measurement, and optical emission spectroscopy. These diagnostic methods supplement each other and resolve problems, which arise when these methods are used separately. Nitrogen is used as sensor gas and is admixed to argon for studying the argon plasma coagulator. The Boltzmann equation is solved in 'local' approximation to determine electron velocity distribution function. Drift velocity, electron-impact excitation rate constants for nitrogen molecular emission, electric current density, and emission spectrum of nitrogen molecule are calculated. Plasma parameters (electron velocity distribution function and electron density) are determined applying calculated as far as measured electric current, and ...

Keller, Sandra; Bibinov, Nikita; Awakowicz, Peter

2011-01-01

184

Evaluation of pressure boundary conditions for permeability calculations using the lattice-Boltzmann method  

CERN Document Server

Lattice-Boltzmann (LB) simulations are a common tool to numerically estimate the permeability of porous media. For valuable results, the porous structure has to be well resolved resulting in a large computational effort as well as high memory demands. In order to estimate the permeability of realistic samples, it is of importance to not only implement very efficient codes, but also to choose the most appropriate simulation setup to achieve accurate results. With the focus on accuracy and computational effort, we present a comparison between different methods to apply an effective pressure gradient, efficient boundary conditions, as well as two LB implementations based on pore-matrix and pore-list data structures.

Narváez, Ariel

2010-01-01

185

Assessment of the Swelling Pressure of the Green Clay of Tangier (Morocco Compared with the Soil-Moisture Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available The swelling phenomenon appears seriously when changing the soil-moisture conditions. The swelling pressure induced by the expansive soil can causes unfavourable problems or instability for the civil structures. So, understanding the soil behavior is considered a valuable work for engineers and consultants in the geotechnical and civil engineering sectors. In reality, the assessment of the swelling pressure of expansive soil depends, first of all, of test conditions related to the change of soil-moisture, as it happens, the influence of the combination “loading-start wetting” and also the unloading process after saturation. To this end, we establish an experimental study on the green clay of Tangier to evaluate the swelling pressure by using oedometer apparatus. Secondly, attention is bore to the combination “initial water content-dry density”, another factor related to the change of the soil-moisture, to show the influence of initial state condition on the swelling pressure.

El Bahlouli Tarik

2014-04-01

186

A study on the pressure distribution in the centrifugal compressor channel diffuser at design and off-design conditions  

International Nuclear Information System (INIS)

The aim of this paper is to understand the time averaged pressure distributions in a high-speed centrifugal compressor channel diffuser at design and off-design flow rates. Pressure distributions from the impeller exit to the channel diffuser exit are measured and discussed for various flow rates from choke to near surge condition, and the effect of operating condition is discussed. The strong non-uniformity in the pressure distribution is obtained over the vaneless space and semi-vaneless space caused by the impeller-diffuser interaction. As the flow rate increases, flow separation near the throat, due to large incidence angle at the vane leading edge, increases aerodynamic blockage and reduces the aerodynamic flow area downstream. Thus the minimum pressure location occurs downstream of the geometric throat, and it is named as the aerodynamic throat. And at choke condition, normal shock occurs downstream of this aerodynamic throat. The variation in the location of the aerodynamic throat is discussed

187

Theoretical and numerical investigations of TAP experiments. New approaches for variable pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

Temporal analysis of products (TAP) is a valuable tool for characterization of porous catalytic structures. Established TAP-modeling requires a spatially constant diffusion coefficient and neglect convective flows, which is only valid in Knudsen diffusion regime. Therefore in experiments, the number of molecules per pulse must be chosen accordingly. New approaches for variable process conditions are highly required. Thus, a new theoretical model is developed for estimating the number of molecules per pulse to meet these requirements under any conditions and at any time. The void volume is calculated as the biggest sphere fitting between three pellets. The total number of pulsed molecules is assumed to fill the first void volume at the inlet immediately. Molecule numbers from these calculations can be understood as maximum possible molecules at any time in the reactor to be in Knudsen diffusion regime, i.e., above the Knudsen number of 2. Moreover, a new methodology for generating a full three-dimensional geometrical representation of beds is presented and used for numerical simulations to investigate spatial effects. Based on a freely available open-source game physics engine library (BULLET), beds of arbitrary-sized pellets can be generated and transformed to CFD-usable geometry. In CFD-software (ANSYS CFX registered) a transient diffusive transport equation with time-dependent inlet boundary conditions is solved. Three different pellet diameters were investigated with 1e18 molecules per pulse, which is higher than the limit from the theoretical calculation. Spatial and temporal distributions of transported species show regions inside the reactor, where non-Knudsen conditions exist. From this results, the distance from inlet can be calculated where the theoretical pressure limit (Knudsen number equals 2) is obtained, i.e., from this point to the end of the reactor Knudsen regime can be assumed. Due to linear dependency of pressure and concentration (assuming ideal gas thermodynamics), the results from one numerical simulation can be converted to any number of molecules per pulse. With this procedure, the distance from inlet from which on Knudsen regime can be assumed for different molecules per pulse can be calculated easily. The new model will be applied to enhance the description of industrially relevant conversions, as for instance alkane conversions on transition metal oxides. (orig.)

Senechal, U.; Breitkopf, C. [Technische Univ. Dresden (Germany). Inst. fuer Energietechnik

2011-07-01

188

Effect of Nb additions on the microstructure, thermal stability and mechanical behavior of high pressure Zr phases under ambient conditions  

International Nuclear Information System (INIS)

Research highlights: ? We analyze the influence of Nb additions on the shear-induced ? ? ? ? ? phase transformations in pure Zr by high pressure torsion (HPT). ? Nb reduces the transition pressures and increases the transformation kinetics. ? High pressure phases are retained under ambient conditions due to the presence of an internal stress. ? Post-HPT annealing allows to fabricate bimodal/biphase nanostructures with enhanced mechanical behavior. - Abstract: This paper analyzes the influence of Nb on the shear-induced ? ? ? ? ? transformation taking place when processing Zr by high pressure torsion (HPT) under suitable conditions of pressure and shear. With that purpose, pure Zr and Zr-2.5%Nb were processed by HPT at room temperature and at pressures ranging from 0.25 to 6 GPa using 5 anvil turns. Nb causes a further reduction of the transition pressures, which are already lower when applying shear besides pressure. Thus, the transition pressure to the ? phase is reduced at least 100 times in the Zr-Nb alloy. Alloying with Nb decreases the grain size of the transformed phases, significantly enhances their thermal stability and increases their UTS and elongation to failure. Selected post-HPT annealing treatments lead to the development of very tough, multiphase Zr and Zr-Nb with bimodal grain size distributions. The retention of the high pressure phases under ambient conditions is explained by the development of a high internal stress during prol stress during processing. This stress is measured by synchrotron radiation diffraction at HZB-BESSY II. It is proposed that the presence of Nb reduces the internal stress level required for the retention of the high pressure phases.

189

Effectiveness of Sealed Double-Ring Infiltrometers trademark and effects of changes in atmospheric pressure on hydraulic conductivity  

International Nuclear Information System (INIS)

The Savannah River Site is currently evaluating some 40 hazardous and radioactive-waste sites for remediation. Among the remedial alternatives considered is closure using a kaolin clay cap. The hydraulic conductivity suggested by the US Environmental Protection Agency is 1.0 x 10-7 cm/sec. One instrument to measure this value is the Sealed Double-Ring Infiltrometer trademark (SDRI). Six SDRI were recently installed on a kaolin test cap. Test results demonstrated uniform performance of these instruments. However, the test data showed as much as an order of magnitude of variation over time. This variation is attributed to both internal structural heterogeneity and variable external boundary conditions. The internal heterogeneity is caused by construction variability within a specified range of moisture and density. The external influences considered are temperature and barometric pressure. Temperature was discharged as a source of heterogeneity because of a lack of correlation with test data and a negligible impact from the range of variability. However, a direct correlation was found between changes in barometric pressure and hydraulic conductivity. This correlation is most pronounced when pressure changes occur over a short period of time. Additionally, this correlation is related to a single soil layer. When the wetting front passes into a more porous foundation layer, the correlation with pressure changes disappears. Conclusions are that the SDRI performsrs. Conclusions are that the SDRI performs adequately, with good repeatability of results. The duration of test is critical to assure a statistically valid data set. Data spikes resulting from pressure changes should be identified, and professional judgment used to determine the representative hydraulic conductivity. Further evaluation is recommended to determine the impact of pressure change on the actual hydraulic conductivity

190

Sufficient conditions for globally asymptotic self-stability of pressurized water reactors  

International Nuclear Information System (INIS)

Highlights: • Self-stability analysis of the PWR is presented through the shifted-ectropy based approach. • Sufficient conditions for the globally asymptotic self-stability are established. • The correctness of the theoretic results are finally verified through numerical simulation. - Abstract: After the Fukushima accident, safe, stable and efficient operation of reactors is very necessary for the development of nuclear power industry. Since pressurized water reactor (PWR) is the mostly widely used fission reactor, the improvement of its operation performance is quite meaningful. Self-stability is the most important dynamic feature of any reactors, and analyzing the self-stability can give the approach of improving the operation performance. With this in mind, the self-stability analysis of the PWR is presented through the shifted-ectropy based approach, and sufficient conditions for the globally asymptotic self-stability in cases of negative, zero and positive coolant temperature feedback coefficient are all established. The correctness of the theoretical results are finally verified through numerical simulation. The results of this paper give the way to not only guaranteeing self-stability through physical and thermal-hydraulic reactor design but also strengthening closed-loop stability and robustness by the means of feedback control

191

Appropriate welding conditions of temper bead weld repair for SQV2A pressure vessel steel  

Energy Technology Data Exchange (ETDEWEB)

Temper bead welding technique is one of the most important repair welding methods for large structures for which it is difficult to perform the specified post weld heat treatment. In this study, appropriate temper bead welding conditions to improve the characteristics of heat affected zone (HAZ) are studied using pressure vessel steel SQV2A corresponding to ASTM A533 Type B Class 1. Thermal/mechanical simulator is employed to give specimens welding thermal cycles from single to quadruple cycle. Charpy absorbed energy and hardness of simulated CGHAZ by first cycle were degraded as compared with base metal. Improvability of these degradations by subsequent cycles is discussed and appropriate temper bead thermal cycles are clarified. When the peak temperature lower than Ac1 and near Ac1 in the second thermal cycle is applied to CGAHZ by first thermal cycle, the characteristics of CGHAZ improve enough. When the other peak temperatures (that is, higher than Ac1) in the second thermal cycle are applied to the CGHAZ, third or more thermal cycle temper bead process should be applied to improve the properties. Appropriate weld condition ranges are selected based on the above results. The validity of the selected ranges is verified by the temper bead welding test. (orig.)

Mizuno, R.; Matsuda, F. [NDE Center, Japan Power Engineering and Inspection Corp. (Japan); Brziak, P. [Welding Research Inst. - Industrial Inst. of Slovak Republic (Slovakia); Lomozik, M. [Inst. of Welding (Poland)

2004-07-01

192

Appropriate welding conditions of temper bead weld repair for SQV2A pressure vessel steel  

International Nuclear Information System (INIS)

Temper bead welding technique is one of the most important repair welding methods for large structures for which it is difficult to perform the specified post weld heat treatment. In this study, appropriate temper bead welding conditions to improve the characteristics of heat affected zone (HAZ) are studied using pressure vessel steel SQV2A corresponding to ASTM A533 Type B Class 1. Thermal/mechanical simulator is employed to give specimens welding thermal cycles from single to quadruple cycle. Charpy absorbed energy and hardness of simulated CGHAZ by first cycle were degraded as compared with base metal. Improvability of these degradations by subsequent cycles is discussed and appropriate temper bead thermal cycles are clarified. When the peak temperature lower than Ac1 and near Ac1 in the second thermal cycle is applied to CGAHZ by first thermal cycle, the characteristics of CGHAZ improve enough. When the other peak temperatures (that is, higher than Ac1) in the second thermal cycle are applied to the CGHAZ, third or more thermal cycle temper bead process should be applied to improve the properties. Appropriate weld condition ranges are selected based on the above results. The validity of the selected ranges is verified by the temper bead welding test. (orig.)

193

Theoretical and numerical investigations of TAP experiments: new approaches for variable pressure conditions  

Science.gov (United States)

Temporal analysis of products ("TAP", see Gleaves et al. in Catal Rev Sci Eng 30:49, 1988) is a valuable tool for characterisation of porous catalytic structures. Established TAP-modelling requires a spatially constant diffusion coefficient and neglect convective flows, which is only valid in Knudsen diffusion regime. A new theoretical model is developed for estimating the number of molecules per pulse to stay in Knudsen diffusion regime under any conditions and at any time. Moreover a new methodology for generating a full three-dimensional geometrical representation of beds is presented and used for numerical simulations. In computational fluid dynamics software (ANSYS CFX® version 14) a transient diffusive transport equation with time-dependent inlet boundary conditions is solved. Three different pellet diameters were investigated with 1E+18 molecules per pulse, which is higher than the limit from the theoretical calculation (about 1E+15). From this results, the distance from inlet can be calculated where the theoretical pressure limit ( Kn = 2) is obtained, i.e., from this point to the end of reactor, Knudsen regime can be assumed.

Breitkopf, Cornelia; Sénéchal, Ulf

2014-03-01

194

Crack tip conditions related to environmentally assisted cracking in pressure vessel steels: Effect of temperature  

International Nuclear Information System (INIS)

The effect of temperature on the anodic dissolution and film repair on pressure vessel steel in deaerated environments was measured by using CERT under controlled potential. The effect of dissolved sulfide was taken into account in this study. The results show that temperature has little effect on the kinetics of anodic processes between 80 and 290 degrees C except that the amount of sulfide required to trigger high dissolution rates decreases when the temperature decreases. In the range 200-290 degrees C, these results are consistent with the current model which assumes that corrosion fatigue crack growth rates on low alloy steel in PWR water are controlled by the film repair kinetics at the crack tip. The agreement is questionable at lower temperatures. The CERT under controlled potential also suggested that plastic deformation cannot account for the effect of sulfur on the anodic processes at crack tip in EAC conditions. Thus, besides anodic dissolution, mechanical decohesion is assumed to contribute to crack advance in EAC conditions

195

Direct ion flux measurements at high-pressure-depletion conditions for microcrystalline silicon deposition  

Energy Technology Data Exchange (ETDEWEB)

The contribution of ions to the growth of microcrystalline silicon thin films has been investigated in the well-known high-pressure-depletion (HPD) regime by coupling thin-film analysis with plasma studies. The ion flux, measured by means of a capacitive probe, has been studied in two regimes, i.e., the amorphous-to-microcrystalline transition regime and a low-to-high power regime; the latter regime had been investigated to evaluate the impact of the plasma power on the ion flux in collisional plasmas. The ion flux was found not to change considerably under the conditions where the deposited material undergoes a transition from the amorphous to the microcrystalline silicon phase; for solar-grade material, an ion-to-Si deposition flux of ?0.30 has been determined. As an upper-estimation of the ion energy, a mean ion energy of ?19 eV has been measured under low-pressure conditions (<1 mbar) by means of a retarding field energy analyzer. Combining this upper-estimate with an ion per deposited Si atom ratio of ?0.30, it is concluded that less than 6 eV is available per deposited Si atom. The addition of a small amount of SiH{sub 4} to an H{sub 2} plasma resulted in an increase of the ion flux by about 30% for higher power values, whereas the electron density, deduced from optical emission spectroscopy analysis, decreased. The electron temperature, also deduced from optical emission spectroscopy analysis, reveals a slight decrease with power. Although the dominant ion in the HPD regime is SiH{sub 3}{sup +}, i.e., a change from H{sub 3}{sup +} in pure hydrogen HPD conditions, the measured larger ion loss can be explained by assuming steeper electron density profiles. These results, therefore, confirm the results reported so far: the ion-to-Si deposition flux is relatively large but has neither influence on the microcrystalline silicon film properties nor on the phase transition. Possible explanations are the reported high atomic hydrogen to deposition flux ratio, mitigating the detrimental effects of an excessive ion flux.

Bronneberg, A. C.; Kang, X.; Palmans, J.; Janssen, P. H. J.; Lorne, T. [Applied Physics Department, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Creatore, M. [Applied Physics Department, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Solliance Solar Research, High Tech Campus 5, 5656AE Eindhoven (Netherlands); Sanden, M. C. M. van de [Applied Physics Department, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven (Netherlands); Dutch Institute for Fundamental Energy Research (DIFFER), P.O. Box 1207, 3430BE Nieuwegein (Netherlands)

2013-08-14

196

Direct ion flux measurements at high-pressure-depletion conditions for microcrystalline silicon deposition  

Science.gov (United States)

The contribution of ions to the growth of microcrystalline silicon thin films has been investigated in the well-known high-pressure-depletion (HPD) regime by coupling thin-film analysis with plasma studies. The ion flux, measured by means of a capacitive probe, has been studied in two regimes, i.e., the amorphous-to-microcrystalline transition regime and a low-to-high power regime; the latter regime had been investigated to evaluate the impact of the plasma power on the ion flux in collisional plasmas. The ion flux was found not to change considerably under the conditions where the deposited material undergoes a transition from the amorphous to the microcrystalline silicon phase; for solar-grade material, an ion-to-Si deposition flux of ˜0.30 has been determined. As an upper-estimation of the ion energy, a mean ion energy of ˜19 eV has been measured under low-pressure conditions (retarding field energy analyzer. Combining this upper-estimate with an ion per deposited Si atom ratio of ˜0.30, it is concluded that less than 6 eV is available per deposited Si atom. The addition of a small amount of SiH4 to an H2 plasma resulted in an increase of the ion flux by about 30% for higher power values, whereas the electron density, deduced from optical emission spectroscopy analysis, decreased. The electron temperature, also deduced from optical emission spectroscopy analysis, reveals a slight decrease with power. Although the dominant ion in the HPD regime is SiH3+, i.e., a change from H3+ in pure hydrogen HPD conditions, the measured larger ion loss can be explained by assuming steeper electron density profiles. These results, therefore, confirm the results reported so far: the ion-to-Si deposition flux is relatively large but has neither influence on the microcrystalline silicon film properties nor on the phase transition. Possible explanations are the reported high atomic hydrogen to deposition flux ratio, mitigating the detrimental effects of an excessive ion flux.

Bronneberg, A. C.; Kang, X.; Palmans, J.; Janssen, P. H. J.; Lorne, T.; Creatore, M.; van de Sanden, M. C. M.

2013-08-01

197

The kinetics of dolomite reaction rim growth under isostatic and non-isostatic pressure conditions  

Science.gov (United States)

During burial and exhumation, rocks are simultaneously exposed to metamorphic reactions and tectonic stresses. Therefore, the reaction rate of newly formed minerals may depend on chemical and mechanical driving forces. Here, we investigate the reaction kinetics of dolomite (CaMg[CO3]2) rim growth by solid-state reactions experiments on oriented calcite (CaCO3) and magnesite (MgCO3) single crystals under isostatic and non-isostatic pressure conditions. Cylindrical samples of 3-5 mm length and 7 mm diameter were drilled and polished perpendicular to the rhombohedral cleavage planes of natural clear crystals. The tests were performed using a Paterson-type deformation apparatus at P = 400 MPa confining pressure, temperatures, T, between 750 and 850°C, and reaction durations, t, of 2 - 146 h to calculate the kinetic parameters of dolomite rim growth under isostatic stress conditions. For non-isostatic reaction experiments we applied in addition differential stresses, ?, up to 40 MPa perpendicular to the contact interface at T = 750°C for 4 - 171 h duration, initiating minor inelastic deformation of calcite. The thickness of the resulting dolomite reaction rims increases linearly with the square root of time, indicating a diffusion-controlled reaction. The rims consist of two different textural domains. Granular dolomite grains (? 2 -5 ?m grain size) form next to calcite and elongated palisade-shaped grains (1-6 ?m diameter) grow perpendicular to the magnesite interface. Texture measurements with the electron backscatter diffraction technique indicate that the orientations of dolomite grains are mainly influenced by the orientation of the calcite educt crystal, in particular in the granular rim. To some extent, the texture of dolomite palisades is also influenced by the orientation of magnesite. The thickness of the two individual layers increases with temperature. At 400 MPa isostatic pressure, T = 750°C and t = 29 hours, a 5 ?m thick granular dolomite layer and a 7 ?m thick palisade-shaped layer evolve. At similar conditions and a differential stress of 30 MPa, the rim thickness remains similar; consequently the effect of non-isostatic stress on dolomite rim growth is negligible. Platinum markers show that the initial calcite-magnesite interface is located between granular and palisade-forming dolomite, indicating that rim growth occurs by counter diffusion of MgO and CaO. Diffusion of MgO across the dolomite reaction rim into calcite forms additionally magnesio-calcite grains with diameters of ? 13 - 46 ?m, depending on the experimental conditions and increasing with increasing distance to the dolomite boundary. At T = 750°C, t = 29 hours, the thickness of the magnesio-calcite layer is 32 ?m (isostatic) - 35 ?m (? = 30 MPa). The experiments indicate that solid-state reaction rim growth of dolomite between calcite and magnesite is primarily controlled by diffusion of MgO and CaO, forming layers with different microstructures during growth into the educt phases. The kinetics of the reaction in the carbonate system are not significantly changed by differential stresses up to 40 MPa. We suggest that volume diffusion is the dominant transport mechanism, which is presumably less affected by non-isostatic stresses than grain boundary diffusion.

Helpa, V.; Rybacki, E.; Morales, L. G.; Abart, R.; Dresen, G. H.

2013-12-01

198

Stress corrosion cracking of ferritic reactor pressure vessel steels under boiling water reactor conditions  

International Nuclear Information System (INIS)

The stress corrosion cracking (SCC) behaviour of low-alloy reactor pressure vessel (RPV) steels in oxygenated high-temperature water and its relevance to boiling water reactor (BWR) power operation, in particular its possible effect on both, RPV structural integrity and safety, has been a subject of controversial discussions for many years. The SCC crack growth behaviour of different RPV steels under simulated BWR/NWC conditions was therefore characterized by constant load and ripple load tests with pre-cracked fracture mechanics specimens in oxygenated high-temperature water at temperatures of either 288, 250, 200 or 150 C. Modern high-temperature water loops, online crack growth monitoring (DCPD) and fractographical analysis by scanning electron microscopy were used to quantify the cracking response. It is concluded that there is no susceptibility to sustained SCC crack growth at temperatures around 288 C under purely static loading, as long as small-scale-yielding conditions prevail at the crack tip and the water chemistry is maintained within current BWR/NWC operational practice (EPRI water chemistry guidelines). However, sustained, fast SCC (with respect to operational time scales) cannot be excluded for faulted water chemistry conditions (EPRI Action Level 3) and/or for highly stressed specimens, either loaded near to KIJ or with a high degree of plasticity in the remaining ligament. The conservative character of the 'BWR VIP 60 Disposition Lines 1 and 2' for SCC crack growth in low-alloy steels has been confirmed by this study for 288 C and RPV base material. Preliminary results indicate, that these disposition lines may be significantly or slightly exceeded (even in steels with low sulphur content) in the case of small load fluctuations at high load ratios (ripple loading) or at intermediate temperatures (200 - 250 C) in RPV materials, which show a distinct susceptibility to Dynamic Strain Ageing (DSA). (orig.)

199

New materials for temperature and pressure sensitive fluorescent paints  

OpenAIRE

This thesis describes the preparation and evaluation of new materials for imaging of barometric pressure and temperature using so-called luminescent paints. The historical background and the motivation for the research conducted are given in Chapter 1. Chapter 2 summarizes the basic principles of photoluminescence involved in imaging of partial oxygen pressure and temperature, the fundamentals of the design of pressure and temperature sensitive paints. It also summarizes the effects of lumine...

Fischer, Lorenz

2012-01-01

200

Porcine Liver Decellularization Under Oscillating Pressure Conditions: A Technical Refinement to Improve the Homogeneity of the Decellularization Process.  

Science.gov (United States)

Decellularization and recellularization of parenchymal organs may facilitate the generation of autologous functional liver organoids by repopulation of decellularized porcine liver matrices with induced liver cells. We present an accelerated (7?h overall perfusion time) and effective protocol for human-scale liver decellularization by pressure-controlled perfusion with 1% Triton X-100 and 1% sodium dodecyl sulfate via the hepatic artery (120?mmHg) and portal vein (60?mmHg). In addition, we analyzed the effect of oscillating pressure conditions on pig liver decellularization (n=19). The proprietary perfusion device used to generate these pressure conditions mimics intra-abdominal conditions during respiration to optimize microperfusion within livers and thus optimize the homogeneity of the decellularization process. The efficiency of perfusion decellularization was analyzed by macroscopic observation, histological staining (hematoxylin and eosin [H&E], Sirius red, and alcian blue), immunohistochemical staining (collagen IV, laminin, and fibronectin), and biochemical assessment (DNA, collagen, and glycosaminoglycans) of decellularized liver matrices. The integrity of the extracellular matrix (ECM) postdecellularization was visualized by corrosion casting and three-dimensional computed tomography scanning. We found that livers perfused under oscillating pressure conditions (P(+)) showed a more homogenous course of decellularization and contained less DNA compared with livers perfused without oscillating pressure conditions (P(-)). Microscopically, livers from the (P(-)) group showed remnant cell clusters, while no cells were found in livers from the (P(+)) group. The grade of disruption of the ECM was higher in livers from the (P(-)) group, although the perfusion rates and pressure did not significantly differ. Immunohistochemical staining revealed that important matrix components were still present after decellularization. Corrosion casting showed an intact vascular (portal vein and hepatic artery) and biliary framework. In summary, the presented protocol for pig liver decellularization is quick (7?h) and effective. The application of oscillating pressure conditions improves the homogeneity of perfusion and thus the outcome of the decellularization process. PMID:25164028

Struecker, Benjamin; Hillebrandt, Karl Herbert; Voitl, Robert; Butter, Antje; Schmuck, Rosa B; Reutzel-Selke, Anja; Geisel, Dominik; Joehrens, Korinna; Pickerodt, Philipp A; Raschzok, Nathanael; Puhl, Gero; Neuhaus, Peter; Pratschke, Johann; Sauer, Igor M

2014-10-16

201

Bottom nozzle failure mechanism of water reactor pressure vessel under severe accident conditions  

International Nuclear Information System (INIS)

Most of past studies devoted to the creep rupture of a nuclear reactor pressure vessel (RPV) lower head under severe accident conditions, have focused on global deformation and rupture modes. Limited efforts were made on local failure modes associated with penetration nozzles as a part of TMI-2 vessel investigation project (TMI-2 VIP) in 1990s. However, it was based on an excessively simplified shear deformation model. In the present study, the mode of nozzle failure has been investigated using data and nozzle materials from Sandia National Laboratory's lower head failure experiment (SNL-LHF). Crack-like separations were revealed at the nozzle weld metal to RPV interfaces indicating the importance of normal stress component rather than the shear stress in the creep rupture. Creep rupture tests were conducted for nozzle and weld metal materials, respectively, at various temperature and stress levels. Stress distribution in the nozzle region is calculated using elastic-viscoplastic finite element analysis (FEA) using the measured properties. Calculation results are compared with earlier results based on the pure shear model of TMI-2 VIP. It is concluded from both LHF-4 nozzle examination and FEA that normal stress at the nozzle/lower head interface is the dominant driving force for the local failure. From the FEA for the nozzle weld attached in RPV, it is shown that nozzle welds failure occur by displacement controlled fracture of nozzle hole not by load controlled fracof nozzle hole not by load controlled fracture of internal pressure. Considering these characteristics of nozzle weld failure, new concept of nozzle failure time prediction is proposed

202

Measurements in a Transitional Boundary Layer Under Low-Pressure Turbine Airfoil Conditions  

Science.gov (United States)

This report presents the results of an experimental study of transition from laminar to turbulent flow in boundary layers or in shear layers over separation zones on a convex-curved surface which simulates the suction surface of a low-pressure turbine airfoil. Flows with various free-stream turbulence intensity (FSTI) values (0.5%, 2.5% and 10%), and various Reynolds numbers (50,000, 100,000 200,000 and 300,000) are investigated. Reynold numbers in the present study are based on suction surface length and passage exit mean velocity. Flow separation followed by transition within the separated flow region is observed for the lower-Re cases at each of the FSTI levels. At the highest Reynolds numbers and at elevated FSn, transition of the attached boundary layer begins before separation, and the separation zone is small. Transition proceeds in the shear layer over the separation bubble. For both the transitional boundary layer and the transitional shear layer, mean velocity, turbulence intensity and intermittency (the fraction of the time the flow is turbulent) distributions are presented. The present data are compared to published distribution models for bypass transition, intermittency distribution through transition, transition start position, and transition length. A model developed for transition of separated flows is shown to adequately predict the location of the beginning of transition, for these cases, and a model developed for transitional boundary layer flows seems to adequately predict the path of intermittency through transition when the transition start and end are known. These results are useful for the design of low-pressure turbine stages which are known to operate under conditions replicated by these tests.

Simon, Terrence W.; Qiu, Songgang; Yuan, Kebiao; Ashpis, David (Technical Monitor); Simon, Fred (Technical Monitor)

2000-01-01

203

The Impact of Hepatic Pressurization on Liver Shear Wave Speed Estimates in Constrained vs. Unconstrained Conditions  

OpenAIRE

Increased hepatic venous pressure can be observed in patients with advanced liver disease and congestive heart failure. This elevated portal pressure also leads to variation in acoustic radiation-force derived shear wave based liver stiffness estimates. These changes in stiffness metrics with hepatic interstitial pressure may confound stiffness-based predictions of liver fibrosis stage. The underlying mechanism for this observed stiffening behavior with pressurization is not well understood, ...

Rotemberg, V.; Palmeri, M.; Nightingale, R.; Rouze, N.; Nightingale, K.

2011-01-01

204

EXAFS and Raman studies of mechanical alloyed Ni25Se75 mixture under high-pressure conditions  

International Nuclear Information System (INIS)

Extended X-ray Absorption Fine Structure and Raman studies were performed to follow the structural and vibrational behavior of a mechanical alloyed Ni25Se75 mixture, containing nanocrystalline pyrite NiSe2 phase, when exposed to high-pressure conditions. An increase in the local structural order of the nanocrystalline phase with pressure increasing was observed by means of Debye-Waller factor analysis. The relative Ni nearest-neighbors distances were determined as a function of pressure, which were used to determine the inverse linear compressibility of the nanocrystalline pyrite NiSe2 alloy as well as its derivate by means of Murnaghan's equation. The Raman results showed tentative NiSe2 phonons dispersion with pressure that becomes a difficult task since the existence/photo-induced nucleation of an important amount of nanocrystalline Se, detected due to the observation of its pressure-induced phase transitions

205

On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow Conditions  

Science.gov (United States)

The present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off-design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05 , which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flow conditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re=50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding the physics of the separation phenomenon under periodic unsteady wake flow. Several physical mechanisms are discussed.

Schobeiri, Meinhard T.; Ozturk, Burak; Ashpis, David E.

2005-01-01

206

Measurement of subcooled boiling pressure drop and local heat transfer coefficient in horizontal tube under LPLF conditions  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? Measured subcooled boiling pressure drop and local heat transfer coefficient in horizontal tubes. ? Infra-red thermal imaging is used for wall temperature measurement. ? Developed correlations for pressure drop and local heat transfer coefficient. -- Abstract: Horizontal flow is commonly encountered in boiler tubes, refrigerating equipments and nuclear reactor fuel channels of pressurized heavy water reactors (PHWR). Study of horizontal flow under low pressure and low flow (LPLF) conditions is important in understanding the nuclear core behavior during situations like LOCA (loss of coolant accidents). In the present work, local heat transfer coefficient and pressure drop are measured in a horizontal tube under LPLF conditions of subcooled boiling. Geometrical parameters covered in this study are diameter (5.5 mm, 7.5 mm and 9.5 mm) and length (550 mm, 750 mm and 1000 mm). The operating parameters varied are mass flux (450–935 kg/m{sup 2} s) and inlet subcooling (29 °C, 50 °C and 70 °C). Infra-red thermography is used for the measurement of local wall temperature to estimate the heat transfer coefficient in single phase and two phase flows with water as the working medium at atmospheric pressure. Correlation for single phase diabatic pressure drop ratio (diabatic to adiabatic) as a function of viscosity ratio (wall temperature to fluid temperature) is presented. Correlation for pressure drop under subcooled boiling conditions as a function of Boiling number (Bo) and Jakob number (Ja) is obtained. Correlation for single phase heat transfer coefficient in the thermal developing region is presented as a function of Reynolds number (Re), Prandtl number (Pr) and z/d (ratio of axial length of the test section to diameter). Correlation for two phase heat transfer coefficient under subcooled boiling condition is developed as a function of boiling number (Bo), Jakob number (Ja) and Prandtl number (Pr)

Baburajan, P.K. [Atomic Energy Regulatory Board, Mumbai (India); Bisht, G.S. [Indian Institute of Technology, Bombay (India); Gupta, S.K. [Atomic Energy Regulatory Board, Mumbai (India); Prabhu, S.V., E-mail: svprabhu@iitb.ac.in [Indian Institute of Technology, Bombay (India)

2013-02-15

207

Test equipment for the determination of the corrosion fatigue of reactor materials under pressurized water reactor conditions  

International Nuclear Information System (INIS)

An experimental set-up was developed for the determination of corrosion fatigue properties under pressure water conditions. The design of the autoclave and its arrangement in a servo-hydraulic pulsator are described. Tests can be performed with this apparatus in pressure water up to 3500C and 165 bar with top loads of 20 000 N at frequencies up to 30 cycles per second. (orig.)

208

The Design Features of the High- and Intermediate-Pressure Cylinders with Forced Cooling for Turbines for Ultrasupercritical Steam Conditions  

Science.gov (United States)

The systems for forced steam cooling of the high-pressure rotor and stator and the intermediate-pressure rotor of a steam turbine for ultrasupercritical steam conditions developed at the Central Boiler-Turbine Institute Research and Production Association jointly with Leningrad Metal Works (a branch of OAO Silovye Mashiny) are considered. The results from calculations of the thermally stressed state of the cooled elements of the high- and intermediate-pressure cylinders have shown that the design solutions adopted for forced cooling of these elements are efficient and promising.

Petrenya, Yu. K.; Khomenok, L. A.; Pichugin, I. I.; Vladimirskii, O. A.; Lyapunov, V. M.; Lisyanskii, A. S.; Kachuriner, Yu. Ya.; Ignat'eva, T. A.; Ivanov, S. A.

2008-01-01

209

Cutting and conditioning of the reactor pressure vessel in the NPP Wuergassen; Zerlegung und Konditionierung des Reaktordruckgefaesses im Kernkraftwerk Wuergassen  

Energy Technology Data Exchange (ETDEWEB)

NPP Wuergassen was shutdown in 1995 after 23 years of operation. Since 1997 the nuclear power plant is being dismantled. The cutting of the reactor pressure vessel internals was performed between 2003 and 2008. After decontamination the cylindrical parts of the reactor pressure vessel were dissected, the process was finalized in 2010. AREVA has now a 30 years-experience concerning repair, replacement and dismantling of reactor components. In the contribution the authors describe the process planning, manufacture and testing of appropriate remote handled tools, decontamination, dissection of the pressure vessel (320 t), conditioning, packaging and transport of the radioactive waste including radiation protection monitoring.

Kraps, Uwe [AREVA NP GmbH, Erlangen (Germany); Duwe, Peter [E.ON Kernkraft GmbH, Bewerungen (Germany)

2011-07-01

210

Comparison Of Vented And Absolute Pressure Transducers For Water-Level Monitoring In Hanford Site Central Plateau Wells  

International Nuclear Information System (INIS)

Automated water-level data collected using vented pressure transducers deployed in Hanford Site Central Plateau wells commonly display more variability than manual tape measurements in response to barometric pressure fluctuations. To explain this difference, it was hypothesized that vented pressure transducers installed in some wells are subject to barometric pressure effects that reduce water-level measurement accuracy. Vented pressure transducers use a vent tube, which is open to the atmosphere at land surface, to supply air pressure to the transducer housing for barometric compensation so the transducer measurements will represent only the water pressure. When using vented transducers, the assumption is made that the air pressure between land surface and the well bore is in equilibrium. By comparison, absolute pressure transducers directly measure the air pressure within the wellbore. Barometric compensation is achieved by subtracting the well bore air pressure measurement from the total pressure measured by a second transducer submerged in the water. Thus, no assumption of air pressure equilibrium is needed. In this study, water-level measurements were collected from the same Central Plateau wells using both vented and absolute pressure transducers to evaluate the different methods of barometric compensation. Manual tape measurements were also collected to evaluate the transducers. Measurements collected during this study demonstrated that the vented pressure transducers over-responded to barometric pressure fluctuations due to a pressure disequilibrium between the air within the wellbores and the atmosphere at land surface. The disequilibrium is thought to be caused by the relatively long time required for barometric pressure changes to equilibrate between land surface and the deep vadose zone and may be exacerbated by the restriction of air flow between the well bore and the atmosphere due to the presence of sample pump landing plates and well caps. The disequilibrium is likely limited to wells screened across the water table (i.e., open to the deep vadose zone) where the depth to water is large or a low-permeability layer occurs in the vadose zone. Such wells are a pathway for air movement between the deep vadose zone and land surface and this sustains the pressure disequilibrium between the well bore and the atmosphere for longer time periods. Barometric over-response was not observed with the absolute pressure transducers because barometric compensation was achieved by directly measuring the air pressure within the well. Users of vented pressure transducers should be aware of the over-response issue in certain Hanford Site wells and ascertain if it will affect the use of the data. Pressure disequilibrium between the well and the atmosphere can be identified by substantial air movement through the wellbore. In wells exhibiting pressure disequilibrium, it is recommended that absolute pressure transducers be used rather than vented transducers for applications that require precise automated determinations of well water-level changes in response to barometric pressure fluctuations.

211

COMPARISON OF VENTED AND ABSOLUTE PRESSURE TRANSDUCERS FOR WATER-LEVEL MONITORING IN HANFORD SITE CENTRAL PLATEAU WELLS  

Energy Technology Data Exchange (ETDEWEB)

Automated water-level data collected using vented pressure transducers deployed in Hanford Site Central Plateau wells commonly display more variability than manual tape measurements in response to barometric pressure fluctuations. To explain this difference, it was hypothesized that vented pressure transducers installed in some wells are subject to barometric pressure effects that reduce water-level measurement accuracy. Vented pressure transducers use a vent tube, which is open to the atmosphere at land surface, to supply air pressure to the transducer housing for barometric compensation so the transducer measurements will represent only the water pressure. When using vented transducers, the assumption is made that the air pressure between land surface and the well bore is in equilibrium. By comparison, absolute pressure transducers directly measure the air pressure within the wellbore. Barometric compensation is achieved by subtracting the well bore air pressure measurement from the total pressure measured by a second transducer submerged in the water. Thus, no assumption of air pressure equilibrium is needed. In this study, water-level measurements were collected from the same Central Plateau wells using both vented and absolute pressure transducers to evaluate the different methods of barometric compensation. Manual tape measurements were also collected to evaluate the transducers. Measurements collected during this study demonstrated that the vented pressure transducers over-responded to barometric pressure fluctuations due to a pressure disequilibrium between the air within the wellbores and the atmosphere at land surface. The disequilibrium is thought to be caused by the relatively long time required for barometric pressure changes to equilibrate between land surface and the deep vadose zone and may be exacerbated by the restriction of air flow between the well bore and the atmosphere due to the presence of sample pump landing plates and well caps. The disequilibrium is likely limited to wells screened across the water table (i.e., open to the deep vadose zone) where the depth to water is large or a low-permeability layer occurs in the vadose zone. Such wells are a pathway for air movement between the deep vadose zone and land surface and this sustains the pressure disequilibrium between the well bore and the atmosphere for longer time periods. Barometric over-response was not observed with the absolute pressure transducers because barometric compensation was achieved by directly measuring the air pressure within the well. Users of vented pressure transducers should be aware of the over-response issue in certain Hanford Site wells and ascertain if it will affect the use of the data. Pressure disequilibrium between the well and the atmosphere can be identified by substantial air movement through the wellbore. In wells exhibiting pressure disequilibrium, it is recommended that absolute pressure transducers be used rather than vented transducers for applications that require precise automated determinations of well water-level changes in response to barometric pressure fluctuations.

MCDONALD JP

2011-09-08

212

An EELS and XAS study of cubic boron nitride synthesized under high pressure - high temperature conditions  

International Nuclear Information System (INIS)

Cubic Boron Nitride (c-BN) single-crystals have been synthesized under high pressure and high temperature conditions (HP-HT) using hexagonal Boron-Nitride (h-BN) precursors. We have performed a study of both phases with electron (EELS) and X-ray (XAS) spectroscopy that are compared. The c-BN ELNES spectra at B-K and N-K edges are found to be consistent with the Xanes (XAS) data, although the energy resolution achieved with X-rays is better than that obtained by EELS with a LaB6 filament. However, XAS is at a disadvantage by comparison with EELS owing to the presence o the N-K edge second order. Attempts were made to dope c-BN with carbon atoms. The examination of the EELS spectra reveals that the incorporation of carbon species in the BN material is always accompanied by the addition of oxygen. Several samples were analyzed both with selected area electron diffraction and energy loss spectroscopy. Most probed crystals containing C (and therefore O) were found to be hexagonal. These results emphasized that the range of existence of the cubic phase is very narrow around the binary composition. (authors). 20 refs., 11 figs

213

Nozzle failure mechanism of a water reactor pressure vessel under severe accident conditions  

International Nuclear Information System (INIS)

Most of past studies for the creep rupture of a nuclear reactor pressure vessel (RPV) lower head under severe accident conditions, have focused on global deformation and rupture modes. Limited efforts were made on local failure modes associated with penetration nozzles as a part of TMI-2 Vessel Investigation Project (TMI-2 VIP) in 1990's. However, it was based on an excessively simplified shear deformation model. In the present study, the mode of nozzle failures has been investigated using data and nozzle materials from Sandia National Laboratory's Lower Head Failure Experiment (SNL-LHF). Crack-like separations were revealed at the nozzle weld metal to RPV interfaces indicating the importance of normal stress component rather than the shear stress in the creep rupture. Creep rupture tests were conducted for nozzle and weld metal materials, respectively, at various temperature and stress levels. Stress distribution in the nozzle region is calculated using elastic-viscoplastic finite element analysis (FEA) using the measured properties. Calculation results are compared with earlier results based on the pure shear model of TMI-2 VIP. It has been concluded from both LHF-4 nozzle examination and FEA that normal stress at the nozzle/lower head interface is the dominant driving force for the local failure with its likelihood significantly greater than previously assumed. (authors)

214

Bundle critical power predictions under normal and abnormal conditions in pressurized water reactors  

International Nuclear Information System (INIS)

In this paper a new approach to bundle critical power predictions is presented. In addition to a very accurate critical heat flux (CHF) model, correction factors that account for the effects of grid spacers, heat flux non-uniformities, and cold walls, which are needed for critical power predictions for practical fuel bundles, are developed. By using the subchannel analysis code COBRA IIIC/MIT-1, local flow conditions needed as input to CHF correlations are obtained. Critical power is therefore obtained iteratively to ensure that the bundle power value from the subchannel analysis will cause CHF at only one point in the bundle. Good agreement with the experimental data is obtained. The accuracy is higher than that of the W-3 and EPRI-1 correlations for the limited data base used in this study. The effects of three types of fuel abnormalities, namely, local heat flux spikes, local flow blockages, and rod bowing, on bundle critical power are also analyzed. The local heat flux spikes and flow blockages have no significant influence on critical power. However, rod bowing phenomena have some effect, the severity of which depends on system pressure, the gap closure between adjacent rods, and the presence or absence of thimble tubes (cold walls). A correlation for the influence of various rod bowing phenomena on bundle critical power is developed. Good agreement with experimental data is shown

215

A study on the stem friction coefficient with differential pressure conditions for the motor operated flexible wedge gate valve  

International Nuclear Information System (INIS)

Stem friction coefficient is very important parameter for the evaluation of valve performance. In this study, the characteristics of stem friction coefficient is analyzed, and the bounding value is determined. The hydraulic testing is performed for flexible wedge gate valves in the plant and statistical method is applied to the determination of bounding value. According to the results of this study, stem friction coefficient is not effected in low differential pressure condition, but it is showed different distribution in medium and high differential pressure condition. And the bounding value of closing stroke is higher than that of opening stroke

216

Cyclic thermal shock crack propagation tests on the HDR-reactor pressure vessel nozzle under operating conditions  

International Nuclear Information System (INIS)

Within the framework of the HDR-Safety Research Program Cyclic Thermal Shock Tests were performed on a cladded reactor pressure vessel nozzle under operating conditions (temperature 3100C, pressure about 11 MPa). The whole round inner edge of the nozzle (diameter 200 mm) was sprayed with cold water by a special device. The main goal of these investigation is to contribute to the understanding of crack propagation of flaws under cyclic loading for adverse environmental water conditions. Furthermore, it is the object of the tests to monitor such cracks and the crack growth by non destructive technics as well as to assess and qualify the applied fracture analysis methods. (orig.)

217

Spatiotemporal variation of radon and carbon dioxide concentrations in an underground quarry: coupled processes of natural ventilation, barometric pumping and internal mixing  

International Nuclear Information System (INIS)

Radon-222 and carbon dioxide concentrations have been measured during several years at several points in the atmosphere of an underground limestone quarry located at a depth of 18 m in Vincennes, near Paris, France. Both concentrations showed a seasonal cycle. Radon concentration varied from 1200 to 2000 Bq m-3 in summer to about 800-1400 Bq m-3 in winter, indicating winter ventilation rates varying from 0.6 to 2.5 x 10-6 s-1. Carbon dioxide concentration varied from 0.9 to 1.0% in summer, to about 0.1-0.3% in winter. Radon concentration can be corrected for natural ventilation using temperature measurements. The obtained model also accounts for the measured seasonal variation of carbon dioxide. After correction, radon concentrations still exhibit significant temporal variation, mostly associated with the variation of atmospheric pressure, with coupling coefficients varying from -7 to -26 Bq m-3 hPa-1. This variation can be accounted for using a barometric pumping model, coupled with natural ventilation in winter, and including internal mixing as well. After correction, radon concentrations exhibit residual temporal variation, poorly correlated between different points, with standard deviations varying from 3 to 6%. This study shows that temporal variation of radon concentrations in underground cavities can be understood to a satisfactory level of detail using non-linear and time-dependent modelling. Iton-linear and time-dependent modelling. It is important to understand the temporal variation of radon concentrations and the limitations in their modelling to monitor the properties of natural or artificial underground settings, and to be able to assess the existence of new processes, for example associated with the preparatory phases of volcanic eruptions or earthquakes.

218

Sulphate chemistry under pressurized oxidizing, reducing and fluctuating conditions; Sulfatkemi under trycksatta oxiderande, reducerande och fluktuerande foerhaallanden  

Energy Technology Data Exchange (ETDEWEB)

In the literature it has been reported that sulfur capture with limestone (CaCO{sub 3}) under atmospheric fluidized bed combustion conditions reaches a maximum at about 850 deg C. Previously, the maximum has been attributed to the sintering of sorbent particles which decreases the reactive surface area. Lately, also another explanation has been reported. In this case the sulfur capture decrease at higher temperatures was concluded to be due to fluctuating oxidizing/reducing conditions in the atmospheric combustor. In this work the influence of alternating oxidizing/reducing conditions on SO{sub 2} capture at atmospheric and elevated pressure (15 bar) has been studied. In the pressurized case, the CO{sub 2} partial pressure was kept high enough to prevent CaCO{sub 3} from calcining and therefore the CaSO{sub 4} would not form CaO but CaCO{sub 3} under reducing conditions. The experiments were done with a pressurized TGA by periodically changing the gas environment between oxidizing (O{sub 2}. SO{sub 2}, CO{sub 2} and N{sub 2}) and slightly reducing (CO, SO{sub 2}, CO{sub 2} and N{sub 2}) gas mixtures at different temperatures. The results from the experiments showed that under normal pressure and slightly reducing conditions CaO formation from CaSO{sub 4} increased with temperature as expected. However, no significant amounts of CaCO{sub 3} were formed from CaSO{sub 4} at elevated pressure. It was also concluded that since the formation of CaO from CaSO{sub 4} was relatively slow it could not explain the sharp sulfur capture maximum at about 850 deg C. Therefore, it was assumed that the strongly reducing zones, where CaS thermodynamically is the stable compound, play a more important role concerning the sulfur capture in fluidized bed combustors. (orig.)

Hupa, M.; Yrjas, P.; Backman, P. [Aabo Akademi, Turku (Finland). Combustion Chemistry Research Group

1997-10-01

219

An Inexpensive Arterial Pressure Wave Sensor and its application in different physiological condition  

CERN Document Server

Arterial Blood Pressure wave monitoring is considered to be important in assessment of cardiovascular system. We developed a novel pulse wave detection system using low frequency specific piezoelectric material as pressure wave sensor. The transducer detects the periodic change in the arterial wall diameter produced by pressure wave and the amplified signal after integration represents the pressure wave. The signal before integration is proportional to the rate of change of pressure wave and it not only reproduces the pressure waveform faithfully, but also its sharper nature helps to reliably detect the heart period variability (HPV). We have studied the position-specific (e.g. over carotid or radial artery) nature of change of this pulse wave signal (shape and amplitude) and also the changes at different physiological states.

Sur, S; Sur, Shantanu

2005-01-01

220

Outflow boundary conditions for 3D simulations of non-periodic blood flow and pressure fields in deformable arteries  

CERN Document Server

The simulation of blood flow and pressure in arteries requires outflow boundary conditions that incorporate models of downstream domains. We previously described a coupled multidomain method to couple analytical models of the downstream domains with 3D numerical models of the upstream vasculature. This prior work either included pure resistance boundary conditions or impedance boundary conditions based on assumed periodicity of the solution. However, flow and pressure in arteries are not necessarily periodic in time due to heart rate variability, respiration, complex transitional flow or acute physiological changes. We present herein an approach for prescribing lumped parameter outflow boundary conditions that accommodate transient phenomena. We have applied this method to compute haemodynamic quantities in different physiologically relevant cardiovascular models, including patient-specific examples, to study non-periodic flow phenomena often observed in normal subjects and in patients with acquired or congen...

Vignon-Clementel, Irene; Jansen, K E; Taylor, C A; 10.1080/10255840903413565

2010-01-01

221

Pressure-stability of phospholipid bicelles: measurement of residual dipolar couplings under extreme conditions.  

Science.gov (United States)

High-pressure NMR of proteins in solutions currently gains increasing interest. 3D structure determination of proteins under high pressure is, however, so far impossible due to the lack of NOE information. Residual dipolar couplings induced by the addition of magnetically orienting media are known to be capable of replacing NOE information to a very high extent. In the present contribution we study the pressure-stability of dimyristoylphosphatidylcholine (DMPC)/dihexanoylphosphatidylcholine (DHPC) bicelles and demonstrate the feasibility of measuring residual dipolar couplings in proteins under high pressure. PMID:11727981

Brunner, E; Arnold, M R; Kremer, W; Kalbitzer, H R

2001-10-01

222

Pressure-stability of phospholipid bicelles: Measurement of residual dipolar couplings under extreme conditions  

International Nuclear Information System (INIS)

High-pressure NMR of proteins in solutions currently gains increasing interest. 3D structure determination of proteins under high pressure is, however, so far impossible due to the lack of NOE information. Residual dipolar couplings induced by the addition of magnetically orienting media are known to be capable of replacing NOE information to a very high extent. In the present contribution we study the pressure-wstability of dimyristoylphosphatidylcholine (DMPC)/ dihexanoylphosphatidylcholine (DHPC) bicelles and demonstrate the feasibility of measuring residual dipolar couplings in proteins under high pressure

223

Leakage rate through a non-cracked concrete wall, comparison between two situations: Air pressure test and accident conditions  

International Nuclear Information System (INIS)

This experimental research investigated the behaviour of a concrete wall, with a local zone very permeable to air, subjected to accident conditions. The high level of permeability in the concrete was obtained for one specimen with a porous concrete having connected pores (intrinsic permeability of 10-16 m2). The aim of this work was to study comparatively, in the laboratory, the permeability of a non-cracked concrete wall under two conditions. A cylindrical specimen 1.3 m thick was used. No appreciable stresses were applied on the concrete. The first condition was at ambient temperature, under an increasing pressure (up to 0.42 MPa) of the air applied on one face of the specimen, the other one being at atmospheric pressure. The second condition was an accident scenario with simultaneous effects of temperature and gas (a mix of air and steam) pressure applied on one face, the other one remaining at atmospheric pressure and temperature. During the test, the lateral face of the cylindrical specimen was thermally isolated and made leak tight. So, a uni-dimensional experimental analysis was performed. The accident conditions consisted of a rise from ambient conditions to a temperature of 141 deg C and a relative pressure of 0.42 MPa (steam pressure of 0.377 MPa and air pressure of 0.043 MPa) for 3 h, the maximum values remaining constant for several days. Thermocouples, pressure taps and moisture gauges were implanted in the specimens at the moment ofmplanted in the specimens at the moment of casting, to provide local information about the inner wall under the simultaneous effects of temperature and steam pressure. Outside the specimen, the chamber enclosed a condenser with a humidity meter and thermocouple, so it was possible to quantify separately the saturated airflow with a flow-metre and the condensed water. During the permeability test at ambient temperature, the field of pressure was affected by the variation of local permeability of the concrete. Furthermore, some movement of interstitial water inside the specimen induced an increase of the predicted outflow, no liquid phase appeared. For the natural porous concrete, during accident testing, the field of pressure advanced slowly, the outflow progressively increased to obtain a maximum at 70 h, after this time on the one hand the airflow rate decreased and became equal to zero; on the other hand, the liquid flow rate was constant, at the end of the test, about 30 cm of the specimen was water saturated. A uni-dimensional numerical analysis was performed. The Tham model (non-saturated porous media thermo-hydro-mechanic) included in CodeAster[reg] was used. Two fluid phases can be considered in the material: a liquid phase (water) and a gas phase (dry air plus vapour) with the liquid/vapour phase changes. The thermodynamic aspects dealt with open systems framework, with temperature, capillary pressure and gas total pressure as variables. Observing the considered conditions (progressive saturation of the wall), the shape of sorption isotherm and permeabilities had an important influence on the results. The numerical results were in good agreement with experimental results, on the phenomenology and on flow rate through the wall. This study gave some indicators about the relations between airflow during a permeability test and gas (air + steam) flows during accident testing

224

Experimental determination of heat transfer critical conditions in water forced convection at low pressure in a circular channel  

International Nuclear Information System (INIS)

An experimental determination was made of heat transfer critical conditions in a circular channel, uniformly heated, and internally cooled by water in ascending forced convection, under a pressure slightly above atmospheric pressure. Measurements were made of water flow, pressure, electric power temperature and heating, and a systematic analysis was made of the system's parameters. The values obtained for the heat critical flux are circa 50% lower than those predicted by Becker and Biasi and this is accounted to flowing instabilities of thermo-hydrodynamic nature. It is suggested that the flowing channels of circuits aiming at the study of the boiling crisis phenomenon be expanded in its upper extremity, and that the coolant circulation be kept through a pump with a pressure X flow characteristic as vertical as possible

225

The lubrication characteristics of the vane tip under inlet pressure boundary conditions for an oil hydraulic vane pump  

International Nuclear Information System (INIS)

The lubrication modes of line contact between the vane and the camring in an oil hydraulic vane pump have been investigated. First, variations of the radial acting force of a vane were calculated from previously measured results of the dynamic internal pressure in four chambers surrounding a vane. Next, distinctions of the lubrication modes were made using Hooke's chart, which represents an improvement over Johnson's chart. Finally, the influence of boundary conditions in the lubrication region on fluid film lubrication was examined by calculating film pressure distributions. The results show that the lubrication modes on the vane tip are a rigid-variable viscosity region. This region discharges pressure higher than 7 MPa, and exerts a great influence on oil film pressure in the large arc section due to the Peizo-viscous effect

226

Analysis of flow induced valve operation and pressure wave propagation for single and two-phase flow conditions  

International Nuclear Information System (INIS)

The flow induced valve operation is calculated for single and two-phase flow conditions by the fluid dynamic computer code DYVRO and results are compared to experimental data. The analysis show that the operational behaviour of the valves is not only dependent on the condition of the induced flow, but also the pipe flow can cause a feedback as a result of the induced pressure waves. For the calculation of pressure wave propagation in pipes of which the operation of flow induced valves has a considerable influence it is therefore necessary to have a coupled analysis of the pressure wave propagation and the operational behaviour of the valves. The analyses of the fast transient transfer from steam to two-phase flow show a good agreement with experimental data. Hence even these very high loads on pipes resulting from such fluid dynamic transients can be calculated realistically. (orig.)

227

Flow Control Under Low-Pressure Turbine Conditions Using Pulsed Jets: Experimental Data Archive  

Science.gov (United States)

This publication is the final report of research performed under an NRA/Cooperative Interagency Agreement, and includes a supplemental CD-ROM with detailed data. It is complemented by NASA/CR-2012-217416 and NASA/CR-2012-217417 which include a Ph.D. Dissertation and an M.S. thesis respectively, performed under this contract. In this study the effects of unsteady wakes and flow control using vortex generator jets (VGJs) were studied experimentally and computationally on the flow over the L1A low pressure turbine (LPT) airfoil. The experimental facility was a six passage linear cascade in a low speed wind tunnel at the U.S. Naval Academy. In parallel, computational work using the commercial code FLUENT (ANSYS, Inc.) was performed at Cleveland State University, using Unsteady Reynolds Averaged Navier Stokes (URANS) and Large Eddy Simulations (LES) methods. In the first phase of the work, the baseline flow was documented under steady inflow conditions without flow control. URANS calculations were done using a variety of turbulence models. In the second phase of the work, flow control was added using steady and pulsed vortex generator jets. The VGJs successfully suppressed separation and reduced aerodynamic losses. Pulsed operation was more effective and mass flow requirements are very low. Numerical simulations of the VGJs cases showed that URANS failed to capture the effect of the jets. LES results were generally better. In the third phase, effects of unsteady wakes were studied. Computations with URANS and LES captured the wake effect and generally predicted separation and reattachment to match the experiments. Quantitatively the results were mixed. In the final phase of the study, wakes and VGJs were combined and synchronized using various timing schemes. The timing of the jets with respect to the wakes had some effect, but in general once the disturbance frequency was high enough to control separation, the timing was not very important. This is the supplemental CD-ROM

Volino, Ralph J.; Ibrahim, Mounir B.

2012-01-01

228

Flow Control Under Low-Pressure Turbine Conditions Using Pulsed Jets  

Science.gov (United States)

This publication is the final report of research performed under an NRA/Cooperative Interagency Agreement, and includes a supplemental CD-ROM with detailed data. It is complemented by NASA/CR-2012-217416 and NASA/CR-2012-217417 which include a Ph.D. Dissertation and an M.S. thesis respectively, performed under this contract. In this study the effects of unsteady wakes and flow control using vortex generator jets (VGJs) were studied experimentally and computationally on the flow over the L1A low pressure turbine (LPT) airfoil. The experimental facility was a six passage linear cascade in a low speed wind tunnel at the U.S. Naval Academy. In parallel, computational work using the commercial code FLUENT (ANSYS, Inc.) was performed at Cleveland State University, using Unsteady Reynolds Averaged Navier Stokes (URANS) and Large Eddy Simulations (LES) methods. In the first phase of the work, the baseline flow was documented under steady inflow conditions without flow control. URANS calculations were done using a variety of turbulence models. In the second phase of the work, flow control was added using steady and pulsed vortex generator jets. The VGJs successfully suppressed separation and reduced aerodynamic losses. Pulsed operation was more effective and mass flow requirements are very low. Numerical simulations of the VGJs cases showed that URANS failed to capture the effect of the jets. LES results were generally better. In the third phase, effects of unsteady wakes were studied. Computations with URANS and LES captured the wake effect and generally predicted separation and reattachment to match the experiments. Quantitatively the results were mixed. In the final phase of the study, wakes and VGJs were combined and synchronized using various timing schemes. The timing of the jets with respect to the wakes had some effect, but in general once the disturbance frequency was high enough to control separation, the timing was not very important.

Volino, Ralph J.; Ibrahim, Mounir B.

2012-01-01

229

Photochemical modelling of the Barcelona area under weak pressure synoptic summer conditions  

International Nuclear Information System (INIS)

This city of Barcelona and its surrounding area, located in the western Mediterranean basin, can reach high levels of O3 in summertime under weak pressure synoptic conditions. To study the origin of this photochemical pollution, the episode that took place between the 3 and 5 August 1990 was chosen. The main meteorological mesoscale flows that take place in the region, such as sea and land breeze, convection cells and topographic injections, were reproduced with the meteorological non-hydrostatic mesoscale model MEMO for 5 August 1990. Industrial and commercial activity on 5 August 1990 was very low because it was a Sunday in the summer holiday period. Therefore, the emissions inventory calculated for this day in an area of 80x80 km2 around Barcelona showed that the main sources of VOC were traffic (51%) and vegetation (34%), while NOx were mostly emitted by traffic (88%). Photochemical simulation with the MARS model has shown that the combination of mesoscale circulations and local emissions is crucial in the production of O3. For instance, NOx inland transport towards regions where biogenic VOC are emitted causes the formation of O3, while topographic injections cause the formation of elevated O3 air layers. The synoptic wind, coming from the northeast in this case, also played an important role in advecting the air masses with local generated O3 away from their precursor emissio>3 away from their precursor emission sources. Evaluation of the model simulations is also performed and discussed by means of comparison of meteorological measurements in 9 surface stations and concentration measurements in 5 surface stations. (Author)

230

Multiple uncontrolled conditions and blood pressure medication intensification: an observational study  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Multiple uncontrolled medical conditions may act as competing demands for clinical decision making. We hypothesized that multiple uncontrolled cardiovascular risk factors would decrease blood pressure (BP medication intensification among uncontrolled hypertensive patients. Methods We observed 946 encounters at two VA primary care clinics from May through August 2006. After each encounter, clinicians recorded BP medication intensification (BP medication was added or titrated. Demographic, clinical, and laboratory information were collected from the medical record. We examined BP medication intensification by presence and control of diabetes and/or hyperlipidemia. 'Uncontrolled' was defined as hemoglobin A1c ? for diabetes, BP ? 140/90 mmHg (? 130/80 mmHg if diabetes present for hypertension, and low density lipoprotein cholesterol (LDL-c ? 130 mg/dl (? 100 mg/dl if diabetes present for hyperlipidemia. Hierarchical regression models accounted for patient clustering and adjusted medication intensification for age, systolic BP, and number of medications. Results Among 387 patients with uncontrolled hypertension, 51.4% had diabetes (25.3% were uncontrolled and 73.4% had hyperlipidemia (22.7% were uncontrolled. The BP medication intensification rate was 34.9% overall, but higher in individuals with uncontrolled diabetes and uncontrolled hyperlipidemia: 52.8% overall and 70.6% if systolic BP ? 10 mmHg above goal. Intensification rates were lowest if diabetes or hyperlipidemia were controlled, lower than if diabetes or hyperlipidemia were not present. Multivariable adjustment yielded similar results. Conclusions The presence of uncontrolled diabetes and hyperlipidemia was associated with more guideline-concordant hypertension care, particularly if BP was far from goal. Efforts to understand and improve BP medication intensification in patients with controlled diabetes and/or hyperlipidemia are warranted.

Halanych Jewell H

2010-07-01

231

Navier-Stokes equations with periodic boundary conditions and pressure loss  

CERN Document Server

We present in this note the existence and uniqueness results for the Stokes and Navier-Stokes equations which model the laminar flow of an incompressible fluid inside a two-dimensional channel of periodic sections. The data of the pressure loss coefficient enables us to establish a relation on the pressure and to thus formulate an equivalent problem.

Amrouche, Chérif; Batina, Jean

2007-01-01

232

Local charge transport properties of hydrazine reduced monolayer graphene oxide sheets prepared under pressure condition  

DEFF Research Database (Denmark)

Charge transport properties of chemically reduced graphene oxide (RGO) sheets prepared by treatment with hydrazine were examined using conductive atomic force microscopy. The current-voltage (I-V) characteristics of monolayer RGO sheets prepared under atmospheric pressure followed an exponentially increase due to 2D variable-range hopping conduction through small graphene domains in an RGO sheet containing defect regions of residual sp3carbon clusters bonded to oxygen groups, whereas RGO sheets prepared in a closed container under moderate pressure showed linear I-V characteristics with a conductivity of 267.2-537.5S/m. It was found that the chemical reduction under pressure results in larger graphene domains (sp2networks) in the RGO sheets when compared to that prepared under atmospheric pressure, indicating that the present reduction of GO sheets under the pressure is one of the effective methods to make well-reduced GO sheets.

Ryuzaki, Sou; Meyer, Jakob A S

2014-01-01

233

Local charge transport properties of hydrazine reduced monolayer graphene oxide sheets prepared under pressure condition  

Science.gov (United States)

Charge transport properties of chemically reduced graphene oxide (RGO) sheets prepared by treatment with hydrazine were examined using conductive atomic force microscopy. The current-voltage (I-V) characteristics of monolayer RGO sheets prepared under atmospheric pressure followed an exponentially increase due to 2D variable-range hopping conduction through small graphene domains in an RGO sheet containing defect regions of residual sp3 carbon clusters bonded to oxygen groups, whereas RGO sheets prepared in a closed container under moderate pressure showed linear I-V characteristics with a conductivity of 267.2-537.5 S/m. It was found that the chemical reduction under pressure results in larger graphene domains (sp2 networks) in the RGO sheets when compared to that prepared under atmospheric pressure, indicating that the present reduction of GO sheets under the pressure is one of the effective methods to make well-reduced GO sheets.

Ryuzaki, Sou; Meyer, Jakob A. S.; Petersen, Søren; Nørgaard, Kasper; Hassenkam, Tue; Laursen, Bo W.

2014-09-01

234

Thermal hydraulic mixing in the primary system of a pressurized water reactor during high pressure safety injection under stagnated loop conditions  

International Nuclear Information System (INIS)

One of the key safety issues currently addressed by the PWR industry is the retention of structural integrity of the pressure vessel during certain high pressure overcooling transients popularly called Pressurized Thermal Shock (PTS). Among the various modes by which a reactor can experience PTS, the high pressure safety injection under stagnated loop conditions is the most severe from the standpoint of overcooling the system. The present work uses a two pronged approach to predict the temperature transients in the primary system under these circumstances. The first approach is to characterize the system response experimentally in a 1/2-scale (of a typical 3000 MW/sub th/ plant) model facility using brine and fresh water as stimulant fluids. The mixing is quantified by the measurement of mean and turbulent concentration and velocity at key locations of interest using electrical conductivity and hot wire probes. Secondly, a computer code is developed that solves the system of governing differential equations using the finite different method. The code is validated against a comprehensive data base

235

Transient behavior of pressure and wall temperature in water flow in a tube under flow reduction conditions  

International Nuclear Information System (INIS)

Flow reduction transient boiling phenomena have been studied in vertical up-flow of water in a tube under an atmospheric pressure to provide information on the transient thermal-hydraulic behavior of a LWR core during Power Cooling Mismatch (PCM) conditions. The electrically heated test section was stainless steel tube 8 mm in diameter and 800 mm long. Experiment was conducted under the conditions; inlet water temperature = 30 -- 800C heat flux = 0.54 -- 1.1 x 106 kcal/hm2, initial mass velocity=3.6 -- 8.4 x 106 kg/hm2, and flow reduction time = 0.05 -- 62 sec. According to the observed behavior of the pressure and wall temperature, the flow reduction transient boiling phenomena are similar to those in the steady-state boiling at flow reduction rates below about 10cm/sec/sec under the ranges of experimental conditions. (auth.)

236

Valve inlet fluid conditions for pressurizer safety and relief valves in Westinghouse-designed plants. Final report  

International Nuclear Information System (INIS)

The overpressure transients for Westinghouse-designed NSSSs are reviewed to determine the fluid conditions at the inlet to the PORV and safety valves. The transients considered are: licensing (FSAR) transients; extended operation of high pressure safety injection system; and cold overpressurization. The results of this review, presented in the form of tables and graphs, define the range of fluid conditions expected at the inlet to pressurized safety and power-operated relief valves utilized in Westinghouse-designed PWR units. These results will provide input to the PWR utilities in their justification that the fluid conditions under which their valve designs were tested as part of the EPRI/PWR Safety and Relief Valve Test Program indeed envelop those expected in their units

237

Effect of Normal Operating Condition Analysis Method for Weld Residual Stress of CD-ROM Nozzle in Reactor Pressure Vessel  

International Nuclear Information System (INIS)

In pressurized water nuclear reactors (PWRs), the reactor pressure vessel (RSV) upper head contains penetration nozzles that use a control rod drive mechanism (CD-ROM). The penetration nozzle uses J-groove weld geometry. Recently, the occurrence of cracking in alloy 600 CD-ROM penetration nozzle has increased. This is attributable to primary water stress corrosion cracking (PWSCC). PWSCC is known to be susceptible to the welding residual stress and operational stress. Generally, the tensile residual stress is the main factor contributing to crack growth. Therefore, this study investigates the effect on weld residual stress through different analysis methods for normal operating conditions using finite element analysis. In addition, this study also considers the effect of repeated normal operating condition cycles on the weld residual stress. Based on the analysis result, this paper presents a normal operating condition analysis method

238

A flow and pressure distribution of APR+ reactor under 4-pump running conditions with a balanced flow rate  

International Nuclear Information System (INIS)

In order to quantify the flow distribution characteristics of APR+ reactor, a test was performed on a test facility, ACOP (APR+ Core Flow and Pressure Test Facility), having a length scale of 1/5 referring to the prototype plant. The major parameters are core inlet flow and outlet pressure distribution and sectional pressure drops along the major flow path inside reactor vessel. To preserve the flow characteristics of prototype plant, the test facility was designed based on a preservation of major flow path geometry. An Euler number is considered as primary dimensionless parameter, which is conserved with a 1/40.9 of Reynolds number scaling ratio. ACOP simplifies each fuel assembly into a hydraulic simulator having the same axial flow resistance and lateral cross flow characteristics. In order to supply boundary condition to estimate thermal margins of the reactor, the distribution of inlet core flow and core exit pressure were measured in each of 257 fuel assembly simulators. In total, 584 points of static pressure and differential pressures were measured with a limited number of differential pressure transmitters by developing a sequential operation system of valves. In the current study, reactor flow characteristics under the balanced four cold leg flow conditions at each of the cold legs were quantified, which is a part of the test matrix composing the APR+ flow distribution test program. The final identification of the reactor flow distribution was obtained by enactor flow distribution was obtained by ensemble averaging 15 independent test data. The details of the design of the test facility, experiment, and data analysis are included in the current paper.

239

An experimental investigation of the creep sag of pressure tubes under LOCA conditions  

International Nuclear Information System (INIS)

During a postulated loss-of-coolant accident with impaired emergency cooling, the heat generated in the fuel will be transferred to the moderator. In the process, the pressure tube will heat and may deform into contact with its calandria tube. This paper describes experiments that were performed to investigate the sagging deformation of a pressure tube when a transient temperature is applied. The pressure-tube deflection and temperature were monitored. The contact between the pressure tube and calandria tube was observed, and the resulting type of boiling on the calandria-tube surface was noted, since this controls the rate of heat removal from the fuel channel. The experimental results were compared with computer predictions of the deformation. The computer models predicted the behaviour well

240

Note: New feedthrough insulation method for the dielectric spectroscopy under ultrahigh pressure conditions  

Science.gov (United States)

We present a new technique to prepare insulated channels for the high pressure cell used in broadband dielectric spectroscopy. The cell resists corrosion or other chemical reactions from the reactive sample liquids. The cell maintains electrical insulation between electrode contacts better than 100 G? as well as good mechanical properties in broad temperature range of -80to+100 °C and under extremely high pressures up to 1.8 GPa.

Mierzwa, Michal; Pawlus, Sebastian; Paluch, Marian; Zio?o, Jerzy; Szulc, Andrzej

2010-06-01

241

Contrasting P-T conditions recorded in ultramafic high-pressure rocks from the Variscan Schwarzwald (F.R.G.)  

Science.gov (United States)

This paper presents mineralogical and tex-tural data as well as thermobarometric calculations on ultramafic high-pressure rocks from the Variscan basement of the Schwarzwald (F.R.G.). The rocks form small isolated bodies within low-pressure / high-temperature gneisses and migmatites. The results of this study constrain contrasting P-T evolutions for four garnet-bearing ultramafic high-pressure rocks. Two magnesian garnet-spinal peridotites sampled near the southern margin of the Central Schwarzwald Gneiss Complex (CSGC) were equilibrated at 670-740° C and 1.4-1.8 GPa. These P-T conditions are similar to those recorded by eclogites intercalated in the same basement unit. Two garnet websterites sampled from the northern part of the CSGC have comparatively low Mg/(Mg + Fe) and low Cr and Ni abundances and are interpreted as former cumulates. These rocks most probably experienced an initial high-temperature stage within the spinel peridotite stability field, followed by re-equilibration at 740-850° C/3.2-4.3 GPa and subsequent recrystallization at lower pressures. Further petrologic studies have to reveal whether ultramafic high-pressure rocks of the Schwarzwald can generally be assigned to these two groups which are mainly defined by contrasting peak pressures.

Kalt, Angelika; Altherr, Rainer; Hanel, Michael

1995-08-01

242

A pressure correction scheme for generalized form of energy-stable open boundary conditions for incompressible flows  

CERN Document Server

We present a generalized form of open boundary conditions, and an associated numerical algorithm, for simulating incompressible flows involving open or outflow boundaries. The generalized form represents a family of open boundary conditions, which all ensure the energy stability of the system, even in situations where strong vortices or backflows occur at the open/outflow boundaries. Our numerical algorithm for treating these open boundary conditions is based on a rotational pressure correction-type strategy, with a formulation suitable for $C^0$ spectral-element spatial discretizations. We have introduced a discrete equation and associated boundary conditions for an auxiliary variable. The algorithm contains constructions that prevent a numerical locking at the open/outflow boundary. In addition, we have also developed a scheme with a provable unconditional stability for a sub-class of the open boundary conditions. Extensive numerical experiments have been presented to demonstrate the performance of our meth...

Dong, Suchuan

2014-01-01

243

Re-investigation of the crystal structure of enstatite under high-pressure conditions  

DEFF Research Database (Denmark)

A synthetic single crystal of pure orthoenstatite (MgSiO3, space group Pbca) has been investigated at high pressure for structural determinations by in situ single-crystal X?ray diffraction using a diamond-anvil cell. Ten complete intensity data collections were performed up to 9.36 GPa. This study significantly improved the accuracy of structural parameters in comparison to a previous high-pressure structural study, allowing a more detailed examination of structural behavior of orthoenstatite at high pressures and a comparison to other more recent structural studies performed on orthopyroxenes with different compositions. The structural evolution determined in this work confirms the high-pressure evolution found previously for other orthopyroxenes and removes some ambiguities originating from the less accurate published data on the MgSiO3 structure at high pressure. The structural compression is mostly governed by significant volume decrease of the Mg1 and Mg2 octahedra, affecting in turn the kink of the tetrahedral chains, especially the TB chain of larger SiO4 tetrahedra. The Mg2 polyhedron undergoes the largest volume variation, 8.7%, due especially to the strong contraction of the longest bond distance (Mg2-O3B), whereas Mg1 polyhedral volume decreases by about 7.4%. The compressional behavior of the tetrahedral sites is quite different from previously published data. The TA and TB tetrahedral volumes decrease by about 2.8 and 1.8%, respectively, and no discontinuities can be observed in the pressure range investigated. Using the data on the pure orthoenstatite as reference, we can confirm the basic influences of element substitutions on the evolution of the crystal structure with pressure.

Periotto, Benedetta; Balic Zunic, Tonci

2012-01-01

244

Evaluation of environmentally-assisted cracking in the simulated PWR primary water conditions for pressure vessel and piping materials  

International Nuclear Information System (INIS)

Two pressure vessel steels (A533 Gr.B, cl.1 and A508 cl.3) and high strength cast and forged stainless steels (CF8A and 316LN) which have been expected as the promising piping materials for PWR primary piping systems were evaluated concerning the reliability in the simulated PWR primary water conditions. Metallurgical and mechanical properties of these new materials lied completely within the specifications. Corrosion fatigue tests for the reactor pressure vessel steels and stress corrosion cracking tests for stainless steels were performed in simulated PWR high temperature water environment. The results are sammarized as follows: (1) Reactor Pressure Vessel Steels (A533B cl.1 and A508 cl.3). Both under air and high temperature water conditions, no significant difference of the fatigue crack growth rate was found in these steels. In comparison with the ASME reference curves in air, a little acceleration effect on crack growth rate in the water condition was observed in a certain stress intensity factor range (low ?K). This environmentally assisted crack growth rate could be negligible. (2) SCC Resistance of cast and forged Stainless Steels (CF8A and 316LN). Following three kinds of SCC tests, constant extention rate test, cyclic tensile test and constant load test were conducted. Even in the heavily sensitized stainless steels, no SCC was observed. These results indicate that CF8A and 316LN stainless steels have enough resistance against SCC in the PWR primary water nce against SCC in the PWR primary water condition. (author)

245

Void fraction under high pressure, low flow conditions in rod bundle geometry  

International Nuclear Information System (INIS)

Void-fraction data are reported from a series of high pressure, low heat and mass flux experiments. Testing was performed in a heated vertical rod bundle with internal dimensions similar to a PWR fuel bundle. The results are of interest in analyses of small break loss of coolant accidents. The experiments showed that, at a given pressure, void-fraction data could be fitted to a drift-flux equation with a constant drift-velocity. The drift-velocity was observed to decrease with increasing pressure and was independent of void fraction: a characteristic normally associated with churn-turbulent flow. However, relevant drift-flux correlations found in the literature gave relatively poor predictions of void fractions. The best predictions were obtained from an empirical correlation based on dimensional analyses. (orig.)

246

Critical heat flux for rod bundle under high-pressure boil-off conditions  

International Nuclear Information System (INIS)

Critical heat flux (CHF) tests were carried out using a 5 x 5 rod bundle test section of the Two-Phase Flow Test Facility (TPTF). The tests represented high-pressure core inventory boil-off and rod dryout situations which may occur during a small break loss-of-coolant accident (LOCA) or an anticipated transient without scram (ATWS) in a light water reactor. Pressures ranging from 3 to 12 MPa, mass fluxes from 17 to 94 kg/m2·s and heat fluxes from 3.3 to 18 W/cm2 were covered. Data were compared with low-flow boiling CHF correlations to examine the applicability of these correlations to high-pressure boil-off. The dryout in the tests occurred at an elevation where the equilibrium quality nearly reached unity. (author)

247

Void fraction predictions in rod bundles at low-pressure low-flow conditions based on Cunningham-Yeh model  

International Nuclear Information System (INIS)

Many experiments have been conducted in the past with full-scale rod bundles to develop void fraction correlations or interfacial drag model which can be used to predict the mixture level in a reactor core following a postulated Loss of Coolant Accident (LOCA). The Cunningham and Yeh correlation was originally developed and validated with boil-off data obtained in the 100 to 400 psi pressure range. Subsequently the validity of the correlation was successfully assessed against several other experiments. However most of the data concentrated in the intermediate to high pressure range (from 100 to 2200 psi). More recently, the development of advanced passive plant such as the AP1000, put more emphasis in the level swell behavior in the near-atmospheric pressure conditions. Following a postulated SBLOCA event for the AP1000 design, the reactor vessel is automatically de-pressurized to a near atmospheric condition and in the long term the core decay heat is removed by gravity driven injection flow while boiling is occurring in the core. In this paper the Cunningham-Yeh correlation was assessed against data beyond its original data base. Cunningham-Yeh model predictions were compared to several low-flow, low-pressure full-scale rod bundle experiments. Results show that the correlation performs relatively well against low pressure test data. However the Cunningham-Yeh model has the tendency to underpredict the void fraction and therefore to provide conservative results of lefore to provide conservative results of level swell for plant safety analysis. (authors)

248

Condensation phenomena in BWR-pressure suppression containments under LOCA conditions  

International Nuclear Information System (INIS)

Experimental studies on condensation phenomena in pressure suppression systems (PSS) have shown, that chugging produces the major dynamic loads in a PSS. Time correlation of digital and visual data have produced understanding of the essential physics of this phenomenon: chugging events are characterized by pipe outside and pipe inside condensation. Pipe outside condensation is smooth, sometimes accompanied by vent pipe acoustic frequency. Pipe inside condensation is ring-like and induces a strong pressure pulse with ringdown frequency. The steam ring is caused by the retreating steam front in the pipe exit, which acts as a BORDA-mouth. (orig.)

249

Pressure effect on nitrogen boiling heat transfer in conditions of natural convection in an annular channel  

International Nuclear Information System (INIS)

The study is made of boiling heat transfer at natural convection of nitrogen in a vertical annular channel with the gap from 0.14 to 3.5 mm at pressures from 1.25x104 to 9x105 Pa. The data are obtained of the pressure effect on the boiling crisis characteristics and heat transfer coefficients. The relationship is established between the gap boundary value complying with the onset of the 'enhanced' heat transfer and the value of the bubble departure diameter for boiling of various liquids, such as nitrogen, helium, water, ethanol and freon

250

Influence of deformation conditions on texture formation and ductility in titanium alloys under hydrostatic pressure  

International Nuclear Information System (INIS)

The influence of hot pressing parameters on microstructure, texture and mechanical properties of bars from titanium alloys VT1-0, VT5-1, (?-alloys) and VT3-1 (?+?-alloy) has been investigated. Mechanical testing of samples has been performed under hydrostatic pressure from 200 to 800 MPa. It is shown that the temperature, deformation degree and type of the structure obtained exert a slight effect on mechanical properties of bars. The texture heterogeneity is more pronounced in ?-alloys. It has been found that hydrostatic pressure during sample tensile testing improves their ductility characteristics

251

Study on heat transfer and pressure drop characteristics of internal heat exchangers in CO2 system under cooling condition  

Science.gov (United States)

In order to study the heat transfer and pressure drop on four types of internal heat exchangers (IHXs) of a CO2 system, the experiment and numerical analysis were performed under a cooling condition. The configuration of the IHXs was a coaxial type and a micro-channel type. Two loops on the gas cooler part and the evaporator part were made, for experiment. And the section-by-section method and Hardy-Cross method were used for the numerical analysis. The capacity and pressure drop of the IHX are larger at the micro-channel type than at the coaxial type. When increasing the mass flow rate and the IHX length the capacity and pressure drop increase. The pressure drop of the evaporator loop is much larger than that of the gas cooler loop. The performance of the IHX was affected with operating condition of the gas-cooler and evaporator. The deviations between the experimental result and the numerical result are about ±20% for the micro-channel type and ±10% for the coaxial type. Thus, the new CO2 heat transfer correlation should be developed to precisely predict a CO2 heat transfer.

Kim, Dae Hoon; Lee, Jae-Heon; Choi, Jun Young; Kwon, Young Chul

2009-12-01

252

The effect of high pressure-high temperature processing conditions on acrylamide formation and other Maillard reaction compounds.  

Science.gov (United States)

The effect of high pressure-high temperature (HPHT) processing on the formation of acrylamide and other Maillard-type reaction compounds was investigated in order to elucidate the impact of HPHT conditions on the different stages of the Maillard reaction. This study was performed in equimolar asparagine-glucose model systems that were treated at various HP/HT conditions (100-115 °C, 400-700 MPa, 0-60 min), and, for comparison, the model system was also heat-treated at ambient pressure. On the treated samples, the concentration of acrylamide, reactants, hydroxymethylfurfural, organic acids, and melanoidins was determined and the pH prior to and after treatment was measured. Based on the measured responses, the retarding effect of high pressure on the overall Maillard reaction was demonstrated; no or little differences were observed between 400 and 700 MPa. The study was conducted in two types of buffer, i.e. phosphate and MES buffer. In case of acrylamide, aspartic acid and browning, a higher concentration was generated in the MES buffer system, but these differences with the phosphate buffer system could be ascribed to pH changes resulting from the application of combined high pressure and high temperature. Based on the results, acrylamide formation is not expected to pose a major hazard to HPHT-treated products. PMID:20973553

De Vleeschouwer, Kristel; Van der Plancken, Iesel; Van Loey, Ann; Hendrickx, Marc E

2010-11-24

253

Feasibility Study of PM Elimination by Silent Discharge Type of DPF under Room Temperature and Atmospheric Pressure Condition  

Science.gov (United States)

This Silent Discharge type of DPF (Diesel Particulate Filter) has been studied for eliminating PM (Particulate Mater) we call it “SDeDPF”. Usually, exhaust gas temperature of diesel engines is under 200 or 250°C at normal city driving condition. Under that condition, generally PM is not bourn out in the normal ceramic DPF. This SDeDPF aims to remove PM electrically and chemically even at room temperature and atmospheric pressure continuously. Finally, in the basic lab test result, 95.6% reduction of PM has been verified by SDeDPF with a special MFS (Metal Fiber Sheet) for discharge electrode to reduce a back pressure, a special Turbulent Block for turbulent and slower velocity of exhaust gas, the 1mm gap between electrodes and an optimum total area of piled electrodes. Also, 98.1% reduction of PM could be designed by most suitable gap between electrodes.

Chuubachi, Minoru; Nagasawa, Takeshi

254

Experimental study on transient void behavior in subcooled water during reactivity initiated accidents under low pressure conditions  

International Nuclear Information System (INIS)

A series of experiments for fast transient void behaviors during reactivity initiated accidents has been performed with a single simulated fuel rod under the atmospheric pressure condition. A fast-response impedance technique was applied for void fraction measurement. The comparison between the impedance and x-ray techniques indicated that the difference between both techniques was within the allowable range of accuracy for fast transient conditions. Experimental database were obtained, including the onset timing of net vapor generation, local void fraction, water temperature and pressure. The Saha and Zuber model overestimated the experimentally obtained local water subcooling at the onset of net vapor generation. The inlet water subcooling largely influenced the variation of local void fraction. In the case with larger inlet water subcooling, grow and collapse by condensation of voids was repeatedly observed, which suppressed a continuous increase in local void fraction. (authors)

255

A Barometric Survey of Dust-Devil Vortices on a Desert Playa  

Science.gov (United States)

Dust devils, and other columnar vortices, are associated with local surface pressure drops that can be observed in time-series data on both Earth and Mars. High cadence measurements are needed to resolve these small structures, and we report a month-long survey (June/July 2012) on a Nevada desert playa using microbarographs sampled multiple times per second. Candidate dust-devil signatures are classified, with detections being robust at about one per day for pressure drops exceeding 0.3 hPa (roughly a 5:1 signal-to-noise threshold, where the observed noise level corresponds reasonably well with the dynamic pressure associated with the estimate convective velocity scale). The vortex population is evaluated and compared with those observed on Mars: a broken power law or a more convex distribution describes the terrestrial data. A single station observes about three events per week (for normalized pressure drops of 0.06 %), about three times fewer than Mars observations for the same normalized drop. We find evidence for clustering of vortex events in a pseudo-periodic manner with a 20-min period, consistent with the size of boundary-layer convection cells.

Lorenz, Ralph D.; Lanagan, Peter D.

2014-12-01

256

Experimental study of centrifugal pump performance under steam-water two-phase flow conditions at elevated pressures  

International Nuclear Information System (INIS)

The performance of a centrifugal pump under two-phase flow conditions was studied in a closed loop. System voids of increasing magnitude were attained by draining water from the loop in steps. The operating temperature/pressure were varied from 110 degrees C/0.15 MPa to 260 degrees C/4.7 MPa. Only tests in the first quadrant were conducted. In this paper the head-flow characteristics and pump head degradation data are presented and discussed

257

The application of the Buckingham theorem to modeling high-pressure regenerative heat exchangers in changed conditions  

OpenAIRE

Abstract The study presents the possibility of applying the Buckingham theorem to modeling high-pressure regenerative heat exchangers in changed conditions. A list of independent parameters on which the water temperature at the outlet of the heat exchanger depends was selected; and by means of the Buckingham theorem a functional relation between two dimensionless quantities, where there is no overall heat transfer coefficient, was obtained. The exact form of the function was determined on the...

Rafal Marcin Laskowski

2011-01-01

258

Seed storage at elevated partial pressure of oxygen, a fast method for analysing seed ageing under dry conditions  

OpenAIRE

Background and Aims Despite differences in physiology between dry and relative moist seeds, seed ageing tests most often use a temperature and seed moisture level that are higher than during dry storage used in commercial practice and gene banks. This study aimed to test whether seed ageing under dry conditions can be accelerated by storing under high-pressure oxygen. Methods Dry barley (Hordeum vulgare), cabbage (Brassica oleracea), lettuce (Lactuca sativa) and soybean (Glycine max) seeds w...

Groot, S. P. C.; Surki, A. A.; Vos, R. C. H.; Kodde, J.

2012-01-01

259

Aluminum oxide films deposited in low pressure conditions by reactive pulsed dc magnetron sputtering  

CERN Document Server

The reactive pulsed dc sputtering technique is widely used for the deposition of oxide films. The operating pressure for sputtering is commonly above 0.13 Pa. In this study, however, aluminum oxide (alumina) films were deposited at operating pressures from 0.06 to 0.4 Pa using a sputtering system equipped with a scanning magnetron cathode and a pulsed dc power supply. The pulsed dc power was found to be useful not only to reduce arcing, but also to sustain the discharge at low pressure. The electrical breakdown field, intrinsic stress, O/Al ratio, refractive index, and surface roughness were investigated. Both a low intrinsic stress and an O/Al ratio around the stoichiometry were required to get the film having a high breakdown field. A low operating pressure of 0.1 Pa was found to provide the necessary stress and O/Al ratio targets. A 50-nm-thick alumina film having a maximum breakdown field of 7.4 MV/cm was obtained.

Seino, T

2002-01-01

260

RCS pressure under reduced inventory conditions following a loss of residual heat removal  

International Nuclear Information System (INIS)

The thermal-hydraulic response of a closed-reactor coolant system to loss of residual heat removal (RHR) cooling is investigated. The processes examined include: core coolant boiling and steam generator reflux condensation, pressure increase on the primary side, heat transfer mechanisms on the steam generator primary and secondary sides, and effects of noncondensible gas on heat transfer processes

261

Experimental investigation of sagging of a completely voided pressure tube of Indian PHWR under heatup condition  

International Nuclear Information System (INIS)

Pressure tube (zirconium 2.5 wt.% Nb) serves as a pressure boundary for the coolant that removes nuclear heat generated in the reactor core of Indian Pressurised Heavy Water Reactors (IPHWRs). Under postulated low frequency (-6 per year) accidents like Loss of Coolant Accident (LOCA) along with failure of Emergency Core Cooling System (ECCS) injection, heatup of pressure tube (PT) combined with internal pressure and the weight of the fuel bundle may lead to deformation. The extent and nature of deformation is important from reactor safety point of view. An experimental set-up has been designed and fabricated to simulate sagging (downward deformation) of PT due to its own weight and the weight of fuel bundles for 220 MWe IPHWRs. Experiments are conducted at different heatup rates of voided PTs. It is observed that sagging initiates at a temperature around 450 oC. Contact between PT and calandria tube (CT) occurs at around 585-625 oC, respectively. Once PT-CT contact takes place, PT temperature either decreases or the temperature rise remains controlled whereas CT temperature keeps on increasing for next 20-30 s. The contact location in all the experiments was near the centre of the tube. Structural integrity of PT is retained (no breach) for all the experiments. The PT temperature rise is found to be arrested after the contact between PT and CT, thus establishing that moderator acts as an efficient heat sink for IPHWRs.icient heat sink for IPHWRs.

262

Elemental and isotope behaviour at ultra-high pressure (UHP) conditions: Earth and Environment  

SCPinfonet

... Therse rocks contain extremely light Li isotope ratios (bulk rocks, garnets and omphacite) and are with very radiogenic Os and Sr isotope signatures. We now investigate the elemental and isotopic influence that the host gneiss may play in shaping the geochemistry of the high pressure eclogite lenses and layers. Collaborators: & nbsp ...

263

Steel surface structure under condition of condensate circuits of supercritical pressure power units and one-loop NPP  

International Nuclear Information System (INIS)

The surface structure of specimens of steel-20 and steel-08Kh14MF has been studied following the corrosion testing under the conditions of condensate circuits of a one-loop NPP for the purpose of replacing steel-08Kh18N10T used for low pressure heaters (LPH). The formation of a protective oxide film of fine crystals on the surface is revealed its continuity and protective properties increasing with the testing temperature. The conclusion is drawn on the possible and abvisable replacement of steel-08Kh18NI0T by steel-08Kh14MF in the course of the circuit operation under neutral oxidizing water conditions

264

Experimental investigations of BWR pressure suppression pool behavior under loss of coolant accident conditions  

International Nuclear Information System (INIS)

The experiments discussed in this paper look into different processes which may occur during a loss-of-coolant accident in the pressure suppression pool of a Boiling Water Reactor (BWR). These processes include: a) development of a thermal stratification, b) bubble dynamics and related water flow during continuous release of air and c) air blowdown and associated water slug phenomenon in the water pool. The experiments have been performed in the THAI test facility, which is a cylindrical vessel of 9.2 m height, 3.2 m diameter and with a gas volume of 60 m3. The variation in the investigated test parameters included, steam and air mass flux, initial water pool temperature, blowdown pressures, downcomer submergence, etc. A systematic variation of the test parameters allowed better understanding of the phenomena. Experiments discussed in this paper were performed with a vertical downcomer of 0.1 m diameter and 2 m submergence depth in the water pool. For the blowdown experiments, a separate interconnecting vessel of 1 m3 volume was used to inject air at pressures between 3 bar and 10 bar. A high speed camera (1000 fps) was installed to visualize the formation and propagation of air bubbles in the suppression pool and the resulting pool swelling phenomena. Customized instrumentation applied during the tests included grids of densely spaced thermocouples and of pressure transducers at various locations in order to capture the temperature distribution r to capture the temperature distribution in the pool and the water slug induced pressure loadings, respectively. The present paper discusses the main outcome of the selected experiments. On the whole the experimental data may be very useful for code validation. (authors)

265

Boundary-Layer Separation Control under Low-Pressure Turbine Airfoil Conditions using Glow-Discharge Plasma Actuators  

Science.gov (United States)

Modem low-pressure turbines, in general, utilize highly loaded airfoils in an effort to improve efficiency and to lower the number of airfoils needed. Typically, the airfoil boundary layers are turbulent and fully attached at takeoff conditions, whereas a substantial fraction of the boundary layers on the airfoils may be transitional at cruise conditions due to the change of density with altitude. The strong adverse pressure gradients on the suction side of these airfoils can lead to boundary-layer separation at the latter low Reynolds number conditions. Large separation bubbles, particularly those which fail to reattach, cause a significant degradation of engine efficiency. A component efficiency drop of the order 2% may occur between takeoff and cruise conditions for large commercial transport engines and could be as large as 7% for smaller engines at higher altitude. An efficient means of of separation elimination/reduction is, therefore, crucial to improved turbine design. Because the large change in the Reynolds number from takeoff to cruise leads to a distinct change in the airfoil flow physics, a separation control strategy intended for cruise conditions will need to be carefully constructed so as to incur minimum impact/penalty at takeoff. A complicating factor, but also a potential advantage in the quest for an efficient strategy, is the intricate interplay between separation and transition for the situation at hand. Volino gives a comprehensive discussion of several recent studies on transition and separation under low-pressure-turbine conditions, among them one in the present facility. Transition may begin before or after separation, depending on the Reynolds number and other flow conditions. If the transition occurs early in the boundary layer then separation may be reduced or completely eliminated. Transition in the shear layer of a separation bubble can lead to rapid reattachment. This suggests using control mechanisms to trigger and enhance early transition. Gad-el-Hak provides a review of various techniques for flow control in general and Volino discusses recent studies on separation control under low-pressure-turbine conditions utilizing passive as well as active devices. As pointed out by Volino, passive devices optimized for separation control at low Reynolds numbers tend to increase losses at high Reynolds numbers, Active devices have the attractive feature that they can be utilized only in operational regimes where they are needed and when turned off would not affect the flow. The focus in the present paper is an experimental Separation is induced on a flat plate installed in a closed-circuit wind tunnel by a shaped insert on the opposite wall. The flow conditions represent flow over the suction surface of a modem low-pressure-turbine airfoil ('Pak-B'). The Reynolds number, based on wetted plate length and nominal exit velocity, is varied from 50,000 to 300,000, covering cruise to takeoff conditions. Low (0.2%) and high (2.5%) Gee-stream turbulence intensities are set using passive grids. A spanwise-oriented phased-plasma-array actuator, fabricated on a printed circuit board, is surface- flush-mounted upstream of the separation point and can provide forcing in a wide frequency range. Static surface pressure measurements and hot-wire anemometry of the base and controlled flows are performed and indicate that the glow-discharge plasma actuator is an effective device for separation control. of active separation control using glow discharge plasma actuators.

Hultgren, Lennart S.; Ashpis, David E.

2003-01-01

266

Study of ballooning of a completely voided pressure tube of Indian PHWR under heat up condition  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer Simulating of LOCA at 4 and 6 MPa internal pressures for IPHWR was carried out at IIT Roorkee, India. Black-Right-Pointing-Pointer The sagging of PT takes place at 500 Degree-Sign C before the commencement of ballooning. Maximum sagging is less than 2 mm. Black-Right-Pointing-Pointer Once PT touches the CT, there is no further rise in PT temperature. Black-Right-Pointing-Pointer The maximum PT temperature was below 700 Degree-Sign C. Black-Right-Pointing-Pointer The transverse creep correlation for CANDU material also holds good for Indian PT material for the temperature range expected during LOCA. - Abstract: In a nuclear reactor, loss of coolant accident (LOCA) considers wide range of postulated damage or rupture of pipe in the heat transport piping system. In case of LOCA with/without failure of emergency core cooling system in a Pressurized Heavy Water Reactor, the pressure tube (PT) temperature can rise significantly due to fuel heat up and gross mismatch of heat generation and heat removal in the affected channel. The extent and nature of deformation is important from reactor safety point of view. Experimental set-ups have been designed and fabricated to simulate ballooning (radial deformation) of PT for 220 MWe IPHWRs. Experiments have been conducted using voided PTs at 4 and 6 MPa internal pressure at different heating rates. It is observed that at 4 MPa and 6 MPa internal pressure, the PT sagged at about 500 Degree-Sign C before the ballooning initiation. The ballooning initiates at a temperature around 625 Degree-Sign C and contact between PT and Calandria Tube (CT) occurs at around 680 Degree-Sign C, respectively, for 4 MPa and the same was at 550 Degree-Sign C and 640 Degree-Sign C for 6 MPa. The structural integrity of PT is retained (no breach) for all the experiments. The PT heat up is found to be arrested after the contact between PT and CT, thus establishing the moderator acting as an efficient heat sink for IPHWRs. A thermal creep model 'PTCREEP' has been developed to predict creep behaviour of the PT of IPHWR. It is found that the contact time predicted by PTCREEP is very close to the experimental result. Hence, PTCREEP can be used for the prediction of the ballooning behaviour of the PT for IPHWR in case of LOCA for the operating temperature and pressure range.

Nandan, Gopal [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee (India); Majumdar, P. [Reactor Safety Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India); Sahoo, P.K., E-mail: sahoofme@iitr.ernet.in [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee (India); Kumar, Ravi [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee (India); Chatterjee, B.; Mukhopadhyay, D.; Lele, H.G. [Reactor Safety Division, Bhabha Atomic Research Centre, Trombay, Mumbai (India)

2012-02-15

267

Abiogenic hydrocarbons produced under upper-mantle pressure-temperature conditions  

Science.gov (United States)

There are growing evidences for abiogenic pathways of the petroleum production in the deep Earth. The laboratory experiments under extreme pressures and temperatures provide direct information about the chemical reactivity and stability of the natural oil components. Here we present new results on formation of hydrocarbons at high pressures and temperatures generated in diamond anvil cells (DAC). We use in situ Raman spectroscopy in laser heated diamond anvil cells to monitor the chemical reactivity; Raman spectroscopy and synchrotron x-ray diffraction are used to determine the reaction products quenched to ambient temperature. We have explored chemical reactions in the system consisting of CaCO3-H2O with either of the following mantle minerals: San Carlos olivine, peridodite, and Rockport fayalite. We also studied chemical reactivity of methane and ethane to explore possible routes to generate heavier hydrocarbons. The pressure range of the experiments (3-6 GPa) are similar to those studied by Kenney et al. [1] and Scott et al. [2] but temperatures up to 2500 K were generated. At pressures in the 5-6 GPa range, methanogenesis was observed in the olivine-calcite-water, fayalite-calcite-water system at temperatures greater than 2300 K and less than 800 K, respectively. We find that methane at 2-5 GPa and 1000-1500 K partially reacts and forms saturated hydrocarbons (C2-C4alkanes), molecular hydrogen and graphite. Formation of methane in similar experiments on ethane suggests reversibility of hydrocarbon formation. These results support proposals of abiogenic pathways for the formation of hydrocarbons in the Earth's upper mantle. 1 Kenney, J. F., Kutcherov, V. G., Bendeliani, N. A. & Alekseev, V. A. The Evolution of Multicomponent Systems at High Pressures: VI. The Thermodynamic Stability of the Hydrogen-Carbon System: The Genesis of Hydrocarbons and the Origin of Petroleum. Proc. Natl. Acad. Sci. U.S.A. 99, 10976-10981 (2002). 2 Scott, H.P., Hemley, R.J., Mao, H-K., Herschbach, D.R., Fried, L.E., Howard, W.M., and Bastea, S. Generation of methane in the Earth's mantle: In situ high pressure-temperature measurements of carbonate reduction, Proc. Nat. Acad. Sci. 39, 14023-14026 (2004).

Goncharov, Alexander F.; Chellappa, Raja S.; Kolesnikov, Anton; Somayazulu, Maddury; Kutcherov, Vladimir G.; Hemley, Russell J.

2010-05-01

268

Effect of hydrostatic pressure on n-type negative differential conduction in conditions of magnetoconcentration effect  

International Nuclear Information System (INIS)

Results of investigations into comprehensive compression effect on the parameters n-type negative differential conductivity (N-NDC) occuring under magnetoconcentrational effect (MCE), and high-frequency (HF) current oscillations in InSb accompanying it are presented. It is supposed that the described regularities in indium antimonide crystal VAC behaviour under comprehensive compression can be explained by a change of nitriusic current carrier concentration in a crystal with pressure and of the most important carrier parameters (lifetime, diffusion, recombination mechanism). The results presented testify to the universal character of H-NDC nature under crossed E and H fields. From the practical viewpoint the results can be applied for control of hydrostatic pressure value, l.g. by degree of harmonicity of HF oscillations or by their frequency

269

Reduced herbivore pressure under rainy ENSO conditions could facilitate dryland reforestation  

OpenAIRE

Most semi-arid and arid regions around the world have lost a major part of their original vegetation. Restoration of once shrublands and woodlands is often challenged by low seedling establishment success due to water stress and herbivory. In some regions, increased rainfall during El Niño Southern Oscillation (ENSO) events can significantly stimulate plant recruitment. However, recruitment seems to be strongly modulated by herbivore pressure. Also, seedling establishment in arid ecosystems ...

Gutierrez, J. R.; Holmgren, M.; Manrique, R.; Squeo, F. A.

2007-01-01

270

Turbulence Sets the Initial Conditions for Star Formation in High-pressure Environments  

Science.gov (United States)

Despite the simplicity of theoretical models of supersonically turbulent, isothermal media, their predictions successfully match the observed gas structure and star formation activity within low-pressure (P/k 107 K cm-3) environments, like those in the Galaxy's inner 200 pc central molecular zone (CMZ) and in the early universe. Here, we present Atacama Large Millimeter/submillimeter Array 3 mm dust continuum emission within a cloud, G0.253+0.016, which is immersed in the high-pressure environment of the CMZ. While the log-normal shape and dispersion of its column density probability distribution function (PDF) are strikingly similar to those of solar neighborhood clouds, there is one important quantitative difference: its mean column density is one to two orders of magnitude higher. Both the similarity and difference in the PDF compared to those derived from solar neighborhood clouds match predictions of turbulent cloud models given the high-pressure environment of the CMZ. The PDF shows a small deviation from log-normal at high column densities confirming the youth of G0.253+0.016. Its lack of star formation is consistent with the theoretically predicted, environmentally dependent volume density threshold for star formation which is orders of magnitude higher than that derived for solar neighborhood clouds. Our results provide the first empirical evidence that the current theoretical understanding of molecular cloud structure derived from the solar neighborhood also holds in high-pressure environments. We therefore suggest that these theories may be applicable to understand star formation in the early universe.

Rathborne, J. M.; Longmore, S. N.; Jackson, J. M.; Kruijssen, J. M. D.; Alves, J. F.; Bally, J.; Bastian, N.; Contreras, Y.; Foster, J. B.; Garay, G.; Testi, L.; Walsh, A. J.

2014-11-01

271

Land use change under conditions of high population pressure : the case of Java  

OpenAIRE

A long history of increases in population pressure in Java has caused agricultural land use to expand and intensify. More recent land use changes caused the conversion of prime agricultural land into residential and industrial area. Results of a dynamic, regional-scale, land use change model are presented, defining the spatial distribution of these land use changes. The model is based on multi-scale modelling of the relations between land use and socio-economic and biophysical determinants. H...

Verburg, P. H.; Veldkamp, A.; Bouma, J.

1999-01-01

272

Heat and mass transfer modelling of sub-micrometer droplets under atmospheric pressure conditions  

OpenAIRE

The mathematical modeling of heat and mass transfers of submicrometer droplets vaporizing in gaseous surroundings at atmospheric pressure is investigated, including the effect of equilibrium/nonequilibrium assumption at the liquid/gas interface and of surface curvature on the droplet evaporation behavior. The numerical limitations of some of the most frequently used models for academic and industrial research activities on sprays have been enlightened. Emphasis is given to the verification of...

Tonini, Simona

2009-01-01

273

Acrylic resin water sorption under different pressure, temperature and time conditions  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of this work was to analyze water sorption by polymerized acrylic resins under different pressure, temperature and time treatments. A thermo-cured acrylic resin was used as the denture base (Classico Ltda. and ethylene glycol di-methacrylate as a cross-linking agent, with processing carried out in a water bath at 73 °C for nine hours. Forty-five samples were prepared following the criteria and dimensions of specification # 12 of the American Dental Association (ADA, using a matrix in the shape of a stainless steel disc with 50 ± 1 mm diameter and 0.5 ± 0.05 mm thickness. The control group samples were stored in distilled water for 30 days, while groups GII to GIX were placed in a polymerization device with adjustable pressure, time and temperature. An analysis of the variance of the results revealed the influence of different factors on water sorption only, with significant factors being temperature, time, pressure and the interaction between time and temperature. Other interactions exerted no significant influence on water sorption. Neither additional treatments nor the control group (GI showed any significant difference in comparison to the averages of other treatments.

Célia Marisa Rizzatti-Barbosa

2001-01-01

274

Two boil-off patterns in rod bundles under high-pressure conditions  

International Nuclear Information System (INIS)

It is believed that the nuclear core or steam generator tube bundle becomes partially uncovered due to transient boil-off during a small-break loss-of-coolant accident. In the boil-off, the water inventory in the nuclear core or the steam generator boiling section decreases due to the effluent steam or water. Existing studies have focused on the boil-off experiments in low bundle powers at system pressures from 0.7 to 7.5 MPa. The boil-off experiments in a wide range of bundle powers at system pressures from 3.1 to 11.9 MPa were conducted by using the Two-Phase Flow Test Facility (TPTF). The paper presents a schematic of boil-off patterns in the high or low bundle power considered in the present study. The high and low power boil-off patterns are observed in the TPTF high-pressure boil-off experiments. The difference between the two patterns is considered to be due to the slug-to-annular-flow transition as explained with the present transition model

275

Turbulence sets the initial conditions for star formation in high-pressure environments  

CERN Document Server

Despite the simplicity of theoretical models of supersonically turbulent, isothermal media, their predictions successfully match the observed gas structure and star formation activity within low-pressure (P/k 10^7 K cm^-3) environments, like those in the Galaxy's inner 200 pc Central Molecular Zone (CMZ) and in the early Universe. Here we present ALMA 3mm dust continuum emission within a cloud, G0.253+0.016, which is immersed in the high-pressure environment of the CMZ. While the log-normal shape and dispersion of its column density PDF is strikingly similar to those of solar neighbourhood clouds, there is one important quantitative difference: its mean column density is 1--2 orders of magnitude higher. Both the similarity and difference in the PDF compared to those derived from solar neighbourhood clouds match predictions of turbulent cloud models given the high-pressure environment of the CMZ. The PDF shows a small deviation from log-normal at high column densities confirming the youth of G0.253+0.016. Its...

Rathborne, J M; Jackson, J M; Kruijssen, J M D; Alves, J F; Bally, J; Bastian, N; Contreras, Y; Foster, J B; Garay, G; Testi, L; Walsh, A J

2014-01-01

276

Acrylic resin water sorption under different pressure, temperature and time conditions  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The purpose of this work was to analyze water sorption by polymerized acrylic resins under different pressure, temperature and time treatments. A thermo-cured acrylic resin was used as the denture base (Classico Ltda.) and ethylene glycol di-methacrylate as a cross-linking agent, with processing car [...] ried out in a water bath at 73 °C for nine hours. Forty-five samples were prepared following the criteria and dimensions of specification # 12 of the American Dental Association (ADA), using a matrix in the shape of a stainless steel disc with 50 ± 1 mm diameter and 0.5 ± 0.05 mm thickness. The control group samples were stored in distilled water for 30 days, while groups GII to GIX were placed in a polymerization device with adjustable pressure, time and temperature. An analysis of the variance of the results revealed the influence of different factors on water sorption only, with significant factors being temperature, time, pressure and the interaction between time and temperature. Other interactions exerted no significant influence on water sorption. Neither additional treatments nor the control group (GI) showed any significant difference in comparison to the averages of other treatments.

Célia Marisa, Rizzatti-Barbosa; Marco Aurélio, Fraga; Tarcísio de Moraes, Gonçalves.

2001-01-01

277

Microstructural studies on steam oxidised Zr-2.5%Nb pressure tube under simulated LOCA condition  

International Nuclear Information System (INIS)

Study of the microstructural evolution of Zr-2.5%Nb pressure tube material of Indian Pressurized Heavy Water Reactors (PHWRs) due to steam oxidation at high temperature (in the range 500-1050°C) was carried out on pressure tube coupons. Hydrogen pick up was less than 55 ppm in the samples oxidized at temperatures up to 850°C but high (250-400 ppm) in the samples oxidized in the ? phase region (900°C and above). The microstructure of the samples oxidized above the ?-Zr/?-Zr transition temperature showed from the surface inwards sequentially the presence of an oxide layer, an underlying oxygen stabilized ?-Zr layer and a prior ?-Zr phase containing hydride precipitates. An increase in the hardness was observed near the oxide-metal interface in the coupons oxidized above 900°C, due to formation of oxygen stabilized ?-Zr layer. Higher hardness was also observed in the base metal in the samples oxidized at 1000 and 1050°C (author)

278

Heat Flux Measurement of Re-Entry Capsule Models under High-Enthalpy High-Pressure Condition  

Science.gov (United States)

Aerodynamic heating test with re-entry capsule configuration in hypersonic high-enthalpy flow has conducted in JAXA-HIEST. An Apollo CM 6.4% scale model has applied in the test, which model has used in the previous test campaign conducted in FY2009. Aerodynamic heating characteristics were observed at model angle-of-attack of the model was fixed at 0 degree. The model had 84 miniature fast response coaxial thermocouples on the windward to see the heat flux distribution. Eight miniature thermocouples and two Piezoresistive pressure transducers were also mounted aft on the model and were used to determine the establishment of flow around the model. In the present test campaign abnormally high heat-flux phenomenon was focused, which phenomenon was observed under stagnation enthalpy H0 over 17MJ/kg and stagnation pressure P0 over 45MPa in the last test campaign. To observe gas composition effect on the phenomenon, measurements with air and pure nitrogen test gas under same flow condition were performed. Stagnation enthalpy and stagnation pressure were varied from H0=3.4MJ/kg to 21MJ/kg, and from P0=11MPa to 58MPa, respectively. The unit Reynolds number under the condition was 0.9million/m to 5.2million/m and the boundary layer was hence mainly fully laminar flow. Measured heat flux was normalized by the product of the Stanton number and the square- root of the Reynolds number for correlation with other wind tunnel results and numerical results. The measurement showed that the abnormal heat flux was increased as stagnation enthalpy and there was no difference between air test gas and pure nitrogen test gas. It should be noted that particles caused by low- pressure diaphragm debris under low enthalpy condition or nozzle throat crack may cause remarkable heat flux increase.

Tanno, H.; Sato, K.; Komuro, T.; Takahashi, M.; Itoh, K.; Ishihara, T.; Ogino, Y.; Sawada, K.

2011-08-01

279

Pressure measurements and high speed visualizations of the cavitation phenomena at deep part load condition in a Francis turbine  

Science.gov (United States)

In a hydraulic power plant, it is essential to provide a reliable, sustainable and flexible energy supply. In recent years, in order to cover the variations of the renewable electricity production, hydraulic power plants are demanded to operate with more extended operating range. Under these off-design conditions, a hydraulic turbine is subject to cavitating swirl flow at the runner outlet. It is well-known that the helically/symmetrically shaped cavitation develops at the runner outlet in part load/full load condition, and it gives severe damage to the hydraulic systems under certain conditions. Although there have been many studies about partial and full load conditions, contributions reporting the deep part load condition are limited, and the cavitation behaviour at this condition is not yet understood. This study aims to unveil the cavitation phenomena at deep part load condition by high speed visualizations focusing on the draft tube cone as well as the runner blade channel, and pressure fluctuations associated with the phenomena were also investigated.

Yamamoto, K.; Müller, A.; Favrel, A.; Landry, C.; Avellan, F.

2014-12-01

280

Single-phase natural circulation in pressurized water reactor under degraded secondary cooling conditions  

International Nuclear Information System (INIS)

In this paper the thermal-hydraulic behavior of inverted-U-Tube steam generator during single-phase natural circulation in a pressurized water reactor is characterized by non-uniform flow distribution among the U-tubes. This results from gravity effects on low-velocity liquid flow through multiple cooling channels. The influence of the secondary-side water level on the tube flow behavior was studied experimentally using a large scale simulator. The experiment indicated the existence of an oscillatory flow mode. This mode appeared when the U-tube external surface was uncovered extensively creating a vertically-stratified temperature distribution in the secondary-side vapor space

281

Investigation of nitrogen tetroxide n,?-radiolysis under temperature and pressure supercritical conditions  

International Nuclear Information System (INIS)

With the help of the ampoule facility in the field of the reactor mixed n, ?-radiation in the range of temperatures 200-350 deg C, pressures 7.8-15.7 MPa and dose rates 50-160 W/kg the formation yields of irreversible radiolysis products of dissociating nitrogen tetroxide (nitrogen and nitrous oxide) are determined. On the basis of the analysis of the data existing in the literature and the data obtained it has been concluded that nitrogen tetroxide molecules and NO2 manifest themselves as molecules with identical properties when investigating their contribution into nitrogen and nitrous oxide formation in radiolysis

282

Evaluation of hydraulic and mechanical properties of Berea sandstone under different conditions of temperature and confining pressure  

International Nuclear Information System (INIS)

The isotropic compression experiments using Berea sandstone were conducted under the different temperature and confining pressure conditions, and the evolutions of hydraulic and mechanical properties were observed. The temperatures and confining pressures prescribed for the experiments are 20 and 90degC, and 7.5 or 8.0 MPa, respectively. The observed permeability at 20degC did not significantly evolve during the experiment period, while that at 90degC decreased by roughly 20% relative to the original value. This reduction may be attributed to the change of pore-structure induced by mineral dissolution and/or precipitation. Unlikely, the uniaxial compression tests showed no obvious change observed between pre- and post-experimental results. The XRD observation also showed no significant difference of mineralogy between them. (author)

283

The application of the Buckingham theorem to modeling high-pressure regenerative heat exchangers in changed conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract The study presents the possibility of applying the Buckingham theorem to modeling high-pressure regenerative heat exchangers in changed conditions. A list of independent parameters on which the water temperature at the outlet of the heat exchanger depends was selected; and by means of the Buckingham theorem a functional relation between two dimensionless quantities, where there is no overall heat transfer coefficient, was obtained. The exact form of the function was determined on the basis of actual measurement data and a linear relation between two dimensionless quantities was obtained. The correctness of the proposed relation was examined for two high-pressure regenerative exchangers for a 200 MW power plant.

Rafal Marcin Laskowski

2011-01-01

284

Experimental investigation of supersonic low pressure air plasma flows obtained with different arc-jet operating conditions  

International Nuclear Information System (INIS)

A stationary arc-jet plasma flow at low pressure is used to simulate some properties of the gas flow surrounding a vehicle during its entry into celestial body's atmospheres. This paper presents an experimental study concerning plasmas simulating a re-entry into our planet. Optical measurements have been carried out for several operating plasma conditions in the free stream, and in the shock layer formed in front of a flat cylindrical plate, placed in the plasma jet. The analysis of the spectral radiation enabled the identification of the emitting species, the determination of the rotational and vibrational temperatures in the free-stream and in the shock layer and the determination of the distance of the shock to the flat plate face. Some plasma fluid parameters like, stagnation pressure, specific enthalpy and heat flux have been determined experimentally along the plasma-jet axis.

285

Creep failure of a reactor pressure vessel lower head under severe accident conditions  

International Nuclear Information System (INIS)

A severe accident in a nuclear power plant could result in the relocation of large quantities of molten core material onto the lower head of he reactor pressure vessel (RPV). In the absence of inherent cooling mechanisms, failure of the RPV ultimately becomes possible under the combined effects of system pressure and the thermal heat-up of the lower head. Sandia National Laboratories has performed seven experiments at 1:5th scale simulating creep failure of a RPV lower head. This paper describes a modeling program that complements the experimental program. Analyses have been performed using the general-purpose finite-element code ABAQUS-5.6. In order to make ABAQUS solve the specific problem at hand, a material constitutive model that utilizes temperature dependent properties has been developed and attached to ABAQUS-executable through its UMAT utility. Analyses of the LHF-1 experiment predict instability-type failure. Predicted strains are delayed relative to the observed strain histories. Parametric variations on either the yield stress, creep rate, or both (within the range of material property data) can bring predictions into agreement with experiment. The analysis indicates that it is necessary to conduct material property tests on the actual material used in the experimental program. The constitutive model employed in the present analyses is the subject of a separate publication

286

Creep failure of a reactor pressure vessel lower head under severe accident conditions  

Energy Technology Data Exchange (ETDEWEB)

A severe accident in a nuclear power plant could result in the relocation of large quantities of molten core material onto the lower head of he reactor pressure vessel (RPV). In the absence of inherent cooling mechanisms, failure of the RPV ultimately becomes possible under the combined effects of system pressure and the thermal heat-up of the lower head. Sandia National Laboratories has performed seven experiments at 1:5th scale simulating creep failure of a RPV lower head. This paper describes a modeling program that complements the experimental program. Analyses have been performed using the general-purpose finite-element code ABAQUS-5.6. In order to make ABAQUS solve the specific problem at hand, a material constitutive model that utilizes temperature dependent properties has been developed and attached to ABAQUS-executable through its UMAT utility. Analyses of the LHF-1 experiment predict instability-type failure. Predicted strains are delayed relative to the observed strain histories. Parametric variations on either the yield stress, creep rate, or both (within the range of material property data) can bring predictions into agreement with experiment. The analysis indicates that it is necessary to conduct material property tests on the actual material used in the experimental program. The constitutive model employed in the present analyses is the subject of a separate publication.

Pilch, M.M.; Ludwigsen, J.S.; Chu, T.Y. [Sandia National Labs., Albuquerque, NM (United States); Rashid, Y.R. [Anatech, San Diego, CA (United States)

1998-08-01

287

Predictions of Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions Using an Intermittency Transport Equation  

Science.gov (United States)

A new transport equation for the intermittency factor was proposed to predict separated and transitional boundary layers under low-pressure turbine airfoil conditions. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, t , with the intermittency factor, y. Turbulent quantities are predicted by using Menter s two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model, which not only can reproduce the experimentally observed streamwise variation of the intermittency in the transition zone, but also can provide a realistic cross-stream variation of the intermittency profile. In this paper, the intermittency model is used to predict a recent separated and transitional boundary layer experiment under low pressure turbine airfoil conditions. The experiment provides detailed measurements of velocity, turbulent kinetic energy and intermittency profiles for a number of Reynolds numbers and freestream turbulent intensity conditions and is suitable for validation purposes. Detailed comparisons of computational results with experimental data are presented and good agreements between the experiments and predictions are obtained.

Suzen, Y. B.; Huang, P. G.; Hultgren, Lennart S.; Ashpis, David E.

2003-01-01

288

A compact and automated ex vivo vessel culture system for the pulsatile pressure conditioning of human saphenous veins.  

Science.gov (United States)

Saphenous vein (SV) graft disease represents an unresolved problem in coronary artery bypass grafting (CABG). After CABG, a progressive remodelling of the SV wall occurs, possibly leading to occlusion of the lumen, a process termed 'intima hyperplasia' (IH). The investigation of cellular and molecular aspects of IH progression is a primary end-point toward the generation of occlusion-free vessels that may be used as 'life-long' grafts. While animal transplantation models have clarified some of the remodelling factors, the pathology of human SV is far from being understood. This is also due to the lack of devices able to reproduce the altered mechanical load encountered by the SV after CABG. This article describes the design of a novel ex vivo vein culture system (EVCS) capable of replicating the altered pressure pattern experienced by SV after CABG, and reports the results of a preliminary biomechanical conditioning experimental campaign on SV segments. The EVCS applied a CAGB-like pressure (80-120?mmHg) or a venous-like perfusion (3?ml/min, 5?mmHg) conditioning to the SVs, keeping the segments viable in a sterile environment during 7?day culture experiments. After CABG-like pressure conditioning, SVs exhibited a decay of the wall thickness, an enlargement of the luminal perimeter, a rearrangement of the muscle fibres and partial denudation of the endothelium. Considering these preliminary results, the EVCS is a suitable system to study the mechanical attributes of SV graft disease, and its use, combined with a well-designed biological protocol, may be of help in elucidating the cellular and molecular mechanisms involved in SV graft disease. Copyright © 2013 John Wiley & Sons, Ltd. PMID:23897837

Piola, Marco; Prandi, Francesca; Bono, Nina; Soncini, Monica; Penza, Eleonora; Agrifoglio, Marco; Polvani, Gianluca; Pesce, Maurizio; Fiore, Gianfranco Beniamino

2013-07-30

289

Behavior of Self-Lubricated Liquids Under Normal and Reduced-Pressure Conditions  

Science.gov (United States)

We explore the behavior of liquid systems where wetting is inhibited via a (self) lubrication effect produced by thermocapillary convection. We investigate shape changes in the lubricating air film when the ambient air pressure is reduced to determine the effect on load capacity and, ultimately, reliability of a system exploiting this effect. We examine the response to electrostatic charges that may induce the wetting of a solid surface, even when the lubricating action of the air film would be sufficient to prevent it otherwise. We have observed that a static model is suitable for describing the behavior of such systems despite the existence of convection. An original technique for measuring the difference between advancing and receding contact angles of a silicone oil drop attached at a copper platelet is presented. The drop is first squeezed and then released by an unwetted glass surface loaded onto the drop. Again, the static model seems suitable to describe the mechanical behavior of such a system.

dell'Aversana, P.; Tontodonato, V.; Neitzel, G. P.

1999-11-01

290

Characteristic study of atmospheric pressure microplasma jets with various operating conditions  

Energy Technology Data Exchange (ETDEWEB)

Non-thermal microplasma jets generated under atmospheric pressure by means of radio-frequency of 13.56 MHz and low-frequency of several tens of kilohertz are characterized. They show several distinct discharge characteristics. Two operation modes of the plasma are observed when the single pin electrode is utilized and separated by the remote ground, and where plasma is sustained between the pin electrode and the ground ring electrode. The electrical characteristic of discharges and various effects of the ground ring electrode are presented. We observe that the emission spectra are dominated by the presence of excited nitrogen, helium, and nitrogen ions. Highly reactive radicals such as hydroxyl (OH) and atomic oxygen are also detected. With the addition of a ground ring electrode, the discharge current and optical emission intensities from the plasma plume are enhanced significantly indicating that the generated plasma is near the glow discharge mode.

Kim, S.J. [Department of Physics, Dong-A University, 840 Hadan-dong, Saha-gu, Busan 604-714 (Korea, Republic of); Chung, T.H., E-mail: thchung@dau.ac.k [Department of Physics, Dong-A University, 840 Hadan-dong, Saha-gu, Busan 604-714 (Korea, Republic of); Bae, S.H. [Department of Physics, Dong-A University, 840 Hadan-dong, Saha-gu, Busan 604-714 (Korea, Republic of)

2009-05-29

291

High Pressure Compression-Molding of ?-Cellulose and Effects of Operating Conditions  

OpenAIRE

Commercial ?-cellulose was compression-molded to produce 1A dog-bone specimens under various operating conditions without any additive. The resulting agromaterials exhibited a smooth, plastic-like surface, and constituted a suitable target as replacement for plastic materials. Tensile and three-points bending tests were conducted according to ISO standards related to the evaluation of plastic materials. The specimens had strengths comparable to classical petroleum-based thermoplastics. They ...

Antoine Rouilly; Luc Rigal; Virginie Vandenbossche; David Viet; Thibaud Pintiaux

2013-01-01

292

Morphological variations in AuxSiy nanostructures under variable pressure and annealing conditions  

Science.gov (United States)

Well-ordered, substrate symmetry-driven, AuxSiy structures of average size ~25 nm were formed under ultra-high vacuum (UHV) conditions using molecular beam epitaxy method. Post-annealing was done at 500 °C in three different vacuum conditions: (1) low vacuum (LV) (10-2 mbar), (2) high vacuum (HV) (10-5 mbar) and (3) UHV (10-10 mbar) (MBE chamber). For both HV and LV cases, the AuxSiy nanostructures were found to have their corners rounded unlike in UHV case where the structures have sharp edges. In all the above three cases, samples were exposed to air before annealing. In situ annealing inside UHV chamber without exposing to air resulted in well-aligned rectangles with sharp corners, while sharp but irregular island structures were found for air exposed and UHV annealing system. The role of residual gases present in LV and HV annealing environment and inhibition of lateral surface diffusion due to the presence of surface oxide (through air exposure) would be discussed. Annealing at various conditions yielded variation in the coverage and correspondingly, the average area of nanostructures varied from a ~329 nm2 (as deposited) to ~2,578 nm2 (at high temperature). High-resolution transmission electron microscopy (planar and cross section) has been utilized to study the morphological variations.

Rath, A.; Dash, J. K.; Juluri, R. R.; Satyam, P. V.

2014-11-01

293

Factors association and predisposing conditions in the event of pressure ulcers  

Directory of Open Access Journals (Sweden)

Full Text Available Objective: to examine the association between predisposing conditions (CP, intrinsic (FI and extrinsic factors (EF with occurrence of PU in bedridden patients in the intensive care unit and wards of a university hospital. Metodology: it’s a descriptive and quantitative study, performed at a University Hospital from Natal/RN city, after approved by the Ethics Committee of Hospital Universitário Onofre Lopes (protocol number135/07 in which data were collected from December 2007 to February 2008, through a structured form, data from medical records and physical examination of the skin. The results were organized using SPSS 15.0 and analyzed using descriptive and inferential statistics. Results: of the 30 patients studied, were diagnosed in 19 UP 43.3% of them. Was found an association of 35.7% of the Predisposing conditions, Intrinsic factors and Extrinsic factors for all patients studied, statistically significant (p-value = 0001, between the average scores in patients with and without PU, with reason chance to 12.0 for the development of PU and there was moderate correlation (r=0618 in the presence of this association. Conclusion: results show the influence of the multiplicity of factors and conditions on the occurrence of PU, which brings us to reflect on the assistance focused on.

Thalyne Yuri de Araújo Farias

2010-01-01

294

Charged and neutral oxygen vacancies at MgO surfaces under realistic temperature and pressure conditions  

Science.gov (United States)

Surface O vacancies (F-centers) can strongly influence catalytic properties of MgO and metal clusters supported on MgO, but the experimental determination of their concentration at catalytic conditions is difficult. We employ density-functional theory and the ab initio atomistic thermodynamics approach to determine concentration and charge states of F-centers at (111) and flat and stepped (100) surfaces of MgO at realistic (T, p) conditions. Slab models and the virtual-crystal approximation [1] are used to model charged defects at surfaces. We find a strong dependence of F^+ and F^2+ formation energy on the exchange-correlation (XC) functional. Varying the amount of screening and fraction of exact exchange within the HSE functional, we find a linear correlation between defect formation energies and calculated valence-band width of the host material, in line with recent results for bulk systems [2]. Using this correlation and extrapolating to experimental band width, we conclude that only F^2+ centers can be present in significant concentrations at the (100) terraces at realistic conditions. --- [1] L. Vegard, Z. Phys. 5, 17 (1921); M. Scheffler, Physica 146B, 176 (1987); [2] R. Ramprasad et al., subm. to Phys. Rev. Lett.

Richter, Norina A.; Levchenko, Sergey V.; Scheffler, Matthias

2012-02-01

295

Failure strains and proposed limit strains for an reactor pressure vessel under severe accident conditions  

International Nuclear Information System (INIS)

The local failure strains of essential design elements of a reactor vessel are investigated. The size influence of the structure is of special interest. Typical severe accident conditions including elevated temperatures and dynamic loads are considered. The main part of work consists of test families with specimens under uniaxial and biaxial load. Within one test family the specimen geometry and the load conditions are similar, but the size is varied up to reactor dimensions. Special attention is given to geometries with a hole or a notch causing non-uniform stress and strain distributions typical for the reactor vessel. A key problem is to determine the local failure strain. Here suitable methods had to be developed including the so-called 'vanishing gap method', and the 'forging die method'. They are based on post-test geometrical measurements of the fracture surfaces and reconstructions of the related strain fields using finite element models. The results indicate that stresses versus dimensionless deformations are approximately size independent up to failure for specimens of similar geometry under similar load conditions. Local failure strains could be determined. The values are rather high and size dependent. Statistical evaluation allow the proposal of limit strains which are also size dependent. If these limit strains are not exceeded, the structures will not fracture

296

Laboratory measurements of materials in extreme conditions; The use of high energy radiation sources for high pressure studies  

Energy Technology Data Exchange (ETDEWEB)

High energy lasers can be used to study material conditions that are appropriate fort inertial confinement fusion: that is, materials at high densities, temperatures, and pressures. Pulsed power devices can offer similar opportunities. The National Ignition Facility (NIF) will be a high energy multi-beam laser designed to achieve the thermonuclear ignition of a mm-scale DT-filled target in the laboratory. At the same time, NE will provide the physics community with a unique tool for the study of high energy density matter at states unreachable by any other laboratory technique. Here we describe how these lasers and pulsed power tools can contribute to investigations of high energy density matter in the areas of material properties and equations of state, extend present laboratory shock techniques such as high-speed jets to new regimes, and allow study of extreme conditions found in astrophysical phenomena.

Cauble, R.; Remington, B.A.

1998-06-01

297

A model for calculation of RCS pressure during reflux boiling under reduced inventory conditions and its assessment against PKL data  

International Nuclear Information System (INIS)

There has been recent interest in the United States concerning the loss of residual heat removal system (RHRS) under reduced coolant inventory conditions for pressurized water reactors. This issue is also of interest in the Federal Republic of Germany and an experiment was performed in the integral PKL-HI experimental facility at Siemens-KWU to supply applicable data. Recently, an NRC-sponsored effort has been undertaken at the Idaho-National Engineering Laboratory to identify and analyze the important thermal-hydraulic phenomena in pressurized water reactors following the long term loss-of-RHRS during reduced inventory operation. The thermal-hydraulic response of a closed reactor coolant system during such a transient is investigated in this report. Some of the specific processes investigated include: reflux condensation in the steam generators, the corresponding pressure increase in the reactor coolant system, and void fraction distributions on the primary side of the system. Mathematical models of these and other physical processes Experiment B4.5

298

Verification of effects of fuel management schemes on the condition of pressure vessels and their support structures  

International Nuclear Information System (INIS)

A number of potential methods exist for assuring the adequacy of fracture control of reactor pressure vessel (PV) beltlines under normal and accident loads. One of these methods, involving the use of fuel management schemes for reducing the rate of neutron damage accumulation at points of high neutron exposure, shows considerable promise. Practices for assessing and controlling the condition of PV beltlines and their support structures follow the recommendations in the US Code of Federal Regulations 10CFR50 (App. G and H) and 10CFR21, respectively, as well as those of the ASME Boiler and Pressure Vessel Code, Sec. III ad XI. In summary fashion, this paper reviews the methods for fracture behavior assessment and control and the interfaces with physics-dosimetry-metallurgy. It then reviews the calculated effects of new fuel management schemes on derived exposure parameter values for a representative PWR power plant. This is followed by a review of recent results of LWR Pressure Vessel Surveillance Dosimetry Improvement Program (LWR-PV-SDIP) interlaboratory efforts. Also provided is an updated set of references to the literature that is most relevant to the LWR-PV-SDIP work through September, 1982

299

Slug behavior and pressure drop of adiabatic slug flow in a narrow rectangular duct under inclined conditions  

International Nuclear Information System (INIS)

Highlights: • The effect of inclination on distribution parameter and drift velocity is studied. • Slug behaviors in different flow regions are investigated. • Inclination influences the void fraction and slip ratio. • Drift flux models for calculating void fraction are evaluated. • Correlations of frictional pressure drop are evaluated in different flow regions. - Abstract: A visualization-based investigation was carried out on slug behavior and pressure drop of air–water slug flow in a narrow rectangular duct with cross section of 43 mm × 3.25 mm under inclined conditions. The velocity and length of slugs were obtained through image processing. Based on the liquid Reynolds number, slug flow was divided into laminar flow region (Rel l ? 3000). Experimental results showed that both the slug velocity and the slug length increased with the inclination angle increasing in laminar flow region, while they were nearly unvaried in turbulent flow region. The slug length and slug frequency decreased with the gas superficial velocity increasing or the liquid superficial velocity decreasing for all cases. For laminar flow, the predictions of frictional pressure drop by Chisholm model, Mishima–Hibiki correlation and Lee–Lee correlation could be significantly improved by replacing the void fraction with the ratio of the slug velocity divided by the gas superficial velocity, us/jg; for turbulent region, all three models could well predict the experimental data if void fraction is calculated by the Jones–Zuber correlation

300

Simulation and analysis of bearing pad to pressure tube contact heat transfer under large break LOCA conditions  

International Nuclear Information System (INIS)

In some postulated loss-of-coolant accidents (LOCAs) in a CANDU reactor, localized 'hot spots' can develop on the pressure tube as a result of decay heat dissipation by conduction through bearing pad/pressure tube contact locations. Depending on the severity of flow degradation in the channel, these 'hot spots' could represent a potential threat to fuel channel integrity. The most important parameter in the simulation of BP/PT contact is the contact conductance. Since BP/PT thermal contact conductance is a complex parameter which depends upon the thermal and physical characteristics of the material junction and the surrounding environment, contact conductance is determined from experiments relevant to the reactor conditions. A series of twelve full scale integrated BP/PT contact experiments have been conducted at AECL-WRL under CANDU Owner Group (COG). The objective of the experiments was to investigate the effect of BP/PT contact on PT thermal-mechanical behaviour. This paper presents the simulation of BP/PT interaction integrated experiments using SMARTT and MINI-SMARTT computer codes and subsequent derivation of the BP/PT contact conductance by best fitting of the experimental pressure tube temperature measurements. (author)

301

Influence of the external conditions on salt retention and pressure-induced electrical potential measured across a composite membrane  

DEFF Research Database (Denmark)

Transport on single electrolyte solutions (NaCl and MgCl2) due to pressure gradients across a commercial reverse osmosis membrane was studied by measuring volume flux (J(v)), salt rejection (S) and pressure induced electrical potential (Delta E) in a crossflow cell. The influence on these parameters of different external conditions due to hydrodynamic or chemical changes in the feed solutions was also studied. Changes were carried out by variation of the feed solution velocity (Reynolds numbers between 1500 and 3300) or the concentration ratio of mixed electrolytes (r = HCl/NaCl and HCl/MgCl2, r = 1, 0.5 and 0.1), respectively. Results show that J(v), S and Delta E values slightly increase when the velocity of the feed solution increases, but the mixed electrolytes strongly affect both salt rejection and pressure-induced electrical potential. A change in the sign of both parameters with respect to the value determined with single electrolytes at the same concentration was obtained, which is attributed to a strong coupling among the fluxes of individual ions and their distribution in the membrane when transport of mixed salt is studied. (C) 1999 Elsevier Science B.V. All rights reserved.

Benavente, Juana; Jonsson, Gunnar Eigil

1999-01-01

302

Slug to annular flow transition during boiloff in a rod bundle under high-pressure conditions  

International Nuclear Information System (INIS)

High-pressure boiloff experiments in a wide range of bundle powers by using the Two-Phase Flow Test Facility (TPTF) were conducted. Two kinds of boiloff patterns were observed in these experiments. One is the boiloff pattern in a low bundle power, in which the dryout points of rods locate at a certain elevation in the bundle because the mixture level controls the dryout points. The other is the boiloff pattern in a high bundle power, in which the clear mixture level can not be observed and the dryout points of rods locate in a wide range of vertical directions. The vertical scatter of the dryout points is considered to be due to the break of the thin water film on the heater rods under the annular flow pattern. A simple model to predict the slug to annular flow transition in the rod bundle is proposed. In the model, the slug to annular flow transition takes place when the interferences of the water films on the neighboring rods cease. The model appeares to give good predictions of the previous flow transition experiment conducted in a rod bundle. The slug-annular transition below the dryout points was predicted with the present model in the high power boiloff experiments of TPTF. No slug-annular transition below the dryout points is predicted with the present model in the low power boiloff experiments. (orig.)

303

Impact of in-sewer transformation on 43 pharmaceuticals in a pressurized sewer under anaerobic conditions.  

Science.gov (United States)

The occurrence of 43 pharmaceuticals and 2 metabolites of ibuprofen was evaluated at the inlet and the outlet of a pressure sewer pipe in order to asses if in-sewer processes affect the pharmaceutical concentrations during their pass through the pipe. The target compounds were detected at concentrations ranging from low ng/L to a few ?g/L, which are in the range commonly found in municipal wastewater of the studied area. The changes in concentrations between two sampling points were negligible for most compounds, i.e. from -10 to 10%. A higher decrease in concentrations (25-60 %) during the pass through the pipe was observed for diltiazem, citalopram, clarithromycin, bezafibrate and amlodipine. Negative removal was calculated for sulfamethoxazole (-66 ± 15%) and irbesartan (-58 ± 25%), which may be due to the conversion of conjugates back to their parent compounds in the sewer. The results show that microbial transformation of pharmaceuticals begins in sewer, albeit to different extents for different compounds. Therefore, the in-sewer transformation of pharmaceuticals should be assessed especially when their concentrations are used to estimate and refine the estimation of their per capita consumption in a catchment of interest in the sewage epidemiology approach. PMID:25462720

Jelic, Aleksandra; Rodriguez-Mozaz, Sara; Barceló, Damia; Gutierrez, Oriol

2014-10-01

304

Current Pressure Transducer Application of Model-based Prognostics Using Steady State Conditions  

Science.gov (United States)

Prognostics is the process of predicting a system's future states, health degradation/wear, and remaining useful life (RUL). This information plays an important role in preventing failure, reducing downtime, scheduling maintenance, and improving system utility. Prognostics relies heavily on wear estimation. In some components, the sensors used to estimate wear may not be fast enough to capture brief transient states that are indicative of wear. For this reason it is beneficial to be capable of detecting and estimating the extent of component wear using steady-state measurements. This paper details a method for estimating component wear using steady-state measurements, describes how this is used to predict future states, and presents a case study of a current/pressure (I/P) Transducer. I/P Transducer nominal and off-nominal behaviors are characterized using a physics-based model, and validated against expected and observed component behavior. This model is used to map observed steady-state responses to corresponding fault parameter values in the form of a lookup table. This method was chosen because of its fast, efficient nature, and its ability to be applied to both linear and non-linear systems. Using measurements of the steady state output, and the lookup table, wear is estimated. A regression is used to estimate the wear propagation parameter and characterize the damage progression function, which are used to predict future states and the remaining useful life of the system.

Teubert, Christopher; Daigle, Matthew J.

2014-01-01

305

Advances in Thin Film Thermocouple Durability Under High Temperature and Pressure Testing Conditions  

Science.gov (United States)

Thin film thermocouples for measuring material surface temperature have been previously demonstrated on several material systems and in various hostile test environments. A well-developed thin film fabrication procedure utilizing shadow masking for patterning the sensors elements had produced thin films with sufficient durability for applications in high temperature and pressure environments that exist in air-breathing and hydrogen-fueled burner rig and engine test facilities. However, while shadow masking had been a reliable method for specimens with flat and gently curved surfaces, it had not been consistently reliable for use on test components with sharp contours. This work reports on the feasibility of utilizing photolithography processing for patterning thin film thermocouples. Because this patterning process required changes in the thin film deposition process from that developed for shadow masking, the effect of these changes on thin film adherence during burner rig testing was evaluated. In addition to the results of changing the patterning method, the effects on thin film adherence of other processes used in the thin film fabrication procedure is also presented.

Martin, Lisa C.; Fralick, Gustave C.; Taylor, Keith F.

1999-01-01

306

The ReactorSTM: atomically resolved scanning tunneling microscopy under high-pressure, high-temperature catalytic reaction conditions.  

Science.gov (United States)

To enable atomic-scale observations of model catalysts under conditions approaching those used by the chemical industry, we have developed a second generation, high-pressure, high-temperature scanning tunneling microscope (STM): the ReactorSTM. It consists of a compact STM scanner, of which the tip extends into a 0.5 ml reactor flow-cell, that is housed in a ultra-high vacuum (UHV) system. The STM can be operated from UHV to 6 bars and from room temperature up to 600 K. A gas mixing and analysis system optimized for fast response times allows us to directly correlate the surface structure observed by STM with reactivity measurements from a mass spectrometer. The in situ STM experiments can be combined with ex situ UHV sample preparation and analysis techniques, including ion bombardment, thin film deposition, low-energy electron diffraction and x-ray photoelectron spectroscopy. The performance of the instrument is demonstrated by atomically resolved images of Au(111) and atom-row resolution on Pt(110), both under high-pressure and high-temperature conditions. PMID:25173272

Herbschleb, C T; van der Tuijn, P C; Roobol, S B; Navarro, V; Bakker, J W; Liu, Q; Stoltz, D; Cañas-Ventura, M E; Verdoes, G; van Spronsen, M A; Bergman, M; Crama, L; Taminiau, I; Ofitserov, A; van Baarle, G J C; Frenken, J W M

2014-08-01

307

The ReactorSTM: Atomically resolved scanning tunneling microscopy under high-pressure, high-temperature catalytic reaction conditions  

Science.gov (United States)

To enable atomic-scale observations of model catalysts under conditions approaching those used by the chemical industry, we have developed a second generation, high-pressure, high-temperature scanning tunneling microscope (STM): the ReactorSTM. It consists of a compact STM scanner, of which the tip extends into a 0.5 ml reactor flow-cell, that is housed in a ultra-high vacuum (UHV) system. The STM can be operated from UHV to 6 bars and from room temperature up to 600 K. A gas mixing and analysis system optimized for fast response times allows us to directly correlate the surface structure observed by STM with reactivity measurements from a mass spectrometer. The in situ STM experiments can be combined with ex situ UHV sample preparation and analysis techniques, including ion bombardment, thin film deposition, low-energy electron diffraction and x-ray photoelectron spectroscopy. The performance of the instrument is demonstrated by atomically resolved images of Au(111) and atom-row resolution on Pt(110), both under high-pressure and high-temperature conditions.

Herbschleb, C. T.; van der Tuijn, P. C.; Roobol, S. B.; Navarro, V.; Bakker, J. W.; Liu, Q.; Stoltz, D.; Cañas-Ventura, M. E.; Verdoes, G.; van Spronsen, M. A.; Bergman, M.; Crama, L.; Taminiau, I.; Ofitserov, A.; van Baarle, G. J. C.; Frenken, J. W. M.

2014-08-01

308

Phenomenology during the loss of residual heat removal system at midloop conditions with pressurizer PORVs open: Associated boron dilution  

International Nuclear Information System (INIS)

The loss of residual heat removal system (RHRS) at midloop operation is an important risk contributor at low power and shutdown conditions. In this kind of transient the reflux-condensation can play an important role during the sequence to avoid the core damage. Several simulations concerning the loss of the RHRS in a PWR-W with the pressurizer PORVs open have been carried out with TRACE code considering the availability of steam generators. The present study aims to analyze, firstly, the thermal-hydraulic behavior after the loss of RHRS at midloop conditions throughout different configurations with reflux-condensation as the sole cooling mechanism available, and secondly, the issue related to the boron dilution that takes place during this kind of transient. The simulation results show that in the open RCS configuration, an equilibrium pressure is obtained in all cases and the reflux-condensation removes an important part of the decay heat. Moreover, in some configurations, this mechanism may cause the formation of an unborated water slug in the crossover leg that can lead to a boron dilution sequence

309

Simulation of ATWS conditions in pressurized water reactors; Simulation von ATWS-Transienten in Druckwasserreaktoren  

Energy Technology Data Exchange (ETDEWEB)

Safety analyses of nuclear power plants use ATWS (Anticipated Transients without Scram) as a term covering also events involving assumed failure of the reactor scram system. In this type of failure of the reactor scram system, power development in the reactor core is determined only by neutron kinetics feedback via the fuel temperature, moderator temperature and moderator density. If borated coolant is supplied, there is the additional feedback from the boron concentration. For nuclear power plants, coupled code complexes are developed and used which are made up of a thermohydraulic plant code and a 3D neutron kinetics model of the reactor core. These lend themselves to the use in analyses of ATWS states. The work presented here about the ATWS problem was performed in the interest of a consistent application of the DYN3D 3D neutron kinetics code in combination with the ATHLET thermohydraulic system code, and the quantification of differences resulting from variations of initial and boundary conditions. The DYN3D/ATHLET coupled code complex was validated by recalculation of various operating transients and by solving benchmark problems. The article contains results computed taking into account the influence of systems engineering and neutron kinetics boundary conditions. The calculations shown are methodological studies in no way demonstrating proof. (orig.)

Kliem, Soeren; Mittag, Siegfried; Rohde, Ulrich; Grundmann, Ulrich; Weiss, Frank-Peter [Forschungszentrum Dresden-Rossendorf, Dresden (Germany). Inst. fuer Sicherheitsforschung

2009-02-15

310

Re-embrittlement of annealed pressure vessel, IAI1-material condition of a Loviisa irradiated weld  

International Nuclear Information System (INIS)

The re-irradiated (IAI1) material condition data of a VVER-440 weld, which is part of the contribution of Fortum Nuclear Services Ltd. to the IAEA research programme, are given in summary. The data were created with the lower half of the Loviisa NPP re-irradiation chain 12K3 using specimen reconstitution. The second re-irradiation fluence will be created with the upper half of the same chain later on. The tests include tensile tests, ISO Charpy-V impact tests, Charpy-V impact tests of 5 mm x5 mm and 3 mm x 4 mm cross-sectional specimens and fracture toughness tests of 10 mm x10 mm and 5 mm x 5 mm cross-sectional specimens. The baseline, I and IA-condition data have been reported earlier. The joint analyses of the test results including earlier Loviisa data as well as a short comparison to an irradiation in Halden are given. (orig.)

311

Preliminary Testing of a Pressurized Space Suit and Candidate Fabrics Under Simulated Mars Dust Storm and Dust Devil Conditions  

Science.gov (United States)

In August 2009 YAP Films (Toronto) received permission from all entities involved to create a documentary film illustrating what it might be like to be on the surface of Mars in a space suit during a dust storm or in a dust devil. The science consultants on this project utilized this opportunity to collect data which could be helpful to assess the durability of current space suit construction to the Martian environment. The NDX-1 prototype planetary space suit developed at the University of North Dakota was used in this study. The suit features a hard upper torso garment, and a soft lower torso and boots assembly. On top of that, a nylon-cotton outer layer is used to protect the suit from dust. Unmanned tests were carried out in the Martian Surface Wind Tunnel (MARSWIT) at the NASA Ames Research Center, with the suit pressurized to 10 kPa gauge. These tests blasted the space suit upper torso and helmet, and a collection of nine candidate outer layer fabrics, with wind-borne simulant for five different 10 min tests under both terrestrial and Martian surface pressures. The infiltration of the dust through the outer fabric of the space suit was photographically documented. The nine fabric samples were analyzed under light and electron microscopes for abrasion damage. Manned tests were carried out at Showbiz Studios (Van Nuys, California) with the pressure maintained at 20 2 kPa gauge. A large fan-created vortex lifted Martian dust simulant (Fullers Earth or JSC Mars-1) off of the floor, and one of the authors (Lee) wearing the NDX-1 space suit walked through it to judge both subjectively and objectively how the suit performed under these conditions. Both the procedures to scale the tests to Martian conditions and the results of the infiltration and abrasion studies will be discussed.

Gaier, James R.; deLeon, Pablo G.; Lee, Pascal; McCue, Terry R.; Hodgson, Edward W.; Thrasher, Jeff

2010-01-01

312

Geochemistry of ultrahigh-pressure anatexis: fractionation of elements in the Kokchetav gneisses during melting at diamond-facies conditions  

Science.gov (United States)

The Kokchetav complex in Kazakhstan contains garnet-bearing gneisses that formed by partial melting of metasedimentary rocks at ultrahigh-pressure (UHP) conditions. Partial melting and melt extraction from these rocks is documented by a decrease in K2O and an increase in FeO + MgO in the restites. The most characteristic trace element feature of the Kokchetav UHP restites is a strong depletion in light rare earth elements (LREE), Th and U. This is attributed to complete dissolution of monazite/allanite in the melt and variable degree of melt extraction. In contrast, Zr concentrations remain approximately constant in all gneisses. Using experimentally determined solubilities of LREE and Zr in high-pressure melts, these data constrain the temperature of melting to ~1,000 °C. Large ion lithophile elements (LILE) are only moderately depleted in the samples that have the lowest U, Th and LREE contents, indicating that phengite retains some LILE in the residue. Some restites display an increase in Nb/Ta with respect to the protolith. This further suggests the presence of phengite, which, in contrast to rutile, preferentially incorporates Nb over Ta. The trace element fractionation observed during UHP anatexis in the Kokchetav gneisses is significantly different from depletions reported in low-pressure restites, where generally no LREE and Th depletion occurs. Melting at UHP conditions resulted in an increase in the Sm/Nd ratio and a decoupling of the Sm-Nd and Lu-Hf systems in the restite. Further subduction of such restites and mixing with mantle rocks might thus lead to a distinct isotopic reservoir different from the bulk continental crust.

Stepanov, Aleksandr S.; Hermann, Joerg; Korsakov, Andrey V.; Rubatto, Daniela

2014-05-01

313

Effect of feedwater conditioning on corrosion behaviour of steam generator pipework materials in pressurized water reactors  

International Nuclear Information System (INIS)

The effect of the phosphate process and the low all volatile treatment procedure on the corrosion resistance of heating tubes of U tube-banked steam boilers is discussed. In individual cases the redox potential of the medium which results from the interaction of various oxidation and reduction agents present in the high temperature water and the self-regulating corrosion potential of the pipework cannot be determined by investigatory methods based on water analyses. In order to establish this type of potential independent of the procedure, the incorporation of potential probes in the components of interest is recommended. In this way any increased danger of corrosion of pipework due to oxidizing water conditions in the steam generator can be detected at an early state. The procedure is described. (orig.)

314

State of the art on the heat transfer experiments under supercritical pressure condition  

International Nuclear Information System (INIS)

The SCWR(Super-Critical Water cooled Reactor) is one of the six reactor candidates selected in the Gen-IV project which aims at the development of new reactors with enhanced economy and safety. The SCWR is considered to be a feasible concept of new nuclear power plant if the existing technologies developed in fossil fuel fired plant and LWR technologies together with additional research on several disciplines such as materials, water chemistry and safety. As KAERI takes part in the GIF(Generation IV Forum) for the Gen-IV project, domestic concerns about the SCWR have been recently increased. In order to establish a foundation for the development of SCWR, efforts should be concentrated on the conceptual design of systems and the associated key experiments as well. Heat transfer experiments, among others, under supercritical condition are required for the proper prediction of thermal hydraulic phenomena, which are essential for the thermal hydraulic designs of reactor core. Nevertheless, the experiments have not been performed in Korea yet. This report deals with fundamental surveys on the heat transfer experiments under supercritical conditions, which are required for the understanding of heat transfer characteristics for the thermal hydraulic designs of supercritical reactor core. Investigations on the physical properties of water and CO2 showed that the physical properties such as density, specific heat, viscosity and thermal conductivity are significantly changed near the pseudo-critical points. The state of the art on the heat transfer characteristics in relation with heat transfer deterioration and heat transfer coefficient is briefly described. In addition, previous experiments with supercritical water as well as supercritical CO2 and Freon used for an alternating fluid are presented

315

Electrochemical promotion of catalytic ethylene oxidation on Pt/YSZ catalyst under low pressure conditions  

International Nuclear Information System (INIS)

The catalytic oxidation of C2H4 on Pt catalyst film interfaced with the oxygen-ion conducting yttria-stabilized zirconia solid electrolyte (YSZ) has been studied in the 10-5 and 10-4 mbar range. Photoemission electron microscopy (PEEM) was used as spatially resolving method. Under open circuit conditions (VWR=0 V) the CO2 production increases by rising p(C2H4) and then at a critical point decreases sharply, showing a pronounced hysteresis. The hysteresis and the abrupt rate decrease are attributed to the build-up of a carbonaceous CHx layer inhibiting O2 adsorption and hence poisoning the catalyst. Applying an anodic potential of +1V leads to trigger a transition from the unreactive branch of the reaction to an active branch. The huge non-Faradayicity reported in the literature for this reaction system is explained as an ignition effect caused by the partial removal of the inhibiting carbonaceaous layer. The electrode has been characterized by SEM, XRD and a profilometer.

316

Electrochemical promotion of catalytic ethylene oxidation on Pt/YSZ catalyst under low pressure conditions  

Energy Technology Data Exchange (ETDEWEB)

The catalytic oxidation of C{sub 2}H{sub 4} on Pt catalyst film interfaced with the oxygen-ion conducting yttria-stabilized zirconia solid electrolyte (YSZ) has been studied in the 10{sup -5} and 10{sup -4} mbar range. Photoemission electron microscopy (PEEM) was used as spatially resolving method. Under open circuit conditions (VWR=0 V) the CO{sub 2} production increases by rising p(C{sub 2}H{sub 4}) and then at a critical point decreases sharply, showing a pronounced hysteresis. The hysteresis and the abrupt rate decrease are attributed to the build-up of a carbonaceous CH{sub x} layer inhibiting O{sub 2} adsorption and hence poisoning the catalyst. Applying an anodic potential of +1V leads to trigger a transition from the unreactive branch of the reaction to an active branch. The huge non-Faradayicity reported in the literature for this reaction system is explained as an ignition effect caused by the partial removal of the inhibiting carbonaceaous layer. The electrode has been characterized by SEM, XRD and a profilometer.

Toghan, Arafat; Roesken, Liz Michaela; Imbihl, Ronald [Institut fuer Physikalische Chemie und Elektrochemie, Universitaet Hannover, Callinstrasse 3-3a, D-30167 Hannover (Germany)

2010-07-01

317

An assessment of the failure rate for the beltline region of PWR pressure vessels during normal operation and certain transient conditions. Technical report  

International Nuclear Information System (INIS)

A study was conducted to assess the failure rate for the beltline region of a generic pressurized-water reactor (PWR) pressure vessel. This assessment included the evaluation of several normal operating and transient reactor conditions. Failure rates were calculated from a computer code that used fracture mechanics methods to model the failure process; random number generation techniques were used to simulate random variables and model their interaction in the failure-process. This investigation had three major objectives: (1) to better define the effect of neutron irradiation, material variation, and flaw distribution on the failure rate for the beltline region of PWR pressure vessels, (2) to estimate the relative margins against failure for normal operation and certain transient conditions associated with nuclear pressure vessels, and (3) to evaluate the current limitations for using fracture mechanics models to predict failure rates for nuclear pressure vessels

318

Turbulence significantly increases pressure and fluid shear stress in an aortic aneurysm model under resting and exercise flow conditions.  

Science.gov (United States)

The numerical models of abdominal aortic aneurysm (AAA) in use do not take into account the non-Newtonian behavior of blood and the development of local turbulence. This study examines the influence of pulsatile, turbulent, non-Newtonian flow on fluid shear stresses and pressure changes under rest and exercise conditions. We numerically analyzed pulsatile turbulent flow, using simulated physiological rest and exercise waveforms, in axisymmetric-rigid aortic aneurysm models (AAMs). Discretization of governing equations was achieved using a finite element scheme. Maximum turbulence-induced shear stress was found at the distal end of an AAM. In large AAMs (dilated to undilated diameter ratio = 3.33) at peak systolic flow velocity, fluid shear stress during exercise is 70.4% higher than at rest. Our study provides a numerical, noninvasive method for obtaining detailed data on the forces generated by pulsatile turbulent flow in AAAs that are difficult to study in humans and in physical models. Our data suggest that increased flow turbulence results in increased shear stress in aneurysms. While pressure readings are fairly uniform along the length of an aneurysm, the kinetic energy generated by turbulence impacting on the wall of the distal half of the aneurysm increases fluid and wall shear stress at this site. If the increased fluid shear stress results in further dilation and hence further turbulence, wall stress may be a mechanism for aneurysmal growth and eventual rupture. PMID:17349339

Khanafer, Khalil M; Bull, Joseph L; Upchurch, Gilbert R; Berguer, Ramon

2007-01-01

319

Low-temperature rupture behavior of Zircaloy clad pressurized water reactor spent fuel rods under dry storage conditions  

International Nuclear Information System (INIS)

Creep rupture studies on five well-characterized Zircaloy clad pressurized water reactor spent fuel rods, which were pressurized to a hoop stress of approximately 145 MPa, were conducted for up to 2101 h at 3230C. The conditions were chosen for limited annealing of in-reactor irradiation-hardening. No cladding breaches occurred, although significant hydride agglomeration and reorientation took place in rods that cooled under stress. Observations are interpreted in terms of a conservatively modified Larson-Miller curve to provide a lower bound on permissible maximum dry-storage temperatures, assuming creep rupture as the life-limiting mechanism. If hydride reorientation can be ruled out during dry storage, 3050C is a conservative lower bound, based on the creep rupture mechanism, for the maximum storage temperature of rods with irradiation hardened cladding to ensure a 100-year cladding lifetime in an inert atmosphere. An oxidizing atmosphere reduces the lower bound on the maximum permissible storage temperature by approx. 50C. While high-temperature tests based on creep rupture as the limiting mechanism indicate that storage at temperatures between 4000C and 4400C may be feasible for rods which are annealed, tests to study rod performance in the 3050 to 4000C temperature range have not been conducted. 37 references, 10 figures, 7 tables

320

Measurement of the growth kinetics of cracks in bainitic NPP pressure vessel steel under stress corrosion cracking conditions  

International Nuclear Information System (INIS)

To evaluate the possibility of stable crack growth in the reactor pressure vessel wall due to the stress corrosion cracking (SCC) mechanism and as well as to calculate the life time of the pressure vessel, the kinetics of the crack growth should be evaluated. The paper deals with the comparison between the behaviour of small and large cracks from the point of view of SCC. The material 15Kh2NMFAA used for the WWER-type RPVs, as the base material, was chosen for the experiments. Slow strain rate tests are carried out on tensile specimens to evaluate the kinetics of small environmentally -initiated cracks. The slow displacement rate are applied to CT specimens is used to evaluate the kinetics of large pre-existing cracks. To compare the response to different water chemistry conditions, tests have been carried out in WWER primary circuit environment with low (below 20 ppb) and high (higher that 1 ppm) dissolved oxygen (DO) content. All the tests have been done in through-flow autoclave system with controlled water chemistry. (author)

321

DNS study of the ignition of n-heptane fuel spray under high pressure and lean conditions  

International Nuclear Information System (INIS)

Direct numerical simulations (DNS) are used to investigate the ignition of n-heptane fuel spray under high pressure and lean conditions. For the solution of the carrier gas fluid, the Eulerian method is employed, while for the fuel spray, the Lagrangian method is used. A chemistry mechanism for n-heptane with 33 species and 64 reactions is adopted to describe the chemical reactions. Initial carrier gas temperature and pressure are 926 K and 30.56 atmospheres, respectively. Initial global equivalence ratio is 0.258. Two cases with droplet radiuses of 35.5 and 20.0 macrons are simulated. Evolutions of the carrier gas temperature and species mass fractions are presented. Contours of the carrier gas temperature and species mass fractions near ignition and after ignition are presented. The results show that the smaller fuel droplet case ignites earlier than the larger droplet case. For the larger droplet case, ignition occurs first at one location; for the smaller droplet case, however, ignition occurs first at multiple locations. At ignition kernels, significant NO is produced when temperature is high enough at the ignition kernels. For the larger droplet case, more NO is produced than the smaller droplet case due to the inhomogeneous distribution and incomplete mixing of fuel vapor

322

Investigations of Response Time Parameters of a Pneumatic 3/2 Direct Acting Solenoid Valve Under Various Working Pressure Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available In pneumatic circuits, a solenoid valve is a key component for controlling and directing pneumatic energy. The solenoid valve functional performances are defined as response time parameters with respect to its actuations in terms of direction changing time. This paper aims to present response time parameters of solenoid valves under various working pressures. An experimental setup is employed in order to measure response time with reference to the input signals. The response time plays significant role for evaluating the valve performance in sensitive applications. The response time parameters includes the on delay, the off delay, the on time, the off time, the cycle time and the switching frequency. In this experimental investigation the influence of various input pressure conditions is recorded and tabulated. Valves with varying orifice diameter are employed and the investigation reveals the influence of orifice diameter in response time variations. The newly-proposed six response time parameters can be used to rate and select the appropriate valve for various industrial applications.

K. A. Venkataraman

2013-08-01

323

Effects of Pressure on the Properties of Coal Char Under Gasification Conditions at High Initial Heating Rates  

Science.gov (United States)

The effects of elevated pressure and high heating rates on coal pyrolysis and gasification were investigated. A high-pressure flat-flame burner (HPFFB) was designed and built to conduct these studies. The HPFFB was designed to provide an environment with laminar, dispersed entrained flow, with particle heating rates of ˜105 K/s, pressures of up to 15 atm, and gas temperatures of up to 2000 K. Residence times were varied from 30 to 700 ms in this study. Pyrolysis experiments were conducted at particle heating rates of ˜10 5 K/s and maximum gas temperatures of ˜1700 K at pressures of 1 to 15 atm. A new coal swelling correlation was developed that predicts the effects of heating rate, pressure, and coal rank on the swelling ratio at heating rates above ˜104 K/s. A coal swelling rank index system based on 13C-NMR chemical structural parameters was devised. The empirical swelling model requires user inputs of the coal ultimate and proximate analyses and the use of a transient particle energy balance to predict the maximum particle heating rate. The swelling model was used to explain differences in previously reported bituminous coal swelling ratios that were measured in facilities with different heating rates. Char gasification studies by CO2 were conducted on a subbituminous coal and 4 bituminous coals in the HPFFB. Pressures of 5, 10, and 15 atmospheres were used with gas compositions of 20, 40, and 90 mole % CO2. Gas conditions with peak temperatures of 1700 K to 2000 K were used, which resulted in char particle temperatures of 1000 K to 1800 K. Three gasification models were developed to fit and analyze the gasification data. A simple 1 st--order model was used to show that the measured gasification rates were far below the film-diffusion limit. The other two models, designated CCK and CCKN, were based on three versions of the CBK models. CCKN used an nth--order kinetic mechanism and CCK used a semi-global Langmuir-Hinshelwood kinetic mechanism. The two CCK models fit the HPFFB gasification data better than the 1st--order model. The fits of the gasification data with CCK and CCKN were comparable to each other. The fit of the data in CCK suggests that Knudsen diffusion may have influenced the gasification rates in the HPFFB experiments. The gasification rate parameters in each of the three models were correlated with coal rank. 13C-NMR parameters were used to estimate a structural parameter of the coal char. Char-CO 2 gasification rate coefficients correlated better with this NMR-based char structure index than it did with the carbon and oxygen content of the parent coal. Keywords: Randy Shurtz, coal, gasification, pyrolysis, swelling, pressure, heating rate, soot

Shurtz, Randy Clark

324

Effects of a carbon convection field on large diamond growth under high-pressure high-temperature conditions  

International Nuclear Information System (INIS)

Large diamond crystals were successfully synthesized by a FeNi—C system using the temperature gradient method under high-pressure high-temperature conditions. The assembly of the growth cell was improved and the growth process of diamond was investigated. Effects of the symmetry of the carbon convection field around the growing diamond crystal were investigated systematically by adjusting the position of the seed crystal in the melted catalyst/solvent. The results indicate that the morphologies and metal inclusion distributions of the synthetic diamond crystals vary obviously in both symmetric and non-symmetric carbon convection fields with temperature. Moreover, the finite element method was applied to analyze the carbon convection mode of the melted catalyst/solvent around the diamond crystal. This work is helpful for understanding the growth mechanism of diamond

325

Influence of the cathode surface conditions on V-A characteristics in low-pressure nitrogen discharge  

Science.gov (United States)

In this paper we demonstrate and analyse the influence of cathode surface inhomogeneities on the breakdown, volt-ampere (V-A) characteristics and the spatial structure of the low-pressure non-equilibrium discharges. The idea for this work came from the need to explain the non-typical V-A characteristics (positive slope of the characteristics in low-current regime of the discharge) that we observed in a parallel-plate, dc discharge in nitrogen. It was found that the cathode was locally conditioned by the discharge that operated in the constricted glow regime. Spatial inhomogeneity of the cathode surface strongly affected the subsequent operation in the breakdown-Townsend regime where discharge is supposed to be uniform.

Goci?, S.; Škoro, N.; Mari?, D.; Petrovi?, Z. Lj

2014-06-01

326

Influence of deposition conditions on mechanical properties of low-pressure chemical vapor deposited low-stress silicon nitride films  

International Nuclear Information System (INIS)

The effect of deposition temperature, deposition pressure, or input gas ratio (SiH2Cl2:NH3) on film stress was determined for low-pressure chemical vapor deposited silicon nitride films. Wafer curvature measurements were performed for films deposited on single crystal silicon and amorphous silica wafer substrates to determine film stress ?dep, biaxial modulus Ef+, and coefficient of thermal expansion ?f. Apparent plane strain film modulus E-barf' and hardness H were measured using depth-sensing indentation. Ellipsometry was used to measure film thickness tf and refractive index n. Infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), forward recoil energy spectroscopy (FReS), and Rutherford backscattering spectroscopy (RBS) experiments were performed to determine film composition. Although film deposition stress varied from -135 MPa (compressive) to 235 MPa (tensile) Ef+, E-barf', H, and ?f remained nearly constant. Infrared spectroscopy resolved only Si-N species for all films, and results from FReS on three films confirmed that the hydrogen content was negligible. RBS and XPS indicated that Si/N increased with increased compressive ?dep. Ellipsometry and RBS indicated that all films were silicon-rich, to a greater extent with increased compressive ?dep. As RBS indicatesive ?dep. As RBS indicated that atomic density decreased with increased compressive deposition stress, it was concluded that the deposition conditions changed both thermal and intrinsic deposition stress for all films. In particular, intrinsic stress was tensile, and became increasingly tensile for increased Si/N and decreased atomic density. Assuming thermal stress was similar for all films examined here, the intrinsic stress must have varied from changes dependent on the deposition conditions

327

Development of Evaluation Technique for Hydrogen Embrittlement Behavior of Metallic Materials Using in-situ SP Testing under Pressurized Hydrogen Gas Conditions  

International Nuclear Information System (INIS)

Recently, alternative and novel energy resources have been developed for use in the future because of the current environmental problems and exhaustion of fossil energy resources. Hydrogen energy has many merits, such as its environmental friendliness, easy storage, and easy production, but it also has disadvantages, in that it is highly combustible and explosive. In this study, a test procedure using a simple SP test under highly pressurized hydrogen gas conditions was established. In order to evaluate its applicability, SP tests were carried out using a stainless steel (SUS316L) sample under atmospheric, pressurized helium, and pressurized hydrogen gas conditions. The results under the pressurized hydrogen gas condition showed fissuring and produced a reduction of the elongation in the plastic instability region due to hydrogen embrittlement, showing the effectiveness of the current in-situ SP test

328

The Influence of Collar on Surge Pressure Caused by the Drilling Fluid Viscous Force under Pumping Condition  

OpenAIRE

The study of surge pressure is of significant importance for the safety of drilling process because field practice shows that the surge pressure caused by fluid viscous force can cause a great damage to the drilling operation. The accurate calculation of surge pressure is directly related to the safety of the drilling process. However, the existing surge pressure models rarely take the impact of the collar into consideration and thus will inevitably affect the precision of the surge pressure ...

Jun Li; Zhen Huang; Ke Li; Wei Wu

2013-01-01

329

Potential application of a flash-type barometric desalination plant powered by waste heat from electric-power stations in Cyprus  

International Nuclear Information System (INIS)

This paper describes and evaluates the results of a study into the problems of freshwater production and shortages on the island of Cyprus. The use of a novel barometric flash-type desalinator, driven by otherwise waste-heat from the island's power-stations, is proposed as a means of increasing freshwater supplies. Mathematical models are described and used to investigate the thermodynamic performance and economic viability of the proposed system. Although water and electricity supply data for the island of Cyprus were used for the purposes of this investigation, the overall findings are thought have a wider applicability

330

Stability of supercritical water-cooled reactor during steady-state and sliding pressure start-up conditions  

International Nuclear Information System (INIS)

Full text of publication follows: The drastic change of fluid density in the reactor core of a supercritical water-cooled reactor (SCWR) gives rise to the concern of density wave stability. Using a single channel thermal-hydraulic model, the stability boundary maps of the U.S. reference SCWR design have been constructed for both the steady state and the sliding pressure start-up conditions. For the steady state, the supercritical water in the reactor core has been simulated using a three-region model - (1) a 'heavy fluid' with constant density, (2) a mixture of 'heavy fluid' and 'light fluid' similar to homogeneous-equilibrium two-phase mixture, and finally (3) a 'light fluid' which behaves like an ideal gas or superheated steam. The governing non-dimensional groups have been determined from a non-dimensional analysis of the conservation equations for this three-region supercritical water model. Two important non-dimensional groups, namely, Pseudo-Subcooling number (Npsub) and Expansion number (Nexp), which are similar to the Subcooling number (Nsub) and Phase Change number (Npch) commonly used in the analysis of the subcritical two-phase flow, have been identified for the supercritical region. The stability map in the supercritical region has been plotted in the Pseudo-Subcooling number versus Expansion number plane. It has been found that the U. S. reference SCWR design operates in the stable region with a big margin. Sens the stable region with a big margin. Sensitivity studies have been performed with respect to the inlet orifice coefficient, system pressure and the inlet coolant velocity. It has been found that the stability boundary in the Npsub - Nexp plane is not sensitive to the system pressure and the inlet coolant velocity, but it is sensitive to the inlet orifice coefficient. This is consistent with the findings of the earlier research done for the subcritical two-phase flow. During the sliding pressure start-up operation of the SCWR, two-phase steam-water mixture at subcritical pressure will appear in the reactor core. A non-homogeneous (e. g., drift-flux) nonequilibrium two-phase flow model was applied. An exponential vapor generation rate for subcooled boiling was assumed along with a simplified but recent correlation for vapor drift velocity. The characteristic equation was numerically integrated, and the stability boundary map was plotted on the traditional Subcooling number versus Phase Change number plane. The effects of different two-phase flow models on the stability boundary have also been investigated. Thus, stability boundary maps have been constructed using four different models, namely, the Homogenous-Equilibrium model, the Homogenous-Nonequilibrium model, the Non-homogenous-Equilibrium model and the Non-homogenous-Non-Equilibrium model. It has been found that the Homogenous-Nonequilibrium model predicts the most conservative stability boundary at high Subcooling numbers, while the Homogenous-Equilibrium model yields the most conservative boundary at low Subcooling numbers. These maps are being used to develop the sliding pressure start-up strategies of the SCWR. Work is underway to expand the single channel model to a multi-channel model with neutronic feedback to study the local flow instabilities in a SCWR. (authors)

331

The burst behavior of the heat transfer tube under an internal pressure load with extraordinarily high temperature condition  

International Nuclear Information System (INIS)

Rapid bursting tests using the Tube Rupture Simulation Test Rig (TRUST-2) and its overheating rupture analyses were carried out on the 2·1/4Cr-1Mo steel tube under an internal pressure load with extraordinarily high temperature condition. The tube failure behaviors were classified into three patterns of the ductile failure, the creep failure, and the ductile failure accompanied by creep, depending on the test conditions. In comparison between the test and the analysis on the creep failure and the ductile failure accompanied by creep, the time to failure of the analysis is estimated 25-50% shorter than that of the test, and the analysis is considered to be conservative. On the ductile failure, the times to failure of the test and the analysis become close but that of the analysis is still estimated about 10% shorter; the temperature to failure of the analysis is calculated about 100degC lower than that of the test; therefore, the conservatism of the analysis is confirmed. On the creep failure, if the time coefficient of the analysis is given about 1.5-2, the time to failure of the analysis becomes close to that of the test, which means that the analysis by use of the time coefficient 3 results in having the safety margin of 1.5-2 in the application to the Prototype FBR MONJU. (author)

332

Shape-controlled synthesis of diamond crystal by epitaxial growth under high pressure and high temperature conditions  

International Nuclear Information System (INIS)

In this paper, the diamond epitaxial growth mechanism has been studied in detail by employing several types of diamond as a seed in a catalyst—graphite system under high pressure and high temperature (HPHT) conditions. We find that the diamond nucleation, growth rate, crystal orientation, and morphology are significantly influenced by the original seeds. The smooth surfaces of seeds are beneficial for the fabrication of high-quality diamond. Our results reveal that the diamond morphology is mainly determined by the original shape of seeds in the early growth stage, but it has an adjustment process during the growth and leads to well symmetry. Additionally, we have also established the growth model for the twinned diamond grown on several seeds, and proposed the possible growth processes by tracking the particular shapes of seeds before and after treatment under HPHT conditions. These results suggest that the shape-controlled synthesis of diamond with well morphology can be realized by employing certain suitable diamond seeds. This work is expected to play an important role in the preparation of trustworthy diamond-based electronic and photonic devices. (interdisciplinary physics and related areas of science and technology)

333

Performance of wear-resistant iron base hardfacing alloys in valves operating under prototypical pressurized water reactor conditions  

Energy Technology Data Exchange (ETDEWEB)

Stroke cycling tests are being conducted on gate valves with iron base hardfacing materials under simulated pressurized water reactor (PWR) conditions to find an alternative to the cobalt-based Stellites. The first phase of the program under PWR conditions where the valves were opened and closed 2000 times over a period of about 1 year has recently been completed. The candidate alloys were EB 5183, EVERIT 50, NOREM 01 and NOREM 04. One valve with Stellite 6 trim served as a standard. Prior to testing, a base-line inaugural inspection was performed. At approximately 3 month intervals and 500 stroke cycles the performance of the alloys was monitored by non-destructive examination, profilometry and leak testing. Also, corrosion coupons were used to monitor metal loss from corrosion alone. The test results show all the candidate alloys performed better than Stellite 6. One valve with EB 5183 and a valve with NOREM 04 did not show any hot leakage as a result of stroke cycling. (orig.).

Inglis, I.; Murphy, E.V. (Atomic Energy of Canada Ltd. CANDU, Sheridan Park Research Community, Mississauga, Ontario (Canada)); Ocken, H. (Electric Power Research Inst., Palo Alto, CA (United States))

1992-07-24

334

Environmentally-Assisted Cracking of Low-Alloy Reactor Pressure Vessel Steels under Boiling Water Reactor Conditions  

International Nuclear Information System (INIS)

The present report summarizes the experimental work performed by PSI on the environmentally-assisted cracking (EAC) of low-alloy steels (LAS) in the frame of the RIKORR-project during the period from January 2000 to August 2001. Within this project, the EAC crack growth behaviour of different low-alloy reactor pressure vessel (RPV) steels, weld filler and weld heat-affected zone materials is investigated under simulated transient and steady-state BWR/NWC power operation conditions. The EAC crack growth behaviour of different low-alloy RPV steels was characterized by slow rising load (SRL) / low-frequency corrosion fatigue (LFCF) and constant load tests with pre-cracked fracture mechanics specimens in oxygenated high-temperature water at temperatures of either 288, 250, 200 or 150 C. These tests revealed the following important interim results: Under low-flow and highly oxidizing (ECP >= 100 mV SHE) conditions, the ASME XI 'wet' reference fatigue crack growth curve could be significantly exceeded by cyclic fatigue loading at low frequencies (<0.001 Hz), at high and low load-ratios R, and by ripple loading near to DKth fatigue thresholds. The BWR VIP 60 SCC disposition lines may be significantly or slightly exceeded (even in steels with a low sulphur content) in the case of small load fluctuations at high load ratios (ripple loading) or at intermediate temperatures (200 -250 C) in RPV materials, which show a distinct susceptibility to dynamic strain ageing (DSA). (author)

335

Environmentally-Assisted Cracking of Low-Alloy Reactor Pressure Vessel Steels under Boiling Water Reactor Conditions  

Energy Technology Data Exchange (ETDEWEB)

The present report summarizes the experimental work performed by PSI on the environmentally-assisted cracking (EAC) of low-alloy steels (LAS) in the frame of the RIKORR-project during the period from January 2000 to August 2001. Within this project, the EAC crack growth behaviour of different low-alloy reactor pressure vessel (RPV) steels, weld filler and weld heat-affected zone materials is investigated under simulated transient and steady-state BWR/NWC power operation conditions. The EAC crack growth behaviour of different low-alloy RPV steels was characterized by slow rising load (SRL) / low-frequency corrosion fatigue (LFCF) and constant load tests with pre-cracked fracture mechanics specimens in oxygenated high-temperature water at temperatures of either 288, 250, 200 or 150 C. These tests revealed the following important interim results: Under low-flow and highly oxidizing (ECP >= 100 mV SHE) conditions, the ASME XI 'wet' reference fatigue crack growth curve could be significantly exceeded by cyclic fatigue loading at low frequencies (<0.001 Hz), at high and low load-ratios R, and by ripple loading near to DKth fatigue thresholds. The BWR VIP 60 SCC disposition lines may be significantly or slightly exceeded (even in steels with a low sulphur content) in the case of small load fluctuations at high load ratios (ripple loading) or at intermediate temperatures (200 -250 C) in RPV materials, which show a distinct susceptibility to dynamic strain ageing (DSA). (author)

Seifert, H.P.; Ritter, S

2002-02-01

336

Crack growth behaviour of low alloy steels for pressure boundary components under transient light water reactor operating conditions (CASTOC)  

International Nuclear Information System (INIS)

The CASTOC project addresses environmentally assisted cracking (EAC) phenomena in low alloy steels used for pressure boundary components in both Western type boiling water reactors (BWR) and Russian type pressurised water reactors (VVER). It comprises the four work packages (WP): inter-laboratory comparison test (WP1); EAC behaviour under static load (WP2), EAC behaviour under cyclic load and load transients (WP3); evaluation of the results with regard to their relevance for components in practice (WP4). The use of sophisticated test facilities and measurement techniques for the on-line detection of crack advances have provided a more detailed understanding of the mechanisms of environmentally assisted cracking and provided quantitative data of crack growth rates as a function of loading events and time, respectively. The effect of several major parameters controlling EAC was investigated with particular emphasis on the transferability of the results to components in service. The obtained crack growth rate data were reflected on literature data and on commonly applied prediction curves as presented in the appropriate Code. At relevant stress intensity factors it could be shown that immediate cessation of growing cracks occurs after changing from cyclic to static load in high purity oxygenated BWR water and oxygen-free VVER water corresponding to steady state operation conditions. Susceptibility to environmentally assisted cracking under static load was observed for a heat affected zone material in oxygenated high purity water and also in base materials during a chloride transient representing BWR water condition below Action Level 1 of the EPRI Water Chemistry Guidelines according to the lectrical conductivity of the water but in the range of Action Level 2 according to the content of chlorides. Time based crack growth was also observed in one Russian type base material in oxygenated VVER water and in one Western type base material in oxygenated high purity BWR water at stress intensity factors above the limit for linear elastic fracture mechanics. There is evidence that the prediction curves of the ASME Boiler and Pressure Vessel Code Section XI, Appendix A are not conservative for some relevant cases with regard to crack growth rates under cyclic load even in oxygenated high purity BWR water. The CASTOC results have provided an important contribution to the understanding of crack growth behavior on the one hand as a function of time and on the other hand as a consequence of the number and height of loading events. This is an important key for the evaluation of transient events, which may occur in a plant during service. (orig.)

337

Effect of aviation fuel type and fuel injection conditions on the spray characteristics of pressure swirl and hybrid air blast fuel injectors  

OpenAIRE

Feddema, Rick T. M.S.M.E., Purdue University, December 2013. Effect of Aviation Fuel Type and Fuel Injection Conditions on the Spray Characteristics of Pressure Swirl and Hybrid Air Blast Fuel Injectors. Major Professor: Dr. Paul E. Sojka, School of Mechanical Engineering Spray performance of pressure swirl and hybrid air blast fuel injectors are central to combustion stability, combustor heat management, and pollutant formation in aviation gas turbine engines. Next generation aviation gas t...

Feddema, Rick

2013-01-01

338

Are processing conditions similar in ball milling and high-pressure torsion? The case of the tetragonal-to-monoclinic phase transition in ZrO2 powders  

International Nuclear Information System (INIS)

Y2O3 partially stabilized zirconium oxide powders have been mechanically processed by ball milling. A tetragonal-to-monoclinic phase transition occurred, accompanied by a refinement of the microstructure, and an increase in the dislocation density. The final phase composition, average size of coherent diffraction domains and dislocation density are comparable to those obtained after high-pressure torsion. This suggests that powder particles experience similar mechanical deformation conditions when involved in a collision or submitted to high-pressure torsion.

339

Evaluation of Low Pressure Fogging System for Improving Crop Yield of Tomato (Lycopersicon esculentum Mill.: Grown under Heat Stress Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available In Mediterranean regions, many tomato plants are grown throughout the hot summer period (May–September in sheltered cultivation, mainly for plant protection reasons. Most of the shelters that are used are low cost net houses covered with 50 mesh insect proof net. In most cases these net houses have a flat roof and no ventilation or climate control measures. This insufficient ventilation during the hot summer leads to above optimal air temperatures and causes moderate heat stress inside the shelters, which leads to yield reduction. The aim of this study was to evaluate the ability of a simple and inexpensive low pressure fogging system installed in a naturally ventilated net house to lower temperatures and improve the yield during the summer. The study showed that in areas where relative air humidity (RH during the daytime is less than 60%, tomato plants improved their performance when grown through the summer in net houses under moderate heat stress. Under fogging conditions pollen grain viability and fruit set were significantly improved. This improvement influenced the yield picked during September (104–136 DAP. However, total seasonal yield was not affected by the fogging treatment.

Kobi Shilo

2013-06-01

340

Spatial-Temporal Patterns in a Dielectric Barrier Discharge under Narrow Boundary Conditions in Argon at Atmospheric Pressure  

International Nuclear Information System (INIS)

Pattern formation phenomena are investigated in a dielectric barrier discharge under narrow boundary conditions in argon at atmospheric pressure. The discharge shows various scenarios with the increasing applied voltage. This is the first observation of alternating single spot and pair spots pattern and of a moving striation pattern in a dielectric barrier discharge system. The spatial-temporal correlations between discharge filaments in these patterns are measured by an optical method. The results show that the zigzag pattern is an interleaving of two sub-structure patterns, which ignites once for each sub-pattern per half cycle of the applied voltage. There is a temporal sequence inversion in consecutive half-cycles for the two sub-patterns. The pattern of alternating single spot and pair spots is also an interleaving of two sub-structure patterns. However, the pair spots sub-pattern ignites twice and the single spot sub-pattern ignites once per half cycle of the applied voltage. (physics of gases, plasmas, and electric discharges)

341

Numerical investigation of the spray-mesh-turbulence interactions for high-pressure, evaporating sprays at engine conditions  

International Nuclear Information System (INIS)

This work presents a numerical methodology to simulate evaporating, high pressure Diesel sprays using the Eulerian-Lagrangian approach. Specific sub-models were developed to describe the liquid spray injection and breakup, and the influence of the liquid jet on the turbulence viscosity in the vicinity of the nozzle. To reduce the computational time and easily solve the problem of the grid dependency, the possibility to dynamically refine the grid where the fuel-air mixing process takes place was also included. The validity of the proposed approach was firstly verified simulating an evaporating spray in a constant-volume vessel at non-reacting conditions. The availability of a large quantity of experimental data allowed us to investigate in detail the effects of grid size, ambient diffusivity and used spray sub-models. In this way, different guidelines were derived for a successful simulation of the fuel-air mixture formation process. Finally, fuel injection and evaporation were simulated in an optical engine geometry and computed mixture fraction distributions were compared with experimental data.

342

Stability of Hydrogen-Bonded Supramolecular Architecture under High Pressure Conditions: Pressure-Induced Amorphization in Melamine-Boric Acid Adduct  

International Nuclear Information System (INIS)

The effects of high pressure on the structural stability of the melamine-boric acid adduct (C3N6H6 2H3BO3, M 2B), a three-dimensional hydrogen-bonded supramolecular architecture, were studied by in situ synchrotron X-ray diffraction (XRD) and Raman spectroscopy. M 2B exhibited a high compressibility and a strong anisotropic compression, which can be explained by the layerlike crystal packing. Furthermore, evolution of XRD patterns and Raman spectra indicated that the M 2B crystal undergoes a reversible pressure-induced amorphization (PIA) at 18 GPa. The mechanism for the PIA was attributed to the competition between close packing and long-range order. Ab initio calculations were also performed to account for the behavior of hydrogen bonding under high pressure.

343

Valve inlet fluid conditions for pressurizer safety and relief valves for B and W 177-FA and 205-FA plants. Final report  

International Nuclear Information System (INIS)

The overpressurization transients for the Babcock and Wilcox Company's 177- and 205-FA units are reviewed to determine the range of fluid conditions expected at the inlet of pressurizer safety and relief valves. The final Safety Analysis Report, extended high-pressure injection, and cold overpressurization events are considered. The results of this review, presented in the form of tables and graphs, provide input to the PWR utilities in their justification that the fluid conditions under which their valve designs were tested as part of the EPRI PWR Safety and Relief Valve Test Program are representative of those expected in their unit(s)

344

The accuracy of the crystal chemical parameters at high-pressure conditions from single-crystal X-ray diffraction in diamond-anvil cell  

DEFF Research Database (Denmark)

The high-pressure studies have been increasingly applied for the investigation of crystal structures under non ambient-conditions and phase-transition of minerals forming the Earth’s lower crust and upper mantle. The knowledge of the behavior of minerals under non-ambient conditions has important applications also in the materials science as it can provide useful information about the properties and performance of new materials. Over the past decades, the research in this field has been strongly developed due to the advances in computer capabilities and to the technological improvements of X-ray instruments. At the same time, the high-pressure experiments have benefited by the strong improvements on the high-pressure devices, in particular the diamond-anvil cell (DAC). The aim of this research project is to assess the quality of the data obtained by means of the single-crystal X-ray diffraction technique through the study of different mineral phases. The procedure for setting up an experiment under high-pressure conditions, using a single crystal as sample held within a DAC, are presented here with all the details of the in situ measurements at high-pressure conditions. The research project started with a comparison between two different DACs, in order to define the capabilities of one of the most common types of pressure device, the ETH-type DAC. Application examples of data quality analysis have been conducted on pyroxenes (NaInSi2O6, orthoenstatite MgSiO3 and LiCrSi2O6), which are important components of the Earth’s lower crust and upper mantle. In the last part of the thesis, the berthierite sulfosalt (FeSb2S4) was measured under pressure in order to test the data accuracy on a slightly more complicated structure

Periotto, Benedetta

2012-01-01

345

RELAP5 Capability to Predict Pressure Wave Propagation Phenomena in Single- and Two-Phase Flow Conditions  

OpenAIRE

Correct evaluation of the hydrodynamic loads induced by large and rapid pressure waves propagating with the speed of sound along the reactor piping systems and Reactor Pressure Vessel (RPV) is an important and difficult issue of nuclear power plant safety. The pressure shock transients and resulting hydrodynamic loads on the pipes and RPV structures are commonly calculated with one-dimensional thermo-hydraulic system codes such as RELAP5, TRACE, DRAKO and ROLAST. In Sweden, the most widely us...

Lukasz Sokolowski; Zbigniew Koszela

2012-01-01

346

Contrasting P-T conditions recorded in ultramafic high-pressure rocks from the Variscan Schwarzwald (F.R.G.)  

OpenAIRE

This paper presents mineralogical and textural data as well as thermobarometric calculations on ultramafic high-pressure rocks from the Variscan basement of the Schwarzwald (F.R.G.). The rocks form small isolated bodies within low-pressure / high-temperature gneisses and migmatites. The results of this study constrain contrasting P-T evolutions for four garnet-bearing ultramafic high-pressure rocks. Two magnesian garnet-spinal peridotites sampled near the southern margin of the Central...

Kalt, Angelika; Altherr, Rainer; Hanel, Michael

2006-01-01

347

Fuel pellets from biomass: The importance of the pelletizing pressure and its dependency on the processing conditions  

DEFF Research Database (Denmark)

The aim of the present study was to identify the key factors affecting the pelletizing pressure in biomass pelletization processes. The impact of raw material type, pellet length, temperature, moisture content and particle size on the pressure build up in the press channel of a pellet mill was studied using a single pellet press unit. It was shown that the pelletizing pressure increased exponentially with the pellet length. The rate of increase was dependent on biomass species, temperature, moisture content and particle size. A mathematical model, predicting the pelletizing pressure, was in good accordance with experimental data. It was shown that increasing the temperature resulted in a decrease of the pelletizing pressure. Infrared spectra taken from the pellets surface, indicated hydrophobic extractives on the pellet surface, for pellets produced at higher temperatures. The extractives act as lubricants, lowering the friction between the biomass and the press channel walls. The effect of moisture content on the pelletizing pressure was dependent on the raw material species. Different particle size fractions, from below 0.5 mm up to 2.8 mm diameter, were tested, and it was shown that the pelletizing pressure increased with decreasing particle size. The impact of pelletizing pressure on pellet density was determined, and it was shown that a pelletizing pressure above 200 MPa resulted only in minor increase in pellet density. 2011 Published by Elsevier Ltd.

Stelte, Wolfgang; Holm, Jens K.

2011-01-01

348

Novel States in Magnetic Materials under Extreme Conditions: A High Pressure Neutron Scattering Study of the Shastry-Sutherland compound SrCu2(BO3)2  

OpenAIRE

This thesis is at the crossing point of dierent elds: Quantum Magnetism which studies the collective properties of low spin systems, Neutron Scattering a powerful technique that enables to probe the microscopic properties of matter, and High Pressure where the use of ultra hard materials allows discoveries in a previously unexplored range. Combining these, we shall search for novel states in magnetic materials under extreme conditions. The extreme conditions are the quantum spin s=1/2, the lo...

Zayed, Mohamed

2010-01-01

349

CAN A PLANTAR PRESSURE-BASED TONGUE-PLACED ELECTROTACTILE BIOFEEDBACK IMPROVE POSTURAL CONTROL UNDER ALTERED VESTIBULAR AND NECK PROPRIOCEPTIVE CONDITIONS?  

OpenAIRE

We investigated the effects of a plantar pressure-based tongue-placed electrotactile biofeedback on postural control during quiet standing under normal and altered vestibular and neck proprioceptive conditions. To achieve this goal, fourteen young healthy adults were asked to stand upright as immobile as possible with their eyes closed in two Neutral and Extended head postures and two conditions of No-biofeedback and Biofeedback. The underlying principle of the biofeedback c...

Vuillerme, Nicolas; Chenu, Olivier; Pinsault, Nicolas; Fleury, Anthony; Demongeot, Jacques; Payan, Yohan

2008-01-01

350

Desaturation of a clay-stone around a ventilated gallery: numerical modelling of pressures and water contents under various conditions  

International Nuclear Information System (INIS)

Document available in extended abstract form only. We present simulation tests focusing on the drying process around a gallery in an initially saturated (water-filled) porous clay rock, in the framework of a research on the isolation properties and hydro-mechanical behaviour of a clayey geologic repository for radioactive waste. The saturated/unsaturated hydrodynamic parameters used in these tests correspond to a hypothetical clay-stone, similar to the 130 m thick Callovo-Oxfordian formation located between depths 400 m and 600 m at the Meuse / Haute-Marne (MHM) Underground Research Laboratory (URL), operated by ANDRA (Bure, France). The simulations tests were designed according to 3 'types' of computational geometries. The drying period was extended to very long time scales in some cases. The clay rock was taken homogeneous in many tests, but the damaged zone was represented in some (Type III) tests. Type (I) tests are conducted in a simplified non circular geometry. Assuming a square cross-section for the drift, the drying process is obtained by imposing a fixed suction on a flat piece of wall at the roof. The bottom of the porous domain coincides with the roof of the drift. The imposed suction at the roof affects the near field pressure both horizontally and vertically. Type (II) tests reproduce the circular cylindrical geometry of a partially or perfectly filled gallery, with drying conditions imposed at both ends of the drift. Finally, Type (III) tests consider trift. Finally, Type (III) tests consider the case of an empty ventilated cylindrical drift with circular cross-section. In this case the drying is imposed on the curved walls of the drift via a transmission mechanism thanks the 'macro-porous immersion' method. In all cases, the drying of the porous clay rock is modeled by imposing a suction condition (?), obtained from relative air humidity (HR) via Kelvin's law (?). Briefly, the macro-porous immersion method consists in the following interrelated procedures. First, the volumetric excavation (cylindrical drift) is discretized and internalized as a 3D 'macro-porous' body within the computational porous domain. Secondly, the properties of this internal macro-porous body are adjusted in such a way that it will transmit properly the imposed suction (or pressure, or flux, as the case may be) from external to internal boundaries. Here, the suction is imposed on the entry face of the gallery (external boundary), and it is transmitted to the clay/gallery interface (internal boundary). The macro-porous body has a porosity of 100%, a large Darcy permeability compared to the clay-stone, and other special nonlinear and non-isotropic unsaturated properties. Briefly, numerical modelling was conducted with BIGFLOW 3D, an implicit finite volume solver of the saturated/unsaturated Richards equation in mixed form (moisture content '?', pressure head 'h'). We used the nonlinear Van Genuchten / Mualem conductivity and water retention curves (K(h); ?(h)) in the unsaturated zone. A specific elastic storativity (SS) was added in the saturated zone to take into account slight deformation mechanisms in a simplified way (the storativity model does not deal with total stress; it assumes ??EFF ? ?p, where p is pore pressure, and ?EFF is Terzaghi's effective stress taken positive when extensional). Finally, the BIGFLOW code can also handle 3D heterogeneity and nonlinear diagonal anisotropy, that is: [Kii(h,x,y,z); ?(h,x,y,z)]. We used these additional capabilities of the code in some of the tests. Figs.1 and 2 show the evolution of desaturation for a 'Type I' test, i.e., with suction imposed on a flat horizontal piece of wall located at the roof of the drift. The drift 'radius' (half-side) is R=2 m. The case shown here is only 'moderately dry': the prescribed suction is ?=3000 m (?30 MPa), corresponding to HR=80.74% at TAIR=25 C and PATM=1 bar (according to Kelvin's law). The imposed desaturation of the porous medium at the drift wall is significant (more than 50% drop of the degree of saturation). The steady state is atta

351

Description of a disposition line on the stress corrosion cracking behaviour of ferritic reactor pressure vessel steels under BWR-conditions  

International Nuclear Information System (INIS)

The inner surface of the reactor pressure vessel of BWR reactors is lined with a welded, corrosion-resistant steel liner. In an assumed case of liner rupture down to the low-alloy ferritic base material, an integrity assessment of the pressure vesssel in consideration of the effects of reactor coolant is of utmost importance, and research in this field has been going on for more than ten years now. An analysis of the available data shows that it is now possible to describe a disposition line on the stress corrosion cracking behaviour of ferritic reactor pressure vessel steels in BWR conditions. Crack growth rates of a stress intensity factor corresponding to a T/4 wall defect (i.e. 25 percent of the wall thickness) are technically not relevant. This scientific finding is supported by measurements of about 450 reactor operation years of all German LWR reactor plants, none of which showed crack initiation in the reactor pressure vessel

352

Modeling of high pressure steam condensation in the presence of a noncondensable gas in a vertical tube with a secondary pool condition  

Energy Technology Data Exchange (ETDEWEB)

An improved theoretical model was developed to investigate the effects of noncondensable gas on the heat transfer coefficient of steam condensing inside a vertical tube using the heat and mass transfer analogy with a secondary pool condition. The model predicted well the experimental data of Oh and Rebankar (2006) and Kim (2000), which had been obtained from the in-tube steam condensation submerged in water pool with air. A parametric study was performed with the system pressure and condenser tube diameter as parameters. Results show that total and overall heat transfer coefficients decreased as the system pressure and the condenser tube diameter increased in low pressure, but they became saturated in high pressure. (authors)

Kwon-Yeong, Lee; Moo Hwan, Kim [Pohang Univ. of Science and Technology, Mechanical Engineering Dept. (Korea, Republic of)

2007-07-01

353

Hydrogen transfer hydrocracking of C. procera latex under ambient pressure conditions to get value added chemicals and fuels  

Energy Technology Data Exchange (ETDEWEB)

Biomass is renewable source of energy while the reserves of petroleum are being depleted. The latex of a potential petrocrop, Calotropis procera, a laticifer, arid-plant which is rich in hydrocarbon type triterpene compounds etc. was found to be a better feed stock for thermal hydrocracking as compared to whole plant biomass in terms of liquid product yield. Studies of chemical reaction dynamics of the thermal cracking of latex at 200-400[degree]C showed that the process should be termed as hydrogen-transfer (H-T) hydrocracking of latex under ambient pressure conditions. The hydrogen rich cracked triterpenoids act as the H-donors in this process, where nascent hydrogen atoms and free radicals chemically plug the cracked moieties to stabilise these. Latex was also coagulated and the H-T hydrocracking of the feedstock coagulum gave a higher yield of cracked oil in comparison to that from the dried latex. The temperature for hydrocracking of latex has been optimized to 350[degree]C and molecular sieve was found to catalyse the H-T hydrocracking process to yield more liquid product. The distillation range of cracked latex oil (CLO) obtained from H-T hydrocracking of C. procera latex indicated that it can be used as fuel oil or substitute for diesel fuel. Moreover, CLO resembled diesel fuels and was predominantly paraffinic in nature as characterised by NMR and FTIR spectral analysis. A process has been recommended for getting value added fuels and chemicals from C. procera latex. 29 refs., 5 figs., 3 tabs.

Sharma, D.K.; Behera, B.K.; Arora, M. (Indian Institute of Technology, New Delhi (India). Fuels and Biofuels Engineering Lab.)

1994-01-01

354

Surface charging patterns of stainless alloys - Effect of ageing in conditions of primary cooling circuit of pressurized water reactors  

Energy Technology Data Exchange (ETDEWEB)

The predominance of electrostatic interactions in the mechanism of particle deposition onto solid surfaces is well documented. Therefore, an electrostatic approach has been used to predict the behavior of activated corrosion products in the primary cooling circuit of a pressurized water reactor (PWR). Only few results have been published on the potential at the interface of metallic alloys and aqueous solutions, even at room temperature. In this study, we present results about the characterization of representative materials such as Inconel 690, stainless steel 304 and Zircaloy 4 at room temperature, for pristine polished samples as well as after an 80-day ageing step in physico-chemical conditions similar to those of a primary circuit (360 Degree-Sign C, boron 1 g L{sup -1} (as H{sub 3}BO{sub 3}), lithium 2 mg L{sup -1} (as LiOH), hydrogen 30 cm{sup 3} kg{sup -1}). The surface potentials of these alloys have been determined using a streaming current method for pH from 3 to 7. Isoelectric points between 4.1 and 4.6 have been found for all samples and there is no effect of the ageing step. These values have been confirmed by adhesion studies of grafted latex particles either positively charged (amidine surface groups) or negatively charged (carboxylate groups) at pH 3.3 and pH 5.5. The results show that particles deposition is favored only when they carry a charge opposite to the substrate surfaces.

Martin Cabanas, B. [EDF R and D Les Renardieres, Departement MMC, Avenue de Sens, Ecuelles, 77818 Moret/Loing Cedex (France); Luetzenkirchen, J. [Institute for Nuclear Waste Disposal (INE), Karlsruhe Institute for Technology (KIT), P.O. Box 3640, 76021 Karlsruhe (Germany); Leclercq, S. [EDF R and D Les Renardieres, Departement MMC, Avenue de Sens, Ecuelles, 77818 Moret/Loing Cedex (France); Barboux, P. [Chimie ParisTech, UMR 7574 LCMCP, 11 rue Pierre et Marie Curie, 75005 Paris (France); Lefevre, G., E-mail: gregory-lefevre@chimie-paristech.fr [Chimie ParisTech, UMR 7575 LECIME, 11 rue Pierre et Marie Curie, 75005 Paris (France)

2012-11-15

355

Effects of storage conditions before or after high-hydrostatic pressure on inactivation of Vibrio parahaemolyticus and Vibrio vulnificus in oysters  

Science.gov (United States)

The effect of storage conditions on subsequent high-hydrostatic pressure (HHP) inactivation of V. parahaemolyticus and V. vulnificus in oyster meat was investigated. Live oysters were inoculated with V. parahaemolyticus or V. vulnificus to ca. 7-8 log MPN/g by feeding and stored at different conditi...

356

Stability and catalytic activity of alpha-amylase from barley malt at different pressure-temperature conditions.  

Science.gov (United States)

The impact of high hydrostatic pressure and temperature on the stability and catalytic activity of alpha-amylase from barley malt has been investigated. Inactivation experiments with alpha-amylase in the presence and absence of calcium ions have been carried out under combined pressure-temperature treatments in the range of 0.1-800 MPa and 30-75 degrees C. A stabilizing effect of Ca(2+) ions on the enzyme was found at all pressure-temperature combinations investigated. Kinetic analysis showed deviations of simple first-order reactions which were attributed to the presence of isoenzyme fractions. Polynomial models were used to describe the pressure-temperature dependence of the inactivation rate constants. Derived from that, pressure-temperature isokinetic diagrams were constructed, indicating synergistic and antagonistic effects of pressure and temperature on the inactivation of alpha-amylase. Pressure up to 200 MPa significantly stabilized the enzyme against temperature-induced inactivation. On the other hand, pressure also hampers the catalytic activity of alpha-amylase and a progressive deceleration of the conversion rate was detected at all temperatures investigated. However, for the overall reaction of blocked p-nitrophenyl maltoheptaoside cleavage and simultaneous occurring enzyme inactivation in ACES buffer (0.1 M, pH 5.6, 3.8 mM CaCl(2)), a maximum of substrate cleavage was identified at 152 MPa and 64 degrees C, yielding approximately 25% higher substrate conversion after 30 min, as compared to the maximum at ambient pressure and 59 degrees C. PMID:17013936

Buckow, Roman; Weiss, Ulrike; Heinz, Volker; Knorr, Dietrich

2007-05-01

357

The influence of meteorological conditions on the side effects of contrast media during infusion urograms  

International Nuclear Information System (INIS)

A relationship between certain weather conditions and the frequency of some diseases has been recognised for a long time. During a period of two and a quarter years, the course of infusion urograms in 6862 patients was carefully monitored. At the same time, records were kept of the weather, including the general weather situation, changes in the weather, its dynamics, atmospheric pressure and 'vorticity'. 7.96% of patients showed side effects from the contrast medium. 32.6% of all patients admitted to having been affected by the weather, with an incidence of side effects of 9.7%. Older patients and over-weight patients tended to suffer fewer side effects. There was no correlation with the seasons. As regards the general weather situation, there was an increased incidence associated with changes coming from the east, fewer incidents during the in-flow of cold air and high pressure situations. There were marked differences during periods of high and low pressure ('vorticity'). High pressure situations and periods of increasing barometric pressure had complication rates of 5.3% and 4.7% respectively, low pressure, 11%. Statistical analysis showed no significant difference between the groups, but tendencies were unmistakable. A large number of individual factors are known to have an effect, such as abnormalities of the complement system, antigen-antibody reactions and others, but the importance of each factor remains uncertain. The present results indicate that the reactie present results indicate that the reaction of a patient at the moment of the investigation also plays a significant part. (org.)

358

Distribution of principal elements and impurities in niobium and tantalum carbonitrides synthesized under high pressure and temperature conditions  

International Nuclear Information System (INIS)

Element distribution in niobium and tantalum carbonitride samples, synthesized under the effect of high pressures up to 7.0 GPa and temperatures up to 2000 K, has been determined. Segregation of the main elements over grain boundaries is detected in niobium and tantalum carbonitrides, synthesized under high pressures and temperatures not using protective containers. The segregations of Fe, W, Ca impurities are of a local character both over the grain boundary and in the grain body

359

Iron reduction by the deep-sea bacterium Shewanella profunda LT13a under subsurface pressure and temperature conditions  

Science.gov (United States)

Microorganisms influence biogeochemical cycles from the surface down to the depths of the continental rocks and oceanic basaltic crust. Due to the poor recovery of microbial isolates from the deep subsurface, the influence of physical environmental parameters, such as pressure and temperature, on the physiology and metabolic potential of subsurface inhabitants is not well constrained. We evaluated Fe(III) reduction rates (FeRRs) and viability, measured as colony-forming ability, of the deep-sea piezophilic bacterium Shewanella profunda LT13a over a range of pressures (0–125 MPa) and temperatures (4–37?C) that included the in situ habitat of the bacterium isolated from deep-sea sediments at 4500 m depth below sea level. S. profunda LT13a was active at all temperatures investigated and at pressures up to 120 MPa at 30?C, suggesting that it is well adapted to deep-sea and deep sedimentary environments. Average initial cellular FeRRs only slightly decreased with increasing pressure until activity stopped, suggesting that the respiratory chain was not immediately affected upon the application of pressure. We hypothesize that, as pressure increases, the increased energy demand for cell maintenance is not fulfilled, thus leading to a decrease in viability. This study opens up perspectives about energy requirements of cells in the deep subsurface. PMID:25653646

Picard, Aude; Testemale, Denis; Wagenknecht, Laura; Hazael, Rachael; Daniel, Isabelle

2015-01-01

360

Heat transfer parameters for glass-peened calandria tube in pressure tube and calandria tube contact conditions  

International Nuclear Information System (INIS)

During a postulated event of large LOCA in CANDU reactors, the pressure tube may balloon to contact with its surrounding calandria tube to transfer heat to the moderator. To confirm the integrity of the fuel channel after the contact with a given moderator subcooling, many experiments have been performed in the last three decades by applying different pressure tube heatup rates, different pressure tube pressures and different moderator subcoolings for calandria tubes with smooth outer surface and glass-peened surface. A concept of Equivalent Moderator Subcooling (EMS) has been put forward to determine integrity of fuel channel upon pressure tube/calandria tube contact based on the existing experiment results. This concept has been presented in another work. In this work, the contact thermal conductance between pressure tube and calandria tube, critical heat flux, minimum film boiling temperature, empirical methods for nucleate boiling and film boiling heat transfer coefficient on the glass-peened calandria tube surface are discussed and estimated based on some experimental results and the EMS concept. These parameters are confirmed by simulating the existing experiments using a computer code. The estimated results may help detailed analyses on fuel channel integrity upon PT/CT contact if necessary. (author)

361

Note: Achieving quasi-hydrostatic conditions in large-volume toroidal anvils for neutron scattering to pressures of up to 18 GPa  

Science.gov (United States)

We present developments that allow neutron-scattering experiments to be performed, with both single-crystal and powder samples, under quasi-hydrostatic conditions to pressures beyond previous limits. Samples of sodium chloride and squaric acid (H2C4O4) have been loaded with argon as the pressure-transmitting medium in encapsulated gaskets redesigned for double-toroidal anvils, using a gas-loading method at ambient temperature. These samples have been compressed up to 18 GPa in a Paris-Edinburgh press, and no evidence of peak broadening in either the single-crystal or the powder experiments was observed.

Bull, C. L.; Bocian, A.; Hamidov, H.; Kamenev, K. V.; Nelmes, R. J.; Loveday, J. S.

2011-07-01

362

Can a plantar pressure-based tongue-placed electrotactile biofeedback improve postural control under altered vestibular and neck proprioceptive conditions?  

Science.gov (United States)

We investigated the effects of a plantar pressure-based tongue-placed electrotactile biofeedback on postural control during quiet standing under normal and altered vestibular and neck proprioceptive conditions. To achieve this goal, 14 young healthy adults were asked to stand upright as immobile as possible with their eyes closed in two Neutral and Extended head postures and two conditions of No-biofeedback and Biofeedback. The underlying principle of the biofeedback consisted of providing supplementary information related to foot sole pressure distribution through a wireless embedded tongue-placed tactile output device. Center of foot pressure (CoP) displacements were recorded using a plantar pressure data acquisition system. Results showed that (1) the Extended head posture yielded increased CoP displacements relative to the Neutral head posture in the No-biofeedback condition, with a greater effect along the anteroposterior than mediolateral axis, whereas (2) no significant difference between the two Neutral and Extended head postures was observed in the Biofeedback condition. The present findings suggested that the availability of the plantar pressure-based tongue-placed electrotactile biofeedback allowed the subjects to suppress the destabilizing effect induced by the disruption of vestibular and neck proprioceptive inputs associated with the head extended posture. These results are discussed according to the sensory re-weighting hypothesis, whereby the CNS would dynamically and selectively adjust the relative contributions of sensory inputs (i.e. the sensory weights) to maintain upright stance depending on the sensory contexts and the neuromuscular constraints acting on the subject. PMID:18597943

Vuillerme, N; Chenu, O; Pinsault, N; Fleury, A; Demongeot, J; Payan, Y

2008-07-31

363

Asthma and climatic conditions: experience from Bermuda, an isolated island community.  

OpenAIRE

A retrospective study of patients attending the emergency department with acute asthma was performed in Bermuda. Climatic data (barometric pressure, rainfall, humidity, and wind strength and direction) were obtained and compared with frequency of exacerbations of asthma. Three factors--namely, relative humidity, average daily temperature, and northeasterly winds--were found to be related to worsening asthma. Owing to Bermuda's lack of pollution and aeroallergens it was thought that these weat...

Carey, M. J.; Cordon, I.

1986-01-01

364

RELAP5 Capability to Predict Pressure Wave Propagation Phenomena in Single- and Two-Phase Flow Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Correct evaluation of the hydrodynamic loads induced by large and rapid pressure waves propagating with the speed of sound along the reactor piping systems and Reactor Pressure Vessel (RPV is an important and difficult issue of nuclear power plant safety. The pressure shock transients and resulting hydrodynamic loads on the pipes and RPV structures are commonly calculated with one-dimensional thermo-hydraulic system codes such as RELAP5, TRACE, DRAKO and ROLAST. In Sweden, the most widely used computer code for this purpose is RELAP5. This code needs, therefore, to be assessed for its capability to predict pressure wave behavior. The conducted assessment involves simulations of single- and two-phase shock-tube problems and two-phase blowdown as well as water hammer experiments. The performed numerical experiments clearly show that RELAP5, with the proper time step and spatial mesh size, is capable of predicting the complex dynamics of single- and two-phase pressure wave phenomena with good to reasonable accuracy.

Lukasz Sokolowski

2012-01-01

365

Real-time optical monitoring of ammonia flow and decomposition kinetics under high-pressure chemical vapor deposition conditions  

Science.gov (United States)

Understanding the gas phase decomposition kinetics of the chemical precursors involved in the nucleation and thin-film growth processes is crucial for controlling the surface kinetics and the growth process. The growth of emerging materials such as InN and related alloys requires deposition methods operating at elevated vapor densities due to the high thermal decomposition pressure of these materials. High nitrogen overpressure has been demonstrated to suppress the thermal decomposition of InN, but has so far not been explored in chemical vapor deposition experiments. In this contribution we present research results on the decomposition kinetics of ammonia in the laminar flow regime of a high-pressure flow channel reactor. Ultraviolet absorption spectroscopy is applied to analyze absorption features of ammonia with respect to the ammonia flow rate during continuous flow and pulsed ammonia injection. Pulsed ammonia injection has been used to analyze the average gas flow velocity in the high-pressure chemical vapor deposition system as a function of the total gas flow rate and the reactor pressure. The onset of the kinetics related to the decomposition of ammonia was found to start above 900 K and showed a marked decrease for higher reactor pressures, thus decreasing the discrepancy of trimethylindium and ammonia decomposition temperatures.

Dietz, Nikolaus; Straßburg, Martin; Woods, Vincent

2005-07-01

366

Predicting crystal structures and properties of matter under extreme conditions via quantum mechanics: the pressure is on.  

Science.gov (United States)

Experimental studies of compressed matter are now routinely conducted at pressures exceeding 1 mln atm (100 GPa) and occasionally at pressures greater than 10 mln atm (1 TPa). The structure and properties of solids that have been so significantly squeezed differ considerably from those of solids at ambient pressure (1 atm), often leading to new and unexpected physics. Chemical reactivity is also substantially altered in the extreme pressure regime. In this feature paper we describe how synergy between theory and experiment can pave the road towards new experimental discoveries. Because chemical rules-of-thumb established at 1 atm often fail to predict the structures of solids under high pressure, automated crystal structure prediction (CSP) methods are increasingly employed. After outlining the most important CSP techniques, we showcase a few examples from the recent literature that exemplify just how useful theory can be as an aid in the interpretation of experimental data, describe exciting theoretical predictions that are guiding experiment, and discuss when the computational methods that are currently routinely employed fail. Finally, we forecast important problems that will be targeted by theory as theoretical methods undergo rapid development, along with the simultaneous increase of computational power. PMID:25427780

Zurek, Eva; Grochala, Wojciech

2015-02-01

367

Self-overcoming of the boiling condition by pressure increment in a water target irradiated by proton beam  

Energy Technology Data Exchange (ETDEWEB)

An experiment was conducted to examine and visualize the boiling phenomena inside a water target by irradiating it with a proton beam from MC-50 cyclotron. The boiling phenomena were recorded with a CMOS camera. While an increase of the fraction of the water vapor volume is generally considered to be normal when water is boiled by a proton beam, our experiment showed the opposite result. The volume expansion of the liquid water exceeded the compressibility of the initial air volume. A grid structure in front of the entrance window foil held the target volume constant. Therefore, the phenomena inside the target underwent an isochoric process, and the pressure inside the target was increased rapidly beyond the pressure at the boiling point. Consequently, there was no more bulk boiling in the Bragg-peak region in the target water. Our results show that the boiling of the water can be controlled by controlling the equilibrium pressure of the water target.

Hong, Bong Hwan, E-mail: burnn@kirams.re.kr [Korea Institute of Radiological and Medical Sciences (KIRMAS), 75 Nowon-Gil, Nowon-Gu, Seoul 139-706 (Korea, Republic of); Kang, Joonsun; Jung, In Su; Ram, Han Ga; Park, Yeun Soo [Korea Institute of Radiological and Medical Sciences (KIRMAS), 75 Nowon-Gil, Nowon-Gu, Seoul 139-706 (Korea, Republic of); Cho, Hyung Hee [Department of Mechanical Engineering, Yonsei University, 134 Sinchon-Dong, Seodaemun-Gu, Seoul 120-749 (Korea, Republic of)

2013-11-11

368

Self-overcoming of the boiling condition by pressure increment in a water target irradiated by proton beam  

International Nuclear Information System (INIS)

An experiment was conducted to examine and visualize the boiling phenomena inside a water target by irradiating it with a proton beam from MC-50 cyclotron. The boiling phenomena were recorded with a CMOS camera. While an increase of the fraction of the water vapor volume is generally considered to be normal when water is boiled by a proton beam, our experiment showed the opposite result. The volume expansion of the liquid water exceeded the compressibility of the initial air volume. A grid structure in front of the entrance window foil held the target volume constant. Therefore, the phenomena inside the target underwent an isochoric process, and the pressure inside the target was increased rapidly beyond the pressure at the boiling point. Consequently, there was no more bulk boiling in the Bragg-peak region in the target water. Our results show that the boiling of the water can be controlled by controlling the equilibrium pressure of the water target

369

Self-overcoming of the boiling condition by pressure increment in a water target irradiated by proton beam  

Science.gov (United States)

An experiment was conducted to examine and visualize the boiling phenomena inside a water target by irradiating it with a proton beam from MC-50 cyclotron. The boiling phenomena were recorded with a CMOS camera. While an increase of the fraction of the water vapor volume is generally considered to be normal when water is boiled by a proton beam, our experiment showed the opposite result. The volume expansion of the liquid water exceeded the compressibility of the initial air volume. A grid structure in front of the entrance window foil held the target volume constant. Therefore, the phenomena inside the target underwent an isochoric process, and the pressure inside the target was increased rapidly beyond the pressure at the boiling point. Consequently, there was no more bulk boiling in the Bragg-peak region in the target water. Our results show that the boiling of the water can be controlled by controlling the equilibrium pressure of the water target.

Hong, Bong Hwan; Kang, Joonsun; Jung, In Su; Ram, Han Ga; Park, Yeun Soo; Cho, Hyung Hee

2013-11-01

370

Pulsed laser ablation plasmas generated in CO2 under high-pressure conditions up to supercritical fluid  

International Nuclear Information System (INIS)

Pulsed laser ablation of solids in supercritical media has a large potential for nanomaterials fabrication. We investigated plasmas generated by pulsed laser ablation of Ni targets in CO2 at pressures ranging from 0.1 to 16 MPa at 304.5 K. Plasma species were characterized by optical emission spectroscopy, and the evolution of cavitation bubbles and shockwaves were observed by time-resolved shadowgraph imaging. Ni and O atomic emissions decreased with increasing gas pressure; however, near the critical point the intensities reached local maxima, probably due to the enhancement of the plasma excitation and effective quenching resulting from the large density fluctuation.

371

Operational measures. Influence of the operational conditions of EDF's PWR reactors on the flux the pressure vessels receive  

International Nuclear Information System (INIS)

The developments in fuel management for the REP-900 park have led to no substantial increase of the flux density on the pressure vessel. From the end of 1992, taking the safety parameters into account, loading diagrams with reduced flux density for UO2 fuel have been used. These are also meant to be utilised for MOX fuel. In the REP 1130, the lengthening of the cycle time with simultaneous lowering of the flux density seems possible. The flux density effect on the pressure vessel and on the radiation samples is constantly being followed. 2 figs., 1 tab

372

Pressurant requirements for discharge of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank under both static and slosh conditions  

Science.gov (United States)

Pressurized expulsion tests were conducted to determine the effect of various physical parameters on the pressurant gas (methane, helium, hydrogen, and nitrogen) requirements during the expulsion of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank and to compare results with those predicted by an analytical program. Also studied were the effects on methane, helium, and hydrogen pressurant requirements of various slosh excitation frequencies and amplitudes, both with and without slosh suppressing baffles in the tank. The experimental results when using gaseous methane, helium, and hydrogen show that the predictions of the analytical program agreed well with the actual pressurant requirements for static tank expulsions. The analytical program could not be used for gaseous nitrogen expulsions because of the large quantities of nitrogen which can dissolve in liquid methane. Under slosh conditions, a pronounced increase in gaseous methane requirements was observed relative to results obtained for the static tank expulsions. Slight decreases in the helium and hydrogen requirements were noted under similar test conditions.

Dewitt, R. L.; Mcintire, T. O.

1974-01-01

373

Macroscopic electric field and osmotic pressure in ultracentrifugal sedimentation diffusion equilibria of charged colloids  

Science.gov (United States)

Sedimentation-diffusion (SD) equilibria from analytical ultracentrifugation of well-characterized charged silica spheres in ethanol deviate strongly from a barometric profile and demonstrate the existence and substantial effects of a recently predicted internal macroscopic electric field (van Roij 2003 J. Phys.: Condens. Matter 15 S3569). Experimental SD-profiles yield the gradient of the electrostatic potential energy of the colloids, which clearly manifests an almost homogeneous macroscopic electric field. Electrochemical Donnan potential measurements confirm a difference in electrical potential between the top and bottom of the profiles. A 'non-barometric' limiting law derived from electroneutrality explains the trends in the SD-profiles quite well. Our analysis of osmotic pressures (obtained from integrating SD-profiles) beyond this simple law includes, among other things, colloid-ion attractions and extra volume terms in the free energy.

Rasa, M.; Erné, B. H.; Zoetekouw, B.; van Roij, R.; Philipse, A. P.

2005-04-01

374

Macroscopic electric field and osmotic pressure in ultracentrifugal sedimentation-diffusion equilibria of charged colloids  

International Nuclear Information System (INIS)

Sedimentation-diffusion (SD) equilibria from analytical ultracentrifugation of well-characterized charged silica spheres in ethanol deviate strongly from a barometric profile and demonstrate the existence and substantial effects of a recently predicted internal macroscopic electric field (van Roij 2003 J. Phys.: Condens. Matter 15 S3569). Experimental SD-profiles yield the gradient of the electrostatic potential energy of the colloids, which clearly manifests an almost homogeneous macroscopic electric field. Electrochemical Donnan potential measurements confirm a difference in electrical potential between the top and bottom of the profiles. A 'non-barometric' limiting law derived from electroneutrality explains the trends in the SD-profiles quite well. Our analysis of osmotic pressures (obtained from integrating SD-profiles) beyond this simple law includes, among other things, colloid-ion attractions and extra volume terms in the free energy

375

Pressure measurements in G-Tunnel  

International Nuclear Information System (INIS)

Transport of water in an unsaturated medium such as the proposed study site at Yucca Mountain, Nevada is very likely to be two-phase: vapor (or steam) and liquid water. Determination of partial vapor pressure in the medium is therefore desired for a model study of the transport mechanism. In this prototype test in G-Tunnel, the author commits to measure the relative humidity and moisture content of the rock around the heater. To determine the partial vapor pressure in the rock, he also needs to determine the total pressure in the medium. For that purpose, he decided to measure the pore-air (include steam or vapor) pressure in the boreholes where relative humidity will be determined (P1, P2, and P3). The total pore-air pressure will be measured by using a strain-gaged pressure transducer. Other purposes of this test are to try the pressure measuring technique and to investigate the long-term stability of sensitive pressure transducers. He also measures the barometric pressure in the alcove, outside the boreholes where total pressure is measured

376

Cooldown to residual heat removal entry conditions using atmospheric dump valves and auxiliary pressurizer spray following a loss-of-offsite power at Calvert Cliffs, Unit 1  

International Nuclear Information System (INIS)

An investigation of cooldown using atmospheric dump valves (ADVs) and auxiliary pressurizer spray (APS) following loss-of-offsite power at Calvert Cliffs-1 showed residual heat removal entry conditions could not be reached with the plant ADVs alone. Use of APS with the plant ADVs enhanced depressurization, but still provided insufficient cooldown. Effective cooldown and depressurization was shown to occur when rated steady state flow through the ADVs was increased by a factor of four. 6 refs., 30 figs., 2 tabs

377

Pressure Fluctuations on the Bed of Surge Tank at the H.P. Zimapan, Hgo., with Different Arrangements Studied on Hydraulic Model, with the Lowest Operation Conditions  

OpenAIRE

In this paper, the pressure fluctuations of the surge tank in the Zimapan Hydroelectric Project are compared in a hydraulic model. The shaft is located lateral, over the conduction tunnel and in the simple form (permitting the tunnel entering the shaft), with and without orifice plates taking into account the demand and supply condition of energy with the minimum level of water of the conduction. It was determined the hydraulic efficiency and it was found that it was the best constructive opt...

Marengo–mogollo?n, H.; Ochoa–a?lvarez, F. J.; Corte?s–corte?s, C.

2009-01-01

378

Investigation of the axial dependence of coolant temperature noise at one-phase and two-phase flow conditions in a pressurized water reactor  

International Nuclear Information System (INIS)

Results of the investigation of coolant temperature noise in a pressurized water reactor are presented. The experiments were performed using a specially aquipped fuel assembly in the WWER-70 reactor of the Rheinsberg nuclear power plant. The interpretation of the measuring values is based on a thermohydraulic model which describes the axial dependence of the temperature noise at one-phase and two-phase flow conditions. (author)

379

Uniqueness of specific interfacial area-capillary pressure-saturation relationship under non-equilibrium conditions in two-phase porous media flow  

OpenAIRE

The capillary pressure–saturation (P c–S w) relationship is one of the central constitutive relationships used in two-phase flow simulations. There are two major concerns regarding this relation. These concerns are partially studied in a hypothetical porous medium using a dynamic pore-network model called DYPOSIT, which has been employed and extended for this study: (a) P c–S w relationship is measured empirically under equilibrium conditions. It is then used in Darcy-based simulations ...

Joekar-niasar, V.; Hassanizadeh, S. M.

2012-01-01

380

Analysis of the critical heat flux in round vertical tubes under low pressure and flow oscillation conditions. Applications of artificial neural network  

International Nuclear Information System (INIS)

Artificial neural networks (ANNs) for predicting critical heat flux (CHF) under low pressure and oscillation conditions have been trained successfully for either natural circulation or forced circulation (FC) in the present study. The input parameters of the ANN are pressure, mean mass flow rate, relative amplitude, inlet subcooling, oscillation period and the ratio of the heated length to the diameter of the tube, L/D. The output is a nondimensionalized factor F, which expresses the relative CHF under oscillation conditions. Based on the trained ANN, the influences of principal parameters on F for FC were analyzed. The parametric trends of the CHF under oscillation obtained by the trained ANN are as follows: the effects of pressure below 500 kPa are complex due to the influence of other parameters. F will increase with increasing mean mass flow rate under any conditions, and will decrease generally with an increase in relative amplitude. F will decrease initially and then increase with increasing inlet subcooling. The influence curves of mean mass flow rate on F will be almost the same when the period is shorter than 5.0 s or longer than 15 s. The influence of L/D will be negligible if L/D>200. It is found that the minimum number of neurons in the hidden layer is a product of the number of neurons in the input layer and in the output layer

381

Stability of Anthocyanins from Red Grape Skins under Pressurized Liquid Extraction and Ultrasound-Assisted Extraction Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available The stability of anthocyanins from grape skins after applying different extraction techniques has been determined. The following compounds, previously extracted from real samples, were assessed: delphinidin 3-glucoside, cyanidin 3-glucoside, petunidin 3-glucoside, peonidin 3-glucoside, malvidin 3-glucoside, peonidin 3-acetylglucoside, malvidin 3-acetylglucoside, malvidin 3-caffeoylglucoside, petunidin 3-p-coumaroylglucoside and malvidin 3-p-coumaroylglucoside (trans. The techniques used were ultrasound-assisted extraction and pressurized liquid extraction. In ultrasound-assisted extraction, temperatures up to 75 °C can be applied without degradation of the aforementioned compounds. In pressurized liquid extraction the anthocyanins were found to be stable up to 100 °C. The relative stabilities of both the glycosidic and acylated forms were evaluated. Acylated derivatives were more stable than non-acylated forms. The differences between the two groups of compounds became more marked on working at higher temperatures and on using extraction techniques with higher levels of oxygen in the extraction media.

Ali Liazid

2014-12-01

382

Influence of operating conditions and ammonia injection on the emission of nitrogenous gases from pressurized fluidized bed combustion of coal  

International Nuclear Information System (INIS)

A coal-fired Pressurized Fluidized Bed Combustor at the Delft University of Technology is being used to study fuel conversion and related environmental aspects. This 'semi-technical' scale combustion test rig with an operating pressure up to 10 bar and a maximum thermal capacity of 1,6 MW is being used to investigate environmental aspects of coal combustion like limiting fly ash concentrations in the flue gas by high temperature/high pressure gas cleaning techniques and the influence of fuel related and operation-dependent parameters on the formation and reduction of noxious oxides, in particular nitrogenous species. The fuels investigated so far were anthracites, bituminous coals and brown coals. The influence of different operating parameters such as coal type, freeboard temperature, pressure and excess air on N2O emissions has been investigated and the effect of Selective Non-Catalytic Reduction (SNCR) using ammonia injection in the exhaust of the combustor on the emission of NO, NO2, CO, NH3 and N2O was determined for a number of mol ratios, injection locations and temperatures using 2 British and 2 German coals. Gas concentrations have been determined at different locations of the PFBC test rig, among others in tile freeboard and downstream of the first cyclone using 'conventional' gas analysis instruments, a Gas Chromatograph (GC) and a Fourier Transform InfraRed (FTIR) spectrometer. The paper describes the PFBC test rmeter. The paper describes the PFBC test rig, the ammonia injection system, the sampling systems and the GC and FTIR gas analysis systems. Practical experience gained so far with these measuring systems will be presented and results of the measurements will be given and discussed

383

Kinetic study of the heterogeneous Si/H system under low-pressure plasma conditions by means of mass spectrometry  

International Nuclear Information System (INIS)

The kinetics of the silicon/hydrogen low-pressure discharge system have been measured using a flow technique and mass spectrometry. Results show that at long residence times the system operates under a partial chemical equilibrium even though it is not at thermodynamic equilibrium. The present work indicates that the decisive parameter controlling the structural properties of the deposit (i.e., the formation of either amorphous or microcrystalline silicon) is the departure of the system from the partial chemical equilibrium

384

Theoretical assessment of boron incorporation in nickel ferrite under conditions of operating nuclear pressurized water reactors (PWRs)  

OpenAIRE

A serious concern in the safety and economy of a pressurized water nuclear reactor is related to the accumulation of boron inside the metal oxide (mostly NiFe${}_{2}$O${}_{4}$ spinel) deposits on the upper regions of the fuel rods. Boron, being a potent neutron absorber, can alter the neutron flux causing anomalous shifts and fluctuations in the power output of the reactor core. This phenomenon reduces the operational flexibility of the plant and may force the down-rating of...

Rak, Zs; Bucholz, E. W.; Brenner, D. W.

2014-01-01

385

Application of the statistical safety evaluation method to the small break LOCA with high pressure injection failure. Sensitivity analyses to determine the break conditions  

International Nuclear Information System (INIS)

By applying a statistical safety evaluation method, the uncertainties of best estimate results can be estimated quantitatively, and as a consequence, excessive conservatism can be reasonably removed to obtain evaluation results with enhanced reliability. Application of a statistical evaluation method is being made to analyses of the “low pressure injection by intentional depressurization of the steam generator secondary side” which is an accident management approach in a SBLOCA (small break loss-of-coolant accident) with HPI (high pressure injection) failure. At the time of a SBLOCA, the break conditions such as the break size are important parameters since they influence PCT (peak cladding temperature). In this research, sensitivity analyses about the break size, direction and position were carried out for a system plant under a condition which the start timing of the steam generator secondary side intentional depressurization is severer than an actual abnormal operating condition. From the result of the sensitivity analyses, differences in the phenomena progression which change depending on the break conditions were evaluated, and a 3 inch facing-down break of the cold-leg was determined as the base case of a statistical safety evaluation. (author)

386

Using Atmospheric Pressure Tendency to Optimise Battery Charging in Off-Grid Hybrid Wind-Diesel Systems for Telecoms  

Directory of Open Access Journals (Sweden)

Full Text Available Off grid telecom base stations in developing nations are powered by diesel generators. They are typically oversized and run at a fraction of their rated load for most of their operating lifetime. Running generators at partial load is inefficient and, over time, physically damages the engine. A hybrid configuration uses a battery bank, which powers the telecoms’ load for a portion of the time. The generator only operates when the battery bank needs to be charged. Adding a wind turbine further reduces the generator run hours and saves fuel. The generator is oblivious to the current wind conditions, which leads to simultaneous generator-wind power production. As the batteries become charged by the generator, the wind turbine controller is forced to dump surplus power as heat through a resistive load. This paper details how the relationship between barometric pressure and wind speed can be used to add intelligence to the battery charger. A Simulink model of the system is developed to test the different battery charging configurations. This paper demonstrates that if the battery charger is aware of upcoming wind conditions, it will provide modest fuel savings and reduce generator run hours in small-scale hybrid energy systems.

Stephen Daniels

2013-06-01

387

Synthesis of super-dense phase of aluminum under extreme pressure and temperature conditions created by femtosecond laser pulses in sapphire  

Energy Technology Data Exchange (ETDEWEB)

We describe synthesis of a new super-dense phase of aluminum under extreme pressure and temperature conditions created by laser-induced microexplosions in sapphire. Micro explosions in sub-micrometer sized regions of sapphire were induced by tightly-focused femtosecond laser pulses with a temporal length of {approx} 100 fs and an energy of {approx} 100 nJ. Fast, explosive expansion of photogenerated high-density plasma created strong heating and pressure transients with peak temperature and pressure of {approx} 105 K and 10 TPa, respectively. Partial decomposition of sapphire in the shock-compressed sapphire led to formation of nanocrystalline bcc-Al phase, which is different from ambient fcc-Al phase, and was permanently preserved by fast quenching. The existence of super-dense bcc-Al phase was confirmed using X-ray diffraction technique. This is the first observation of bcc-Al phase, which so far has been only predicted theoretically, and a demonstration that laser-induced micro explosions technique enables simple, safe and cost-efficient access to extreme pressures and temperatures without the tediousness typical to traditional techniques that use diamond anvil cells, gas guns, explosives, or megajoule-class lasers.

Mizeikis, Vygantas; Vailionis, Arturas; Gamaly, Eugene G.; Yang, Wenge; Rode, Andrei V.; Juodkazis, Saulius (Swinburne); (Shizuoka); (Stanford); (CIW); (ANU)

2012-06-26

388

Pore-by-pore capillary pressure measurements using X-ray microtomography at reservoir conditions: Curvature, snap-off, and remobilization of residual CO2  

Science.gov (United States)

microtomography was used to image the shape and size of residual ganglia of supercritical CO2 at resolutions of 3.5 and 2 ?m and at representative subsurface conditions of temperature and pressure. The capillary pressure for each ganglion was found by measuring the curvature of the CO2-brine interface, while the pore structure was parameterized using distance maps of the pore space. The formation of the residual clusters by snap-off was examined by comparing the ganglion capillary pressure to local pore topography. The capillary pressure was found to be inversely proportional to the radius of the largest restriction (throat) surrounding the ganglion, which validates the imbibition mechanisms used in pore-network modeling. The potential mobilization of residual ganglia was assessed using a reformulation of both the capillary (Ncmacro) and Bond numbers (Nbmacro), rigorously based on a balance of pore-scale forces, with the majority of ganglia remobilized at Ncmacro around 1. Buoyancy forces were found to be small in this system (Nbmacro << 1), meaning the gravitational remobilization of CO2 after residual trapping would be extremely difficult.

Andrew, Matthew; Bijeljic, Branko; Blunt, Martin J.

2014-11-01

389

Effects of hydrogen loading conditions on fabrication of long-period fiber-grating sensors by low-pressure mercury lamp  

Science.gov (United States)

Conditions of hydrogen loading were studied for shortening of the exposure time for fabrication of long-period fiber grating sensors using a low-pressure mercury lamp. By an increased hydrogen pressure of 135 atm, shortening of the exposure time to 2/3 that of 120 atm was obtained. By increasing the loading time from 4 to 12 weeks, the exposure time was shortened to 3/4 that of the same pressure, or half that of 120 atm for 3 weeks. The temperature rise of the fiber during exposure was measured to be 16 °C or less. Distribution of hydrogen molecules in the fiber was studied by a numerical analysis solving a diffusion equation. The result of the analysis agreed with the pressure dependence of the measured hydrogen concentration and the exposure time for fabrication. For the longer loading time, neither the calculated nor the measured hydrogen concentrations increased: the shortening of the exposure time by the longer loading time was not explained. The temperature and strain sensitivities were lower than those of hydrogen loading at 120 atm except that a temperature sensitive and strain insensitive long-period grating was obtained with a period of 460 ?m.

Mizunami, Toru; Tashiro, Yoshihisa

2015-01-01

390

In situ phase transition study of nano- and coarse-grained TiO2 under high pressure/temperature conditions  

International Nuclear Information System (INIS)

A comparative phase transition study of nanocrystalline and micro-TiO2 has been conducted under high pressure-temperature (P-T) conditions using energy-dispersive synchrotron x-ray diffraction (XRD). Our study reveals that on compression at room temperature, the micro-tetragonal anatase-type TiO2 started to transform to the orthorhombic columbite-type TiO2 near 1.6 GPa. In contrast, we did not observe this phase transition in nano-anatase at pressures of up to 8.5 GPa. At 8.5 GPa, by applying moderate heat, both samples were transformed completely to columbite-type TiO2 almost simultaneously, indicating that heat treatment could significantly expedite this phase transition. These columbite-type TiO2 phases were quenchable because after cooling them to room temperature and decompressing them to 2.0 GPa, the XRD patterns displayed no changes in comparison with those collected at 8.6 GPa and 1270 K. At 2 GPa, we heated the specimens again, and the rutile-type TiO2 started to emerge around 970 K. This phase was also quenchable after cooling and releasing pressure to ambient conditions. The grain size effects on the phase transition were discussed based on the kinetics mechanism. This study should be of considerable interest to the fields of materials science and condensed matter

391

A versatile elevated-pressure reactor combined with an ultrahigh vacuum surface setup for efficient testing of model and powder catalysts under clean gas-phase conditions  

Energy Technology Data Exchange (ETDEWEB)

A small-volume reaction cell for catalytic or photocatalytic testing of solid materials at pressures up to 1000 Torr has been coupled to a surface-science setup used for standard sample preparation and characterization under ultrahigh vacuum (UHV). The reactor and sample holder designs allow easy sample transfer from/to the UHV chamber, and investigation of both planar and small amounts of powder catalysts under the same conditions. The sample is heated with an infrared laser beam and its temperature is measured with a compact pyrometer. Combined in a regulation loop, this system ensures fast and accurate temperature control as well as clean heating. The reaction products are automatically sampled and analyzed by mass spectrometry and/or gas chromatography (GC). Unlike previous systems, our GC apparatus does not use a recirculation loop and allows working in clean conditions at pressures as low as 1 Torr while detecting partial pressures smaller than 10{sup ?4} Torr. The efficiency and versatility of the reactor are demonstrated in the study of two catalytic systems: butadiene hydrogenation on Pd(100) and CO oxidation over an AuRh/TiO{sub 2} powder catalyst.

Morfin, Franck; Piccolo, Laurent [Institut de recherches sur la catalyse et l' environnement de Lyon (IRCELYON), UMR 5256 CNRS and Université Lyon 1, 2 avenue Albert Einstein, F-69626 Villeurbanne (France)

2013-09-15

392

Isovolumic relaxation period as an index of left ventricular relaxation under different afterload conditions--comparison with the time constant of left ventricular pressure decay in the dog.  

Science.gov (United States)

In order to determine whether isovolumic relaxation period (IRP) reflects left ventricular relaxation under different afterload conditions, 17 anesthetized, open chest dogs were studied, and the left ventricular pressure decay time constant (T) was calculated. In 12 dogs, angiotensin II and nitroprusside were administered, with the heart rate constant at 90 beats/min. Multiple linear regression analysis showed that the aortic dicrotic notch pressure (AoDNP) and T were major determinants of IRP, while left ventricular end-diastolic pressure was a minor determinant. Multiple linear regression analysis, correlating T with IRP and AoDNP, did not further improve the correlation coefficient compared with that between T and IRP. We concluded that correction of the IRP by AoDNP is not necessary to predict T from additional multiple linear regression. The effects of ascending aortic constriction or angiotensin II on IRP were examined in five dogs, after pretreatment with propranolol. Aortic constriction caused a significant decrease in IRP and T, while angiotensin II produced a significant increase in IRP and T. IRP was affected by the change of afterload. However, the IRP and T values were always altered in the same direction. These results demonstrate that IRP is substituted for T and it reflects left ventricular relaxation even in different afterload conditions. We conclude that IRP is a simple parameter easily used to evaluate left ventricular relaxation in clinical situations. PMID:2632821

Ochi, H; Ikuma, I; Toda, H; Shimada, T; Morioka, S; Moriyama, K

1989-12-01

393

Externally controlled pressure and temperature microreactor for in situ x-ray diffraction, visual and spectroscopic reaction investigations under supercritical and subcritial conditions  

Energy Technology Data Exchange (ETDEWEB)

A microreactor has been developed for in situ, spectroscopic investigations of materials and reaction processes with full external pressure and temperature control from ambient conditions to 400 C and 310 bar. The sample chamber is in direct contact with an external manifold, whereby gases, liquids or fluids can be injected and their activities controlled prior to and under investigation conditions. The microreactor employs high strength, single crystal moissanite windows which allow direct probe beam interaction with a sample to investigate in situ reaction processes and other materials properties. The relatively large volume of the cell, along with full optical accessibility and external temperature and pressure control, make this reaction cell well suited for experimental investigations involving any combination of gas, fluid, and solid interactions. The microreactor's capabilities are demonstrated through an in situ x-ray diffraction study of the conversion of a meta-serpentine sample to magnesite under high pressure and temperature. Serpentine is one of the mineral candidates for the implementation of mineral carbonation, an intriguing carbon sequestration candidate technology.

Diefenbacher, J.; McKelvy, M.; Chizemeshya, A.V.; Wolf, G.H. (ASU)

2010-07-13