WorldWideScience
 
 
1

Barometric pressure and gas composition  

Science.gov (United States)

Many factors affecting artificial gas atmosphere, which is used to maintain life during space flight, are considered. The wide variability of barometric pressure in spacecraft, due in large measure to spacecraft design is discussed. Explosive decompression is described; this develops from instantaneous depressurization of the cabin. Decompression sickness is reviewed, including bubble growth and evolution of gas bubbles in organisms. Dysbarism, hypoxia, and hypercapnia are also discussed.

Malkin, V. B.

1975-01-01

2

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

3

Time series analysis of barometric pressure data  

Energy Technology Data Exchange (ETDEWEB)

Time series of atmospheric pressure data, collected over a period of several years, were analysed to provide undergraduate students with educational examples of application of simple statistical methods of analysis. In addition to basic methods for the analysis of periodicities, a comparison of two forecast models, one based on autoregression algorithms, and the other making use of an artificial neural network, was made. Results show that the application of artificial neural networks may give slightly better results compared to traditional methods.

La Rocca, Paola; Riggi, Francesco [Department of Physics and Astronomy, University of Catania, and INFN, Catania, Via S Sofia 64, I95123 Catania (Italy); Riggi, Daniele, E-mail: francesco.riggi@ct.infn.i [Department of Statistics, University of Milano Bicocca, Ed. U7, Via Bicocca degli Arcimboldi 8, 20126 Milano (Italy)

2010-05-15

4

Time series analysis of barometric pressure data  

International Nuclear Information System (INIS)

Time series of atmospheric pressure data, collected over a period of several years, were analysed to provide undergraduate students with educational examples of application of simple statistical methods of analysis. In addition to basic methods for the analysis of periodicities, a comparison of two forecast models, one based on autoregression algorithms, and the other making use of an artificial neural network, was made. Results show that the application of artificial neural networks may give slightly better results compared to traditional methods.

5

Flip-chip packaging of piezoresistive barometric pressure sensors  

Science.gov (United States)

To miniaturize piezoresistive barometric pressure sensors we have developed a package using flip-chip bonding. However, in a standard flip-chip package the different coefficients of thermal expansion (CTE) of chip and substrate and strong mechanical coupling by the solder bumps would lead to stress in the sensor chip which is not acceptable for piezoresistive pressure sensors. To overcome this problem we have developed a new ultra low stress flip-chip packaging technology. In this new packaging technology for pressure sensors first an under bump metallization (UBM) is patterned on the sensor wafer. As the next step solder bumps are deposited. After wafer-dicing the chips are flip-chip bonded on copper springs within a ceramic cavity. As sources of residual stress we identified the copper springs, the UBM and the solder bumps on the sensor chip. Different CTEs of the silicon chip and the UBM/solder lead to creep strain in the aluminum metallization between UBM and chip. As a consequence a temperature hysteresis can be measured.

Waber, T.; Pahl, W.; Schmidt, M.; Feiertag, G.; Stufler, S.; Dudek, R.; Leidl, A.

2013-05-01

6

Insights into aquifer vulnerability and potential recharge zones from the borehole response to barometric pressure changes  

Science.gov (United States)

Borehole water levels fluctuate in response to deformation of the surrounding aquifer caused by surface loading due to barometric pressure or strain caused by Earth and ocean tides. The magnitude and nature of this response mainly depend on the hydraulic properties of the aquifer and overlying units and borehole design. Thus water level responses reflect the effectiveness of a confining unit as a protective layer against aquifer contamination (and therefore groundwater vulnerability) and to potential aquifer recharge/discharge zones. In this study, time series of borehole water levels and barometric pressure are being investigated using time series analysis and signal processing techniques with the aim of developing a methodology for assessing recharge/discharge distribution and groundwater vulnerability in the confined/semi-confined part of the Chalk aquifer in East Yorkshire, UK. The chalk aquifer in East Yorkshire is an important source for industrial and domestic water supply. The aquifer water quality is threatened by surface pollution particularly by nitrates from agricultural fertilizers. The confined/semi-confined part of this aquifer is covered by various types of superficial deposits resulting in a wide range of the aquifer's degree of confinement. A number of boreholes have been selected for monitoring to cover all these various types of confining units. Automatic pressure transducers are installed to record water levels and barometric pressure measurements at each borehole on 15 minutes recording intervals. In strictly confined aquifers, borehole water level response to barometric pressure is an un-drained instantaneous response and is a constant fraction of the barometric pressure changes. This static confined constant is called the barometric efficiency which can be estimated simply by the slope of a regression plot of water levels versus barometric pressure. However, in the semi confined aquifer case this response is lagged due to water movement between the aquifer and the confining layer. In this case the static constant barometric efficiency is not applicable and the response is represented by a barometric response function which reflects the timing and frequency of the barometric pressure loading. In this study, the barometric response function is estimated using de-convolution techniques both in the time domain (least squares regression de-convolution) and in the frequency domain (discrete Fourier transform de-convolution). In order to estimate the barometric response function, borehole water level fluctuations due to factors other than barometric pressure should be removed (de-trended) as otherwise they will mask the response relation of interest. It is shown from the collected borehole data records that the main four factors other than barometric pressure contribute to borehole water level fluctuations. These are the rainfall recharge, Earth tides, sea tides and pumping activities close to the borehole location. Due to the highly variable nature of the UK weather, rainfall recharge shows a wide variation throughout the winter and summer seasons. This gives a complicated recharge signal over a wide range of frequencies which must be de-trended from the borehole water level data in order to estimate the barometric response function. Methods for removing this recharge signal are developed and discussed. Earth tides are calculated theoretically at each borehole location taking into account oceanic loading effects. Ocean tide effects on water levels fluctuations are clear for the boreholes located close to the coast. A Matlab code has been designed to calculate and de-trend the periodic fluctuations in borehole water levels due to Earth and ocean tides using the least squares regression technique based on a sum of sine and cosine fitting model functions. The program results have been confirmed using spectral analysis techniques.

El Araby, Mahmoud; Odling, Noelle; Clark, Roger; West, Jared

2010-05-01

7

Suitability of commercial barometric pressure sensors to distinguish sitting and standing activities for wearable monitoring.  

Science.gov (United States)

Despite its medical relevance, accurate recognition of sedentary (sitting and lying) and dynamic activities (e.g. standing and walking) remains challenging using a single wearable device. Currently, trunk-worn wearable systems can differentiate sitting from standing with moderate success, as activity classifiers often rely on inertial signals at the transition period (e.g. from sitting to standing) which contains limited information. Discriminating sitting from standing thus requires additional sources of information such as elevation change. The aim of this study is to demonstrate the suitability of barometric pressure, providing an absolute estimate of elevation, for evaluating sitting and standing periods during daily activities. Three sensors were evaluated in both calm laboratory conditions and a pilot study involving seven healthy subjects performing 322 sitting and standing transitions, both indoor and outdoor, in real-world conditions. The MS5611-BA01 barometric pressure sensor (Measurement Specialties, USA) demonstrated superior performance to counterparts. It discriminates actual sitting and standing transitions from stationary postures with 99.5% accuracy and is also capable to completely dissociate Sit-to-Stand from Stand-to-Sit transitions. PMID:24485500

Massé, F; Bourke, A K; Chardonnens, J; Paraschiv-Ionescu, A; Aminian, K

2014-06-01

8

The Effects of Temperature, Humidity and Barometric Pressure on Short Sprint Race Times  

CERN Document Server

A numerical model of 100 m and 200 m world class sprinting performances is modified using standard hydrodynamic principles to include effects of air temperature, pressure, and humidity levels on aerodynamic drag. The magnitude of the effects are found to be dependent on wind speed. This implies that differing atmospheric conditions can yield slightly different corrections for the same wind gauge reading. In the absence of wind, temperature is found to induce the largest variation in times (0.01 s per $10\\dc$ increment in the 100 m), while relative humidity contributes the least (under 0.01 s for all realistic conditions for 100 m). Barometric pressure variations at a particular venue can also introduce fluctuations in performance times on the order of a 0.01 s for this race. The combination of all three variables is essentially additive, and is more important for head-wind conditions that for tail-winds. As expected, calculated corrections in the 200 m are magnified due to the longer duration of the race. The...

Mureika, J R

2006-01-01

9

Total dissolved gas, barometric pressure, and water temperature data, lower Columbia River, Oregon and Washington, 1996  

Science.gov (United States)

Increased levels of total dissolved gas pressure can cause gas-bubble trauma in fish downstream from dams on the Columbia River. In cooperation with the U.S. Army Corps of Engineers, the U.S. Geological Survey collected data on total dissolved gas pressure, barometric pressure, water temperature, and dissolved oxygen pressure at 11 stations on the lower Columbia River from the John Day forebay (river mile 215.6) to Wauna Mill (river mile 41.9) from March to September 1996. Methods of data collection, review, and processing are described in this report. Summaries of daily minimum, maximum, and mean hourly values are presented for total dissolved gas pressure, barometric pressure, and water temperature. Hourly values for these parameters are presented graphically. Dissolved oxygen data are not presented in this report because the quality-control data show that the data have poor precision and high bias. Suggested changes to monitoring procedures for future studies include (1) improved calibration procedures for total dissolved gas and dissolved oxygen to better define accuracy at elevated levels of supersaturation and (2) equipping dissolved oxygen sensors with stirrers because river velocities at the shoreline monitoring stations probably cannot maintain an adequate flow of water across the membrane surface of the dissolved oxygen sensor.

Tanner, Dwight Q.; Harrison, Howard E.; McKenzie, Stuart W.

1996-01-01

10

Torricelli and the ocean of air: the first measurement of barometric pressure.  

Science.gov (United States)

The recognition of barometric pressure was a critical step in the development of environmental physiology. In 1644, Evangelista Torricelli described the first mercury barometer in a remarkable letter that contained the phrase, "We live submerged at the bottom of an ocean of the element air, which by unquestioned experiments is known to have weight." This extraordinary insight seems to have come right out of the blue. Less than 10 years before, the great Galileo had given an erroneous explanation for the related problem of pumping water from a deep well. Previously, Gasparo Berti had filled a very long lead vertical tube with water and showed that a vacuum formed at the top. However, Torricelli was the first to make a mercury barometer and understand that the mercury was supported by the pressure of the air. Aristotle stated that the air has weight, although this was controversial for some time. Galileo described a method of measuring the weight of the air in detail, but for reasons that are not clear his result was in error by a factor of about two. Torricelli surmised that the pressure of the air might be less on mountains, but the first demonstration of this was by Blaise Pascal. The first air pump was built by Otto von Guericke, and this influenced Robert Boyle to carry out his classical experiments of the physiological effects of reduced barometric pressure. These were turning points in the early history of high-altitude physiology. PMID:23455767

West, John B

2013-03-01

11

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

12

Relationships of barometric pressure and environmental temperature with incidence of parturition in beef cows.  

Science.gov (United States)

The relationship between barometric pressure (BARO) and maximum (MAX_T) and minimum (MIN_T) environmental temperatures with the incidence of parturition in beef cows was examined through exploratory data analysis. Spring- and fall-calving records from a 5-yr period (2005 through 2009) collected at the University of Arkansas, Livestock and Forestry Research Station (Batesville) and the Department of Animal Science Savoy Research Unit (Savoy, AR) were used. All cows were multiparous, predominantly Angus, and naturally bred. During this period, 2,210 calves were born over a cumulative 1,547 d. Local weather station BARO and MAX_T and MIN_T data were obtained from the Southern Regional Climate Center, Louisiana State University, Baton Rouge. The combined calving record and climate variables were used to determine differences in BARO, MAX_T, and MIN_T on d 0 (d of calving) and -1, -2, or -3 d, respectively, before calving occurred (CALFD) or did not occur (NOCALFD). Location and season also were included in the model. For fall-calving cows, BARO on d 0 and -1, -2, or -3 was not different between CALFD and NOCALFD (P > 0.10). For spring-calving cows, BARO on d 0, -1, -2, and -3 was greater (P 0.10). In the spring, a decreased MAX_T was associated with CALFD. Maximum environmental temperatures on d 0 (14.7 vs. 16.0°C), -1 (14.4 vs. 16.0°C), and -3 (14.0 vs. 15.7°C) were less for CALFD compared with NOCALFD (P 0.10). For fall, MIN_T was greater on d -1 (12.8 vs. 11.3°C), -2 (13.0 vs. 11.4°C), and -3 (13.1 vs. 11.7°C) for CALFD compared with NOCALFD (P < 0.05). In spring, MIN_T for d 0 (2.6 vs. 3.9°C), -1 (2.5 vs. 3.7°C), -2 (2.1 vs. 3.7°C), and -3 (1.8 vs. 3.8°C) were lesser (P < 0.05) for CALFD vs. NOCALFD. These data indicate that for spring-calving cows, a greater BARO and decreased MAX_T and MIN_T were associated with CALFD, whereas for fall-calving cows, an increase in MAX_T and MIN_T was associated with CALFD. Therefore, monitoring weather conditions may assist producers in preparing for the obstetric assistance of beef cattle. PMID:22147487

Troxel, T R; Gadberry, M S

2012-05-01

13

On the efficiency of barometric arrays to improve the reduction of atmospheric effects on gravity data  

Science.gov (United States)

Air pressure reduction in local gravity measurements is usually done by means of an empirical transfer function (barometric admittance) between pressure and gravity both measured at the same site. In the local zone (critical area for which it may be useful to have more detailed pressure data. One way to model the local atmosphere is to use an array of sensors located around the gravity station. We model the barometric local effect on gravity data using superconducting gravity (SG) data, collected in Strasbourg and barometric records in five sites around the SG station at distances ranging between 10 and 60 km. Six months of gravity and air pressure records are analysed both in the time and frequency domains. The admittance factors for each station are computed by means of different numerical analyses and their time and frequency behaviour investigated. The results demonstrate that in normal weather conditions a single barometer can be enough to account for the pressure effect originating in the local zone and the pressure data from an array are redundant. The use of the barometric array pressure data is found to improve the reduction of the air pressure effects in only one time span among those selected. The improvement is significant at low frequency, while an artificial increase in the residual gravity derives from the array reduction in the high-frequency band (>3.0 cycles/day). The atmospheric reduction from the barometric array is also compared to global loading computations from ECMWF-4Dvar surface pressure data, having a sampling rate of 3 h and a spatial resolution of 0.5°. We also tested a hybrid method based on a spline interpolation of joint ECMWF-4Dvar surface pressure data and local observations collected on the barometric array. The findings are discussed in light of the main features (dimension, geometry and instrumental accuracy) of the barometric array.

Riccardi, U.; Hinderer, J.; Boy, J.-P.

2007-05-01

14

Barometric pressure influence on water table fluctuations in coastal aquifers of partially enclosed seas: An example from the Adriatic coast, Italy  

Science.gov (United States)

SummaryThe water table level fluctuations in a coastal phreatic aquifer of the Adriatic coast (southern Po Plain - Italy) were recorded to characterize groundwater level response to sea level fluctuations. Tide-induced fluctuations, atmospheric pressure loading and recharge from rainfall have all been recognized in the measured water table changes. We also identified additional water table fluctuations that are not related to rain, atmospheric pressure or tides. We propose that these additional fluctuations are related to interaction of groundwater, seiche events and 'inverted barometric effects'. Their amplitude is important, because at a distance of 70 m from the coast they have a magnitude of 0.07 m, whereas the local tide has a 1 m amplitude. Seiches are standing waves that create sea water fluxes which affect groundwater below the first row of dunes in the study area. We propose that this 'inverted barometric effect' is an important process in creating water fluxes in the coastal zone that may strongly affect the position and width of the mixing zone between salt and fresh water.

Balugani, Enrico; Antonellini, Marco

2011-03-01

15

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)

16

Mapping of multi-floor buildings: A barometric approach  

DEFF Research Database (Denmark)

This paper presents a new method for mapping multi5floor buildings. The method combines laser range sensor for metric mapping and barometric pressure sensor for detecting floor transitions and map segmentation. We exploit the fact that the barometric pressure is a function of the elevation, and it varies between different floors. The method is tested with a real robot in a typical indoor environment, and the results show that physically consistent multi5floor representations are achievable.

Özkil, Ali Gürcan; Fan, Zhun

2011-01-01

17

Variations in cosmic radiation intensity associated with the barometric effect  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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; Rogelio Caballero López

2000-01-01

18

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

19

Breath-to-breath variations of alveolar Po2 and Pco2 at barometric pressures of 490, 745 and 1500 Toor in resting awake dogs.  

Science.gov (United States)

Two awake, resting dogs born and raised at low altitude were studied, breathing air (1) at 745 torr, (2) during a 12 days sojourn at 490 torr in an altitude chamber, and (3) during 5 days sojourn at 1500 torr in a hyperbaric chamber. The respired gas was continuously sampled an end-tidal PCO2 and PO2 of sequences of thirty breaths were measured by fast analyzers. The mean value of alveolar PCO2 was 29 torr at high altitude; 35 torr at 745 torr; and 40 torr in hyperbary. The changes of PCO2 indicate different alveolar ventilations which result mainly from the changes of the chemoreceptor drive which is enhanced at high altitude and decreased in hyperbary. The scattering of PCO2 is about the same at the three pressures. The scattering of PO2 is less at high altitude than at sea level, and less at sea level than in hyperbary. On a PCO2 vs PO2 diagram end-tidal PCO2 and PO2 points form elliptical clouds whose mean slopes decrease with the increase of total pressure. The characteristics of the dispersion of the alveolar pressures and of the slopes of the alveolar clouds depend on several factors among which the relevant steepness (i.e. capacitance) of the O2 and CO2 blood abosrption curves at the three pressures presumably plays the major role. PMID:1013514

Imbert, G; Hildwein, G; Dejours, P

1976-11-01

20

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

International Nuclear Information System (INIS)

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 ratchetedclose 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

 
 
 
 
21

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

22

[A device for measuring the burning rate of light and thin homogeneous solid under low barometric pressure and in enriched oxygen].  

Science.gov (United States)

Oxygen enrichment of room air is an effective way to resist hypoxia at high altitude, but it may introduce a potential fire hazard. In common, the burning rate of light and thin homogeneous solid in oxygen enriched atmosphere was used to assess the fire hazard. For the purpose of measuring the burning rate of light and thin homogeneous solid in oxygen enriched atmosphere, we used the methods of laser contact ignition and direct calculation of burning rate, and invented a device that includes mixing gas system, ignition equipment, system of measuring the burning rate and self-made specimen frame. By using the homemade device, we studied the burning rate of filter paper under low pressure and in oxygen-enriched atmosphere and in that of the oxygen concentration of reached stationary burning rate. The results showed that this device was simple, and could obtain the burning rate of light and thin homogeneous solid quantitatively. PMID:23198421

Cheng, Haiyang; Sun, Xuechuan; Zhu, Yinhua; Deng, Weiming; Lin, Zhuo; Liu, Tao

2012-10-01

23

Passive remediation of chlorinated volatile organic compounds using barometric pumping  

International Nuclear Information System (INIS)

The purpose of the Savannah River Integrated Demonstration Program, sponsored by the Department of Energy, is to demonstrate new subsurface characterization, monitoring, and remediation technologies. The interbedded clay and sand layers at the Integrated Demonstration Site (IDS) are contaminated with chlorinated volatile organic compounds (CVOCs). Characterization studies show that the bulk of the contamination is located in the approximately 40 m thick vadose zone. The most successful strategy for removing contaminants of this type from this environment is vapor extraction alone or in combination with other methods such as air sparging or enhanced bioremediation. Preliminary work at the IDS has indicated that natural pressure differences between surface and subsurface air caused by surface barometric fluctuations can produce enough gas flow to make barometric pumping a viable method for subsurface remediation. Air flow and pressure were measured in wells that are across three stratigraphic intervals in the vadose zone' The subsurface pressures were correlated to surface pressure fluctuations but were damped and lagging in phase corresponding to depth and stratum permeability. Piezometer wells screened at lower elevations exhibited a greater phase lag and damping than wells screened at higher elevations where the pressure wave from barometric fluctuations passes through a smaller number of low permeable layers. The phase lag between surface and subsurface pressures results in significant fluxes through these wells. The resultant air flows through the subsurface impacts CVOC fate and transport. With the appropriate controls (e.g. solenoid valves) a naturally driven vapor extraction system can be implemented requiring negligible operating costs yet capable of a large CVOC removal rate (as much as 1--2 kg/day in each well at the IDS)

24

Field measurements of tracer gas transport by barometric pumping  

Energy Technology Data Exchange (ETDEWEB)

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 {approximately}1 millimeter vertical fractures spaced 2 to 4 meters apart. 6 refs., 18 figs., 3 tabs.

Lagus, P.L. [Lagus Applied Technology, San Diego, CA (United States); McKinnis, W.B. [Lawrence Livermore National Lab., Mercury, NV (United States); Hearst, J.R.; Burkhard, N.R.; Smith, C.F. [Lawrence Livermore National Lab., CA (United States)

1994-07-28

25

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

26

Steam-water pressure drop under high pressure condition  

International Nuclear Information System (INIS)

For the Steam Generator (SG) in a commercialized sodium cooled Faster Breeder Reactor, flow instability in water side is one of the most important items need researching. As the first step of the research, thermal hydraulics experiments using water as test fluid were performed under high pressure condition at JAEA with using a circular tube. Pressure drop, heat transfer coefficients and void fraction data were derived. This paper focuses on the discussion to steam-water pressure drop. We evaluated existing correlations for two-phase flow multiplier under high pressure. As a result, Chismholm correlation was confirmed being the best one for the present high pressure data. (author)

27

An Educational Study of the Barometric Effect of Cosmic Rays with a Geiger Counter  

Science.gov (United States)

An educational study of the barometric effect of cosmic rays was carried out using an inexpensive experimental set-up that allowed for long-term monitoring of atmospheric pressure and cosmic ray flux as measured in a Geiger counter. The investigation was intended as a pilot study in view of ongoing involvements of high-school teams operating…

Famoso, Barbara; La Rocca, Paola; Riggi, Francesco

2005-01-01

28

40 CFR 53.56 - Test for effect of variations in ambient pressure.  

Science.gov (United States)

...variations in ambient (barometric) pressure. Tests shall be conducted in a pressure-controlled...areas may be substituted, provided the test pressure requirements are met. Means for simulating...proposed method for simulating the test pressure conditions may be described and...

2010-07-01

29

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

30

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.

31

Contribution to the barometric-effect at the Siemens-Argonaut-Reactor  

International Nuclear Information System (INIS)

The core regions of research reactors frequently contain air-filled cavities, which are in connection with the outer atmosphere. In such reactors changes of the atmospheric pressure lead to a variation of the reactivity (barometric-effect). When measuring the absolute reactivity in these reactors over a longer period it is therefore necessary to apply a correction in accordance with the barometric-effect. At the Siemens-Argonaut-Reactor the reactivity behaviour as a function of the pressure fluctuation in the Argon-filled central channel of the inner reflector has been investigated. With a first-order perturbation analysis in the multigroup diffusion theory it was possible to verify to full satisfaction the experimental results. (orig.)

32

Gas flow to a barometric pumping well in a multilayer unsaturated zone  

Science.gov (United States)

When an open well is installed in an unsaturated zone, gas can flow between the subsurface and the well depending on the gas pressure gradient near the well. This well is called a barometric pumping well (BPW). Quantifying gas flow rate to and from a BPW is indispensable to optimize the passive soil vapor extraction in remediation of volatile organic compounds in the unsaturated zone. This study presents a two-dimensional (2-D) semianalytical solution for a multilayer unsaturated zone (ML solution) to determine gas flow rate to and from a BPW. The gas flow rate is approximated by a decomposing method frequently used in previous studies, that is, first solving the one-dimensional (1-D) vertical flow equation in response to the surface barometric pressure fluctuations and then superimposing this solution on that of the 1-D horizontally radial flow equation. The error induced by this approximation is quantified by a 2-D numerical simulation for the first time in this study. Results show that the maximum error induced is 20% at the peak flow rates. The ML solution is demonstrated to be sufficient for predicting subsurface gas pressure and gas flow rate in a multilayer unsaturated zone by the barometric pumping test at the Hanford site.

You, Kehua; Zhan, Hongbin; Li, Jian

2011-05-01

33

Harmonic response of soil radon-222 flux and concentration induced by barometric oscillations  

Science.gov (United States)

Radon-222 flux and concentration in the soil are sensitive to changes in atmospheric pressure, and in particular to periodic signals, such as the semi-diurnal barometric tide S2. The response of radon flux and concentration to barometric oscillations is calculated analytically for all harmonic degrees in the case of a horizontal layer over a half-space, representing the situation of a soil layer over homogeneous bedrock, taking into account air and water phases and the presence of static vertical advection. The calculations show that the presence of an interface changes dramatically the response to barometric oscillations. Large amplitudes at the forcing frequency (fundamental) are concentrated in the vicinity of the interface, while amplitudes remain negligible at the same depth in a homogeneous half-space. A significant negative phase shift in the surface radon flux is introduced when a shallow interface is present, while radon flux is almost in phase opposition with atmospheric pressure over a homogeneous half-space. While, in most situations, the amplitudes are small and difficult to detect, situations can be exhibited where the amplitudes of harmonics 2 and 3 of radon concentration are larger than 100 Bq m-3, leading, for example, to possible detection of 4-hr peaks in the radon power spectra due to barometric tide S2. Optimal position of the radon sensors appears to be a few centimetres in the bedrock below the soil. Amplitudes of radon concentration and surface flux are sensitive to underlying bedrock permeability, porosity, water saturation and effective radium concentration, and depend also on the presence of advection. At large carrier gas velocities, a more precise calculation valid for multilayered media, is presented, which can be used in volcanic and hydrothermal areas. While the amplitudes of all harmonics for radon concentration in the soil become negligible, the fundamental in radon surface flux reaches a constant and, possibly, observable value dominated by the parameters of the deepest medium. A better knowledge of the response of radon flux and concentration to barometric oscillations is important to interpret the presence or absence of peaks in the power spectra of radon time-series collected for environmental and geodynamical purposes. This study provides further support to the relevance of long-term radon monitoring to constrain the transport properties of the subsurface.

Perrier, Frédéric; Girault, Frédéric

2013-11-01

34

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

35

A sensor fusion method for tracking vertical velocity and height based on inertial and barometric altimeter measurements.  

Science.gov (United States)

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. PMID:25061835

Sabatini, Angelo Maria; Genovese, Vincenzo

2014-01-01

36

Sealing of rotary drums for operation under pressurized conditions  

International Nuclear Information System (INIS)

In practice, rotary drums are always designed for operation under vacuum conditions. In this paper, a novel technique is proposed for sealing the rotary drums under pressurized conditions. The proposed system is based on applying a secondary pressurized volume around the leaking gap of the drum. By controlling the pressure of this volume above the pressure of the drum, it will be possible to prevent from any leakage of gases to the ambient. The objective of a controller in this system is that the pressure of secondary volume be kept above the pressure of the drum in spite of the disturbances which may be exerted on the system by the wind outside the drum. The control system is also required to trace the variations in the drum pressure with the least fluctuations in the pressure difference among the drum and the volume

37

Practical conditions in the neutron diffraction under high pressure  

International Nuclear Information System (INIS)

Practical analysis is made on some conditions in utilizing neutrons for the study of atomistic structure of materials under high pressure. Investigation is made on the geometrical conditions; size of the specimen, width of slits, and the rate of extra-scattering. Experiments are performed on the effects of absorption by high pressure cell and the disturbance due to an overlapping of diffraction peaks. An observation is presented on the pressure-induced transformation in RbBr. (author)

38

Electrochemical noise measurements under pressurized water reactor conditions  

International Nuclear Information System (INIS)

Electrochemical potential noise measurements on sensitized stainless steel pressure tubes under pressurized water reactor (PWR) conditions were performed for the first time. Very short potential spikes, believed to be associated to crack initiation events, were detected when stressing the sample above the yield strength and increased in magnitude until the sample broke. Sudden increases of plastic deformation, as induced by an increased tube pressure, resulted in slower, high-amplitude potential transients, often accompanied by a reduction in noise level

39

A Stochastic Approach to Noise Modeling for Barometric Altimeters  

Directory of Open Access Journals (Sweden)

Full Text Available The question whether barometric altimeters can be applied to accurately track human motions is still debated, since their measurement performance are rather poor due to either coarse resolution or drifting behavior problems. As a step toward accurate short-time tracking of changes in height (up to few minutes, we develop a stochastic model that attempts to capture some statistical properties of the barometric altimeter noise. The barometric altimeter noise is decomposed in three components with different physical origin and properties: a deterministic time-varying mean, mainly correlated with global environment changes, and a first-order Gauss-Markov (GM random process, mainly accounting for short-term, local environment changes, the effects of which are prominent, respectively, for long-time and short-time motion tracking; an uncorrelated random process, mainly due to wideband electronic noise, including quantization noise. Autoregressive-moving average (ARMA system identification techniques are used to capture the correlation structure of the piecewise stationary GM component, and to estimate its standard deviation, together with the standard deviation of the uncorrelated component. M-point moving average filters used alone or in combination with whitening filters learnt from ARMA model parameters are further tested in few dynamic motion experiments and discussed for their capability of short-time tracking small-amplitude, low-frequency motions.

Angelo Maria Sabatini

2013-11-01

40

Comparative analysis of pressure vessel integrity for various LOCA conditions  

International Nuclear Information System (INIS)

In this study, integrity analysis is performed for a classical four loop PWR pressure vessel fabricated from SA533B type ferritic steel. Pressure vessel behavior is analyzed by deterministic and probabilistic methods under transient conditions, which may cause pressurized thermal shock (PTS). In deterministic analysis, the change of material properties and the mechanical state of the vessel are analyzed against changes in coolant pressure and temperature. Probabilistic analysis is performed to obtain pressure vessel beltline region weld failure probabilities in transient conditions. Overall vessel failure probabilities are evaluated based on the results of deterministic analyses. Computer code VISA-II is utilized for the calculation of vessel failure probabilities. Among three cases considered in this study, a medium break loss of coolant accident induced by a 50 cm2 break in the hot leg yields the highest vessel rupture probability. The maximum nil ductility temperature in all cases is still below the NRC PTS limit

 
 
 
 
41

Pyrolysis and gasification behavior of black liquor under pressurized conditions  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study has been to enhance the understanding of the processes involved in pressurized black liquor gasification. Gasification is known to occur in three stages: drying, pyrolysis and char gasification. The work presented here focuses on the pyrolysis and gasification stages. Experiments were carried out primarily in two laboratory-scale reactors. A pressurized grid heater was used to study black liquor pyrolysis under pressurized conditions. Char yields and the fate of elements in the liquor, as well as the degree of liquor swelling, were measured in this device. A pressurized thermogravimetric reactor was used to measure the rate of the char gasification process under different temperatures and pressures and in various gas atmospheres. Pyrolysis experiments were also carried out in this device, and data on swelling behavior, char yields and component release were obtained 317 refs.

Whitty, K.

1997-11-01

42

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 of the measured thermal profiles in the ABAQUS finite element analysis, resulted in very good agreement between the predicted and measured displacements. (author)

43

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 proce...

Diemuodeke, E. O.; Oko, C. O. C.

2010-01-01

44

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

45

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.

46

Steam water heat transfer characteristics under high pressure condition  

International Nuclear Information System (INIS)

For a steam generator with straight double-walled heat transfer tubes that used in sodium cooled faster breeder reactor, clarification of flow instability in heat transfer tubes is one of the most important research themes. As the first step of the research, thermal hydraulics experiments with water were performed under high pressure condition in JAEA with using a circular tube. Pressure drop, heat transfer coefficients and void fraction data were derived. This paper summarizes the heat transfer characteristics under 15 - 18MPa. Saturated boiling heat transfer was discussed with four most famous general heat transfer correlations (Chen, Shah, Steiner-Taborek and Gungor-Winterton) being tested. Under present high pressure condition, it was found that the shah correlation gave good agreement with data at low mass flow rate and Chen correlation gave good agreement at high mass flow rate condition. For the nominate flow rate of w=110 g/s, both Chen and shah correlation can be used. As a result, under present high pressure condition, we recommend the smaller one of the Chen and Shah correlations being used for the calculation of heat transfer coefficient. (author)

47

Conditional Sampling of Bypass Transition in Pressure Gradient Boundary Layers  

Science.gov (United States)

Conditional sampling of velocity fields from Direct Numerical Simulations (DNS) of bypass transition is performed with discrimination between laminar and turbulent events. Individual positive and negative streaks are isolated and an extreme value analysis of their amplitudes is performed. A more detailed view of the growth of positive and negative streaks is obtained than is typical by simply measuring the root mean square perturbations. The resulting velocity distributions are compared with the amplitudes of streaks which undergo secondary instability, and breakdown into turbulent spots. A range of pressure gradients is considered and the rates of turbulent spot production and propagation are investigated. While the spot production rate increases significantly with adverse pressure gradient, it is found that the spot propagation rate is unaffected. By considering the spot spreading angle others have shown a pressure gradient dependence of the propagation parameter. The current work eschews the spreading angle, opting instead to directly track the growth of the spot volume.

Nolan, Kevin; Zaki, Tamer

2011-11-01

48

Modeling of Spray Combustion under Cryogenic and High Pressure Conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paper concerns both the numerical and experimental investigation of turbulent liquid oxygen/hydrogen spray combustion for elevated subcritical pressure and cryogenic inlet temperature conditions. In particular, the combustion in the single injector combustion chamber is studied where experimental data are obtained for gas phase temperature and both droplet size and velocities. The model uses an Eulerian--Lagrangian formulation for the gas and the liquid phase, respectively. Detailed ...

Schlotz, D.; Vogelgesang, M.; Gutheil, E.; Clauss, W.; Sender, J.

2005-01-01

49

Materials Science under Extreme Conditions of Pressure and Strain Rate  

Energy Technology Data Exchange (ETDEWEB)

Solid state dynamics experiments at very high pressures (P >> 10 GPa) and strain rates ({var_epsilon} >> 10{sup 5} s{sup -1}) have been demonstrated on high energy laser facilities, albeit over brief intervals of time and small spatial scales. We have developed two methods for driving samples to high pressures (10-100 GPa) at high strain rate (10{sup 6}-10{sup 8} s{sup -1}) in the solid state. One method uses a shockless compression technique, and the other uses multiple staged shocks. These drives are calibrated with VISAR measurements of the resulting compression wave. Deformation mechanisms are inferred under these conditions by characterizing recovered samples. Material strength at high pressures and strain rates is deduced by measuring the reduced growth of material perturbations at a hydrodynamically unstable interface. Microscopic lattice response is determined by time-resolved Bragg diffraction and x-ray absorption spectroscopy (EXAFS). Large-scale simulations, both at the continuum level using constitutive models and at the lattice level using molecular dynamics simulation, are used to interpret these integral experiments. We will review our progress in this new area of laser-based materials science research, then present a vision for carrying these solid-state experiments to much higher pressures, P > 1000 GPa, on the National Ignition Facility (NIF) laser facility.

Remington, B A; Bazan, G; Bringa, E; Caturla, M; Edwards, M J; Glendinning, S G; Kad, B; Kalantar, D H; Kumar, M; Lasinski, B F; Lorenz, K T; McNaney, J; Meyerhofer, D; Meyers, M A; Pollaine, S M; Reisman, D B; Rowley, D; Schneider, M; Stolken, J; Wark, J; Yaakobi, B

2003-03-27

50

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

51

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

52

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.

53

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

54

STOCHASTIC ACCELERATION OF SUPRATHERMAL PARTICLES UNDER PRESSURE BALANCE CONDITIONS  

International Nuclear Information System (INIS)

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?p –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 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 pI . 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?p –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.

55

Critical heat flux at low pressure and low velocity conditions  

International Nuclear Information System (INIS)

Critical heat flux(CHF) at low pressure and low velocity conditions is important in relation to the design of passive safety reactors, research reactors and district heating reactors as well as accident analyses of commercial nuclear reactors. However, experimental data and design correlations are scarce and physical mechanisms are not well known. KAIST is studying this subject through experiments, theoretical modeling and correlation development. This paper describes the results of the first-phase work. It includes a brief literature survey, introduction of KAIST experimental loop, discussion on the experimental results with a 6mm-ID and 0.685m-long vertical round tube, postulation of physical mechanisms, and suggestion of design correlations

56

Critical heat flux at low velocity and pressure conditions  

International Nuclear Information System (INIS)

The purpose of this study is to provide some systematic understanding on critical heat flux (CHF) at low velocity and pressure conditions in which the effects of gravity and flow instability are remarkable. Experimental data obtained previously for water in an annulus, rectangular ducts and a round tube are briefly reviewed and augmented in collaboration with existing data and correlations to extract more generic information. The effect of channel geometry is then discussed. The effect of channel geometry turned out to be significant at intermediate mass velocities. The difference in CHF at these mass velocities between a round tube and the other channel geometries was attributed mainly to the existence of unheated wall which causes a nonuniform distribution of liquid film. (author)

57

Electrotransport purification of thorium under low pressure conditions  

Science.gov (United States)

It was demonstrated that the ultrapurification of refractory metals by electrotransport refining could best be accomplished in the noncontaminating environment of an orbiting low density materials laboratory such as the Molecular Shield Device. Refining experiments were performed at 2 x 10 to the -12th Torr which resulted in the preparation of small quantities of the World's purest thorium metal. The microgravity occurring in orbit was simulated electromagnetically and shown to be advantageous in eliminating grain-sliding caused by the plastic deformation of the sample at high temperature. The electrotransport sample assembly was tested in several environments including simulated solar irradiation, coldness and darkness and under various pressure conditions. Ultrapure single crystals of alpha thorium were also prepared and characterized. Laboratory electronics for the experiment were developed and a totally automatic control system was used to heat the specimens.

Schmidt, F. A.; Lunde, B. K.; Outlaw, R. A.

1979-01-01

58

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.'

59

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

60

Treatment of a Vadose Zone Plume Using Barometric Pumping: A Passive Soil Vapor Extraction Study at the Miscellaneous Chemicals Basin, Savannah River Site, S.C.  

Science.gov (United States)

A passive soil vapor extraction (PSVE) treatability study at the Miscellaneous Chemical Basin (MCB) of the Savannah River Site (SRS) has been progressing since September 1996. During this time more than 243 pounds of chlorinated organic contaminants (183 lbs of TCE and 61 lbs of PCE) have been removed by natural barometric pumping of wells fitted with BaroBall TM valves (low-pressure check valves). In addition, contour maps of the vadose zone contaminant gas plume made before the study and after 4.5 years of operation show a significant decrease in the extent of the gas plume and identify the source location. To date, over 86% of all PCE and 89% of all TCE have been removed from the system. By projecting the exponentially declining concentration curves it is estimated that 99% of all PCE and TCE will be removed from the system by 2007 and 2009 respectively. In addition, soil samples were collected in July 2001 at various depths within the previously defined plume source area. Analysis of VOC content in these samples confirms that barometric pumping has significantly remediated the contamination in the MCB area. Barometric pumping harnesses natural atmospheric fluctuations to move air in and out of the vadose zone. Barometric pressure fluctuations are transmitted through the vadose zone, however, these pressure waves are damped and delayed in phase to degrees dependent on the effective vertical permeability of the formation. As a result, there is a pressure differential between the atmospheric pressure at the surface and the soil gas pressure in the subsurface. By connecting these two zones with a vadose zone well, the differential pressure will cause gas flow either into or out of the well. If the soil gas in the subsurface contains VOC's (gas phase), than flow out of the well will remove contaminants from the subsurface without mechanical pumping. The Baroball uses a lightweight ball in a conical seat to allow gas flow in only one direction with little pressure, but prevents gas flow in the opposite direction. Thus the Baroball can be used to allow contaminated soil gas out of the well, while preventing clean surface air from flowing into the well and diluting soil gas in the subsurface.

Bosze, S. L.; Riha, B.; Rossabi, J.; Hyde, K.

2001-12-01

 
 
 
 
61

Weather forecasting by insects: modified sexual behaviour in response to atmospheric pressure changes.  

Science.gov (United States)

Prevailing abiotic conditions may positively or negatively impact insects at both the individual and population levels. For example while moderate rainfall and wind velocity may provide conditions that favour development, as well as movement within and between habitats, high winds and heavy rains can significantly decrease life expectancy. There is some evidence that insects adjust their behaviours associated with flight, mating and foraging in response to changes in barometric pressure. We studied changes in different mating behaviours of three taxonomically unrelated insects, the curcurbit beetle, Diabrotica speciosa (Coleoptera), the true armyworm moth, Pseudaletia unipuncta (Lepidoptera) and the potato aphid, Macrosiphum euphorbiae (Hemiptera), when subjected to natural or experimentally manipulated changes in atmospheric pressure. In response to decreasing barometric pressure, male beetles exhibited decreased locomotory activity in a Y-tube olfactometer with female pheromone extracts. However, when placed in close proximity to females, they exhibited reduced courtship sequences and the precopulatory period. Under the same situations, females of the true armyworm and the potato aphid exhibited significantly reduced calling behaviour. Neither the movement of male beetles nor the calling of armyworm females differed between stable and increasing atmospheric pressure conditions. However, in the case of the armyworm there was a significant decrease in the incidence of mating under rising atmospheric conditions, suggesting an effect on male behaviour. When atmospheric pressure rose, very few M. euphorbiae oviparae called. This was similar to the situation observed under decreasing conditions, and consequently very little mating was observed in this species except under stable conditions. All species exhibited behavioural modifications, but there were interspecific differences related to size-related flight ability and the diel periodicity of mating activity. We postulate that the observed behavioral modifications, especially under decreasing barometric pressure would reduce the probability of injury or death under adverse weather conditions. PMID:24098362

Pellegrino, Ana Cristina; Peñaflor, Maria Fernanda Gomes Villalba; Nardi, Cristiane; Bezner-Kerr, Wayne; Guglielmo, Christopher G; Bento, José Maurício Simões; McNeil, Jeremy N

2013-01-01

62

A dual-pressure boundary condition for use in simulations of bifurcating conduits.  

Science.gov (United States)

A dual-pressure boundary condition has been developed for computational modelling of bifurcating conduits. The condition involves the imposition of a constant pressure on one branch while adjusting iteratively the pressure on the other branch until the desired flow division is obtained. The dual-pressure condition eliminates the need for specifying fully-developed flow conditions, which thereby enables significant reduction of the outlet branch lengths. The dual-pressure condition is suitable for both steady and time-periodic simulations of laminar or turbulent flows. PMID:12405605

Gin, Ron; Straatman, Anthony G; Steinman, David A

2002-10-01

63

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

64

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

International Nuclear Information System (INIS)

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

65

Pressurizer and steam-generator behavior under PWR transient conditions  

International Nuclear Information System (INIS)

Experiments have been 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 main purpose of the LOFT facility is to provide data for the development of computer codes for PWR transient analyses. Significant thermal-hydraulic differences have been 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. Two transients were accompanied by pressurizer inflow and a reduction of the heat transfer in the steam generator to a very small value. The other two transients were accompanied by pressurizer outflow while the steam generator behavior was controlled

66

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

67

Generalization of barometric formula for a sollisional plasma in a magnetostatic and rf fields  

International Nuclear Information System (INIS)

A modification is derived of the barometric formula, describing the plasma density modulation due to nonlinear ponderomotive forces of rf fields implied by collisional diffusion. A one-dimensional model of a fully-ionized plasma is used for simplification. The viscosity and inertia of electrons and the influence of rf fields on ions are neglected. The generalized barometric formula is found as a solution of the Bernoulli-type equation for plasma density derived from the general theory of hydrodynamics. The influence of rf fields on particle fluxes and plasma density is discussed. (J.U.)

68

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

Directory of Open Access Journals (Sweden)

Full Text Available 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

2009-01-01

69

SMART behavior under over-pressurizing accident conditions  

International Nuclear Information System (INIS)

SMART (system-integrated modular advanced reactor) is an integral reactor of 330 MW capacity with passive safety features under development in Korea. The design is developed by combining the firmly-established commercial reactor technologies with new and advanced technologies such as industry proven KOFA (Korea optimized fuel assembly) based nuclear fuels, self-pressurizing pressurizer, helically coiled once-through steam generators, and new control concepts. The design of SMART focuses on enhancing the safety and reliability of the reactor by employing inherent safety features such as low core power density, elimination of large break loss of coolant accident, etc. In addition, in order to prevent the progression of emergency situations into accidents, the SMART is provided with a number of engineered safety features such as passive residual heat removal system, passive emergency core cooling system, safeguard vessel, and passive containment over-pressure protection system. This paper presents an overview of the SMART design, characteristics of it's safety systems, and results of over-pressure accident analyses. The results of the accident analyses show that the SMART provides the inherent over-pressure protection capability for design basis accidents without actuation of any protection devices such as safety valves, rupture disks, etc. (orig.)

70

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

71

?-? transition pathway of iron under quasihydrostatic pressure conditions  

Science.gov (United States)

We have carefully investigated the ?-? transition pathway of iron under quasihydrostatic pressures. For this purpose, combined measurements of extended x-ray absorption fine structure (EXAFS) and x-ray magnetic circular dichroism at the Fe K edge were performed using a helium pressure-transmitting medium. Collapse of the ferromagnetism simultaneously occurs with the ?-? structural transition, which is in contrast to the scenario that the transition is driven by the pressure-induced instability of the ferromagnetism in ? phase of iron. We conclude that shear stress is important to initiate the ?-? transition. Our model to fit the EXAFS profile demonstrates that the local atomic arrangement in ? phase is slightly distorted due to unfinished shuffle motion, whereas shear motion finishes at the beginning of the transition.

Ishimatsu, N.; Sata, Y.; Maruyama, H.; Watanuki, T.; Kawamura, N.; Mizumaki, M.; Irifune, T.; Sumiya, H.

2014-07-01

72

Materials science under extreme conditions of pressure and strain rate  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Solid-state dynamics experiments at very high pressures and strain rates are becoming possible with high-power laser facilities, albeit over brief intervals of time and spatially small scales. To achieve extreme pressures in the solid state requires that the sample be kept cool, with T-sample < T-melt. To this end, a shockless, plasma-piston "drive" has been developed on the Omega laser, and a staged shock drive was demonstrated on the Nova laser. To characterize the drive, velocity interfero...

Remington, Ba; Bazan, G.; Belak, J.; Bringa, E.; Caturla, M.; Colvin, Jd; Edwards, Mj; Glendinning, Sg; Ivanov, Ds; Kad, B.; Kalantar, Dh; Kumar, M.; Lasinski, Bf; Lorenz, Kt; Mcnaney, Jm

2004-01-01

73

Behaviour of polymer muds under high pressure – high temperature conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

74

Spherical steel containments of pressurized water reactors under accident conditions  

International Nuclear Information System (INIS)

The investigations will deal with the mechanical behavior of a free standing spherical containment shell built for the latest type of a German pressurized water reactor. The diameter of the containment shell is 56 m. The wall thickness is 38 mm. The material used is the ferritic steel 15MnNi63. The investigation program includes theoretical as well as experimental activities and concerns four different accidents which are beyond the scope of the common design and licensing practice: containment behavior under quasi-static pressure increase up to containment failure; containment behavior under high transient pressures; containment vibrations due to earthquake loadings (consideration of shell imperfections); containment buckling due to earthquake loadings. First results concerning the containment behavior under quasi-static pressure increase are presented. It turns out that the mechanical failure of the containment shell is controlled by plastic instability. A computer program to describe this problem has been developed and membrane tests to check the computational methods have been carried out. (orig.)

75

A Correlation Study of Cardiopulmonary Arrests, Cholesterol and Pressures  

Directory of Open Access Journals (Sweden)

Full Text Available This study consisted of cardiopulmonary arrests occurring between January 1990 and December 1991 in a Midwestern City in Kansas, U.S.A., with a population of 300,000. Admission cholesterol levels and hourly barometric pressures were obtained to show if there exists a relationship between cardiopulmonary arrests, cholesterol levels and barometric pressures. Statistical analysis was performed using Pearson-Moment Correlation Coefficient. Scattergrams amongst the dependent variables such as time, age, cholesterol, temperature and each of these dependent variables vs the independent variable, barometric pressure are depicted. Small value of the correlation coefficient in each case indicates no significant linear correlation between sudden changes in barometric pressure, cholesterol level and cardiopulmonary arrests.

S.E. Rider

2003-01-01

76

Solid Nitrogen at Extreme Conditions of High Pressure and Temperature  

Energy Technology Data Exchange (ETDEWEB)

We review the phase diagram of nitrogen in a wide pressure and temperature range. Recent optical and x-ray diffraction studies at pressures up to 300 GPa and temperatures in excess of 1000 K have provided a wealth of information on the transformation of molecular nitrogen to a nonmolecular (polymeric) semiconducting and two new molecular phases. These newly found phases have very large stability (metastability) range. Moreover, two new molecular phases have considerably different orientational order from the previously known phases. In the iota phase (unlike most of other known molecular phases), N{sub 2} molecules are orientationally equivalent. The nitrogen molecules in the theta phase might be associated into larger aggregates, which is in line with theoretical predictions on polyatomic nitrogen.

Goncharov, A; Gregoryanz, E

2004-04-05

77

Relight imaging at low temperature, Low pressure conditions  

DEFF Research Database (Denmark)

High-altitude relight inside a lean, direct-injection, gas turbine combustor is investigated experimentally by high-speed imaging. Ignition testing is conducted at two operating conditions: a 'safe' point at which relight is possible, and an 'unsafe' condition where ignition is precluded by the large air mass flow rate. Image processing software has been developed to analyze the motion and breakup of the imaged flame. At the safe condition, the developing flame kernels are typically swept downstream and towards the fuel-injector center-line, before moving upstream. The comparatively large gas-phase velocity at the unsafe condition causes rapid disintegration of the ignition kernel. At neither condition does the size of the spark kernel determine ignition outcome. Good agreement is demonstrated between the measured spark-centroid velocity and CFD predictions of gas-phase velocity below the igniter tip.

Read, Robert; Rogerson, J.W.

2008-01-01

78

Estimation of partial pressure during graphite conditioning by matrix method  

Science.gov (United States)

Plasma Facing Components (PFC) of SST-1 tokamak are designed to be compatible for UHV as it is kept in the main vacuum vessel. Graphite is the most widely used plasma facing material in present day tokamaks. High thermal shock resistance and low atomic number carbon are the most important properties of graphite for this application. However, graphite is porous and absorbs gases, which may be released during plasma operation. Graphite tiles are baked at high temperature of about 1000 °C in high vacuum (10-5 Torr) for several hours before installing them in the tokamak to remove the impurities (mainly water vapour and metal impurities), which may have been deposited during machining of the tiles? The measurements of the released gas (such as H2, H2O, CO, CO2, Hydrocarbons, etc.) from graphite tiles during baking are accomplished with the help of a Quadrupole Mass Analyzer (QMA). Since, the output of this measurement is a mass spectrum and not the partial pressures of the residual gases, one needs to adopt some procedure to convert the spectrum to obtain the partial pressures. The conventional method of analysis is tedious and time consuming. We propose a new approach based on constructing a set of linear equations and solving them using matrix operations. This is a simple method compared to the conventional one and also eliminates the limitations of the conventional method. A Fortran program has been developed which identifies the likely gases present in the vacuum system and calculates their partial pressures from the data of the residual gas analyzers. Application of this method of calculating partial pressures from mass spectra data will be discussed in detail in this paper.

Chaudhuri, P.; Prakash, A.; Reddy, D. C.

2008-05-01

79

Estimation of partial pressure during graphite conditioning by matrix method  

International Nuclear Information System (INIS)

Plasma Facing Components (PFC) of SST-1 tokamak are designed to be compatible for UHV as it is kept in the main vacuum vessel. Graphite is the most widely used plasma facing material in present day tokamaks. High thermal shock resistance and low atomic number carbon are the most important properties of graphite for this application. However, graphite is porous and absorbs gases, which may be released during plasma operation. Graphite tiles are baked at high temperature of about 1000 deg. C in high vacuum (10-5 Torr) for several hours before installing them in the tokamak to remove the impurities (mainly water vapour and metal impurities), which may have been deposited during machining of the tiles. The measurements of the released gas (such as H2, H2O, CO, CO2, Hydrocarbons, etc.) from graphite tiles during baking are accomplished with the help of a Quadrupole Mass Analyzer (QMA). Since, the output of this measurement is a mass spectrum and not the partial pressures of the residual gases, one needs to adopt some procedure to convert the spectrum to obtain the partial pressures. The conventional method of analysis is tedious and time consuming. We propose a new approach based on constructing a set of linear equations and solving them using matrix operations. This is a simple method compared to the conventional one and also eliminates the limitations of the conventional method. A Fortran program has been developed which identian program has been developed which identifies the likely gases present in the vacuum system and calculates their partial pressures from the data of the residual gas analyzers. Application of this method of calculating partial pressures from mass spectra data will be discussed in detail in this paper

80

A Correlation Study of Cardiopulmonary Arrests, Cholesterol and Pressures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study consisted of cardiopulmonary arrests occurring between January 1990 and December 1991 in a Midwestern City in Kansas, U.S.A., with a population of 300,000. Admission cholesterol levels and hourly barometric pressures were obtained to show if there exists a relationship between cardiopulmonary arrests, cholesterol levels and barometric pressures. Statistical analysis was performed using Pearson-Moment Correlation Coefficient. Scattergrams amongst the dependent variables such as time...

Rider, S. E.; Taher, S. M.

2003-01-01

 
 
 
 
81

X-ray reflectivity measurements of liquid/solid interfaces under high hydrostatic pressure conditions.  

Science.gov (United States)

A high-pressure cell for in situ X-ray reflectivity measurements of liquid/solid interfaces at hydrostatic pressures up to 500?MPa (5?kbar), a pressure regime that is particularly important for the study of protein unfolding, is presented. The original set-up of this hydrostatic high-pressure cell is discussed and its unique properties are demonstrated by the investigation of pressure-induced adsorption of the protein lysozyme onto hydrophobic silicon wafers. The presented results emphasize the enormous potential of X-ray reflectivity studies under high hydrostatic pressure conditions for the in situ investigation of adsorption phenomena in biological systems. PMID:24365919

Wirkert, Florian J; Paulus, Michael; Nase, Julia; Möller, Johannes; Kujawski, Simon; Sternemann, Christian; Tolan, Metin

2014-01-01

82

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

83

Probes for bulk superconductivity in iron pnictide systems under hydrostatic pressure conditions  

International Nuclear Information System (INIS)

We discuss the sensitivity of iron based superconductors to the hydrostaticity of pressure conditions, which results in discrepancies between different studies. To clarify the situation we present the phase diagram of several systems obtained on single crystals, using the highly hydrostatic pressure conditions of argon in a diamond anvil cell, and an ac susceptibility method to detect superconductivity.

84

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 the future to explore methods for estimating hepatic interstitial pressure noninvasively. (paper)

85

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

Science.gov (United States)

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 the future to explore methods for estimating hepatic interstitial pressure noninvasively.

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

2012-01-01

86

Dynamical stability of iron under high-temperature and high-pressure conditions  

Science.gov (United States)

The dynamical stability of iron under high-temperature and high-pressure conditions was investigated based on the phonons evaluated by using a recently developed method. It is revealed that both the fcc-Fe and the hcp-Fe are dynamically stable in a wide temperature and pressure range. The bcc-Fe phase can be stable as well, while in a limited temperature/pressure regime bounded by a dynamical stability limit and a harmonic limit. Direct evidence shows that it is the entropy term that plays a critical role in stabilizing the bcc-Fe under high-temperature and high-pressure conditions.

Kong, L. T.; Li, J. F.; Shi, Q. W.; Huang, H. J.; Zhao, K.

2012-03-01

87

Effect of atmospheric conditions on soil diffuse degassing  

Science.gov (United States)

Secondary manifestations of volcanism in the Azores archipelago include low temperature fumaroles (maximum temperature around 100 °C), hot springs, CO2 cold springs and several diffuse degassing areas. Continuous monitoring of hydrothermal soil CO2 flux started at Furnas volcano (S. Miguel island) in October 2002 with the installation of a permanent gas station coupled also with several meteorological sensors (barometric pressure, air temperature, wind speed and direction, air relative humidity, rainfall, soil temperature and soil water content). In October 2004, a second station was installed in this volcanic system. Both stations perform measurements by the accumulation chamber method. Daily and seasonal cycles have been observed in the soil CO2 flux time series. From all the monitored variables, air temperature and barometric pressure are the ones that best correlate with the soil CO2 flux cycles. Air temperature and soil CO2 flux behave in an inverse way: the higher soil CO2 flux values are registered early in the morning (lower air temperature) while lower soil CO2 flux values in the afternoon (higher air temperature). Barometric pressure shows higher correlation with the CO2 cycles during winter months and in bad weather conditions. In order to understand the influence of soil conditions on the gas release, several simulations with TOUGH2 geothermal simulator were performed. We used different TOUGH modules to describe multi-component (water, CO2 and air) and multi-phase (liquid and gas) fluids. Using a 1D model, a parametric study was performed to understand the physical mechanisms producing the observed variations. In this simplified model, only the air temperature was changed. Numerical results, in agreement with the observed data, show that the CO2 are strongly dependent on domain permeability, gas saturation and temperature changes at the surface. Amplitude of the thermal oscillations influences the amplitude of the observed variations in soil degassing but does not affect their temporal evolution. A main role is played by rock permeability.

Pio Rinaldi, Antonio; Viveiros, Fatima; Vandemeulebrouck, Jean; Todesco, Micol

2010-05-01

88

Monte-Carlo calculations of the partial and total barometric coefficients of the cosmic ray muon component  

International Nuclear Information System (INIS)

The results of calculations of the partial barometric coefficients for rigid muons in cosmic rays are presented. The atmospheric one-dimensional nuclear-meson cascade has been calculated by the method of statistical trials. (orig./WBU)

89

Antiferromagnetic critical pressure in URu2Si2 under hydrostatic conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

90

Mechanical pressure gages under difficult conditions; Mechanische Druckmessgeraete unter schwierigen Einsatzbedingungen  

Energy Technology Data Exchange (ETDEWEB)

In spite of electronic solutions, mechanical pressure meters still find their place in reliable in-situ process pressure monitoring without external influences. Planners and users often have difficulties selecting the optimum meter for a given application, especially where difficult operating conditions are concerned. The contribution presents a neutral and practical guide. (orig.)

Nieswandt, T. [Wika Alexander Wiegand GmbH und Co. KG, Klingenberg (Germany)

2008-05-15

91

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.

92

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

93

Blind source separation for groundwater pressure analysis based on nonnegative matrix factorization  

Science.gov (United States)

identification of the physical sources causing spatial and temporal fluctuations of aquifer water levels is a challenging, yet a very important hydrogeological task. The fluctuations can be caused by variations in natural and anthropogenic sources such as pumping, recharge, barometric pressures, etc. The source identification can be crucial for conceptualization of the hydrogeological conditions and characterization of aquifer properties. We propose a new computational framework for model-free inverse analysis of pressure transients based on Nonnegative Matrix Factorization (NMF) method for Blind Source Separation (BSS) coupled with k-means clustering algorithm, which we call NMFk. NMFk is capable of identifying a set of unique sources from a set of experimentally measured mixed signals, without any information about the sources, their transients, and the physical mechanisms and properties controlling the signal propagation through the subsurface flow medium. Our analysis only requires information about pressure transients at a number of observation points, m, where m?r, and r is the number of unknown unique sources causing the observed fluctuations. We apply this new analysis on a data set from the Los Alamos National Laboratory site. We demonstrate that the sources identified by NMFk have real physical origins: barometric pressure and water-supply pumping effects. We also estimate the barometric pressure efficiency of the monitoring wells. The possible applications of the NMFk algorithm are not limited to hydrogeology problems; NMFk can be applied to any problem where temporal system behavior is observed at multiple locations and an unknown number of physical sources are causing these fluctuations.

Alexandrov, Boian S.; Vesselinov, Velimir V.

2014-09-01

94

Whole body barometric plethysmography: a screening method to investigate airway reactivity and acute lung injuries in freely moving pigs.  

Science.gov (United States)

The aim of this work was to investigate whether the Penh index, measured using whole body barometric plethysmography, can be used as a screening parameter to evaluate the airway reactivity and the intensity of the pulmonary response to endotoxins. Penh was firstly recorded in non-sedated freely moving piglets exposed (1) to a nebulized acetylcholine (Ach) pre-treated or not with clenbuterol, or (2) to endotoxin challenge. To measure Penh simultaneously with total pulmonary resistance (R(L)), dynamic compliance (C(dyn)) and intrapleural pressure changes (Max Delta Ppl), an oesophageal balloon catheter technique was used and the piglets were anaesthetised. The recordings were performed during (1) an intravenous metacholine (Mch) challenge and (2) in endotoxin-exposed animals. In freely moving animals, Ach induced a significant dose-dependent increase in Penh, which was significantly blocked by clenbuterol. Endotoxin instillation also resulted in a significant rise in Penh while the corresponding response measured under anaesthesia was significantly and positively correlated with R(L) and Max Delta Ppl. Similar results were obtained during Mch challenge but the Penh was negatively correlated with C(dyn). We conclude that Penh could be used in freely moving piglets as a screening index for airway reactivity and pulmonary functional changes in cholinergic and endotoxin challenges. PMID:15501145

Halloy, David J; Kirschvink, Nathalie A; Vincke, Grégoire L; Hamoir, Julien N; Delvaux, François H; Gustin, Pascal G

2004-11-01

95

Deformation behaviour of Zr-2.5 wt percent Nb pressure tubes under internal pressurization and ramp temperature conditions  

International Nuclear Information System (INIS)

The deformation behaviour of 0.6 m long Zr-2.5 wt percent Nb pressure tube specimens deformed under internal pressurization and ramp temperature conditions has been studied. Both inert gas and steam have been used as the pressurizing medium. Controlled heating rates in the range 1-25 K/s and internal pressures in the range 0-12 MPa have been investigated. It was observed that, except at the very high test pressures, the samples deformed to circumferential strains well in excess of the nominal 'contact' strain of 0.18 before possible rupture. Over the time scale of the biaxial tests carried out, the effect of steam on deformation behaviour appeared to be minimal. It was also found that the major features of the biaxial deformation behaviour can be investigated, at least qualitatively, by carrying out uniaxial tensile tests. However, detailed analysis of uniaxial and biaxial data showed that there were several major differences between the two types of data. These differences are discussed in considerable detail in the present report

96

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

97

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

98

Accessing High Pressure States Relevant to Core Conditions in the Giant Planets  

Energy Technology Data Exchange (ETDEWEB)

We have designed an experimental technique to use on the National Ignition Facility (NIF) laser to achieve very high pressure (P{sub max} > 10 Mbar = 1000 GPa), dense states of matter at moderate temperatures (kT < 0.5 eV = 6000 K), relevant to the core conditions of the giant planets. A discussion of the conditions in the interiors of the giant planets is given, and an experimental design that can approach those conditions is described.

Remington, B A; Cavallo, R M; Edwards, M J; Ho, D D; Lorenz, K T; Lorenzana, H E; Lasinski, B F; McNaney, J M; Pollaine, S M; Smith, R F

2004-04-15

99

Effects of atmospheric conditions on surface diffuse degassing  

Science.gov (United States)

Diffuse degassing through the soil is commonly observed in volcanic areas and monitoring of carbon dioxide flux at the surface can provide a safe and effective way to infer the state of activity of the volcanic system. Continuous measurement stations are often installed on active volcanoes such as Furnas (Azores archipelago), which features low temperature fumaroles, hot and cold CO2 rich springs, and several diffuse degassing areas. As in other volcanoes, fluxes measured at Furnas are often correlated with environmental variables, such as air temperature or barometric pressure, with daily and seasonal cycles that become more evident when gas emission is low. In this work, we study how changes in air temperature and barometric pressure may affect the gas emission through the soil. The TOUGH2 geothermal simulator was used to simulate the gas propagation through the soil as a function of fluctuating atmospheric conditions. Then, a dual parameters study was performed to assess how the rock permeability and the gas source properties affect the resulting fluxes. Numerical results are in good agreement with the observed data at Furnas, and show that atmospheric variables may cause the observed daily cycles in CO2 fluxes. The observed changes depend on soil permeability and on the pressure driving the upward flux.

Rinaldi, A. P.; Vandemeulebrouck, J.; Todesco, M.; Viveiros, F.

2012-11-01

100

INFLUENCE OF CHANGE OF INITIAL PRESSURE ON GAS-CONTROL PLANT ON GAS CONSUMPTION CONDITIONS / ??????? ????????? ?????????? ???????? ?? ???????????????? ?????? ?? ????? ??????????? ????  

Directory of Open Access Journals (Sweden)

Full Text Available The authors provide the analysis of gas consumption conditions of household sector is provided, they show the necessity to match the daily schedule of gas consumption due to the reduction of peak load. Processing of experimental data allowed to reveal the dependence of initial pressure on GCP and gas consumption. The dependence of resistance equivalent on pressure quantity due to change of gas consumption is defined / ???????? ?????? ?????? ??????????????? ???????????-???????? ???????, ???????? ????????????? ???????????? ????????? ??????? ??????? ???? ?? ???? ?????????? ??????? ????????. ????????? ????????????????? ?????? ????????? ??????? ??????????? ?????????? ???????? ?? ??? ? ??????? ????. ?????????? ??????????? ?????????????? ????????????? ?? ???????? ???????? ?? ???? ????????? ??????? ????

Zhila V. A. / ???? ?????? ?????????

2014-10-01

 
 
 
 
101

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

102

Determination of the effective thermal conductivity of granular materials under varying pressure conditions  

Science.gov (United States)

We report on thermal conductivity measurements performed on glass spheres of different grain sizes under varying pressure conditions ranging from 10-5 up to 1000 hPa. Glass spheres of 0.1 up to 4.3 mm were used as an analogue for the coarse-grained fractions of planetary regolith. From the obtained conductivity versus pressure data, sample pore sizes were derived and compared to estimated pore sizes. An increasing difference between derived and estimated pore size with increasing grain size was found. The behavior of the granular matter with decreasing pressure was analyzed by estimating the Knudsen number for the given system. The results indicate a high variability of the effective thermal conductivity for Martian conditions. Furthermore, the results imply that the thermal conductivity reaches a grain size-dependent, but pressure-independent, value for pressures below 0.01 hPa. For vacuum conditions a linear relation between grain size and effective thermal conductivity was found. Additionally, a mixture was analyzed, which showed a stronger decrease with gas pressure compared to the single-sized samples. From the pore size derived for the mixture an ``effective'' grain size composed of weighted mean of the mixture components was determined.

Huetter, E. S.; Koemle, N. I.; Kargl, G.; Kaufmann, E.

2008-12-01

103

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

104

Characterization of Contaminant Transport by Gravity, Capillarity and Barometric Pumping in Heterogeneous Vadose Zones  

Energy Technology Data Exchange (ETDEWEB)

This final report summarizes the work and accomplishments of our three-year project. We 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. Our 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. The key feature of the VZO constructed at Lawrence Livermore National Laboratory (LLNL) is the variety of plume-tracking techniques that can be used at a single location. Electric resistance tomography (ERT) uses vertical arrays of electrodes across the vadose zone that can monitor electrical resistance changes in the soil as a plume moves downward to the water table. These resistance changes can be used to provide ''snapshots'' of the progress of the plume. Additionally, monitoring wells have been completed at multiple levels in the vicinity of a central infiltration site. Sensors emplaced at different levels include electrically conducting gypsum blocks for detecting saturation changes, thermistors for monitoring temperature changes and pressure transducers for observing barometric changes at different levels in the vadose regime. The data from these sensors are providing important information about the state of the gas- and liquid-phase dynamics of the infiltration process. Similarly, access ports at different levels have been used to supply gas-phase samples while lysimeters yield liquid-phase samples. Studies involving gas-phase tracers were carried out at LLNL and at an Orange County Water District site in southern California to evaluate the time-dependent chemical signature of a plume that was spiked with an array of dissolved noble-gas tracers. Our work also correlate chemical signatures with those of the above-mentioned sensors that track the physical changes in the vadose zone. From the VZO at the LLNL site and from 3-D diagnostic simulations of our very first tracer-spiked plume infiltration event, we produced a much better understanding of the implications of soil heterogeneity for unsaturated zone contaminant transport at DOE sites. Even though the LLNL VZO site is considered to be hydrologically ''tight'' owing to the low permeability of the clays and silts that dominate the soil formations there, we find that saturation increases resulting from a near-surface ''leak'' reach the water table across the 20-meter-thick vadose zone in only tens of hours. This rapid transport at the site cannot be accurately simulated by layered models that derive their hydrologic properties from borehole-soil samples. In the LLNL vadose zone, layered infiltration models clearly underpredict of the rate of contaminant infiltration to the water table. Chemical transport simulations based on layered models of the Hanford vadose zone also appear to drastically underpredict contaminant migration. Furthermore, only simulations assuming a heterogeneous regime ''threaded'' by extremely high-permeability pathways can explain the rapid increase in saturation observed with ERT near the water table. Three-dimensional predictive models of a hypothetical tritiated water leak that are based on the above mentioned VZO infiltration-experiment diagnostic models were run. Tritiated water is an excellent conservative tracer and the infiltration simulations predict, in very good agreement with VZO experiments, that a continuous hypothetical tritium release (2-3 liters/rein) would be expected to reach the water table at significant concentrations within days. The numerical model suggests that this arrival time is determined by the amount of time required, infiltrating liquid at a given rate, to flush one pore volume in the soil between the infiltration point and the water table. Another infiltration event monitored by ERT demonstrated that infiltration could occur even more

Carrigan, C R; Martins, S A; Ramirez, A L; Daily, W D; Hudson, G B; Ralsont, D; Ekwurzel, B

2001-02-27

105

Embedded optical probes for simultaneous pressure and temperature measurement of materials in extreme conditions  

Science.gov (United States)

We present recent efforts at Los Alamos National Laboratory (LANL) to develop sensors for simultaneous, in situ pressure and temperature measurements under dynamic conditions by using an all-optical fiber-based approach. While similar tests have been done previously in deflagration-to-detonation tests (DDT), where pressure and temperature were measured to 82 kbar and 400°C simultaneously, here we demonstrate the use of embedded fiber grating sensors to obtain high temporal resolution, in situ pressure measurements in inert materials. We present two experimental demonstrations of pressure measurements: (1) under precise shock loading from a gas-gun driven plate impact and (2) under high explosive driven shock in a water filled vessel. The system capitalizes on existing telecom components and fast transient digitizing recording technology. It operates as a relatively inexpensive embedded probe (single-mode 1550 nm fiber-based Bragg grating) that provides a continuous fast pressure record during shock and/or detonation. By applying well-controlled shock wave pressure profiles to these inert materials, we study the dynamic pressure response of embedded fiber Bragg gratings to extract pressure amplitude of the shock wave and compare our results with particle velocity wave profiles measured simultaneously.

Sandberg, R. L.; Rodriguez, G.; Gibson, L. L.; Dattelbaum, D. M.; Stevens, G. D.; Grover, M.; Lalone, B. M.; Udd, E.

2014-05-01

106

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 viscomet...

Mahmood Amani

2012-01-01

107

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

108

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 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)

109

Study on Condensing Heat Transfer Test under High Temperature and High Pressure Conditions  

Science.gov (United States)

The condensing heat transfer coefficient is one of the important factors to evaluate the pressure change under BWR (Boiling Water Reactors) abnormal transients. Condensing condition is about 7 MPa of pressure with vapor flow. Many condensing studies have been done under atmospheric conditions with stagnant vapor. However, the condensing test results under BWR conditions have not reported. Therefore, the condensing heat transfer test of the saturated vapor with vertical upward vapor flow has been done under high temperature and high pressure conditions. The final purpose of this study is to develop the condensing correlation under BWR conditions. In this report, the data under pressures of 0.5 and 1 MPa are reported. Test section is tube. The inner diameter and condensing length is 57.6 mm and 2000 mm. Test fluid is saturated vapor. The following test results were obtained (1) Flooding may have occurred at a higher vapor velocity. (2) Vertical vapor flow has the effect to enhance the condensing heat transfer. (3) The measured heat transfer coefficients are larger than that of Nusselt model due to the vertical vapor flow

Morooka, Shinichi; Kubo, Shinji; Shirakawa, Ken-Etu; Yuasa, Hiroko; Yamamoto, Tetuzou; Ono, Hiroshi

110

Pressurization of cryogens - A review of current technology and its applicability to low-gravity conditions  

Science.gov (United States)

A review of technology, history, and current status for pressurized expulsion of cryogenic tankage is presented. Use of tank pressurization to expel cryogenic fluid will continue to be studied for future spacecraft applications over a range of operating conditions in the low-gravity environment. The review examines experimental test results and analytical model development for quiescent and agitated conditions in normal-gravity followed by a discussion of pressurization and expulsion in low-gravity. Validated, 1-D, finite difference codes exist for the prediction of pressurant mass requirements within the range of quiescent normal-gravity test data. To date, the effects of liquid sloshing have been characterized by tests in normal-gravity, but analytical models capable of predicting pressurant gas requirements remain unavailable. Efforts to develop multidimensional modeling capabilities in both normal and low-gravity have recently occurred. Low-gravity cryogenic fluid transfer experiments are needed to obtain low-gravity pressurized expulsion data. This data is required to guide analytical model development and to verify code performance.

Van Dresar, N. T.

1992-01-01

111

Pressurization of cryogens: A review of current technology and its applicability to low-gravity conditions  

Science.gov (United States)

A review of technology, history, and current status for pressurized expulsion of cryogenic tankage is presented. Use of tank pressurization to expel cryogenic fluids will continue to be studied for future spacecraft applications over a range of operating conditions in the low-gravity environment. The review examines experimental test results and analytical model development for quiescent and agitated conditions in normal-gravity, followed by a discussion of pressurization and expulsion in low-gravity. Validated, 1-D, finite difference codes exist for the prediction of pressurant mass requirements within the range of quiescent normal-gravity test data. To date, the effects of liquid sloshing have been characterized by tests in normal-gravity, but analytical models capable of predicting pressurant gas requirements remain unavailable. Efforts to develop multidimensional modeling capabilities in both normal and low-gravity have recently occurred. Low-gravity cryogenic fluid transfer experiments are needed to obtain low-gravity pressurized expulsion data. This data is required to guide analytical model development and to verify code performance.

Vandresar, N. T.

1992-01-01

112

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

113

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)

114

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)

115

Effect of mixing rule boundary conditions on high pressure (liquid + liquid) equilibrium prediction  

International Nuclear Information System (INIS)

Highlights: ? Prediction of LLE from the combined use of EOS and liquid model are examined. ? The mixing rule used affects the predicted pressure dependence of LLE. ? MHV1 mixing rule predicts decent LLE at low pressures. ? WS mixing rule predicts more accurate excess volume and LLE at high pressures. ? The hybrid of MHV1 and WS mixing rule gives overall the best predictions. - Abstract: We examine the prediction of high pressure (liquid + liquid) equilibrium (LLE) from the Peng–Robinson equation with three excess Gibbs free energy (Gex)-based mixing rules (MR): the first order modified Huron–Vidal (MHV1), the Wong–Sandler (WS), and a hybrid of these two (referred to as GexB2). These mixing rules differ by the boundary conditions used for determination of the temperature and composition dependence of parameters a and b in the PR EOS. The condition of matching the excess Gibbs free energy from the EOS at zero pressure to that from the Gex model, used in MHV1 and GexB2 MR, leads to a similar miscibility gap from PR EOS and the Gex model used. On the other hand, the condition of matching excess Helmholtz energy from the EOS at infinite pressure to that from the Gex model, used in the WS MR, shows remarkable deviations. The condition of quadratic composition dependence in the second virial coefficient (B2), used in WS and GexB2 MR, allows for both positive and negative values in the molar excess volume. Depending on the mixture, either the increase or decrease of the miscibility gap with pressure can be observed when the WS or the GexB2 MR is used. The condition of linear combination of molecular sizes of each component used in the MHV1 MR, however, often leads to small, positive molar excess volumes. As a consequence, the predicted LLE from using the MHV1 MR are insensitive to pressure. Therefore, we find that the GexB2 mixing rule provides the best predictive power for the LLE over a wide range of temperature and pressure.

116

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

117

Effect of boundary conditions of failure pressure models on reliability estimation of buried pipelines  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the effect of boundary conditions of various failure pressure models published for the estimation of failure pressure. Furthermore, this approach is extended to the failure prediction with the help of a failure probability model. The first order Taylor series expansion of the limit state function is used in order to estimate the probability of failure associated with each corrosion defect in buried pipelines for long exposure periods in years. The effects of random variables such as defect depth, pipe diameter, defect length, fluid pressure, corrosion rate, material yield stress, material ultimate tensile strength and pipe thickness on the failure probability of the buried pipelines are systematically investigated for the corrosion pipeline by using an adapted failure probability model and varying failure pressure model. (orig.)

Lee, O.S.; Pyun, J.S. [School of Mechanical Engineering, InHa Univ., Incheon (Korea); Hwang, S.W.; Cho, K.S. [Mechanical Engineer Design Dept., Dongyang Univ., KyoungSangBukDo (Korea)

2004-07-01

118

Experimental investigations of bundle boiloff and reflood under high-pressure low heat flux conditions  

International Nuclear Information System (INIS)

Results are reported from high-pressure bundle boiloff and reflood tests run during the second series of pressurized-water reactor small-break loss-of-coolant accident (SBLOCA) heat transfer experiments. Tests were conducted at Oak Ridge National Laboratory in the Thermal Hydraulic Test Facility (THTF), a 64-rod, full-length rod bundle heat transfer loop. Tests discussed include five bundle boiloff tests and five reflood tests. Tests were performed under conditions similar to those expected in an SBLOCA. The objective of reflood testing was to study bundle quenching behavior under conditions of varying system pressure, linear power, and flooding rate. Results indicate that average bundle quench rates are roughly 40% of flooding rates for THTF heater rods. The purpose of the boiloff testing was to characterize the response of a full-length heated core undergoing a low-power boiloff transient. Primary test parameters included the linear heat rate and the depressurization rate

119

Investigation of the influences of atmospheric conditions on the variability of radon and radon progeny in buildings  

Science.gov (United States)

Analysis of time-series data sets, collected in vernacular buildings and workplaces linked with radium source bedrock has identified a number of internal and external pressure characteristics linking meteorological parameters with the variability of radon gas and its progeny. The cellars in these buildings are excavated from the bedrock associated with the radium source and have relatively high levels of radon concentration along with largely stable microclimatic conditions, which differ from those of the buildings' ground and upper levels. In workplace environments cyclical characteristics are apparent, associated with heating and ventilation related to working hours. Comparative radon concentration data, collected within buildings and similarities identified between buildings, suggest the need to distinguish between short and longer-term influences. From a range of comparative data studied, water vapour pressure, a partial pressure of barometric pressure, is indicated as a principal determinant of the short-term variability of radon gas concentrations, with barometric pressure determining the trend or general longer term level, both linked to temperature. Wind speed appears to have the potential for a dual influence on radon variability: directly, through wind pressure differences and indirectly, through changes to the water vapour component.

Marley, Frederick

120

Study on vortex cavitation in a compact fast reactor. Effects of system pressure on inception condition  

International Nuclear Information System (INIS)

A compact sodium reactor is designed as a commercialized fast reactor cycle system. A 1/10 scaled water experiment was performed to optimize flow in an upper plenum of the reactor vessel, because of high flow velocity resulted from the compacted vessel. In the experiment, vortex cavitation was found at the hot leg inlet because of high velocity in the hot leg pipe (9.4m/s in the design). To evaluate cavitation inception condition of the commercialized reactor, we use the cavitation number k in order to consider the difference of system pressures (0.1MPa in the experiment and 0.3MPa in the design). The minimum pressure at the vortex center will depend on vortex core radius (size of forced vortex region). It is related to axial velocity gradient and fluid viscosity in theory of the Burger's stretched vortex model. We carried out a basic water experiment to investigate the influence of system pressure and fluid viscosity on the vortex cavitation. The cavitation number at the inception of vortex cavitation slightly increased according to the increase of the system pressure. It means that the vortex cavitation occurs easily under higher pressure condition as compared with the similar condition of cavitation number with lower pressure. However the increase was less than 30% when the system pressure was varied from 0.1 to 0.3MPa. The influence of fluid viscosity was examined by change of fluid temperature. Velocity distribution around the vortex was also measured to see the structure of vortex. (authors)

 
 
 
 
121

Aza-Michael reaction of 12-N-carboxamide of (-)-cytisine under high pressure conditions.  

Science.gov (United States)

The first example of aza-Michael reaction of 12-N-carboxamide of quinolizidine alkaloid (-)-cytisine with ?,?-unsaturated ketones, dimethyl acetylenedicarboxylate and ?-nitrostyrene under high pressure condition has been described. It has been shown that the [4+2]-cycloaddition takes place in the case with N-phenylmaleimide. PMID:25330752

Tsypysheva, Inna P; Lobov, Alexander N; Kovalskaya, Alena V; Petrova, Polina R; Ivanov, Sergey P; Rameev, Shamil A; Borisevich, Sophia S; Safiullin, Rustam L; Yunusov, Marat S

2015-01-01

122

Influence of initial and boundary conditions on the formation of reactor pressure vessel thermal shock  

International Nuclear Information System (INIS)

Influence of initial and boundary conditions on the formation of reactor pressure vessel thermal shock is analyzed by the example of South Ukraine NPP -1 with WWER-1000/V-302. The most conservative scenario for a group of initiating events related to the secondary leaks was obtained in a series of thermal-hydraulic calculations

123

Monitoring breathing in avian embryos and hatchlings by the barometric technique.  

Science.gov (United States)

This communication describes the application of the barometric technique to the measurements of the breathing pattern (tidal volume and breathing rate) and pulmonary ventilation (VE) in chicken embryos and hatchlings. The chamber-plethysmograph was separated into two sections, an animal compartment, maintained at incubation temperature, and a recording compartment kept at a lower temperature. In the case of the embryos, the eggshell itself represented the animal compartment. The hatchlings were accommodated into a "nest" compartment. A flow-through system permitted simultaneous measurements of oxygen consumption (VO2) and carbon dioxide production. Values of breathing rate corresponded to those counted visually in hatchlings while resting in the incubator, and data of resting VE were similar to those obtained by airflow plethysmography, a more invasive technique applicable only to the hatchlings. At rest, the ventilatory equivalent (VE/VO2) of the hatchlings was similar to that reported for adult birds, while in embryos it was much lower. Hypoxia (15 and 10% O2) and hypercapnia (2 and 4% CO2) caused hyperventilation (increase in VE/VO2), both in the hatchlings and in the embryos, these latter using hypometabolism as the main approach to hyperventilate in hypoxia. We conclude that the barometric technique can be adapted to the study of breathing and VE responses in avian embryos and hatchlings. PMID:17825629

Szdzuy, Kirsten; Mortola, Jacopo P

2007-11-15

124

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.

125

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

126

Flare-out condition of Morris-Thorne wormhole and finiteness of pressure  

CERN Document Server

Wormhole is defined as the topological structure with the throat connecting two asymptotically flat spaces. In order to have and maintain the structure of the wormhole, there needs the geometrical flare-out condition, i.e., the minimal size at throat. In the case of Morris-Thorne type wormhole, the condition is given by the huge surface tension compared to the energy density times the square of the light speed. In this paper, we re-considered the flare-out condition for the wormhole with the Einstein equation, checked the finiteness of the pressure, and investigated its physical meaning.

Kim, Sung-Won

2013-01-01

127

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)

128

Automatic optimization of the operating conditions of thermionic converters using cesium vapor pressure  

International Nuclear Information System (INIS)

Techniques for optimizing the efficiency of a thermionic converter (TC) for electric power generation are described. Attention is given to the possibility of varying cesium vapor pressure in the TC to conform to changing operating conditions including the build-up of gaseous fission products in the emitter. An optimization algorithm incorporating the dynamic parameters of the cesium channel is proposed, and an adaptive control system is described. The efficiency of a TC electric generator with adaptive cesium vapor pressure control was studied experimentally and the results agreed well with the optimization calculations. 6 references

129

Capillary pressure and heterogeneity for the CO2/water system in sandstone rocks at reservoir conditions  

Science.gov (United States)

A novel method is presented to measure drainage capillary pressure curves both at the core and sub-core scale using CO2 and water at reservoir conditions. The experimental configuration is very similar to the one used in traditional steady-state relative permeability experiments. Capillary pressure measurements are made at the inlet face of the sample by successively increasing the flow rate of the non-wetting phase while measuring the saturation with a medical X-ray Computed Tomography (CT) scanner. The method requires that the wetting phase pressure is uniform across the core and can be measured in the outlet end-cap. A capillary pressure curve is obtained in less than two days, as compared to weeks for existing methods that use porous plates. Drainage capillary pressure curves of CO2 and water are measured for two sandstones rock cores with different lithology and pore size distribution. Experiments are carried out at 25 and 50 °C and at 9 MPa pore pressure, while keeping the confining pressure on the core at 12 MPa. There is excellent agreement between the new method and data from mercury intrusion porosimetry; beside providing confidence in the new technique, such comparison allows for an estimate of the wetting and interfacial properties of the CO2/water system. X-ray CT scanning allows for precise imaging of fluid saturations at a resolution of about (2.5 × 2.5 × 1) mm3, thus enabling quantification of sub-core scale capillary pressure curves. These measurements provide independent confirmation that sub-core scale capillary heterogeneity plays an important role in controlling saturation distributions during multiphase flow.

Pini, Ronny; Krevor, Samuel C. M.; Benson, Sally M.

2012-03-01

130

Nonlinear analysis for a double-channel natural circulation loop under low-pressure conditions  

International Nuclear Information System (INIS)

On the basis of the homogeneous flow model and Galerkin nodal approximation method, a numerical model for a double-channel natural circulation loop is developed. The calculated steady-state results provide a reasonable agreement against the experimental data in the high power region but over-estimate in the low power region under unequal heating conditions for the double channels. Nonlinear dynamics and stability boundary of the system are also analyzed under equal heating power conditions. Two unstable regions, Type-I and Type-II instabilities, are found in this system. In the low inlet subcooling region, the oscillations of the equal-heating double channels are out-of-phase under low power conditions due to the effect of the gravitational pressure drop; however, are in-phase under high power conditions resulting from the effect of the two-phase frictional pressure drop. On the other hand, in the high inlet subcooling region, these double channels are both nearly in-phase at Type-I and Type-II stability boundaries, where the two-phase frictional drop is dominate for the channel pressure drop. (author)

131

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

132

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

133

Assessment of Fuel Behaviour under Large Break LOCA Condition for Indian Pressurized Heavy Water Reactor  

International Nuclear Information System (INIS)

Pressurized heavy water reactor (PHWR) consists of a large number of coolant channel assemblies. Each channel assembly is loaded with number of short length fuel bundles. A fuel element consists of sintered cylindrical UO2 pellets contained in a thin collapsible Zircaloy-4 cladding. Large break loss of coolant accident (LBLOCA) in PHWR results in insertion of positive reactivity due to core voiding leading to increase in reactor power. For large breaks, there is an early increase in neutron power and the event leads to reactor trip occurring from neutronic signals besides various other process trips. PHT system depressurizes rapidly and heat transfer from fuel rods decreases sharply which results in rapid rise in clad temperature. With this rise in clad temperature, the exothermic zirconium-metal water reaction would also start contributing toward energy generation and hence results in rapid rise in fuel clad temperature. The fuel clad temperature in the core is estimated during large break LOCA accident and fuel failures in this case are calculated. Under the postulated accident conditions, fuel shall remain in position and not suffer distortion to an extent that would render post- accident core cooling ineffective. The criteria for accident conditions for predicting fuel failure are: (1) The maximum oxygen concentration in the least affected half thickness of clad shall not exceed 0.7 per cent by weight. (2) Stress in the cladding shall not exceed burst stress. (3) The total energy in fuel element including radial average enthalpy shall be less than 200 cal.g-1 in the over power transient. In an accident transient fuel clad will be subjected to high temperature and high pressure difference across the clad. The coolant pressure goes down in case of large break LOCA. The fission gas pressure is estimated in transient considering fuel temperature and deformation of clad. The fuel element failure is considered if the fuel clad local stress equal or exceeds the burst stresses. The burst stress is calculated considering, clad temperature, differential pressure between clad and coolant and oxidation of the Zircaloy-4 during the transient. In the over power transient initiated by reactivity initiated accident or LOCA, cumulative energy deposition in the fuel is estimated. In this paper, assessment of fuel damage under LBLOCA condition for Indian PHWRs is performed for identified limiting governing break sizes. Analysis demonstrates that under governing LOCA condition with high pressure ECCS available, adequate coolant pressure at the time of peak clad temperature on collapsible clad prevents the gross fuel failure and fuel clad failure is limited to low value of full core in the entire spectrum of break sizes and locations. (author)

134

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

135

Flow Visualization at Cryogenic Conditions Using a Modified Pressure Sensitive Paint Approach  

Science.gov (United States)

A modification to the Pressure Sensitive Paint (PSP) method was used to visualize streamlines on a Blended Wing Body (BWB) model at full-scale flight Reynolds numbers. In order to achieve these conditions, the tests were carried out in the National Transonic Facility operating under cryogenic conditions in a nitrogen environment. Oxygen is required for conventional PSP measurements, and several tests have been successfully completed in nitrogen environments by injecting small amounts (typically flow. A similar technique was employed here, except that air was purged through pressure tap orifices already existent on the model surface, resulting in changes in the PSP wherever oxygen was present. The results agree quite well with predicted results obtained through computational fluid dynamics analysis (CFD), which show this to be a viable technique for visualizing flows without resorting to more invasive procedures such as oil flow or minitufts.

Watkins, A. Neal; Goad, William K.; Obara, Clifford J.; Sprinkle, Danny R.; Campbell, Richard L.; Carter, Melissa B.; Pendergraft, Odis C., Jr.; Bell, James H.; Ingram, JoAnne L.; Oglesby, Donald M.

2005-01-01

136

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

Science.gov (United States)

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

2014-05-01

137

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

138

Flow Visualization at Cryogenic Conditions Using a Modified Pressure Sensitive Paint Approach  

Science.gov (United States)

A modification to the Pressure Sensitive Paint (PSP) method was used to visualize streamlines on a Blended Wing Body (BWB) model at full-scale flight Reynolds numbers. In order to achieve these conditions, the tests were carried out in the National Transonic Facility operating under cryogenic conditions in a nitrogen environment. Oxygen is required for conventional PSP measurements, and several tests have been successfully completed in nitrogen environments by injecting small amounts (typically < 3000 ppm) of oxygen into the flow. A similar technique was employed here, except that air was purged through pressure tap orifices already existent on the model surface, resulting in changes in the PSP wherever oxygen was present. The results agree quite well with predicted results obtained through computational fluid dynamics analysis (CFD), which show this to be a viable technique for visualizing flows without resorting to more invasive procedures such as oil flow or minitufts.

Watkins, A. Neal; Goad, William K.; Obara, Clifford J.; Sprinkle, Danny R.; Campbell, Richard L.; Carter, Melissa B.; Pendergraft, Odis C., Jr.; Bell, James H.; Ingram, JoAnne L.; Oglesby, Donald M.

2005-01-01

139

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

140

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

 
 
 
 
141

Seismic-safe conditions of blasting near pressure pipe-lines during power installation construction  

International Nuclear Information System (INIS)

Seismic-safe conditions for performing drill-blasting operations in the vicinity of underground gas pipelines when constructing thermal- or nuclear power plants are discussed. It is shown that, for the determination of seismic-safe parameters, of drill-blasting operations, the maximum permissible level of seismic loads should be specified taking into account the mechanical properties of the pipeline.metal, structural parameters of the gas pipeline and the pressure of the medium transported. Besides, the seismic effect of the blast should be considered with regard to particular conditions of blasting and rock properties. The equations and diagrams used in the calculation are given

142

Modeling and Investigation of Electromechanical Valve Train Actuator at simulated Pressure conditions  

DEFF Research Database (Denmark)

In an electromechanical valve actuated engine, the valves are driven by solenoid-type actuators and cam-shaft is eliminated. Control of each valve provides flexibility in valve timings over all engine conditions and achieves the benefits of variable valve timing(VVT). This paper is about investigation of Electro-mechanical actuator at simulated pressure conditions for a single cylinder engine. For this purpose, a scaled down actuator with reduced armature lift and high stiffness springs are being used. Experiments are conducted to measure valve release timings, transition times and contact velocities. Furthermore, discussion about the spring, magnetic, exhausts gas forces and their ability to actuate the system as desired.

Habib, Tufail

2012-01-01

143

Conditions for sustaining low-pressure plasma columns by travelling electromagnetic UHF waves  

Energy Technology Data Exchange (ETDEWEB)

The paper considers the conditions for sustaining low-pressure plasma columns by travelling electromagnetic waves in symmetric and dipolar modes, respectively. The treatment is fully electrodynamic. It is shown that the wave energy flux along the plasma column determines the conditions for sustaining the discharge. In particular as the plasma is sustained by a symmetric wave whose flux depends mainly on the radial distribution of the wave electric field whilst for a dipolar wave sustained plasma the flux is specified by the magnitude of the axial wave field component at the plasma-dielectric interface. (orig.). 12 refs.

Benova, E. [Institute for Foreign Students, Sofia (Bulgaria). Dept. of Phys.; Zhelyazkov, I.

1997-10-01

144

Conditions for sustaining low-pressure plasma columns by travelling electromagnetic UHF waves  

International Nuclear Information System (INIS)

The paper considers the conditions for sustaining low-pressure plasma columns by travelling electromagnetic waves in symmetric and dipolar modes, respectively. The treatment is fully electrodynamic. It is shown that the wave energy flux along the plasma column determines the conditions for sustaining the discharge. In particular as the plasma is sustained by a symmetric wave whose flux depends mainly on the radial distribution of the wave electric field whilst for a dipolar wave sustained plasma the flux is specified by the magnitude of the axial wave field component at the plasma-dielectric interface. (orig.)

145

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

146

BWR In-Core Monitor Housing Replacement Under Dry Condition of Reactor Pressure Vessel  

International Nuclear Information System (INIS)

A new method of In-Core Monitor Housing replacement has been successfully applied to Tokai Unit 2 (BWR with 1100 MWe) in April of 2001. It was designed to replace a housing under dry condition of reactor pressure vessel (RPV): this enabled the elimination of water filled-up and drained processes during the replacement procedure resulting in the reduction of implementation schedule. To realize the dry condition, the radiation shields were placed in the RPV and the hollow guide pipe (GP) was adopted to transfer the apparatuses from the top to the bottom work area. (authors)

147

Flare-out condition of a Morris-Thorne wormhole and finiteness of pressure  

Science.gov (United States)

A wormhole is defined as a topological structure with a throat connecting two asymptotically-flat spaces. In order to have and maintain the structure of the wormhole, a geometrical flare-out condition, i.e., a minimal size at throat, needs to be satisfied. In the case of a Morris-Thorne-type wormhole, the condition is given by surface tension which is huge compared to the energy density times the square of the light speed. In this paper, we re-considered the flare-out condition for a wormhole by using the Einstein equation, checked the finiteness of the pressure, and investigated its physical meaning. We also derived the power-law form of the flare-out condition.

Kim, Sung-Won

2013-11-01

148

Line-tied MHD modes: effect of plasma pressure, axial boundary condition and axial flow  

Science.gov (United States)

Recent 3D nonlinear magnetohydrodynamic (MHD) simulations of astrophysical jets [1] showed a narrow jet-like region with very tightly wound magnetic fields, very suggestive of jet observations. These results were unexpected because such tightly wound magnetic fields should be violently MHD unstable. In order to make direct contact with the simulations of Ref. [1], we present a linear stability study in resistive MHD in cylindrical geometry. In this work, stability is studied including axial flows and finite plasma pressure. We also changed the axial boundary conditions to model those typical of astrophysical jets and laboratory experiments, using line-tying at one end of the field lines and non-line-tied boundary conditions at the other end [2]. The numerical results show that pressure strongly shifts the marginal stability threshold relative to the Kruskal-Shafranov threshold and a monotonically increasing pressure profile stabilizes the plasma. On the other hand, non-line-tied boundary conditions have little effect on marginal stability for typical parameters. All the results are supported by analytical studies based on reduced ideal MHD. [1] H. Li, G. Lapenta, J. M. Finn, S. Li, and S. A. Colgate, Astrophys. J. 643, 92 (2006). [2] D. D. Ryutov, I. Furno, T. P. Intrator, S. Abbate, and T. Madziwa-Nussinov, Phys. Plasmas 13, 032105 (2006).

Arcudi, Francesco; Delzanno, Gian Luca; Finn, John M.

2008-11-01

149

Spherically symmetric models: generalised local conditions separating expansion from collapse in models with anisotropic pressures  

CERN Document Server

We investigate spherically symmetric spacetimes with an anisotropic ?uid and discuss the exis- tence and stability of a dividing shell separating expanding and collapsing regions. We resort to a 3 + 1 splitting and obtain gauge invariant conditions relating intrinsic spacetimes quantities to characteristics of the matter source. We ?nd that the dividing shell is de?ned by a generalization of the Tolman-Oppenheimer-Volko? equilibrium condition. The latter establishes a balance between the pressure gradients, both isotropic and anisotropic, and the strength of the ?elds induced by the Misner-Sharp mass inside the separating shell and by the pressure ?uxes. This de?nes a local equi- librium condition, but conveys also a non-local character given the de?nition of the Misner-Sharp mass. By the same token it is also a generalized thermodynamical equation of state as usually interpreted for the perfect ?uid case, which now has the novel feature of involving both the isotropic pressure P and the anisotropic stress. W...

Mimoso, José P; Mena, Filipe C

2013-01-01

150

Wall pressure and conditional flow structures downstream of a reattaching flow region  

International Nuclear Information System (INIS)

Highlights: ? Investigation of the separating and reattaching flow over a thick plate. ? Analysis of the evolution of the large scale vortices downstream of the reattachment. ? Stochastic estimation of the velocity correlated with the fluctuating wall pressure. ? Use of swirling strength and FTLE to detect and characterize the coherent structures. ? Observation of a rapid loss of coherence of vortices downstream of the reattachment. - Abstract: The separating and reattaching flow over a thick plate with sharp angle at Re = 80,000 is investigated using pressure and HS-PIV measurements. After having studied the mean flow properties, which are found in good agreement with the literature, a particular emphasis is given concerning the eduction and the analysis of the evolution of the large scale vortices downstream of the reattachment. This is done using an adapted multi-time and multichannel stochastic estimation of the velocity correlated with the fluctuating wall pressure. Swirling strength and Finite Time Lyapunov Exponents are then used in order to detect and characterize the structures and their dynamics. Conditional statistics based on the feature longitudinal position are computed in order to educe intensity, size, position and convection velocity of each conditional feature. A rapid longitudinal decrease of the fluctuating kinetic energy carried by these conditional structures has been observed, highlighting their rapid loss of coherence downstream mean ss of coherence downstream mean reattachment.

151

Wall pressure and conditional flow structures downstream of a reattaching flow region  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer Investigation of the separating and reattaching flow over a thick plate. Black-Right-Pointing-Pointer Analysis of the evolution of the large scale vortices downstream of the reattachment. Black-Right-Pointing-Pointer Stochastic estimation of the velocity correlated with the fluctuating wall pressure. Black-Right-Pointing-Pointer Use of swirling strength and FTLE to detect and characterize the coherent structures. Black-Right-Pointing-Pointer Observation of a rapid loss of coherence of vortices downstream of the reattachment. - Abstract: The separating and reattaching flow over a thick plate with sharp angle at Re = 80,000 is investigated using pressure and HS-PIV measurements. After having studied the mean flow properties, which are found in good agreement with the literature, a particular emphasis is given concerning the eduction and the analysis of the evolution of the large scale vortices downstream of the reattachment. This is done using an adapted multi-time and multichannel stochastic estimation of the velocity correlated with the fluctuating wall pressure. Swirling strength and Finite Time Lyapunov Exponents are then used in order to detect and characterize the structures and their dynamics. Conditional statistics based on the feature longitudinal position are computed in order to educe intensity, size, position and convection velocity of each conditional feature. A rapid longitudinal decrease of the fluctuating kinetic energy carried by these conditional structures has been observed, highlighting their rapid loss of coherence downstream mean reattachment.

Sicot, C., E-mail: christophe.sicot@ensma.fr [Institut Pprime, UPR CNRS 3346, ENSMA, Universite de Poitiers, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France); Perrin, R.; Tran, T.T.; Boree, J. [Institut Pprime, UPR CNRS 3346, ENSMA, Universite de Poitiers, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France)

2012-06-15

152

Freezing and melting of 3D complex plasma structures under microgravity conditions driven by neutral gas pressure manipulation  

CERN Document Server

Freezing and melting of large three-dimensional complex plasmas under microgravity conditions is investigated. The neutral gas pressure is used as a control parameter to trigger the phase changes: Complex plasma freezes (melts) by decreasing (increasing) the pressure. Evolution of complex plasma structural properties upon pressure variation is studied. Theoretical estimates allow us to identify main factors responsible for the observed behavior.

Khrapak, S A; Huber, P; Molotkov, V I; Lipaev, A M; Naumkin, V N; Thomas, H M; Ivlev, A V; Morfill, G E; Petrov, O F; Fortov, V E; Malentschenko, Yu; Volkov, S

2011-01-01

153

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

154

Equation of state for solids with high accuracy and satisfying the limitation condition at high pressure  

International Nuclear Information System (INIS)

An equation of state (EOS) with high accuracy is proposed to strictly satisfy the Fermi gas limitation condition at high pressure. The EOS (SJX EOS) is a modification of the effective Rydberg (ER2) EOS. Instead of Holzapfel's method to directly modify the ER2 EOS, one modifying term is added to the ER2 EOS to make it not only satisfy the high pressure limitation condition, but also to avoid the disadvantages occurring in the Holzapfel and 'adapted polynomial expansion of the order 3' (AP3) EOSs. The two-parameter ER2, Holzapfel, and three-parameter SJX, AP3, Kumari and Dass (KD) EOSs are applied to 50 materials to fit all experimental compression data available. The five EOSs also are applied to 37 of the 50 materials to fit experimental compression data at low-pressure ranges. The results show that for all pressure ranges the AP3 EOS gives the best fitting results; the SJX, ER2, Holzapfel and KD EOSs sequentially give inferior results. Otherwise, it is shown that the values of B0, B0' and B0'' are different for different EOSs and also, within one EOS, for high and low-pressure ranges. The SJX EOS gives the best consistency between the values obtained by fitting all experimental data available, and the experimental data at low-pressure ranges, respectively. The AP3 EOS gives the worst results. The differences of the values of B0, B0' and B0'' obtained for the ER2, Holzapfel and KD EOSs with those obtained for the SJX EOS are large at high-pressure ranges, but decrease at low-pressure ranges. At present, the newest experimental compression data, within the widest compression range, are available for solid n-H2. The values of B0, B0' and B0'' fitted by using the SJX EOS are almost in agreement with these experimental data. The ER2 EOS gives inferior values, and other EOSs give fairly bad results. For the predicted compression curves and the cohesive energy, the SJX EOS gives the best results; the AP3 EOS gives the worst results, even for many solids the AP3 EOS cannot give physically correct results for the cohesive energy. The analysis shows that for such solids, the variation of pressure and energy versus compression ratio calculated by using the AP3 EOS would oscillate, physically incorrectly. Although the AP3 EOS has the best fitting ability to the pressures, it has the worst predicting ability, and fails to be a universal EOS. The SJX EOS is recommended and can be taken as a candidate of universal EOSs to predict compression curves of solids in a wide pressure range only using the values of B0, B0' and B0'' obtained from low-pressure data

155

Measurements of mixtures with carbon dioxide under supercritical conditions using commercial high pressure equipment  

Energy Technology Data Exchange (ETDEWEB)

There is a growing interest in studying physical properties of binary and multicomponent fluid mixtures with supercritical carbon dioxide (CO{sub 2}) over an extended range of temperature and pressure. The estimation of properties such as density, viscosity, saturation pressure, compressibility, solubility and surface tension of mixtures is important in design, operation and control as well as optimization of chemical processes especially in extractions, separations, catalytic and enzymatic reactions. The phase behaviour of binary and multicomponent mixtures with supercritical CO{sub 2} is also important in the production and refining of petroleum where mixtures of paraffin, naphthene and aromatics with supercritical fluids are often encountered. Petroleum fluids can present a complex phase behaviour in the presence of CO{sub 2}, where two-phase (VLE and LLE) and three phase regions (VLLE) might occur within ranges of supercritical conditions of temperature and pressure. The objective of this study is to develop an experimental methodology for measuring the phase behaviour of mixtures containing CO{sub 2} in supercritical regions, using commercial high-pressure equipment. (author)

Andrade, Luciana L.P.R. de; Rutledge, Luis Augusto Medeiros; Moreno, Eesteban L.; Hovell, Ian; Rajagopal, Krishnaswamy [Universidade Federal do Rio de Janeiro (LATCA-EQ-UFRJ), RJ (Brazil). Escola de Quimica. Lab. de Termodinamica e Cinetica Aplicada

2012-07-01

156

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)

157

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)

158

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

International Nuclear Information System (INIS)

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)

159

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

International Nuclear Information System (INIS)

Since the suggestion of external reactor vessel cooling (ERVC), the effects of melting and cooling on the response of structural integrity of the reactor pressure vessel (RPV) under core melting accident conditions have been investigated. To investigate the initial behavior of RPV lower head and the effects of analysis conditions on the structural integrity of RPV, the transient analysis is utilized considering the transient state. 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 temperature and stress analyses are performed for core melting accident by using ABAQUS. Finally, the potential for vessel damage is discussed using the Larson-Miller curve and damage rule. In addition, the results by transient analysis are compared with those by steady state analysis and the effects of analysis conditions on structural integrity are reviewed. (orig.)

160

Behavior of surface flaws in reactor pressure vessels under thermal-shock loading conditions  

International Nuclear Information System (INIS)

This paper discusses the conditions necessary for crack propagation during a loss of coolant accident (LOCA), the detailed behavior of the cracks under these specific conditions, and an experimental program designed to determine the validity of the method of analysis (linear-elastic fracture mechanics) used to predict the behavior of flaws under severe thermal-shock loading conditions. A detailed fracture-mechanics analysis of the LOCA thermal shock was performed to help establish the scope of the experimental program. The results of this analysis indicate that present-generation and future pressurized water reactor (PWR) vessels will not experience excessive crack propagation. This is also true of earlier PWR vessels, which contain rather high concentrations of copper. The agreement between experimental results and the LEFM analysis was very good. 14 refs

 
 
 
 
161

Entropy Generation in Pressure Gradient Assisted Couette Flow with Different Thermal Boundary Conditions  

Directory of Open Access Journals (Sweden)

Full Text Available The present paper is concerned with an analytical study of entropy generation in viscous, incompressible Couette flow between a stationary plate and a moving plate. The flow induced by the moving plate is assisted by a constant pressure gradient along the flow direction. Four different combinations of thermal boundary conditions are investigated: (a plates at different temperatures, (b stationary plate at a fixed temperature and moving plate subjected to a constant heat flux, (c stationary plate at a fixed temperature and convection at the moving plate, and (d convection at both plates. Besides the velocity and temperature profiles, dimensionless results are presented for the entropy generated due to heat transfer, the entropy generated due to viscous dissipation, and the total entropy generation. These results illustrate the effect of pressure gradient, temperature asymmetry, heat flux, convection Biot numbers, and ambient temperatures. For certain combinations of thermal variables, the total entropy generated is minimized.

Abdul Aziz

2006-05-01

162

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)

163

Toward measurements of volatile behavior at realistic pressure and temperature conditions in planetary deep interiors. (Invited)  

Science.gov (United States)

Laboratory studies of volatiles at high pressure are constantly challenged to achieve conditions directly relevant to planets. While dynamic compression experiments are confined to adiabatic pathways that frequently exceed relevant temperatures due to the low densities and bulk moduli of volatile samples, static compression experiments are often complicated by sample reactivity and mobility before reaching relevant temperatures. By combining the speed of dynamic compression with the flexibility of experimental path afforded by static compression, optical spectroscopy measurements in volatiles such as H, N, and Ar have been demonstrated at previously-unexplored planetary temperature (up to 11,000 K) and pressure (up to 150 GPa). These optical data characterize the electronic properties of extreme states and have implications for bonding, transport, and mixing behavior in volatiles within planets. This work was conducted in collaboration with D.A. Dalton and A.F. Goncharov (Carnegie Institution of Washington) and M.F. Mahmood (Howard University).

McWilliams, R. S.

2013-12-01

164

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)

165

Windsock memory conditioned RAM (Co-Ram) pressure effect: forced reconnection in the Earth's magnetotail  

CERN Document Server

Magnetic reconnection (MR) is a key physical concept explaining the addition of magnetic flux to the magnetotail and closed flux lines back-motion to the dayside magnetosphere. This scenario elaborated by \\citet{dung63}, can explain many aspects of solar wind-magnetosphere interaction processes, including substorms. However, neither the Dungey model nor its numerous modifications were able to explain fully the onset conditions for MR in the tail. In this paper, we introduce new onset conditions for forced MR in the tail. We call our scenario the "windsock memory conditioned ram pressure effect". Our non-flux-transfer associated forcing is introduced by a combination of large-scale windsock motions exhibiting memory effects and solar wind dynamic pressure actions on the nightside magnetopause during northward oriented IMF. Using global MHD GUMICS-4 simulation results, upstream data from WIND, magnetosheath data from Cluster-1 and distant-tail data from the two-probe ARTEMIS mission, we show that the simultaneo...

Vörös, Z; Khodachenko, M; Honkonen, I; Janhunen, P; Palmroth, M

2014-01-01

166

Experimental study on two-phase flow and heat transfer through narrow rectangular channel under middle-low pressure condition  

International Nuclear Information System (INIS)

Two-phase boiling experiments have been performed in narrow rectangular channel at middle-low pressure. Based on the measured pressure drop and temperature across the test section, the effect of pressure and mass flow rate has been analyzed. Saturated boiling heat transfer was studied. And a new correlation has been developed for saturated boiling heat transfer under middle-low pressure condition. Additionally, based on the predigested one-dimensioned model of two-phase boiling flow, a new correlation has been developed for two-phase flow pressure drop under middle-low pressure condition. Furthermore, F parameter has been defined to expresses proportion of moistening perimeter between steam-phase and wall in this new correlation. The calculation results of new correlation predict well the experimental results. The average saturated boiling heat transfer coefficient is great impacted by system pressure, mass flow and heat flux. (authors)

167

Windsock memory COnditioned RAM (CO-RAM) pressure effect: Forced reconnection in the Earth's magnetotail  

Science.gov (United States)

Magnetic reconnection (MR) is a key physical concept explaining the addition of magnetic flux to the magnetotail and closed flux lines back-motion to the dayside magnetosphere. This scenario elaborated by Dungey (1963) can explain many aspects of solar wind-magnetosphere interaction processes, including substorms. However, neither the Dungey model nor its numerous modifications were able to explain fully the onset conditions for MR in the tail. In this paper, we introduce new onset conditions for forced MR in the tail. We call our scenario the "windsock memory conditioned ram pressure effect." Our nonflux transfer-associated forcing is introduced by a combination of the large-scale windsock motions exhibiting memory effects and solar wind dynamic pressure actions on the nightside magnetopause during northward oriented interplanetary magnetic field (IMF). Using global MHD Grand Unified Magnetosphere Ionosphere Coupling Simulation version 4 simulation results, upstream data from Wind, magnetosheath data from Cluster 1 and distant tail data from the two-probe Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun mission, we show that the simultaneous occurrence of vertical windsock motions of the magnetotail and enhanced solar wind dynamic pressure introduces strong nightside disturbances, including enhanced electric fields and persistent vertical cross-tail shear flows. These perturbations, associated with a stream interaction region in the solar wind, drive MR in the tail during episodes of northward oriented interplanetary magnetic field (IMF). We detect MR indirectly, observing plasmoids in the tail and ground-based signatures of earthward moving fast flows. We also consider the application to solar system planets and close-in exoplanets, where the proposed scenario can elucidate some new aspects of solar/stellar wind-magnetosphere interactions.

Vörös, Z.; Facskó, G.; Khodachenko, M.; Honkonen, I.; Janhunen, P.; Palmroth, M.

2014-08-01

168

High pressure gas pipeline in Artic conditions; Hochdruck-Gaspipeline in arktischen Gebieten  

Energy Technology Data Exchange (ETDEWEB)

More than 2000 km north of moscow, in the timan-pechora region, the kharyaga oil field is located. Gas is transported through a 9.5 km long 6{sup ''} pipeline with an operating pressure of up to 356 bar to a field injection well and is reinjected into the reservoir. The installations are erected in Artic conditions, with ambient temperatures of down to -56 C. The pipeline is laid above ground on piled supports, heat insulated in permafrost conditions. Due to environmental conditions the construction of pipelines is carried out during winter season. A particular difficulty for the design was the fact that Russian as well as western norms and standards for design and material selection had to be fulfilled. In October 2003 the pipeline has been successfully pressure tested with a pressure of 534 bar and put in operation. (orig.) [German] Mehr als 2000 km noerdlich von Moskau, in der Region Timan-Pechora, liegt das Kharjaga Oelfeld. Durch eine 9,5 km lange 6{sup ''} Pipeline mit einem Betriebsdruck von bis zu 356 bar wird Gas zu einer Sondenstation transportiert und wieder in die Lagerstaette eingepresst. Die Anlage wird unter arktischen Bedingungen errichtet und betrieben, mit Temperaturen bis -56 C. In dieser Gegend gibt es durchgaengig Permafrostboden. Deshalb ist die Leitung oberirdisch auf Pfaehlen installiert. Auf Grund der Umweltbedingungen kann der Bau nur im Winter erfolgen. Eine besondere Schwierigkeit fuer die Planung war die Tatsache, dass sowohl westliche als auch russische Normen beruecksichtigt werden mussten. Im Oktober 2003 wurde die Wasserdruckpruefung mit einem Druck von 534 bar erfolgreich durchgefuehrt und die Leitung in Betrieb genommen. (orig.)

Heinz, C. [ILF Beratende Ingenieure GmbH, Muenchen (Germany)

2004-03-01

169

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

170

Numerical characterization of pressure instabilities in a vaned centrifugal pump under partload condition  

Science.gov (United States)

This paper studies the hysteresis/saddle phenomena of the head-drop in a scaled model pump turbine using CFD methods. This lag was induced by complicated flow patterns, which influenced the reliability of rotating machine that was analysed by a commercial code with DES model for computing turbulence. Analyses were carried out on the pressure signals both in frequency and time-frequency domains at full and part load conditions. The results highlighted the remarkable interaction between the unsteady structures in diffuser and return.

Yang, J.; Pavesi, G.; Cavazzini, G.; Yuan, S. Q.

2013-12-01

171

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

172

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

173

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.)

174

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, L.; Lopes, N.

2011-01-01

175

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

176

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.

177

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

Science.gov (United States)

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.

Chirkov, D.; Avdyushenko, A.; Panov, L.; Bannikov, D.; Cherny, S.; Skorospelov, V.; Pylev, I.

2012-11-01

178

Safety criterion for burnout of the plate-type fuel in pressurized conditions  

International Nuclear Information System (INIS)

The reduced enrichment program for JMTR is now underway and the core conversion to LEU (Low Enrichment Uranium) is scheduled to be made in 1993. Consistent with the safety guide which have been recently developed for research and test reactors in Japan, the safety analysis for the JMTR LEU conversion was conducted. In the safety analysis, DNB (Departure from Nucleate Boiling) heat flux correlation for the JMTR downflow condition was reconsidered because recent studies on burnout show that DNB heat fluxes with thin rectangular channels under low flow rate and low pressure conditions are much lower than predicted values by conventional DNB correlations. Available DNB data, however, are very limited for the JMTR operation pressure range, so that DNB experiments were conducted simulating the JMTR fuel subchannel. Based mainly on the present experimental data, the DNB correlations scheme composed of three correlations was selected for the JMTR safety analysis. Errors of the correlations scheme with experimental data were evaluated in order to determine the allowable limit of the minimum DNB ratio for preventing fuel failure. (author)

179

Stress corrosion cracking of low-alloy reactor pressure vessel steels under boiling water reactor conditions  

Science.gov (United States)

The stress corrosion cracking (SCC) behaviour of different reactor pressure vessel (RPV) steels and weld filler/heat-affected zone materials was characterized under simulated boiling water reactor (BWR) normal water (NWC) and hydrogen water chemistry (HWC) conditions by periodical partial unloading, constant and ripple load tests with pre-cracked fracture mechanics specimens. The experiments were performed in oxygenated or hydrogenated high-purity or sulphate/chloride containing water at temperatures from 150 to 288 °C. In good agreement with field experience, these investigations revealed a very low susceptibility to SCC crack growth and small crack growth rates (BWR/NWC and material conditions. Critical water chemistry, loading and material conditions, which can result in sustained and fast SCC well above the 'BWRVIP-60 SCC disposition lines' were identified, but many of them generally appeared atypical for current optimized BWR power operation practice or modern RPVs. Application of HWC always resulted in a significant reduction of SCC crack growth rates by more than one order of magnitude under these critical system conditions and growth rates dropped well below the 'BWRVIP-60 SCC disposition lines'.

Seifert, H. P.; Ritter, S.

2008-01-01

180

Stress corrosion cracking of low-alloy reactor pressure vessel steels under boiling water reactor conditions  

International Nuclear Information System (INIS)

The stress corrosion cracking (SCC) behaviour of different reactor pressure vessel (RPV) steels and weld filler/heat-affected zone materials was characterized under simulated boiling water reactor (BWR) normal water (NWC) and hydrogen water chemistry (HWC) conditions by periodical partial unloading, constant and ripple load tests with pre-cracked fracture mechanics specimens. The experiments were performed in oxygenated or hydrogenated high-purity or sulphate/chloride containing water at temperatures from 150 to 288 deg. C. In good agreement with field experience, these investigations revealed a very low susceptibility to SCC crack growth and small crack growth rates (<0.6 mm/year) under most BWR/NWC and material conditions. Critical water chemistry, loading and material conditions, which can result in sustained and fast SCC well above the 'BWRVIP-60 SCC disposition lines' were identified, but many of them generally appeared atypical for current optimized BWR power operation practice or modern RPVs. Application of HWC always resulted in a significant reduction of SCC crack growth rates by more than one order of magnitude under these critical system conditions and growth rates dropped well below the 'BWRVIP-60 SCC disposition lines'

 
 
 
 
181

Freezing and Melting of 3D Complex Plasma Structures under Microgravity Conditions Driven by Neutral Gas Pressure Manipulation  

International Nuclear Information System (INIS)

Freezing and melting of large three-dimensional complex plasmas under microgravity conditions is investigated. The neutral gas pressure is used as a control parameter to trigger the phase changes: Complex plasma freezes (melts) by decreasing (increasing) the pressure. The evolution of complex plasma structural properties upon pressure variation is studied. Theoretical estimates allow us to identify the main factors responsible for the observed behavior.

182

Metamorphism at ultrahigh-temperature and ultrahigh-pressure conditions: what comes first?  

Science.gov (United States)

Recent discoveries of diamond, and coesite, in several metamorphic terranes show that ultrahigh-pressure metamorphism is a rather common phenomenon in orogenic belts of various ages worldwide. Whereas models applicable for UHP belts with low-temperature imprint exist, the genesis of ultrahigh-pressure and ultrahigh-temperature rocks is still not well understood. Our study of ultrahigh-pressure units of the Bohemian Massif, where diamonds have been found in various rocks including high-pressure granulites characteristic of the internal zone of the European Variscan Belt, helps to shed some light on these processes. Diamond and coesite occur in the northern part of the Bohemian Massif as an inclusion in garnet, kyanite and zircon in the rocks classically described as HP granulites. And indeed, composition of the major phases corresponds to equilibration under conditions of high-pressure granulite metamorphism. However, presence of UHP index phases, omphacite relics enclosed in garnet in intermediate lithologies, and associated mafic UHP eclogites suggest that these rocks are ultrahigh-pressure rocks, or UHP eclogites. Garnet lherzolites associated with the North Bohemian UHP rocks do not contain spinel-bearing coronas around garnets; these are rimmed by hornblende instead. Garnets are largely homogeneous, with only a slight MgO decrease in a narrow rim. An inclusion of spinel has been found in garnet. Mafic eclogite is devoid of diopside and plagioclase symplectites after omphacite due to low silica content, but contains characteristic symplectites of pargasite and quartz indicative of the decompression. In summary, both mantle and crustal rocks record prograde evolution with P-T increase, UHP-HT-UHT peak conditions, and rapid cooling during their exhumation. It is obvious that our petrological, P-T and geochronological data show striking similarity with the UHP unit in the Erzgebirge, to the N from our area. Although the north Bohemian crystalline basement is poorly exposed, an E-W trend of the lithological boundaries that is consistent with the structures in the Erzgebirge is documented by numerous boreholes. Steep E-W- trending foliations in northern Bohemian UHP area are overprinted by a flat-lying ones in the Erzgebirge, whereas E-W strike of the lineations is characteristic of both areas. The fabric can be interpreted in terms of an initial vertical extrusion of the UHP rocks from mantle depths followed by W-directed (for the Erzgebirge) flow and emplacement in mid crustal levels, related to the late Variscan N-S compression. Association of the mantle and both mafic and intermediate-felsic UHP-UHT crustal rocks with similar peak P-T conditions relates to a deep subduction of predominantly felsic continental crust. Present setup of the units is consistent with the early extrusion of the deepest subducted crustal material in an exhumation channel without temperature increase, allowing preservation of their UHP assemblages. Only then the units showing high-temperature overprint due to the interaction with the hot asthenosphere, without UHP indicators preserved, are exhumed. Thus the UHT comes after UHP.

Kotkova, Jana; Schmädicke, Esther; Kroner, Uwe

2014-05-01

183

The investigation of argon diffusion in phlogopite under high pressure conditions  

Science.gov (United States)

The present study deals with assessment of pressure effect on the mechanism of bleeding an argon from mica at high temperatures and pressures. The influence of pressure on the diffusion of argon in crustal conditions is not significant (Harrison et al., 2009), while in the mantle conditions, should be significant. The authors suggest that the findings will help to better understand the behavior of K/Ar isotopic system in mica under the lower crust and mantle, including xenoliths transport by kimberlite melt. The experiment was made by using high-pressure spacer "split-sphere" (BARS - 300). Phlogopite from veins cutting metamorphic rocks from the Sludyanka number 2 quarry was used as a testing material. Inclusions of other minerals were not found in the original phlogopite crystal. Chemical composition of phlogopite is homogeneous. 8 experiments was made at a constant pressure of 30 kbar and different temperature and duration: 20 degrees Celsius, 20 minutes; 700 degrees Celsius, 20 minutes; 800 degrees Celsius, 10 minutes; 800 degrees Celsius, 20 minutes; 800 degrees Celsius, 30 minutes; 900 degrees Celsius, 20 minutes; 1000 degrees Celsius, 20 minutes; 1100 degrees Celsius, 20 minutes. According the results of SEM-observation, there is no signs of recrystallization and solid state transformations and melting of phlogopite. It's chemical composition is identical to that of the original phlogopite. Diffractograms of phlogopites after the experiments are similar to the diffractograms of the original phlogopites. Research results of IR spectroscopy, together with the results of SEM and microprobe analysis suggest that phlogopite dehydroxylation in the temperature range T = 700-900 degrees Celsius was negligible. Numerical simulation of the behavior of radiogenic argon in phlogopite at high temperatures and pressure was performed using «Diffarg» software finite differences algorithm, based on the mechanism of bulk thermally activated diffusion (Wheeler, 1996). The size of the effective diffusion domain of mica was considered to be 100-150 microns, when modeling (Baxter, 2010). Comparison of results of simulations and experiments suggests that the mobility of argon isotopes in phlogopite at high temperatures and pressure is well described by the mechanism of thermally activated volume diffusion. Stepwise release of argon in a vacuum experiment was also conducted. The activation energy of 207,714 J/mol was calculated from the slope of the line on the Arrhenius chart. This value is consistent with data obtained by other authors in hydrothermal experiments (Baxter, 2010). The work was supported by the grant of the President of Russia MK-3240.2014.5. Baxter E.F. Diffusion of Noble Gases in Minerals // Reviews in Mineralogy & Geochemistry. 2010. V.72. P.509-557. Harrison T.M., Celerier J., Aikman A.B., Hermann J., Heizler M.T. Diffusion of 40Ar in muscovite // Geochim Cosmochim Acta. 2009. V.73. P.1039-1051. Wheeler J. Diffarg: A program for simulating argon diffusion profiles in minerals // Computers & Geosciences. 1996. V. 22(8). P. 919-929.

Yudin, Denis; Korzhova, Sophia; Travin, Alexey; Zhimulev, Egor; Murzintsev, Nikolay; Moroz, Tatiana

2014-05-01

184

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

185

Analysis of pressure locking and thermal binding conditions on shutdown cooling system suction isolation valves  

International Nuclear Information System (INIS)

Shutdown Cooling System (SCS) suction isolation valves for Yonggwang Nuclear Units 5 and 6 (YGN 5 and 6) had been selected as the valves susceptible to pressure locking and thermal binding (PLTB) phenomena considering valves' allowable internal leakage and various operating conditions. To prevent the anticipated PLTB phenomena, the isolation valve type was changed from the flexible-wedge gate valve to the double-disk gate valve with the drilled hole on the upstream disk. During plant pre-operational hydrostatic tests, however, the technical issue regarding the valve type change was raised due to the inherent difficulty in pressurizing the valve downstream piping, which was caused by the drilled hole. In order to resolve this technical issue, the technical adequacy of the valve type change was justified through the identification of the PLTB conditions on the SCS isolation valves using brief hand calculations and FLUENT code simulations. From these calculations and simulations, it was found that the upstream fluid temperatures of the second and third valves were almost the same as the ambient temperature for the case of no leakage in the isolation valves. However, if there were leakage through each isolation valve up to the maximum allowable leakage in the plant Technical Specification, the upstream fluid temperature of the farthest third isolation valve even increased enough to cause the PLTB phenomena. In these analyses, the valve leakage and turbulent penetration duvalve leakage and turbulent penetration due to high-velocity flow in the RCS hot leg were identified as dominant factors which cause the PLTB conditions such as a valve bonnet overpressurization and a thermal difference between both ends of the valve disk. (author)

186

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

187

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

188

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

189

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)

190

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

Directory of Open Access Journals (Sweden)

Full Text Available 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. The Pearson correlation coefficient between ICP and IOP was calculated, the fisher line discriminated analysis to evaluate the effectivity of using IOP to predict the ICP level. Results A significant correlation between ICP and IOP was found. ICP was correlated significantly with IOP of the right eyes (p? Conclusion Our data suggested that although a significant correlation exists between ICP and IOP, caution needs to be taken when using IOP readings by Goldmann applanation tonometer as a surrogate for direct cerebrospinal fluid pressure measurement of ICP.

Li Zhen

2012-08-01

191

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

Energy Technology Data Exchange (ETDEWEB)

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.

Ezato, Koichiro [Blanket Engineering Lab, Department of Fusion Research Establishment, Japan Atomic Energy Research Institute, JAERI, Naka-shi, Naka-gun, Ibaraki-ken 311-0193 (Japan)]. E-mail: ezatok@fusion.naka.jaeri.go.jp; Suzuki, Satoshi [Blanket Engineering Lab, Department of Fusion Research Establishment, Japan Atomic Energy Research Institute, JAERI, Naka-shi, Naka-gun, Ibaraki-ken 311-0193 (Japan); Dairaku, Masayuki [Blanket Engineering Lab, Department of Fusion Research Establishment, Japan Atomic Energy Research Institute, JAERI, Naka-shi, Naka-gun, Ibaraki-ken 311-0193 (Japan); Akiba, Masato [Blanket Engineering Lab, Department of Fusion Research Establishment, Japan Atomic Energy Research Institute, JAERI, Naka-shi, Naka-gun, Ibaraki-ken 311-0193 (Japan)

2006-02-15

192

Case Study for the Numerical Instabilities of the MATRA at Low Flow and Low Pressure Conditions  

International Nuclear Information System (INIS)

Subchannel analysis codes are very useful and have important roles in analyzing the thermal performance of nuclear reactors. The COBRA and its descendants, including the MATRA, have been widely used as a subchannel analysis code. These codes are known to be unstable for certain conditions. There have been many efforts to resolve unstableness and increase the stability of the subchannel analysis codes. Cuta et al. assessed the stabilities of subchannel analysis codes, VIPRE-01, COBRA-3C, COBRA-IV-I, and LYNX-T with five different experimental data. They found that those codes are unstable for certain cases in a steady state. And they suggested that the cause of unstableness of those codes is the way the lateral pressure difference is updated in the momentum equation. They introduced the crossflow parameter as a measure of the relative numerical stability

193

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

194

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

195

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

196

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

197

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

198

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

199

Modelling of laminar spray flames in high-pressure conditions; Modellierung laminarer Sprayflammen unter Hochdruckbedingungen  

Energy Technology Data Exchange (ETDEWEB)

The structure of laminar spray diffusion flames is investigated in counterflow configuration using numerical methods in a spray of liquid oxygen with hydrogen as carrier gas. The model considers detailed chemistry and detailed transport. The conditions selected require an extension of the model to consider the transport properties at cryogenic inlet temperatures as well as changed phase equilibria of binary mixtures at high pressure. The parametric dependence of the flame structure on the elongation velocity and the global equivalence ratio is presented and discussed. The model enables calculation of quenching conditions which are a fundamental parameter in simulating turbulent spray diffusion flames by means of a flamelet approach. [German] Die Struktur laminarer Spraydiffusionsflammen wird in der Gegenstromkonfiguration mittels numerischen Methoden untersucht. Ein Spray aus fluessigem Sauerstoff mit Traegergas Wasserstoff wird gegen Wasserstoff bei hohem subkritischen Druck und mit kryogener Eintrittstemperatur eingeduest. In dem Modell werden detaillierte Chemie und detaillierter Transport beruecksichtigt. Die gewaehlten Bedingungen erfordern die Modellerweiterung bezueglich der Transporteigenschaften bei kryogenen Eintrittstemperaturen sowie die Beruecksichtigung veraenderter Phasengleichgewichte binaerer Mischungen bei Hochdruck. Parametrische Abhaengigkeiten der Flammenstruktur von der Streckungsgeschwindigkeit und dem globalen Aequivalenzverhaeltnis werden dargestellt und diskutiert. Das Modell ermoeglicht die Bestimmung von Verloeschbedingungen, die fuer die Simulation turbulenter Spraydiffusionsflammen mittels eines Flamelet-Ansatzes grundlegend sind. (orig.)

Schlotz, D.; Gutheil, E.

1999-07-01

200

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

 
 
 
 
201

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.)

202

Equation of state of Al-bearing perovskite to lower mantle pressure conditions  

Science.gov (United States)

Al2O3 is estimated to total 4 to 5 mol% in all mantle compositional models, and is believed to be incorporated into (Mg,Fe)SiO3-perovskite at lower mantle conditions. Using synchrotron X-ray diffraction, we have measured the 300 K equation of state of a perovskite with XAl=Al/(Al+Mg+Si)=.077, up to 32 GPa. A least squares refinement of two independent data sets yields the following equation of state parameters V0=163.52(3) ų, K0=229(4) GPa, and K0=2.5(4). These values allow us to assess the most probable substitution mechanism for aluminium into perovskite at pressure conditions of the shallow lower mantle. Al3+ is likely to be incorporated in place of Si4+ in the octahedral site of perovskite, hence requiring the creation of oxygen vacancies for charge balance. As a consequence, aluminous perovskites may have a high affinity for water. The enhanced compressibility of aluminous perovskite certainly has also strong geophysical and geochemical implications, as it may revive perovskite-rich lower mantle models.

Daniel, Isabelle; Cardon, Hervé; Fiquet, Guillaume; Guyot, François; Mezouar, Mohamed

203

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

204

Magnetite reactivity in representative conditions of the secondary circuit of pressurized water reactors  

International Nuclear Information System (INIS)

In the secondary circuit of Pressurized Water Reactors (PWR), magnetite deposits lead to steam generators (SG) fouling, which decreases thermal performances and enhances stress corrosion cracking (SCC). The aim of this study is to improve the understanding of magnetite particles behaviour and their reactivity in the secondary circuit conditions. Experimental tests investigated the fast thermal decomposition of hydrazine, injected in the secondary circuit to eliminate oxygen. Temperature, pH, and catalytic properties of materials surfaces have an influence on the kinetics of hydrazine decomposition. A predictive model was proposed. Growing, transport and deposits of iron oxides, essentially formed with magnetite, responsible of the steam generator fouling, were studied in the experimental loop FORTRAND, Formation and Transport of Deposits. Surface characterizations show that magnetite is the corrosion product formed on carbon steel and stainless steel at 220 C, and goethite is formed at room temperature on stainless steel. Results indicate also that the effect of different amines, used in the secondary circuit, on the soluble iron is principally due to their effect on the pH. Performed tests highlight transport and deposition of magnetite particles in the loop. Deposits formed in the SG could promote SCC of tubes by sorption and reduction of sulfates. To reproduce secondary circuit conditions, studies of sorption were made in reducing medium imposed by hydrazine. At 275 C, the presence of hydrazine has an effect on the speciation of sulfates in solution but does not seem to influence the sorption nor to lead to H2S(g) emission predicted by thermodynamic calculations. These experimental results are used to predict sulfur and iron species behaviour in the secondary circuit. Low pH conditioning enhances soluble iron concentration, consequently iron transport in the SG. Sulfides are the most probable sulfur species in flow-restricted areas of SG, harmful for stress corrosion cracking. (author)

205

NUMERICAL SIMULATION ON EFFECTS OF TEST CONDITIONS ON MEASURED SWELLING PRESSURE OF COMPACTED BENTONITE BY SWELLING MODEL  

Science.gov (United States)

In the current concept of repository for radioactive waste disposal, compacted bentonite as well as bentonite-based material will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. In most cases, swelling pressure is one of the most important characteristics of bentonite as an engineered barrier. However measured swelling pressure by laboratory tests often varies considerably even if index parameter, such as eff ective clay density, is constant. Thus, existing study already revealed that difference among swelling pressure test apparatuses was the most influencing factor. In this study, swelling model of unsaturated bentonite is proposed for simulating the effects of three test conditions, which are deformability of swelling pressure test apparatuses, height of specimens and initial water content, on measured swelling pressure. Consequently, it is revealed that the effects of three test conditions on swelling pressures can be simulated by the model and that scattering of measured swelling pressure is mostly attributable to deformability of swelling pressure test apparatuses and height of specimens.

Tanaka, Yukihisa

206

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

207

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

International Nuclear Information System (INIS)

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/m2 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)

208

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

209

Effects interaction of ion beams with electrolyte surface at atmospheric pressure glow discharge conditions  

International Nuclear Information System (INIS)

Authors describe the ion beams interaction with liquid electrolyte surface (water solution of sodium chloride) at conditions of atmospheric pressure glow discharge plasma. The glow discharge is ignited between metal anode and liquid electrolyte surface as cathode. It was noted that the increasing dissolved substance concentration leads to abrupt change of discharge view: from 'spreading' at low concentration to 'arc form' at 2.5 times concentration increasing. The 'arc form' is changed without variation of voltage and current. The form changes occur during 0.25 second. It was assumed that there is the back connection between dissolved substances concentration and discharge properties. The estimations of positive ions bombarding liquid surface are presented. The main ion is H3O+. The energetic expenditures on the one water molecule transfer from solution into gas phase were made. The values are 1-2 order less then expenditure for metallic cathode. The suggestion of liquid cathode state in the thin surface layer was made. (authors)

210

Numerical simulation of pressure fluctuation of a pump-turbine with MGV at no-load condition  

Science.gov (United States)

In order to analyse the pressure fluctuation caused by misaligned guide vanes (MGV) during starting period at no-load condition, 3-D (three dimensional), unsteady flows in a pump-turbine were numerically studied. Pressure fluctuations of different points at no-load condition are obtained. Fast Fourier Transform(FFT) was used to analyse the frequency spectrum of pressure fluctuations. The amplitude and dominant frequency of pressure fluctuation at vaneless space between the runner and guide vane, as well as the inlet of draft tube, was investigated. The amplitude of pressure fluctuation of the pump-turbine with MGV device is twice that of synchronous vanes. This might be caused by the non-uniform flow in the pump-turbine due to the pre-opened guide vanes. The pump-turbine with synchronous vanes has a low frequency which is 0.33fn, while the low frequency changes into 0.63fn when the MGV device is used. The vortex rope in the draft tube is large than that of synchronize vanes. Resultsof pressure fluctuations with synchronous vanes agree with each other between computational and testing results. The numerical study of pressure fluctuations with MGV can provide a basic understanding for the improvement of the instability of a pump-turbine.

Liu, J. T.; Liu, S. H.; Sun, Y. K.; Wu, Y. L.; Wang, L. Q.

2012-11-01

211

Numerical simulation of pressure fluctuation of a pump-turbine with MGV at no-load condition  

International Nuclear Information System (INIS)

In order to analyse the pressure fluctuation caused by misaligned guide vanes (MGV) during starting period at no-load condition, 3-D (three dimensional), unsteady flows in a pump-turbine were numerically studied. Pressure fluctuations of different points at no-load condition are obtained. Fast Fourier Transform(FFT) was used to analyse the frequency spectrum of pressure fluctuations. The amplitude and dominant frequency of pressure fluctuation at vaneless space between the runner and guide vane, as well as the inlet of draft tube, was investigated. The amplitude of pressure fluctuation of the pump-turbine with MGV device is twice that of synchronous vanes. This might be caused by the non-uniform flow in the pump-turbine due to the pre-opened guide vanes. The pump-turbine with synchronous vanes has a low frequency which is 0.33fn, while the low frequency changes into 0.63fn when the MGV device is used. The vortex rope in the draft tube is large than that of synchronize vanes. Resultsof pressure fluctuations with synchronous vanes agree with each other between computational and testing results. The numerical study of pressure fluctuations with MGV can provide a basic understanding for the improvement of the instability of a pump-turbine.

212

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

213

Raman spectroscopy of cubic boron nitride under extreme conditions of high pressure and temperature  

Science.gov (United States)

Raman spectroscopy in the diamond cell has been used to determine the pressure dependence at high temperature of the transverse optical phonon (TO) of cubic boron nitride to 1750 K at a maximum pressure of 40 GPa, and up to 2300 K at 26 GPa. We have identified extrinsic (volume-dependent) and intrinsic contributions to the experimental frequency and find that the intrinsic contribution is only weakly pressure-dependent. These data establish a high-temperature pressure scale to at least 1700 K. Ab initio calculations to 80 GPa are in excellent agreement with the experiment at low temperatures.

Goncharov, Alexander F.; Crowhurst, Jonathan C.; Dewhurst, J. K.; Sharma, S.

2005-09-01

214

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

215

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

216

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)

217

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

218

Visualization study of the subcooled flow boiling under various pressure condition  

International Nuclear Information System (INIS)

The behavior of bubbles in subcooled flow boiling have been investigated photographically in vertical rectangular channel, one-side heat heating with aid of a digital still camera. The test has a flow area of 10 x 10 mm and heated area of 3 x 100 mm. The test hs ben performed for de-ionized water with variation of pressure, heat flux, mass flux and local quality. The various parameters including average bubble size were measured near the heated surface with photos and image processing program. Consequently, as the pressure increased, the average bubble size decrease but the number of bubbles increased. As the pressure increased, the temperature difference between heater wall and bulk dramatically increased at pressures of 1.50 ? 4.00 MPa. When the pressure exceeded about 4.00 MPa, the differential temperature dramatically decreased

219

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

220

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

 
 
 
 
221

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.)

222

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.

223

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

224

DESIGNED PARAMETERS FOR NOZZLES OF LOCAL SMALL-JET LOW-PRESSURE IRRIGATION NETWORK FOR THE CONDITIONS OF PROTECTED GROUND ????????? ????????? ??????? ????????? ????????????? ????????????? ???????????? ???? ??? ??????? ????????? ??????  

Directory of Open Access Journals (Sweden)

Full Text Available Hydraulic design of water outlets installed (mounted on water application pipelines of low-pressure small-jet irrigation network when growing gerbera flowers under the conditions of protected ground is given in the paper. Relationships for estimating coefficients of hydraulic resistance and discharge coefficients for different nozzles are deduced

Pavlyukova E. D.

2011-11-01

225

40 CFR 86.1312-2007 - Filter stabilization and microbalance workstation environmental conditions, microbalance...  

Science.gov (United States)

...using the dewpoint temperature in the Magnus formula...Where: Pw =vapor pressure of liquid water, kPa. Tdp =dewpoint temperature, °C. (B) Calculate...using the ideal gas relationship and molecular weights... . P=barometric pressure, kPa. Pw...

2010-07-01

226

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

227

Volume based vs. time based chromatograms: reproducibility of data for gradient separations under high and low pressure conditions.  

Science.gov (United States)

A critical aspect in fast gradient separations carried out under constant pressure, in the very high pressure liquid chromatography (VHPLC) mode is that time-based chromatograms may not yield highly reproducible separations. A proposed solution to improve the reproducibility of these separations involves plotting the chromatograms as functions of the volume eluted vs. UV absorbance instead of time vs. UV. To study the consequences of using the volume-based rather than the time-based chromatograms, separations were first performed under low pressures that do not generate significant amounts of heat and for which the variations of the eluent density along the columns are negligible. Secondly, they were performed under very high pressures that do generate heat and measurable variations of the local retention factor and eluent density along the column. Comparison of the results provides estimates of the improvements obtained when volume based chromatograms are used in gradient analyses. Using a column packed with fully porous particles, four different types of methods and several sets for each method were used to perform the gradient elution runs: two sets of constant flow rate operations, four sets of constant pressure operations, two sets of constant pressure operations with programmed flow rate, and one set using the constant heat loss approach. The differences between time-based and volume-based chromatograms are demonstrated by using eight replicates of early, middle, and last eluting peaks. The results show that volume-based chromatograms improve the retention time reproducibility of the four constant pressure methods by a factor of 3.7 on average. If the column is not thermally conditioned prior to performing a long series of separations, flow controlled methods (constant flow rate, programmed constant pressure, and constant wall heat approaches) are more precise. If one gradient run is used to bring the column to a relatively stable temperature, constant pressure separations have a factor of 3 times better reproducibility of retention times with respect to constant flow rate gradient separations. PMID:24717849

Stankovich, Joseph J; Gritti, Fabrice; Stevenson, Paul G; Vajda, Péter; Beaver, Lois Ann; Guiochon, Georges

2014-05-23

228

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

229

Scaling of conditional Lagrangian time correlation functions of velocity and pressure gradient magnitudes in isotropic turbulence  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study Lagrangian statistics of the magnitudes of velocity and pressure gradients in isotropic turbulence by quantifying their correlation functions and their characteristic time scales. It has been found that the Lagrangian time-correlations of the velocity and pressure gradient tensor and vector elements scale with the locally-defined Kolmogorov time scale, defined from the box-averaged dissipation-rate and viscosity. In this work, we study the Lagrangian time-correlatio...

Yu, Huidan; Meneveau, Charles

2009-01-01

230

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.

231

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

232

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

233

The Effects of Temperature, Pressure, and Humidity Variations on 100 Meter Sprint Performances  

CERN Document Server

It is well known that ``equivalent'' sprint race times run with different accompanying wind speeds or at different altitudes are anything but equivalent races. The drag force acting on a sprinter is a function of air density and the relative wind speed, where the former has traditionally been calculated using the race venue's elevation above sea level. However, air density variation is dependent on more than just altitude. This work will quantify how changes in air temperature, barometric pressure, and humidity levels influence 100 m sprint performances. When these effects are considered in combination, the corrections to performances can be very large. The results suggest that a non-negligible difference in race times can be expected for ``equivalent'' performances run with the same wind speed at the same venue or physical altitude, but under different atmospheric conditions.

Mureika, J R

2005-01-01

234

Real-Time Optical Monitoring of Flow Kinetics and Gas Phase Reactions Under High-Pressure OMCVD Conditions  

Science.gov (United States)

This contribution addresses the real-time optical characterization of gas flow and gas phase reactions as they play a crucial role for chemical vapor phase depositions utilizing elevated and high pressure chemical vapor deposition (HPCVD) conditions. The objectives of these experiments are to validate on the basis of results on real-time optical diagnostics process models simulation codes, and provide input parameter sets needed for analysis and control of chemical vapor deposition at elevated pressures. Access to microgravity is required to retain high pressure conditions of laminar flow, which is essential for successful acquisition and interpretation of the optical data. In this contribution, we describe the design and construction of the HPCVD system, which include access ports for various optical methods of real-time process monitoring and to analyze the initial stages of heteroepitaxy and steady-state growth in the different pressure ranges. To analyze the onset of turbulence, provisions are made for implementation of experimental methods for in-situ characterization of the nature of flow. This knowledge will be the basis for the design definition of experiments under microgravity, where gas flow conditions, gas phase and surface chemistry, might be analyzed by remote controlled real-time diagnostics tools, developed in this research project.

Dietz, N.; McCall, S.; Bachmann, K. J.

2001-01-01

235

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

236

Convective heat and mass transfer in water at super-critical pressures under heating or cooling conditions in vertical tubes  

Science.gov (United States)

Forced and mixed convection heat and mass transfer are studied numerically for water containing metallic corrosion products in a heated or cooled vertical tube with variable thermophysical properties at super-critical pressures. The fouling mechanisms and fouling models are presented. The influence of variable properties at super-critical pressures on forced or mixed convection has been analyzed. The differences between heat and mass transfer under heating and cooling conditions are discussed. It is found that variable properties, especially buoyancy, greatly influence the fluid flow and heat mass transfer.

Jiang, Pei-Xue; Ren, Ze-Pei; Wang, Bu-Xuan

1995-01-01

237

Liquid gallium in confined droplets under high-temperature and high-pressure conditions  

International Nuclear Information System (INIS)

Phase transitions and the local structure of micrometric droplets of liquid gallium under pressure were studied by combining extended x-ray absorption fine structure, single-energy x-ray absorption detection (SEXAD), and energy-scanning x-ray diffraction (ESXD). Measurements were performed in a range of pressures and temperatures of 0-6.7 GPa and 298-440 K, respectively. The samples for the high-pressure measurements were obtained by using an emulsion of gallium into epoxy resin, a procedure previously developed by the authors. The distribution of droplets was fully characterized by scanning electron microscopy. We found that the liquid can be kept in a metastable state well beyond the liquid-solid coexistence line (1.9 GPa at 300 K). Considering both the ESXD patterns and the SEXAD scans, we infer that the quantity of crystallized gallium droplets increases as a function of pressure, while no sign of crystallization is observed up to 2.7 GPa. The structural and crystallization properties of Ga emulsions, including the determination of the short-range radial distribution function, were measured by XAS in an extended range of pressures and temperatures, putting to a test the possible existence of different Ga-liquid polymorphs

238

Synthesis of novel Ru2C under high pressure-high temperature conditions  

International Nuclear Information System (INIS)

We report here, for the first time, synthesis of the Fe2N type hexagonal phase of ruthenium carbide by a high pressure-high temperature technique using a laser heated diamond anvil cell (LHDAC). The synthesis is carried out by laser heating a mixture of pure elements, Ru and C, at very low ‘pressure’ of 5 GPa and T ? 2000 K. The structure of the temperature quenched high pressure phase is characterized by in situ high pressure x-ray diffraction (HPXRD) and is corroborated by ex situ TEM imaging and diffraction, carried out for the first time on the retrieved sample synthesized by LHDAC. The lattice parameters of Ru2C at ambient pressure are found to be a = 2.534 ? and c = 4.147 ?. In situ HPXRD studies up to 14.2 GPa yield a bulk modulus of 178(4) GPa. Electronic structure calculations reveal the system to be metallic in nature with a degree of covalence along the Ru-C bond. As ruthenium is isoelectronic to osmium, this result for Ru2C has significant implications in the synthesis and study of osmium carbides.

239

Osmosis-induced water uptake by Eurobitum bituminized radioactive waste and pressure development in constant volume conditions  

Energy Technology Data Exchange (ETDEWEB)

Highlights: Black-Right-Pointing-Pointer The water uptake by Eurobitum is studied to judge the safety of geological disposal. Black-Right-Pointing-Pointer High pressures of up to 20 MPa are measured in constant volume water uptake tests. Black-Right-Pointing-Pointer The morphology of leached Eurobitum samples is studied with {mu}CT and ESEM. Black-Right-Pointing-Pointer The observations are reproduced by an existing CHM formulation for Eurobitum. - Abstract: The chemo-hydro-mechanical (CHM) interaction between swelling Eurobitum radioactive bituminized waste (BW) and Boom Clay is investigated to assess the feasibility of geological disposal for the long-term management of this waste. These so-called compatibility studies include laboratory water uptake tests at Belgian Nuclear Research Center SCK-CEN, and the development of a coupled CHM formulation for Eurobitum by the International Center for Numerical Methods and Engineering (CIMNE, Polytechnical University of Cataluna, Spain). In the water uptake tests, the osmosis-induced swelling, pressure increase and NaNO{sub 3} leaching of small cylindrical BW samples (diameter 38 mm, height 10 mm) is studied under constant total stress conditions and nearly constant volume conditions; the actual geological disposal conditions should be intermediate between these extremes. Two nearly constant volume tests were stopped after 1036 and 1555 days to characterize the morphology of the hydrated BW samples and to visualize the hydrated part with microfocus X-ray Computer Tomography ({mu}CT) and Environmental Scanning Electron Microscopy (ESEM). In parallel, a coupled CHM formulation is developed that describes chemically and hydraulically coupled flow processes in porous materials with salt crystals, and that incorporates a porosity dependent membrane efficiency, permeability and diffusivity. When Eurobitum BW is hydrated in (nearly) constant volume conditions, the osmosis-induced water uptake results in an increasing pressure to values that can be (in theory) as high as 42.8 MPa, being the osmotic pressure of a saturated NaNO{sub 3} solution. After about four years of hydration in nearly constant volume water uptake tests, pressures up to 20 MPa are measured. During this hydration period only the outer layers with a thickness of 1-2 mm were hydrated (as derived from {mu}CT and ESEM analyses), and only about 10-20% of the initial NaNO{sub 3} content was released by the samples. In the studied test conditions, the rates of water uptake and NaNO{sub 3} leaching are low because of the low porosity, and thus low permeability, of the hydrated BW samples in combination with a highly efficient semi-permeable bitumen membrane. In contrast to the hydration in free swelling conditions, the increase in porosity is limited by the high pressures in the nearly constant volume tests. Furthermore, at the interface with the stainless steel filters, a low permeable re-compressed bitumen layer is formed, as observed on the ESEM images. The experimental results of pressure increase and NaNO{sub 3} leaching, as well as observations on {mu}CT and ESEM images (e.g. compression of leached layers, high dissolved NaNO{sub 3} concentration in hydrated BW after about four years), were reproduced rather successfully by the coupled CHM formulation for Eurobitum BW. A long-term model prediction of the evolution of the osmosis-induced pressure in the nearly constant volume tests shows that the pressure would reach a maximal value of about 20 MPa after about 5.5 years, after which the pressure would start to decrease. After 10,000 days ({approx}27 years) the pressure would have decreased to a value of {approx}2 MPa.

Marieen, A., E-mail: amarien@sckcen.be [Waste and Disposal Expert Group, Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, 2400 Mol (Belgium); Mokni, N., E-mail: Nadia.mokni@upc.edu [Department of Geotechnical Engineering and Geosciences, Universidad Politecnica de Catalunya (UPC), Calle Gran Capitan, s/n, Edificio C-1, 08034 Barcelona (Spain); Valcke, E. [Waste and Disposal Expert Group, Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, 2400 Mol (Belgium); Olivella, S. [Department of Geotechnical Engineering and Geosciences, Universidad Politecnica de Catalunya (UPC), Calle Gran Capitan, s/n, Edificio C-1, 08034 Barcelona (Spain); Smets, S. [Waste and Disposal Expert Group, Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, 2400 Mol (Belgium); Li, X., E-mail: xli@sckcen.be [EIG EURIDICE, Boeretang 200, 2400 Mol (Belgium)

2013-01-15

240

Scaling of conditional Lagrangian time correlation functions of velocity and pressure gradient magnitudes in isotropic turbulence  

CERN Document Server

We study Lagrangian statistics of the magnitudes of velocity and pressure gradients in isotropic turbulence by quantifying their correlation functions and their characteristic time scales. It has been found that the Lagrangian time-correlations of the velocity and pressure gradient tensor and vector elements scale with the locally-defined Kolmogorov time scale, defined from the box-averaged dissipation-rate and viscosity. In this work, we study the Lagrangian time-correlations of the absolute values of velocity and pressure gradients. We explore the appropriate temporal scales with the aim to achieve collapse of the correlation functions. The data used in this study are sampled from the web-services accessible public turbulence database(http://turbulence.pha.jhu.edu). The database archives a pseudo-spectral direct numerical simulation of forced isotropic turbulence with Taylor-scale Reynolds number 433, and supports spatial differentiation and spatial/temporal interpolation inside the database. The analysis s...

Yu, Huidan

2009-01-01

 
 
 
 
241

Advanced setup for high-pressure and low-temperature neutron diffraction at hydrostatic conditions  

International Nuclear Information System (INIS)

We describe a design of the experimental setup for neutron diffraction studies at low temperatures and hydrostatic pressure. The significant benefit of the setup, compared to the previous methods, is that it makes possible the simultaneous collection of neutrons diffracted at the 30 deg. -150 deg. range with no contamination by the primary scattering from the sample surroundings and without cutting out the incident and diffracted beams. The suggested design is most useful for third-generation time-of-flight diffractometers and constant wavelength instruments. Application of the setup expands the capabilities of high-pressure neutron diffraction, allowing time-resolved kinetics and structural studies, multihistogram Rietveld, and pair distribution function and texture analyses. The high efficiency of the setup was proven for the HIPPO diffractometer at Los Alamos Neutron Science Center under pressures up to 10 kbar and temperatures from 4 to 300 K

242

Barometric effect in EAS with energies 1017-1019 eV  

International Nuclear Information System (INIS)

Seasonal variations in extensive air showers (EAS) detected at the Yakut EAS array are analyzed. The atmospheric pressure dependence of the variations is essentially pronounced. As the pressure increases by 1 mm of mercury, the EAS intensity decreases by 2%. No air temperature dependence is revealed

243

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 condition. (author)

244

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)

245

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

246

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.

247

Influence of the synthesis conditions of silicon nanodots in an industrial low pressure chemical vapor deposition reactor  

Energy Technology Data Exchange (ETDEWEB)

Experiments conducted in an industrial tubular low pressure chemical vapor deposition (LPCVD) reactor have demonstrated the reproducibility and spatial uniformity of silicon nanodots (NDs) area density and mean radius. The wafer to wafer uniformity was satisfactory (density and radius standard deviations <10%) for the whole conditions tested except for low silane flow rates, high silane partial pressures and short run durations (<20 s). Original synthesis conditions have then been searched to reach both excellent wafer to wafer uniformities along the industrial load of wafers and high NDs densities. From previous results, it was deduced that the key was to markedly increase run duration in decreasing temperature and in increasing silane pressure. At 773 K, run durations as long as 180 and 240 s have thus allowed to reach NDs densities respectively equal to 9 x 10{sup 11} and 6.5 x 10{sup 11} NDs/cm{sup 2} for the two highest silane pressures tested in the range 60-150 Pa.

Cocheteau, V. [LGC/ENSIACET/INPT, UMR CNRS 5503, 5 rue Paulin Talabot, BP1301, 31106 Toulouse Cedex 1 (France); CEA, LETI - MINATEC, 17 Avenue des Martyrs, 38054 Grenoble Cedex 09 (France); Scheid, E. [LAAS, UPR CNRS 8011, Avenue du Colonel Roche, 31077 Toulouse Cedex (France); Mur, P.; Billon, T. [CEA, LETI - MINATEC, 17 Avenue des Martyrs, 38054 Grenoble Cedex 09 (France); Caussat, B. [LGC/ENSIACET/INPT, UMR CNRS 5503, 5 rue Paulin Talabot, BP1301, 31106 Toulouse Cedex 1 (France)], E-mail: Brigitte.Caussat@ensiacet.fr

2008-03-15

248

A Computational Fluid Dynamics Study of Transitional Flows in Low-Pressure Turbines under a Wide Range of Operating Conditions  

Science.gov (United States)

A transport equation for the intermittency factor is employed to predict the transitional flows in low-pressure turbines. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, mu(sub p) with the intermittency factor, gamma. Turbulent quantities are predicted using Menter's two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model which can produce both the experimentally observed streamwise variation of intermittency and a realistic profile in the cross stream direction. The model had been previously validated against low-pressure turbine experiments with success. In this paper, the model is applied to predictions of three sets of recent low-pressure turbine experiments on the Pack B blade to further validate its predicting capabilities under various flow conditions. Comparisons of computational results with experimental data are provided. Overall, good agreement between the experimental data and computational results is obtained. The new model has been shown to have the capability of accurately predicting transitional flows under a wide range of low-pressure turbine conditions.

Suzen, Y. B.; Huang, P. G.; Ashpis, D. E.; Volino, R. J.; Corke, T. C.; Thomas, F. O.; Huang, J.; Lake, J. P.; King, P. I.

2007-01-01

249

Crack growth behaviour of low-alloy steels for pressure boundary components under transient light water reactor operating conditions - CASTOC, Part I: BWR/NWC conditions  

International Nuclear Information System (INIS)

One of the ageing phenomena of pressure boundary components of light water reactors (LWR) is environmentally-assisted cracking (EAC). The project CASTOC (5. Framework Programme of the EU) was launched September 2000 with six European partners and terminated August 2003. It was focused in particular on the EAC behaviour of low-alloy steels (LAS) and to some extent to weld metal, heat affected zone and the influence of an austenitic cladding. The main objective was directed to the clarification of EAC crack growth behaviour/mechanism of LAS in high-temperature water under steady-state power operation (constant load) and transient operating conditions (e.g., start-up/shut-down, transients in water chemistry and load). Autoclave tests were performed with Western and Russian type reactor pressure vessel steels under simulated boiling water reactor (BWR)/normal water chemistry (NWC) and pressurised water reactor (VVER) conditions. The investigations were performed with fracture mechanics specimens of different sizes and geometries. The applied loading comprised cyclic loads, static loads and load spectra where the static load was periodically interrupted by partial unloading. With regard to water chemistry, the oxygen content (VVER) and impurities of sulphate and chlorides (BWR) were varied beyond allowable limits for continuous operation. The current paper summarises the most important crack growth results obtained under simulated BWR/NWC conditions. The results are discussed in the context of the current crack growth rate curves in the corresponding nuclear codes. (authors)

250

Crack growth behaviour of low-alloy steels for pressure boundary components under transient light water reactor operating conditions - CASTOC, Part I: BWR/NWC conditions  

Energy Technology Data Exchange (ETDEWEB)

One of the ageing phenomena of pressure boundary components of light water reactors (LWR) is environmentally-assisted cracking (EAC). The project CASTOC (5. Framework Programme of the EU) was launched September 2000 with six European partners and terminated August 2003. It was focused in particular on the EAC behaviour of low-alloy steels (LAS) and to some extent to weld metal, heat affected zone and the influence of an austenitic cladding. The main objective was directed to the clarification of EAC crack growth behaviour/mechanism of LAS in high-temperature water under steady-state power operation (constant load) and transient operating conditions (e.g., start-up/shut-down, transients in water chemistry and load). Autoclave tests were performed with Western and Russian type reactor pressure vessel steels under simulated boiling water reactor (BWR)/normal water chemistry (NWC) and pressurised water reactor (VVER) conditions. The investigations were performed with fracture mechanics specimens of different sizes and geometries. The applied loading comprised cyclic loads, static loads and load spectra where the static load was periodically interrupted by partial unloading. With regard to water chemistry, the oxygen content (VVER) and impurities of sulphate and chlorides (BWR) were varied beyond allowable limits for continuous operation. The current paper summarises the most important crack growth results obtained under simulated BWR/NWC conditions. The results are discussed in the context of the current crack growth rate curves in the corresponding nuclear codes. (authors)

Ritter, S.; Seifert, H.P. [Paul Scherrer Institute, PSI, Villigen (Switzerland); Devrient, B.; Roth, A. [Framatome ANP GmbH, Erlangen (Germany); Ehrnsten, U. [VTT Industrial Systems, Espoo (Finland); Ernestova, M.; Zamboch, M. [Nuclear Research Institute, NRI, Rez (Czech Republic); Foehl, J.; Weissenberg, T. [Staatliche Materialpruefungsanstalt, MPA, Stuttgart (Germany); Gomez-Briceno, D.; Lapena, J. [Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, CIEMAT, Madrid (Spain)

2004-07-01

251

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)

252

Stressed-and-strained state for short cylinder under unsteady heating conditions, irradiation and uniform external pressure  

International Nuclear Information System (INIS)

The stressed-and-strained state problem for a short continuous cylinder under unsteady heating conditions, irradiation and uniform external pressure has been solved numerically in axially symmetric formulation of the problem. The solution algorithm has been computerized on the electronic computer BEhSm - 6 as a mathematical programm on the FORTRAN language. Calculation of a short continuous cylinder is given as an example

253

Crack growth behaviour of low-alloy steels for pressure boundary components under transient light water reactor operating conditions - CASTOC, Part II: WWER conditions  

International Nuclear Information System (INIS)

One of the ageing phenomena of pressure boundary components of light water reactors (LWRs) is environmentally-assisted cracking (EAC). The project CASTOC (5. Framework Programme of the EU) was launched September 2000 with six European partners and terminated August 2003. It focused in particular on the EAC behaviour of low-alloy steels (LAS) and to some extent to weld metal, heat affected zone and the influence of an austenitic cladding. The main objective was directed to the clarification of crack growth behavior of LAS in high-temperature water due to EAC under constant load (steady-state power operation), to study the effect of transient conditions (during operation or start-up/shut-down of a plant) using their impact on time-based and cycle-based crack growth rates and to a more detailed understanding of the acting mechanisms. Autoclave tests were performed with Western and Russian type reactor pressure vessel steels under simulated boiling water reactor (BWR)/normal water chemistry (NWC) and pressurized water reactor (WWER) conditions. The investigations were performed with fracture mechanics specimens of different sizes and geometries. The applied loading comprised cyclic loads, static loads and load spectra where the static load was periodically interrupted by partial unloading. With regard to water chemistry, the oxygen content (WWER) and impurities of sulphate and chlorides (BWR) were varied beyond allowable limits for continuous operation. The current paper summarizes the most important crack growth results obtained under simulated WWER conditions. The influence of oxygen content and the effect of specimen size (C(T)25 versus C(T)50 specimens) on the crack growth rates are shown. The results are discussed in the context of the current crack growth rate curves in the corresponding nuclear codes. (authors)

254

Crack growth behaviour of low-alloy steels for pressure boundary components under transient light water reactor operating conditions - CASTOC, Part II: WWER conditions  

Energy Technology Data Exchange (ETDEWEB)

One of the ageing phenomena of pressure boundary components of light water reactors (LWRs) is environmentally-assisted cracking (EAC). The project CASTOC (5. Framework Programme of the EU) was launched September 2000 with six European partners and terminated August 2003. It focused in particular on the EAC behaviour of low-alloy steels (LAS) and to some extent to weld metal, heat affected zone and the influence of an austenitic cladding. The main objective was directed to the clarification of crack growth behavior of LAS in high-temperature water due to EAC under constant load (steady-state power operation), to study the effect of transient conditions (during operation or start-up/shut-down of a plant) using their impact on time-based and cycle-based crack growth rates and to a more detailed understanding of the acting mechanisms. Autoclave tests were performed with Western and Russian type reactor pressure vessel steels under simulated boiling water reactor (BWR)/normal water chemistry (NWC) and pressurized water reactor (WWER) conditions. The investigations were performed with fracture mechanics specimens of different sizes and geometries. The applied loading comprised cyclic loads, static loads and load spectra where the static load was periodically interrupted by partial unloading. With regard to water chemistry, the oxygen content (WWER) and impurities of sulphate and chlorides (BWR) were varied beyond allowable limits for continuous operation. The current paper summarizes the most important crack growth results obtained under simulated WWER conditions. The influence of oxygen content and the effect of specimen size (C(T)25 versus C(T)50 specimens) on the crack growth rates are shown. The results are discussed in the context of the current crack growth rate curves in the corresponding nuclear codes. (authors)

Ernestova, M.; Zamboch, M. [Nuclear Research Institute, NRI, Rez (Czech Republic); Devrient, B.; Roth, A. [Framatome ANP GmbH, Erlangen (Germany); Ehrnsten, U. [VTT Industrial Systems, Espoo (Finland); Foehl, J.; Weissenberg, T. [Staatliche Materialpruefungsanstalt, MPA, Stuttgart (Germany); Gomez-Briceno, D.; Lapena, J. [Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, CIEMAT, Madrid (Spain); Ritter, S.; Seifert, H.P. [Paul Scherrer Institute, PSI, Villigen (Switzerland)

2004-07-01

255

Seasonal variation in the incidence of preeclampsia and eclampsia in tropical climatic conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Observational studies have demonstrated various correlations between hypertensive disorders of pregnancy and different weather parameters. We aim to study if a correlation exists between the incidence of eclampsia and pre-eclampsia and various weather parameters in the tropical coastal city of Mumbai which has the distinction of having relatively uniform meteorological variables all throughout the year, except for the monsoon season. Methods We retrospectively analysed data from a large maternity centre in Mumbai, India over a period of 36 months from March 1993 to February 1996, recording the incidence of preeclampsia and eclampsia. Meteorological data was acquired from the regional meteorological centre recording the monthly average temperature, humidity, barometric pressure and rainfall during the study period. Study period was then divided into two climate conditions: monsoon season (June to August and dry season September to May. The incidence of preeclampsia and eclampsia and the meteorological differences between the two seasons were compared. Results Over a 36-month period, a total of 29562 deliveries were recorded, of which 1238 patients developed preeclampsia (4.18% and 34 developed eclampsia (0.11%. The incidence of preeclampsia did not differ between the monsoon and the dry season (4.3% vs. 4.15%, p = 0.5. The incidence of eclampsia was significantly higher in the monsoon (0.2% vs. 0.08%, p = 0.01. The monsoon was significantly cooler (median maximum temperature 30.7°C vs. 32.3°C, p = 0.01, more humid (median relative humidity 85% vs. 70%, p = 0.0008, and received higher rainfall (median 504.9 mm vs. 0.3 mm, p = 0.0002 than the rest of the year. The median barometric pressure (1005 mb during the monsoon season was significantly lower than the rest of the year (1012 mb, p Conclusion In the tropical climate of Mumbai, the incidence of eclampsia is significantly higher in monsoon, when the weather is cooler and humid with a lower barometric pressure than the rest of the year. This effect is not seen with preeclampsia. This strengthens the association of low temperature and high humidity with triggering of eclampsia.

Subramaniam Vidya

2007-10-01

256

High temperature postirradiation materials performance of spent pressurized water reactor fuel rods under dry storage conditions  

International Nuclear Information System (INIS)

Postirradiation studies on failure mechanisms of well-characterized pressurized water reactor rods were conducted for up to a year at 482, 510, and 5710C in limited air and inert gas atmospheres. No cladding breaches occurred even though the tests operated many orders of magnitude longer in time than the lifetime predicted by Blackburn's analyses. The extended lifetime is due to significant creep strain of the Zircaloy cladding, which decreases the internal rod pressure. The cladding creep also contributes to radial cracks, through the external oxide and internal fuel-cladding chemical interaction layers, which propagated into and arrested in an oxygen stabilized alpha-Zircaloy layer. There were no signs of either additional cladding hydriding, stress corrosion cracking, or fuel pellet degradation. If irradiation hardening does not reduce the stress rupture properties of Zircaloy, a conservative maximum storage temperature of 4000C based on a stress-rupture mechanism is recommended to ensure a 1000-yr cladding lifetime

257

Border control! Capillary pressure / saturation relationships in a diphasic flow in a random medium: Influence of the boundary conditions  

Science.gov (United States)

Solving problems involving biphasic flows in porous media, at a scale larger than the pore one, normally requires the use of relationships between pressure and saturation. These allow the closure of generalized Darcy flow models for two phases, commonly used in hydrology or large scale problems of diphasic flow in porous media. There are mathematical models which approximate experimental records with curve-fitting equations. The two most common models are the Brooks-Corey and van Genüchten ones, they are used to complete a system of generalized Darcy equations. The purpose of the current study is the influence of the boundary conditions on the relationship between pressure and saturation. We perform numerical simulations of drainage experiments. Water is the wetting fluid and air is the non wetting fluid. The results highlight the fact that a filter which allows only water to flow at the exit face of the system modifies both the shape of the curve and the value of the residual saturation. The pressure of the models that are commonly used does not match with the pressure of real flows since there is no filter to cross, to flow from an elementary volume to another. Experiments performed in transparent Hele-Shaw cells exhibit the same features, showing the influence of the semi permeable boundary conditions on the pressure-saturation measures obtained. This effect corresponding to the formation of localized plugging clusters at the boundaries, is obtained in slow flow conditions, and is independent of any dynamic fingering, also known to affect such relations (1,2,3). Modeling flows in open media thus would require to use the central part of the curves pressure saturation where the effect of the boundaries is the least important, or to modify properly these relationships to extract the behavior unaffected by boundaries. References: (1) Two-phase flow: structure, upscaling, and consequences for macroscopic transport properties Renaud Toussaint ; Knut Jørgen Måløy; Yves Méheust; Grunde Løvoll; Mihailo Jankov; Gerhard Schäfer; Jean Schmittbuhl Vadose Zone Journal, 2012, 11 (3), pp. vzj2011.0123 (2) Løvoll, G., M. Jankov, K.J. Måløy, R. Toussaint, J. Schmittbuhl, G. Schaefer and Y. Méheust, Influence of viscous fingering on dynamic saturation-pressure curves in porous media, Transport in Porous Media, 86, 1, 305-324, 2010 (3) Toussaint, R., G. Løvoll, Y. Méheust, K.J. Måløy and J. Schmittbuhl, Influence of pore-scale disorder on viscous fingering during drainage, Europhys. Lett., 71, 583 (2005).

Fiorentino, Eve-Agnès; Toussaint, Renaud; Moura, Marcel; Jankov, Mihailo; Schäfer, Gerhard; Jørgen Måløy, Knut

2013-04-01

258

Temperature conditions control in welding and heat treatment of pressure vessel parts  

International Nuclear Information System (INIS)

The appropriate method is described and the results are listed of measuring temperature fields in welding, pre-heating, local annealing and heat treatment of the Kh2MFA type steels used for the manufacture of reactor pressure vessels. The collection and evaluations of the measured data from up to 256 measuring points were done using the Adimes Czechoslovak-made measuring system. (J.B.)

259

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 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

260

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

 
 
 
 
261

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

The plasma parameters such as electron distribution function and electron density of three atmospheric-pressure transient discharges namely filamentary and homogeneous dielectric barrier discharges in air, and the spark discharge of argon plasma coagulation (APC) system are determined. A combination of numerical simulation as well as diagnostic methods including current measurement and optical emission spectroscopy (OES) based on nitrogen emissions is used. The applied metho...

Keller, Sandra; Rajasekaran, Priyadarshini; Bibinov, Nikita; Awakowicz, Peter

2011-01-01

262

Surface tension measurements of coal ash slags under reducing conditions at elevated pressures  

Energy Technology Data Exchange (ETDEWEB)

The aim of limiting the amount of CO{sub 2} that is released together with other exhaust gases from power plants can be reached by technologies allowing for a systematic separation of this greenhouse gas. One such technology is the integrated gasification combined cycle power plant which makes use of a coal gasification step. For the gasification involving temperatures far higher than in typical pulverised combustion chambers, ash contained in the fuel is liquefied (slag) and must be removed from the cycle to guarantee safe operation of downstream equipment. To keep the efficiency of the power plant as high as possible, hot gas cleaning facilities are most desirable for this purpose. The design of these installations necessitates knowledge about thermophysical properties of coal ash slags, especially in reducing, pressurised atmospheres. In this work, the surface tension of 15 coal ash slags was measured in argon hydrogen gas of up to 10 bar absolute pressure according to the sessile drop method. Compared to experiments at 1 bar, surface tension values up to 42% lower were found on applying pressure. Additionally, shifts in the melting temperature interval of the ashes due to increased pressure were observed. The surface tension values obtained in pressurised atmospheres ranged from 270 to 490 mN/m with respect to temperature intervals where almost no data scattering occured. 43 refs., 11 figs., 1 tab.

Tobias Melchior; Marc Blaesing; Guenther Puetz; Michael Mueller [Forschungszentrum Juelich GmbH, Juelich (Germany). Institute of Energy Research

2011-01-15

263

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

264

Shear Veins Under High Pore Pressure Condition Along Subduction Interface: Yokonami Mélange, Cretaceous Shimanto Belt, Shikoku, Southwest Japan  

Science.gov (United States)

Fluid pressure along subdcution interface is a key parameter to understand the fault strength, wedge geometry and seismogenic behavior. In this study, we focused on shear veins pervasively observed in exhumed accretionary complex, Yokonami mélange, Cretaceous Shiamanto Belt, Southwest Japan to examine paleo-stress, effective friction coefficient, fluid pressure ratio and fluid pressure along subduction interface. Lithology of the Yokonami mélange is mainly sandstones surrounded by foliated black shales with minor components of basalts, cherts, tuffs, and limestones, representing tectonic mélange textures. Shear veins cutting mélange foliations are pervasively observed. Shear veins are composed of quartz and calcite. Slicken lines and slicken steps are always observed on the surfaces of shear veins. Pressure-temperature conditions for shear veins are about 180MPa and about 200 degree C on the basis of fluid inclusion analysis. Since the distribution of shear veins are related to packages of ocean floor stratigraphy, formation of shear vein can be before underplating and after mélange formation along subduction interface. We conducted multiple inversion method using slip data of shear veins to examine paleo-stress. In the result, we obtained maximum shear stress horizontal to foliations with 0.3 of stress ratio that is defined as (sigma2-sigma3)/(sigma1-sigma3). Effective friction coefficient was estimated as about 0.10-0.22 by the lowest value of ratio of normal and shear stresses in the normalized Mohr's circle on each plane of shear vein. If we put friction coefficient under dry condition as 0.7 because shear veins cut lithified mélange through out, fluid pressure ratio is equivalent to 0.68-0.86. This is very high fluid pressure ratio along subduction plate interface. On the basis of this fluid pressure ratio and P-T conditions of shear veins from fluid inclusion analysis, 7-12km of depth and 20-30 degree C of geothermal gradient were estimated. The age of subducting plate in the Yokonami mélange was about 50-60Ma from the difference of depositional ages between chert and black shale. The geothermal gradient estimated from the slab age is consistent with from fluid pressure ratio and fluid inclusion analysis. This suggests that the low effective frictional coefficient and high fluid pressure ratio estimated from geological evidences are reasonable values for the formation of shear veins. Kitajima and Saffer (2012) revealed that very low frequency earthquakes (VLFs) occur in the high pore pressure area. Saito et al. (2013) found the quartz cemented fault rocks represent velocity weakening behavior and suggested that the quartz-rich shear veins in shallow accretionary complex might be a geological evidence of VLFs. Our result in this study can support this idea as a shear veins with high fluid pressure at the time of their formation.

Hashimoto, Y.; Eida, M.

2013-12-01

265

Sequential capture of CO2 and SO2 in a pressurized TGA simulating FBC conditions.  

Science.gov (United States)

Four FBC-based processes were investigated as possible means of sequentially capturing SO2 and CO2. Sorbent performance is the key to their technical feasibility. Two sorbents (a limestone and a dolomite) were tested in a pressurized thermogravimetric analyzer (PTGA). The sorbent behaviors were explained based on complex interaction between carbonation, sulfation, and direct sulfation. The best option involved using limestone or dolomite as a SO2-sorbent in a FBC combustor following cyclic CO2 capture. Highly sintered limestone is a good sorbent for SO2 because of the generation of macropores during calcination/carbonation cycling. PMID:17533862

Sun, Ping; Grace, John R; Lim, C Jim; Anthony, Edward J

2007-04-15

266

A new transducer for roll gap measurements of the roll pressure distribution and the friction condition in cold flat rolling  

DEFF Research Database (Denmark)

Background/purpose The only way to establish the true rolling pressure and the true friction condition in cold rolling is to conduct measurements in the roll bite. A new transducer design is therefore proposed, this to overcome problems in previous measurements in the past 70 years. Method The new idea is to increase the contact surface of the transducer, to be larger than the arc of contact. This is in the opposite way, compared to the smaller and smaller contact pin design that has been prevailing. Results The measurements where conducted during cold dry rolling of both copper strips and stainless steel strips in a pilot mill. The recordings were selected from a steady state with no disturbance from the material flow. The transducer was able to simultaneously measure both the normal pressure and the friction stress. An estimation of the coefficient of friction was accordingly performed. Conclusions The new transducer works very well, it was seen to be robust and able to avoid signal disturbance. The pressure and friction stress distribution results was as expected by the authors and a good reproducibility, together with a proven agreement between recorded signals and signals simulated. Keywords Friction stress, normal pressure distribution, roll bite measurements, cold flat rolling of metals

Wanheim, Tarras; Henningsen, Poul

2005-01-01

267

The central axis prosthetic cardiac valve: an in vitro study of pressure drop assessment under steady-state flow conditions.  

Science.gov (United States)

In this work, a new mechanical prosthetic heart valve, the central axis valve, is presented. This new prosthesis has been tested in vitro, and compared with four other common prosthetic cardiac valves (Starr-Edwards 6120, Bjork-Shiley monostrut, Medtronic-Hall, and St Jude Medical valves). All valves studied have the same orifice diameter of 22 mm. The prostheses were installed inside a transparent mitral test chamber, which enables pressure drop measurement to be made under steady-state flow conditions using a blood analogue fluid. Pressure drop loss is one important factor affecting the overall performance of a prosthetic heart valve. Steady-state flow tests are essential to predict certain flow characteristics and pressure gradient loss before more complicated, expensive, and difficult-to-interpret pulsatile flow tests are conducted. All experiments were performed in vitro and at steady volumetric flow rates of 10 to 30 l/min. The Starr-Edwards SE 6120 showed the highest values for pressure drop. The St Jude Medical valve offers the minimum resistance to flow. The central axis valve comes second to the Starr Edwards valve for this type of measurement. The new valve is promising. A complete valve evaluation programme, covering initial conceptional design through to clinical use, is in progress. Materials for the fabrication of the new valve are also under consideration. PMID:2296172

Haggag, Y A

1990-01-01

268

Sodium-heated evaporator critical heat flux experiments at subcritical pressure conditions for commercial LMFBR plant application  

International Nuclear Information System (INIS)

An experimental program was performed to investigate critical heat flux at subcritical pressure conditions in a single duplex tube sodium heated steam generator mode. The experimental ranges were: pressure: 8.274 to 12.41 MPa (1200 to 1800 psia); mass flux: 2.01*10$sup 6$ to 7.82*10$sup 6$ kg/hr-m$sup 2$ (0.43 to 1.65*10$sup 6$ lb/hr-ft$sup 2$); and heat flux: 0.48 to 0.85 MW/m$sup 2$(0.152 to 0.27*10$sup 6$ Btu/hr-ft$sup 2$). The present test data was correlated and compared with that of other investigations in terms of critical steam quality, heat flux, tube diameter, pressure, and water/steam mass flux. The resulting correlation agrees well with other sodium-heated and electrically heated test results in the range of pressure: 6.9 to 15.4 MPa (1000 to 2670 psia) and mass flux: 2.01*10$sup 6$ to 7.82*10$sup 6$ kg/hr-m$sup 2$ (0.43 to 1.65*10$sup 6$ lb/hr-ft$sup 2$). 17 refs

269

Post-dryout heat transfer and entrained droplet sizes at low pressure and low flow conditions  

International Nuclear Information System (INIS)

The entrainment mechanisms and the entrained droplet sizes with relation to the flow regimes are investigated. Through the analysis of many experimental post-dryout data, it is shown that the most probable flow regime near dryout or quench front is not annular flow but churn-turbulent flow when the mass flux is low. A correlation describing the initial droplet size just after the CHF position at low mass flux is suggested through regression analysis. The history-dependent post-dryout model of Varone and Rohsenow replaced by the Webb-Chen model for wall-vapor heat transfer is used as a reference model in the analysis. In the post-dryout region at low pressure and low flow, it is found that the suggested one-dimensional mechanistic model is not applicable when the vapor superficial velocity is very low. This is explained by the change of main entrainment mechanism with the change of flow regime. In bubbly or slug flow a number of tiny droplets generated from bubble burst become important in the heat transfer after dryout. Therefore, the suggested correlation is valid only in the churn-turbulent flow regime (jg* = 0.5?4.5). It is also suggested that the droplet size generated from the churn-turbulent surface is dependent not only on the pressure but also on the vapor velocity. It turns out that the present model can predict the measured cladding and vapor temperatures within 20% and 25%, respectively

270

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

271

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

272

Barometric sensitive coatings based upon osmium complexes dissolved in a fluoroacrylic polymer.  

Science.gov (United States)

Pressure sensitive paints (PSP) that measure the changes in air pressure have proved to be useful in the design of aircraft and other vehicles. In this study we incorporate highly luminescent divalent osmium complexes into PSP. The divalent osmium complexes were heptafluorobutyrate salts of [Os(N-N)2(L-L)]2+ or [Os(L-L)2(N-N)]2+, where N-N is a derivative of 1,10-phenanthroline, and L-L is a diphosphine or diarsine ligand. The complexes were dissolved into poly(1,1,1,3,3,3-hexafluoroisopropylmethacrylate-co-1H,1H-dihydroperflurobutylmethacrylate) (FIB) at a concentration of 0.002 g of complex to 1.000 g of polymer. The luminescence of the coatings was tested for pressure sensitivity, temperature dependence, and photodegradation. The paints featured strong pressure response, and the temperature dependence of the luminescence was measured as low as -0.11% degrees C(-1). Several of the complexes exhibited little photodegradation upon prolonged exposure to 400 nm light. These attributes make the complexes very desirable luminescent dyes for PSP. PMID:19117455

Carlson, Brenden; Bullock, John P; Hance, Timothy M; Phelan, Gregory D

2009-01-01

273

Investigation of the air pressure characteristics influencing the variability of radon gas and radon progeny in domestic vernacular buildings.  

Science.gov (United States)

Analysis of time-series data sets collected in vernacular buildings linked with radium source bedrock has identified a number of internal and external pressure characteristics linking meteorological parameters with the variability of radon gas and its progeny. The buildings' cellars built into the bedrock associated with the radium source have relatively high levels of radon concentration. These cellars have essentially stable microclimatic conditions, unlike the ground and upper levels of the buildings. Comparative radon concentration data collected from various comparable buildings suggest the need to distinguish between short and longer-term influences on radon concentrations. Water vapor pressure is inferred to be a principal determinant of the short-term variability of radon gas concentrations. Barometric pressure is suggested as determining the trend or general longer-term level of radon. Both of these pressure components are related to temperature. Wind speed appears to have a dual influence on radon variability: directly, through wind pressure relative to the ground and building structure particularly associated with low-pressure weather regimes; and indirectly, through changes to the water vapor pressure component. PMID:11414625

Marley, F

2001-07-01

274

Numerical study of the pressure drop in a plain fin-and-circular tube heat exchanger under frost condition  

International Nuclear Information System (INIS)

Full text: Three-dimensional computational fluid dynamics (CFD) simulations are carried out to study the pressure drop behavior in a plain fin-and-four staggered layout and circular tube rows for different fin pitches under frost conditions using FLUENT 6.3 CFD code. Models geometry is created and meshed using GAMBIT 2.3. Fluid flow and heat transfer are simulated and results calculated using (Transitional SST k-omega) turbulence model, with steady-state solver. Model validation is carried out by comparing the pressure drop of a simulated case with experimental results from the literature. It was found that Fluent 6.3 software has been sufficient for simulating the flow characteristics in tube-fin heat exchangers. (author)

275

Experimental study on heating conditions of the welded rotor of the NPP turbine low-pressure cylinder at start ups  

International Nuclear Information System (INIS)

As a result of the experimental studies performed at the low pressure cylinder (LPC) of the Kolski NPP K-220-44 turbine the data have been obtained on border (initial and boundary) heating conditions of the welded dise rotor of the LPC. The temperature of the rotor surface at cooling down and steam temperatures in the cylinder at sturt-ups, shutdowns and stationary regimes of a turbine operation were measured. On the basis of the experimental data obtained empirical dependences and computer calculation programs of changing the temperature state of the low pressure cylinder rotor at cooling down and its heating at start-ups which makes possible to evaluate the thermostrained state of the rotor, to develop the recommendations on the start-up regime

276

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

277

Photovoltaic performance of dye-sensitized solar cells stained with black dye under pressurized condition and mechanism for high efficiency  

Energy Technology Data Exchange (ETDEWEB)

A porous TiO{sub 2} layer was stained with black dye (BD) under a pressurized CO{sub 2} atmosphere. Jsc of the cell (20.66 mA/cm{sup 2}) was higher than that prepared by a conventional dipping process (18.96 mA/cm{sup 2}). The higher Jsc was explained by the decrease in surface-state density on the nano-porous TiO{sub 2} layer. In addition, BD aggregation was found to be retarded under the pressurized CO{sub 2} condition, which is also associated with the higher Jsc. These phenomena were explained by the low BD concentration in the CO{sub 2} fluid, the swift reaction rate between TiOH and HOCO dye, and the high diffusion coefficient of BD molecules into porous TiO{sub 2} layers. (author)

Ogomi, Y.; Kashiwa, Y.; Noma, Y.; Fujita, Y.; Kojima, S.; Hayase, S. (Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Wakamatsu-ku, Kitakyushu 808-0196 Japan); Kono, M.; Yamaguchi, Y. [Nippon Steel Chemical Co., Ltd., 46-80, Oaza Nakabaru Sakinohama, Tobata-ku, Kita-Kyushu 804-8503 (Japan)

2009-06-15

278

Evidence for a phase transition in silicate melt at extreme pressure and temperature conditions.  

Science.gov (United States)

Laser-driven shock compression experiments reveal the presence of a phase transition in MgSiO(3) over the pressure-temperature range 300-400 GPa and 10?000-16?000 K, with a positive Clapeyron slope and a volume change of ?6.3 (±2.0) percent. The observations are most readily interpreted as an abrupt liquid-liquid transition in a silicate composition representative of terrestrial planetary mantles, implying potentially significant consequences for the thermal-chemical evolution of extrasolar planetary interiors. In addition, the present results extend the Hugoniot equation of state of MgSiO(3) single crystal and glass to 950 GPa. PMID:22401087

Spaulding, D K; McWilliams, R S; Jeanloz, R; Eggert, J H; Celliers, P M; Hicks, D G; Collins, G W; Smith, R F

2012-02-10

279

Metamorphic pressure-temperature conditions of Indian plate rocks south of the main mantle thrust, lower Swat, Pakistan  

Science.gov (United States)

The Lower Swat rock sequence, in northern Pakistan, is composed of greenschist and amphibolite facies Indian plate rocks that crop out in a dome directly south of the Main Mantle thrust zone and Kohistan arc terrane. The metamorphism is Eocene to Oligocene in age and records the collision of the Indian plate with the Kohistan arc. This paper presents mineral assemblage, mineral composition and garnet zoning data on the Lower Swat rock sequence in order to estimate the pressure-temperature conditions of metamorphism and to infer a possible pressure-temperature-time path. The stratigraphic sequence consists of Precambrian to Cambrian(?) Manglaur formation unconformably overlain by late Paleozoic to early Mesozoic Alpurai group. The Alpurai group is further subdivided into the Marghazar, Kashala, Saidu and Nikanai Ghar formations. The Manglaur formation, in the core of the dome, is at kyanite grade. Metamorphic grade decreases in the overlying Alpurai group where a garnet "isograd" is mapped in calcareous schist of the Kashala formation. Mineral composition geothermometers and geobarometers indicate final metamorphic equilibrium conditions of about 600°-700°C and 9-11 kbar in the Manglaur and Marghazar formations. These conditions are associated with a phase of static recrystallization which postdates the main phases of deformation. Correlation of the structural-tectonic history with the pressure-temperature estimates, and with the garnet zoning analysis, suggests that in the Eocene the Lower Swat rock sequence was subducted to a depth of 35 to 45 km beneath the MMT suture melange. Subduction was followed immediately by exhumation. The initiation of exhumation is believed to have been triggered by a change from subduction to strike slip motion in the MMT, thereby allowing the relatively buoyant Lower Swat crust to rise. The entire metamorphic-deformational cycle lasted from 7 to 16 m.y., ending in the late Eocene about 38 Ma when the rocks cooled through the argon blocking temperature in hornblende (? 550°C).

Dipietro, Joseph A.

1991-08-01

280

In situ X-ray diffraction of natural chromium-bearing spinel under high pressure and high temperature conditions  

International Nuclear Information System (INIS)

Energy dispersive X-ray powder diffraction (EDXD) of natural chromium-bearing spinel collected from Damapin using synchrotron radiation has been in situ measured under high pressure (0-12.82 GPa) and high temperature (300-603 K) conditions. Based on Murnaghan equation, the state equation of natural chromium-bearing spinel was deduced, the bulk modulus KT(0)=369 Gpa and compression coefficient K=2.713x10-3/Gpa were obtained. In addition, the thermal expansion of spinel was discussed, and a thermal expansion coefficient of ?=1.004 x 10-5/K was calculated. (authors)

 
 
 
 
281

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.)

282

ZrNi5-based hydrogenated phases formed under high hydrogen pressure conditions  

International Nuclear Information System (INIS)

Formation of novel hydrides from ZrNi5 alloy has been confirmed experimentally. After exposure of ZrNi5 at 0.9 GPa(H2) and 100 oC for 6 days the alloy transformed into two hydrogenated phases ? and ? containing initially more than 0.38 and 0.86 hydrogen atoms per formula unit respectively. At ambient conditions both hydrides were extremely unstable. Major part of hydrogen desorbed within few minutes. During this desorption the lattice parameters of both hydrides were continuously reduced what confirms their solid solution character.

283

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.)

284

A reactor water level and pressure prediction method under small loss-of-coolant-accident conditions in boiling water reactors  

International Nuclear Information System (INIS)

An on-line method of predicting reactor water level and pressure under small loss-of-coolant-accident (LOCA) conditions has been proposed. The method features initialization of a simplified reactor model in transient conditions. This is done by using plant data in time series and estimating unknown parameters, such as break area, by a nonlinear optimization method. Off-line simulations were performed for small LOCAs (break area: about100 cm2) using the results of a reference LOCA analysis code for plant data. These showed that the difference from the reference calculation during a 10-min period was within 10%, normalized by the value at the initialization time, and the estimation error for break area was below 11%. The overall CPU time required for the prediction was below 10 s in a general purpose computer of 10 million instructions per second

285

Natural organic matter fouling of low-pressure, hollow-fiber membranes: Effects of NOM source and hydrodynamic conditions.  

Science.gov (United States)

Effects of natural organic matter (NOM) source and hydrodynamic conditions on both hydraulically reversible and irreversible fouling of low-pressure, hollow-fiber (LPHF) membranes were systematically investigated using representative sources of natural waters and wastewater effluents. It was found that NOM source plays a primary role in determining the fouling of these membranes. Increase in permeate flux promoted membrane fouling, but to a lesser extent than NOM source. Permeate backwash flux appeared to restore permeability more effectively for the polyether sulfone (PES) membranes than to the polyvinylidene fluoride (PVDF) membranes used. NOM characterization revealed that organic colloids contributed predominantly to the hydraulically reversible fouling, and potentially to the irreversible fouling. Overall, this study demonstrated the importance of NOM source and the presence of organic colloids in the fouling of LPHF membranes, as well as the relevance of hydrodynamic operating conditions on the hydraulic reversibility of the fouling. PMID:17644151

Huang, Haiou; Lee, Nohwa; Young, Thayer; Gary, Amy; Lozier, James C; Jacangelo, Joseph G

2007-09-01

286

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.

Jonsson, Gunnar Eigil

1999-01-01

287

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

288

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)

289

Study and Optimization on graft polymerization under normal pressure and air atmospheric conditions, and its application to metal adsorbent  

International Nuclear Information System (INIS)

Radiation-induced graft polymerization of glycidyl methacrylate (GMA) onto non-woven polyethylene (NWPE) fabric was achieved under normal pressure and air atmospheric conditions, without using unique apparatus such as glass ampoules or vacuum lines. To attain graft polymerization under normal pressure and air atmospheric conditions, the effects of the pre-irradiation dose, pre-irradiation atmosphere, pre-irradiation temperature, de-aeration of GMA-emulsion, grafting atmosphere in a reactor, and dissolved oxygen (DO) concentration in GMA-emulsion on the degree of grafting (Dg) were investigated in detail. It was found that the DO concentration had the strongest influence, the pre-irradiation dose, de-aeration of emulsion and grafting atmosphere had a relatively strong impact, and the pre-irradiation atmosphere and pre-irradiation temperature had the least effect on Dg. The optimum DO concentration before grafting was 2.0 mg/L or less. When a polyethylene bottle was used as a reactor instead of a glass ampoule, graft polymerization under normal pressure and air atmospheric conditions could be achieved under the following conditions; the pre-irradiation dose was more than 50 kGy, the volume ratio of GMA-emulsion to air was 50:1 or less, and the DO concentration in GMA-emulsion during grafting was below 2.0 mg/L. Under these grafting conditions, Dg was controlled within a range of up to 362%. The prepared GMA–grafted NWPE (GMA–g-NWPE) fabric was modified with a phosphWPE) fabric was modified with a phosphoric acid to obtain an adsorbent for heavy metal ions. In the column-mode adsorption tests of Pb(II), the adsorption performance of the produced phosphorylated GMA–g-NWPE fabric (fibrous metal adsorbent) was not essentially dependent on the flow rate of the feed. The breakthrough points of 200, 500, and 1000 h?1 in space velocity were 483, 477 and 462 bed volumes, and the breakthrough capacities of the three flow rates were 1.16, 1.15 and 1.16 mmol-Pb(II)/g-adsorbent.

290

Study and Optimization on graft polymerization under normal pressure and air atmospheric conditions, and its application to metal adsorbent  

Science.gov (United States)

Radiation-induced graft polymerization of glycidyl methacrylate (GMA) onto non-woven polyethylene (NWPE) fabric was achieved under normal pressure and air atmospheric conditions, without using unique apparatus such as glass ampoules or vacuum lines. To attain graft polymerization under normal pressure and air atmospheric conditions, the effects of the pre-irradiation dose, pre-irradiation atmosphere, pre-irradiation temperature, de-aeration of GMA-emulsion, grafting atmosphere in a reactor, and dissolved oxygen (DO) concentration in GMA-emulsion on the degree of grafting (Dg) were investigated in detail. It was found that the DO concentration had the strongest influence, the pre-irradiation dose, de-aeration of emulsion and grafting atmosphere had a relatively strong impact, and the pre-irradiation atmosphere and pre-irradiation temperature had the least effect on Dg. The optimum DO concentration before grafting was 2.0 mg/L or less. When a polyethylene bottle was used as a reactor instead of a glass ampoule, graft polymerization under normal pressure and air atmospheric conditions could be achieved under the following conditions; the pre-irradiation dose was more than 50 kGy, the volume ratio of GMA-emulsion to air was 50:1 or less, and the DO concentration in GMA-emulsion during grafting was below 2.0 mg/L. Under these grafting conditions, Dg was controlled within a range of up to 362%. The prepared GMA-grafted NWPE (GMA-g-NWPE) fabric was modified with a phosphoric acid to obtain an adsorbent for heavy metal ions. In the column-mode adsorption tests of Pb(II), the adsorption performance of the produced phosphorylated GMA-g-NWPE fabric (fibrous metal adsorbent) was not essentially dependent on the flow rate of the feed. The breakthrough points of 200, 500, and 1000 h-1 in space velocity were 483, 477 and 462 bed volumes, and the breakthrough capacities of the three flow rates were 1.16, 1.15 and 1.16 mmol-Pb(II)/g-adsorbent.

Ueki, Yuji; Chandra Dafader, Nirmal; Hoshina, Hiroyuki; Seko, Noriaki; Tamada, Masao

2012-07-01

291

Sorption activity investigation of ultrafine powders of high temperature melting point compounds in atmospheric pressure conditions  

International Nuclear Information System (INIS)

A study is made in saturation with gas in the air for ultradispersed chromium carbonitride and boride powders synthesized in a nitrogen plasma jet according to three variants: from elements, from oxides, from chromium trichloride. It is established that in the air on temperature increasing the powders adsorb considerable amounts of oxygen and water vapor. This results in surface oxidation of powder particles and a loss in specific combination of properties. Preliminary vacuum heat treatment is shown to decrease sharply the rate of atmospheric gas adsorption. The quantity of adsorbed gases is dependent on a carbon monoxide concentration in a particle surface layer and the availability of adsorption centers. The number of such centers in the layer can be controlled by vacuum heat treatment conditions. The interaction of the powders with atmospheric gases is concluded to be of adsorption-diffusion nature

292

Electron micrographical investigations of a corrosion fatigue fracture surface developed under pressure water reactor conditions  

International Nuclear Information System (INIS)

Metallographic and fractographic investigations have been carried out at a 2 T-WOL-specimen of A 508-2 material with which a corrosion fatgue test under PWR-conditions has been performed. There was observed a remarkable accelertion of crack growth rate reducing frequency of fatigue load from 1 Hz to 17 mHz for a limited number of cycles referred to about 3 mm crack growth. In this region of accelerated crack growth the mechanism of tough fatigue crack propagation appears to change mainly to brittle fatigue crack growth along cleavage planes. The reason for the acceleration of crack growth may be causally the hydrogen crack tip embrittlement which is promoted by a longer exposure time for hydrogen under stress. The crack tip embrittlement may also be assisted by 3000C tempering (ageing) effect

293

Reactions of possible cellulose liquefaction intermediates under high pressure liquefaction conditions  

Energy Technology Data Exchange (ETDEWEB)

Glucose, methyl and phenyl glucosides, glucitol, levoglucosenone and hydroxymethylfurfural were allowed to react under conditions where cellulose liquefies, with ZnCl/sub 2/, NaH/sub 2/PO/sub 4/ and NaOAc/H/sub 3/BO/sub 3/ as catalysts, to determine whether these compounds could be intermediates in cellulose liquefaction. It was found that: free aldehyde groups and acidity promote charring; these compounds do not fully interconvert before further reaction; levoglucosenone cannot be an intermediate except in acid solutions, glucose and phenyl glucoside give products consistent with their being intermediates; and solvent phenol is incorporated in all products except for hydrocarbons. Dilute aqueous solutions of some of these intermediates can be reacted in the absence of phenol to produce liquids and char. The liquids contain about 90% phenols, and 75% of the liquid products is phenol itself. 18 references, 1 figure, 5 tables.

Miller, I.J.; Saunders, E.R.

1987-01-01

294

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.)

295

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

296

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

297

Improvement of superconducting properties of MgB2 by changing the argon ambient pressure and sintering conditions  

International Nuclear Information System (INIS)

We have investigated various characteristic properties depending on sintering conditions of MgB2 samples prepared by the standard solid state reaction method. It is inferred from experimental results that the crystallinity of samples were improved when the pressure of the Ar ambient increased. Also, it was found that the sintering temperature above 850 deg. C caused extremely high amount of decomposition of the superconductor phase. Finally, it was considered that the sintering process of MgB2 must be carried out under the pressure of Ar ambient higher than 8 bar to impede the volatility of Mg in the structure of MgB2. The Jc values of samples systematically enhanced with the increase of sintering time and in particular, the sample sintered for 180 min. exhibited the highest Jc (0) of 4.9 x 103 A cm-2 at 30 K. The obtained results demonstrate that the sintering conditions of MgB2 have a significant influence on Tc(onset) and Jc, which are directly related to practical applications of MgB2 based superconductor components.

298

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

299

Experimental device to investigate crack propagation in pressure vessel steel under BWR conditions  

International Nuclear Information System (INIS)

An experimental device is developed to investigate the crack growth behaviour of RPV steel specimens under service conditions. It will be installed in the experimental power station VAK-Kahl (BWR, 16 MWe). The in pile part is composed of a stable frame with a hydraulically actuated load mechanism, the specimen chain and a measuring instrumentation. The specimen chain, fastened between load mechanism and a lower fixing point at the frame, is made up of five compact tensile specimens (CT40) and the associated connecting links. Specimen strain, crack opening and temperature are measured; for neutron dose monitoring activation wires are disposed. Out of pile, in the reactor hall, the hydraulic loading system is installed. The loading force is generated by a 100 kN-material testing machine; it moves a piston in the control cylinder, which is connected to the loading bellows of the in pile section. The measuring and control equipment and a desk computer serving for data preparation and reduction is placed in the reactor control room. (orig.)

300

Molecular Studies of Surfaces under Reaction Conditions; Sum Frequency Generation Vibrational Spectroscopy, Scanning Tunneling Microscopy and Ambient Pressure X-Ray Photoelectron Spectroscopy  

Energy Technology Data Exchange (ETDEWEB)

Instruments developed in our laboratory permit the atomic and molecular level study of NPs under reaction conditions (SFG, ambient pressure XPS and high pressure STM). These studies indicate continuous restructuring of the metal substrate and the adsorbate molecules, changes of oxidation states with NP size and surface composition variations of bimetallic NPs with changes of reactant molecules.

Somorjai, G.A.

2009-11-11

 
 
 
 
301

A study on the numerical instability of COBRA-series subchannel analysis codes at low-pressure and low-flow conditions  

International Nuclear Information System (INIS)

The numerical instability at low-pressure and low-flow conditions has been confirmed to be the common problem of the existing COBRA-series subchannel analysis codes. In addition, the range of operating conditions at which the analyses by the codes are impossible has been evaluated. To evaluate the MATRA's inapplicable range of operating conditions of the SMART core that is to be operated at the low flow condition, i.e. about 30% of the flow of the existing commercial pressurized water reactors at the steady-state condition, the analyses of various operating conditions were performed by using several representative COBRA-series subchannel analysis codes including MATRA. TORC of CE, COBRA3CP of Siemens/KWU, COBRA4I of PNL, and MATRA of KAERI were chosen as the subchannel analysis codes to be evaluated. The various operating conditions used in the CHF tests carried out at the Winfrith Establishment of UKAEA were chosen as the conditions to be analyzed. As the result, the numerical instabilities at low-pressure and low-flow conditions occurred in the analyses by all of the codes. It was revealed that the MATRA code, which numerically more stable thatn the other codes, was not able to analyze the conditions of the pressure not more than 100 bar and the mass velocity not more than 300 kg/sec-m2. Hereafter it is required to find out the exact reason for the numerical instability of the existing COBRA-series subchannel analysis codes at low-pressure and low-flow coysis codes at low-pressure and low-flow conditions and to devise the new method to get over that numerical problem

302

Multiwell CO2 injectivity: impact of boundary conditions and brine extraction on geologic CO2 storage efficiency and pressure buildup.  

Science.gov (United States)

CO2 storage efficiency is a metric that expresses the portion of the pore space of a subsurface geologic formation that is available to store CO2. Estimates of storage efficiency for large-scale geologic CO2 storage depend on a variety of factors including geologic properties and operational design. These factors govern estimates on CO2 storage resources, the longevity of storage sites, and potential pressure buildup in storage reservoirs. This study employs numerical modeling to quantify CO2 injection well numbers, well spacing, and storage efficiency as a function of geologic formation properties, open-versus-closed boundary conditions, and injection with or without brine extraction. The set of modeling runs is important as it allows the comparison of controlling factors on CO2 storage efficiency. Brine extraction in closed domains can result in storage efficiencies that are similar to those of injection in open-boundary domains. Geomechanical constraints on downhole pressure at both injection and extraction wells lower CO2 storage efficiency as compared to the idealized scenario in which the same volumes of CO2 and brine are injected and extracted, respectively. Geomechanical constraints should be taken into account to avoid potential damage to the storage site. PMID:23971876

Heath, Jason E; McKenna, Sean A; Dewers, Thomas A; Roach, Jesse D; Kobos, Peter H

2014-01-21

303

Numerical simulation on the "S" characteristics and pressure fluctuation of reduced pump-turbine at start-up condition  

Science.gov (United States)

The performance of a reversible pump turbine with S-shaped characteristics is of great importance to the transition processes such as start-up and load rejection. In order to improve the "S" characteristics of reduced pump-turbine, several MGV (misaligned guide vane) schemes are calculated. The SST (shear stress turbulence) model is added to the N-S (Navier-strokes) governing equation. In order to predict the S-shaped curve accurately and develop a reliable tool for design improvement, the "S" characteristic is investigated in a whole pump-turbine including spiral casing, stay vanes, guide vanes, runner and draft tube. To validate the scheme reasonable, the mesh independent is tested. Comparison of unit discharge and unit speed performance showed that good correspondence is obtained between experimental data and calculated results. The "S shape" of reduced pump-turbine is eliminated with MGV schemes. Based on this, internal flow analysis is carried out adopting six typical MGV schemes at the same working condition. Through the calculation, we find that, first the pressure fluctuation is different between the guide vane and runner among the five MGV schemes, second the pressure fluctuation amplitude of MGV schemes D (4*35° and 16*6° average installed) is smallest, third the main frequency is the blade passing frequency and guide vane passing frequency at vane-less space and head cover, respectively. The conclusion is the "S shape" of pump-turbine can be improved with the average installed scheme.

Liu, D. M.; Zheng, J. S.; Wen, G. Z.; Zhao, Y. Z.; Shi, Q. H.

2012-11-01

304

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

305

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

306

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

307

Corrosion fatigue crack growth behaviour of low-alloy reactor pressure vessel steels under boiling water reactor conditions  

International Nuclear Information System (INIS)

The corrosion fatigue crack growth behaviour of different low-alloy reactor pressure vessel (RPV) steels and weld filler/heat-affected zone materials was systematically characterized under simulated boiling water reactor normal water and hydrogen water chemistry conditions by low-frequency fatigue tests with pre-cracked fracture mechanics specimens. The experiments were performed in oxygenated or hydrogenated high-purity or sulphate/chloride containing water at temperatures from 150 to 288 deg. C. In this paper, the observed synergistic effects of environmental, material and loading parameters on the environmental acceleration of fatigue crack growth in low-alloy RPV steels are discussed in the context of the Ford-Andresen model. Additionally, the adequacy and conservatism of the current 'ASME XI reference fatigue crack growth curves' of the ASME Boiler and Pressure Vessel Code are critically reviewed and assessed on the basis of the gathered experimental data base and this model. Based on the observed cracking behaviour and the Ford-Andresen model, a simple time-domain superposition model is suggested, which could reduce most of the undue conservatism and eliminate uncertainties of the existing codes and therefore serve as a basis for the development of improved reference fatigue crack growth curves

308

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

309

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

310

Reverse Spin-Crossover and High-Pressure Kinetics of the Heme?Iron Center Relevant for the Operation of Heme?Proteins under Deep-Sea Conditions.  

Science.gov (United States)

By design of a heme model complex with a binding pocket of appropriate size and flexibility, and by elucidating its kinetics and thermodynamics under elevated pressures, some of the pressure effects are demonstrated relevant for operation of heme-proteins under deep-sea conditions. Opposite from classical paradigms of the spin-crossover and reaction kinetics, a pressure increase can cause deceleration of the small-molecule binding to the vacant coordination site of the heme-center in a confined space and stabilize a high-spin state of its Fe?center. This reverse high-pressure behavior can be achieved only if the volume changes related to the conformational transformation of the cavity can offset the volume changes caused by the substrate binding. It is speculated that based on these criteria nature could make a selection of structures of heme?pockets that assist in reducing metabolic activity and enzymatic side reactions under extreme pressure conditions. PMID:25213097

Troeppner, Oliver; Lippert, Rainer; Shubina, Tatyana E; Zahl, Achim; Jux, Norbert; Ivanovi?-Burmazovi?, Ivana

2014-10-20

311

Nonlinear analysis for a double-channel two-phase natural circulation loop under low-pressure conditions  

International Nuclear Information System (INIS)

On the basis of the homogeneous flow model and Galerkin nodal approximation method, this study adopts the methodology in [Nucl. Eng. Des. 192 (1999) 31] to develop a nonlinear numerical model for a double-channel two-phase natural circulation loop. The calculated steady-state results provide a reasonable agreement against the experimental data in the high power region but overestimate in the low power region under both equal-heating and unequal-heating conditions. Nonlinear dynamics and stability boundary of the double-channel boiling natural circulation loop are also analyzed. Two unstable regions, type-I and type-II instabilities, are found in this system. Complex channel-to-channel interactions coupling with loop dynamics may occur in the double-channel natural circulation loop. For the equal-heating system, out-of-phase oscillations may prevail under the operating conditions that the gravitational pressure drops are very highly dominant, such as low subcooling and low power conditions. However, in-phase oscillations may exist in the medium to high power regions, where two-phase frictions are relatively important. For the unequal-heating system, the heating power difference between two channels may drive the system more unstable both in type-I and type-II regions. The two unequal-heating channels exhibit in-phase oscillation mode, instead of out-of-phase in the equal-heating system, at low subcooling and low power conditions. In addition, parametric effects on the s. In addition, parametric effects on the stability are also evaluated in this study

312

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

International Nuclear Information System (INIS)

rift. 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 attained after ?10-30 years, due to the influx from the hydrostatic head boundary condition imposed on top, about 13.2 m above the drying piece of drift wall. The total net liquid volume that was evacuated out of the clay into the gallery was VNET(OUT) ? 20 l/m of the drift (axially). Given the assumed symmetries of 'Type I', with a 2 m piece of drift wall submitted to suction, 20 liters/m is in fact the amount of water evacuated through 1/8 of the drift's perimeter. The vertical extent of desaturation based on the 'zero suction' iso-surface is Z(t)?40 cm at t ? 1 year, and it reaches the stable value Z(t)?60 cm for t?? (in practice, this is attained after t?10-30 years). It was also shown, interestingly, that there is at first a short 'decompression' phase with decreasing positive pore pressures in the clay, before desaturation becomes significant. Finally, some uncertainty may arise regarding the definition of 'desaturation' (0-pressure iso-surface vs. saturation iso-surface). (authors)

313

Metal-silicate partitioning of potassium at high pressure and temperature conditions and implications for thermal history of the Earth  

Science.gov (United States)

The possible presence of potassium in the Earth's core as a radioactive heat source can have a significant influence on the thermal evolution of the Earth (Buffett, 2002 GRL; Labrosse, 2003 PEPI). Core-mantle equilibration at high P-T (e.g. ~30 GPa, ~3450 K [Righter, 2011 EPSL]) was suggested from the mantle contents of siderophile elements. Basal magma ocean (Labrosse et al., 2007 Nature) also should be equilibrated with molten iron at the core-mantle boundary (CMB) (~135 GPa) due to its gravitational stability (Nomura et al., 2011 Nature). Previous experimental studies on potassium partitioning between liquid metal and silicate melt showed contradictory results on the concentration of potassium in the Earth's core because of experimental artifacts (K loss in metal phase), different (simplified) chemical compositions for study and large extrapolations to high P-T which suits for core-mantle equilibration at the base of the magma ocean. Recently, Corgne et al. (2007 EPSL) performed the partitioning experiments up to 7.7 GPa and 2200°C with chemical compositions of CI chondrite doped with moderate amount of S and K and revealed a significant effect of O contents in molten alloy on K partition coefficient while with negligible effect of P-T and S and C contents. The change in electronic structure of potassium from 4s- to 3d-like was predicted by theory (Bukowinski, 1976 GRL) and potassium alloying with nickel and iron was reported by experiments using diamond anvil cell at ~30 GPa and 2200 K (Parker et al., 1997 Science; Lee and Jeanloz, 2003 GRL). So, it is important to investigate the effect of pressure on K partition coefficient at the pressure conditions above ~30 GPa up to 135 GPa. Hirao et al. (2006 GRL) performed melting experiment at 135 GPa and 3500 K using laser-heated diamond anvil cell (LHDAC) and showed the value of partition coefficient Dk is 0.15, but their results lack the elemental mass balances between run products and starting materials. Our melting experiments were performed at high P-T conditions using LHDAC. Fine powdered mixtures of Fe (or Fe-FeS, Fe-FeSi) metal and gels with chemical compositions of KLB-1 peridotite doped with 1wt% K were used as a starting material. The gel powder was dehydrated by heating to 1273 K for 1 h in a H2-CO2 gas mixing furnace, in which oxygen fugacity was controlled to be slightly above the iron-wustite buffer. Pressure was measured after quenching with the Raman shift of diamond anvil. Ar was used as a pressure medium. The sample was heated from double side using Nd:YLF laser. A recovered sample was processed with Ion Slicer (JEOL EM-09100 IS), and subsequently examined by energy-dispersive X-ray spectrometry (EDS) attached with field emission scanning electron microscope (FE-SEM: JOEL JSM-7000F). Our preliminary results at ~20 GPa, fO2 of ~IW-1 and high temperature up to 5000 K with KLB-1 gel and S-free metal shows the clear correlation between O contents in molten iron and K partition coefficients suggested by Corgne et al. (2007). The results of partitioning coefficient at high P-T range up to primordial CMB conditions will be discussed in our presentation.

Nomura, R.; Hirose, K.

2011-12-01

314

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. 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)

315

Investigations on tailoring the deposition conditions in HIPIMS by varying the pulse durations and the argon partial pressure  

International Nuclear Information System (INIS)

In most cases HIPIMS is used to get the highest possible ionisation of the deposition particles, which is realised by pulse durations with short on- and very long off-times. These conditions are combined with a more or less pronounced decrease in deposition rate. In this work the pulse configuration has been varied. A three dimensional matrix of parameters was spanned, made of 3 on- and 3 off-times at 4 argon partial pressures. The average power was kept constant and the data achieved were additionally compared to DC-magnetron sputtering. The experiments were carried out using 50 mm diameter targets made of Ti, powered by a MELEC SPIK1000A pulser unit. The deposition rate was measured by quartz microbalance mounted in front of the target. Peak current density and target voltage were recorded and time averaged optical emission spectroscopy (t.a.OES) measurements provided information about the ionisation conditions in the plasma. The results of the data analysis provide a coherent overview of the impact of the HIPIMS parameters as well as of their complex interrelations.

316

Investigations on tailoring the deposition conditions in HIPIMS by varying the pulse durations and the argon partial pressure  

Science.gov (United States)

In most cases HIPIMS is used to get the highest possible ionisation of the deposition particles, which is realised by pulse durations with short on- and very long off-times. These conditions are combined with a more or less pronounced decrease in deposition rate. In this work the pulse configuration has been varied. A three dimensional matrix of parameters was spanned, made of 3 on- and 3 off-times at 4 argon partial pressures. The average power was kept constant and the data achieved were additionally compared to DC-magnetron sputtering. The experiments were carried out using 50 mm diameter targets made of Ti, powered by a MELEC SPIK1000A pulser unit. The deposition rate was measured by quartz microbalance mounted in front of the target. Peak current density and target voltage were recorded and time averaged optical emission spectroscopy (t.a.OES) measurements provided information about the ionisation conditions in the plasma. The results of the data analysis provide a coherent overview of the impact of the HIPIMS parameters as well as of their complex interrelations.

Balzer, M.; Fenker, M.

2012-09-01

317

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)

318

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

319

Numerical simulation on the 'S' characteristics and pressure fluctuation of reduced pump-turbine at start-up condition  

International Nuclear Information System (INIS)

The performance of a reversible pump turbine with S-shaped characteristics is of great importance to the transition processes such as start-up and load rejection. In order to improve the 'S' characteristics of reduced pump-turbine, several MGV (misaligned guide vane) schemes are calculated. The SST (shear stress turbulence) model is added to the N-S (Navier-strokes) governing equation. In order to predict the S-shaped curve accurately and develop a reliable tool for design improvement, the 'S' characteristic is investigated in a whole pump-turbine including spiral casing, stay vanes, guide vanes, runner and draft tube. To validate the scheme reasonable, the mesh independent is tested. Comparison of unit discharge and unit speed performance showed that good correspondence is obtained between experimental data and calculated results. The 'S shape' of reduced pump-turbine is eliminated with MGV schemes. Based on this, internal flow analysis is carried out adopting six typical MGV schemes at the same working condition. Through the calculation, we find that, first the pressure fluctuation is different between the guide vane and runner among the five MGV schemes, second the pressure fluctuation amplitude of MGV schemes D (4*35° and 16*6° average installed) is smallest, third the main frequency is the blade passing frequency and guide vane passing frequency at vane-less space and head cover, respectively. The conclusion is the 'S shape' of pump-turbine can be improved withpe' of pump-turbine can be improved with the average installed scheme.

320

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.)

 
 
 
 
321

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

Energy Technology Data Exchange (ETDEWEB)

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.)

Foehl, J.; Weissenberg, T. [Materialpruefungsanstalt, Univ. Stuttgart (Germany); Gomez-Briceno, D.; Lapena, J. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT) (Spain); Ernestova, M.; Zamboch, M. [Nuclear Research Inst. (NRI) (Czech Republic); Seifert, H.P.; Ritter, S. [Paul Scherrer Inst. (PSI) (Switzerland); Roth, A.; Devrient, B. [Framatome ANP GmbH (F ANP) (Germany); Ehrnsten, U. [Technical Research Centre of Finland (VTT) (Finland)

2004-07-01

322

Hypertension (High Blood Pressure)  

Science.gov (United States)

... they think about their blood pressure. Understanding Blood Pressure Every person needs blood pressure to live. Without ... women get this condition. How Does High Blood Pressure Affect the Body? High blood pressure adds to ...

323

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

324

Control of a fluid particle under simulated deep-ocean conditions in a high-pressure water tunnel  

Science.gov (United States)

An apparatus that permits the observation of liquid CO2 particles in a simulated deep-ocean environment was designed, modeled, constructed, and tested. Analysis concerning the vertical stability and control of the fluid particle in a countercurrent flow loop is presented. The vertical position of the particle was found to vary due to the gradual dissolution of the CO2 into the water and various other random effects. Using linearized equations for spherical particle motion in the fluid flow, a second-order dynamic equation is derived and analyzed. The servocontrol system consists of a video system that digitizes particle position in a viewing window and a centrifugal pump that can control the speed of the countercurrent flow in order to maintain the particle within the observation window of a charge-coupled device camera. Currently, the system is being used to obtain information on the dissolution behavior of CO2 in seawater at various conditions of pressure and temperature that simulate ocean depths down to 3400m. This information can be used to predict the fate of CO2 drops in the ocean, whether released from natural seeps, leaks from suboceanic geologic CO2 storage sites, or from engineered deep-ocean injection systems. The study of other liquids and gases is also possible.

Haljasmaa, Igor V.; Vipperman, Jeffrey S.; Lynn, Ronald J.; Warzinski, Robert P.

2005-02-01

325

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

Energy Technology Data Exchange (ETDEWEB)

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.

Lucchini, Tommaso, E-mail: tommaso.lucchini@polimi.i [Internal Combustion Engine Group, Dipartimento di Energia, Politecnico di Milano, Via Lambruschini 4, 20156 Milan (Italy); D' Errico, Gianluca; Ettorre, Daniele [Internal Combustion Engine Group, Dipartimento di Energia, Politecnico di Milano, Via Lambruschini 4, 20156 Milan (Italy)

2011-02-15

326

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.

327

Influence of neutron exposure, chemical composition and metallurgical condition, on the irradiation shift of reactor pressure vessel steels  

International Nuclear Information System (INIS)

The work described in this paper is part of a continuing program to produce well-characterized data for use in the development of models for the prediction of irradiation shift in pressurized water reactor steels. Results are presented for around 50 batches of Charpy specimens, irradiated either in the DIDO or PLUTO heavy water, or in the HERALD light water, research reactors, to doses up to 35 mdpa (approx. 2 x 1019) n/cm2, E > 1 MeV). The materials include A533B plate, weld, and heat affected zones. The results are compatible with a log/log relationship between dose and shift with an exponent of 0.5 for all materials. They also show that irradiation response is dependent on heat treatment condition. If it is assumed that the Varsik and Byrne Chemistry Relationship, or a similar expression, is an appropriate parameter to characterize the effect of chemical composition on irradiation sensitivity, the results also demonstrate a difference between plate and weld irradiation sensitivity. An empirical model of the data has been developed and assessed, and this is compared with the Odette physically-based irradiation damage model

328

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)

329

Readiness of teenagers to will pressures and pedagogical conditions of their training in the course of physical training at comprehensive school.  

Directory of Open Access Journals (Sweden)

Full Text Available The main components in the structure of general school students' readiness to the will pressures, such as cognitive, motivational-emotional, active are considered. 318 students f the middle school age took part in the experiment. As a result of certifying experiment all the students were nominally divided into tree groups: with high, middle and law levels of readiness to the will pressures. The effectiveness of the proposed pedagogical conditions was proved as well as readiness to the will pressures training models for teenagers in the process of physical education at comprehensive school were developed.

Dudnik I.O.

2011-04-01

330

Photovoltaic barometer; Barometre photovoltaique  

Energy Technology Data Exchange (ETDEWEB)

The photovoltaic sector is continuing on track, just as the extent of solar energy's electricity-generating potential is dawning on the public mind. The annual global installation figure was up more than twofold in 2010 (rising from just short of 7000 MWp in 2009). It leapt to over 16000 MWp, bringing worldwide installed photovoltaic capacity close to 38000 MWp. The photovoltaic power generated in the European Union at the end of 2010 reached 22.5 TWh which means an additional capacity of 13023 MWp during 2010. Concerning the cumulated installed capacity, Germany and Spain rank first and second in the European Union with respectively 17370 MWp and 3808 MWp

Anon.

2011-04-15

331

Photovoltaic barometer; Barometre photovoltaique  

Energy Technology Data Exchange (ETDEWEB)

spain and Germany set the pace for the world photovoltaic market in 2008, which grew to more than twice its 2007 size. The European Union continued to drive photocell installation with an additional 4 592.3 MWp in 2008, or 151.6% growth over 2007. However, European growth prospects for the photovoltaic market in 2009 are being dampened by the global financial crisis and the scheduled slow-down of the Spanish market. (author)

Anon

2009-04-15

332

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)

333

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

334

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

335

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

336

Thermal-mechanical modelling of the pressure tube following fuel element contact under LOCA conditions in a CANDU-PHWR  

International Nuclear Information System (INIS)

This paper quantifies the thermal-mechanical effects of potential contact between the fuel element and the pressure tube (FE/PT contact) during a postulated large break LOCA transient in a CANDU reactor. At issue is the possibility of local failure of the pressure tube early in the LOCA transient. Calculations have been performed using the code MINI-SMARTT which was developed specifically for this analysis. It is shown that pressure tube local strain is most sensitive to the contact conductance, contact width, and transient time of FE/PT contact. The strain response of the pressure tube is derived over a broad range for the above parameters. A critical FE/PT contact conductance value is derived as a function of contact width and judged to be sufficiently high that pressure tube failure would be precluded

337

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

338

Constraining the Depth of a Martian Magma Ocean through Metal-Silicate Partitioning Experiments: The Role of Different Datasets and the Range of Pressure and Temperature Conditions  

Science.gov (United States)

Mars accretion is known to be fast compared to Earth. Basaltic samples provide a probe into the interior and allow reconstruction of siderophile element contents of the mantle. These estimates can be used to estimate conditions of core formation, as for Earth. Although many assume that Mars went through a magma ocean stage, and possibly even complete melting, the siderophile element content of Mars mantle is consistent with relatively low pressure and temperature (PT) conditions, implying only shallow melting, near 7 GPa and 2073 K. This is a pressure range where some have proposed a change in siderophile element partitioning behavior. We will examine the databases used for parameterization and split them into a low and higher pressure regime to see if the methods used to reach this conclusion agree for the two sets of data.

Righter, K.; Chabot, N.L.

2009-01-01

339

Definition of routine conditions of transport: a perspective on pressure and temperature for excepted and industrial packages as required by ST-1  

International Nuclear Information System (INIS)

The implementation of ST-1 will bring a change to the requirements for packages to withstand ambient temperatures and pressures that are likely to be encountered in routine transport. This paper, making use of published data, postulates an environment and then considers the physical effect of that environment on excepted and industrial packages. The effect of atmospheric pressure changes is considered together with pressures arising from ambient temperature changes. Assuming a constant volume the pressure that could be developed within a package is estimated to be 21.4 kPa for transport in the UK at the highest road elevation. This equates to a volume change of 23% assuming constant pressure and variable volume. The constant pressure case is applicable to a wrapped or bagged package and the constant volume to a drum. Information from a major drum manufacturer indicates that a standard 200 litre drum may experience deformation of the lid beyond its elastic limit (particularly if the route is over mountain passes), although it is still likely to retain its contents (up to a pressure differential of 100 kPa). The paper poses the following questions: (1) Are the conditions considered for the UK realistic and acceptable to the Competent Authority? If not what should be used? (2) Is a drum capable of withstanding a 1.2 m drop test in its pressurised configuration, or does it have to? (3) Is there operational experience which refutes or supports the above?. (author)

340

Computer simulations of a 1/5-scale experiment of a Mark I boiler water reactor pressure-suppression system under hypothetical LOCA conditions  

Energy Technology Data Exchange (ETDEWEB)

The CHAMP computer code was employed to simulate a plane-geometry cross section of a Mark I boiling water reactor toroidal pressure suppression system air discharge experiment under hypothetical loss-of-coolant accident conditions. The experiments were performed at the Lawrence Livermore Laboratory on a /sup 1///sub 5/-scale model of the Peach Bottom Nuclear Power Plant.

Edwards, L.L.

1978-05-02

 
 
 
 
341

Computer simulations of a 1/5-scale experiment of a Mark I boiler water reactor pressure-suppression system under hypothetical LOCA conditions  

International Nuclear Information System (INIS)

The CHAMP computer code was employed to simulate a plane-geometry cross section of a Mark I boiling water reactor toroidal pressure suppression system air discharge experiment under hypothetical loss-of-coolant accident conditions. The experiments were performed at the Lawrence Livermore Laboratory on a 1/5-scale model of the Peach Bottom Nuclear Power Plant

342

Comparison of pressure vessel integrity analyses and approaches for VVER 000 and PWR vessels for PTS conditions  

Energy Technology Data Exchange (ETDEWEB)

Currently, license renewals and plant-life extension are important issues for nuclear industry. Pressure vessel integrity is one of the main concerns related to these issues. Pressure vessel integrity is of prime concern for pressurized reactors, since they operate at higher pressures and neutron fluxes when compared to boiling water reactors. Pressure vessel integrity analyses for two commercial pressurized water reactors are performed in this study; a Westinghouse 4 loop 1000 MW PWR and a VVER 1000/320. Two most limiting loss of coolant accidents (LOCA) for pressurized thermal shock (PTS) are considered and deterministic and probabilistic failure analyses are performed. Differences in eastern and western regulatory approaches are also taken into account. Among the vessels simulated, the maximum nil ductility transition temperatures are found to be below the relevant regulatory limit. However, the results of probabilistic analyses are observed to be above the prescribed national limits. This is attributed to the use of rather conservative assumptions used in this study. Findings of this study may help the re-evaluation efforts of PTS screening criteria.

Guelol, Oya Oezdere; Colak, Uener E-mail: uc@nuke.hacettepe.edu.tr

2003-12-01

343

Comparison of pressure vessel integrity analyses and approaches for VVER 000 and PWR vessels for PTS conditions  

International Nuclear Information System (INIS)

Currently, license renewals and plant-life extension are important issues for nuclear industry. Pressure vessel integrity is one of the main concerns related to these issues. Pressure vessel integrity is of prime concern for pressurized reactors, since they operate at higher pressures and neutron fluxes when compared to boiling water reactors. Pressure vessel integrity analyses for two commercial pressurized water reactors are performed in this study; a Westinghouse 4 loop 1000 MW PWR and a VVER 1000/320. Two most limiting loss of coolant accidents (LOCA) for pressurized thermal shock (PTS) are considered and deterministic and probabilistic failure analyses are performed. Differences in eastern and western regulatory approaches are also taken into account. Among the vessels simulated, the maximum nil ductility transition temperatures are found to be below the relevant regulatory limit. However, the results of probabilistic analyses are observed to be above the prescribed national limits. This is attributed to the use of rather conservative assumptions used in this study. Findings of this study may help the re-evaluation efforts of PTS screening criteria

344

Influence of the synthesis conditions of silicon nanodots in an industrial low pressure chemical vapor deposition reactor  

International Nuclear Information System (INIS)

Experiments conducted in an industrial tubular low pressure chemical vapor deposition (LPCVD) reactor have demonstrated the reproducibility and spatial uniformity of silicon nanodots (NDs) area density and mean radius. The wafer to wafer uniformity was satisfactory (density and radius standard deviations 11 and 6.5 x 1011 NDs/cm2 for the two highest silane pressures tested in the range 60-150 Pa

345

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

346

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

347

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

Science.gov (United States)

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.

Kato, Toru; Stauss, Sven; Kato, Satoshi; Urabe, Keiichiro; Baba, Motoyoshi; Suemoto, Tohru; Terashima, Kazuo

2012-11-01

348

Effects of Partial O(2) Pressure, Partial CO(2) Pressure, and Agitation on Growth Kinetics of Azospirillum lipoferum under Fermentor Conditions.  

Science.gov (United States)

Azospirillum lipoferum crt1 was grown in batch cultures under standard conditions at 85% saturation of dissolved oxygen (DO) and 30-g/liter glucose concentrations. Kinetic studies revealed nutritional limitations of growth and the presence of an initial lag phase prior to consumption of glucose. The influences of various gaseous environments and shear stress on growth, i.e., various conditions of agitation-aeration, were characterized. Faster growth in the first stages of the culture and shorter duration of the lag phase were observed at DO concentrations of <30% saturation. The possible influences of dissolved CO(2) concentration or shear stress or both were discounted, and we confirmed the detrimental effect of high DO levels (up to 80% saturation) and the favorable influence of low DO concentrations (lower than 30% saturation) on growth. It was concluded that the gaseous environment, i.e., the DO concentration, needs to be considered as an operating parameter and be accurately controlled to ensure optimal growth of Azospirillum cells. PMID:16348331

Paul, E; Mulard, D; Blanc, P; Fages, J; Goma, G; Pareilleux, A

1990-11-01

349

Grid spacer effect on reflood behavior observed at reflood experiment with 5 x 5 bundle test section under wide pressure condition  

International Nuclear Information System (INIS)

There are a lot of works on quenching behavior and minimum film boiling temperature. However, these phenomena are not clear enough for high-pressure condition. Therefore, reflood experiments were performed with 5 x 5-bundle test section under pressure of 2 MPa to 15.5 MPa. Geometry of a bundle test section used at the present experiments was principally the same as that of conventional PWRs. Grid spacers used at the present experiments were designed to simulate conventional ones. Data on clad temperature transient, quench time, and heat transfer coefficient were obtained. Quenching took place at several elevations where grid spacers located, and then each quenching front propagated downstream, or toward upper elevations under high mass flux condition. Thus, grid spacers showed influence of significant promotion of quenching occurrence above grid spacers. This promotion is more significant at higher mass flux and slightly significant at higher pressure. Under such condition, grid spacer effect is not negligible to analyze thermal-hydraulics accurately for PWRs and BWRs accidents. On the other hand, grid spacer effect on quenching occurrence is small at lower mass flux and lower pressure. The boundary of above two cases was determined experimentally. In order to study above characteristics, heat transfer coefficient distribution along the distance of the grid spacer was investigated. Heat transfer coefficient was enhanced above grid spacers and the enhancement was decayed along the distance of the grid spacer. The enhancement at the grid spacer was significant at higher mass flux. Relaxation length of grid spacer effect was about 0.1 m. Thus, effects of mass flux and pressure on promotion of quenching occurrence is explained by heat transfer enhancement above the grid spacers. (author)

350

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

351

Comprehensive two-dimensional gas chromatography under high outlet pressure conditions: a new approach to correct the flow-mismatch issue in the two dimensions.  

Science.gov (United States)

The typical column sets employed in comprehensive two-dimensional gas chromatography (GC × GC) suffer from the impossibility to fully exploit the efficiency of both dimensions simultaneously. Adding a restrictor at the end of the second dimension is a possible approach to adjust the linear velocity profile. Under these high outlet pressure conditions the second dimension becomes much slower while the effect on the primary column is limited. The gap in terms of optimum inlet pressures is thus reduced. A program written in Microsoft Excel was used to calculate the efficiencies of the two dimensions in GC × GC at different outlet pressures. A GC × GC set-up with a restrictor at the end of the second dimension column was successfully installed. Experiments proved that this is a possible way to have a better exploitation of the columns. The chromatograms obtained for a number of applications confirm that the separations achieved at elevated outlet pressure are more efficient than those obtained with the same column set under atmospheric outlet conditions. The price to pay is that the separations become considerably slower. PMID:24513348

Peroni, Daniela; Janssen, Hans-Gerd

2014-03-01

352

A detailed TEM and SEM study of Ni-base alloys oxide scales formed in primary conditions of pressurized water reactor  

Digital Repository Infrastructure Vision for European Research (DRIVER)

he oxide film formed on nickel-based alloys in pressurized water reactors (PWR) primary coolant conditions (325 °C, aqueous media) is very thin, in the range of 1–100 nm thick, depending on the surface state and on the corrosion test duration. The nature and the structure of this scale have been investigated by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). TEM observations revealed an oxide layer divided in two parts. The internal layer was mainly composed ...

Sennour, Mohamed; Marchetti, Loic; Martin, Frantz; Perrin, Ste?phane; Molins, Re?gine; Pijolat, Miche?le

2010-01-01

353

Condition-oriented servicing of gas pressure control and measuring systems; Zustandsorientierte Instandhaltung von Gas-Druckregel- und -Messanlagen  

Energy Technology Data Exchange (ETDEWEB)

Condition monitoring and assessment are indispensable today. DBI Gas- und Umwelttechnik GmbH, in cooperation with the Technical Universities of Dortmund and Dresden, developed component-specific approaches for condition monitoring and assessment of the gas-transporting components of gas presure control and measuring systems. The work was carried out in the context of a DVGW research project. (orig.)

Huettenrauch, Jens; Mueller-Syring, Gert [DBI Gas- und Umwelttechnik GmbH, Leipzig (Germany); Gampe, Uwe; Schoene, Sophie [Technische Univ. Dresden (Germany). Inst. fuer Energietechnik; Bruemmer, Andreas; Nikolov, Alexander [Technische Univ. Dortmund (Germany). Fachgebiet Fluidtechnik

2010-06-15

354

Modelling for post-dryout heat transfer and droplet sizes at low pressure and low flow conditions  

International Nuclear Information System (INIS)

A correlation describing the initial droplet size just after the CHF position at low mass flux is suggested through regression analysis. The history-dependent post-dryout model of Varone and Rohsenow replaced by the Webb-Chen model for wall-vapor heat transfer is used as a reference model in the analysis. In the post-dryout region at low pressure and low flow, it is found that the suggested one-dimensional mechanistic model is valid only in the churn-turbulent flow regime (j*g = 0.5 ? 4.5). It is also suggested that the droplet size generated from the churn-turbulent surface is dependent not only on the pressure but also on the vapor velocity. It turns out that the present model can predict the measured cladding and vapor temperatures within 20% and 15%, respectively

355

Effect of rotor design tip speed on noise of a 1.21 pressure ratio model fan under static conditions  

Science.gov (United States)

Preliminary results are presented for a reverberant-field noise investigation of three fan stages designed for the same overall total pressure ratio of 1.21 at different rotor tip speeds (750, 900, and 1050 fps). The stages were tested statically in a 15-in.-dia model lift fan installed in a wing pod located in the test section of a wind tunnel. Although the fan stages produced essentially the same design pressure ratio, marked differences were observed in the variation of fan noise with fan operating speed. At design speed, the forward-radiated sound power level was approximately the same for the 750 and 900 fps stages. For the 1050 fps stage, the design-speed forward-radiated power level was about 7 dB higher due to the generation of multiple pure tone noise.

Loeffler, I. J.; Lieblein, S.; Stockman, N. O.

1973-01-01

356

Probabilistic structural integrity assessment of reactor coolant pressure boundary piping. 1. The scatter of welding conditions and welding residual stress  

International Nuclear Information System (INIS)

Residual stress by welding would be one of the most significant factors in evaluating failure probabilities of PLR piping since the SCC growth behavior is strongly affected by residual stress distribution. The residual stress distribution is well known to change caused by varying of welding conditions such as groove shape, electrical voltage and current, inter-pass temperature, etc. Therefore, to evaluate the scatter of welding condition and their influence on residual stress is important to assess the structural integrity of PLR piping. In present work, the scatters of welding conditions were evaluated by producing some series of butt-welding pipe specimens made of stainless steel. Residual stress distributions due to welding were measured by applying X-ray diffraction method and stress relief method. Measured welding conditions and residual stress distributions are provided to determine the conditions of welding residual stress simulations and to confirm an accuracy of the simulation described in the following paper. (author)

357

Theoretical assessment of boron incorporation in nickel ferrite under conditions of operating nuclear pressurized water reactors (PWRs)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

358

Rheology and microstructure of carrot and tomato emulsions as a result of high-pressure homogenization conditions.  

Science.gov (United States)

High-pressure homogenization, as a way to further mechanically disrupt plant cells and cell walls compared to conventional blending, has been applied to thermally treated and comminuted carrot and tomato material in the presence of 5% olive oil. Mixes of both vegetables in a 1:1 ratio were also included. Both the effect of homogenization pressure and the effect of multiple process cycles were studied. The different microstructures generated were linked to different rheological properties analyzed by oscillatory and steady state measurements. The results showed that while carrot tissue requires a high shear input to be disrupted into cells and cell fragments, tomato cells were broken across the cell walls already at moderate shear input, and the nature of the tomato particles changed to amorphous aggregates, probably composed of cell contents and cell wall polymers. All the plant stabilized emulsions generated were stable against creaming under centrifugation. While for tomato a low-pressure multiple cycle and a high-pressure single-cycle process led to comparable microstructures and rheological properties, carrot showed different rheological properties after these treatments linked to differences in particle morphology. Mixes of carrot and tomato showed similar rheological properties after homogenizing in a single or in a split-stream process. Practical Application: Following consumers' demand, the food industry has shown a growing interest in manufacturing products free of gums and stabilizers, which are often perceived as artificial. By tailored processing, fresh plant material could be used to structure food products in a more natural way while increasing their nutritional quality. PMID:21535664

Lopez-Sanchez, Patricia; Svelander, Cecilia; Bialek, Lucy; Schumm, Stephan; Langton, Maud

2011-01-01

359

Electrical Properties of amphiboles from the Kola super deep borehole, Russia, at mantle pressure and temperature conditions  

International Nuclear Information System (INIS)

We present here for the first time, the temperature and pressure dependence of the electrical resistivity of ferro-actinolite amphibole from the World's deepest borehole, the Kola super-deep borehole (KSDB) up to the depth of 12.84 km. High-pressure and high-temperature measurements were carried out by using an opposed anvil system up to 700 K and 4 GPa. Ten samples from different depths (from the surface to the deepest 12,890 m) were investigated for their compositional, structural and electrical behaviour. Ferro-actinolite sample exhibits a thermally induced phase transformation to cummingtonite-clinopyroxene—quartz assemblages at 780 K and 0.5 GPa. The transformation temperature is found to be decreasing with the increase of pressure and reaches a value of 680 K at 6.0 GPa. The conductivity activation energy, (determined from the temperature dependence of conductivity) of the ferroactinolite is found to be decreasing from 0.8 eV at 0.5 GPa to 0.30 eV at 6 GPa. The present study indicates that the amphiboles at deeper crustal level is more conducting and bears significance in understanding the physical properties of rocks at the deep continental crust.

360

High-pressure crystal structure of elastically isotropic CaTiO3 perovskite under hydrostatic and non-hydrostatic conditions  

International Nuclear Information System (INIS)

The structural evolution of orthorhombic CaTiO3 perovskite has been studied using high-pressure single-crystal x-ray diffraction under hydrostatic conditions up to 8.1 GPa and under a non-hydrostatic stress field formed in a diamond anvil cell (DAC) up to 4.7 GPa. Under hydrostatic conditions, the TiO6 octahedra become more tilted and distorted with increasing pressure, similar to other 2:4 perovskites. Under non-hydrostatic conditions, the experiments do not show any apparent difference in the internal structural variation from hydrostatic conditions and no additional tilts and distortions in the TiO6 octahedra are observed, even though the lattice itself becomes distorted due to the non-hydrostatic stress. The similarity between the hydrostatic and non-hydrostatic cases can be ascribed to the fact that CaTiO3 perovskite is nearly elastically isotropic and, as a consequence, its deviatoric unit-cell volume strain produced by the non-hydrostatic stress is very small; in other words, the additional octahedral tilts relevant to the extra unit-cell volume associated with the deviatoric unit-cell volume strain may be totally neglected. This study further addresses the role that three factors-the elastic properties, the crystal orientation and the pressure medium-have on the structural evolution of an orthorhombic perovskite loaded in a DAC under non-hydrostatic conditions. The influence of these factors can be clearly visualized by plotting the three-dimensional distribution of the deviatoric unit-cell volume strain in relation to the cylindrical axis of the DAC and indicates that, if the elasticity of a perovskite is nearly isotropic as it is for CaTiO3, the other two factors become relatively insignificant. (paper)

 
 
 
 
361

Deformation of olivine under mantle conditions: An in situ high-pressure, high-temperature study using monochromatic synchrotron radiation  

Energy Technology Data Exchange (ETDEWEB)

Polycrystalline samples of San Carlos olivine were deformed at high-pressure (2.8-7.8 GPa), high-temperature (1153 to 1670 K), and strain rates between 7.10{sup -6} and 3.10{sup -5} s{sup -1}, using the D-DIA apparatus. Stress and strain were measured in situ using monochromatic X-rays diffraction and imaging, respectively. Based on the evolution of lattice strains with total bulk strain and texture development, we identified three deformation regimes, one at confining pressures below 3-4 GPa, one above 4 GPa, both below 1600 K, and one involving growth of diffracting domains associated with mechanical softening above {approx}1600 K. The softening is interpreted as enhanced grain boundary migration and recovery. Below 1600 K, elasto-plastic self-consistent analysis suggests that below 3-4 GPa, deformation in olivine occurs with large contribution from the so-called 'a-slip' system [100](010). Above {approx}4 GPa, the contribution of the a-slip decreases relative to that of the 'c-slip' [001](010). This conclusion is further supported by texture refinements. Thus for polycrystalline olivine, the evolution in slip systems found by previous studies may be progressive, starting from as low as 3-4 GPa and up to 8 GPa. During such a gradual change, activation volumes measured on polycrystalline olivine cannot be linked to a particular slip system straightforwardly. The quest for 'the' activation volume of olivine at high pressure should cease at the expense of detailed work on the flow mechanisms implied. Such evolution in slip systems should also affect the interpretation of seismic anisotropy data in terms of upper mantle flow between 120 and 300 km depth.

Hilairet, Nadège; Wang, Yanbin; Sanehira, Takeshi; Merkel, Sébastien; Mei, Shenghua (CNRS-UMR); (UC); (UMM)

2012-03-15

362

Unique rod lens/video system designed to observe flow conditions in emergency core coolant loops of pressurized water reactors  

International Nuclear Information System (INIS)

Techniques and equipment are described which are used for video recordings of the single- and two-phase fluid flow tests conducted with the PKL Spool Piece Measurement System designed by Lawrence Livermore Laboratory and EG and G Inc. The instrumented spool piece provides valuable information on what would happen in pressurized water reactor emergency coolant loops should an accident or rupture result in loss of fluid. The complete closed-circuit television video system, including rod lens, light supply, and associated spool mounting fixtures, is discussed in detail. Photographic examples of test flows taken during actual spool piece system operation are shown

363

Synthesis of super-dense phase of aluminum under extreme pressure and temperature conditions created by femtosecond laser pulses in sapphire  

Science.gov (United States)

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 ~ 100 fs and an energy of ~ 100 nJ. Fast, explosive expansion of photogenerated high-density plasma created strong heating and pressure transients with peak temperature and pressure of ~ 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

2012-03-01

364

Effects of pressure drop, particle size and thermal conditions on retention and efficiency in supercritical fluid chromatography.  

Science.gov (United States)

The effects of particle size and thermal insulation on retention and efficiency in packed-column supercritical fluid chromatography with large pressure drops are described for the separation of a series of model n-alkane solutes. The columns were 2.0mm i.d.x150mm long and were packed with 3, 5, or 10-mum porous octylsilica particles. Separations were performed with pure carbon dioxide at 50 degrees C at average mobile phase densities of 0.47g/mL (107bar) and 0.70g/mL (151bar). The three principal causes of band broadening were the normal dispersion processes described by the van Deemter equation, changes in the retention factor due to the axial density gradient, and radial temperature gradients associated with expansion of the mobile phase. At the lower density the use of thermal insulation resulted in significant improvements in efficiency and decreased retention times at large pressure drops. The effects are attributed to the elimination of radial temperature gradients and the concurrent enhancement of the axial temperature gradient. Thermal insulation had no significant effect on chromatographic performance at the higher density. A simple expression to predict the onset of excess efficiency loss due to the radial temperature gradient is proposed. PMID:19767007

Poe, Donald P; Schroden, Jonathan J

2009-11-01

365

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  

International Nuclear Information System (INIS)

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?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/TiO2 powder catalyst

366

Application of a macromolecular chelating agent in chemical mechanical polishing of copper film under the condition of low pressure and low abrasive concentration  

Science.gov (United States)

The mechanism of the FA/O chelating agent in the process of chemical mechanical polishing (CMP) is introduced. CMP is carried on a ?300 mm copper film. The higher polishing rate and lower surface roughness are acquired due to the action of an FA/O chelating agent with an extremely strong chelating ability under the condition of low pressure and low abrasive concentration during the CMP process. According to the results of several kinds of additive interaction curves when the pressure is 13.78 kPa, flow rate is 150 mL/min, and the rotating speed is 55/60 rpm, it can be demonstrated that the FA/O chelating agent plays important role during the CMP process.

Yan, Li; Yuling, Liu; Xinhuan, Niu; Xiaofeng, Bu; Hongbo, Li; Jiying, Tang; Shiyan, Fan

2014-01-01

367

Performance of a CCD detector using rotating anode generator for x-ray diffraction studies at ambient and high pressure conditions  

International Nuclear Information System (INIS)

Details of a two dimensional x-ray area detector developed using a charge coupled device, image intensifier and a fibre optic taper are given. The detector system is optimized for angle dispersive x-ray diffraction set up using rotating anode x-ray generator. The performance of this detector was tested by carrying out powder x-ray diffraction measurements on various materials such as intermetallics AuIn2, AuGa2, high Z material Pd and low Z scatterer adamantane (C10H16) at ambient conditions. Its utility for quick detection of phase transitions at high pressures with diamond anvil cell is demonstrated by reproducing the known pressure induced structural transitions in RbI, KI and a new structural phase transition in AuGa2 above 10 GPa. Various software have also been developed to analyse data from this detector. (author)