No abstract available

[en] High-density horizontally aligned single-walled carbon nanotubes (SWCNTs) have been grown by annealing Fe catalyst in air and optimizing catalyst thickness in the gas flow process. The aligned SWCNT density reaches >60 nanotubes per 100 μm and the length can be a few millimeters. Interestingly, the growth of aligned SWCNT arrays can be extended from the catalyst substrate to a downstream substrate across the gap between them by gas flow when the two substrates are put close to each other, and thus an aligned SWCNT array has been achieved on an isolated clean substrate.

[en] Above-boiling temperature conditions, as encountered, for example, in geothermal reservoirs and in geologic repositories for the storage of heat-producing nuclear wastes, may give rise to strongly altered liquid and gas flow processes in porous subsurface environments. The magnitude of such flow perturbation is extremely hard to measure in the field. We therefore propose a simple temperature-profile method that uses high-resolution temperature data for deriving such information. The energy that is transmitted with the vapor and water flow creates a nearly isothermal zone maintained at about the boiling temperature, referred to as a heat pipe. Characteristic features of measured temperature profiles, such as the differences in the gradients inside and outside of the heat pipe regions, are used to derive the approximate magnitude of the liquid and gas fluxes in the subsurface, for both steady-state and transient conditions

[en] The comparison of the two different approaches for simulation of the force interaction of the two- phase flow with the external surfaces is presented in the paper. The two-velocity two-phase flow model has been developed for calculation of the two-phase pressure drop for the cross flow across tube bundle. The calculated results have been compared with the experimental ones

[en] Highlights: • TMAC rather than NMAC has great influence on the flow field in circular microchannel. • The flow field is greatly influenced by the velocity stages in vicinity of the wall. • Effect of wall roughness on flow field is much greater than that of wall material. - Abstract: Effects of a gas-surface interaction model, the Cercignani-Lampise-Lord model, on primary fluid properties in a circular micro-channel are investigated in this paper. The tangential momentum accommodation coefficient (TMAC) has a significant influence on the flow field in the micro-channel. However, the variation of the flow field with the normal momentum accommodation coefficient is not as significant as that with the TMAC. The fundamental mechanism behind the change of flow field is revealed. Moreover, it is found that the effect of the wall roughness on the flow field is much greater than that of the wall material. When the wall roughness varies, the mass flux of the ring section region between the half radius and the radius changes a lot while the rest remains unchanged. However, the heat flux over the cross section remains almost unchanged with the variation of the wall material when the wall is rough.

[en] Gas-flow ionization chambers for radioisotope (RI) monitoring systems at RI institutes throughout Japan are commonly used to measure RIs which leak from the RI institutes. Before the Japan's 2011 Tohoku earthquake [11 March 2011, moment magnitude (M_w) 9.0], ionization current data measured with a gas-flow ionization chamber at the RI institute of Fukushima Medical University were found to change. The question we must raise is whether the variation ionization current can be considered to the variation of outdoor radon concentration. The conversion factors (from ionization current to radon concentration in air) of the gas-flow ionization chamber can be obtained by measuring four levels of radon concentration (outdoor air, indoor air, high level and radon-free gas) with an AlphaGUARD monitor and the chamber itself. The two gas-flow ionization chambers consist of the air intake and terminal exhaust duct of the RI institute. It was found that the radon concentration in the exhaust air was the same as that in the air intake. This study provided evidence that variations of outdoor radon concentration could be determined using gas-flow ionization chambers for RI monitoring systems. (author)

[en] The paper presents a series of mathematical models for calculating the cryogenic cycles with throttle expansion, based on energetic methods of investigation, and with applicability in industrial and laboratory cryogenic plants. In the presentation, the importance of studying the Joule-Thomson effect is underlined. The mathematical relations for calculation of the thermodynamic characteristics and the modeling of cryogenic cycles are of interest at global scale in nuclear power and in a lot of other domains. The modeling of cryogenic cycles in non-stationary conditions, and optimizing the geometry of studied flow areas, may give an important rise in the performances of cryogenic laboratories and of industrial plants too. The models proposed, based on gas dynamics studies, in concordance with the thermo-physics characteristics of the circulated gas, try to find answers to some requirements concerning the performance of the modern installations, particularly in the nuclear power field. Those methods, and the analysis of possible materials which can concur to the realization of a throttle valve, allow the designing and execution of throttle valves based on Joule-Thomson principle at cryogenic temperatures, in various conditions of pressure or flow rate, in stationary conditions as well in non-stationary conditions. (authors)

[en] Document available in extended abstract form only. The gas release from disposal system is classically described by four mechanisms i) advective-diffusive transport of gas dissolved in the pore-water, ii) visco-capillary two-phase flow, iii) dilatancy-controlled gas flow and iv) gas transport in macroscopic tensile fractures. An in situ gas experiment in the French Underground Research Laboratory (URL) is dedicated to the observation of these four mechanisms. This experiment called PGZ1 (Perturbation induced by gas) has been installed during summer 2009. Before drilling, the set-up i.e. location of the boreholes and intervals was verified by scoping calculation performed by Intera and AF-Colenco. Numerical models are used for investigating the relevant phenomena associated with two-phase flow taking into account coupled HM processes associated with dilation and fracturing. The two codes include the two-phase flow simulator TOUGH2 and the coupled two-phase geo-mechanical code GEOSIM (TAURUS Reservoir simulation Ltd.). At the start of PGZ1, the experimental layout comprised three boreholes. Two boreholes drilled from GED drift PGZ1201 and PGZ1202 (28.59 and 28.28 m respectively), are equipped with a triple packer system to monitor water/gas pressure. They are parallel at a distance closed to 1 m, inclined at 35 deg. versus horizontal. These boreholes are closed parallel to the maximal principle stress. PGZ1031, drilled from the GEX drift, is equipped with a multiple magnetic extensometers probe (MagX system^R) for observation of the axial deformation (length 23.27 m). PGZ1031 is also inclined at 48 deg. versus horizontal. This borehole crosses vertically above PGZ1201 at 2.2 m of distance. All the test sequence will be done in the interval 2 of PGZ1201. The first test phase (HYDRO1) will be performed with synthetic water and includes first a pulse test and then a constant pressure test. After the recovery period, the water will be exchanged with gas (nitrogen) at equilibrium conditions (formation pressure). The second test phase (GAS1) is composed of a series of constant flux gas injections conducted at successively higher rates and separated by recovery periods. The maximal gas pressure will be less than the fracturing pressure (near 12.3 MPa), but should reach dilation conditions. The third test phase (HYDRO2) will be performed again with synthetic water after flushing the gas at the end of GAS1. The purpose of HYDRO2 is to identify any potential change in formation permeability after the gas tests performed under expected dilation conditions (GAS1). The fourth test phase (GAS2) is planned to be similar to GAS1 but the main difference is to create a macroscopic tensile fracture. The detailed test design of GAS2 will depend on the results of GAS1. The created fracture is supposed to be seen by PGZ1031. A fifths test phase (HYDRO3) will be performed again with synthetic water at the end of GAS2 to characterize the geometrical and hydraulic properties of the newly created fracture. The whole experiment, from HYDRO1 to HYDRO3 is expected to last around 2 years. The comparison of the results obtained from HYDRO1 to HYDRO3 will give some information about the evolution of the system due to gas injection. An additional borehole, PGZ1032, nearly parallel to PGZ1031 will be drilled from the GEX drift in order to reach the gas created fracture. This borehole will be instrumented by a triple packer system with one test interval to be located on the fracture. Some gas and hydro tests will be performed in PGZ1201 to evaluate the permeability of the fracture. The subsequent sealing/healing of the fracture will be also investigated. A huge modeling activity has been planned to interpret and analysis all the results that will be obtained on PGZ1 experiment. Thereby, several groups will be involved in calculations such as AF-Colenco and Intera Inc (with TOUGH2 and GEOSIM) and also some partners within the framework of the FORGE project (Fate of Repository Gases). This European project that began in 2009 is specifically designed to tackle the key research issues associated with the generation and movement of repository gasses. (authors)

[en] The need to maximize efficiency in fuel cell applications results in the desire for minimum fuel flows. If a distribution in flow to individual cells exists, then some cells may experience fuel utilization in excess of 100%. This condition can lead to reversed polarity of the cell voltage due to an increase in anode potential. The oxidative conditions which thus occur can result in rapid degradation of a carbon supported anode catalyst layer. The catalyst and structure can be modified to reduce the rate of degradation. This approach allows for increased system flexibility and improved fuel efficiency by reducing the need for excess fuel flow and purging. Strategies to reduce degradation are focused on promoting alternative reactions to the carbon oxidation reaction. The water oxidation reaction for oxygen evolution can be preferentially promoted by improving corrosion resistance and by modifying the catalyst to reduce overpotential for water oxidation. Improved retention of water at the anode catalyst layer will ensure that it is available for the water oxidation reaction to proceed. (author)

[en] The 10 cm x 10 cm active area membrane electrode assembly (MEA) has been fabricated by adopting two routes, i.e., catalyst-coated membrane (CCM) and catalyst-coated support (CCS). In CCM method, the catalyst is directly applied on the Nafion membrane while in CCS method, catalyst is applied on support (GDL). The catalyst layer was prepared by nano-sized platinum on carbon particle, the ionomer material of the membrane and a solvent that allows the catalyst to behave like ink. The catalyst slurry was applied on the membrane, hot-pressed the sandwich of GDL and catalyst-coated Nafion membrane to form a single unit which behaves as electrodes. The primary tests regarding the efficiency of indigenously-fabricated MEAs have been carried out successfully. The performance of MEA with respect to continuous operation for long hours from the standpoint of proper functioning was also checked. A maximum power of 13 watt was obtained. (author)