Discrimination of thermal diffusivity
Bergmann Tiest, W.M.; Kappers, A.M.L.
2009-01-01
Materials such as wood or metal which are at equal temperatures are perceived to be of different ‘coldness’ due to differences in thermal properties, such as the thermal diffusivity. The thermal diffusivity of a material is a parameter that controls the rate with which heat is extracted from the
International Nuclear Information System (INIS)
Lemarechal, A.
1963-01-01
This report brings together the essential principles of thermal diffusion in the liquid and gaseous phases. The macroscopic and molecular aspects of the thermal diffusion constant are reviewed, as well as the various measurement method; the most important developments however concern the operation of the CLUSIUS and DICKEL thermo-gravitational column and its applications. (author) [fr
Thermal diffusion (1963); Diffusion thermique (1963)
Energy Technology Data Exchange (ETDEWEB)
Lemarechal, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1963-07-01
This report brings together the essential principles of thermal diffusion in the liquid and gaseous phases. The macroscopic and molecular aspects of the thermal diffusion constant are reviewed, as well as the various measurement method; the most important developments however concern the operation of the CLUSIUS and DICKEL thermo-gravitational column and its applications. (author) [French] Ce rapport rassemble les principes essentiels de la diffusion thermique en phase liquide et en phase gazeuse. Les aspects macroscopique et moleculaire de la constante de diffusion thermique sont passes en revue ainsi que ses differentes methodes de mesure; mais les developpements les plus importants concernent le fonctionnement de ls colonne thermogravitationnelle de CLUSIUS et DICKEL et ses applications. (auteur)
Thermal diffusivity effect in opto-thermal skin measurements
International Nuclear Information System (INIS)
Xiao, P; Imhof, R E; Cui, Y; Ciortea, L I; Berg, E P
2010-01-01
We present our latest study on the thermal diffusivity effect in opto-thermal skin measurements. We discuss how thermal diffusivity affects the shape of opto-thermal signal, and how to measure thermal diffusivity in opto-thermal measurements of arbitrary sample surfaces. We also present a mathematical model for a thermally gradient material, and its corresponding opto-thermal signal. Finally, we show some of our latest experimental results of this thermal diffusivity effect study.
Anisotropic Thermal Diffusivities of Plasma-Sprayed Thermal Barrier Coatings
Akoshima, Megumi; Takahashi, Satoru
2017-09-01
Thermal barrier coatings (TBCs) are used to shield the blades of gas turbines from heat and wear. There is a pressing need to evaluate the thermal conductivity of TBCs in the thermal design of advanced gas turbines with high energy efficiency. These TBCs consist of a ceramic-based top coat and a bond coat on a superalloy substrate. Usually, the focus is on the thermal conductivity in the thickness direction of the TBC because heat tends to diffuse from the surface of the top coat to the substrate. However, the in-plane thermal conductivity is also important in the thermal design of gas turbines because the temperature distribution within the turbine cannot be ignored. Accordingly, a method is developed in this study for measuring the in-plane thermal diffusivity of the top coat. Yttria-stabilized zirconia top coats are prepared by thermal spraying under different conditions. The in-plane and cross-plane thermal diffusivities of the top coats are measured by the flash method to investigate the anisotropy of thermal conduction in a TBC. It is found that the in-plane thermal diffusivity is higher than the cross-plane one for each top coat and that the top coats have significantly anisotropic thermal diffusivity. The cross-sectional and in-plane microstructures of the top coats are observed, from which their porosities are evaluated. The thermal diffusivity and its anisotropy are discussed in detail in relation to microstructure and porosity.
Gas phase thermal diffusion of stable isotopes
International Nuclear Information System (INIS)
Eck, C.F.
1979-01-01
The separation of stable isotopes at Mound Facility is reviewed from a historical perspective. The historical development of thermal diffusion from a laboratory process to a separation facility that handles all the noble gases is described. In addition, elementary thermal diffusion theory and elementary cascade theory are presented along with a brief review of the uses of stable isotopes
Stable isotope separation by thermal diffusion
International Nuclear Information System (INIS)
Vasaru, Gheorghe
2001-01-01
Thermal diffusion in both gaseous and liquid phase has been subject of extensive experimental and theoretical investigations, especially after the invention of K. Clusius and G. Dickel of the thermal diffusion column, sixty three years ago. This paper gives a brief overview of the most important research and developments performed during the time at the National Institute for Research and Development for Isotopic and Molecular Technology (ITIM) at Cluj - Napoca, Romania in the field of separation of stable isotopes by thermal diffusion. An retrospective analysis of the research and results concerning isotope separation by thermal diffusion entails the following conclusions: - thermal diffusion is an adequate method for hydrogen isotope separation (deuterium and tritium) and for noble gas isotope separation (He, Ne, Ar, Kr, Xe); - thermal diffusion is attractive also for 13 C enrichment using methane as raw material for separation, when annual yields of up to 100 g are envisaged; - lately, the thermal diffusion appears to be chosen as a final enrichment step for 17 O. An obvious advantage of this method is its non-specificity, i.e. the implied equipment can be utilized for isotope separation of other chemical elements too. Having in view the low investment costs for thermal diffusion cascades the method appears economically attractive for obtaining low-scale, laboratory isotope production. The paper has the following content: 1. The principle of method; 2. The method's application; 3. Research in the field of thermal diffusion at ITIM; 4. Thermal diffusion cascades for N, C, Ne, Ar and Kr isotope separation; 5. Conclusion
Thermal Diffusivity Measurements in Edible Oils using Transient Thermal Lens
Valdez, R. Carbajal.; Pérez, J. L. Jiménez.; Cruz-Orea, A.; Martín-Martínez, E. San.
2006-11-01
Time resolved thermal lens (TL) spectrometry is applied to the study of the thermal diffusivity of edible oils such as olive, and refined and thermally treated avocado oils. A two laser mismatched-mode experimental configuration was used, with a He Ne laser as a probe beam and an Ar+ laser as the excitation one. The characteristic time constant of the transient thermal lens was obtained by fitting the experimental data to the theoretical expression for a transient thermal lens. The results showed that virgin olive oil has a higher thermal diffusivity than for refined and thermally treated avocado oils. This measured thermal property may contribute to a better understanding of the quality of edible oils, which is very important in the food industry. The thermal diffusivity results for virgin olive oil, obtained from this technique, agree with those reported in the literature.
Thermal diffusion and separation of isotopes
International Nuclear Information System (INIS)
Fournier, Andre
1944-01-01
After a review of the various processes used to separate isotopes or at least to obtain mixes with a composition different from the natural proportion, this research addresses the use of thermal diffusion. The author reports a theoretical study of gas thermal diffusion and of the Clusius-Dickel method. In the second part, he reports the enrichment of methane with carbon-13, and of ammoniac with nitrogen-15. The next part reports the experimental study of thermal diffusion of liquids and solutions, and the enrichment of carbon tetra-chloride with chlorine-37. The author then proposes an overview of theories of thermal diffusion in liquid phase (hydrodynamic theory, kinetic theory, theory of caged molecules)
Ballistic and Diffusive Thermal Conductivity of Graphene
Saito, Riichiro; Masashi, Mizuno; Dresselhaus, Mildred S.
2018-02-01
This paper is a contribution to the Physical Review Applied collection in memory of Mildred S. Dresselhaus. Phonon-related thermal conductivity of graphene is calculated as a function of the temperature and sample size of graphene in which the crossover of ballistic and diffusive thermal conductivity occurs at around 100 K. The diffusive thermal conductivity of graphene is evaluated by calculating the phonon mean free path for each phonon mode in which the anharmonicity of a phonon and the phonon scattering by a 13C isotope are taken into account. We show that phonon-phonon scattering of out-of-plane acoustic phonon by the anharmonic potential is essential for the largest thermal conductivity. Using the calculated results, we can design the optimum sample size, which gives the largest thermal conductivity at a given temperature for applying thermal conducting devices.
Thermal diffusion of chlorine in uranium dioxide
International Nuclear Information System (INIS)
Pipon, Y.; Toulhoat, N.; Moncoffre, N.; Jaffrezic, H.; Gavarini, S.; Martin, P.; Raimbault, L.; Scheidegger, A.M.
2006-01-01
In a nuclear reactor, isotopes such as 35 Cl present as impurities in the nuclear fuel are activated by thermal neutron capture. During interim storage or geological disposal of nuclear fuel, the activation products such as 36 Cl may be released from the fuel to the geo/biosphere and contribute to the ''instant release fraction'' as they are likely to migrate in defects and grain boundaries. In order to differentiate diffusion mechanisms due to ''athermal'' processes during irradiation from thermally activated diffusion, both irradiation and thermal effects must be assessed. This work concerns the measurement of the thermal diffusion coefficient of chlorine in UO 2 . 37 Cl was implanted at a 10 13 at/cm 2 fluence in depleted UO 2 samples which were then annealed in the 900-1200 C temperature range and finally analyzed by secondary ion mass spectrometry (SIMS) to obtain 37 Cl depth profiles. The migration process appears to be rather complex, involving mechanisms such as atomic, grain boundary, directed diffusion along preferential patterns as well as trapping into sinks before successive effusion. However, using a diffusion model based on general equation of transport, apparent diffusion coefficients could be calculated for 1000 and 1100 C and a mean activation energy of 4.3 eV is proposed. This value is one of the lowest values compared to those found in literature for other radionuclides pointing out a great ability of chlorine to migrate in UO 2 at relatively low temperatures. In order to unequivocally determine the diffusion behaviour of both implanted and pristine chlorine before and after thermal annealing, the structural environment of chlorine in UO 2 was examined using micro X-ray fluorescence (micro-XRF) and micro X-ray absorption spectroscopy (micro-XAS). (orig.)
Thermal Diffusivity in Bone and Hydroxyapatite
Calderón, A.; Peña Rodríguez, G.; Muñoz Hernández, R. A.; Díaz Gongora, J. A. I.; Mejia Barradas, C. M.
2004-09-01
We report thermal diffusivity measurements in bull bone and commercial hydroxyapatite (HA), both in powder form, in order to determinate the thermal compatibility between these materials. Besides this, we report a comparison between these measured values and those of metallic samples frequently used in implants, as high purity titanium and stainless steel. Our results show a good thermal compatibility (74%) between HA and bone, both in powder form. Finally, it was obtained a one order of magnitude difference between the thermal diffusivity values of metallic samples and those corresponding values to bone and HA being this difference greater in titanium than in stainless steel, which is important to consider in some biomedical and dental applications.
Thermal neutron diffusion parameters in homogeneous mixtures
Energy Technology Data Exchange (ETDEWEB)
Drozdowicz, K.; Krynicka, E. [Institute of Nuclear Physics, Cracow (Poland)
1995-12-31
A physical background is presented for a computer program which calculates the thermal neutron diffusion parameters for homogeneous mixtures of any compounds. The macroscopic absorption, scattering and transport cross section of the mixture are defined which are generally function of the incident neutron energy. The energy-averaged neutron parameters are available when these energy dependences and the thermal neutron energy distribution are assumed. Then the averaged diffusion coefficient and the pulsed thermal neutron parameters (the absorption rare and the diffusion constant) are also defined. The absorption cross section is described by the 1/v law and deviations from this behaviour are considered. The scattering cross section can be assumed as being almost constant in the thermal neutron region (which results from the free gas model). Serious deviations are observed for hydrogen atoms bound in molecules and a special study in the paper is devoted to this problem. A certain effective scattering cross section is found in this case on a base of individual exact data for a few hydrogenous media. Approximations assumed for the average cosine of the scattering angle are also discussed. The macroscopic parameters calculated are averaged over the Maxwellian energy distribution for the thermal neutron flux. An information on the input data for the computer program is included. (author). 10 refs, 4 figs, 5 tabs.
Thermal neutron diffusion parameters in homogeneous mixtures
International Nuclear Information System (INIS)
Drozdowicz, K.; Krynicka, E.
1995-01-01
A physical background is presented for a computer program which calculates the thermal neutron diffusion parameters for homogeneous mixtures of any compounds. The macroscopic absorption, scattering and transport cross section of the mixture are defined which are generally function of the incident neutron energy. The energy-averaged neutron parameters are available when these energy dependences and the thermal neutron energy distribution are assumed. Then the averaged diffusion coefficient and the pulsed thermal neutron parameters (the absorption rare and the diffusion constant) are also defined. The absorption cross section is described by the 1/v law and deviations from this behaviour are considered. The scattering cross section can be assumed as being almost constant in the thermal neutron region (which results from the free gas model). Serious deviations are observed for hydrogen atoms bound in molecules and a special study in the paper is devoted to this problem. A certain effective scattering cross section is found in this case on a base of individual exact data for a few hydrogenous media. Approximations assumed for the average cosine of the scattering angle are also discussed. The macroscopic parameters calculated are averaged over the Maxwellian energy distribution for the thermal neutron flux. An information on the input data for the computer program is included. (author). 10 refs, 4 figs, 5 tabs
Liquid Thermal Diffusion during the Manhattan Project
Cameron Reed, B.
2011-06-01
On the basis of Manhattan Engineer District documents, a little known Naval Research Laboratory report of 1946, and other sources, I construct a more complete history of the liquid-thermal-diffusion method of uranium enrichment during World War II than is presented in official histories of the Manhattan Project. This method was developed by Philip Abelson (1913-2004) and put into operation at the rapidly-constructed S-50 plant at Oak Ridge, Tennessee, which was responsible for the first stage of uranium enrichment, from 0.72% to 0.85% U-235, producing nearly 45,000 pounds of enriched U-235 by July 1945 at a cost of just under 20 million. I review the history, design, politics, construction, and operation of the S-50 liquid-thermal-diffusion plant.
Thermal diffusivity of diamond films using a laser pulse technique
International Nuclear Information System (INIS)
Albin, S.; Winfree, W.P.; Crews, B.S.
1990-01-01
Polycrystalline diamond films were deposited using a microwave plasma-enhanced chemical vapor deposition process. A laser pulse technique was developed to measure the thermal diffusivity of diamond films deposited on a silicon substrate. The effective thermal diffusivity of a diamond film on silicon was measured by observing the phase and amplitude of the cyclic thermal waves generated by laser pulses. An analytical model is presented to calculate the effective inplane (face-parallel) diffusivity of a two-layer system. The model is used to reduce the effective thermal diffusivity of the diamond/silicon sample to a value for the thermal diffusivity and conductivity of the diamond film
Apparatus for diffusion-gap thermal desalination
Lowenstein, Andrew
2017-09-26
A thermal distillation apparatus including evaporation surfaces that are wetted with a solution, and from which at least some of the volatile solvent contained in the solution evaporates, condensers having an external surface in close proximity to, but not touching, a corresponding one of the one or more evaporation surfaces, and on which vapors of the solvent condense, releasing thermal energy that heats a flow of the solution moving upward within the condensers, spacers that prevent contact between the evaporating surfaces and the condensers, wherein spaces between the evaporating surfaces and the condensers are filled with a gaseous mixture composed of solvent vapor and one or more non-condensable gases, and except for diffusion of the solvent vapor relative to the non-condensable gases, the gaseous mixture is stationary.
Thermal diffusivity imaging with the thermal lens microscope.
Dada, Oluwatosin O; Feist, Peter E; Dovichi, Norman J
2011-12-01
A coaxial thermal lens microscope was used to generate images based on both the absorbance and thermal diffusivity of histological samples. A pump beam was modulated at frequencies ranging from 50 kHz to 5 MHz using an acousto-optic modulator. The pump and a CW probe beam were combined with a dichroic mirror, directed into an inverted microscope, and focused onto the specimen. The change in the transmitted probe beam's center intensity was detected with a photodiode. The photodiode's signal and a reference signal from the modulator were sent to a high-speed lock-in amplifier. The in-phase and quadrature signals were recorded as a sample was translated through the focused beams and used to generate images based on the amplitude and phase of the lock-in amplifier's signal. The amplitude is related to the absorbance and the phase is related to the thermal diffusivity of the sample. Thin sections of stained liver and bone tissues were imaged; the contrast and signal-to-noise ratio of the phase image was highest at frequencies from 0.1-1 MHz and dropped at higher frequencies. The spatial resolution was 2.5 μm for both amplitude and phase images, limited by the pump beam spot size. © 2011 Optical Society of America
Thermal diffuse scattering in transmission electron microscopy
Energy Technology Data Exchange (ETDEWEB)
Forbes, B.D.; D' Alfonso, A.J. [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Findlay, S.D. [School of Physics, Monash University, Victoria 3800 (Australia); Van Dyck, D. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); LeBeau, J.M. [North Carolina State University, Raleigh, NC 27695-7907 (United States); Stemmer, S. [Materials Department, University of California, Santa Barbara, CA 93106-5050 (United States); Allen, L.J., E-mail: lja@unimelb.edu.au [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia)
2011-12-15
In conventional transmission electron microscopy, thermal scattering significantly affects the image contrast. It has been suggested that not accounting for this correctly is the main cause of the Stobbs factor, the ubiquitous, large contrast mismatch found between theory and experiment. In the case where a hard aperture is applied, we show that previous conclusions drawn from work using bright field scanning transmission electron microscopy and invoking the principle of reciprocity are reliable in the presence of thermal scattering. In the aperture-free case it has been suggested that even the most sophisticated mathematical models for thermal diffuse scattering lack in their numerical implementation, specifically that there may be issues in sampling, including that of the contrast transfer function of the objective lens. We show that these concerns can be satisfactorily overcome with modest computing resources; thermal scattering can be modelled accurately enough for the purpose of making quantitative comparison between simulation and experiment. Spatial incoherence of the source is also investigated. Neglect or inadequate handling of thermal scattering in simulation can have an appreciable effect on the predicted contrast and can be a significant contribution to the Stobbs factor problem. -- Highlights: Black-Right-Pointing-Pointer We determine the numerical requirements for accurate simulation of TDS in CTEM. Black-Right-Pointing-Pointer TDS can be simulated to high precision using the Born-Oppenheimer model. Black-Right-Pointing-Pointer Such calculations establish the contribution of TDS to the Stobbs factor problem. Black-Right-Pointing-Pointer Treating spatial incoherence using envelope functions increases image contrast. Black-Right-Pointing-Pointer Rigorous treatment of spatial incoherence significantly reduces image contrast.
Stable isotope enrichment by thermal diffusion
International Nuclear Information System (INIS)
Vasaru, Gheorghe
2003-01-01
Thermal diffusion (TD) in both gaseous and liquid phase has been the subject of extensive experimental and theoretical investigations, especially after the invention by K. Clusius and G. Dickel of the thermal diffusion column, sixty years ago. This paper gives a brief overview of the most important applications and developments of this transport phenomenon for enrichment of 13 C and of some noble gases isotopes in our institute. The results of calculations of the transport coefficients H and K for a concentric tube type TD column, operated with methane as process gas, are presented. Static separation factor at equilibrium vs gas pressure has been calculated for various molecular models. The experimental separation factors for different gas pressure were found to be consistent with those calculated for the inverse power repulsion model and the Lennard-Jones model. The most important characteristics of a seven-stage cascade consisting of 19 TD columns of concentric tube type are given. This system has been constructed and successfully operated at a temperature of 673 K and produces an enrichment of methane of natural isotopic 13 C abundance, up to the concentration of 25% 13 CH 4 . Enrichment of the noble gases isotopes implies: - a . Enrichment of 20 Ne and 22 Ne in a eight-stage cascade consisting of 8 TD columns; - b. enrichment of 46 Ar in a seven-stage cascade consisting of TD columns and finally; - c. enrichment of 78 Kr and 86 Kr in a fifteen-stage cascade, consisting of 35 TD columns. For all these installations we have adopted TD columns of hot wire type (4 m in length), operated at a temperature of 1073 K. (author)
Carson, James K.
2018-06-01
Glass spheres are often used as filler materials for composites. Comparatively few articles in the literature have been devoted to the measurement or modelling of thermal properties of composites containing glass spheres, and there does not appear to be any reported data on the measurement of thermal diffusivities over a range of filler volume fractions. In this study, the thermal diffusivities of guar-gel/glass sphere composites were measured using a transient comparative method. The addition of the glass beads to the gel increased the thermal diffusivity of the composite, more than doubling the thermal diffusivity of the composite relative to the diffusivity of the gel at the maximum glass volume fraction of approximately 0.57. Thermal conductivities of the composites were derived from the thermal diffusivity measurements, measured densities and estimated specific heat capacities of the composites. Two approaches to modelling the effective thermal diffusivity were considered.
Thermal diffusivity of felsic to mafic granulites at elevated temperatures
Ray, Labani; Förster, H.-J.; Schilling, F. R.; Förster, A.
2006-11-01
The thermal diffusivity of felsic and intermediate granulites (charnockites, enderbites), mafic granulites, and amphibolite-facies gneisses has been measured up to temperatures of 550 °C using a transient technique. The rock samples are from the Archean and Pan-African terranes of the Southern Indian Granulite Province. Thermal diffusivity at room temperature ( DRT) for different rock types ranges between 1.2 and 2.2 mm 2 s - 1 . For most of the rocks, the effect of radiative heat transfer is observed at temperatures above 450 °C. However, for few enderbites and mafic granulites, radiative heat transfer is negligible up to 550 °C. In the temperature range of conductive heat transfer, i.e., between 20 ° and 450 °C, thermal diffusivity decreases between 35% and 45% with increasing temperature. The temperature dependence of the thermal diffusivity is directly correlated with the thermal diffusivity at room temperature, i.e., the higher the thermal diffusivity at room temperature, DRT, the greater is its temperature dependence. In this temperature range i.e., between 20 and 450 °C, thermal diffusivity can be expressed as D = 0.7 mm 2 s -1 + 144 K ( DRT - 0.7 mm 2 s -1 ) / ( T - 150 K), where T is the absolute temperature in Kelvin. At higher temperatures, an additional radiative contribution is observed according to CT3, where C varies from 10 - 9 to 10 - 10 depending on intrinsic rock properties (opacity, absorption behavior, grain size, grain boundary, etc). An equation is presented that describes the temperature and pressure dependence thermal diffusivity of rocks based only on the room-temperature thermal diffusivity. Room-temperature thermal diffusivity and its temperature dependence are mainly dependent on the major mineralogy of the rock. Because granulites are important components of the middle and lower continental crust, the results of this study provide important constraints in quantifying more accurately the thermal state of the deeper continental
New acrylic resin composite with improved thermal diffusivity.
Messersmith, P B; Obrez, A; Lindberg, S
1998-03-01
Studies have shown that physical characteristics of denture base materials may affect patient acceptance of denture prostheses by altering sensory experience of food during mastication. Thermal diffusivity is one material property that has been cited as being important in determining gustatory response, with denture base acrylic resins having low thermal diffusivity compared with denture base metal alloys. This study prepared and characterized experimental acrylic resin composite material with increased thermal diffusivity. Sapphire (Al2O3) whiskers were added to conventional denture base acrylic resin during processing to achieve loadings of 9.35% and 15% by volume. Cylindrical test specimens containing an embedded thermocouple were used to determine thermal diffusivity over a physiologic temperature range (0 degree to 70 degrees C). Thermal diffusivities of the sapphire containing composites were found to be significantly higher than the unmodified acrylic resin. Thermal diffusivity was found to increase in proportion to the volume percentage of sapphire filler, which suggested that the high aspect ratio ceramic particles formed a pathway for heat conduction through the insulating polymer matrix. The thermal diffusivity of denture base acrylic resin was increased by the addition of thermally conducting sapphire whiskers.
Thermal diffusivity of samarium-gadolinium zirconate solid solutions
International Nuclear Information System (INIS)
Pan, W.; Wan, C.L.; Xu, Q.; Wang, J.D.; Qu, Z.X.
2007-01-01
We synthesized samarium-gadolinium zirconate solid solutions and determined their thermal diffusivities, Young's moduli and thermal expansion coefficients, which are very important for their application in thermal barrier coatings. Samarium-gadolinium zirconate solid solutions have extremely low thermal diffusivity between 20 and 600 deg. C. The solid solutions have lower Young's moduli and higher thermal expansion coefficients than those of pure samarium and gadolinium zirconates. This combination of characteristics is promising for the application of samarium and gadolinium zirconates in gas turbines. The mechanism of phonon scattering by point defects is discussed
Thermal diffusion in dilute nanofluids investigated by photothermal interferometry
International Nuclear Information System (INIS)
Philip, J; Nisha, M R
2010-01-01
We have carried out a theoretical analysis of the dependence of the particle mass fraction on the thermal diffusivity of dilute suspensions of nanoparticles in liquids (dilute nanofluids). The analysis takes in to account adsorption of an ordered layer of solvent molecules around the nanoparticles. It is found that thermal diffusivity decreases with mass fraction for sufficiently small particle sizes. Beyond a critical particle size thermal diffusivity begins to increase with mass fraction for the same system. The results have been verified experimentally by measuring the thermal diffusivity of dilute suspensions of TiO 2 nanoparticles dispersed in polyvinyl alcohol (PVA) medium. The effect is attributed to Kapitza resistance of thermal waves in the medium.
Computational Analysis on Performance of Thermal Energy Storage (TES) Diffuser
Adib, M. A. H. M.; Adnan, F.; Ismail, A. R.; Kardigama, K.; Salaam, H. A.; Ahmad, Z.; Johari, N. H.; Anuar, Z.; Azmi, N. S. N.
2012-09-01
Application of thermal energy storage (TES) system reduces cost and energy consumption. The performance of the overall operation is affected by diffuser design. In this study, computational analysis is used to determine the thermocline thickness. Three dimensional simulations with different tank height-to-diameter ratio (HD), diffuser opening and the effect of difference number of diffuser holes are investigated. Medium HD tanks simulations with double ring octagonal diffuser show good thermocline behavior and clear distinction between warm and cold water. The result show, the best performance of thermocline thickness during 50% time charging occur in medium tank with height-to-diameter ratio of 4.0 and double ring octagonal diffuser with 48 holes (9mm opening ~ 60%) acceptable compared to diffuser with 6mm ~ 40% and 12mm ~ 80% opening. The conclusion is computational analysis method are very useful in the study on performance of thermal energy storage (TES).
Computational Analysis on Performance of Thermal Energy Storage (TES) Diffuser
International Nuclear Information System (INIS)
Adib, M A H M; Ismail, A R; Kardigama, K; Salaam, H A; Ahmad, Z; Johari, N H; Anuar, Z; Azmi, N S N; Adnan, F
2012-01-01
Application of thermal energy storage (TES) system reduces cost and energy consumption. The performance of the overall operation is affected by diffuser design. In this study, computational analysis is used to determine the thermocline thickness. Three dimensional simulations with different tank height-to-diameter ratio (HD), diffuser opening and the effect of difference number of diffuser holes are investigated. Medium HD tanks simulations with double ring octagonal diffuser show good thermocline behavior and clear distinction between warm and cold water. The result show, the best performance of thermocline thickness during 50% time charging occur in medium tank with height-to-diameter ratio of 4.0 and double ring octagonal diffuser with 48 holes (9mm opening ∼ 60%) acceptable compared to diffuser with 6mm ∼ 40% and 12mm ∼ 80% opening. The conclusion is computational analysis method are very useful in the study on performance of thermal energy storage (TES).
Periodic heat wave determination of thermal diffusivity of clays ...
African Journals Online (AJOL)
The responses of Ankaful, Tetegu (# 1 & 2) and Mamfe clays to periodic heat waves were analyzed to deter-mine the thermal diffusivity values. The temperature amplitude attenuated with depth of penetration, while the phase shift increased. The thermal diffusivity values ranged from 3.0 - 9.5 x 10P-7P mP2P/s by amplitude ...
Parallel diffusion length on thermal neutrons in rod type lattices
International Nuclear Information System (INIS)
Ahmed, T.; Siddiqui, S.A.M.M.; Khan, A.M.
1981-11-01
Calculation of diffusion lengths of thermal neutrons in lead-water and aluminum water lattices in direction parallel to the rods are performed using one group diffusion equation together with Shevelev transport correction. The formalism is then applied to two practical cases, the Kawasaki (Hitachi) and the Douglas point (Candu) reactor lattices. Our results are in good agreement with the observed values. (author)
Manipulation of heat-diffusion channel in laser thermal lithography.
Wei, Jingsong; Wang, Yang; Wu, Yiqun
2014-12-29
Laser thermal lithography is a good alternative method for forming small pattern feature size by taking advantage of the structural-change threshold effect of thermal lithography materials. In this work, the heat-diffusion channels of laser thermal lithography are first analyzed, and then we propose to manipulate the heat-diffusion channels by inserting thermal conduction layers in between channels. Heat-flow direction can be changed from the in-plane to the out-of-plane of the thermal lithography layer, which causes the size of the structural-change threshold region to become much smaller than the focused laser spot itself; thus, nanoscale marks can be obtained. Samples designated as "glass substrate/thermal conduction layer/thermal lithography layer (100 nm)/thermal conduction layer" are designed and prepared. Chalcogenide phase-change materials are used as thermal lithography layer, and Si is used as thermal conduction layer to manipulate heat-diffusion channels. Laser thermal lithography experiments are conducted on a home-made high-speed rotation direct laser writing setup with 488 nm laser wavelength and 0.90 numerical aperture of converging lens. The writing marks with 50-60 nm size are successfully obtained. The mark size is only about 1/13 of the focused laser spot, which is far smaller than that of the light diffraction limit spot of the direct laser writing setup. This work is useful for nanoscale fabrication and lithography by exploiting the far-field focusing light system.
Accurate photopyroelectric measurements of thermal diffusivity of (semi)liquids
Dadarlat, D.; Neamtu, C.; Surducan, E.; Sahraoui, A.H.; Longuemart, S.; Bicanic, D.
2002-01-01
The back photopyroelectric (PPE) configuration, with opaque sample and thermally thick sample and sensor, was applied in order to obtain room temperature values of the thermal diffusivity of some (semi)liquid materials. The methodology is based on a sample's thickness scan, and not on a frequency
Characterization and modeling of thermal diffusion and aggregation in nanofluids.
Energy Technology Data Exchange (ETDEWEB)
Gharagozloo, Patricia E.; Goodson, Kenneth E. (Stanford University, Stanford, CA)
2010-05-01
Fluids with higher thermal conductivities are sought for fluidic cooling systems in applications including microprocessors and high-power lasers. By adding high thermal conductivity nanoscale metal and metal oxide particles to a fluid the thermal conductivity of the fluid is enhanced. While particle aggregates play a central role in recent models for the thermal conductivity of nanofluids, the effect of particle diffusion in a temperature field on the aggregation and transport has yet to be studied in depth. The present work separates the effects of particle aggregation and diffusion using parallel plate experiments, infrared microscopy, light scattering, Monte Carlo simulations, and rate equations for particle and heat transport in a well dispersed nanofluid. Experimental data show non-uniform temporal increases in thermal conductivity above effective medium theory and can be well described through simulation of the combination of particle aggregation and diffusion. The simulation shows large concentration distributions due to thermal diffusion causing variations in aggregation, thermal conductivity and viscosity. Static light scattering shows aggregates form more quickly at higher concentrations and temperatures, which explains the increased enhancement with temperature reported by other research groups. The permanent aggregates in the nanofluid are found to have a fractal dimension of 2.4 and the aggregate formations that grow over time are found to have a fractal dimension of 1.8, which is consistent with diffusion limited aggregation. Calculations show as aggregates grow the viscosity increases at a faster rate than thermal conductivity making the highly aggregated nanofluids unfavorable, especially at the low fractal dimension of 1.8. An optimum nanoparticle diameter for these particular fluid properties is calculated to be 130 nm to optimize the fluid stability by reducing settling, thermal diffusion and aggregation.
Thermal diffusion and separation of isotopes; Diffusion thermique et separation d'isotopes
Energy Technology Data Exchange (ETDEWEB)
Fournier, Andre
1944-03-30
After a review of the various processes used to separate isotopes or at least to obtain mixes with a composition different from the natural proportion, this research addresses the use of thermal diffusion. The author reports a theoretical study of gas thermal diffusion and of the Clusius-Dickel method. In the second part, he reports the enrichment of methane with carbon-13, and of ammoniac with nitrogen-15. The next part reports the experimental study of thermal diffusion of liquids and solutions, and the enrichment of carbon tetra-chloride with chlorine-37. The author then proposes an overview of theories of thermal diffusion in liquid phase (hydrodynamic theory, kinetic theory, theory of caged molecules)
Water cooling thermal power measurement in a vacuum diffusion pump
Directory of Open Access Journals (Sweden)
Luís Henrique Cardozo Amorin
2012-04-01
Full Text Available Diffusion vacuum pumps are used both in industry and in laboratory science for high vacuum production. For its operation they must be refrigerated, and it is done by circulating water in open circuit. Considering that, vacuum systems stays operating by hours, the water consumption may be avoided if the diffusion vacuum pumps refrigeration were done in closed circuit. However, it is necessary to know the diffusion vacuum pump thermal power (the heat transferred to circulate water by time units to implement one of these and get in the refrigeration system dimension. In this paper the diffusion vacuum pump thermal power was obtained by measuring water flow and temperature variation and was calculated through the heat quantity variation equation time function. The thermal power value was 935,6 W, that is 397 W smaller and 35 W bigger than, respectively, the maximum and minimum diffusion pump thermal power suggested by its operation manual. This procedure have been shown useful to precisely determine the diffusion pump thermal power or of any other system that needs to be refrigerated in water closed circuit.
Akoshima, Megumi; Tanaka, Takashi; Endo, Satoshi; Baba, Tetsuya; Harada, Yoshio; Kojima, Yoshitaka; Kawasaki, Akira; Ono, Fumio
2011-11-01
Ceramic-based thermal barrier coatings are used as heat and wear shields of gas turbine blades. There is a strong need to evaluate the thermal conductivity of coating for thermal design and use. The thermal conductivity of a bulk material is obtained as the product of thermal diffusivity, specific heat capacity, and density above room temperature in many cases. Thermal diffusivity and thermal conductivity are unique for a given material because they are sensitive to the structure of the material. Therefore, it is important to measure them in each sample. However it is difficult to measure the thermal diffusivity and thermal conductivity of coatings because coatings are attached to substrates. In order to evaluate the thermal diffusivity of a coating attached to the substrate, we have examined the laser flash method with the multilayer model on the basis of the response function method. We carried out laser flash measurements in layered samples composed of a CoNiCrAlY bond coating and a 8YSZ top coating by thermal spraying on a Ni-based superalloy substrate. It was found that the procedure using laser flash method with the multilayer model is useful for the thermal diffusivity evaluation of a coating attached to a substrate.
Thermal diffusivity measurement by lock-in photothermal shadowgraph method
Energy Technology Data Exchange (ETDEWEB)
Cifuentes, A. [Instituto Politécnico Nacional, Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Ciudad de México 11500 (Mexico); Departamento de Física Aplicada I, Escuela Técnica Superior de Ingeniería, Universidad del País Vasco UPV/EHU, Alameda Urquijo s/n, 48013 Bilbao (Spain); Alvarado, S. [Instituto Politécnico Nacional, Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Ciudad de México 11500 (Mexico); Laboratory for Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, Heverlee B-3001 (Belgium); Cabrera, H. [Centro Multidisciplinario de Ciencias, Instituto Venezolano de Investigaciones Científicas, IVIC, Mérida 5101, Venezuela and SPIE-ICTP Anchor Research in Optics Program Lab, International Centre for Theoretical Physics (ICTP), Strada Costiera 11, Trieste (Italy); Calderón, A.; Marín, E., E-mail: emarinm@ipn.mx [Instituto Politécnico Nacional, Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Ciudad de México 11500 (Mexico)
2016-04-28
Here, we present a novel application of the shadowgraph technique for obtaining the thermal diffusivity of an opaque solid sample, inspired by the orthogonal skimming photothermal beam deflection technique. This new variant utilizes the shadow projected by the sample when put against a collimated light source. The sample is then heated periodically by another light beam, giving rise to thermal waves, which propagate across it and through its surroundings. Changes in the refractive index of the surrounding media due to the heating distort the shadow. This phenomenon is recorded and lock-in amplified in order to determine the sample's thermal diffusivity.
Viscosity, thermal diffusivity and Prandtl number of nanoparticle suspensions
Institute of Scientific and Technical Information of China (English)
WANG Buxuan; ZHOU Leping; PENG Xiaofeng
2004-01-01
Using our reported experimental data of effective thermal conductivity, specific heat capacity and viscosity for CuO nanoparticle suspensions, the corresponding thermal diffusivity and Prandtl number are calculated. With the hard sphere model and considering effects of particle clustering and surface adsorption, the increase of viscosity for nanoparticle suspension observed is explained. It is shown that the effective thermal conductivity will be strongly affected by the formation and correlated spatial distribution of nanoparticle clusters when compared to viscosity in hosting liquid.
Fourier diffraction theorem for diffusion-based thermal tomography
International Nuclear Information System (INIS)
Baddour, Natalie
2006-01-01
There has been much recent interest in thermal imaging as a method of non-destructive testing and for non-invasive medical imaging. The basic idea of applying heat or cold to an area and observing the resulting temperature change with an infrared camera has led to the development of rapid and relatively inexpensive inspection systems. However, the main drawback to date has been that such an approach provides mainly qualitative results. In order to advance the quantitative results that are possible via thermal imaging, there is interest in applying techniques and algorithms from conventional tomography. Many tomography algorithms are based on the Fourier diffraction theorem, which is inapplicable to thermal imaging without suitable modification to account for the attenuative nature of thermal waves. In this paper, the Fourier diffraction theorem for thermal tomography is derived and discussed. The intent is for this thermal-diffusion based Fourier diffraction theorem to form the basis of tomographic reconstruction algorithms for quantitative thermal imaging
Measurement of thermal diffusivity of depleted uranium metal microspheres
Humrickhouse-Helmreich, Carissa J.; Corbin, Rob; McDeavitt, Sean M.
2014-03-01
The high void space of nuclear fuels composed of homogeneous uranium metal microspheres may allow them to achieve ultra-high burnup by accommodating fuel swelling and reducing fuel/cladding interactions; however, the relatively low thermal conductivity of microsphere nuclear fuels may limit their application. To support the development of microsphere nuclear fuels, an apparatus was designed in a glovebox and used to measure the apparent thermal diffusivity of a packed bed of depleted uranium (DU) microspheres with argon fill in the void spaces. The developed Crucible Heater Test Assembly (CHTA) recorded radial temperature changes due to an initial heat pulse from a central thin-diameter cartridge heater. Using thermocouple positions and time-temperature data, the apparent thermal diffusivity was calculated. The thermal conductivity of the DU microspheres was calculated based on the thermal diffusivity from the CHTA, known material densities and specific heat capacities, and an assumed 70% packing density based on prior measurements. Results indicate that DU metal microspheres have very low thermal conductivity, relative to solid uranium metal, and rapidly form an oxidation layer even in a low oxygen environment. At 500 °C, the thermal conductivity of the DU metal microsphere bed was 0.431 ± 0.0560 W/m-K compared to the literature value of approximately 32 W/m-K for solid uranium metal.
Measurement of thermal diffusivity of depleted uranium metal microspheres
Energy Technology Data Exchange (ETDEWEB)
Humrickhouse-Helmreich, Carissa J., E-mail: carissahelmreich@tamu.edu [Texas A and M University, Department of Nuclear Engineering, 337 Zachry Engineering Center, 3133 TAMU, College Station, TX 77843 (United States); Corbin, Rob, E-mail: rcorbin@terrapower.com [TerraPower, LLC, 330 120th Ave NE, Suite 100, Bellevue, WA 98005 (United States); McDeavitt, Sean M., E-mail: mcdeavitt@tamu.edu [Texas A and M University, Department of Nuclear Engineering, 337 Zachry Engineering Center, 3133 TAMU, College Station, TX 77843 (United States)
2014-03-15
The high void space of nuclear fuels composed of homogeneous uranium metal microspheres may allow them to achieve ultra-high burnup by accommodating fuel swelling and reducing fuel/cladding interactions; however, the relatively low thermal conductivity of microsphere nuclear fuels may limit their application. To support the development of microsphere nuclear fuels, an apparatus was designed in a glovebox and used to measure the apparent thermal diffusivity of a packed bed of depleted uranium (DU) microspheres with argon fill in the void spaces. The developed Crucible Heater Test Assembly (CHTA) recorded radial temperature changes due to an initial heat pulse from a central thin-diameter cartridge heater. Using thermocouple positions and time–temperature data, the apparent thermal diffusivity was calculated. The thermal conductivity of the DU microspheres was calculated based on the thermal diffusivity from the CHTA, known material densities and specific heat capacities, and an assumed 70% packing density based on prior measurements. Results indicate that DU metal microspheres have very low thermal conductivity, relative to solid uranium metal, and rapidly form an oxidation layer even in a low oxygen environment. At 500 °C, the thermal conductivity of the DU metal microsphere bed was 0.431 ± 0.0560 W/m-K compared to the literature value of approximately 32 W/m-K for solid uranium metal.
Measurement of thermal diffusivity of depleted uranium metal microspheres
International Nuclear Information System (INIS)
Humrickhouse-Helmreich, Carissa J.; Corbin, Rob; McDeavitt, Sean M.
2014-01-01
The high void space of nuclear fuels composed of homogeneous uranium metal microspheres may allow them to achieve ultra-high burnup by accommodating fuel swelling and reducing fuel/cladding interactions; however, the relatively low thermal conductivity of microsphere nuclear fuels may limit their application. To support the development of microsphere nuclear fuels, an apparatus was designed in a glovebox and used to measure the apparent thermal diffusivity of a packed bed of depleted uranium (DU) microspheres with argon fill in the void spaces. The developed Crucible Heater Test Assembly (CHTA) recorded radial temperature changes due to an initial heat pulse from a central thin-diameter cartridge heater. Using thermocouple positions and time–temperature data, the apparent thermal diffusivity was calculated. The thermal conductivity of the DU microspheres was calculated based on the thermal diffusivity from the CHTA, known material densities and specific heat capacities, and an assumed 70% packing density based on prior measurements. Results indicate that DU metal microspheres have very low thermal conductivity, relative to solid uranium metal, and rapidly form an oxidation layer even in a low oxygen environment. At 500 °C, the thermal conductivity of the DU metal microsphere bed was 0.431 ± 0.0560 W/m-K compared to the literature value of approximately 32 W/m-K for solid uranium metal
Estimating thermal diffusivity and specific heat from needle probe thermal conductivity data
Waite, W.F.; Gilbert, L.Y.; Winters, W.J.; Mason, D.H.
2006-01-01
Thermal diffusivity and specific heat can be estimated from thermal conductivity measurements made using a standard needle probe and a suitably high data acquisition rate. Thermal properties are calculated from the measured temperature change in a sample subjected to heating by a needle probe. Accurate thermal conductivity measurements are obtained from a linear fit to many tens or hundreds of temperature change data points. In contrast, thermal diffusivity calculations require a nonlinear fit to the measured temperature change occurring in the first few tenths of a second of the measurement, resulting in a lower accuracy than that obtained for thermal conductivity. Specific heat is calculated from the ratio of thermal conductivity to diffusivity, and thus can have an uncertainty no better than that of the diffusivity estimate. Our thermal conductivity measurements of ice Ih and of tetrahydrofuran (THF) hydrate, made using a 1.6 mm outer diameter needle probe and a data acquisition rate of 18.2 pointss, agree with published results. Our thermal diffusivity and specific heat results reproduce published results within 25% for ice Ih and 3% for THF hydrate. ?? 2006 American Institute of Physics.
High-Temperature Thermal Diffusivity Measurements of Silicate Glasses
Pertermann, M.; Hofmeister, A. M.; Whittington, A. G.; Spera, F. J.; Zayac, J.
2005-12-01
Transport of heat in geologically relevant materials is of great interest because of its key role in heat transport, magmatism and volcanic activity on Earth. To better understand the thermal properties of magmatic materials at high temperatures, we measured the thermal diffusivity of four synthetic end-member silicate glasses with the following compositions: albite (NaAlSi3O8), orthoclase (KAlSi3O8), anorthite (CaAl2Si2O8), and diopside (CaMgSi2O6). Thermal diffusivity measurements were conducted with the laser-flash technique and data were acquired from room temperature to a maximum temperature near 1100°C, depending on the glass transition temperature. The presence of sub-mm sized bubbles in one of the orthoclase samples had no discernable effect on measured diffusivities. At room temperature, the three feldspar-type glasses have thermal diffusivity (D) values of 0.58-0.61 mm2/s, whereas the diopside glass has 0.52 mm2/s. With increasing temperature, D decreases by 5-10% (relative) for all samples and becomes virtually constant at intermediate temperatures. At higher temperatures, the anorthite and diopside glasses exhibit significant drops in thermal diffusivity over a 50-100°C interval, correlating with previously published heat capacity changes near the glass transition for these compositions. For anorthite, D (in mm2/s) decreases from 0.48 at 750-860°C to 0.36 at 975-1075°C; for diopside, D changes from 0.42 at 630-750°C to 0.30 at 850-910°C, corresponding to relative drops of 24 and 29%, respectively. Albite and orthoclase glasses do not exhibit this change and also lack significant changes in heat capacity near the glass transition. Instead, D is constant at 400-800°C for albite, and for orthoclase values go through a minimum at 500-600°C before increasing slightly towards 1100°C but it never exceeds the room temperature D. Our data on thermal diffusivity correlate closely with other thermophysical properties. Thus, at least in case of simple
Instrumentation for thermal diffusivity determination of sintered materials
International Nuclear Information System (INIS)
Turquetti Filho, R.
1990-01-01
A new procedure to measure the sinterized materials thermal diffusivity, using the heat pulse method was developed in this work. The experimental data were performed at room temperature with UO sub(2), ThO sub(2), and Al sub(2)O sub(3) samples with 94%, 95%, and 96% of theoretical densities, respectively. Nondimensional root mean square deviation for theoretical function fitting was found to be on the order, of 10 sup(-3). The total error associated with the measurements for thermal diffusivity was ± 5%. (author)
Thermal diffusivity of alumina-zirconia sintered with niobium additions
International Nuclear Information System (INIS)
Santos, W.N. dos; Paulin Filho, P.I.; Taylor, R.
1994-01-01
The effect of niobium oxide addition on the alumina-zirconia thermal diffusivity was investigated from 100 0 C to 1000 0 C by the laser flash method. It was observed that 4 to 6% addition of niobium oxide increases the thermal diffusivity when samples were sintered at 1450 0 C. This effect was due to elimination of porosity by formation of liquid please above 1420 0 C in the Al 2 O 3 - Nb 2 O 5 system. (author). 7 refs., 3 figs
An extension of diffusion theory for thermal neutrons near boundaries
International Nuclear Information System (INIS)
Alvarez Rivas, J. L.
1963-01-01
The distribution of thermal neutron flux has been measured inside and outside copper rods of several diameters, immersed in water. It has been found that these distributions can be calculated by means of elemental diffusion theory if the value of the coefficient of diffusion is changed. this parameter is truly a diffusion coefficient, which now also depends on the diameter of the rod. Through a model an expression of this coefficient is introduced which takes account of the measurements of the author and of those reported in PIGC P/928 (1995), ANL-5872 (1959), DEGR 319 (D) (1961). This model could be extended also to plane geometry. (Author) 19 refs
International Nuclear Information System (INIS)
Ruan, Ying; Li, Liuhui; Gu, Qianqian; Zhou, Kai; Yan, Na; Wei, Bingbo
2016-01-01
Highlights: • Length change difference between rapidly and slowly solidified Co-Si alloy occurs at high temperature. • Generally CTE increases with an increasing Si content. • The thermal diffusion abilities are CoSi 2 > Co 95 Si 5 > Co 90 Si 10 > Co 2 Si > CoSi if T exceeds 565 K. • All the CTE and thermal diffusivity variations with T satisfy linear or polynomial relations. - Abstract: The thermal expansion of Co-Si solid solutions and intermetallic compounds was measured via dilatometric method, compared with the results of first-principles calculations, and their thermal diffusivities were investigated using laser flash method. The length changes of rapidly solidified Co-Si alloys are larger than those of slowly solidified alloys when temperature increases to around 1000 K due to the more competitive atom motion. The coefficient of thermal expansion (α) of Co-Si alloy increases with an increasing Si content, except that the coefficient of thermal expansion of Co 95 Si 5 influenced by both metastable structure and allotropic transformation is lower than that of Co 90 Si 10 at a higher temperature. The thermal expansion abilities of Co-Si intermetallic compounds satisfy the relationship of Co 2 Si > CoSi > CoSi 2 , and the differences of the coefficients of thermal expansion between them increase with the rise of temperature. The thermal diffusivity of CoSi 2 is evidently larger than the values of other Co-Si alloys. If temperature exceeds 565 K, their thermal diffusion abilities are CoSi 2 > Co 95 Si 5 > Co 90 Si 10 > Co 2 Si > CoSi. All the coefficient of thermal expansion and thermal diffusivity variations with temperature satisfy linear or polynomial relations.
Measurement of through-thickness thermal diffusivity of thermoplastics using thermal wave method
Singh, R.; Mellinger, A.
2015-04-01
Thermo-physical properties, such as thermal conductivity, thermal diffusivity and specific heat are important quantities that are needed to interpret and characterize thermoplastic materials. Such characterization is necessary for many applications, ranging from aerospace engineering to food packaging, electrical and electronic industry and medical science. In this work, the thermal diffusivity of commercially available polymeric films is measured in the thickness direction at room temperature using thermal wave method. The results obtained with this method are in good agreement with theoretical and experimental values.
Thermal-Diffusivity-Based Frequency References in Standard CMOS
Kashmiri, S.M.
2012-01-01
In recent years, a lot of research has been devoted to the realization of accurate integrated frequency references. A thermal-diffusivity-based (TD) frequency reference provides an alternative method of on-chip frequency generation in standard CMOS technology. A frequency-locked loop locks the
Thermal diffusion baro-effect in cluster gases
International Nuclear Information System (INIS)
Kurlapov, L.M.; Segeda, T.A.
2003-01-01
Thermal diffusion baro-effect as a difference of pressure under which action in the established process in the close device the particles flow of an irreversible nature is counterbalanced by current of gas is considered. For not ideal gases the settlement formula is received, in which no ideality is taken into account through the compressibility factor and also for cluster mixture. (author)
Temperature mapping, thermal diffusivity and subsoil heat flux at ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
vide an understanding of the gain or loss of heat by the soil from the atmosphere. Many studies made earlier have been related to sim- ilar issues such as prediction of soil tempera- tures; heat storage variations; thermal diffusivity of the soil, etc. (Kelkar et al 1980; Chowdhury et al 1991; Lamba and Khambete 1991; Retnaku ...
Characteristics of Laser Flash Technique for Thermal Diffusivity Measurement
Energy Technology Data Exchange (ETDEWEB)
Park, D. G.; Kim, H. M.; Hong, G. P
2008-08-15
In relation to selection of thermal conductivity measurement technology, various thermal conductivity measurement technique are investigated for characteristics of each technique and it's measurable range. For the related laser flash techniques, various technical characteristics are reviewed and discussed. Especially, Parker adiabatic model are reviewed because of importance for basic theory of the thermal diffusivity determination. Finite pulse time effect, heat loss effect and non-uniform heating effect, which are main technical factors for laser flash technique, are considered. Finally, characteristics of constituent elements for laser flash measurement system are reviewed and investigated in detail.
Synthesis, Characterization and Thermal Diffusivity of Holmium and Praseodymium Zirconates
Stopyra M.; Niemiec D.; Moskal G.
2016-01-01
A2B2O7 oxides with pyrochlore or defected fluorite structure are among the most promising candidates for insulation layer material in thermal barrier coatings. The present paper presents the procedure of synthesis of holmium zirconate Ho2Zr2O7 and praseodymium zirconate Pr2Zr2O7 via Polymerized-Complex Method (PCM). Thermal analysis of precursor revealed that after calcination at relatively low temperature (700°C) fine-crystalline, single-phase material is obtained. Thermal diffusivity was me...
Thermal conductivity and thermal diffusivity of solid UO2
International Nuclear Information System (INIS)
Fink, J.K.; Chasanov, M.G.; Leibowitz, L.
1981-06-01
New equations for the thermal conductivity of solid UO 2 were derived based upon a nonlinear least squares fit of the data available in the literature. In the development of these equations, consideration was given to their thermodynamic consistency with heat capacity and density and theoretical consistency with enthalpy and heat capacity. Consistent with our previous treatment of enthalpy and heat capacity, 2670 K was selected as the temperature of a phase transition. A nonlinear equation, whose terms represent contributions due to phonons and electrons, was selected for the temperature region below 2670 K. Above 2670 K, the data were fit by a linear equation
The thermal conductivity and thermal diffusivity of four types of rice flours and one type of rice protein were determine at temperatures ranging from 4.8 to 36.8 C, bulk densities 535 to 875.8 kg/m3, and moisture contents 2.6 to 16.7 percent (w.b.), using a KD2 Thermal Properties Analyzer. It was ...
An anisotropic diffusion approximation to thermal radiative transfer
International Nuclear Information System (INIS)
Johnson, Seth R.; Larsen, Edward W.
2011-01-01
This paper describes an anisotropic diffusion (AD) method that uses transport-calculated AD coefficients to efficiently and accurately solve the thermal radiative transfer (TRT) equations. By assuming weak gradients and angular moments in the radiation intensity, we derive an expression for the radiation energy density that depends on a non-local function of the opacity. This nonlocal function is the solution of a transport equation that can be solved with a single steady-state transport sweep once per time step, and the function's second angular moment is the anisotropic diffusion tensor. To demonstrate the AD method's efficacy, we model radiation flow down a channel in 'flatland' geometry. (author)
Discrete Diffusion Monte Carlo for Electron Thermal Transport
Chenhall, Jeffrey; Cao, Duc; Wollaeger, Ryan; Moses, Gregory
2014-10-01
The iSNB (implicit Schurtz Nicolai Busquet electron thermal transport method of Cao et al. is adapted to a Discrete Diffusion Monte Carlo (DDMC) solution method for eventual inclusion in a hybrid IMC-DDMC (Implicit Monte Carlo) method. The hybrid method will combine the efficiency of a diffusion method in short mean free path regions with the accuracy of a transport method in long mean free path regions. The Monte Carlo nature of the approach allows the algorithm to be massively parallelized. Work to date on the iSNB-DDMC method will be presented. This work was supported by Sandia National Laboratory - Albuquerque.
Effects of variable thermal diffusivity on the structure of convection
Shcheritsa, O. V.; Getling, A. V.; Mazhorova, O. S.
2018-03-01
The structure of multiscale convection in a thermally stratified plane horizontal fluid layer is investigated by means of numerical simulations. The thermal diffusivity is assumed to produce a thin boundary sublayer convectively much more unstable than the bulk of the layer. The simulated flow is a superposition of cellular structures with three different characteristic scales. In contrast to the largest convection cells, the smaller ones are localised in the upper portion of the layer. The smallest cells are advected by the larger-scale convective flows. The simulated flow pattern qualitatively resembles that observed on the Sun.
Separation of Kr-Xe system by thermal diffusion method
International Nuclear Information System (INIS)
Yoshida, Hiroshi; Numata, Kazuyoshi; Matsuda, Yuji; Ouchi, Misao; Naruse, Yuji
1979-11-01
Separation experiments of Kr-Xe system were carried out to study the possibility of adapting thermal diffusion method for concentration of krypton in a fuel reprocessing off-gas treatment process. The results are as follows. (1) A batchwise thermal diffusion column of hot tube diameter 21 mm, cold tube diameter 32 mm, effective hight 1000 mm and volume -- 500 CC is the best in separation characteristics and in ease of operation under the different conditions. (2) The overall separation factor increases with increase of the operating temperature in the column with and without reservoir. (3) The optimum operating pressure (about 400 Torr) is independent of the operating conditions such as temperature, reservoir volume and feed gas content. (4) A preliminary design of the Kr-Xe separating plant for a reprocessing plant (1500 ton-U/yr) shows the required number of columns and the total electric power. (author)
Evaluation of the Thermodynamic Models for the Thermal Diffusion Factor
DEFF Research Database (Denmark)
Gonzalez-Bagnoli, Mariana G.; Shapiro, Alexander; Stenby, Erling Halfdan
2003-01-01
Over the years, several thermodynamic models for the thermal diffusion factors for binary mixtures have been proposed. The goal of this paper is to test some of these models in combination with different equations of state. We tested the following models: those proposed by Rutherford and Drickamer...... we applied different thermodynamic models, such as the Soave-Redlich-Kwong and the Peng-Robinson equations of state. The necessity to try different thermo-dynamic models is caused by the high sensitivity of the thermal diffusion factors to the values of the partial molar properties. Two different...... corrections for the determination of the partial molar volumes have been implemented; the Peneloux correction and the correction based on the principle of corresponding states....
Fractional Heat Conduction Models and Thermal Diffusivity Determination
Directory of Open Access Journals (Sweden)
Monika Žecová
2015-01-01
Full Text Available The contribution deals with the fractional heat conduction models and their use for determining thermal diffusivity. A brief historical overview of the authors who have dealt with the heat conduction equation is described in the introduction of the paper. The one-dimensional heat conduction models with using integer- and fractional-order derivatives are listed. Analytical and numerical methods of solution of the heat conduction models with using integer- and fractional-order derivatives are described. Individual methods have been implemented in MATLAB and the examples of simulations are listed. The proposal and experimental verification of the methods for determining thermal diffusivity using half-order derivative of temperature by time are listed at the conclusion of the paper.
Measurement of the diffusion length of thermal neutrons inside graphite
International Nuclear Information System (INIS)
Ertaud, A.; Beauge, R.; Fauquez, H.; De Laboulay, H.; Mercier, C.; Vautrey, L.
1948-11-01
The diffusion length of thermal neutrons inside a given industrial graphite is determined by measuring the neutron density inside a parallelepipedal piling up of graphite bricks (2.10 x 2.10 x 2.442 m). A 3.8 curies (Ra α → Be) source is placed inside the parallelepipedal block of graphite and thin manganese detectors are used. Corrections are added to the unweighted measurements to take into account the effects of the damping of supra-thermal neutrons in the measurement area. These corrections are experimentally deduced from the differential measurements made with a cadmium screen interposed between the source and the first plane of measurement. An error analysis completes the report. The diffusion length obtained is: L = 45.7 cm ± 0.3. The average density of the graphite used is 1.76 and the average apparent density of the piling up is 1.71. (J.S.)
Determination of thermal-diffusive properties of lyophilized food products
International Nuclear Information System (INIS)
Kaplon, J.; Kramkowski, R.; Berdzik, M.
1998-01-01
Experimental results of vacuum freeze drying were presented. Water solutions of skim milk were dried under various pressures and distribution of temperature and moisture as a function of drying time were determined. Unilateral radiant heating of the material was applied. On the basis of experiment results and URIF model of vacuum freeze drying the thermal conductivity and vapour diffusion coefficients in dry layer were determined
Lattice dynamics and thermal diffuse scattering for molecular crystals
International Nuclear Information System (INIS)
Kroon, P.A.
1977-01-01
Thermal diffuse scattering (TDS) corrections on the observed reflection intensities in the accurate determination of crystal structures by X-ray diffraction are emphasized. A lattice-dynamical model and procedure for lattice-dynamical calculations are set up. Expression for first- and second-order TDS intensity distributions are derived. A comparison with other models is made. First-order TDS corrections for naphtalene at 100 K are presented
LDPE and PP thermal diffusivity in molten state
Yánez, G.; Rodríguez - Pérez, M. A; Almanza, O. A.
2013-01-01
Experimental results are reported for measuring the thermal diffusivity of two polymer species: low density polyethylene (LDPE) and polypropylene (PP). Measurements were taken in unsteady state heat flow conditions around the materials' melting temperature, using a device specially constructed for this purpose. The experimental results for the sample's temperature profile (temperature gradient product) were adjusted with the theoretical results obtained by solving the heat conduction equation...
Determination of thermal neutrons diffusion length in graphite
International Nuclear Information System (INIS)
Garcia Fite, J.
1959-01-01
The diffusion length of thermal neutrons in graphite using the less possible quantity of material has been determined. The proceeding used was the measurement in a graphite pile which has a punctual source of rapid neutrons inside surrounded by a reflector medium (paraffin or water). The measurement was done in the following conditions: a) introducing an aluminium plate between both materials. b) Introducing a cadmium plate between both materials. (Author) 91 refs
Synthesis, Characterization and Thermal Diffusivity of Holmium and Praseodymium Zirconates
Directory of Open Access Journals (Sweden)
Stopyra M.
2016-06-01
Full Text Available A2B2O7 oxides with pyrochlore or defected fluorite structure are among the most promising candidates for insulation layer material in thermal barrier coatings. The present paper presents the procedure of synthesis of holmium zirconate Ho2Zr2O7 and praseodymium zirconate Pr2Zr2O7 via Polymerized-Complex Method (PCM. Thermal analysis of precursor revealed that after calcination at relatively low temperature (700°C fine-crystalline, single-phase material is obtained. Thermal diffusivity was measured in temperature range 25-200°C, Ho2Zr2O7 exhibits lower thermal diffusivity than Pr2Zr2O7. Additionally, PrHoZr2O7 was synthesized. The powder in as-calcined condition is single-phase, but during the sintering decomposition of solid solution took place and Ho-rich phase precipitated. This material exhibited the best insulating properties among the tested ones.
DEFF Research Database (Denmark)
Bording, Thue Sylvester; Nielsen, Søren Bom; Balling, Niels
2016-01-01
and volumetric heat capacity, and thereby also thermal diffusivity, are measured simultaneously. As the density of samples is easily determined independently, specific heat capacity may also be determined. Finite element formulation provides a flexible forward solution for heat transfer across the bar...... and thermal properties are estimated by inverse Monte Carlo modelling. This methodology enables a proper quantification of experimental uncertainties on measured thermal properties. The developed methodology was applied to laboratory measurements of various materials, including a standard ceramic material......-3 %, and for diffusivity uncertainty may be reduced to about 3-5 %. The main uncertainty originates from the presence of thermal contact resistance associated with the internal interfaces of the bar. They are not resolved during inversion, and it is highly important that they are minimized by careful sample preparation....
Thermal diffusivity and conductivity of thorium- uranium mixed oxides
Saoudi, M.; Staicu, D.; Mouris, J.; Bergeron, A.; Hamilton, H.; Naji, M.; Freis, D.; Cologna, M.
2018-03-01
Thorium-uranium oxide pellets with high densities were prepared at the Canadian Nuclear Laboratories (CNL) by co-milling, pressing, and sintering at 2023 K, with UO2 mass contents of 0, 1.5, 3, 8, 13, 30, 60 and 100%. At the Joint Research Centre, Karlsruhe (JRC-Karlsruhe), thorium-uranium oxide pellets were prepared using the spark plasma sintering (SPS) technique with 79 and 93 wt. % UO2. The thermal diffusivity of (Th1-xUx)O2 (0 ≤ x ≤ 1) was measured at CNL and at JRC-Karlsruhe using the laser flash technique. ThO2 and (Th,U)O2 with 1.5, 3, 8 and 13 wt. % UO2 were found to be semi-transparent to the infrared wavelength of the laser and were coated with graphite for the thermal diffusivity measurements. This semi-transparency decreased with the addition of UO2 and was lost at about 30 wt. % of UO2 in ThO2. The thermal conductivity was deduced using the measured density and literature data for the specific heat capacity. The thermal conductivity for ThO2 is significantly higher than for UO2. The thermal conductivity of (Th,U)O2 decreases rapidly with increasing UO2 content, and for UO2 contents of 60% and higher, the conductivity of the thorium-uranium oxide fuel is close to UO2. As the mass difference between the Th and U atoms is small, the thermal conductivity decrease is attributed to the phonon scattering enhanced by lattice strain due to the introduction of uranium in ThO2 lattice. The new results were compared to the data available in the literature and were evaluated using the classical phonon transport model for oxide systems.
Energetics of silicate melts from thermal diffusion studies. Final report
International Nuclear Information System (INIS)
Walker, D.
1997-01-01
Initially this project was directed towards exploiting Soret diffusion of silicate liquids to learn about the internal energetics of the constituents of the liquids. During the course of this project this goal was realized at the same time a series of intellectual and technical developments expanded the scope of the undertaking. Briefly recapping some of the highlights, the project was initiated after the discovery that silicate liquids were strongly Soret-active. It was possible to observe the development of strong diffusive gradients in silicate liquid composition in response to laboratory-imposed thermal gradients. The character of the chemical separations was a direct window into the internal speciation of the liquids; the rise time of the separation was a useful entree to quantitatively measuring chemical diffusivity; and the steady state magnitude of the separation proved to be an excellent determinant of the constituents' mixing energies. A comprehensive program was initiated to measure the separations, rise times, and mixing energies of a range of geologically and technically interesting silicate liquids. An additional track of activities in the DOE project has run in parallel to the Soret investigation of single-phase liquids in a thermal gradient. This additional track is the study of liquid-plus-crystal systems in a thermal gradient. In these studies solubility-driven diffusion introduced many useful effects, some quite surprising. In partially molten silicate liquids the authors applied their experiments to understanding magmatic cumulate rocks. They have also applied their understanding of these systems to aspects of evaporite deposits in the geological record. They also undertook studies of this sort in systems with retrograde solubility in order to form the basis for understanding remediation for brine migration problems in evaporite-hosted nuclear waste repositories such as the WIPP
Thermal diffusion boron doping of single-crystal natural diamond
Energy Technology Data Exchange (ETDEWEB)
Seo, Jung-Hun; Mikael, Solomon; Mi, Hongyi; Venkataramanan, Giri; Ma, Zhenqiang, E-mail: mazq@engr.wisc.edu [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Wu, Henry; Morgan, Dane [Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Blanchard, James P. [Department of Nuclear Engineering and Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Zhou, Weidong [Department of Electrical Engineering, NanoFAB Center, University of Texas at Arlington, Arlington, Texas 76019 (United States); Gong, Shaoqin [Department of Biomedical Engineering and Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)
2016-05-28
With the best overall electronic and thermal properties, single crystal diamond (SCD) is the extreme wide bandgap material that is expected to revolutionize power electronics and radio-frequency electronics in the future. However, turning SCD into useful semiconductors requires overcoming doping challenges, as conventional substitutional doping techniques, such as thermal diffusion and ion implantation, are not easily applicable to SCD. Here we report a simple and easily accessible doping strategy demonstrating that electrically activated, substitutional doping in SCD without inducing graphitization transition or lattice damage can be readily realized with thermal diffusion at relatively low temperatures by using heavily doped Si nanomembranes as a unique dopant carrying medium. Atomistic simulations elucidate a vacancy exchange boron doping mechanism that occurs at the bonded interface between Si and diamond. We further demonstrate selectively doped high voltage diodes and half-wave rectifier circuits using such doped SCD. Our new doping strategy has established a reachable path toward using SCDs for future high voltage power conversion systems and for other novel diamond based electronic devices. The novel doping mechanism may find its critical use in other wide bandgap semiconductors.
Thermal diffusion boron doping of single-crystal natural diamond
International Nuclear Information System (INIS)
Seo, Jung-Hun; Mikael, Solomon; Mi, Hongyi; Venkataramanan, Giri; Ma, Zhenqiang; Wu, Henry; Morgan, Dane; Blanchard, James P.; Zhou, Weidong; Gong, Shaoqin
2016-01-01
With the best overall electronic and thermal properties, single crystal diamond (SCD) is the extreme wide bandgap material that is expected to revolutionize power electronics and radio-frequency electronics in the future. However, turning SCD into useful semiconductors requires overcoming doping challenges, as conventional substitutional doping techniques, such as thermal diffusion and ion implantation, are not easily applicable to SCD. Here we report a simple and easily accessible doping strategy demonstrating that electrically activated, substitutional doping in SCD without inducing graphitization transition or lattice damage can be readily realized with thermal diffusion at relatively low temperatures by using heavily doped Si nanomembranes as a unique dopant carrying medium. Atomistic simulations elucidate a vacancy exchange boron doping mechanism that occurs at the bonded interface between Si and diamond. We further demonstrate selectively doped high voltage diodes and half-wave rectifier circuits using such doped SCD. Our new doping strategy has established a reachable path toward using SCDs for future high voltage power conversion systems and for other novel diamond based electronic devices. The novel doping mechanism may find its critical use in other wide bandgap semiconductors.
Thermal diffusivity of solids; Diffusivite thermique des solides
Energy Technology Data Exchange (ETDEWEB)
Kleimann, H; Fetiveau, Y; Richard, M; Eyraud, L; Eyraud, C; Elston, J [Institut National des Sciences Appliquees, Lyon (France); Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1969-07-01
The authors recall the different methods of thermal diffusivity measurements and point out the possible causes of errors. They study in particular the sinusoidal methods of thermal attack using the measurement of either an amplitude or a phase, in which the controlled energy in-put is obtained either by Joule effect or by radiation. By the use of controlled systems, it is possible to apply those methods to the measurement of thermal diffusivity of their samples in a large scale of temperature. The authors describe their experimental achievements and give several results dealing especially with Al{sub 2}O{sub 3}, BeO, MgO. (author) [French] Les auteurs rappellent les diverses methodes de mesure de la diffusivite thermique et indiquent les sources d'erreurs possibles. Ils etudient particulierement les methodes d'attaque thermique sinusoidales utilisant soit une mesure d'amplitude, soit une mesure de phase dans lesquelles l'apport energetique controle est effectue soit par effet Joule, soit par rayonnement. La mise en oeuvre de systemes asservis permet l'utilisation de ces methodes pour la mesure de la diffusivite thermique d'echantillons minces dans une gamme etendue de temperature. Les auteurs decrivent les realisations experimentales et fournissent divers resultats concernant notamment Al{sub 2}O{sub 3}, BeO, MgO. (auteur)
DEFF Research Database (Denmark)
Zajas, Jan Jakub; Heiselberg, Per
The LFA 447 can be successfully used for measurements of thermal diffusivity, specific heat and thermal conductivity of various samples. It is especially useful when determining the properties of materials on a very small scale. The matrix measurement mode allows for determining the local...... that the heat losses from both samples during the measurement are similar. Finally, the leveling of the samples is very important. Very small discrepancies can cause a massive error in the derivation of specific heat capacity and, as a result, thermal conductivity....
Hu, Jiuning; Chen, Yong P.
2013-06-01
We show that in a finite one-dimensional (1D) system with diffusive thermal transport described by the Fourier's law, negative differential thermal conductance (NDTC) cannot occur when the temperature at one end is fixed and there are no abrupt junctions. We demonstrate that NDTC in this case requires the presence of junction(s) with temperature-dependent thermal contact resistance (TCR). We derive a necessary and sufficient condition for the existence of NDTC in terms of the properties of the TCR for systems with a single junction. We show that under certain circumstances we even could have infinite (negative or positive) differential thermal conductance in the presence of the TCR. Our predictions provide theoretical basis for constructing NDTC-based devices, such as thermal amplifiers, oscillators, and logic devices.
Fossil rocks of slow earthquake detected by thermal diffusion length
Hashimoto, Yoshitaka; Morita, Kiyohiko; Okubo, Makoto; Hamada, Yohei; Lin, Weiren; Hirose, Takehiro; Kitamura, Manami
2016-04-01
Fault motion has been estimated by diffusion pattern of frictional heating recorded in geology (e.g., Fulton et al., 2012). The same record in deeper subduction plate interface can be observed from micro-faults in an exhumed accretionary complex. In this study, we focused on a micro-fault within the Cretaceous Shimanto Belt, SW Japan to estimate fault motion from the frictional heating diffusion pattern. A carbonaceous material concentrated layer (CMCL) with ~2m of thickness is observed in study area. Some micro-faults cut the CMCL. Thickness of a fault is about 3.7mm. Injection veins and dilatant fractures were observed in thin sections, suggesting that the high fluid pressure was existed. Samples with 10cm long were collected to measure distribution of vitrinite reflectance (Ro) as a function of distance from the center of micro-fault. Ro of host rock was ~1.0%. Diffusion pattern was detected decreasing in Ro from ~1.2%-~1.1%. Characteristic diffusion distance is ~4-~9cm. We conducted grid search to find the optimal frictional heat generation per unit area per second (Q (J/m^2/s), the product of friction coefficient, normal stress and slip velocity) and slip duration (t(s)) to fit the diffusion pattern. Thermal diffusivity (0.98*10^8m^2/s) and thermal conductivity (2.0 w/mK) were measured. In the result, 2000-2500J/m^2/s of Q and 63000-126000s of t were estimated. Moment magnitudes (M0) of slow earthquakes (slow EQs) follow a scaling law with slip duration and its dimension is different from that for normal earthquakes (normal EQ) (Ide et al., 2007). The slip duration estimated in this study (~10^4-~10^5s) consistent with 4-5 of M0, never fit to the scaling law for normal EQ. Heat generation can be inverted from 4-5 of M0, corresponding with ~10^8-~10^11J, which is consistent with rupture area of 10^5-10^8m2 in this study. The comparisons in heat generation and slip duration between geological measurements and geophysical remote observations give us the
A diffusive thermal phase shifter; Dephaseur thermique diffusif
Energy Technology Data Exchange (ETDEWEB)
Lachal, B; Hollmuller, P; Zgraggen, J -M [Universite de Geneve, Centre universitaire d' etude des problemes de l' energie(CUEPE), Geneva (Switzerland)
2004-07-01
The investigations carried out in this project show that dephasing a thermal oscillation carried by an air flow by utilizing the heat exchange with a diffusive heat store made of thin layers, is possible without any significant damping of the oscillation. The practical application of this phenomenon, with a time shift of 8 to 12 hours, looks particularly attractive for space cooling of buildings during summertime or in hot climates. The possibilities of dephasing completely a thermal wave (i.e. by a half period) carried by a stream of air have been investigated both theoretically by model calculations and experimentally by building two prototypes. Promising results have been obtained for the case of a daily phase shift. In the case of a summer-winter shift the required volumes and lengths seem too large to enable such a storage system becoming cost effective.
Thermal diffusion of water vapour in porous materials: fact or fiction?
DEFF Research Database (Denmark)
Janssen, Hans
2011-01-01
diffusion. Thermal diffusion opponents, on the other hand, assert that these thermal transports are negligibly small. This paper resolves that contradiction. A critical analysis of the investigations supporting the occurrence of thermal diffusion reveals that all are flawed. A correct reinterpretation...... its negligible magnitude. It can in conclusion be stated that thermal diffusion is of no importance for building science applications, leaving vapour pressure as the sole significant transport potential for the diffusion of water vapour in porous materials. (C) 2010 Elsevier Ltd. All rights reserved....
Electron diffraction patterns with thermal diffuse scattering maxima around Kikuchi lines
International Nuclear Information System (INIS)
Karakhanyan, R. K.; Karakhanyan, K. R.
2011-01-01
Transmission electron diffraction patterns of silicon with thermal diffuse maxima around Kikuchi lines, which are analogs of the maxima of thermal diffuse electron scattering around point reflections, have been recorded. Diffuse maxima are observed only around Kikuchi lines with indices that are forbidden for the silicon structure. The diffraction conditions for forming these maxima are discussed.
Thermal diffusivity and thermal conductivity of (Th,U)O2 fuels
International Nuclear Information System (INIS)
Sengupta, A.K.; Jarvis, T.; Nair, M.R.; Ramachandran, R.; Mujumdar, S.; Purushotham, D.S.C.
2000-05-01
India has vast reserves of thorium (> 460,000 tons) and sustained work on all aspects of thorium utilization has been initiated. In this context work on fabrication of sintered thoria and mixed (Th,U)O 2 pellets and evaluation of their thermophysical properties have been taken up in Radiometallurgy Division. Thermal conductivity, being the most important thermal properties, has been calculated using the experimentally measured thermal diffusivity, density and literature values of specific heats for ThO 2 and thoria containing 2,4,6,10 and 20% UO 2 . Thermal diffusivity was measured experimentally by the laser flash method from 600 to 1600 deg C in vacuum. It was observed that thermal conductivity of ThO 2 and mixed (Th,U)O 2 decrease with increase in temperature. It was also observed that the conductivity decreases with increase in UO 2 content, the decrease being more at lower temperature than that at higher temperatures. Empirical relations correlating thermal conductivity to temperatures have been generated by the least square fit method and reported. (author)
Thermal diffusivity from heat wave propagation in Wendelstein 7-AS
Energy Technology Data Exchange (ETDEWEB)
Hartfuss, H J; Erckmann, V; Giannone, L.; Maassberg, H; Tutter, M [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany)
1991-01-01
Electron thermal diffusivity studies can be carried out in two ways: static and dynamic. In the static analysis, the transport coefficients are determined from the stationary power balance, in the dynamic analysis from the propagation of a small perturbation of the stationary plasma state which can be caused by either a sawtooth generated heat pulse or modulation of the heating power. Electron thermal diffusivity [chi][sub e] is deduced from the evolution of the perturbed electron temperature T[sub e] at different locations r[sub i] in the plasma. [chi][sub e] values obtained from perturbation analysis are usually greater than those calculated from power balance. It has been pointed out that there is a principal difference between static and perturbative analysis. Whereas the static method yields the transport coefficient [chi][sub e]=q[sub e]/n[sub e][nabla]T[sub e], the perturbative method leads to an increase of the flux q[sub e] as a result of an increase in the temperature gradient [nabla]T[sub e]. The quantity determined is an incremental [chi][sub e] as defined by [chi][sub e][sup inc]=[partial derivative]q[sub e]/n[sub e][partial derivative]([nabla]T[sub e]). By varying the modulation of the heating power at different frequencies and amplitudes one can address the question whether or not this discrepancy is a function of the varied parameters. (author) 7 refs., 2 figs.
Thermal diffusivity from heat wave propagation in Wendelstein 7-AS
International Nuclear Information System (INIS)
Hartfuss, H.J.; Erckmann, V.; Giannone, L.; Maassberg, H.; Tutter, M.
1991-01-01
Electron thermal diffusivity studies can be carried out in two ways: static and dynamic. In the static analysis, the transport coefficients are determined from the stationary power balance, in the dynamic analysis from the propagation of a small perturbation of the stationary plasma state which can be caused by either a sawtooth generated heat pulse or modulation of the heating power. Electron thermal diffusivity χ e is deduced from the evolution of the perturbed electron temperature T e at different locations r i in the plasma. χ e values obtained from perturbation analysis are usually greater than those calculated from power balance. It has been pointed out that there is a principal difference between static and perturbative analysis. Whereas the static method yields the transport coefficient χ e = q e /n e ∇T e , the perturbative methods leads to an icnrease of the flux q e as a result of an increase in the temperature gradient ∇T e . The quantity determined is an incremental χ e as defined by χ e inc =δq e /n e δ(∇T e ). By varying the modulation of the heating power at different frequencies and amplitudes one can address the question whether or not this discrepancy is a function of the varied parameters. (orig.)
Numerical methods for calculating thermal residual stresses and hydrogen diffusion
International Nuclear Information System (INIS)
Leblond, J.B.; Devaux, J.; Dubois, D.
1983-01-01
Thermal residual stresses and hydrogen concentrations are two major factors intervening in cracking phenomena. These parameters were numerically calculated by a computer programme (TITUS) using the FEM, during the deposition of a stainless clad on a low-alloy plate. The calculation was performed with a 2-dimensional option in four successive steps: thermal transient calculation, metallurgical transient calculation (determination of the metallurgical phase proportions), elastic-plastic transient (plain strain conditions), hydrogen diffusion transient. Temperature and phase dependence of hydrogen diffusion coefficient and solubility constant. The following results were obtained: thermal calculations are very consistent with experiments at higher temperatures (due to the introduction of fusion and solidification latent heats); the consistency is not as good (by 70 degrees) for lower temperatures (below 650 degrees C); this was attributed to the non-introduction of gamma-alpha transformation latent heat. The metallurgical phase calculation indicates that the heat affected zone is almost entirely transformed into bainite after cooling down (the martensite proportion does not exceed 5%). The elastic-plastic calculations indicate that the stresses in the heat affected zone are compressive or slightly tensile; on the other hand, higher tensile stresses develop on the boundary of the heat affected zone. The transformation plasticity has a definite influence on the final stress level. The return of hydrogen to the clad during the bainitic transformation is but an incomplete phenomenon and the hydrogen concentration in the heat affected zone after cooling down to room temperature is therefore sufficient to cause cold cracking (if no heat treatment is applied). Heat treatments are efficient in lowering the hydrogen concentration. These results enable us to draw preliminary conclusions on practical means to avoid cracking. (orig.)
International Nuclear Information System (INIS)
Fink, J.K.; Chasanov, M.G.; Leibowitz, L.
Equations have been derived for the enthalpy, heat capacity, thermal conductivity, and thermal diffusivity of UO 2 . In selection of these equations, we considered the traditional criterion of lowest relative standard deviation between experimental data and the function chosen to fit these data as well as consistency between the thermophysical properties. In the latter case, we considered consistency in (1) thermodynamic relations among properties, (2) the choice of physical phenomena on which to base the theoretical formulation of the equations, and (3) the existence and temperature of phase transitions
Thermal diffuse scattering in angular-dispersive neutron diffraction
International Nuclear Information System (INIS)
Popa, N.C.; Willis, B.T.M.
1998-01-01
The theoretical treatment of one-phonon thermal diffuse scattering (TDS) in single-crystal neutron diffraction at fixed incident wavelength is reanalysed in the light of the analysis given by Popa and Willis [Acta Cryst. (1994), (1997)] for the time-of-flight method. Isotropic propagation of sound with different velocities for the longitudinal and transverse modes is assumed. As in time-of-flight diffraction, there exists, for certain scanning variables, a forbidden range in the one-phonon TDS of slower-than-sound neutrons, and this permits the determination of the sound velocity in the crystal. A fast algorithm is given for the TDS correction of neutron diffraction data collected at a fixed wavelength: this algorithm is similar to that reported earlier for the time-of-flight case. (orig.)
Validation of a mixture-averaged thermal diffusion model for premixed lean hydrogen flames
Schlup, Jason; Blanquart, Guillaume
2018-03-01
The mixture-averaged thermal diffusion model originally proposed by Chapman and Cowling is validated using multiple flame configurations. Simulations using detailed hydrogen chemistry are done on one-, two-, and three-dimensional flames. The analysis spans flat and stretched, steady and unsteady, and laminar and turbulent flames. Quantitative and qualitative results using the thermal diffusion model compare very well with the more complex multicomponent diffusion model. Comparisons are made using flame speeds, surface areas, species profiles, and chemical source terms. Once validated, this model is applied to three-dimensional laminar and turbulent flames. For these cases, thermal diffusion causes an increase in the propagation speed of the flames as well as increased product chemical source terms in regions of high positive curvature. The results illustrate the necessity for including thermal diffusion, and the accuracy and computational efficiency of the mixture-averaged thermal diffusion model.
Thermal Diffusivity Measurement for p-Si and Ag/p-Si by Photoacoustic Technique
Hussein, Mohammed Jabbar; Yunus, W. Mahmood Mat; Kamari, Halimah Mohamed; Zakaria, Azmi
2015-10-01
Thermal diffusivity (TD) of p-Si and Ag/p-Si samples were measured by photoacoustic technique using open photoacoustic cell (OPC). The samples were annealed by heating them at 960, 1050, 1200, and 1300 °C for 3 h in air. The thermal diffusivity of Ag-coated samples was obtained by fitting the photoacoustic experimental data to the thermally thick equation for Rosencwaig and Gersho (RG) theory. For the single layer samples, the thermal diffusivity can be obtained by fitting as well as by obtaining the critical frequency f c . In this study, the thermal diffusivity of the p-Si samples increased with increasing the annealing temperature. The thermal diffusivity of the Ag/p-Si samples, after reaching the maximum value of about 2.73 cm2/s at a temperature of 1200 °C, decreased due to the silver complete melt in the surface of the silicon.
Thermal diffusivity measurement for p-Si and Ag/p-Si by photoacoustic technique
Energy Technology Data Exchange (ETDEWEB)
Hussein, Mohammed Jabbar; Yunus, W. Mahmood Mat; Kamari, Halimah Mohamed; Zakaria, Azmi, E-mail: mohammed55865@yahoo.com [Department of Physics, Faculty of Science, Universiti PutraMalaysia (UPM), Serdang (Malaysia)
2015-10-15
Thermal diffusivity (TD) of p-Si and Ag/p-Si samples were measured by photoacoustic technique using open photoacoustic cell (OPC). The samples were annealed by heating them at 960, 1050, 1200, and 1300 °C for 3 h in air. The thermal diffusivity of Ag-coated samples was obtained by fitting the photoacoustic experimental data to the thermally thick equation for Rosencwaig and Gersho (RG) theory. For the single layer samples, the thermal diffusivity can be obtained by fitting as well as by obtaining the critical frequency f{sub c.} In this study, the thermal diffusivity of the p-Si samples increased with increasing the annealing temperature. The thermal diffusivity of the Ag/p-Si samples, after reaching the maximum value of about 2.73 cm{sup 2}/s at a temperature of 1200 °C, decreased due to the silver complete melt in the surface of the silicon. (author)
Thermal conductivity thermal diffusivity of UO{sub 2}-BeO nuclear fuel pellets
Energy Technology Data Exchange (ETDEWEB)
Mansur, Fábio A.; Camarano, Denise M.; Santos, Ana M. M.; Ferraz, Wilmar B.; Silva, Mayra A.; Ferreira, Ricardo A.N., E-mail: fam@cdtn.br, E-mail: dmc@cdtn.br, E-mail: amms@cdtn.br, E-mail: ferrazw@cdtn.br, E-mail: mayra.silva@cdtn.br, E-mail: ricardoanf@yahoo.com.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)
2017-07-01
The temperature distribution in nuclear fuel pellets is of vital importance for the performance of the reactor, as it affects the heat transfer, the mechanical behavior and the release of fission gas during irradiation, reducing safety margins in possible accident scenarios. One of the main limitation for the current uranium dioxide nuclear fuel (UO{sub 2}) is its low thermal conductivity, responsible for the higher temperature of the pellet center and, consequently, for a higher radial temperature gradient. Thus, the addition of another material to increase the UO{sub 2} fuel thermal conductivity has been considered. Among the additives that are being investigated, beryllium oxide (BeO) has been chosen due to its high thermal conductivity, with potential to optimize power generation in pressurized light water reactors (PWR). In this work, UO{sub 2}-BeO pellets were obtained by the physical mixing of the powders with additions of 2wt% and 3wt% of BeO. The thermal diffusivity and conductivity of the pellets were determined from room temperature up to 500 °C. The results were normalized to 95% of the theoretical density (TD) of the pellets and varied according to the BeO content. The range of the values of thermal diffusivity and conductivity were 1.22 mm{sup 2}∙s{sup -1} to 3.69 mm{sup 2}∙s{sup -1} and 3.80 W∙m{sup -}'1∙K{sup -1} to 9.36 W∙m{sup -1}∙K{sup -1}, respectively. (author)
The Measurement of Thermal Diffusivity in Conductor and Insulator by Photodeflection Technique
Achathongsuk, U.; Rittidach, T.; Tipmonta, P.; Kijamnajsuk, P.; Chotikaprakhan, S.
2017-09-01
The purpose of this study is to estimate thermal diffusivities of high thermal diffusivity bulk material as well as low thermal diffusivity bulk material by using many types of fluid such as Ethyl alcohol and water. This method is studied by measuring amplitude and phase of photodeflection signal in various frequency modulations. The experimental setup consists of two laser lines: 1) a pump laser beams through a modulator, varied frequency, controlled by lock-in amplifier and focused on sample surface by lens. 2) a probe laser which parallels with the sample surface and is perpendicular to the pump laser beam. The probe laser deflection signal is obtained by a position sensor which controlled by lock-in amplifier. Thermal diffusivity is calculated by measuring the amplitude and phase of the photodeflection signal and compared with the thermal diffusivity of a standard value. The thermal diffusivity of SGG agrees well with the literature but the thermal diffusivity of Cu is less than the literature value by a factor of ten. The experiment requires further improvement to measure the thermal diffusivity of Cu. However, we succeed in using ethyl alcohol as the coupling medium instead of CCl4 which is highly toxic.
Modelling thermal radiation and soot formation in buoyant diffusion flames
International Nuclear Information System (INIS)
Demarco Bull, R.A.
2012-01-01
The radiative heat transfer plays an important role in fire problems since it is the dominant mode of heat transfer between flames and surroundings. It controls the pyrolysis, and therefore the heat release rate, and the growth rate of the fire. In the present work a numerical study of buoyant diffusion flames is carried out, with the main objective of modelling the thermal radiative transfer and the soot formation/destruction processes. In a first step, different radiative property models were tested in benchmark configurations. It was found that the FSCK coupled with the Modest and Riazzi mixing scheme was the best compromise in terms of accuracy and computational requirements, and was a good candidate to be implemented in CFD codes dealing with fire problems. In a second step, a semi-empirical soot model, considering acetylene and benzene as precursor species for soot nucleation, was validated in laminar co flow diffusion flames over a wide range of hydrocarbons (C1-C3) and conditions. In addition, the optically-thin approximation was found to produce large discrepancies in the upper part of these small laminar flames. Reliable predictions of soot volume fractions require the use of an advanced radiation model. Then the FSCK and the semi-empirical soot model were applied to simulate laboratory-scale and intermediate-scale pool fires of methane and propane. Predicted flame structures as well as the radiant heat flux transferred to the surroundings were found to be in good agreement with the available experimental data. Finally, the interaction between radiation and turbulence was quantified. (author)
International Nuclear Information System (INIS)
Palmer, B.J.
1994-01-01
A method to calculate the thermal diffusivity D T from spontaneous fluctuations in the local heat energy density is presented. Calculations of the thermal diffusivity are performed for the Lennard-Jones fluid, carbon dioxide, and water. The results for the Lennard-Jones fluid are in agreement with calculations of the thermal conductivity using Green-Kubo relations and nonequilibrium molecular-dynamics techniques. The results for carbon dioxide and water give thermal diffusivities within a factor of 2 of the experimental values
International Nuclear Information System (INIS)
Van Berkel, M; Hogeweij, G M D; Van den Brand, H; De Baar, M R; Zwart, H J; Vandersteen, G
2014-01-01
In this paper, the estimation of the thermal diffusivity from perturbative experiments in fusion plasmas is discussed. The measurements used to estimate the thermal diffusivity suffer from stochastic noise. Accurate estimation of the thermal diffusivity should take this into account. It will be shown that formulas found in the literature often result in a thermal diffusivity that has a bias (a difference between the estimated value and the actual value that remains even if more measurements are added) or have an unnecessarily large uncertainty. This will be shown by modeling a plasma using only diffusion as heat transport mechanism and measurement noise based on ASDEX Upgrade measurements. The Fourier coefficients of a temperature perturbation will exhibit noise from the circular complex normal distribution (CCND). Based on Fourier coefficients distributed according to a CCND, it is shown that the resulting probability density function of the thermal diffusivity is an inverse non-central chi-squared distribution. The thermal diffusivity that is found by sampling this distribution will always be biased, and averaging of multiple estimated diffusivities will not necessarily improve the estimation. Confidence bounds are constructed to illustrate the uncertainty in the diffusivity using several formulas that are equivalent in the noiseless case. Finally, a different method of averaging, that reduces the uncertainty significantly, is suggested. The methodology is also extended to the case where damping is included, and it is explained how to include the cylindrical geometry. (paper)
Thermal conductivity and thermal diffusivity are two important physical properties essential for designing any food engineering processes. Recently a new transient plane-source method was developed to measure a variety of materials, but its application in foods has not been documented. Therefore, ...
A residual Monte Carlo method for discrete thermal radiative diffusion
International Nuclear Information System (INIS)
Evans, T.M.; Urbatsch, T.J.; Lichtenstein, H.; Morel, J.E.
2003-01-01
Residual Monte Carlo methods reduce statistical error at a rate of exp(-bN), where b is a positive constant and N is the number of particle histories. Contrast this convergence rate with 1/√N, which is the rate of statistical error reduction for conventional Monte Carlo methods. Thus, residual Monte Carlo methods hold great promise for increased efficiency relative to conventional Monte Carlo methods. Previous research has shown that the application of residual Monte Carlo methods to the solution of continuum equations, such as the radiation transport equation, is problematic for all but the simplest of cases. However, the residual method readily applies to discrete systems as long as those systems are monotone, i.e., they produce positive solutions given positive sources. We develop a residual Monte Carlo method for solving a discrete 1D non-linear thermal radiative equilibrium diffusion equation, and we compare its performance with that of the discrete conventional Monte Carlo method upon which it is based. We find that the residual method provides efficiency gains of many orders of magnitude. Part of the residual gain is due to the fact that we begin each timestep with an initial guess equal to the solution from the previous timestep. Moreover, fully consistent non-linear solutions can be obtained in a reasonable amount of time because of the effective lack of statistical noise. We conclude that the residual approach has great potential and that further research into such methods should be pursued for more general discrete and continuum systems
Subgrid models for mass and thermal diffusion in turbulent mixing
Energy Technology Data Exchange (ETDEWEB)
Sharp, David H [Los Alamos National Laboratory; Lim, Hyunkyung [STONY BROOK UNIV; Li, Xiao - Lin [STONY BROOK UNIV; Gilmm, James G [STONY BROOK UNIV
2008-01-01
We are concerned with the chaotic flow fields of turbulent mixing. Chaotic flow is found in an extreme form in multiply shocked Richtmyer-Meshkov unstable flows. The goal of a converged simulation for this problem is twofold: to obtain converged solutions for macro solution features, such as the trajectories of the principal shock waves, mixing zone edges, and mean densities and velocities within each phase, and also for such micro solution features as the joint probability distributions of the temperature and species concentration. We introduce parameterized subgrid models of mass and thermal diffusion, to define large eddy simulations (LES) that replicate the micro features observed in the direct numerical simulation (DNS). The Schmidt numbers and Prandtl numbers are chosen to represent typical liquid, gas and plasma parameter values. Our main result is to explore the variation of the Schmidt, Prandtl and Reynolds numbers by three orders of magnitude, and the mesh by a factor of 8 per linear dimension (up to 3200 cells per dimension), to allow exploration of both DNS and LES regimes and verification of the simulations for both macro and micro observables. We find mesh convergence for key properties describing the molecular level of mixing, including chemical reaction rates between the distinct fluid species. We find results nearly independent of Reynolds number for Re 300, 6000, 600K . Methodologically, the results are also new. In common with the shock capturing community, we allow and maintain sharp solution gradients, and we enhance these gradients through use of front tracking. In common with the turbulence modeling community, we include subgrid scale models with no adjustable parameters for LES. To the authors' knowledge, these two methodologies have not been previously combined. In contrast to both of these methodologies, our use of Front Tracking, with DNS or LES resolution of the momentum equation at or near the Kolmogorov scale, but without
Thermal conductivity and diffusivity of biomaterials measured with self-heated thermistors
Valvano, J. W.; Cochran, J. R.; Diller, K. R.
1985-05-01
This paper presents an experimental method to measure the thermal conductivity and thermal diffusivity of biomaterials. Self-heated thermistor probes, inserted into the tissue of interest, are used to deliver heat as well as to monitor the rate of heat removal. An empirical calibration procedure allows accurate thermal-property measurements over a wide range of tissue temperatures. Operation of the instrument in three media with known thermal properties shows the uncertainty of measurements to be about 2%. The reproducibility is 0.5% for the thermal-conductivity measurements and 2% for the thermal-diffusivity measurements. Thermal properties were measured in dog, pig, rabbit, and human tissues. The tissues included kidney, spleen, liver, brain, heart, lung, pancreas, colon cancer, and breast cancer. Thermal properties were measured for 65 separate tissue samples at 3, 10, 17, 23, 30, 37, and 45°C. The results show that the temperature coefficient of biomaterials approximates that of water.
Maqsood, Asghari; Anis-ur-Rehman, M.
2013-12-01
Thermal conductivity and thermal diffusivity are two important physical properties for designing any food engineering processes1. The knowledge of thermal properties of the elements, compounds and different materials in many industrial applications is a requirement for their final functionality. Transient plane source (tps) sensors are reported2 to be useful for the simultaneous measurement of thermal conductivity, thermal diffusivity and volumetric heat capacity of insulators, conductor liquids3 and high-TC superconductors4. The tps-sensor consists of a resistive element in the shape of double spiral made of 10 micrometer thick Ni-foils covered on both sides with 25 micrometer thick Kapton. This sensor acts both as a heat source and a resistance thermometer for recording the time dependent temperature increase. From the knowledge of the temperature co-efficient of the metal spiral, the temperature increase of the sensor can be determined precisely by placing the sensor in between two surfaces of the same material under test. This temperature increase is then related to the thermal conductivity, thermal diffusivity and volumetric heat capacity by simple relations2,5. The tps-sensor has been used to measure thermal conductivities from 0.001 Wm-1K-1to 600 Wm-1K-1 and temperature ranges covered from 77K- 1000K. This talk gives the design, advantages and limitations of the tpl-sensor along with its applications to the measurementof thermal properties in a variety of materials.
International Nuclear Information System (INIS)
Maqsood, Asghari; Anis-ur-Rehman, M
2013-01-01
Thermal conductivity and thermal diffusivity are two important physical properties for designing any food engineering processes 1 . The knowledge of thermal properties of the elements, compounds and different materials in many industrial applications is a requirement for their final functionality. Transient plane source (tps) sensors are reported 2 to be useful for the simultaneous measurement of thermal conductivity, thermal diffusivity and volumetric heat capacity of insulators, conductor liquids 3 and high-T C superconductors 4 . The tps-sensor consists of a resistive element in the shape of double spiral made of 10 micrometer thick Ni-foils covered on both sides with 25 micrometer thick Kapton. This sensor acts both as a heat source and a resistance thermometer for recording the time dependent temperature increase. From the knowledge of the temperature co-efficient of the metal spiral, the temperature increase of the sensor can be determined precisely by placing the sensor in between two surfaces of the same material under test. This temperature increase is then related to the thermal conductivity, thermal diffusivity and volumetric heat capacity by simple relations 2,5 . The tps-sensor has been used to measure thermal conductivities from 0.001 Wm −1 K −1 to 600 Wm −1 K −1 and temperature ranges covered from 77K– 1000K. This talk gives the design, advantages and limitations of the tpl-sensor along with its applications to the measurementof thermal properties in a variety of materials
Tuning the thermal diffusivity of silver based nanofluids by controlling nanoparticle aggregation
International Nuclear Information System (INIS)
Agresti, Filippo; Barison, Simona; Battiston, Simone; Pagura, Cesare; Fabrizio, Monica; Colla, Laura; Fedele, Laura
2013-01-01
With the aim of preparing stable nanofluids for heat exchange applications and to study the effect of surfactant on the aggregation of nanoparticles and thermal diffusivity, stable silver colloids were synthesized in water by a green method, reducing AgNO 3 with fructose in the presence of poly-vinylpyrollidone (PVP) of various molecular weights. A silver nanopowder was precipitated from the colloids and re-dispersed at 4 vol% in deionized water. The Ag colloids were characterized by UV–visible spectroscopy, combined dynamic light scattering and ζ-potential measurements, and laser flash thermal diffusivity. The Ag nanopowders were characterized by scanning electron microscopy and thermal gravimetric analysis. It was found that the molecular weight of PVP strongly affects the ζ-potential and the aggregation of nanoparticles, thereby affecting the thermal diffusivity of the obtained colloids. In particular, it was observed that on increasing the molecular weight of PVP the absolute value of the ζ-potential is reduced, leading to increased aggregation of nanoparticles. A clear relation was identified between thermal diffusivity and aggregation, showing higher thermal diffusivity for nanofluids having higher aggregation. A maximum improvement of thermal diffusivity by about 12% was found for nanofluids prepared with PVP having higher molecular weight. (paper)
The effect of a realistic thermal diffusivity on numerical model of a subducting slab
Maierova, P.; Steinle-Neumann, G.; Cadek, O.
2010-12-01
A number of numerical studies of subducting slab assume simplified (constant or only depth-dependent) models of thermal conductivity. The available mineral physics data indicate, however, that thermal diffusivity is strongly temperature- and pressure-dependent and may also vary among different mantle materials. In the present study, we examine the influence of realistic thermal properties of mantle materials on the thermal state of the upper mantle and the dynamics of subducting slabs. On the basis of the data published in mineral physics literature we compile analytical relationships that approximate the pressure and temperature dependence of thermal diffusivity for major mineral phases of the mantle (olivine, wadsleyite, ringwoodite, garnet, clinopyroxenes, stishovite and perovskite). We propose a simplified composition of mineral assemblages predominating in the subducting slab and the surrounding mantle (pyrolite, mid-ocean ridge basalt, harzburgite) and we estimate their thermal diffusivity using the Hashin-Shtrikman bounds. The resulting complex formula for the diffusivity of each aggregate is then approximated by a simpler analytical relationship that is used in our numerical model as an input parameter. For the numerical modeling we use the Elmer software (open source finite element software for multiphysical problems, see http://www.csc.fi/english/pages/elmer). We set up a 2D Cartesian thermo-mechanical steady-state model of a subducting slab. The model is partly kinematic as the flow is driven by a boundary condition on velocity that is prescribed on the top of the subducting lithospheric plate. Reology of the material is non-linear and is coupled with the thermal equation. Using the realistic relationship for thermal diffusivity of mantle materials, we compute the thermal and flow fields for different input velocity and age of the subducting plate and we compare the results against the models assuming a constant thermal diffusivity. The importance of the
Banish, R. Michael; Brantschen, Segolene; Pourpoint, Timothee L.; Wessling, Francis; Sekerka, Robert F.
2003-01-01
This paper presents methodologies for measuring the thermal diffusivity using the difference between temperatures measured at two, essentially independent, locations. A heat pulse is applied for an arbitrary time to one region of the sample; either the inner core or the outer wall. Temperature changes are then monitored versus time. The thermal diffusivity is calculated from the temperature difference versus time. No initial conditions are used directly in the final results.
An accurate method for the determination of unlike potential parameters from thermal diffusion data
International Nuclear Information System (INIS)
El-Geubeily, S.
1997-01-01
A new method is introduced by means of which the unlike intermolecular potential parameters can be determined from the experimental measurements of the thermal diffusion factor as a function of temperature. The method proved to be easy, accurate, and applicable two-, three-, and four-parameter potential functions whose collision integrals are available. The potential parameters computed by this method are found to provide a faith full representation of the thermal diffusion data under consideration. 3 figs., 4 tabs
Ohmic ion temperature and thermal diffusivity profiles from the JET neutron emission profile monitor
Energy Technology Data Exchange (ETDEWEB)
Esposito, B. (ENEA, Frascati (Italy). Centro Ricerche Energia); Marcus, F.B.; Conroy, S.; Jarvis, O.N.; Loughlin, M.J.; Sadler, G.; Belle, P. van (Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking); Adams, J.M.; Watkins, N. (AEA Industrial Technology, Harwell (United Kingdom))
1993-10-01
The JET neutron emission profile monitor was used to study ohmically heated deuterium discharges. The radial profile of the neutron emissivity is deduced from the line-integral data. The profiles of ion temperature, T[sub i], and ion thermal diffusivity, [chi][sub i], are derived under steady-state conditions. The ion thermal diffusivity is higher than, and its scaling with plasma current opposite to, that predicted by neoclassical theory. (author).
Ohmic ion temperature and thermal diffusivity profiles from the JET neutron emission profile monitor
International Nuclear Information System (INIS)
Esposito, B.
1993-01-01
The JET neutron emission profile monitor was used to study ohmically heated deuterium discharges. The radial profile of the neutron emissivity is deduced from the line-integral data. The profiles of ion temperature, T i , and ion thermal diffusivity, χ i , are derived under steady-state conditions. The ion thermal diffusivity is higher than, and its scaling with plasma current opposite to, that predicted by neoclassical theory. (author)
Fusion product measurements of the local ion thermal diffusivity in the PLT tokamak
International Nuclear Information System (INIS)
Heidbrink, W.W.; Lovberg, J.; Strachan, J.D.; Bell, R.E.
1986-03-01
Measurement of the gradient of the d-d fusion rate profile in an ohmic PLT plasma is used to deduce the gradient of the ion temperature and, thus, the local ion thermal diffusivity through an energy balance analysis. The inferred ion diffusivity is consistent with neoclassical theory
Energy Technology Data Exchange (ETDEWEB)
Mendez, M.; Diaz G, J.A.I.; Calderon, A. [CICATA-IPN, Legaria 694, 11500 Mexico D.F. (Mexico)
2006-07-01
We report X-Ray diffraction and SEM analysis in hydroxyapatite obtained in powder form, as well as a SEM analysis in titanium, 316l stainless steel and dense bone in longitudinal and transversal cutting. Moreover, we realized a thermal diffusivity measurement in these materials in order to obtain the thermal compatibility between them. We use the photoacoustic technique in heat transmission configuration in order to obtain the thermal diffusivity values in the samples. Our results show a good thermal compatibility (74%) between hydroxyapatite and bone. Finally, it was obtained a one order of magnitude difference between the thermal diffusivity values of metallic samples and those corresponding values to bone and HA being this difference greater in titanium than in stainless steel, which is important to consider in some biomedical and dental applications. (Author)
International Nuclear Information System (INIS)
Mendez, M.; Diaz G, J.A.I.; Calderon, A.
2006-01-01
We report X-Ray diffraction and SEM analysis in hydroxyapatite obtained in powder form, as well as a SEM analysis in titanium, 316l stainless steel and dense bone in longitudinal and transversal cutting. Moreover, we realized a thermal diffusivity measurement in these materials in order to obtain the thermal compatibility between them. We use the photoacoustic technique in heat transmission configuration in order to obtain the thermal diffusivity values in the samples. Our results show a good thermal compatibility (74%) between hydroxyapatite and bone. Finally, it was obtained a one order of magnitude difference between the thermal diffusivity values of metallic samples and those corresponding values to bone and HA being this difference greater in titanium than in stainless steel, which is important to consider in some biomedical and dental applications. (Author)
Energy Technology Data Exchange (ETDEWEB)
Mendez, M.; Diaz G, J.A.I.; Calderon, A. [CICATA-IPN, 11500 Mexico D.F. (Mexico)
2007-07-01
Full text: We report X-Ray diffraction and SEM analysis in hydroxyapatite obtained in powder form, as well as a SEM analysis in titanium, 316l stainless steel and dense bone in longitudinal and transversal cutting. Moreover, we realized a thermal diffusivity measurement in these materials in order to obtain the thermal compatibility between them. We use the photoacoustic technique in heat transmission configuration in order to obtain the thermal diffusivity values in the samples. Our results show a good thermal compatibility (74%) between hydroxyapatite and bone. Finally, it was obtained a one order of magnitude difference between the thermal diffusivity values of metallic samples and those corresponding values to bone and HA being this difference greater in titanium than in stainless steel, which is important to consider in some biomedical and dental applications. (Author)
Radial thermal diffusivity of toroidal plasma affected by resonant magnetic perturbations
International Nuclear Information System (INIS)
Kanno, Ryutaro; Nunami, Masanori; Satake, Shinsuke; Takamaru, Hisanori; Okamoto, Masao
2012-04-01
We investigate how the radial thermal diffusivity of an axisymmetric toroidal plasma is modified by effect of resonant magnetic perturbations (RMPs), using a drift kinetic simulation code for calculating the thermal diffusivity in the perturbed region. The perturbed region is assumed to be generated on and around the resonance surfaces, and is wedged in between the regular closed magnetic surfaces. It has been found that the radial thermal diffusivity χ r in the perturbed region is represented as χ r = χ r (0) {1 + c r parallel 2 >}. Here r parallel 2 > 1/2 is the strength of the RMPs in the radial directions, means the flux surface average defined by the unperturbed (i.e., original) magnetic field, χ r (0) is the neoclassical thermal diffusivity, and c is a positive coefficient. In this paper, dependence of the coefficient c on parameters of the toroidal plasma is studied in results given by the δ f simulation code solving the drift kinetic equation under an assumption of zero electric field. We find that the dependence of c is given as c ∝ ω b /ν eff m in the low collisionality regime ν eff b , where ν eff is the effective collision frequency, ω b is the bounce frequency and m is the particle mass. In case of ν eff > ω b , the thermal diffusivity χ r evaluated by the simulations becomes close to the neoclassical thermal diffusivity χ r (0) . (author)
Directed Thermal Diffusions through Metamaterial Source Illusion with Homogeneous Natural Media
Directory of Open Access Journals (Sweden)
Guoqiang Xu
2018-04-01
Full Text Available Owing to the utilization of transformation optics, many significant research and development achievements have expanded the applications of illusion devices into thermal fields. However, most of the current studies on relevant thermal illusions used to reshape the thermal fields are dependent of certain pre-designed geometric profiles with complicated conductivity configurations. In this paper, we propose a methodology for designing a new class of thermal source illusion devices for achieving directed thermal diffusions with natural homogeneous media. The employments of the space rotations in the linear transformation processes allow the directed thermal diffusions to be independent of the geometric profiles, and the utilization of natural homogeneous media improve the feasibility. Four schemes, with fewer types of homogeneous media filling the functional regions, are demonstrated in transient states. The expected performances are observed in each scheme. The related performance are analyzed by comparing the thermal distribution characteristics and the illusion effectiveness on the measured lines. The findings obtained in this paper see applications in the development of directed diffusions with minimal thermal loss, used in novel “multi-beam” thermal generation, thermal lenses, solar receivers, and waveguide.
Coupling diffusion and maximum entropy models to estimate thermal inertia
Thermal inertia is a physical property of soil at the land surface related to water content. We have developed a method for estimating soil thermal inertia using two daily measurements of surface temperature, to capture the diurnal range, and diurnal time series of net radiation and specific humidi...
Theory of thermal and charge transport in diffusive normal metal / superconductor junctions
Yokoyama, T.; Tanaka, Y.; Golubov, Alexandre Avraamovitch; Asano, Y.
2005-01-01
Thermal and charge transport in diffusive normal metal (DN)/insulator/s-, d-, and p-wave superconductor junctions are studied based on the Usadel equation with the Nazarov's generalized boundary condition. We derive a general expression of the thermal conductance in unconventional superconducting
Thermal diffusion of hydrogen in zircaloy-2 containing hydrogen beyond terminal solid solubility
International Nuclear Information System (INIS)
Maki, Hideo; Sato, Masao.
1975-01-01
The thermal diffusion of hydrogen is one of causes of uneven hydride precipitation in zircaloy fuel cladding tubes that are used in water reactors. In the diffusion model of hydrogen in zircaloy, the effects of the hydride on the diffusibility of hydrogen has been regarded as negligibly small in comparison with that of hydrogen dissolved in the matrix. Contrary to the indications given by this model, phenomena are often encountered that cannot be explained unless hydride platelets have considerable ostensible diffusibility in zircaloy. In order to determine quantitatively the diffusion characteristics of hydrogen in zircaloy, a thermal diffusion experiment was performed with zircaloy-2 fuel cladding tubes containing hydrogen beyond the terminal solid solubility. In this experiment, a temperature difference of 20 0 --30 0 C was applied between the inside and outside surfaces of the specimen in a thermal simulator. To explain the experimental results, a modified diffusion model is presented, in which the effects of stress are introduced into Markowitz's model with the diffusion of hydrogen in the hydride taken into account. The diffusion equation derived from this model can be written in a form that ostensibly represents direct diffusion of hydride in zircaloy. The apparent diffusion characteristics of the hydride at around 300 0 C are Dsub(p)=2.3x10 5 exp(-32,000/RT), (where R:gas constant, T:temperature) and the apparent heat of transport Qsub(p) =-60,000 cal/mol. The modified diffusion model well explains the experimental results in such respects as reaches a steady state after several hours. (auth.)
Mathematical modelling of pasta dough dynamic viscosity, thermal conductivity and diffusivity
Directory of Open Access Journals (Sweden)
Andrei Ionuţ SIMION
2015-08-01
Full Text Available This work aimed to study the mathematical variation of three main thermodynamic properties (dynamic viscosity, thermal conductivity and thermal diffusivity of pasta dough obtained by mixing wheat semolina and water with dough humidity and deformation speed (for dynamic viscosity, respectively with dough humidity and temperature (for thermal diffusivity and conductivity. The realized regression analysis of existing graphical data led to the development of mathematical models with a high degree of accuracy. The employed statistical tests (least squares, relative error and analysis of variance revealed that the obtained equations are able to describe and predict the tendency of the dough thermodynamic properties.
Thermal diffusivity of diamond nanowires studied by laser assisted atom probe tomography
Arnoldi, L.; Spies, M.; Houard, J.; Blum, I.; Etienne, A.; Ismagilov, R.; Obraztsov, A.; Vella, A.
2018-04-01
The thermal properties of single-crystal diamond nanowires (NWs) have been calculated from first principles but have never been measured experimentally. Taking advantage of the sharp geometry of samples analyzed in a laser assisted atom probe, this technique is used to measure the thermal diffusivity of a single NW at low temperature (ab-initio calculations and confirms that thermal diffusivity in nanoscale samples is lower than in bulk samples. The results impact the design and integration of diamond NWs and nanoneedles in nanoscale devices for heat dissipation.
Energy Technology Data Exchange (ETDEWEB)
Bennacer, R. [Neuville sur Oise, LEEVAM 5 mail Gay Lussac, Cergy-Pontoise Cedex (France); Mohamad, A.A. [CEERE University of Calgary, Department of Mechanical and Manufacturing Engineering, Calgary, Alberta (Canada); Ganaoui, M.El [Faculte des Sciences et Techniques de Limoges, Limoges (France)
2005-02-01
Double-diffusive natural convection within a multilayer anisotropic porous medium is studied numerically and analytically. The domain composed of two horizontal porous layers is subjected to a uniform horizontal heat flux and a vertical mass flux, where only the lower one is thermally anisotropic. Darcy model with classical Boussinesq approximation is used in formulating the mathematical model. The effect of thermal anisotropy and the relative width of the two layers on the flow and transfers is illustrated with characterising the transitions from the diffusive to the convective solution. Results were well compared with respect to a developed analytical approach, based on a parallel flow approximation for thermally anisotropic multilayer media. (orig.)
Correia, A.; Vieira, G.; Ramos, M.
2012-06-01
During the month of January of 2008 a borehole (Permamodel-Gulbenkian 1 — PG1) 26 m deep was drilled on the top of Mount Reina Sofia (275 m a.s.l.) near the Spanish Antarctic Station of Livingston Island, South Shetland Islands. Cores from 1.5 m to about 26 m deep were collected for measuring several physical properties. The objective of the present work is to report the values of the thermal conductivity and the thermal diffusivity that were measured in the cores from the borehole and the heat production that was estimated for the geological formations intercepted by it. Seven cores were selected to measure the thermal conductivity and the thermal diffusivity. The measured values for the thermal conductivity vary from 2.6 W/mK to 3.3 W/mK while the measured values for the thermal diffusivity vary from 1.1 × 10- 6 m2/s to 1.6 × 10- 6 m2/s. Both thermal conductivity and thermal diffusivity, on average, show a slight increase with depth. Average heat production was also estimated for two portions of the borehole: one from 2 to 12 m and the other from 12 to 25 m. A gamma-ray spectrometer was used to estimate the concentrations of uranium, thorium, and potassium of the cores, from which the heat production per unit volume was calculated. The estimated heat production for the first half of the borehole is 2.218 μW/m3 while for the second half it is 2.173 μW/m3; these heat production values are compatible with acidic rock types. Porosity and density were also estimated for the same cores.
Stress in film/substrate system due to diffusion and thermal misfit effects
International Nuclear Information System (INIS)
Shao Shanshan; Xuan Fuzhen; Wang Zhengdong; Tu Shantung
2009-01-01
The stress in film/substrate systems has been analysed taking into consideration the coupling effects of diffusion and thermal misfit within the framework of Fick's second law. The solution of diffusion-induced stress in a film/substrate system involving the thermal misfit stress feedback is developed. The effects of modulus ratios, diffusivity ratios, thickness ratios of the substrate and the film and the partial molar volume of the diffusing component on the stress distribution in the film/substrate system are then discussed with the help of the finite difference method. Results indicate that the stresses in the film/substrate system vary with diffusion time. Diffusion enhances the magnitudes of film stress when the thermal misfit stress is compressive in the film. Furthermore, the absolute values of stress in the film increase with the increasing modulus ratios of the substrate and film, while they reduce with the increasing partial molar volume of the diffusing component and the diffusivity ratio of the substrate and the film.
Thermal diffusion in nanostructured porous InP
International Nuclear Information System (INIS)
Srinivasan, R.; Ramachandran, K.
2008-01-01
Nanostructured porous InP samples were prepared by electrochemical anodic dissolution of InP for various current densities and etching periods. The samples were characterized by SEM and photoluminescence (PL) where a blue shift was observed in PL. Thermal properties studies by photoacoustic (PA) spectroscopy revealed one order decrease in thermal conductivity of porous InP compared to the bulk. Further it is shown that the thermal conductivity of porous InP decreases with decrease in size of the particles. (author)
Measurement of the thermal diffusivity on ceramics and metals using the laser flash method
International Nuclear Information System (INIS)
Blumm, J.; Sauseng, B.
2001-01-01
Full Text: In the past few decades measurement of the thermophysical properties such as thermal expansion, specific heat, thermal diffusivity or thermal conductivity has become increasingly important for industrial applications. One example is the optimization of the heat transfer in industrial assemblies used for automotive or space applications. The thermal diffusivity and thermal conductivity of all components exposed to high and/or sub-ambient temperatures or large temperature gradients should be accurately known. Another well known example is the characterization of materials such as graphite used in nuclear reactors. Furthermore, analysis of solid and liquid metals is of paramount importance for the simulation of casting processes using finite element software programs. Thermal barrier coatings (zirconia) are used more and more often for high-temperature turbine blades. Reducing the thermal conductivity and the heat transfer through such coatings usually allows higher working temperatures and therefore higher efficiency of the gas turbine. These examples clearly demonstrate the need of instrumentation for the accurate measurement of the required thermophysical properties. The laser flash method has been developed to become one of the most commonly used techniques for the measurement of the thermal diffusivity of various kinds of solids and liquids. Easy sample preparation, small sample dimensions, fast measurement times and high accuracy are only some of the advantages of this non-destructive measurement technique. In addition, temperature dependent measurements can easily be realized. Since the development of the method by Parker et al. new routines for processing of the raw data have been established. Analytical mathematical descriptions were found to compensate for heat loss and finite pulse effects. Using modern personal computers and non-linear regression routines, mathematical models can be used to fit the raw data, yielding improved results for thermal
DEFF Research Database (Denmark)
Deepagoda Thuduwe Kankanamge Kelum, Chamindu; Smits, Kathleen; Ramirez, Jamie
2016-01-01
porous media transport properties, key transport parameters such as thermal conductivity and gas diffusivity are particularly important to describe temperature-induced heat transport and diffusion-controlled gas transport processes, respectively. Despite many experimental and numerical studies focusing...... transport models (thermal conductivity, saturated hydraulic conductivity, and gas diffusivity). An existing thermal conductivity model was improved to describe the distinct three-region behavior in observed thermal conductivity–water saturation relations. Applying widely used parametric models for saturated......Detailed characterization of partially saturated porous media is important for understanding and predicting vadose zone transport processes. While basic properties (e.g., particle- and pore-size distributions and soil-water retention) are, in general, essential prerequisites for characterizing most...
CMOS Thermal Ox and Diffusion Furnace: Tystar Tytan 2000
Federal Laboratory Consortium — Description:CORAL Names: CMOS Wet Ox, CMOS Dry Ox, Boron Doping (P-type), Phos. Doping (N-Type)This four-stack furnace bank is used for the thermal growth of silicon...
Sparse estimation of model-based diffuse thermal dust emission
Irfan, Melis O.; Bobin, Jérôme
2018-03-01
Component separation for the Planck High Frequency Instrument (HFI) data is primarily concerned with the estimation of thermal dust emission, which requires the separation of thermal dust from the cosmic infrared background (CIB). For that purpose, current estimation methods rely on filtering techniques to decouple thermal dust emission from CIB anisotropies, which tend to yield a smooth, low-resolution, estimation of the dust emission. In this paper, we present a new parameter estimation method, premise: Parameter Recovery Exploiting Model Informed Sparse Estimates. This method exploits the sparse nature of thermal dust emission to calculate all-sky maps of thermal dust temperature, spectral index, and optical depth at 353 GHz. premise is evaluated and validated on full-sky simulated data. We find the percentage difference between the premise results and the true values to be 2.8, 5.7, and 7.2 per cent at the 1σ level across the full sky for thermal dust temperature, spectral index, and optical depth at 353 GHz, respectively. A comparison between premise and a GNILC-like method over selected regions of our sky simulation reveals that both methods perform comparably within high signal-to-noise regions. However, outside of the Galactic plane, premise is seen to outperform the GNILC-like method with increasing success as the signal-to-noise ratio worsens.
DEFF Research Database (Denmark)
Zhang, Chen; Heiselberg, Per Kvols; Pomianowski, Michal Zbigniew
2016-01-01
An integrated system combining diffuse ceiling ventilation with thermally activated building construction (TABS) was proposed recently. In this system, TABS is encapsulated by diffuse ceiling panel and cannot have directly heat exchange with the room. The aim of this study is to investigate...... the effect of diffuse ceiling panel on the energy performance of TABS in both heat and cooling mode. Experiments are carried out in a full-scale test facility with the integrated system, and the cases without diffuse ceiling are also measured as references. The results indicate that the diffuse ceiling has...... an opposite effect on the heating and cooling capacity of TABS. In addition, a numerical model is built and validated by the measured data. The validated model is further applied to conduct a paramedical study on the materials of the diffuse ceiling panel....
In-Situ Testing of the Thermal Diffusivity of Polysilicon Thin Films
Directory of Open Access Journals (Sweden)
Yi-Fan Gu
2016-10-01
Full Text Available This paper presents an intuitive yet effective in-situ thermal diffusivity testing structure and testing method. The structure consists of two doubly clamped beams with the same width and thickness but different lengths. When the electric current is applied through two terminals of one beam, the beam serves as thermal resistor and the resistance R(t varies as temperature rises. A delicate thermodynamic model considering thermal convection, thermal radiation, and film-to-substrate heat conduction was established for the testing structure. The presented in-situ thermal diffusivity testing structure can be fabricated by various commonly used micro electro mechanical systems (MEMS fabrication methods, i.e., it requires no extra customized processes yet provides electrical input and output interfaces for in-situ testing. Meanwhile, the testing environment and equipment had no stringent restriction, measurements were carried out at normal temperatures and pressures, and the results are relatively accurate.
Measurement of diffusion length of thermal neutrons in concrete
International Nuclear Information System (INIS)
Moser, M.
2007-04-01
The diffusion length of neutrons with a medium energy < 0.025 eV in concrete were determined using 4π-β detector and gamma detectors. Then it was possible to determine how deep can neutrons penetrate diverse concrete construction parts in a reactor in operation, with this method the dismantling process of a reactor can be planned in terms of what parts can be removed without danger and what parts can be assumed still are activated. (nevyjel)
Landfeld, Ales; Strohalm, Jan; Stancl, Jaromir; Houska, Milan
2011-06-01
Our study is directed at the effects of high pressure on the thermal diffusivity of selected food samples - a fresh meat formulation for Swedish meatballs, pork meat pate and tomato puree. Preheated food samples were placed in a copper cell and tested at nominal pressures of 400 and 500 MPa in a high pressure chamber. The thermal diffusivity was estimated from the recorded time course of temperatures (at the center of the food sample, at the wall of the copper cell, and 7.5 mm from the wall) during the high pressure holding time. Measured time-temperature profiles were compared with predictions using the finite-element model to solve the problem of uneven heat conduction in an infinite, solid, linear cylinder using the linear temperature dependence of apparent thermal conductivity. Optimal parameters of the linear temperature dependence of apparent thermal conductivity were evaluated by comparing measured temperatures and temperatures calculated from the model. To minimize differences between measured and calculated temperatures, at the center of the sample, the Marquardt-Levenberg optimization method was used. The thermal diffusivity values of all food samples were linearly correlated with temperature for two levels of pressure. Thermal diffusivity values increased with increased pressure and temperature. † This paper was presented at the XLVIIIth European High Pressure Research Group (EHPRG 48) Meeting at Uppsala (Sweden), 25-29 July 2010.
Thermal diffusion in nanostructured porous InP
Indian Academy of Sciences (India)
Nanostructured porous InP samples were prepared by electrochemical anodic dissolution of InP for various current densities and etching periods. The samples were characterized by SEM and photoluminescence (PL) where a blue shift was observed in PL. Thermal properties studied by photoacoustic (PA) spectroscopy ...
Energetics of melts from thermal diffusion studies. FY 1995 progress report
International Nuclear Information System (INIS)
Lesher, C.E.
1996-01-01
This research program characterizes mass transport by diffusion in geological fluids in response to thermal, solubility, and/or chemical gradients to obtain quantitative information on the thermodynamic and kinetic properties of multicomponent systems. Silicate liquids undergo substantial thermal diffusion (Soret) differentiation, while the response in sulfide, carbonate, and aqueous fluids to an imposed temperature gradient is varied. The experimental observations of this differentiation are used to evaluate the form and quantitative values of solution parameters, and to quantify ordinary diffusion coefficients, heats of transport, and activation energies of multicomponent liquids. The diffusion, solution, and element partition coefficients determined for these geological fluids form a data base for understanding magmatic crystallization behavior and for evaluating geothermal, ore deposit, and nuclear waste isolation potentials
Thermal diffusivity of fuel clad materials: study on D9 alloy
International Nuclear Information System (INIS)
Seenivasan, G.; Balasubramanian, R.; Krishnaiah, M.V.
2003-01-01
Thermal diffusivity of D9 alloy has been measured using a laser flash method in the temperature range of 673 to 1273 K. The samples were taken in the form of 2 mm thick polished discs and some of the discs were annealed at 1073 K in high vacuum. A Nd-YAG laser of pulse width 1 msec and energy 20 J was used for heating. Lead sulphide (PbS) was used as detector. The result indicates that the thermal diffusivity increases with increasing temperature. It has been observed that the thermal diffusivity of 503 and 505 alloys are very similar and their values are very close to that of SS-304. (author)
Power dependence of ion thermal diffusivity at the internal transport barrier in JT-60U
Energy Technology Data Exchange (ETDEWEB)
Sakamoto, Yoshiteru; Suzuki, Takahiro; Ide, Shunsuke [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment] [and others
2002-09-01
The formation properties of an internal transport barrier (ITB) were investigated in a weak positive magnetic shear plasma by changing the neutral beam heating power. The ion thermal diffusivity in the core region shows L-mode state, weak ITB, and strong ITB, depending upon the heating power. Two features of ITB formation were experimentally confirmed. Weak ITB was formed in spite of the absence of an apparent transition in an ion temperature profile. On the other hand, strong ITB appeared after an apparent transition from the weak ITB. In addition, the ion thermal diffusivity at the ITB is correlated to the radial electric field shear. In the case of the weak ITB, ion thermal diffusivity decreased gradually with increases in the radial electric field shear. There exists a threshold in the radial electric field shear, which allows for a change in state from that of weak to strong ITBs. (author)
International Nuclear Information System (INIS)
Savic, S.M.; Aleksic, O.S.; Nikolic, M.V.; Lukovic, D.T.; Pejovic, V.Z.; Nikolic, P.M.
2006-01-01
Thermal diffusivity and electron transport parameters of sintered NTC samples were determined by the photoacoustic (PA) technique. Powder mixtures composed of MnO, NiO, CoO and Fe 2 O 3 were milled to nanometer particle size. NTC discs were dry powder pressed and sintered at different temperatures in the range from 900 deg. C to 1300 deg. C for 30 min. A second group of NTC discs was sintered at 1200 deg. C with the sintering time varying from 30 min to 360 min. These NTC samples were polished and exposed to a chopped laser beam in order to plot a response in the acoustic range. The thermal diffusivity of sintered NTC layers based on a metal oxide powder mixture was measured at room temperature by the photoacoustic technique. An increase of thermal diffusivity with the sintering temperature and time of sintering was observed
Energy Technology Data Exchange (ETDEWEB)
Savic, S.M. [Institute of Technical Sciences of SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Aleksic, O.S. [Center for Multidisciplinary Studies of the University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Nikolic, M.V. [Center for Multidisciplinary Studies of the University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Lukovic, D.T. [Institute of Technical Sciences of SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Pejovic, V.Z. [Center for Multidisciplinary Studies of the University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Nikolic, P.M. [Institute of Technical Sciences of SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia)]. E-mail: nikolic@sanu.ac.yu
2006-07-15
Thermal diffusivity and electron transport parameters of sintered NTC samples were determined by the photoacoustic (PA) technique. Powder mixtures composed of MnO, NiO, CoO and Fe{sub 2}O{sub 3} were milled to nanometer particle size. NTC discs were dry powder pressed and sintered at different temperatures in the range from 900 deg. C to 1300 deg. C for 30 min. A second group of NTC discs was sintered at 1200 deg. C with the sintering time varying from 30 min to 360 min. These NTC samples were polished and exposed to a chopped laser beam in order to plot a response in the acoustic range. The thermal diffusivity of sintered NTC layers based on a metal oxide powder mixture was measured at room temperature by the photoacoustic technique. An increase of thermal diffusivity with the sintering temperature and time of sintering was observed.
International Nuclear Information System (INIS)
Ravi, Jyotsna; Lekshmi, S.; Nair, K.P.R.; Rasheed, T.M.A
2004-01-01
A modified amplitude method to analyze the photothermal probe beam deflection signal for the determination of low thermal diffusivity values of materials is proposed. This simple theoretical model, which is an extension of the amplitude method proposed by Quelin et al., takes into account the dependence of the photothermal signal on the height of the probe beam above the sample surface which affects mirage measurements when the thermal diffusivity of the coupling medium is greater than that of the sample. The present work is similar to the modification to the phase method proposed by Bertolotti et al. for determination of low thermal diffusivity. The method can be applied irrespective of whether the sample is optically transparent or optically opaque and is independent of thickness
International Nuclear Information System (INIS)
Seddeek, M.A.; Abdelmeguid, M.S.
2006-01-01
The effect of radiation and thermal diffusivity on heat transfer over a stretching surface with variable heat flux has been studied. The thermal diffusivity is assumed to vary as a linear function of temperature. The governing partial differential equations have been transformed to ordinary differential equations. The exact analytical solution for the velocity and the numerical solution for the temperature field are given. Numerical solutions are obtained for different values of variable thermal diffusivity, radiation, temperature parameter and Prandtl number
Analytical developments in the Wong-Fung-Tam-Gao radiation model of thermal diffusivity
International Nuclear Information System (INIS)
Lucia, U.; Maino, G.
2004-01-01
When the thermal diffusivity, χ, of a thin film on a substrate is measured by means of the mirage method, the photothermal deflection of the probe beam is determined by the heat radiation field contributed by the film and the substrate, heated by the pump beam. A two-dimensional algorithm is here presented in order to deduce the measure of the diffusivities of the film and the substrate in one set of mirage detection from the experimental data
Xiang-Guo, Meng; Hong-Yi, Fan; Ji-Suo, Wang
2018-04-01
This paper proposes a kind of displaced thermal states (DTS) and explores how this kind of optical field emerges using the entangled state representation. The results show that the DTS can be generated by a coherent state passing through a diffusion channel with the diffusion coefficient ϰ only when there exists κ t = (e^{\\hbar ν /kBT} - 1 )^{-1}. Also, its statistical properties, such as mean photon number, Wigner function and entropy, are investigated.
International Nuclear Information System (INIS)
Najsh, V.E.; Novoselova, T.V.; Sagaradze, I.V.; Kvyatkovskij, B.E.; Fedorov, V.I.; Chernenkov, Yu.P.
1994-01-01
With the use of X-ray diffractometer a study was made into the intensity of diffuse scattering in Ni crystals with FCC lattice. Earlier accomplished quantitative analysis for BCC crystals was extended to FCC lattices. Comparative evaluation was made for cooperative thermal oscillation patterns and corresponding diffuse scattering in crystals of various structures. Measurements on FCC crystals were carried out at room temperature using AgK a lpha-radiation in 96 points of Ni crystal. 8 refs., 4 figs
Barriers to the Diffusion of Solar Thermal Technologies
Energy Technology Data Exchange (ETDEWEB)
NONE
2006-07-01
Despite its considerable potential in household, domestic and industry sectors, the possible contribution of solar heat is often neglected in many academic and institutional energy projections and scenarios. This is best explained by the frequent failure to distinguish heat and work as two different forms of energy transfers. As a result, policy makers in many countries or States have tended to pay lesser attention to solar thermal technologies than to other renewable energy technologies.
Subgrid models for mass and thermal diffusion in turbulent mixing
International Nuclear Information System (INIS)
Lim, H; Yu, Y; Glimm, J; Li, X-L; Sharp, D H
2010-01-01
We propose a new method for the large eddy simulation (LES) of turbulent mixing flows. The method yields convergent probability distribution functions (PDFs) for temperature and concentration and a chemical reaction rate when applied to reshocked Richtmyer-Meshkov (RM) unstable flows. Because such a mesh convergence is an unusual and perhaps original capability for LES of RM flows, we review previous validation studies of the principal components of the algorithm. The components are (i) a front tracking code, FronTier, to control numerical mass diffusion and (ii) dynamic subgrid scale (SGS) models to compensate for unresolved scales in the LES. We also review the relevant code comparison studies. We compare our results to a simple model based on 1D diffusion, taking place in the geometry defined statistically by the interface (the 50% isoconcentration surface between the two fluids). Several conclusions important to physics could be drawn from our study. We model chemical reactions with no closure approximations beyond those in the LES of the fluid variables itself, and as with dynamic SGS models, these closures contain no adjustable parameters. The chemical reaction rate is specified by the joint PDF for temperature and concentration. We observe a bimodal distribution for the PDF and we observe significant dependence on fluid transport parameters.
Effects on nuclear fusion reaction on diffusion and thermal conduction in a magnetoplasma
International Nuclear Information System (INIS)
Sakai, Kazuo; Aono, Osamu.
1976-12-01
In spite of the well spread belief in the field of irreversible thermodynamics, vectorial phenomena couple thermodynamically with the scalar phenomena. Transport coefficients concerning the diffusion and the thermal conduction across a strong magnetic field are calculated in the presence of the deuteron-triton fusion reaction on the basis of the gas kinetic theory. When the reaction takes place, the diffusion increases and the thermal conduction decreases. Effects of the reaction exceed those of the Coulomb collision as the temperature is high enough. (auth.)
FORTRAN program for calculating liquid-phase and gas-phase thermal diffusion column coefficients
International Nuclear Information System (INIS)
Rutherford, W.M.
1980-01-01
A computer program (COLCO) was developed for calculating thermal diffusion column coefficients from theory. The program, which is written in FORTRAN IV, can be used for both liquid-phase and gas-phase thermal diffusion columns. Column coefficients for the gas phase can be based on gas properties calculated from kinetic theory using tables of omega integrals or on tables of compiled physical properties as functions of temperature. Column coefficients for the liquid phase can be based on compiled physical property tables. Program listings, test data, sample output, and users manual are supplied for appendices
Energy Technology Data Exchange (ETDEWEB)
Biro, D.; Preu, R.; Schultz, O.; Peters, S.; Huljic, D.M.; Zickermann, D.; Schindler, R.; Luedemann, R.; Willeke, G. [Fraunhofer Institute for Solar Energy Systems ISE, Freiburg (Germany)
2002-10-01
A novel diffusion system for in-line rapid thermal diffusion is presented. The lamp-heated furnace has a low thermal mass and a metal free transport system based on the walking beam principle. The furnace has been used to process first solar cells with lightly and highly doped emitters respectively. Solar cells with shallow lightly doped emitters show that the emitters processed in the new device can be well passivated. Shallow emitters with sheet resistances of up to 40/sq. have been contacted successfully by means of screen printing and firing through a SiN{sub x} antireflection coating. (author)
On thermal vibration effects in diffusion model calculations of blocking dips
International Nuclear Information System (INIS)
Fuschini, E.; Ugozzoni, A.
1983-01-01
In the framework of the diffusion model, a method for calculating blocking dips is suggested that takes into account thermal vibrations of the crystal lattice. Results of calculations of the diffusion factor and the transverse energy distribution taking into accoUnt scattering of the channeled particles at thermal vibrations of lattice nuclei, are presented. Calculations are performed for α-particles with the energy of 2.12 MeV at 300 K scattered by Al crystal. It is shown that calculations performed according to the above method prove the necessity of taking into account effects of multiple scattering under blocking conditions
Photoacoustic spectroscopy, FTIR spectra and thermal diffusivity investigation of emeraldine pellet
International Nuclear Information System (INIS)
Phing, T.E.; Fanny, C.Y.J.; Wan Mahmood Mat Yunus
2001-01-01
Photoacoustic spectra for both emeraldine base and emeraldine salt in bulk form were measured in the wavelength range of 350 nm to 700 nm. The Fourier transform Infrared spectroscopy (FTIR) have also been studied to determine the structure changes due to the protonation process. For the thermal diffusivity measurement, the open photoacoustic cell (OPC) technique has been used. It was found that the emeraldine salt exhibit higher thermal diffusivity compare to emeraldine base and this is similar to the higher conductivity characteristics of emeraldine salt. (Author)
Measurement of the diffusion length of thermal neutrons in the beryllium oxide
International Nuclear Information System (INIS)
Koechlin, J.C.; Martelly, J.; Duggal, V.P.
1955-01-01
The diffusion length of thermal neutrons in the beryllium oxide has been obtained while studying the spatial distribution of the neutrons in a massive parallelepiped of this matter placed before the thermal column of the reactor core of Saclay. The mean density of the beryllium oxide (BeO) is 2,95 gr/cm 3 , the mean density of the massif is 2,92 gr/cm 3 . The value of the diffusion length, deducted of the done measures, is: L = 32,7 ± 0,5 cm (likely gap). Some remarks are formulated about the influence of the spectral distribution of the neutrons flux used. (authors) [fr
Bench-scale experimental determination of the thermal diffusivity of crushed tuff
International Nuclear Information System (INIS)
Ryder, E.E.; Finley, R.E.; George, J.T.; Ho, C.K.; Longenbaugh, R.S.; Connolly, J.R.
1996-06-01
A bench-scale experiment was designed and constructed to determine the effective thermal diffusivity of crushed tuff. Crushed tuff particles ranging from 12.5 mm to 37.5 mm (0.5 in. to 1.5 in.) were used to fill a cylindrical volume of 1.58 m 3 at an effective porosity of 0.48. Two iterations of the experiment were completed; the first spanning approximately 502 hours and the second 237 hours. Temperatures near the axial heater reached 700 degrees C, with a significant volume of the test bed exceeding 100 degrees C. Three post-test analysis techniques were used to estimate the thermal diffusivity of the crushed tuff. The first approach used nonlinear parameter estimation linked to a one dimensional radial conduction model to estimate thermal diffusivity from the first 6 hours of test data. The second method used the multiphase TOUGH2 code in conjunction with the first 20 hours of test data not only to estimate the crushed tuffs thermal diffusivity, but also to explore convective behavior within the test bed. Finally, the nonlinear conduction code COYOTE-II was used to determine thermal properties based on 111 hours of cool-down data. The post-test thermal diffusivity estimates of 5.0 x 10-7 m 2 /s to 6.6 x 10-7 m 2 /s were converted to effective thermal conductivities and compared to estimates obtained from published porosity-based relationships. No obvious match between the experimental data and published relationships was found to exist; however, additional data for other particle sizes and porosities are needed
Wang, Yanru; Li, Bincheng
2012-11-01
The laser calorimetry (LCA) technique is used to determine simultaneously the absorptances and thermal diffusivities of optical components. An accurate temperature model, in which both the finite thermal conductivity and the finite sample size are taken into account, is employed to fit the experimental temperature data measured with an LCA apparatus for a precise determination of the absorptance and thermal diffusivity via a multiparameter fitting procedure. The uniqueness issue of the multiparameter fitting is discussed in detail. Experimentally, highly reflective (HR) samples prepared with electron-beam evaporation on different substrates (BK7, fused silica, and Ge) are measured with LCA. For the HR-coated sample on a fused silica substrate, the absorptance is determined to be 15.4 ppm, which is close to the value of 17.6 ppm, determined with a simplified temperature model recommended in the international standard ISO11551. The thermal diffusivity is simultaneously determined via multiparameter fitting to be approximately 6.63 × 10-7 m2 · s-1 with a corresponding square variance of 4.8 × 10-4. The fitted thermal diffusivity is in reasonably good agreement with the literature value (7.5 × 10-7 m2 · s -1). Good agreement is also obtained for samples with BK7 and Ge substrates.
Photothermal radiometric determination of thermal diffusivity depth profiles in a dental resin
International Nuclear Information System (INIS)
MartInez-Torres, P; Alvarado-Gil, J J; Mandelis, A
2010-01-01
The depth of curing due to photopolymerization in a commercial dental resin is studied using photothermal radiometry. The sample consists of a thick layer of resin on which a thin metallic layer is deposited guaranteeing full opacity of the sample. In this case, purely thermal-wave inverse problem techniques without the interference of optical profiles can be used. Thermal profiles are obtained by heating the coating with a modulated laser beam and performing a modulation frequency scan. Before each frequency scan, photopolymerization was induced using a high power blue LED. However due to the fact that dental resins are highly light dispersive materials, the polymerization process depends strongly on the optical absorption coefficient inducing a depth dependent thermal diffusion in the sample. It is shown that using a robust depth profilometric inverse method one can reconstruct the thermal diffusivity profile of the photopolymerized resin.
A study on the ocean circulation and thermal diffusion near a nuclear power plant
International Nuclear Information System (INIS)
Shu, Kyung Suk; Han, Moon Hee; Kim, Eun Han; Hwang, Won Tae
1994-08-01
The thermal discharge used with cooling water at nuclear power plant is released to a neighbour sea and it is influenced on marine environment. The thermal discharge released from power plant is mainly transported and diffused by ocean circulation of neighbour sea. So the evaluation for characteristics of ocean circulation around neighbour sea is firstly performed. The purpose of this research is primarily analyzed the thermal diffusion in sea around Yongkwang nuclear power plant. For this viewpoint, fundamental oceanographic data sets are collected and analyzed in Yellow sea, west sea of Korea, sea around Yongkwang. The ocean circulation and the effects of temperature increase by thermal discharge are evaluated using these data. The characteristics of tide is interpreted by the analysis of observed tidal elevation and tidal currents. The characteristics of temperature and salinity is investigated by the long-term observation of Korea Fisheries Research and Development Agency and the short-term observation around Yongkwang. (Author)
Balderas-López, J. A.; Mandelis, Andreas
2003-01-01
The thermal wave resonator cavity (TWRC) was used to measure the thermal properties of vegetable oils. The thermal diffusivity of six commercial vegetable oils (olive, corn, soybean, canola, peanut, and sunflower) was measured by means of this device. A linear relation between both the amplitude and phase as functions of the cavity length for the TWRC was observed and used for the measurements. Three significant figure precisions were obtained. A clear distinction between extra virgin olive oil and other oils in terms of thermal diffusivity was shown. The high measurement precision of the TWRC highlights the potential of this relatively new technique for assessing the quality of this kind of fluids in terms of their thermophysical properties.
On the Effective Thermal Conductivity of Frost Considering Mass Diffusion and Eddy Convection
Kandula, Max
2010-01-01
A physical model for the effective thermal conductivity of water frost is proposed for application to the full range of frost density. The proposed model builds on the Zehner-Schlunder one-dimensional formulation for porous media appropriate for solid-to-fluid thermal conductivity ratios less than about 1000. By superposing the effects of mass diffusion and eddy convection on stagnant conduction in the fluid, the total effective thermal conductivity of frost is shown to be satisfactorily described. It is shown that the effects of vapor diffusion and eddy convection on the frost conductivity are of the same order. The results also point out that idealization of the frost structure by cylindrical inclusions offers a better representation of the effective conductivity of frost as compared to spherical inclusions. Satisfactory agreement between the theory and the measurements for the effective thermal conductivity of frost is demonstrated for a wide range of frost density and frost temperature.
Sakai, Koh; Kobayashi, Yuri; Saito, Tsuguyuki; Isogai, Akira
2016-02-01
High porosity solids, such as plastic foams and aerogels, are thermally insulating. Their insulation performance strongly depends on their pore structure, which dictates the heat transfer process in the material. Understanding such a relationship is essential to realizing highly efficient thermal insulators. Herein, we compare the heat transfer properties of foams and aerogels that have very high porosities (97.3-99.7%) and an identical composition (nanocellulose). The foams feature rather closed, microscale pores formed with a thin film-like solid phase, whereas the aerogels feature nanoscale open pores formed with a nanofibrous network-like solid skeleton. Unlike the aerogel samples, the thermal diffusivity of the foam decreases considerably with a slight increase in the solid fraction. The results indicate that for suppressing the thermal diffusion of air within high porosity solids, creating microscale spaces with distinct partitions is more effective than directly blocking the free path of air molecules at the nanoscale.
Energy Technology Data Exchange (ETDEWEB)
Bretscher, M M [Argonne National Laboratory, Argonne, IL 60439 (United States)
1985-07-01
Simple diffusion theory cannot be used to evaluate control rod worths in thermal neutron reactors because of the strongly absorbing character of the control material. However, reliable control rod worths can be obtained within the framework of diffusion theory if the control material is characterized by a set of mesh-dependent effective diffusion parameters. For thin slab absorbers the effective diffusion parameters can be expressed as functions of a suitably-defined pair of 'blackness coefficients'. Methods for calculating these blackness coefficients in the P1, P3, and P5 approximations, with and without scattering, are presented. For control elements whose geometry does not permit a thin slab treatment, other methods are needed for determining the effective diffusion parameters. One such method, based on reaction rate ratios, is discussed. (author)
Diffusion Mechanisms and Lattice Locations of Thermal-Equilibrium Defects in Si-Ge Alloys
Lyutovich, K; Touboltsev, V; Laitinen, P O; Strohm, A
2002-01-01
It is generally accepted that Ge and Si differ considerably with respect to intrinsic-point-defect-mediated diffusion. In Ge, the native point defects dominating under thermal-equilibium conditions at all solid-state temperatures accessible in diffusion experiments are vacancies, and therefore Ge self-diffusion is vacancy-controlled. In Si, by contrast, self-interstitials and vacancies co-exist in thermal equilibrium. Whereas in the most thoroughly investigated temperature regime above about 1000$^\\circ$C Si self-diffusion is self-interstitial-controlled, it is vacancy-controlled at lower temperatures. According to the scenario displayed above, self-diffusion in Si-Ge alloys is expected to change from an interstitialcy mechanism on the Si side to a vacancy mechanism on the Ge side. Therefore, $^{71}$Ge self-diffusion experiments in Si$_{1- \\it y}$Ge$_{\\it y}$ as a function of composition Y are highly interesting. In a first series of experiments the diffusion of Ge in 0.4 to 10 $\\mu$m thick, relaxed, low-disl...
International Nuclear Information System (INIS)
Komarov, F.F.; Komarov, A.F.; Mironov, A.M.; Makarevich, Yu.V.; Miskevich, S.A.; Zayats, G.M.
2011-01-01
Physical and mathematical models and numerical simulation of the diffusion of implanted impurities during rapid thermal treatment of silicon structures are discussed. The calculation results correspond to the experimental results with a sufficient accuracy. A simulation software system has been developed that is integrated into ATHENA simulation system developed by Silvaco Inc. This program can simulate processes of the low-energy implantation of B, BF 2 , P, As, Sb, C ions into the silicon structures and subsequent rapid thermal annealing. (authors)
Self-thermophoresis and thermal self-diffusion in liquids and gases.
Brenner, Howard
2010-09-01
This paper demonstrates the existence of self-thermophoresis, a phenomenon whereby a virtual thermophoretic force arising from a temperature gradient in a quiescent single-component liquid or gas acts upon an individual molecule of that fluid in much the same manner as a "real" thermophoretic force acts upon a macroscopic, non-Brownian body immersed in that same fluid. In turn, self-thermophoresis acting in concert with Brownian self-diffusion gives rise to the phenomenon of thermal self-diffusion in single-component fluids. The latter furnishes quantitative explanations of both thermophoresis in pure fluids and thermal diffusion in binary mixtures (the latter composed of a dilute solution of a physicochemically inert solute whose molecules are large compared with those of the solvent continuum). Explicitly, the self-thermophoretic theory furnishes a simple expression for both the thermophoretic velocity U of a macroscopic body in a single-component fluid subjected to a temperature gradient ∇T , and the intimately related binary thermal diffusion coefficient D{T} for a two-component colloidal or macromolecular mixture. The predicted expressions U=-D{T}∇T≡-βD{S}∇T and D{T}=βD{S} (with β and D{S} the pure solvent's respective thermal expansion and isothermal self-diffusion coefficients) are each noted to accord reasonably well with experimental data for both liquids and gases. The likely source of systematic deviations of the predicted values of D{T} from these data is discussed. This appears to be the first successful thermodiffusion theory applicable to both liquids and gases, a not insignificant achievement considering that the respective thermal diffusivities and thermophoretic velocities of these two classes of fluids differ by as much as six orders of magnitude.
Thermal diffusion through amalgam and cement base: comparison of in vitro and in vivo measurements.
Tibbetts, V R; Schnell, R J; Swartz, M L; Phillips, R W
1976-01-01
Thermal diffusion was measured in vitro and in vivo through amalgam and amalgam underlaid with bases of zinc phosphate, zinc oxide-eugenol, and calcium hydroxide cements. Although the magnitudes differed, there generally was good agreement between in vitro and in vivo data with respect to the relative rates of thermal diffusivity through amalgam restorations underlaid with bases of each of the three materials. In all tests, both in vitro and in vivo, the zinc oxide-eugenol base proved to be the best thermal insulator. Calcium hydroxide was the next best thermal barrier and was followed by zinc phosphate cement. In vitro tests indicated dentin to be a better thermal insulator than zinc phosphate cement but inferior to the zinc oxide-eugenol and calcium hydroxide base materials used here. Although a method has been presented here for the in vivo assessment of the efficacy of thermal insulating bases and a number of in vivo experiments were conducted, much research remains to be done in this area. Additional investigation is needed to better define the parameters of thermal change beneath various types of restoratives and also to establish more exactly the role of base thickness in providing thermal protection beneath clinical metallic restorations.
International Nuclear Information System (INIS)
Aurangzeb; Ali, Zulqurnain; Gurmani, Samia Faiz; Maqsood, Asghari
2006-01-01
Thermal conductivity, thermal diffusivity and heat capacity per unit volume of porous consolidated igneous rocks have been measured, simultaneously by Gustafsson's probe at room temperature and normal pressure using air as saturant. Data are presented for eleven samples of dunite, ranging in porosity from 0.130 to 0.665% by volume, taken from Chillas near Gilgit, Pakistan. The porosity and density parameters have been measured using American Society of Testing and Materials (ASTM) standards at ambient conditions. The mineral composition of samples has been analysed from their thin sections (petrography). An empirical model to predict the thermal conductivity of porous consolidated igneous rocks is also proposed. The thermal conductivities are predicted by some of the existing models along with the proposed one. It is observed that the values of effective thermal conductivity predicted by the proposed model are in agreement with the experimental thermal conductivity data within 6%
Remote assessment of permeability/thermal diffusivity of consolidated clay sediments
International Nuclear Information System (INIS)
Lovell, M.A.; Ogden, P.
1984-02-01
The aim of this project was to examine the feasibility of predicting marine sediment permeability and thermal diffusivity by remote geophysical observations. For this purpose a modified consolidation cell was developed and constructed and tests on deep sea sediment samples carried out. Results and conclusions of a nineteen month programme are presented. (U.K.)
Thermal diffusivity estimation of the olive oil during its high-pressure treatment
Czech Academy of Sciences Publication Activity Database
Kubásek, M.; Houška, M.; Landfeld, A.; Strohalm, J.; Kamarád, Jiří; Žitný, R.
2006-01-01
Roč. 74, - (2006), s. 286-291 ISSN 0260-8774 R&D Projects: GA MZe QF3287 Institutional research plan: CEZ:AV0Z10100521 Keywords : olive oil * food processing * high pressure * thermal diffusivity Subject RIV: GM - Food Processing Impact factor: 1.696, year: 2006
Energy Technology Data Exchange (ETDEWEB)
Burkes, Douglas [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Casella, Amanda J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Gardner, Levi D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Casella, Andrew M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Huber, Tanja K. [Technische Universität München, Munich (Germany); Breitkreutz, Harald [Technische Universität München, Munich (Germany)
2015-02-11
The Office of Material Management and Minimization Fuel Thermo-physical Characterization Project at Pacific Northwest National Laboratory (PNNL) is tasked with using PNNL facilities and processes to receive irradiated low enriched uranium-molybdenum fuel plate samples and perform analyses in support of the Office of Material Management and Minimization Reactor Conversion Program. This work is in support of the Fuel Development Pillar that is managed by Idaho National Laboratory. A key portion of the scope associated with this project was to measure the thermal properties of fuel segments harvested from plates that were irradiated in the Advanced Test Reactor. Thermal diffusivity of samples prepared from the fuel segments was measured using laser flash analysis. Two models, one developed by PNNL and the other developed by the Technische Universität München (TUM), were evaluated to extract the thermal diffusivity of the uranium-molybdenum alloy from measurements made on the irradiated, layered composites. The experimental data of the “TC” irradiated fuel segment was evaluated using both models considering a three-layer and five-layer system. Both models are in acceptable agreement with one another and indicate that the zirconium diffusion barrier has a minimal impact on the overall thermal diffusivity of the monolithic U-Mo fuel.
DEFF Research Database (Denmark)
Zhang, Chen; Heiselberg, Per Kvols; Pomianowski, Michal Zbigniew
2015-01-01
-scale experiments in a climate chamber. The experimental results indicate that diffuse ceiling can significantly improve thermal comfort in the occupied zone, by reducing draught risk and vertical temperature gradient. The linear function between pressure drop and air change rate points out that the air flow...
Single-particle thermal diffusion of charged colloids: Double-layer theory in a temperature gradient
Dhont, J.K.G.; Briels, Willem J.
2008-01-01
The double-layer contribution to the single-particle thermal diffusion coefficient of charged, spherical colloids with arbitrary double-layer thickness is calculated and compared to experiments. The calculation is based on an extension of the Debye-Hückel theory for the double-layer structure that
Effect of Fe Doping by Thermal in-Diffusion on the Defect Structure of Lithium Niobate
Energy Technology Data Exchange (ETDEWEB)
Mignoni, S; Zaltron, A; Ciampolillo, M V; Bazzan, M; Argiolas, N; Sada, C; Fontana, M D, E-mail: zaltronam@padova.infm.it
2010-11-15
In this work we investigate the iron incorporation in thermally diffused Fe doped LN, by combining two experimental techniques, i.e. micro-Raman spectroscopy and proton induced X rays emission. Our results point out that in substituting for Li, Fe ions induces a decrease of Nb{sub Li} antisite defects and rearrangement of the Nb sublattice.
DEFF Research Database (Denmark)
Zhang, Chen; Yu, Tao; Heiselberg, Per
. And the thermal comfort is analyzed by draught rate vertical temperature gradient and radiant temperature asymmetry. Finally the effect of plenum and diffuse ceiling is discussed. This report mainly focuses on the experiment results and discussions. Therefore, some details about the measurement are not presented...
Thermal diffusivity measurements with a photothermal method of fusion solid breeder materials
International Nuclear Information System (INIS)
Bertolotti, M.; Fabri, L.; Ferrari, A.; Sibilia, C.; Alvani, C.; Casadio, S.
1989-01-01
The Photothermal Deflection method is employed in thermal diffusivity measurements. A theoretical analysis is performed to reduce the influence of arbitrary parameters. Measurements on gamma-lithium aluminate samples as a function of temperatures are performed. (author). 5 refs.; 4 figs
von Aulock, Felix W.; Wadsworth, Fabian B.; Vasseur, Jeremie; Lavallée, Yan
2016-04-01
Heat diffusion in the Earth's crust is critical to fundamental geological processes, such as the cooling of magma, heat dissipation during and following transient heating events (e.g. during frictional heating along faults), and to the timescales of contact metamorphosis. The complex composition and multiphase nature of geomaterials prohibits the accurate modeling of thermal diffusivities and measurements over a range of temperatures are sparse due to the specialized nature of the equipment and lack of instrument availability. We present a novel method to measure the thermal diffusivity of geomaterials such as minerals and rocks with high precision and accuracy using a commercially available differential scanning calorimeter (DSC). A DSC 404 F1 Pegasus® equipped with a Netzsch high-speed furnace was used to apply a step-heating program to corundum single crystal standards of varying thicknesses. The standards were cylindrical discs of 0.25-1 mm thickness with 5.2-6 mm diameter. Heating between each 50 °C temperature interval was conducted at a rate of 100 °C/min over the temperature range 150-1050 °C. Such large heating rates induces temperature disequilibrium in the samples used. However, isothermal segments of 2 minutes were used during which the temperature variably equilibrated with the furnace between the heating segments and thus the directly-measured heat-flow relaxed to a constant value before the next heating step was applied. A finite-difference 2D conductive heat transfer model was used in cylindrical geometry for which the measured furnace temperature was directly applied as the boundary condition on the sample-cylinder surfaces. The model temperature was averaged over the sample volume per unit time and converted to heat-flow using the well constrained thermal properties for corundum single crystals. By adjusting the thermal diffusivity in the model solution and comparing the resultant heat-flow with the measured values, we obtain a model
Institute of Scientific and Technical Information of China (English)
Aliakbar Ghadi; Hassan Saghafian; Mansour Soltanieh; Zhi-gang Yang
2017-01-01
The diffusion mechanism of carbide-forming elements from a molten salt bath to a substrate surface was studied in this research, with particular focus on the processes occurring in the molten bath at the time of coating. Metal, oxide, and metal-oxide baths were investi-gated, and the coating process was performed on H13 steel substrates. Scanning electron microscopy and electron-probe microanalysis were used to study the coated samples and the quenched salt bath. The thickness of the carbide coating layer was 6.5 ± 0.5, 5.2 ± 0.5, or 5.7 ± 0.5μm depending on whether it was deposited in a metal, oxide, or metal-oxide bath, respectively. The phase distribution of vanadium-rich regions was 63%, 57%, and 74% of the total coating deposited in metal, oxide, and metal-oxide baths, respectively. The results obtained using the metal bath indicated that undissolved suspended metal particles deposited onto the substrate surface. Then, carbon subsequently diffused to the sub-strate surface and reacted with the metal particles to form the carbides. In the oxide bath, oxide powders dissolved in the bath with or without binding to the oxidative structure (Na2O) of borax; they were then reduced by aluminum and converted into metal particles. We concluded that, in the metal and oxide baths, the deposition of metal particles onto the sample surface is an important step in the formation of the coating.
Linear thermal expansion, thermal diffusivity and melting temperature of Am-MOX and Np-MOX
International Nuclear Information System (INIS)
Prieur, D.; Belin, R.C.; Manara, D.; Staicu, D.; Richaud, J.-C.; Vigier, J.-F.; Scheinost, A.C.; Somers, J.; Martin, P.
2015-01-01
Highlights: • The thermal properties of Np- and Am-MOX solid solutions were investigated. • Np- and Am-MOX solid solutions exhibit the same linear thermal expansion. • The thermal conductivity of Am-MOX is about 10% higher than that of Np-MOX. • The melting temperatures of Np-MOX and Am-MOX are 3020 ± 30 K and 3005 ± 30 K, respectively. - Abstract: The thermal properties of Np- and Am-MOX solid solution materials were investigated. Their linear thermal expansion, determined using high temperature X-ray diffraction from room temperature to 1973 K showed no significant difference between the Np and the Am doped MOX. The thermal conductivity of the Am-MOX is about 10% higher than that of Np-MOX. The melting temperatures of Np-MOX and Am-MOX, measured using a laser heating self crucible arrangement were 3020 ± 30 K and 3005 ± 30 K, respectively
Irradiation of diffusion couples U-Mo/Al. Thermal calculation
International Nuclear Information System (INIS)
Fortis, Ana M.; Mirandou, Monica; Denis, Alicia C.
2004-01-01
The development of new low enrichment fuel elements for research reactors has lead to obtaining a number of compounds and alloys where the decrease in the enrichment is compensated by a higher uranium density in the fuel material. This has been achieved in particular with the uranium silicides dispersed in an aluminum matrix, where uranium densities about 4.8 g/cm 3 have been reached. Among the diverse candidate alloys, those of U-Mo with molybdenum content in the range 6 to 10 w % can yield, upon dispersion, to uranium densities of about 8 g/cm 3 . The first irradiation experiments employing these alloys in fuel plates, either dispersed in Al or monolithic revealed certain phenomena which are worthy of further studies. Failures have been detected apparently due to the formation of reaction products between the fissile material and the aluminum matrix, which exhibit a poor irradiation behavior. An experiment was designed which final purpose is to irradiate diffusion couples U-Mo/Al in the RA-3 reactor and to analyze the interaction zone at the working temperatures of the fuel elements. A simple device was built consisting of two Al 6063 blocks which press the U-Mo sample in between, located in an Al capsule. The ensemble is placed in a tube, which can be filled with different gases and introduced in the reactor. For safety reasons temperature predictions are necessary before performing the experiment. To this end, the COSMOS code was used. As a preliminary step and in order to test to exactness of the numerical estimations, two irradiations were performed in the RA-1 reactor with He and N 2 as transference gases. The agreement between the measured and calculated temperatures was good, particularly in the case of He and, along with the numerical predictions for the RA-3 reactor, provides a reliable basis to proceed with the following steps. (author)
Modelling thermal radiation in buoyant turbulent diffusion flames
Consalvi, J. L.; Demarco, R.; Fuentes, A.
2012-10-01
This work focuses on the numerical modelling of radiative heat transfer in laboratory-scale buoyant turbulent diffusion flames. Spectral gas and soot radiation is modelled by using the Full-Spectrum Correlated-k (FSCK) method. Turbulence-Radiation Interactions (TRI) are taken into account by considering the Optically-Thin Fluctuation Approximation (OTFA), the resulting time-averaged Radiative Transfer Equation (RTE) being solved by the Finite Volume Method (FVM). Emission TRIs and the mean absorption coefficient are then closed by using a presumed probability density function (pdf) of the mixture fraction. The mean gas flow field is modelled by the Favre-averaged Navier-Stokes (FANS) equation set closed by a buoyancy-modified k-ɛ model with algebraic stress/flux models (ASM/AFM), the Steady Laminar Flamelet (SLF) model coupled with a presumed pdf approach to account for Turbulence-Chemistry Interactions, and an acetylene-based semi-empirical two-equation soot model. Two sets of experimental pool fire data are used for validation: propane pool fires 0.3 m in diameter with Heat Release Rates (HRR) of 15, 22 and 37 kW and methane pool fires 0.38 m in diameter with HRRs of 34 and 176 kW. Predicted flame structures, radiant fractions, and radiative heat fluxes on surrounding surfaces are found in satisfactory agreement with available experimental data across all the flames. In addition further computations indicate that, for the present flames, the gray approximation can be applied for soot with a minor influence on the results, resulting in a substantial gain in Computer Processing Unit (CPU) time when the FSCK is used to treat gas radiation.
Evaluation of Specimen Geometric Effect for Laser Flash Thermal Diffusivity Test
International Nuclear Information System (INIS)
Park, Dae Gyu; Kim, Hee Moon; Song, Woong Sub; Baik, Seung Je; Ryu, Woo Seok; Ahn, Sang Bok; Joo, Young Sun
2012-01-01
KAERI(Korea Atomic Energy Research Institute) is developing a new type of nuclear reactor, the so called 'SMART' (System Integrated Modular Advanced Reactor) reactor. Alloy 690 was selected as the candidate material for the heat exchanger tube of of SMART's steam generator. The SMART R and D is now facing the stage of engineering verification and standard design approval for application of DEMO reactors. Therefore, the material performance under the relevant environment needs to be evaluated. The one of the important material performance issues is thermal conductivity, which the engineering database is necessary for the steam generator design. However, the neutron post irradiation characteristics of alloy 690 are little known. As a result, a PIE (Post Irradiation Examination) of the thermal properties have been plan for a 4 times, so called base line test, 1 st irradiation test, 2 nd and 3 rd irradiation test. But there is some constraint to perform thermal diffusivity test owing to test specimen. Originally thermal diffusivity test are planed using disk shape with 9 mm diameter and 1 mm thick specimen. Due to mismatch of neutron irradiation schedule, thermal diffusivity will be tested by different shape and size specimens at 1 st irradiation test. Therefore, verification of geometric and size effect are necessary for test specimen in order to achieve accurate test results
International Nuclear Information System (INIS)
Perovic, N.L.; Maglic, K.D.; Stanimirovic, A.M.; Vukovic, G.S.
1995-01-01
The study of the thermophysical properties of AISI 321 stainless steel was the last part of work within the IAEA-coordinated Research Programme for the Establishment of a Database of Thermophysical Properties of LW and HW Reactor Materials (IAEA CRP) effected at the Institute of Nuclear Sciences Vinca (NIV). The AISI 321 stainless steel belongs to the group of construction materials whose thermophysical and calorimetric properties have significance for the IAEA CRP. Because there have been few investigations of the thermal properties of this material, the CRP foresaw the need for new measurements, which are reported in this paper. Experimental research performed at NIV consisted of the investigation of thermal diffusivity, electric resistivity, and specific heat capacity of this austenitic stainless steel. The thermal diffusivity was measured by the laser pulse technique, and the elastic resistivity and specific heat capacity were determined by use of millisecond-resolution pulse calorimetry. All measurements were performed from ambient temperature to above 1000 o C, within which temperature range the material maintains its structure and stable thermophysical properties. Values for the thermal conductivity were computed from data on the thermal diffusivity, specific heat capacity, and the room-temperature density. (author)
An extended laser flash technique for thermal diffusivity measurement of high-temperature materials
Shen, F.; Khodadadi, J. M.
1993-01-01
Knowledge of thermal diffusivity data for high-temperature materials (solids and liquids) is very important in analyzing a number of processes, among them solidification, crystal growth, and welding. However, reliable thermal diffusivity versus temperature data, particularly those for high-temperature liquids, are still far from complete. The main measurement difficulties are due to the presence of convection and the requirement for a container. Fortunately, the availability of levitation techniques has made it possible to solve the containment problem. Based on the feasibility of the levitation technology, a new laser flash technique which is applicable to both levitated liquid and solid samples is being developed. At this point, the analysis for solid samples is near completion and highlights of the technique are presented here. The levitated solid sample which is assumed to be a sphere is subjected to a very short burst of high power radiant energy. The temperature of the irradiated surface area is elevated and a transient heat transfer process takes place within the sample. This containerless process is a two-dimensional unsteady heat conduction problem. Due to the nonlinearity of the radiative plus convective boundary condition, an analytic solution cannot be obtained. Two options are available at this point. Firstly, the radiation boundary condition can be linearized, which then accommodates a closed-form analytic solution. Comparison of the analytic curves for the temperature rise at different points to the experimentally-measured values will then provide the thermal diffusivity values. Secondly, one may set up an inverse conduction problem whereby experimentally obtained surface temperature history is used as the boundary conditions. The thermal diffusivity can then be elevated by minimizing the difference between the real heat flux boundary condition (radiation plus convection) and the measurements. Status of an experimental study directed at measuring the
Theory of the Thermal Diffusion of Microgel Particles in Highly Compressed Suspensions
Sokoloff, Jeffrey; Maloney, Craig; Ciamarra, Massimo; Bi, Dapeng
One amazing property of microgel colloids is the ability of the particles to thermally diffuse, even when they are compressed to a volume well below their swollen state volume, despite the fact that they are surrounded by and pressed against other particles. A glass transition is expected to occur when the colloid is sufficiently compressed for diffusion to cease. It is proposed that the diffusion is due to the ability of the highly compressed particles to change shape with little cost in free energy. It will be shown that most of the free energy required to compress microgel particles is due to osmotic pressure resulting from either counterions or monomers inside of the gel, which depends on the particle's volume. There is still, however, a cost in free energy due to polymer elasticity when particles undergo the distortions necessary for them to move around each other as they diffuse through the compressed colloid, even if it occurs at constant volume. Using a scaling theory based on simple models for the linking of polymers belonging to the microgel particles, we examine the conditions under which the cost in free energy needed for a particle to diffuse is smaller than or comparable to thermal energy, which is a necessary condition for particle diffusion. Based on our scaling theory, we predict that thermally activated diffusion should be possible when the mean number of links along the axis along which a distortion occurs is much larger than N 1 / 5, where Nis the mean number of monomers in a polymer chain connecting two links in the gel.
Study of heat and hydraulic diffusions in clays under thermal loading
International Nuclear Information System (INIS)
Djeran, I.
1993-01-01
This study is a cost-sharing research programme on radioactive waste disposal and radioactive waste management. The thermal conductivity of clays is the fundamental parameter which governs the thermal diffusion and the pore pressure of the rock mass under thermal loading. Experiments have been undertaken in a reduced model, respecting representative boundary conditions. They show that the thermal conductivity depends on temperature in an unfavourable sense to the decrease of heat. On the other hand, the outflow of pore water, from the source to the exterior, has a low amplitude. A single model of porous medium allows the observations and illustrates the effects of the variation of conductivity on the behaviour of rock mass. Finally, thanks to the numerical formulations specially developed, we examine the incident of the particularities of proposed models on the thermohydromechanical behaviour of geometrically simple structures subjected to a given thermal loading
Non-Contact Measurement of Thermal Diffusivity in Ion-Implanted Nuclear Materials
Hofmann, F.; Mason, D. R.; Eliason, J. K.; Maznev, A. A.; Nelson, K. A.; Dudarev, S. L.
2015-11-01
Knowledge of mechanical and physical property evolution due to irradiation damage is essential for the development of future fission and fusion reactors. Ion-irradiation provides an excellent proxy for studying irradiation damage, allowing high damage doses without sample activation. Limited ion-penetration-depth means that only few-micron-thick damaged layers are produced. Substantial effort has been devoted to probing the mechanical properties of these thin implanted layers. Yet, whilst key to reactor design, their thermal transport properties remain largely unexplored due to a lack of suitable measurement techniques. Here we demonstrate non-contact thermal diffusivity measurements in ion-implanted tungsten for nuclear fusion armour. Alloying with transmutation elements and the interaction of retained gas with implantation-induced defects both lead to dramatic reductions in thermal diffusivity. These changes are well captured by our modelling approaches. Our observations have important implications for the design of future fusion power plants.
A high-resolution, nanomembrane-based, thermal diffusivity biosensor for living cells
Elafandy, Rami T.; Ooi, Boon S.
2017-01-01
A method for measuring thermal diffusivity/conductivity of a microscale sample includes placing a metallic disk atop the sample, and disposing a nanomembrane over the sample and over the metallic disk so that the nanomembrane, so that the metallic disk, the nanomembrane and the sample are in thermal equilibrium with one another. A laser beam is directed to fall onto the nanomembrane over the sample, while a radiation sensor is operated to detect photoluminescent radiation emitted by the nanomembrane in response to the laser beam. A spectral shift in the detected photoluminescent radiation emitted by the nanomembrane is determined, and thermal diffusivity/conductivity is calculated from the determined spectral shift of the photoluminescence.
Non-Contact Measurement of Thermal Diffusivity in Ion-Implanted Nuclear Materials
International Nuclear Information System (INIS)
Hofmann, F.; Mason, D. R.; Eliason, J. K.; Maznev, A. A.; Nelson, K. A.; Dudarev, S. L.
2015-01-01
Knowledge of mechanical and physical property evolution due to irradiation damage is essential for the development of future fission and fusion reactors. Ion-irradiation provides an excellent proxy for studying irradiation damage, allowing high damage doses without sample activation. Limited ion-penetration-depth means that only few-micron-thick damaged layers are produced. Substantial effort has been devoted to probing the mechanical properties of these thin implanted layers. Yet, whilst key to reactor design, their thermal transport properties remain largely unexplored due to a lack of suitable measurement techniques. Here we demonstrate non-contact thermal diffusivity measurements in ion-implanted tungsten for nuclear fusion armour. Alloying with transmutation elements and the interaction of retained gas with implantation-induced defects both lead to dramatic reductions in thermal diffusivity. These changes are well captured by our modelling approaches. Our observations have important implications for the design of future fusion power plants
An optimised instrument to measure thermal diffusivities of gases with opto-acoustic spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Soldner, J.; Stephan, K. [Institute of Technical Thermodynamics and Thermal Process Engineering, University of Stuttgart, Pfaffenwaldring 9, 70550, Stuttgart (Germany)
2004-11-01
The paper describes the theory and application of opto-acoustics to determine thermal diffusivities of gases. An experimental device, already described in previous papers of the authors [Internat. J. Thermophys. 19 (1998) 1099; Proc. 2. European Thermal Science and 14. UIT National Heat Transfer Conf., 1996, pp. 1071-1078] permitted the detection of thermal diffusivities of gases at moderate pressures with an experimental uncertainty of about {+-}1.25%.Based on the experience gained with this device, a comprehensive error analysis is presented in this paper. It shows how the experimental uncertainties can be considerably reduced to about -0.45 to +0.35%. The parameters for optical cell design are dealt with, as well as the appropriate characteristics, such as frequencies of the modulated laser beam, and the microphone used in the experiment. (authors)
A high-resolution, nanomembrane-based, thermal diffusivity biosensor for living cells
El Afandy, Rami Tarek
2017-07-27
A method for measuring thermal diffusivity/conductivity of a microscale sample includes placing a metallic disk atop the sample, and disposing a nanomembrane over the sample and over the metallic disk so that the nanomembrane, so that the metallic disk, the nanomembrane and the sample are in thermal equilibrium with one another. A laser beam is directed to fall onto the nanomembrane over the sample, while a radiation sensor is operated to detect photoluminescent radiation emitted by the nanomembrane in response to the laser beam. A spectral shift in the detected photoluminescent radiation emitted by the nanomembrane is determined, and thermal diffusivity/conductivity is calculated from the determined spectral shift of the photoluminescence.
Influence of fast alpha diffusion and thermal alpha buildup on tokamak reactor performance
International Nuclear Information System (INIS)
Uckan, N.A.; Tolliver, J.S.; Houlberg, W.A.; Attenberger, S.E.
1988-01-01
The effect of fast alpha diffusion and thermal alpha accumulation on the confinement capability of a candidate Engineering Test Reactor plasma (Tokamak Ignition/Burn Experimental Reactor) in achieving ignition and steady-state driven operation has been assessed using both global and 1-1/2-dimensional transport models. Estimates are made of the threshold for radial diffusion of fast alphas and thermal alpha buildup. It is shown that a relatively low level of radial transport, when combined with large gradients in the fast alpha density, leads to a significant radial flow with a deleterious effect on plasma performance. Similarly, modest levels of thermal alpha concentration significantly influence the ignition and steady-state burn capability
International Nuclear Information System (INIS)
Marinak, M.
1990-02-01
The problem of deducing χ e from measurements of the propagation of a monopole heatpulse is considered. An extended diffusive model, which takes into account perturbed sources and sinks is extended to the case of a monopole heat input. χ e is expressed as a function of two observables, the heat pulse velocity and the radial damping rate. Two simple expressions valid for two different ranges of the radius of the poloidal waist of the beam power profile are given. The expressions are valid in the heat pulse measurement region, extending radially 0.05a beyond the beam power waist to near 0.6a. The inferred χ e is a local value, not an average value of the radial χ e profile. 7 refs., 6 figs., 1 tab
International Nuclear Information System (INIS)
Kubaschewski, O.
1983-01-01
The diffusion rate values of titanium, its compounds and alloys are summarized and tabulated. The individual chemical diffusion coefficients and self-diffusion coefficients of certain isotopes are given. Experimental methods are listed which were used for the determination of diffusion coefficients. Some values have been taken over from other studies. Also given are graphs showing the temperature dependences of diffusion and changes in the diffusion coefficient with concentration changes
International Nuclear Information System (INIS)
Durham, W.B.; Abey, A.E.
1981-11-01
Measurements of thermal conductivity and thermal diffusivity have been made on two samples of Climax Stock quartz monzonite at pressures between 3 and 50 MPa and temperatures between 300 and 523 0 K. Following those measurements the apparatus was calibrated with respect to the thermal conductivity measurement using a reference standard of fused silica. Corrected thermal conductivity of the rock indicates a value at room temperature of 2.60 +- 0.25 W/mK at 3 MPa increasing linearly to 2.75 +- 0.25 W/mK at 50 MPa. These values are unchanged (+- 0.07 W/mK) by heating under 50-MPa pressure to as high as 473 0 K. The conductivity under 50-MPa confining pressure falls smoothly from 2.75 +- 0.25 W/mK at 313 0 K to 2.15 +- 0.25 W/mK at 473 0 K. Thermal diffusivity at 300 0 K was found to be 1.2 +- 0.4 X 10 -6 m 2 /s and shows approximately the same pressure and temperature dependencies as the thermal conductivity
Energy Technology Data Exchange (ETDEWEB)
Durham, W.B.; Abey, A.E.
1981-11-01
Measurements of thermal conductivity and thermal diffusivity have been made on two samples of Climax Stock quartz monzonite at pressures between 3 and 50 MPa and temperatures between 300 and 523{sup 0}K. Following those measurements the apparatus was calibrated with respect to the thermal conductivity measurement using a reference standard of fused silica. Corrected thermal conductivity of the rock indicates a value at room temperature of 2.60 +- 0.25 W/mK at 3 MPa increasing linearly to 2.75 +- 0.25 W/mK at 50 MPa. These values are unchanged (+- 0.07 W/mK) by heating under 50-MPa pressure to as high as 473{sup 0}K. The conductivity under 50-MPa confining pressure falls smoothly from 2.75 +- 0.25 W/mK at 313{sup 0}K to 2.15 +- 0.25 W/mK at 473{sup 0}K. Thermal diffusivity at 300{sup 0}K was found to be 1.2 +- 0.4 X 10{sup -6} m{sup 2}/s and shows approximately the same pressure and temperature dependencies as the thermal conductivity.
Thermal fluid characteristics in diffusion flame formed by coaxial flow configuration
Energy Technology Data Exchange (ETDEWEB)
Torii, S. [Kumamoto Univ., Kumamoto (Japan). Dept. of Mechanical Engineering and Materials Science
2005-07-01
A numerical and experimental study was performed on the thermal transport phenomena of turbulent jet diffusion flames formed by coaxial flow configuration. Consideration was given to the effect of the flow rates of air and fuel on the flame morphology. It was noted that as the air flow rate increases, the augmentation of flow shear effect exerted on the shear layer form between the flame jet and the air flow induced the fuel-to-air mixture. Thermal diffusion was amplified with an increase in the Reynolds number. As the velocity ratio was increased, the streamwise velocity gradient along the radial axis was intensified, resulting in an amplification of thermal diffusion. Details of the experimental apparatus and method were provided, along with governing equations and numerical methods. It was concluded that the suppression of the flame length and an extension of flame blowoff limit caused an annular jet diffusion flame. An increase in the velocity ratio of air to fuel showed the blue flame. When cold and hot gases are injected along the same direction from the annular channel, the flow pattern and isotherms are affected by the velocity ratio. The streamwise velocity gradient along the r axis was intensified with an increase in N. The trend became larger in the vicinity of the injection nozzle. 15 refs., 9 figs.
Effective Thermal Conductivity and Diffusivity of Containment Wall for Nuclear Power Plant OPR1000
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Hyung Gyun Noh
2017-04-01
Full Text Available The goal of this study is to evaluate the effective thermal conductivity and diffusivity of containment walls as heat sinks or passive cooling systems during nuclear power plant (NPP accidents. Containment walls consist of steel reinforced concrete, steel liners, and tendons, and provide the main thermal resistance of the heat sinks, which varies with the volume fraction and geometric alignment of the rebar and tendons, as well as the temperature and chemical composition. The target geometry for the containment walls of this work is the standard Korean NPP OPR1000. Sample tests and numerical simulations are conducted to verify the correlations for models with different densities of concrete, volume fractions, and alignments of steel. Estimation of the effective thermal conductivity and diffusivity of the containment wall models is proposed. The Maxwell model and modified Rayleigh volume fraction model employed in the present work predict the experiment and finite volume method (FVM results well. The effective thermal conductivity and diffusivity of the containment walls are summarized as functions of density, temperature, and the volume fraction of steel for the analysis of the NPP accidents.
Effective thermal conductivity and diffusivity of containment wall for nuclear power plant OPR1000
Energy Technology Data Exchange (ETDEWEB)
Noh, Hyung Gyun; Park, Hyun Sun [Div. of Advanced Nuclear Engineering (DANE), Pohang University of Science and Technology (POSTECH), Pohang (Korea, Republic of); Lee, Jong Hwi; Kang, Hie Chan [Mechanical Engineering Div., Kunsan National University (KNU), Gunsan (Korea, Republic of)
2017-04-15
The goal of this study is to evaluate the effective thermal conductivity and diffusivity of containment walls as heat sinks or passive cooling systems during nuclear power plant (NPP) accidents. Containment walls consist of steel reinforced concrete, steel liners, and tendons, and provide the main thermal resistance of the heat sinks, which varies with the volume fraction and geometric alignment of the rebar and tendons, as well as the temperature and chemical composition. The target geometry for the containment walls of this work is the standard Korean NPP OPR1000. Sample tests and numerical simulations are conducted to verify the correlations for models with different densities of concrete, volume fractions, and alignments of steel. Estimation of the effective thermal conductivity and diffusivity of the containment wall models is proposed. The Maxwell model and modified Rayleigh volume fraction model employed in the present work predict the experiment and finite volume method (FVM) results well. The effective thermal conductivity and diffusivity of the containment walls are summarized as functions of density, temperature, and the volume fraction of steel for the analysis of the NPP accidents.
Thermal conductivity, diffusivity and expansion of Avery Island salt at pressure and temperature
International Nuclear Information System (INIS)
Durham, W.B.; Abey, A.E.; Trimmer, D.A.
1981-01-01
Preliminary data on the thermal propertes of a course-grained rock salt from Avery Island, Louisiana, indicate that hydrostatic pressure to 50 MPa has little effect on the thermal conductivity, diffusivity and linear expansion at temperatures from 300 to 573 K. The measurements were made in a new apparatus under conditions of true hydrostatic loading. At room temperature and effective confining pressure increasing from 10 to 50 MPa, thermal conductivity and diffusivity are constant at roughly 7 W/mK and 3.6 x 10 -6 m 2 /s, respectively. At 50 MPa and temperature increasing from 300 to 573 K, both conductivity and diffusivity drop by a factor of 2. Thermal linear expansion at 0 MPa matches that at 50 MPa, increasing from roughly 4.2 x 10 -5 /K at 300 K to 5.5 x 10 -5 /K at 573 K. The lack of a pressure effect on all three properties is confirmed by previous work. Simple models of microcracking suggest that among common geological materials the lack of pressure dependence is unique to rock salt
Thermal conductivity, diffusivity and expansion of Avery Island salt at pressure and temperature
International Nuclear Information System (INIS)
Durham, W.B.; Abey, A.E.; Trimmer, D.A.
1980-01-01
Preliminary data on the thermal properties of a coarse-grained rock salt from Avery Island, Louisiana, indicates that hydrostatic pressure to 50 MPa has little effect on the thermal conductivity, diffusivity and linear expansion at temperatures from 300 to 573 K. The measurements were made in a new apparatus under conditions of true hydrostatic loading. At room temperature and effective confining pressure increasing from 10 to 50 MPa, thermal conductivity and diffusivity are constant at roughly 7W/mK and 3.6 x 10 -6 m 2 /s, respectively. At 50 MPa and temperature increasing from 300 to 573K, both conductivity and diffusivity drop by a factor of 2. Thermal linear expansion at 0 MPa matches that at 50 MPa, increasing from roughly 4.2 x 10 -5 /K at 300 K to 5.5 x 10 -5 at 573 K. The lack of a pressure effect on all three properties is confirmed by previous work. Simple models of microcracking suggest that among common geological materials the lack of pressure dependence is unique to rock salt
Thermal diffusivity measurements between 0 0C and 2000 0C: application to UO2
International Nuclear Information System (INIS)
Van Craeynest, J.C.; Weilbacher, J.C.; Lallement, R.
1969-01-01
We have built two types of apparatus to measure the thermal diffusivity of ceramic fuels. The first apparatus, based on Angstrom's method, operates between 0 deg. C and 1000 deg. C. Satisfactory results have been obtained for iron, nickel and molybdenum. The other apparatus, based on Cowan's method, operates between 1000 deg. C and 2000 deg. C on thin slabs. The thermal conductivity of UO 2 has been measured from 0 deg. C to 2000 deg. C. There is a good agreement between our results and the well known values for UO 2 . (authors) [fr
Thermal diffusivity of a metallic thin layer using the time-domain thermo reflectance technique
International Nuclear Information System (INIS)
Battaglia, J-L; Kusiak, A; Rossignol, C; Chigarev, N
2007-01-01
The time domain thermo reflectance (TDTR) is widely used in the field of acoustic and thermal characterization of thin layers at the nano and micro scale. In this paper, we propose to derive a simple analytical expression of the thermal diffusivity of the layer. This relation is based on the analytical solution of one-dimensional heat transfer in the medium using integral transforms. For metals, the two-temperature model shows that the capacitance effect at the short times is essentially governed by the electronic contribution
Accuracy analysis of the thermal diffusivity measurement of molten salts by stepwise heating method
International Nuclear Information System (INIS)
Kato, Yoshio; Furukawa, Kazuo
1976-11-01
The stepwise heating method for measuring thermal diffusivity of molten salts is based on the electrical heating of a thin metal plate as a plane heat source in the molten salt. In this method, the following estimations on error are of importance: (1) thickness effect of the metal plate, (2) effective length between the plate and a temperature measuring point and (3) effect of the noise on the temperature rise signal. In this report, a measuring apparatus is proposed and measuring conditions are suggested on the basis of error estimations. The measurements for distilled water and glycerine were made first to test the performance; the results agreed well with standard values. The thermal diffusivities of molten NaNO 3 at 320-380 0 C and of molten Li 2 BeF 4 at 470-700 0 C were measured. (auth.)
International Nuclear Information System (INIS)
Smedley-Stevenson, Richard P.; McClarren, Ryan G.
2015-01-01
This paper attempts to unify the asymptotic diffusion limit analysis of thermal radiation transport schemes, for a linear-discontinuous representation of the material temperature reconstructed from cell centred temperature unknowns, in a process known as ‘source tilting’. The asymptotic limits of both Monte Carlo (continuous in space) and deterministic approaches (based on linear-discontinuous finite elements) for solving the transport equation are investigated in slab geometry. The resulting discrete diffusion equations are found to have nonphysical terms that are proportional to any cell-edge discontinuity in the temperature representation. Based on this analysis it is possible to design accurate schemes for representing the material temperature, for coupling thermal radiation transport codes to a cell centred representation of internal energy favoured by ALE (arbitrary Lagrange–Eulerian) hydrodynamics schemes
Energy Technology Data Exchange (ETDEWEB)
Smedley-Stevenson, Richard P., E-mail: richard.smedley-stevenson@awe.co.uk [AWE PLC, Aldermaston, Reading, Berkshire, RG7 4PR (United Kingdom); Department of Earth Science and Engineering, Imperial College London, SW7 2AZ (United Kingdom); McClarren, Ryan G., E-mail: rmcclarren@ne.tamu.edu [Department of Nuclear Engineering, Texas A & M University, College Station, TX 77843-3133 (United States)
2015-04-01
This paper attempts to unify the asymptotic diffusion limit analysis of thermal radiation transport schemes, for a linear-discontinuous representation of the material temperature reconstructed from cell centred temperature unknowns, in a process known as ‘source tilting’. The asymptotic limits of both Monte Carlo (continuous in space) and deterministic approaches (based on linear-discontinuous finite elements) for solving the transport equation are investigated in slab geometry. The resulting discrete diffusion equations are found to have nonphysical terms that are proportional to any cell-edge discontinuity in the temperature representation. Based on this analysis it is possible to design accurate schemes for representing the material temperature, for coupling thermal radiation transport codes to a cell centred representation of internal energy favoured by ALE (arbitrary Lagrange–Eulerian) hydrodynamics schemes.
Hybrid transport and diffusion modeling using electron thermal transport Monte Carlo SNB in DRACO
Chenhall, Jeffrey; Moses, Gregory
2017-10-01
The iSNB (implicit Schurtz Nicolai Busquet) multigroup diffusion electron thermal transport method is adapted into an Electron Thermal Transport Monte Carlo (ETTMC) transport method to better model angular and long mean free path non-local effects. Previously, the ETTMC model had been implemented in the 2D DRACO multiphysics code and found to produce consistent results with the iSNB method. Current work is focused on a hybridization of the computationally slower but higher fidelity ETTMC transport method with the computationally faster iSNB diffusion method in order to maximize computational efficiency. Furthermore, effects on the energy distribution of the heat flux divergence are studied. Work to date on the hybrid method will be presented. This work was supported by Sandia National Laboratories and the Univ. of Rochester Laboratory for Laser Energetics.
A technique to measure the thermal diffusivity of high-Tc superconductors
International Nuclear Information System (INIS)
Powers, C.E.
1991-01-01
High T(sub c) superconducting electrical current leads and ground straps will be used in cryogenic coolers in future NASA Goddard Space Flight Center missions. These superconducting samples are long, thin leads with a typical diameter of two millimeters. A longitudinal method is developed to measure the thermal diffusivity of candidate materials for this application. This technique uses a peltier junction to supply an oscillatory heat wave into one end of a sample and will use low mass thermocouples to follow the heat wave along the sample. The thermal diffusivity is calculated using both the exponential decay of the heat wave and the phase shift to the wave. Measurements are performed in a cryostat between 10 K and room temperature
Energy Technology Data Exchange (ETDEWEB)
Motozawa, Masaaki, E-mail: motozawa.masaaki@shizuoka.ac.jp [Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu-shi, Shizuoka 432-8561 (Japan); Muraoka, Takashi [Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu-shi, Shizuoka 432-8561 (Japan); Motosuke, Masahiro, E-mail: mot@rs.tus.ac.jp [Tokyo University of Science, 6-3-1 Niijuku, Katsushika-ku, Tokyo 125-8585 (Japan); Fukuta, Mitsuhiro, E-mail: fukuta.mitsuhiro@shizuoka.ac.jp [Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu-shi, Shizuoka 432-8561 (Japan)
2017-04-15
It can be expected that the thermal diffusivity of a magnetic fluid varies from time to time after applying a magnetic field because of the growth of the inner structure of a magnetic fluid such as chain-like clusters. In this study, time series variation of the thermal diffusivity of a magnetic fluid caused by applying a magnetic field was investigated experimentally. For the measurement of time series variation of thermal diffusivity, we attempted to apply the forced Rayleigh scattering method (FRSM), which has high temporal and high spatial resolution. We set up an optical system for the FRSM and measured the thermal diffusivity. A magnetic field was applied to a magnetic fluid in parallel and perpendicular to the heat flux direction, and the magnetic field intensity was 70 mT. The FRSM was successfully applied to measurement of the time series variation of the magnetic fluid from applying a magnetic field. The results show that a characteristic configuration in the time series variation of the thermal diffusivity of magnetic fluid was obtained in the case of applying a magnetic field parallel to the heat flux direction. In contrast, in the case of applying a magnetic field perpendicular to the heat flux, the thermal diffusivity of the magnetic fluid hardly changed during measurement. - Highlights: • Thermal diffusivity was measured by forced Rayleigh scattering method (FRSM). • FRSM has high temporal and high spatial resolutions for measurement. • We attempted to apply FRSM to magnetic fluid (MF). • Time series variation of thermal diffusivity of MF was successfully measured by FRSM. • Anisotropic thermal diffusivity of magnetic fluid was also successfully confirmed.
Thermally activated reaction–diffusion-controlled chemical bulk reactions of gases and solids
Directory of Open Access Journals (Sweden)
S. Möller
2015-01-01
Full Text Available The chemical kinetics of the reaction of thin films with reactive gases is investigated. The removal of thin films using thermally activated solid–gas to gas reactions is a method to in-situ control deposition inventory in vacuum and plasma vessels. Significant scatter of experimental deposit removal rates at apparently similar conditions was observed in the past, highlighting the need for understanding the underlying processes. A model based on the presence of reactive gas in the films bulk and chemical kinetics is presented. The model describes the diffusion of reactive gas into the film and its chemical interaction with film constituents in the bulk using a stationary reaction–diffusion equation. This yields the reactive gas concentration and reaction rates. Diffusion and reaction rate limitations are depicted in parameter studies. Comparison with literature data on tokamak co-deposit removal results in good agreement of removal rates as a function of pressure, film thickness and temperature.
Thermal diffuse scattering in time-of-flight neutron diffraction studied on SBN single crystals
International Nuclear Information System (INIS)
Prokert, F.; Savenko, B.N.; Balagurov, A.M.
1994-01-01
At time-of-flight (TOF) diffractometer D N-2, installed at the pulsed reactor IBR-2 in Dubna, Sr x Ba 1-x Nb 2 O 6 mixed single crystals (SBN-x) of different compositions (0.50 < x< 0.75) were investigated between 15 and 773 K. The diffraction patterns were found to be strongly influenced by the thermal diffuse scattering (TDS). The appearance of the TDS from the long wavelength acoustic models of vibration in single crystals is characterized by the ratio of the velocity of sound to the velocity of neutron. Due to the nature of the TOF Laue diffraction technique used on D N-2, the TDS around Bragg peaks has rather a complex profile. An understanding of the TDS close to Bragg peaks is essential in allowing the extraction of the diffuse scattering occurring at the diffuse ferroelectric phase transition in SBN crystals. 11 refs.; 9 figs.; 1 tab. (author)
Gavrilin, A V
2001-01-01
Low temperature composite superconductors stabilized with extra large cross-section pure aluminum are currently in use for the Large Helical Device in Japan, modern big detectors such as ATLAS at CERN, and other large magnets. In these types of magnet systems, the rated average current density is not high and the peak field in a region of interest is about 2-4 T. Aluminum stabilized superconductors result in high stability margins and relatively long quench times. Appropriate quench analyses, both for longitudinal and transverse propagation, have to take into account a rather slow diffusion of current from the superconductor into the thick aluminum stabilizer. An exact approach to modeling of the current diffusion would be based on directly solving the Maxwell's equations in parallel with thermal diffusion and conduction relations. However, from a practical point of view, such an approach should be extremely time consuming due to obvious restrictions of computation capacity. At the same time, there exist cert...
Effects of thermal vapor diffusion on seasonal dynamics of water in the unsaturated zone
Milly, Paul C.D.
1996-01-01
The response of water in the unsaturated zone to seasonal changes of temperature (T) is determined analytically using the theory of nonisothermal water transport in porous media, and the solutions are tested against field observations of moisture potential and bomb fallout isotopic (36Cl and 3H) concentrations. Seasonally varying land surface temperatures and the resulting subsurface temperature gradients induce thermal vapor diffusion. The annual mean vertical temperature gradient is close to zero; however, the annual mean thermal vapor flux is downward, because the temperature‐dependent vapor diffusion coefficient is larger, on average, during downward diffusion (occurring at high T) than during upward diffusion (low T). The annual mean thermal vapor flux is shown to decay exponentially with depth; the depth (about 1 m) at which it decays to e−1of its surface value is one half of the corresponding decay depth for the amplitude of seasonal temperature changes. This depth‐dependent annual mean flux is effectively a source of water, which must be balanced by a flux divergence associated with other transport processes. In a relatively humid environment the liquid fluxes greatly exceed the thermal vapor fluxes, so such a balance is readily achieved without measurable effect on the dynamics of water in the unsaturated zone. However, if the mean vertical water flux through the unsaturated zone is very small (theoretical prediction is supported by long‐term field measurements in the Chihuahuan Desert. The analysis also makes predictions, confirmed by the field observations, regarding the seasonal variations of matric potential at a given depth. The conceptual model of unsaturated zone water transport developed here implies the possibility of near‐surface trapping of any aqueous constituent introduced at the surface.
International Nuclear Information System (INIS)
Bertolotti, M.; Liakhou, G.; Li Voti, R.; Paoloni, S.; Sibilia, C.; Sparvieri, N.
1995-01-01
A cryostatic setup is described to perform photothermal deflection measurements from room temperature to 77 K. The setup uses gaseous nitrogen as a medium where the photodeflection is produced. The ability of the system to work is demonstrated presenting some measurements of thermal diffusivity of high-temperature superconductor samples and of yttrium-iron garnets with variable aluminum content. copyright 1995 American Institute of Physics
Lasing and thermal characteristics of Yb:YAG/YAG composite with atomic diffusion bonding
Czech Academy of Sciences Publication Activity Database
Nagisetty, Siva S.; Severová, Patricie; Miura, Taisuke; Smrž, Martin; Kon, H.; Uomoto, M.; Shimatsu, T.; Kawasaki, M.; Higashiguchi, T.; Endo, Akira; Mocek, Tomáš
2017-01-01
Roč. 14, č. 1 (2017), 1-6, č. článku 015001. ISSN 1612-2011 R&D Projects: GA MŠk LM2015086; GA MŠk LO1602 Institutional support: RVO:68378271 Keywords : composite Yb:YAG ceramic * atomic diffusion bonding * thermal effects Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 2.537, year: 2016
Determination of the ion thermal diffusivity from neutron emission profiles in decay
Energy Technology Data Exchange (ETDEWEB)
Sasao, M. (National Inst. for Fusion Science, Nagoya (Japan)); Adams, J.M. (AEA Industrial Technology, Harwell (United Kingdom)); Conroy, S.; Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Belle, P. van (Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking)
1994-01-01
Spatial profiles of the neutron emission from deuterium plasmas are routinely obtained at the Joint European Torus (JET) using the line-integrated signals measured with a multichannel instrument. It is shown that the manner in which these profiles relax following the termination of strong heating with neutral beam injection (NBI) permits the local thermal diffusivity ([chi][sub i]) to be obtained with an accuracy of about 20%. (author).
Determination of the ion thermal diffusivity from neutron emission profiles in decay
International Nuclear Information System (INIS)
Sasao, M.; Adams, J.M.; Conroy, S.; Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Belle, P. van
1994-01-01
Spatial profiles of the neutron emission from deuterium plasmas are routinely obtained at the Joint European Torus (JET) using the line-integrated signals measured with a multichannel instrument. It is shown that the manner in which these profiles relax following the termination of strong heating with neutral beam injection (NBI) permits the local thermal diffusivity (χ i ) to be obtained with an accuracy of about 20%. (author)
Ma, Hao; Tian, Zhiting
2018-01-10
Tapered bottlebrush polymers have novel nanoscale polymer architecture. Using nonequilibrium molecular dynamics simulations, we showed that these polymers have the unique ability to generate thermal rectification in a single polymer molecule and offer an exceptional platform for unveiling different heat conduction regimes. In sharp contrast to all other reported asymmetric nanostructures, we observed that the heat current from the wide end to the narrow end (the forward direction) in tapered bottlebrush polymers is smaller than that in the opposite direction (the backward direction). We found that a more disordered to less disordered structural transition within tapered bottlebrush polymers is essential for generating nonlinearity in heat conduction for thermal rectification. Moreover, the thermal rectification ratio increased with device length, reaching as high as ∼70% with a device length of 28.5 nm. This large thermal rectification with strong length dependence uncovered an unprecedented phenomenon-diffusive thermal transport in the forward direction and ballistic thermal transport in the backward direction. This is the first observation of radically different transport mechanisms when heat flow direction changes in the same system. The fundamentally new knowledge gained from this study can guide exciting research into nanoscale organic thermal diodes.
Directory of Open Access Journals (Sweden)
Boričić Aleksandar Z.
2016-01-01
Full Text Available The unsteady 2-D dynamic, thermal, and diffusion magnetohydrodynamic laminar boundary layer flow over a horizontal cylinder of incompressible and electrical conductivity fluid, in mixed convection in the presence of heat source or sink and chemical reactions. The present magnetic field is homogenous and perpendicular to the body surface. It is assumed that induction of outer magnetic field is a function of longitudinal co-ordinate outer electric field is neglected and magnetic Reynolds number is significantly lower than one, i. e. considered the problem is in approximation without induction. Fluid electrical conductivity is constant. Free stream velocity, temperature, and concentration on the body are functions of longitudinal co-ordinate. The developed governing boundary layer equations and associated boundary conditions are made dimensionless using a suitable similarity transformation and similarity parameters. System of non-dimensionless equations is solved using the implicit finite difference three-diagonal and iteration method. Numerical results are obtained and presented for different Prandtl, Eckart, and Schmidt numbers, and values: magnetic parameter, temperature, and diffusion parameters, buoyancy temperature parameters, thermal parameter, and chemical reaction parameter. Variation of velocity profiles, temperature and diffusion distributions, and many integral and differential characteristics, boundary layer, are evaluated numerically for different values of the magnetic field. Transient effects of velocity, temperature and diffusion are analyzed. A part of obtained results is given in the form of figures and corresponding conclusions.
International Nuclear Information System (INIS)
Pang Longgang; Wang Qun; Wang Xinnian; Xu Rong
2010-01-01
Transverse momentum correlations in the azimuthal angle of hadrons produced owing to minijets are first studied within the HIJING Monte Carlo model in high-energy heavy-ion collisions. Quenching of minijets during thermalization is shown to lead to significant diffusion (broadening) of the correlation. Evolution of the transverse momentum density fluctuation that gives rise to this correlation in azimuthal angle in the later stage of heavy-ion collisions is further investigated within a linearized diffusion-like equation and is shown to be determined by the shear viscosity of the evolving dense matter. This diffusion equation for the transverse momentum fluctuation is solved with initial values given by HIJING and together with the hydrodynamic equation for the bulk medium. The final transverse momentum correlation in azimuthal angle is calculated along the freeze-out hypersurface and is found to be further diffused for higher values of the shear viscosity to entropy density ratio, η/s∼0.2-0.4. Therefore the final transverse momentum correlation in azimuthal angle can be used to study the thermalization of minijets in the early stage of heavy-ion collisions and the viscous effect in the hydrodynamic evolution of strongly coupled quark-gluon plasma.
An On-Line Method for Thermal Diffusivity Detection of Thin Films Using Infrared Video
Directory of Open Access Journals (Sweden)
Dong Huilong
2016-03-01
Full Text Available A novel method for thermal diffusivity evolution of thin-film materials with pulsed Gaussian beam and infrared video is reported. Compared with common pulse methods performed in specialized labs, the proposed method implements a rapid on-line measurement without producing the off-centre detection error. Through mathematical deduction of the original heat conduction model, it is discovered that the area s, which is encircled by the maximum temperature curve rTMAX(θ, increases linearly over elapsed time. The thermal diffusivity is acquired from the growth rate of the area s. In this study, the off-centre detection error is avoided by performing the distance regularized level set evolution formulation. The area s was extracted from the binary images of temperature variation rate, without inducing errors from determination of the heat source centre. Thermal diffusivities of three materials, 304 stainless steel, titanium, and zirconium have been measured with the established on-line detection system, and the measurement errors are: −2.26%, −1.07%, and 1.61% respectively.
International Nuclear Information System (INIS)
Yamamoto, Ichiro; Kanagawa, Akira
1987-01-01
In order to evaluate separative performance of a thermal diffusion column, a simplification is usually made in which the temperature dependence of the relevant properties such as thermal diffusion constant is ignored and some proper mean values evaluated at a specific ''mean'' temperature are used. Adoption of weighted average of temperature distribution is common for the ''mean'' temperature, but there exists no definite way of determining mean temperature. The present paper proposes a new reference mean temperature determined by the equation governing the free convection. It is based on the fact that the multiplication effect of free convection is essential to separation by thermal diffusion column. The reference mean temperature is related to pressure difference between top and bottom of column and is higher than a mass-averaged temperature (due to gravitational force) by a contribution of viscous force. The reference mean temperature was calculated, as a reference, for an Ar isotope separating column with an inner hot radius of 0.2 mm and an outer cold radius of 5 mm. The results confirmed the validity of an approximate formula expressing effects of temperature difference and ratio of inner and outer radii of column explicitly for the temperature. The reference mean temperature calculated from pressure difference given by axisymmetric solution of equations of change was in good agreement with the analytical solution. (author)
'Thermal ghosts': apparent decay of fixed surfaces caused by heat diffusion
International Nuclear Information System (INIS)
Livadiotis, George
2007-01-01
The behaviour concerning classical heat diffusion on fixed thermal surfaces, studied by observations, still holds surprises. As soon as convective and radiative processes are negligible within the medium, this is considered to be free from energy sources and sinks. Then, the heat diffusion equation is conveniently solved using standard Fourier methods. Some considerations about the contrast effect suggest that the surface boundary would rather be observed to follow specific area decay dynamics than remaining fixed and static. Here it is shown that the apparent boundary lies on a specific isothermal spatiotemporal curve, which depends on the observing device. This is characterized by a slight, though determinative, difference between its radiance and that of the ambient background. Thereafter, the heat diffusion yields apparent boundary shrinkage with the passing of time. This phenomenon is particularly notable for two reasons: its lifetime and final decay rate depend only on the medium thermal properties, while being independent of the apparent boundary spatiotemporal curve. Thus, the former provides a suitable method for measuring the medium thermal properties via the observational data. The latter strongly reveal a kind of universality of some characteristic properties of the phenomenon, common to all observers
International Nuclear Information System (INIS)
Drozdowicz, K.
1999-01-01
Macroscopic parameters for a description of the thermal neutron transport in finite volumes are considered. A very good correspondence between the theoretical and experimental parameters of hydrogenous media is attained. Thermal neutrons in the medium possess an energy distribution, which is dependent on the size (characterized by the geometric buckling) and on the neutron transport properties of the medium. In a hydrogenous material the thermal neutron transport is dominated by the scattering cross section which is strongly dependent on energy. A monoenergetic treatment of the thermal neutron group (admissible for other materials) leads in this case to a discrepancy between theoretical and experimental results. In the present paper the theoretical definitions of the pulsed thermal neutron parameters (the absorption rate, the diffusion coefficient, and the diffusion cooling coefficient) are based on Nelkin's analysis of the decay of a neutron pulse. Problems of the experimental determination of these parameters for a hydrogenous medium are discussed. A theoretical calculation of the pulsed parameters requires knowledge of the scattering kernel. For thermal neutrons it is individual for each hydrogenous material because neutron scattering on hydrogen nuclei bound in a molecule is affected by the molecular dynamics (characterized with internal energy modes which are comparable to the incident neutron energy). Granada's synthetic model for slow-neutron scattering is used. The complete up-dated formalism of calculation of the energy transfer scattering kernel after this model is presented in the paper. An influence of some minor variants within the model on the calculated differential and integral neutron parameters is shown. The theoretical energy-dependent scattering cross section (of Plexiglas) is compared to experimental results. A particular attention is paid to the calculation of the diffusion cooling coefficient. A solution of an equation, which determines the
Chlorine Diffusion in Uranium Dioxide: Thermal Effects versus Radiation Enhanced Effects
International Nuclear Information System (INIS)
Pipon, Yves; Moncoffre, Nathalie; Bererd, Nicolas; Jaffrezic, Henri; Toulhoat, Nelly; Barthe, Marie France; Desgardin, Pierre; Raimbault, Louis; Scheidegger, Andre M.; Carlot, Gaelle
2007-01-01
Chlorine is present as an impurity in the UO 2 nuclear fuel. 35 Cl is activated into 36 Cl by thermal neutron capture. In case of interim storage or deep geological disposal of the spent fuel, this isotope is known to be able to contribute significantly to the instant release fraction because of its mobile behavior and its long half life (around 300000 years). It is therefore important to understand its migration behavior within the fuel rod. During reactor operation, chlorine diffusion can be due to thermally activated processes or can be favoured by irradiation defects induced by fission fragments or alpha decay. In order to decouple both phenomena, we performed two distinct experiments to study the effects of thermal annealing on the behaviour of chlorine on one hand and the effects of the irradiation with fission products on the other hand. During in reactor processes, part of the 36 Cl may be displaced from its original position, due to recoil or to collisions with fission products. In order to study the behavior of the displaced chlorine, 37 Cl has been implanted into sintered depleted UO 2 pellets (mean grain size around 18 μm). The spatial distribution of the implanted and pristine chlorine has been analyzed by SIMS before and after treatment. Thermal annealing of 37 Cl implanted UO 2 pellets (implantation fluence of 10 13 ions.cm -2 ) show that it is mobile from temperatures as low as 1273 K (E a =4.3 eV). The irradiation with fission products (Iodine, E=63.5 MeV) performed at 300 and 510 K, shows that the diffusion of chlorine is enhanced and that a thermally activated contribution is preserved (E a =0.1 eV). The diffusion coefficients measured at 1473 K and under fission product irradiation at 510 K are similar (D = 3.10 -14 cm 2 .s -1 ). Considering in first approximation that the diffusion length L can be expressed as a function of the diffusion coefficient D and time t by : L=(Dt)1/2, the diffusion distance after 3 years is L=17 μm. It results that
Capriotti, Margherita; Sternini, Simone; Lanza di Scalea, Francesco; Mariani, Stefano
2016-04-01
In the field of non-destructive evaluation, defect detection and visualization can be performed exploiting different techniques relying either on an active or a passive approach. In the following paper the passive technique is investigated due to its numerous advantages and its application to thermography is explored. In previous works, it has been shown that it is possible to reconstruct the Green's function between any pair of points of a sensing grid by using noise originated from diffuse fields in acoustic environments. The extraction of the Green's function can be achieved by cross-correlating these random recorded waves. Averaging, filtering and length of the measured signals play an important role in this process. This concept is here applied in an NDE perspective utilizing thermal fluctuations present on structural materials. Temperature variations interacting with thermal properties of the specimen allow for the characterization of the material and its health condition. The exploitation of the thermographic image resolution as a dense grid of sensors constitutes the basic idea underlying passive thermography. Particular attention will be placed on the creation of a proper diffuse thermal field, studying the number, placement and excitation signal of heat sources. Results from numerical simulations will be presented to assess the capabilities and performances of the passive thermal technique devoted to defect detection and imaging of structural components.
International Nuclear Information System (INIS)
Perez, L; Autrique, L; Gillet, M
2008-01-01
The aim of this paper is to investigate the thermal diffusivity identification of a multilayered material dedicated to fire protection. In a military framework, fire protection needs to meet specific requirements, and operational protective systems must be constantly improved in order to keep up with the development of new weapons. In the specific domain of passive fire protections, intumescent coatings can be an effective solution on the battlefield. Intumescent materials have the ability to swell up when they are heated, building a thick multi-layered coating which provides efficient thermal insulation to the underlying material. Due to the heat aggressions (fire or explosion) leading to the intumescent phenomena, high temperatures are considered and prevent from linearization of the mathematical model describing the system state evolution. Previous sensitivity analysis has shown that the thermal diffusivity of the multilayered intumescent coating is a key parameter in order to validate the predictive numerical tool and therefore for thermal protection optimisation. A conjugate gradient method is implemented in order to minimise the quadratic cost function related to the error between predicted temperature and measured temperature. This regularisation algorithm is well adapted for a large number of unknown parameters.
Isochoric thermal conductivity of solid carbon oxide: the role of phonons and 'diffusive' modes
International Nuclear Information System (INIS)
Konstantinov, V A; Manzhelii, V G; Revyakin, V P; Sagan, V V; Pursky, O I
2006-01-01
The isochoric thermal conductivity of solid CO was investigated in three samples of different densities in the interval from 35 K to the onset of melting. In α-CO the temperature dependence of the isochoric thermal conductivity is significantly weaker than Λ∝1/T; in β-CO it increases slightly with temperature. A quantitative description of the experimental results is given within the Debye model of thermal conductivity in the approximation of the corresponding relaxation times and which allows for the fact that the mean-free path of phonons cannot become smaller than half the phonon wavelength. On this consideration the heat is transported by both phonons and 'diffusive' modes
International Nuclear Information System (INIS)
Otter, Claude; Vandevelde, Jean
1982-01-01
Two solutions, one analytical and the other numerical are proposed to solve the thermokinetic problem encountered when measuring the thermal diffusivity of liquid materials at very high temperature (T>3123K). The liquid material is contained in a parallel faced vessel. This liquid is traversed by a short thermal pulse from a relaxed laser. The temperature response of the back face of the measurement cell is analysed. The first model proposed which does not take thermal losses into consideration, is a mathematical model derived from the ''two layer model'' (Larson and Koyama, 1968) extended to ''three layers''. In order to take the possibility of thermal losses to the external environment at high temperature into consideration, a Crank-Nicolson (1947) type numerical model utilizing finite differences is employed. These thermokinetic studies were performed in order to interpret temperature response curves obtained from the back face of a tungsten-liquid UO 2 -tungsten thermal wall, the purpose of the measurements made being to determine the thermal properties of liquid uranium oxide [fr
Bisetti, Fabrizio; El Morsli, Mbark
2012-01-01
Simulations of ion and electron transport in flames routinely adopt plasma fluid models, which require transport coefficients to compute the mass flux of charged species. In this work, the mobility and diffusion coefficient of thermal electrons
Hofmeister, A.
2010-12-01
Many measurements and models of heat transport in lower mantle candidate phases contain systematic errors: (1) conventional methods of insulators involve thermal losses that are pressure (P) and temperature (T) dependent due to physical contact with metal thermocouples, (2) measurements frequently contain unwanted ballistic radiative transfer which hugely increases with T, (3) spectroscopic measurements of dense samples in diamond anvil cells involve strong refraction by which has not been accounted for in analyzing transmission data, (4) the role of grain boundary scattering in impeding heat and light transfer has largely been overlooked, and (5) essentially harmonic physical properties have been used to predict anharmonic behavior. Improving our understanding of the physics of heat transport requires accurate data, especially as a function of temperature, where anharmonicity is the key factor. My laboratory provides thermal diffusivity (D) at T from laser flash analysis, which lacks the above experimental errors. Measuring a plethora of chemical compositions in diverse dense structures (most recently, perovskites, B1, B2, and glasses) as a function of temperature provides a firm basis for understanding microscopic behavior. Given accurate measurements for all quantities: (1) D is inversely proportional to [T x alpha(T)] from ~0 K to melting, where alpha is thermal expansivity, and (2) the damped harmonic oscillator model matches measured D(T), using only two parameters (average infrared dielectric peak width and compressional velocity), both acquired at temperature. These discoveries pertain to the anharmonic aspects of heat transport. I have previously discussed the easily understood quasi-harmonic pressure dependence of D. Universal behavior makes application to the Earth straightforward: due to the stiffness and slow motions of the plates and interior, and present-day, slow planetary cooling rates, Earth can be approximated as being in quasi
Phase and thickness dependence of thermal diffusivity in a-SiCxNy and a-BCxNy
International Nuclear Information System (INIS)
Chattopadhyay, S.; Chen, L.C.; Chien, S.C.; Lin, S.T.; Wu, C.T.; Chen, K.H.
2002-01-01
Thermal diffusivity (α) and bonding configuration of amorphous silicon carbon nitride (a-SiC x N y ) and boron carbon nitride (a-BC x N y ) films on silicon substrates were studied. Measurement of α by the traveling wave technique and bonding characterisation through X-ray photoelectron spectroscopy in a-SiC x N y and a-BC x N y films having different carbon concentrations revealed that lower coordinated bonds were detrimental to the thermal diffusivity of these films. Furthermore, α was found to depend on the thickness of these films deposited on silicon. This was attributed to the interface thermal resistance between two thermally different materials, the film and the substrate, although other factors such as film microstructure could also play a role. An empirical relation for the variation of thermal diffusivity with thickness is proposed
Energy Technology Data Exchange (ETDEWEB)
Prandel, L. V.; Somer, A.; Assmann, A.; Camelotti, F.; Costa, G.; Bonardi, C.; Jurelo, A. R.; Rodrigues, J. B.; Cruz, G. K. [Universidade Estadual de Ponta Grossa, Grupo de Espectroscopia Optica e Fotoacustica de Materiais, Departamento de Fisica, Av. Carlos Cavalcanti, 4748, CEP 84030-900, Ponta Grossa, PR (Brazil)
2013-02-14
This work reports for the first time on the use of the open photoacoustic cell technique operating at very low frequencies and at room temperature to experimentally determine the thermal diffusivity parameter of commercial AISI304 stainless steel and AISI304 stainless steel nitrided samples. Complementary measurements of X-ray diffraction and scanning electron microscopy were also performed. The results show that in standard AISI 304 stainless steel samples the thermal diffusivity is (4.0 {+-} 0.3) Multiplication-Sign 10{sup -6} m{sup 2}/s. After the nitriding process, the thermal diffusivity increases to the value (7.1 {+-} 0.5) Multiplication-Sign 10{sup -6} m{sup 2}/s. The results are being associated to the diffusion process of nitrogen into the surface of the sample. Carrying out subsequent thermal treatment at 500 Degree-Sign C, the thermal diffusivity increases up to (12.0 {+-} 2) Multiplication-Sign 10{sup -6} m{sup 2}/s. Now the observed growing in the thermal diffusivity must be related to the change in the phases contained in the nitrided layer.
The Effect of Al2O3 Addition on the Thermal Diffusivity of Heat Activated Acrylic Resin.
Atla, Jyothi; Manne, Prakash; Gopinadh, A; Sampath, Anche; Muvva, Suresh Babu; Kishore, Krishna; Sandeep, Chiramana; Chittamsetty, Harika
2013-08-01
This study aimed at investigating the effect of adding 5% to 20% by weight aluminium oxide powder (Al2O3) on thermal diffusivity of heat-polymerized acrylic resin. Twenty five cylindrical test specimens with an embedded thermocouple were used to determine thermal diffusivity over a physiologic temperature range (0 to 70°C). The specimens were divided into five groups (5 specimens/group) which were coded A to E. Group A was the control group (unmodified acrylic resin specimens). The specimens of the remaining four groups were reinforced with 5%, 10%, 15%, and 20% Al2O3 by weight. RESULTS were analysed by using one-way analysis of variance (ANOVA). Test specimens which belonged to Group E showed the highest mean thermal diffusivity value of 10.7mm(2)/sec, followed by D (9.09mm(2)/sec), C (8.49mm(2)/sec), B(8.28mm(2)/sec) and A(6.48mm(2)/sec) groups respectively. Thermal diffusivities of the reinforced acrylic resins were found to be significantly higher than that of the unmodified acrylic resin. Thermal diffusivity was found to increase in proportion to the weight percentage of alumina filler. Al2O3 fillers have potential to provide increased thermal diffusivity. Increasing the heat transfer characteristics of the acrylic resin base material could lead to more patient satisfaction.
Formation of protocell-like vesicles in a thermal diffusion column.
Budin, Itay; Bruckner, Raphael J; Szostak, Jack W
2009-07-22
Many of the properties of bilayer membranes composed of simple single-chain amphiphiles seem to be well-suited for a potential role as primitive cell membranes. However, the spontaneous formation of membranes from such amphiphiles is a concentration-dependent process in which a significant critical aggregate concentration (cac) must be reached. Since most scenarios for the prebiotic synthesis of fatty acids and related amphiphiles would result in dilute solutions well below the cac, the identification of mechanisms that would lead to increased local amphiphile concentrations is an important aspect of defining reasonable conditions for the origin of cellular life. Narrow, vertically oriented channels within the mineral precipitates of hydrothermal vent towers have previously been proposed to act as natural Clusius-Dickel thermal diffusion columns, in which a strong transverse thermal gradient concentrates dilute molecules through the coupling of thermophoresis and convection. Here we experimentally demonstrate that a microcapillary acting as a thermal diffusion column can concentrate a solution of oleic acid. Upon concentration, self-assembly of large vesicles occurs in regions where the cac is exceeded. We detected vesicle formation by fluorescence microscopy of encapsulated dye cargoes, which simultaneously concentrated in our channels. Our findings suggest a novel means by which simple physical processes could have led to the spontaneous formation of cell-like structures from a dilute prebiotic reservoir.
Iron doping of lithium niobate by thermal diffusion from thin film: study of the treatment effect
Energy Technology Data Exchange (ETDEWEB)
Ciampolillo, Maria Vittoria; Zaltron, Annamaria; Bazzan, Marco; Argiolas, Nicola; Sada, Cinzia [Universita di Padova (Italy); CNISM, Dipartimento di Fisica ' ' G. Galilei' ' , Padova (Italy); Mignoni, Sabrina; Fontana, Marc [Universite de Metz et Supelec, Laboratoire Materiaux Optiques, Photoniques et Systemes, UMR CNRS 7132, Metz (France)
2011-07-15
Thermal diffusion from thin film is one of the most widespread approaches to prepare iron doped regions in lithium niobate with limited size for photorefractive applications. In this work, we investigate the doping process with the aim of determining the best process conditions giving a doped region with the characteristics required for photorefractive applications. Six samples were prepared by changing the atmosphere employed in the diffusion treatment in order to obtain different combination of diffusion profiles and reduction degrees and also to check the effect of employing a wet atmosphere. The compositional, optical, and structural properties are then extensively characterized by combining Secondary ion Mass Spectrometry, UV, visible and IR spectrophotometry, High Resolution X-Rays Diffraction, and Micro-Raman Spectroscopy. Moreover, the sample topography was checked by Atomic Force Microscopy. An analysis of all our data shows that the best results are obtained performing a double step process, i.e. diffusion in oxidizing atmosphere and subsequent reduction at lower temperature in an hydrogen-containing atmosphere. (orig.)
International Nuclear Information System (INIS)
Durham, W.B.; Boro, C.O.; Beiriger, J.M.; Montan, D.N.
1983-10-01
Measurements of thermal conductivity and diffusivity were made on five core samples of bedded rock salt from the Permian Basin in Texas to determine its suitability as an underground nuclear waste repository. The sample size was 100 mm in diameter by 250 mm in length. Measurements were conducted under confining pressures ranging from 3.8 to 31.0 MPa and temperatures from room temperature to 473 K. Conductivity showed no dependence on confining pressure but evidenced a monotonic, negative temperature dependence. Four of the five samples showed conductivities clustered in a range of 5.6 +- 0.5 W/m.K at room temperature, falling to 3.6 +- 0.3 W/m.K at 473 K. These values are approximately 20% below those for pure halite, reflecting perhaps the 5 to 20%-nonhalite component of the samples. Diffusivity also showed a monotonic, negative temperature dependence, with four of the five samples clustered in a range of 2.7 +- 0.4 x 10 -6 m 2 /s at room temperature, and 1.5 +- 0.3 x 10 -6 m 2 /s at 473 K, all roughly 33% below the values for pure halite. One sample showed an unusually high conductivity (it also had the highest diffusivity), about 20% higher than the others; and one sample showed an unusually low diffusivity (it also had the lowest conductivity), roughly a factor of 2 lower than the others. 27 references, 8 figures, 4 tables
International Nuclear Information System (INIS)
Yokoyama, Masayuki
2014-01-01
A statistical approach is proposed to predict thermal diffusivity profiles as a transport “model” in fusion plasmas. It can provide regression expressions for the ion and electron heat diffusivities (χ i and χ e ), separately, to construct their radial profiles. An approach that this letter is proposing outstrips the conventional scaling laws for the global confinement time (τ E ) since it also deals with profiles (temperature, density, heating depositions etc.). This approach has become possible with the analysis database accumulated by the extensive application of the integrated transport analysis suite to experiment data. In this letter, TASK3D-a analysis database for high-ion-temperature (high-T i ) plasmas in the LHD (Large Helical Device) is used as an example to describe an approach. (author)
Significantly reduced c-axis thermal diffusivity of graphene-based papers
Han, Meng; Xie, Yangsu; Liu, Jing; Zhang, Jingchao; Wang, Xinwei
2018-06-01
Owing to their very high thermal conductivity as well as large surface-to-volume ratio, graphene-based films/papers have been proposed as promising candidates of lightweight thermal interface materials and lateral heat spreaders. In this work, we study the cross-plane (c-axis) thermal conductivity (k c ) and diffusivity (α c ) of two typical graphene-based papers, which are partially reduced graphene paper (PRGP) and graphene oxide paper (GOP), and compare their thermal properties with highly-reduced graphene paper and graphite. The determined α c of PRGP varies from (1.02 ± 0.09) × 10‑7 m2 s‑1 at 295 K to (2.31 ± 0.18) × 10‑7 m2 s‑1 at 12 K. This low α c is mainly attributed to the strong phonon scattering at the grain boundaries and defect centers due to the small grain sizes and high-level defects. For GOP, α c varies from (1.52 ± 0.05) × 10‑7 m2 s‑1 at 295 K to (2.28 ± 0.08) × 10‑7 m2 s‑1 at 12.5 K. The cross-plane thermal transport of GOP is attributed to the high density of functional groups between carbon layers which provide weak thermal transport tunnels across the layers in the absence of direct energy coupling among layers. This work sheds light on the understanding and optimizing of nanostructure of graphene-based paper-like materials for desired thermal performance.
Correction Effect of Finite Pulse Duration for High Thermal Diffusivity Materials
International Nuclear Information System (INIS)
Park, Dae Gyu; Kim, Hee Moon; Baik, Seung Je; Yoo, Byoung Ok; Ahn, Sang Bok; Ryu, Woo Seok
2010-01-01
In the laser pulsed flash method, a pulse of energy is incident on one of two parallel faces of a sample. The subsequent temperature history of the opposite face is then related to the thermal diffusivity. When the heat pulse is of infinitesimal duration, the diffusivity is obtained from the transient response of the rear face temperature proposed by Parker et al. The diffusivity αis computed from relation 2222121.37cattαππ≡= (1) Where a is the sample thickness and is the time required for the rear face temperature to reach half-maximum, and t c ≡a 2 / π 2 t 1/2 is the characteristic rise time of the rear face temperature. When the pulse-time 1/2tτis not infinitesimal, but becomes comparable to tc, it is apparent that the rise in temperature of the rear face will be retarded, and will be greater than 1.37 t c . This retardation has been called the ' finite pulse-time effect.' Equation (1) is accurate to 1% for tc > ∼ 501/2tτ. For many substances, this inequality cannot be achieved with conventional optical sources (e.g. τ. 10 -3 sec for a solid state laser) unless the sample thickness is so large that its rise in temperature is too small for accurate measurement. One must therefore make an appropriate correction for the retardation of the temperature wave. Purpose of study are to observe impact of finite pulse time effect in appropriate sample thickness and to verify the effect of pulse correction using Cape and Lehman method for high thermal diffusivity materials
Local Group dSph radio survey with ATCA - II. Non-thermal diffuse emission
Regis, Marco; Richter, Laura; Colafrancesco, Sergio; Profumo, Stefano; de Blok, W. J. G.; Massardi, Marcella
2015-04-01
Our closest neighbours, the Local Group dwarf spheroidal (dSph) galaxies, are extremely quiescent and dim objects, where thermal and non-thermal diffuse emissions lack, so far, of detection. In order to possibly study the dSph interstellar medium, deep observations are required. They could reveal non-thermal emissions associated with the very low level of star formation, or to particle dark matter annihilating or decaying in the dSph halo. In this work, we employ radio observations of six dSphs, conducted with the Australia Telescope Compact Array in the frequency band 1.1-3.1 GHz, to test the presence of a diffuse component over typical scales of few arcmin and at an rms sensitivity below 0.05 mJy beam-1. We observed the dSph fields with both a compact array and long baselines. Short spacings led to a synthesized beam of about 1 arcmin and were used for the extended emission search. The high-resolution data mapped background sources, which in turn were subtracted in the short-baseline maps, to reduce their confusion limit. We found no significant detection of a diffuse radio continuum component. After a detailed discussion on the modelling of the cosmic ray (CR) electron distribution and on the dSph magnetic properties, we present bounds on several physical quantities related to the dSphs, such that the total radio flux, the angular shape of the radio emissivity, the equipartition magnetic field, and the injection and equilibrium distributions of CR electrons. Finally, we discuss the connection to far-infrared and X-ray observations.
International Nuclear Information System (INIS)
Gupta, A.; Hong, S.; Moacanin, J.
1981-01-01
A method and apparatus for measuring thermal diffusivity and molecular relaxation processes in a sample material utilizing two light beams, one being a pulsed laser light beam for forming a thermal lens in the sample material, and the other being a relatively low power probe light beam for measuring changes in the refractive index of the sample material during formation and dissipation of the thermal lens. More specifically, a sample material is irradiated by relatively high power, short pulses from a dye laser. Energy from the pulses is absorbed by the sample material, thereby forming a thermal lens in the area of absorption. The pulse repetition rate is chosen so that the thermal lens is substantially dissipated by the time the next pulse reaches the sample material. A probe light beam, which in a specific embodiment is a relatively low power, continuous wave (Cw) laser beam, irradiates the thermal lens formed in the sample material. The intensity characteristics of the probe light beam subsequent to irradiation of the thermal lens is related to changes in the refractive index of the sample material as the thermal lens is formed and dissipated. A plot of the changes in refractive index as a function of time during formation of the thermal lens as reflected by changes in intensity of the probe beam, provides a curve related to molecular relaxation characteristics of the material, and a plot during dissipation of the thermal lens provides a curve related to the thermal diffusivity of the sample material
Enrichment of heavy water in thermal-diffusion columns connected in series
International Nuclear Information System (INIS)
Yeh, Ho-Ming; Chen, Liu Yi
2009-01-01
The separation equations for enrichment of heavy water from water isotope mixture by thermal diffusion in multiple columns connected in series, have been derived based on one column design developed in previous work. The improvement in separation is achievable by operating in a double-column device, instead of in a single-column device, with the same total column length. It is also found that further improvement in separation is obtainable if a triple-column device is employed, except for operating under small total column length and low flow rate.
Thermal Diffusion Processes in Metal-Tip-Surface Interactions: Contact Formation and Adatom Mobility
DEFF Research Database (Denmark)
Sørensen, Mads Reinholdt; Jacobsen, Karsten Wedel; Jonsson, Hannes
1996-01-01
and the surface can occur by a sequence of atomic hop and exchange processes which become active on a millisecond time scale when the tip is about 3-5 Angstrom from the surface. Adatoms on the surface are stabilized by the presence of the tip and energy barriers for diffusion processes in the region under the tip......We have carried out computer simulations to identify and characterize various thermally activated atomic scale processes that can play an important role in room temperature experiments where a metal tip is brought close to a metal surface. We find that contact formation between the tip...
Influence of silicon dangling bonds on germanium thermal diffusion within SiO{sub 2} glass
Energy Technology Data Exchange (ETDEWEB)
Barba, D.; Martin, F.; Ross, G. G. [INRS Centre for Energy, Materials and Telecommunications, 1650 Boul. Lionel-Boulet, Varennes, Québec J3X 1S2 (Canada); Cai, R. S.; Wang, Y. Q. [The Cultivation Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China); Demarche, J.; Terwagne, G. [LARN, Centre de Recherche en Physique de la Matière et du Rayonnement (PMR), University of Namur (FUNDP), B-5000 Namur (Belgium); Rosei, F. [INRS Centre for Energy, Materials and Telecommunications, 1650 Boul. Lionel-Boulet, Varennes, Québec J3X 1S2 (Canada); Center for Self-Assembled Chemical Structures, McGill University, Montreal, Quebec H3A 2K6 (Canada)
2014-03-17
We study the influence of silicon dangling bonds on germanium thermal diffusion within silicon oxide and fused silica substrates heated to high temperatures. By using scanning electron microscopy and Rutherford backscattering spectroscopy, we determine that the lower mobility of Ge found within SiO{sub 2}/Si films can be associated with the presence of unsaturated SiO{sub x} chemical bonds. Comparative measurements obtained by x-ray photoelectron spectroscopy show that 10% of silicon dangling bonds can reduce Ge desorption by 80%. Thus, the decrease of the silicon oxidation state yields a greater thermal stability of Ge inside SiO{sub 2} glass, which could enable to considerably extend the performance of Ge-based devices above 1300 K.
Directory of Open Access Journals (Sweden)
Muthucumaraswamy R.
2006-01-01
Full Text Available Thermal radiation effects on unsteady free convective flow of a viscous incompressible flow past an infinite vertical oscillating plate with variable temperature and mass diffusion has been studied. The fluid considered here is a gray, absorbing-emitting radiation but a non-scattering medium. The plate temperature is raised linearly with respect to time and the concentration level near the plate is also raised linearly with respect to time. An exact solution to the dimensionless governing equations has been obtained by the Laplace transform method, when the plate is oscillating harmonically in its own plane. The effects of velocity, temperature and concentration are studied for different parameters like phase angle, radiation parameter, Schmidt number, thermal Grashof number, mass Grashof number and time are studied. It is observed that the velocity increases with decreasing phase angle ωt. .
Evaluation of ethanol aged PVDF: diffusion, crystallinity and dynamic mechanical thermal properties
International Nuclear Information System (INIS)
Silva, Agmar J.J.; Costa, Marysilvia F.
2015-01-01
This work discuss firstly the effect of the ethanol fuel absorption by PVDF at 60°C through mass variation tests. A Fickian character was observed for the ethanol absorption kinetics of the aged PVDF at 60°C. In the second step, the dynamic mechanical thermal properties (E’, E’, E” and tan δ) of the PVDF were evaluated through dynamic mechanical thermal analysis (DMTA). The chemical structure of the materials was analyzed by X-ray diffraction analysis (XRD), and significant changes in the degree of crystallinity were verified after the aging. However, DMTA results showed a reduction in the storage modulus (E') of the aged PVDF, which was associated to diffusion of ethanol and swelling of the PVDF, which generated a prevailing plasticizing effect and led to reduction of its structural stiffness. (author)
International Nuclear Information System (INIS)
Tittle, C.W.
1992-01-01
Diffusion theory has been successfully used to model the effect of fluid invasion into the formation for neutron porosity logs and for the gamma-gamma density log. The purpose of this paper is to present results of computations using a five-group time-dependent diffusion code on invasion effects for the pulsed neutron thermal decay time log. Previous invasion studies by the author involved the use of a three-dimensional three-group steady-state diffusion theory to model the dual-detector thermal neutron porosity log and the gamma-gamma density log. The five-group time-dependent code MGNDE (Multi-Group Neutron Diffusion Equation) used in this work was written by Ferguson. It has been successfully used to compute the intrinsic formation life-time correction for pulsed neutron thermal decay time logs. This application involves the effect of fluid invasion into the formation
International Nuclear Information System (INIS)
Pech-May, Nelson Wilbur; Cifuentes, Ángel; Mendioroz, Arantza; Oleaga, Alberto; Salazar, Agustín
2015-01-01
Both thermal diffusivity and effusivity (or conductivity) are necessary to characterize the thermal transport properties of a material. The flash method is the most recognized procedure to measure the thermal diffusivity of free-standing opaque plates. However, it fails to simultaneously obtain the thermal effusivity (or conductivity). This is due to the difficulty of knowing the total energy absorbed by the sample surface after the light pulse. In this work, we propose using the flash method in the front-face configuration on a two-layer system made of the unknown plate and a fluid of known thermal properties. We demonstrate that the surface temperature is sensitive to the thermal mismatch between the plate and the fluid, which is governed by their thermal effusivity ratio. In order to verify the validity of the method and to establish its application limits we have performed flash measurements, using a pulsed laser and an infrared camera, on a set of calibrated materials (metals, alloys, ceramics and polymers) covering a wide range of thermal transport properties. These results confirm the ability of the flash method to simultaneously retrieve thermal diffusivity and effusivity in a fast manner in samples whose effusivities are lower than three times the effusivity of the liquid used as backing fluid. (paper)
International Nuclear Information System (INIS)
Nicolaides, Lena; Mandelis, Andreas; Beingessner, Clare J.
2001-01-01
It is well established that in hardened steels thermal-diffusivity broadly anticorrelates with microhardness, allowing thermal-wave depth profilometry to be used as a tool to measure microhardness profiles. Nevertheless, the physical mechanisms for this anticorrelation have not been well understood. In this work, the thermal-diffusivity profiles of rough, hardened industrial steels were reconstructed after the elimination of roughness effects from the experimental data. Carburizing and quenching are widely used for the heat treatment of steel components, and it is important to understand their effects on thermal-diffusivity profiles. A thorough examination of the actual mechanism by which thermal-diffusivity depth profiles are affected by first carburizing and then quenching AISI-8620 steels was performed. It was concluded that the variation of thermal diffusivity with depth is dominated by the carbon concentration profile, whereas the absolute value of the thermal diffusivity is a function of microstructure. [copyright] 2001 American Institute of Physics
Muñoz, G. A. López; González, R. F. López; López, J. A. Balderas; Martínez-Pérez, L.
2011-05-01
Photoacoustic methodology in the transmission configuration (PMTC) was used to study the thermophysical properties and their relation with the composition in Mexican citrus essential oils providing the viability of using photothermal techniques for quality control and for authentication of oils and their adulteration. Linear relations for the amplitude (on a semi-log scale) and phase, as functions of the sample's thickness, for the PMTC was obtained through a theoretical model fit to the experimental data for thermal-diffusivity measurements in Mexican orange, pink grapefruit, mandarin, lime type A, centrifuged essential oils, and Mexican distilled lime essential oil. Gas chromatography for distilled lime essential oil and centrifuged lime essential oil type A is reported to complement the study. Experimental results showed close thermal-diffusivity values between Mexican citrus essential oils obtained by centrifugation, but a significant difference of this physical property for distilled lime oil and the corresponding value obtained by centrifugation, which is due to their different chemical compositions involved with the extraction processes.
Ivers, D. J.; Phillips, C. G.
2018-03-01
We re-consider the plate-like model of turbulence in the Earth's core, proposed by Braginsky and Meytlis (1990), and show that it is plausible for core parameters not only in polar regions but extends to mid- and low-latitudes where rotation and gravity are not parallel, except in a very thin equatorial layer. In this model the turbulence is highly anisotropic with preferred directions imposed by the Earth's rotation and the magnetic field. Current geodynamo computations effectively model sub-grid scale turbulence by using isotropic viscous and thermal diffusion values significantly greater than the molecular values of the Earth's core. We consider a local turbulent dynamo model for the Earth's core in which the mean magnetic field, velocity and temperature satisfy the Boussinesq induction, momentum and heat equations with an isotropic turbulent Ekman number and Roberts number. The anisotropy is modelled only in the thermal diffusion tensor with the Earth's rotation and magnetic field as preferred directions. Nonlocal organising effects of gravity and rotation (but not aspect ratio in the Earth's core) such as an inverse cascade and nonlocal transport are assumed to occur at longer length scales, which computations may accurately capture with sufficient resolution. To investigate the implications of this anisotropy for the proposed turbulent dynamo model we investigate the linear instability of turbulent magnetoconvection on length scales longer than the background turbulence in a rotating sphere with electrically insulating exterior for no-slip and isothermal boundary conditions. The equations are linearised about an axisymmetric basic state with a conductive temperature, azimuthal magnetic field and differential rotation. The basic state temperature is a function of the anisotropy and the spherical radius. Elsasser numbers in the range 1-20 and turbulent Roberts numbers 0.01-1 are considered for both equatorial symmetries of the magnetic basic state. It is found
Energy Technology Data Exchange (ETDEWEB)
Kukkonen, I.; Suppala, I. [Geological Survey of Finland, Espoo (Finland)
1999-01-01
In situ measurements of thermal conductivity and diffusivity of bedrock were investigated with the aid of a literature survey and theoretical simulations of a measurement system. According to the surveyed literature, in situ methods can be divided into `active` drill hole methods, and `passive` indirect methods utilizing other drill hole measurements together with cutting samples and petrophysical relationships. The most common active drill hole method is a cylindrical heat producing probe whose temperature is registered as a function of time. The temperature response can be calculated and interpreted with the aid of analytical solutions of the cylindrical heat conduction equation, particularly the solution for an infinite perfectly conducting cylindrical probe in a homogeneous medium, and the solution for a line source of heat in a medium. Using both forward and inverse modellings, a theoretical measurement system was analysed with an aim at finding the basic parameters for construction of a practical measurement system. The results indicate that thermal conductivity can be relatively well estimated with borehole measurements, whereas thermal diffusivity is much more sensitive to various disturbing factors, such as thermal contact resistance and variations in probe parameters. In addition, the three-dimensional conduction effects were investigated to find out the magnitude of axial `leak` of heat in long-duration experiments. The radius of influence of a drill hole measurement is mainly dependent on the duration of the experiment. Assuming typical conductivity and diffusivity values of crystalline rocks, the measurement yields information within less than a metre from the drill hole, when the experiment lasts about 24 hours. We propose the following factors to be taken as basic parameters in the construction of a practical measurement system: the probe length 1.5-2 m, heating power 5-20 Wm{sup -1}, temperature recording with 5-7 sensors placed along the probe, and
International Nuclear Information System (INIS)
Kukkonen, I.; Suppala, I.
1999-01-01
In situ measurements of thermal conductivity and diffusivity of bedrock were investigated with the aid of a literature survey and theoretical simulations of a measurement system. According to the surveyed literature, in situ methods can be divided into 'active' drill hole methods, and 'passive' indirect methods utilizing other drill hole measurements together with cutting samples and petrophysical relationships. The most common active drill hole method is a cylindrical heat producing probe whose temperature is registered as a function of time. The temperature response can be calculated and interpreted with the aid of analytical solutions of the cylindrical heat conduction equation, particularly the solution for an infinite perfectly conducting cylindrical probe in a homogeneous medium, and the solution for a line source of heat in a medium. Using both forward and inverse modellings, a theoretical measurement system was analysed with an aim at finding the basic parameters for construction of a practical measurement system. The results indicate that thermal conductivity can be relatively well estimated with borehole measurements, whereas thermal diffusivity is much more sensitive to various disturbing factors, such as thermal contact resistance and variations in probe parameters. In addition, the three-dimensional conduction effects were investigated to find out the magnitude of axial 'leak' of heat in long-duration experiments. The radius of influence of a drill hole measurement is mainly dependent on the duration of the experiment. Assuming typical conductivity and diffusivity values of crystalline rocks, the measurement yields information within less than a metre from the drill hole, when the experiment lasts about 24 hours. We propose the following factors to be taken as basic parameters in the construction of a practical measurement system: the probe length 1.5-2 m, heating power 5-20 Wm -1 , temperature recording with 5-7 sensors placed along the probe, and
International Nuclear Information System (INIS)
Pereira, Thiago Martini
2009-01-01
In this work it was developed a software that calculates automatically, the thermal diffusivity value as a function of temperature in materials. The infrared thermography technique was used for data acquisition of temperature distribution as a function of time. These data were used to adjust a temperature function obtained from the homogeneous heat equation with specific boundary conditions. For that, an infrared camera (detecting from 8 μm to 9 μm) was calibrated to detect temperature ranging from 185 degree C up to 1300 degree C at an acquisition rate of 300 Hz. It was used, 10 samples of dental enamel and 10 samples of dentin, with 4 mm x 4 mm x 2 mm, which were obtained from bovine lower incisor teeth. These samples were irradiated with an Er:Cr:YSGG pulsed laser (λ = 2,78 μm). The resulting temperature was recorded 2 s prior, 10 s during irradiation and continuing for 2 more seconds after it. After each irradiation, all obtained thermal images were processed in the software, creating a file with the data of thermal diffusivity as a function of temperature. Another file with the thermal diffusivity values was also calculated after each laser pulse. The mean result of thermal diffusivity obtained for dental enamel was 0,0084 ± 0,001 cm2/s for the temperature interval of 220-550 degree C. The mean value for thermal diffusivity obtained for dentin was 0,0015 0,0004 cm2/s in temperatures up to 360 degree C; however, this value increases for higher temperatures. According to these results, it was possible to conclude that the use of infrared thermography, associated with the software developed in this work, is an efficient method to determine the thermal diffusivity values as a function of temperature in different materials. (author)
Ishizaki, Takuya; Nagano, Hosei
2015-11-01
A new measurement technique to measure the in-plane thermal diffusivity, the distribution of in-plane anisotropy, and the out-of-plane thermal diffusivity has been developed to evaluate the thermal conductivity of anisotropic materials such as carbon fiber-reinforced plastics (CFRPs). The measurements were conducted by using a laser-spot-periodic-heating method. The temperature of the sample is detected by using lock-in thermography. Thermography can analyze the phase difference between the periodic heat input and the temperature response of the sample. Two kinds of samples, unidirectional (UD) and cross-ply (CP) pitch-based CFRPs, were fabricated and tested in an atmospheric condition. All carbon fibers of the UD sample run in one direction [90°]. The carbon fibers of the CP sample run in two directions [0°/90°]. It is found that, by using lock-in thermography, it is able to visualize the thermal anisotropy and calculate the angular dependence of the in-plane thermal diffusivity of the CFRPs. The out-of-plane thermal diffusivity of CFRPs was also measured by analyzing the frequency dependence of the phase difference.
Characterization of the thermalness of a fissile system with a two-group diffusion theory parameter
International Nuclear Information System (INIS)
Bredehoft, B.B.; Busch, R.D.
1993-01-01
In tabulating critical data, the hydrogen-to-fissile atom ratio (H/X) is commonly used to characterize the amount of moderation in a system. Though adequate in many cases, H/X does not account for the moderating contribution of other light nuclei contained in common uranium-moderator mixtures. This ratio also does not account for enrichment of the system, which affects the resonance absorption characteristics and, therefore, the moderating behavior of that system. To alleviate these problems, a two-energy-group diffusion theory analogy to the six-factor formula was applied to define a new parameter p/(η 2 · f 2 ), which describes the moderation characteristics or the 'thermalness' of a fissioning system and includes the effects of enrichment and the presence of moderators other than hydrogen. From an analysis of several low-enriched uranium systems with different moderators, it was found that the values of p/(η 2 · f 2 ) corresponding to minimum critical mass and volume tend to center in a narrower range than do the values of H/X for the same systems. Also, the thermalness parameter does not vary with the addition of a reflector and is applicable to systems with other than hydrogenous moderators. Based on these results, the thermalness parameter p/(η 2 · f 2 ) provides an effective means of characterizing moderated systems relative to optimum conditions
Directory of Open Access Journals (Sweden)
S. Srinivas
2016-01-01
Full Text Available The present work investigates the effects of thermal-diffusion and diffusion-thermo on MHD flow of viscous fluid between expanding or contracting rotating porous disks with viscous dissipation. The partial differential equations governing the flow problem under consideration have been transformed by a similarity transformation into a system of coupled nonlinear ordinary differential equations. An analytical approach, namely the homotopy analysis method is employed in order to obtain the solutions of the ordinary differential equations. The effects of various emerging parameters on flow variables have been discussed numerically and explained graphically. Comparison of the HAM solutions with the numerical solutions is performed.
International Nuclear Information System (INIS)
Hsu, Ching-Chun; Yeh, Ho-Ming
2014-01-01
Highlights: • Recovery of deuterium by thermal diffusion from water–isotope mixture has been investigated. • The undesirable remixing effect can be reduced by employing the device of branch columns. • Deuterium recoveries were compared with that in a single column of the same total column length. • Considerable recovery improvement is obtainable in the device of branch columns, instead of in a single-column device. - Abstract: Deuterium recovery from water–isotopes mixture using thermal diffusion can be improved by employing the branch column device, instead of single column devices, with the same total column length. The remixing effect due to convection currents in a thermal diffusion column for heavy water enrichment is thus reduced and separation improvement increases when the flow rate or the total column length increases. The improvement in separation can reach about 50% for the numerical example given
Branlund, J. M.; Hofmeister, A.; Merriman, J. D.; Nabelek, P. I.; Whittington, A. G.
2010-12-01
We've created a new model for the average continental geotherm by incorporating accurate thermal conductivity values into Fourier's law. Previous geotherm models used thermal conductivities (k) with systematic errors: (1) Pores and microcracks in polycrystalline samples provide artificially low k compared to buried rocks, (2) conventional measurement techniques involve contact losses between thermocouples and samples, especially at high temperature, and/or (3) many techniques inadequately remove ballistic radiative transfer, which does not represent true heat transfer in the earth. To provide k values appropriate for Earth’s interior, we measured thermal diffusivity and its temperature derivatives using laser-flash analysis (LFA) for common rock-forming minerals. To avoid problems of pores and microcracks artificially lowering measured k values, we mathematically mixed mineral data to create synthetic rocks representative of the upper and lower crust and mantle, and checked our values against measurements of rocks least contaminated. Compared to previous models using k of rocks measured with non-LFA methods, our mixture models give higher k of crustal rocks at room temperature, but lower values at higher temperatures. Calculating a geotherm with these revised thermal conductivity values gives a lower temperature throughout the lower crust and mantle lithosphere. Altering the composition of the crust will change the geotherm; crust with more quartz, olivine and/or pyroxene has higher k and a lower geothermal gradient. Adding calcic plagioclase lowers k and steepens the geotherm. The new constraints on k allow us to set bounds on the steady-state geotherm based on ranges of possible mineralogy, chemistry, and radiogenic contents.
International Nuclear Information System (INIS)
Drozdowicz, K.; Woznicka, U.
1982-01-01
The program in FORTRAN for the ODRA-1305 computer is described. The dependence of the decay constant of the thermal neutron flux upon the dimensions of the two-region concentric cylindrical system is the result of the program. The solution (with a constant neutron flux in the inner medium assumed) is generally obtained in the one-group diffusion approximation by the method of the perturbation calculation. However, the energy distribution of the thermal neutron flux and the diffusion cooling are taken into account. The program is written for the case when the outer medium is hydrogenous. The listing of the program and an example of calculation results are included. (author)
On the sound attenuation in fluid due to the thermal diffusion and viscous dissipation
Energy Technology Data Exchange (ETDEWEB)
Hu, Hanping, E-mail: hphu@ustc.edu.cn; Wang, Yandong; Wang, Dongdong
2015-09-11
We review the sound attenuation in fluid due to the thermal diffusion and viscous dissipation and derive the formula of the sound attenuation coefficient in fluid by solving a fully thermally–mechanically coupled equation set. Problem occurring in Stokes–Kirchhoff relation, the well-known and widely used classical formula for sound attenuation coefficient, is therefore found and pointed out. The reason for its generation is analyzed and verified. An improved formula to replace Stokes–Kirchhoff relation is suggested and the typical case for the error in calculating sound pressure level (SPL) of attenuated sound wave in fluid between the two formulas is also given. - Highlights: • Problem with Stokes–Kirchhoff relation. • Generation reason of defect in Stokes–Kirchhoff relation. • An improved formula for sound attenuation coefficient in fluid. • Typical cases of the calculation error by Stokes–Kirchhoff relation.
Transport tensors in perfectly aligned low-density fluids: Self-diffusion and thermal conductivity
International Nuclear Information System (INIS)
Singh, G. S.; Kumar, B.
2001-01-01
The modified Taxman equation for the kinetic theory of low-density fluids composed of rigid aspherical molecules possessing internal degrees of freedom is generalized to obtain the transport tensors in a fluid of aligned molecules. The theory takes care of the shape of the particles exactly but the solution has been obtained only for the case of perfectly aligned hard spheroids within the framework of the first Sonine polynomial approximation. The expressions for the thermal-conductivity components have been obtained for the first time whereas the self-diffusion components obtained here turn out to be exactly the same as those derived by Kumar and Masters [Mol. Phys. >81, 491 (1994)] through the solution of the Lorentz-Boltzmann equation. All our expressions yield correct results in the hard-sphere limit
Thermal diffusion segregation of an impurity in a driven granular fluid
Energy Technology Data Exchange (ETDEWEB)
Reyes, Francisco Vega; Garzó, Vicente [Departamento de Física, Universidad de Extremadura, E-06071 Badajoz, Spain and Instituto de Computación Científica Avanzada (ICCAEx), Universidad de Extremadura, E-06071 Badajoz (Spain)
2014-12-09
We study segregation of an impurity in a driven granular fluid under two types of steady states. In the first state, the granular gas is driven by a stochastic volume force field with a Fourier-type profile while in the second state, the granular gas is sheared in such a way that inelastic cooling is balanced by viscous heating. We compare theoretical results derived from a solution of the (inelastic) Boltzmann equation at Navier-Stokes (NS) order with those obtained from the Direct Monte Carlo simulation (DSMC) method and molecular dynamics (MD) simulations. Good agreement is found between theory and simulation, which provides strong evidence of the reliability of NS granular hydrodynamics for these steady states (including the dynamics of the impurity), even at high inelasticity. In addition, preliminary results for thermal diffusion in granular fluids at moderate densities are also presented. As for dilute gases, excellent agreement is also found in this more general case.
Determination of the ion thermal diffusivity from neutron emission profiles in decay
International Nuclear Information System (INIS)
Sasao, M.; Adam, J.M.; Conroy, S.; Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Belle, P. van
1992-01-01
Spatial profiles of neutron emission are routinely obtained at the Joint European Torus (JET) from line-integrated emissivities measured with a multi-channel instrument. It is shown that the manner in which the emission profiles relax following termination of strong heating with Neutral Beam Injection (NBI) permits the local thermal diffusivity (χ i ) to be obtained with an accuracy of about 20%. The radial profiles of χ i for small minor radius (r/a 2 /s for H-mode plasmas with plasma current I p = 3.1 MA and toroidal field B T = 2.3T. The experimental value of χ i is smallest for Z eff = 2.2 and increases weakly with increasing Z eff . The experimental results disagree by two orders of magnitude with predictions from an ion temperature gradient driven turbulence model. (author) 6 refs., 3 figs
Directory of Open Access Journals (Sweden)
Li Tse-Chang
2017-01-01
Full Text Available In the present study, the thermal diffusivities of the Al, Si and ITO films deposited on the SUS304 steel substrate are evaluated via the present technique. Before applying this technique, the temperature for the thin film of the multi-layered specimen is developed theoretically for the one- dimensional steady heat conduction in response to amplitude and frequency of the periodically oscillating temperature imposed by a peltier placed beneath the specimen's substrate. By the thermal-electrical data processing system excluding the lock-in amplifier, the temperature frequency a3 has been proved first to be independent of the electrical voltage applied to the peltier and the contact position of the thermocouples. The experimental data of phase difference for three kinds of specimen are regressed well by a straight line with a slope. Then, the thermal diffusivity of the thin film is thus determined if the slope value and the film- thickness are available. In the present arrangements for the thermocouples, two thermal diffusivity values are quite close each other and valid for every kind of specimen. This technique can provide an efficient, low-cost method for the thermal diffusivity measurements of thin films.
International Nuclear Information System (INIS)
Zamengo, Massimiliano; Funada, Tomohiro; Morikawa, Junko
2017-01-01
Highlights: • Thermal diffusivity of Erythritol was measured by temperature wave method. • Thermal diffusivity was measured in function of temperature and during phase change. • Database of temperature-dependent thermal properties is used for numerical analysis. • Heat transfer and heat storage were analyzed in a fin-type heat exchanger. • Use of temperature-dependent properties in calculations lead to longer melting time. - Abstract: Temperature dependency of thermal diffusivity of erythritol was measured by temperature wave analysis (TWA) method. This modulating technique allowed measuring thermal diffusivity continuously, even during the phase transition solid-liquid. Together with specific heat capacity and specific enthalpy measured by differential scanning calorimetry, the values of measured properties were utilized in a bi-dimensional numerical model for analysis of heat transfer and heat storage performance. The geometry of the model is representative of a cross section of a fin-type heat exchanger, in which erythritol is filling the interspaces between fins. Time-dependent temperature change and heat storage performance were analyzed by considering the variation of thermophysical properties as a function of temperature. The numerical method can be utilized for a fast parametric analysis of heat transfer and heat storage performance into heat storage systems of phase-change materials and composites.
International Nuclear Information System (INIS)
Kutner, R.; Sosnowska, I.
1977-01-01
A Multi-Sublattice Jump Diffusion Model (MSJD) for hydrogen diffusion through interstitial-site lattices is presented. The MSJD approach may, in principle, be considered as an extension of the Rowe et al (J. Phys. Chem. Solids; 32:41 (1971)) model. Jump diffusion to any neighbours with different jump times which may be asymmetric in space is discussed. On the basis of the model a new method of calculating the diffusion tensor is advanced. The quasielastic, double differential cross section for thermal neutron scattering is obtained in terms of the MSJD model. The model can be used for systems in which interstitial jump diffusion of impurity particles occurs. In Part II the theoretical results are compared with those for quasielastic neutron scattering from the αNbHsub(x) system. (author)
Energy Technology Data Exchange (ETDEWEB)
Brill, J. W.; Shahi, Maryam; Yao, Y. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055 (United States); Payne, Marcia M.; Anthony, J. E. [Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055 (United States); Edberg, Jesper; Crispin, Xavier [Department of Science and Technology, Organic Electronics, Linköping University, SE-601 74 Norrköping (Sweden)
2015-12-21
We have used a photothermal technique, in which chopped light heats the front surface of a small (∼1 mm{sup 2}) sample and the chopping frequency dependence of thermal radiation from the back surface is measured with a liquid-nitrogen-cooled infrared detector. In our system, the sample is placed directly in front of the detector within its dewar. Because the detector is also sensitive to some of the incident light, which leaks around or through the sample, measurements are made for the detector signal that is in quadrature with the chopped light. Results are presented for layered crystals of semiconducting 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pn) and for papers of cellulose nanofibrils coated with semiconducting poly(3,4-ethylene-dioxythiophene):poly(styrene-sulfonate) (NFC-PEDOT). For NFC-PEDOT, we have found that the transverse diffusivity, smaller than the in-plane value, varies inversely with thickness, suggesting that texturing of the papers varies with thickness. For TIPS-pn, we have found that the interlayer diffusivity is an order of magnitude larger than the in-plane value, consistent with previous estimates, suggesting that low-frequency optical phonons, presumably associated with librations in the TIPS side groups, carry most of the heat.
DWARF, 1-D Few-Group Neutron Diffusion with Thermal Feedback for Burnup and Xe Oscillation
International Nuclear Information System (INIS)
Anderson, E.C.; Putnam, G.E.
1975-01-01
1 - Description of problem or function: DWARF allows one-dimensional simulation of reactor burnup and xenon oscillation problems in slab, cylindrical, or spherical geometry using a few-group diffusion theory model. 2 - Method of solution: The few-group, neutron diffusion theory equations are reduced to a system of finite-difference equations that are solved for each group by the Gauss method at each time point. Fission neutron source iteration can be accelerated with Chebyshev extrapolation. A thermal feedback iterative loop is used to obtain consistent solutions for the distributions of reactor power, neutron flux, and fuel and coolant properties with the neutron group constants functions of the latter. Solutions for the new nuclide concentrations of a time-point are made with the flux assumed constant in the time interval. 3 - Restrictions on the complexity of the problem - Maxima of: 4 groups; 40 regions; 50 macroscopic materials (Only 10 are functions of the feedback variables); 50 nuclides per region; 250 mesh points
Energy Technology Data Exchange (ETDEWEB)
Ertaud, A; Beauge, R; Fauquez, H; De Laboulay, H; Mercier, C; Vautrey, L
1948-11-01
The diffusion length of thermal neutrons inside a given industrial graphite is determined by measuring the neutron density inside a parallelepipedal piling up of graphite bricks (2.10 x 2.10 x 2.442 m). A 3.8 curies (Ra {alpha} {yields} Be) source is placed inside the parallelepipedal block of graphite and thin manganese detectors are used. Corrections are added to the unweighted measurements to take into account the effects of the damping of supra-thermal neutrons in the measurement area. These corrections are experimentally deduced from the differential measurements made with a cadmium screen interposed between the source and the first plane of measurement. An error analysis completes the report. The diffusion length obtained is: L = 45.7 cm {+-} 0.3. The average density of the graphite used is 1.76 and the average apparent density of the piling up is 1.71. (J.S.)
Energy Technology Data Exchange (ETDEWEB)
Koechlin, J C; Martelly, J; Duggal, V P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1955-07-01
The diffusion length of thermal neutrons in the beryllium oxide has been obtained while studying the spatial distribution of the neutrons in a massive parallelepiped of this matter placed before the thermal column of the reactor core of Saclay. The mean density of the beryllium oxide (BeO) is 2,95 gr/cm{sup 3}, the mean density of the massif is 2,92 gr/cm{sup 3}. The value of the diffusion length, deducted of the done measures, is: L = 32,7 {+-} 0,5 cm (likely gap). Some remarks are formulated about the influence of the spectral distribution of the neutrons flux used. (authors) [French] La longueur de diffusion des neutrons thermiques dans l'oxyde de beryllium a ete obtenue en etudiant la repartition spatiale des neutrons dans un massif parallelepipedique de cette matiere placee devant la colonne thermique de la Pile de Saclay. La densite moyenne de l'oxyde de beryllium (BeO) est de 2,95 gr/cm{sup 3}, la densite moyenne du massif de 2,92 gr/cm{sup 3}. La valeur de la longueur de diffusion, deduite des mesures effectuees est: L 32,7 {+-} 0,5 cm (ecart probable). Des remarques sont formulees quant a l'influence de la repartition spectrale du flux de neutrons utilise. (auteurs)
Influence of thermal radiation on soot production in Laminar axisymmetric diffusion flames
International Nuclear Information System (INIS)
Demarco, R.; Nmira, F.; Consalvi, J.L.
2013-01-01
The aim of this paper is to study the effect of radiative heat transfer on soot production in laminar axisymmetric diffusion flames. Twenty-four C 1 –C 3 hydrocarbon–air flames, consisting of normal (NDF) and inverse (IDF) diffusion flames at both normal gravity (1 g) and microgravity (0 g), and covering a wide range of conditions affecting radiative heat transfer, were simulated. The numerical model is based on the Steady Laminar Flamelet (SLF) model, a semi-empirical two-equation acetylene/benzene based soot model and the Statistical Narrow Band Correlated K (SNBCK) model coupled to the Finite Volume Method (FVM) to compute thermal radiation. Predictions relative to velocity, temperature, soot volume fraction and radiative losses are on the whole in good agreement with the available experimental data. Model results show that, for all the flames considered, thermal radiation is a crucial process with a view to providing accurate predictions for temperatures and soot concentrations. It becomes increasingly significant from IDFs to NDFs and its influence is much greater as gravity is reduced. The radiative contribution of gas prevails in the weakly-sooting IDFs and in the methane and ethane NDFs, whereas soot radiation dominates in the other flames. However, both contributions are significant in all cases, with the exception of the 1 g IDFs investigated where soot radiation can be ignored. The optically-thin approximation (OTA) was also tested and found to be applicable as long as the optical thickness, based on flame radius and Planck mean absorption coefficient, is less than 0.05. The OTA is reasonable for the IDFs and for most of the 1 g NDFs, but it fails to predict the radiative heat transfer for the 0 g NDFs. The accuracy of radiative-property models was then assessed in the latter cases. Simulations show that the gray approximation can be applied to soot but not to combustion gases. Both the non-gray and gray soot versions of the Full Spectrum Correlated
Eskew, Matthew W.; Harrison, Jason; Simoyi, Reuben H.
2016-11-01
Oxidation reactions of thiourea by chlorite in a Hele-Shaw cell are excitable, autocatalytic, exothermic, and generate a lateral instability upon being triggered by the autocatalyst. Reagent concentrations used to develop convective instabilities delivered a temperature jump at the wave front of 2.1 K. The reaction zone was 2 mm and due to normal cooling after the wave front, this generated a spike rather than the standard well-studied front propagation. The reaction front has solutal and thermal contributions to density changes that act in opposite directions due to the existence of a positive isothermal density change in the reaction. The competition between these effects generates thermal plumes. The fascinating feature of this system is the coexistence of plumes and fingering in the same solution which alternate in frequency as the front propagates, generating hot and cold spots within the Hele-Shaw cell, and subsequently spatiotemporal inhomogeneities. The small ΔT at the wave front generated thermocapillary convection which competed effectively with thermogravitational forces at low Eötvös Numbers. A simplified reaction-diffusion-convection model was derived for the system. Plume formation is heavily dependent on boundary effects from the cell dimensions. This work was supported by Grant No. CHE-1056366 from the NSF and a Research Professor Grant from the University of KwaZulu-Natal.
International Nuclear Information System (INIS)
Youchison, D.L.; Guiniiatouline, R.; Watson, R.D.
1994-01-01
Thermal response and thermal fatigue tests of four 5 mm thick beryllium tiles on a Russian divertor mock-up were completed on the Electron Beam Test System at Sandia National Laboratories. The beryllium tiles were diffusion bonded onto an OFHC copper saddleblock and a DSCu (MAGT) tube containing a porous coating. Thermal response tests were performed on the tiles to an absorbed heat flux of 5 MW/m 2 and surface temperatures near 300 degrees C using 1.4 MPa water at 5.0 m/s flow velocity and an inlet temperature of 8-15 degrees C. One tile was exposed to incrementally increasing heat fluxes up to 9.5 MW/m 2 and surface temperatures up to 690 degrees C before debonding at 10 MW/m 2 . A third tile debonded after 9200 thermal fatigue cycles at 5 MW/m 2 , while another debonded after 6800 cycles. In all cases, fatigue failure occurred in the intermetallic layers between the beryllium and copper. No fatigue cracking of the bulk beryllium was observed. During thermal cycling, a gradual loss of porous coating produced increasing sample temperatures. These experiments indicate that diffusion-bonded beryllium tiles can survive several thousand thermal cycles under ITER relevant conditions without failure. However, the reliability of the diffusion bonded Joint remains a serious issue
Energy Technology Data Exchange (ETDEWEB)
Zhong, Hui; Fu, Yanqing [Key laboratory of electromagnetic processing of materials (EPM), Ministry of Education, Northeastern University, Shenyang 110819 (China); Department of Physics and Chemistry of Materials, School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); Li, Guojian; Liu, Tie [Key laboratory of electromagnetic processing of materials (EPM), Ministry of Education, Northeastern University, Shenyang 110819 (China); Cui, Weibin, E-mail: cuiweibin@epm.neu.edu.cn [Key laboratory of electromagnetic processing of materials (EPM), Ministry of Education, Northeastern University, Shenyang 110819 (China); Department of Physics and Chemistry of Materials, School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); Liu, Wei; Zhang, Zhidong [Shenyang National Laboratory for Materials Science, Institute of Metal Research (IMR), Chinese Academy of Sciences (CAS), Shenyang 110016 (China); Wang, Qiang, E-mail: wangq@mail.neu.edu.cn [Key laboratory of electromagnetic processing of materials (EPM), Ministry of Education, Northeastern University, Shenyang 110819 (China)
2017-03-15
A proposed Nd{sub 2}Fe{sub 14}B-core/Nd{sub 2}(Fe, Co){sub 14}B-shell microstructure was realized by diffusion-processing textured Nd{sub 14}Fe{sub 77}B{sub 9} single-layer film with Nd{sub 100−x}Co{sub x} (x=10, 20 and 40) alloys to improve the coercivity thermal stability. The ambient coercivity was increased from around 1 T in single-layer film to nearly 2 T in diffusion-processed films, which was due to the Nd-rich grain boundaries as seen from transmission electron microscopy (TEM) images. The coercivity thermal stability was improved by the core/shell microstructure because Nd-rich grain boundaries provided the high ambient coercivity and Co-rich shell provided the improved coercivity stability. - Highlights: • Core–shell microstructure proposed for enhancing the coercivity thermal stability. • Coercivity enhanced to nearly 2 T by diffusion-processing with Nd–Co alloy. • Good squareness and highly textured microstructure obtained. • Nd-rich phases observed by TEM after diffusion process. • Coercivity thermal stability improved with minor Co addition in grain boundary regions.
CARMEN-SYSTEM, Programs System for Thermal Neutron Diffusion and Burnup with Feedback
International Nuclear Information System (INIS)
Ahnert, Carol; Aragones, Jose M.
1983-01-01
1 - Description of problem or function: CARMEN is a system of programs developed for the neutronic calculation of PWR cycles. It includes the whole chain of analysis from cell calculations to core calculations with burnup. The core calculations are based on diffusion theory with cross sections depending on the relevant space-dependent feedback effects which are present at each moment along the cycles. The diffusion calculations are in one, two or three dimensions and in two energy groups. The feedback effects which are treated locally are: burnup, water density, power density and fission products. In order to study in detail these parameters the core should be divided into as many zones as different cross section sets are expected to be required in order to reproduce reality correctly. A relevant difference in any feedback parameter between zones produces different cross section sets for the corresponding zones. CARMEN is also capable to perform the following calculations: - Multiplication factor by burnup step with fixed boron concentration - Buckling and control rod insertion - Buckling search by burnup step - Boron search by burnup step - Control rod insertion search by burnup step. 2 - Method of solution: The cell code (LEOPARD-TRACA) generates the fuel assembly cross sections versus burnup. This is the basic library to be used in the CARMEN code proper. With a planar distribution guess for power density, water density and fluxes, the macroscopic cross sections by zone are calculated by CARMEN, and then a diffusion calculation is done in the whole geometry. With the distribution of power density, heat accumulated in the coolant and the thermal and fast fluxes determined in the diffusion calculation, CARMEN calculates the values of the most relevant parameters that influence the macroscopic cross sections by zone: burnup, water density, effective fuel temperature and fission product concentrations. If these parameters by zone are different from the reference
Energy Technology Data Exchange (ETDEWEB)
Pipon, Yves [Ecole doctorale de physique et d' astrophysique, Universite Claude Bernard Lyon-I, Lyon (France)
2006-12-15
This work concerns the study of the thermal and radiation enhanced diffusion of {sup 36}Cl in uranium dioxide. It is a contribution to PRECCI programme (research programme on the long-term behaviour of the spent nuclear fuel). {sup 36}Cl is a long lived volatile activation product (T = 300 000 years) able to contribute significantly to the instant release fraction in geological disposal conditions. We simulated the presence of {sup 36}Cl by implanting a quantity of {sup 37}Cl comparable to the impurity content of chlorine in UO{sub 2}. In order to evaluate the diffusion properties of chlorine in the fuel and in particular to assess the influence of the irradiation defects, we performed two kinds of experiments: - the influence of the temperature was studied by carrying out thermal annealings in the temperature range 900 - 1300 deg. C; we showed that implanted chlorine was mobile from temperatures as low as 1000 deg. C and determined a thermal diffusion coefficient D{sub 1000} {sub deg.} {sub C} around 10{sup -16} cm{sup 2}s{sup -1} and deduced an activation energy of 4.3 eV. This value is one of lowest compared to that of volatile fission products such as iodine or the xenon. These parameters reflect the very mobile behaviour of chlorine; - the irradiation effects induced by fission products were studied by irradiating the samples with {sup 127}I (energy of 63.5 MeV). We showed that the implanted chlorine diffusion in the temperature range 30 - 250 deg. C is not purely athermal. In these conditions, the diffusion coefficient D{sub 250} {sub deg.} {sub C} for the implanted chlorine is around 10{sup -14} cm{sup 2}s{sup -1} and the activation energy is calculated to be 0.1 eV. Moreover, at 250 deg. C, we observed an important transport of the pristine chlorine from the bulk towards the surface. This chlorine comes from a zone where the defects are mainly produced by the nuclear energy loss process at the end of iodine range. We showed the importance of the
International Nuclear Information System (INIS)
Salazar, Agustín; Oleaga, Alberto; Mendioroz, Arantza; Apiñaniz, Estibaliz
2017-01-01
The photopyroelectric (PPE) technique in the front configuration consists in illuminating one surface of a pyroelectric slab while the other surface is in contact with the test sample. This method has been widely used to measure the thermal effusivity of liquids. Recently, it has been extended to measure the thermal effusivity of solids, by taking into account the influence of the coupling fluid layer used to guarantee the thermal contact. In both cases, the sample (liquid or solid) must be very thick. In this work, we propose a classical frequency scan of a thin sample slab to retrieve the thermal diffusivity and effusivity simultaneously. We use the amplitude and the phase of the front PPE signal, which depend on four parameters: the sample diffusivity and effusivity, the coupling fluid thickness and the coefficient of heat losses. It is demonstrated that the four quantities are not correlated. PPE measurements performed on a set of calibrated solids confirm the ability of the method to obtain the thermal diffusivity and effusivity of solids accurately. (paper)
International Nuclear Information System (INIS)
Gambier, D.J.; Evrard, M.P.; Adam, J.
1990-01-01
The power deposition profile in the ion cyclotron range of frequencies (ICRF) has been investigated experimentally in JET by means of a square wave modulated RF perturbation. The study has been conducted in D(H) and D( 3 He) plasmas for two heating scenarios. In D( 3 He) plasmas and for central heating in a scenario where mode conversion to Bernstein waves is accessible, the direct power deposition profile on electrons has been derived. It accounts for 15% of the total coupled power and extends over 25% of the minor radius. Outside the RF power deposition zone, the electron thermal diffusivity χ e inside the inversion radius surface (r i ) can be estimated through observation of the diffusive electronic transport. In discharges without monster sawteeth and for a low central temperature gradient (∇T e (r ≤ r i ) ≤ ∇T e (r ≥ r i ) approx. = 5 keV·m -1 ) the value obtained is small (approx. =0.24 +- 0.05 m 2 · s -1 ), typically ten times lower than χ e values deduced from heat pulse propagation in similar discharges at radii larger than the inversion radius. For the D(H) minority heating scheme, a large fraction of the ICRF modulated power is absorbed by minority ions, and the minority tail is modulated with a characteristic ion-electron (i-e) slowing-down time. In this scheme, electron heating occurs only through collisions with the minority ion tail and no modulation of the electron temperature is observed in sawtoothing discharges. This is interpreted as a consequence of the long i-e equipartition time, acting as an integrator for the modulated ICRF signal. Finally, a correlation between the time of the sawtooth crash and the periodic turn-off of the ICRF power is found and its consequence for modulation experiments is reviewed. (author). 22 refs, 16 figs
Influence of thermal radiation on soot production in Laminar axisymmetric diffusion flames
Demarco, R.; Nmira, F.; Consalvi, J. L.
2013-05-01
The aim of this paper is to study the effect of radiative heat transfer on soot production in laminar axisymmetric diffusion flames. Twenty-four C1-C3 hydrocarbon-air flames, consisting of normal (NDF) and inverse (IDF) diffusion flames at both normal gravity (1 g) and microgravity (0 g), and covering a wide range of conditions affecting radiative heat transfer, were simulated. The numerical model is based on the Steady Laminar Flamelet (SLF) model, a semi-empirical two-equation acetylene/benzene based soot model and the Statistical Narrow Band Correlated K (SNBCK) model coupled to the Finite Volume Method (FVM) to compute thermal radiation. Predictions relative to velocity, temperature, soot volume fraction and radiative losses are on the whole in good agreement with the available experimental data. Model results show that, for all the flames considered, thermal radiation is a crucial process with a view to providing accurate predictions for temperatures and soot concentrations. It becomes increasingly significant from IDFs to NDFs and its influence is much greater as gravity is reduced. The radiative contribution of gas prevails in the weakly-sooting IDFs and in the methane and ethane NDFs, whereas soot radiation dominates in the other flames. However, both contributions are significant in all cases, with the exception of the 1 g IDFs investigated where soot radiation can be ignored. The optically-thin approximation (OTA) was also tested and found to be applicable as long as the optical thickness, based on flame radius and Planck mean absorption coefficient, is less than 0.05. The OTA is reasonable for the IDFs and for most of the 1 g NDFs, but it fails to predict the radiative heat transfer for the 0 g NDFs. The accuracy of radiative-property models was then assessed in the latter cases. Simulations show that the gray approximation can be applied to soot but not to combustion gases. Both the non-gray and gray soot versions of the Full Spectrum Correlated k (FSCK
Hofmeister, Anne M.; Dong, Jianjun; Branlund, Joy M.
2014-04-01
We show that laser-flash analysis measurements of the temperature (T) dependence of thermal diffusivity (D) for diverse non-metallic (e.g., silicates) single-crystals is consistently represented by D(T) = FT-G + HT above 298 K, with G ranging from 0.3 to 2, depending on structure, and H being ˜10-4 K-1 for 51 single-crystals, 3 polycrystals, and two glasses unaffected by disorder or reconstructive phase transitions. Materials exhibiting this behavior include complex silicates with variable amounts of cation disorder, perovskite structured materials, and graphite. The high-temperature term HT becomes important by ˜1300 K, above which temperature its contribution to D(T) exceeds that of the FT-G term. The combination of the FT-G and HT terms produces the nearly temperature independent high-temperature region of D previously interpreted as the minimal phonon mean free path being limited by the finite interatomic spacing. Based on the simplicity of the fit and large number of materials it represents, this finding has repercussions for high-temperature models of heat transport. One explanation is that the two terms describing D(T) are associated with two distinct microscopic mechanisms; here, we explore the possibility that the thermal diffusivity of an electrical insulator could include both a contribution of lattice phonons (the FT-G term) and a contribution of diffusive bulk phonon-polaritons (BPP) at infrared (IR) frequencies (the HT term). The proposed BPP diffusion exists over length scales smaller than the laboratory sample sizes, and transfers mixed light and vibrational energy at a speed significantly smaller than the speed of light. Our diffusive IR-BPP hypothesis is consistent with other experimental observations such as polarization behavior, dependence of D on the number of IR peaks, and H = 0 for Ge and Si, which lack IR fundamentals. A simple quasi-particle thermal diffusion model is presented to begin understanding the contribution from bulk phonon
A 3-D wellbore simulator (WELLTHER-SIM) to determine the thermal diffusivity of rock-formations
Wong-Loya, J. A.; Santoyo, E.; Andaverde, J.
2017-06-01
Acquiring thermophysical properties of rock-formations in geothermal systems is an essential task required for the well drilling and completion. Wellbore thermal simulators require such properties for predicting the thermal behavior of a wellbore and the formation under drilling and shut-in conditions. The estimation of static formation temperatures also needs the use of these properties for the wellbore and formation materials (drilling fluids and pipes, cements, casings, and rocks). A numerical simulator (WELLTHER-SIM) has been developed for modeling the drilling fluid circulation and shut-in processes of geothermal wellbores, and for the in-situ determination of thermal diffusivities of rocks. Bottomhole temperatures logged under shut-in conditions (BHTm), and thermophysical and transport properties of drilling fluids were used as main input data. To model the thermal disturbance and recovery processes in the wellbore and rock-formation, initial drilling fluid and static formation temperatures were used as initial and boundary conditions. WELLTHER-SIM uses these temperatures together with an initial thermal diffusivity for the rock-formation to solve the governing equations of the heat transfer model. WELLTHER-SIM was programmed using the finite volume technique to solve the heat conduction equations under 3-D and transient conditions. Thermal diffusivities of rock-formations were inversely computed by using an iterative and efficient numerical simulation, where simulated thermal recovery data sets (BHTs) were statistically compared with those temperature measurements (BHTm) logged in some geothermal wellbores. The simulator was validated using a well-documented case reported in the literature, where the thermophysical properties of the rock-formation are known with accuracy. The new numerical simulator has been successfully applied to two wellbores drilled in geothermal fields of Japan and Mexico. Details of the physical conceptual model, the numerical
Enhanced thermal diffusivity of copperbased composites using copper-RGO sheets
Kim, Sangwoo; Kwon, Hyouk-Chon; Lee, Dohyung; Lee, Hyo-Soo
2017-11-01
The synthesis of copper-reduced graphene oxide (RGO) sheets was investigated in order to control the agglutination of interfaces and develop a manufacturing process for copper-based composite materials based on spark plasma sintering. To this end, copper-GO (graphene oxide) composites were synthesized using a hydrothermal method, while the copper-reduced graphene oxide composites were made by hydrogen reduction. Graphene oxide-copper oxide was hydrothermally synthesized at 80 °C for 5 h, and then annealed at 800 °C for 5 h in argon and hydrazine rate 9:1 to obtain copper-RGO flakes. The morphology and structure of these copper-RGO sheets were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. After vibratory mixing of the synthesized copper-RGO composites (0-2 wt%) with copper powder, they were sintered at 600 °C for 5 min under100 MPa of pressure by spark plasma sintering process. The thermal diffusivity of the resulting sintered composite was characterized by the laser flash method at 150 °C.
Weres, Jerzy; Kujawa, Sebastian; Olek, Wiesław; Czajkowski, Łukasz
2016-04-01
Knowledge of physical properties of biomaterials is important in understanding and designing agri-food and wood processing industries. In the study presented in this paper computational methods were developed and combined with experiments to enhance identification of agri-food and forest product properties, and to predict heat and water transport in such products. They were based on the finite element model of heat and water transport and supplemented with experimental data. Algorithms were proposed for image processing, geometry meshing, and inverse/direct finite element modelling. The resulting software system was composed of integrated subsystems for 3D geometry data acquisition and mesh generation, for 3D geometry modelling and visualization, and for inverse/direct problem computations for the heat and water transport processes. Auxiliary packages were developed to assess performance, accuracy and unification of data access. The software was validated by identifying selected properties and using the estimated values to predict the examined processes, and then comparing predictions to experimental data. The geometry, thermal conductivity, specific heat, coefficient of water diffusion, equilibrium water content and convective heat and water transfer coefficients in the boundary layer were analysed. The estimated values, used as an input for simulation of the examined processes, enabled reduction in the uncertainty associated with predictions.
Using the thermal diffusion cloud chamber to study the ion-induced nucleation by radon decay
International Nuclear Information System (INIS)
Wu, Yefei.
1991-01-01
Thermal diffusion cloud chamber is steady-state device and has been extensively used for nucleation research. In order to study the ion-induced nucleation by radon decay, a new chamber was designed with improved both upper and bottom plates, the system of circulating fluid, the gasketting, the temperature measurement and the insulation. An alternative method of using oxygen as carrier gas was examined. Therefore, the heavy carrier gas including nitrogen, oxygen, neon, argon and air can be used to study radon radiolysis-induced nucleation for the water or organic compounds in the TDCC. The effects of the pressure and temperature ranges on the density, supersaturation, temperature and partial pressure profile for the water-oxygen-helium in the TDCC have been examined. Based on the classical theory, the rate profile of ion-induced nucleation by radon decays was calculated and compared with the homogeneous nucleation. From measured indoor concentrations of Volatile Organic Compounds (VOC), thermodynamic theory models were used to assess the possibility that these compounds will form ultrafine particles in indoor air by ion-induced nucleation. The energy, number of molecules and equilibrium radius of clusters have been calculated based on Such and Thomson theories. These two sets of values have been compared. Ion cluster radii corresponding to 1--3 VOC molecules are in range of 3--5 x 10 -8 cm. 43 refs., 18 figs., 5 tabs
Optimum pressure for total-reflux operated thermal diffusion column for isotope separation
International Nuclear Information System (INIS)
Yamamoto, Ichiro; Makino, Hitoshi; Kanagawa, Akira
1990-01-01
A formula for prediction of the optimum operating pressure P opt of the thermal diffusion columns at total reflux is derived based on the approximate formulae for the column constants which can be evaluated analytically. The formula is expressed explicitly in terms of (1) physical properties of gases to be separated, (2) ratio of radii between hot wire and cold wall of the column, and (3) the ratio of the temperature difference to the cold wall temperature. The result is compared with experimental data; (1) binary monatomic gas systems, (2) multicomponent monatomic gas systems, (3) isotopically substituted polyatomic systems, (4) systems of low atomic or molecular weight, and (5) mixtures of unlike gases; mainly obtained by Rutherford and coworkers. Although the formula is based on the rather rough approximation for the column constants, the optimum pressures predicted by the present formula are in successfully good agreement with the experimental data even for the systems of low atomic or molecular weight and that of mixtures of unlike gases. (author)
Allen, Philip B.
2018-04-01
Simulations [e.g., X. W. Zhou et al., Phys. Rev. B 79, 115201 (2009), 10.1103/PhysRevB.79.115201] show nonlocal effects of the ballistic/diffusive crossover. The local temperature has nonlinear spatial variation not contained in the local Fourier law j ⃗(r ⃗) =-κ ∇ ⃗T (r ⃗) . The heat current j ⃗(r ⃗) depends not just on the local temperature gradient ∇ ⃗T (r ⃗) but also on temperatures at points r⃗' within phonon mean free paths, which can be micrometers long. This paper uses the Peierls-Boltzmann transport theory in nonlocal form to analyze the spatial variation Δ T (r ⃗) . The relaxation-time approximation (RTA) is used because the full solution is very challenging. Improved methods of extrapolation to obtain the bulk thermal conductivity κ are proposed. Callaway invented an approximate method of correcting RTA for the q ⃗ (phonon wave vector or crystal momentum) conservation of N (Normal as opposed to Umklapp) anharmonic collisions. This method is generalized to the nonlocal case where κ (k ⃗) depends on the wave vector of the current j ⃗(k ⃗) and temperature gradient i k ⃗Δ T (k ⃗) .
Directory of Open Access Journals (Sweden)
Holmes Jesse
2017-01-01
Full Text Available The neutron scattering properties of water ice are of interest to the nuclear criticality safety community for the transport and storage of nuclear materials in cold environments. The common hexagonal phase ice Ih has locally ordered, but globally disordered, H2O molecular orientations. A 96-molecule supercell is modeled using the VASP ab initio density functional theory code and PHONON lattice dynamics code to calculate the phonon vibrational spectra of H and O in ice Ih. These spectra are supplied to the LEAPR module of the NJOY2012 nuclear data processing code to generate thermal neutron scattering laws for H and O in ice Ih in the incoherent approximation. The predicted vibrational spectra are optimized to be representative of the globally averaged ice Ih structure by comparing theoretically calculated and experimentally measured total cross sections and inelastic neutron scattering spectra. The resulting scattering kernel is then supplied to the MC21 Monte Carlo transport code to calculate time eigenvalues for the fundamental mode decay in ice cylinders at various temperatures. Results are compared to experimental flux decay measurements for a pulsed-neutron die-away diffusion benchmark.
Thermal diffusivity and butterfly velocity in anisotropic Q-lattice models
Jeong, Hyun-Sik; Ahn, Yongjun; Ahn, Dujin; Niu, Chao; Li, Wei-Jia; Kim, Keun-Young
2018-01-01
We study a relation between the thermal diffusivity ( D T ) and two quantum chaotic properties, Lyapunov time (τ L ) and butterfly velocity ( v B ) in strongly correlated systems by using a holographic method. Recently, it was shown that E_i:={D}_{T,i}/({v}{^{B,i}}^2{τ}_L)(i=x,y) is universal in the sense that it is determined only by some scaling exponents of the IR metric in the low temperature limit regardless of the matter fields and ultraviolet data. Inspired by this observation, by analyzing the anisotropic IR scaling geometry carefully, we find the concrete expressions for E_i in terms of the critical dynamical exponents z i in each direction, E_i={z}_i/2({z}_i-1) . Furthermore, we find the lower bound of E_i is always 1 /2, which is not affected by anisotropy, contrary to the η/s case. However, there may be an upper bound determined by given fixed anisotropy.
Design of a system to measure thermal diffusivity of metals in the form of miniature disks
International Nuclear Information System (INIS)
Zimmerschied, M.K.
1986-03-01
This report describes the design of a system to measure the thermal diffusivity of stainless steel alloy specimens in the form of 3-mm-diameter, 0.3-mm-thick disks. To measure these tiny specimens, the flash method devised by Parker et al. is employed; in this method, one surface of the specimen is exposed to a pulse of energy and the temperature response of the opposite surface is recorded. Derivations of the governing equations are included; these derivations differ from the work of Parker et al. bcause the heat pulse irradiating the specimen in this system is a square wave (in intensity vs time) rather than triangular, and the equation for estimating the maximum temperature of the irradiated surface of the specimen was simplified by the elimination of several variables. The design, selection, or modification of each of the components of the system to meet the criteria of the flash method is described. The capability of this system to perform in accordance with the assumptions of the flash method is discussed, and recommendations for improvement of the present system and extension of its capabilities are included
International Nuclear Information System (INIS)
Rice, Jarrett A.; Pokorny, Richard; Schweiger, Michael J.; Hrma, Pavel R.
2014-01-01
The heat conductivity (λ) and the thermal diffusivity (a) of reacting glass batch, or melter feed, control the heat flux into and within the cold cap, a layer of reacting material floating on the pool of molten glass in an all-electric continuous waste glass melter. After previously estimating λ of melter feed at temperatures up to 680 deg C, we focus in this work on the λ(T) function at T > 680 deg C, at which the feed material becomes foamy. We used a customized experimental setup consisting of a large cylindrical crucible with an assembly of thermocouples, which monitored the evolution of the temperature field while the crucible with feed was heated at a constant rate from room temperature up to 1100°C. Approximating measured temperature profiles by polynomial functions, we used the heat transfer equation to estimate the λ(T) approximation function, which we subsequently optimized using the finite-volume method combined with least-squares analysis. The heat conductivity increased as the temperature increased until the feed began to expand into foam, at which point the conductivity dropped. It began to increase again as the foam turned into a bubble-free glass melt. We discuss the implications of this behavior for the mathematical modeling of the cold cap
Determination of the ion thermal diffusivity from neutron emission profiles in decay
Energy Technology Data Exchange (ETDEWEB)
Sasao, M. (National Inst. for Fusion Science, Nagoya (Japan)); Adam, J.M. (AEA Industrial Technology, Harwell (United Kingdom)); Conroy, S.; Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Belle, P. van (Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking)
1992-01-01
Spatial profiles of neutron emission are routinely obtained at the Joint European Torus (JET) from line-integrated emissivities measured with a multi-channel instrument. It is shown that the manner in which the emission profiles relax following termination of strong heating with Neutral Beam Injection (NBI) permits the local thermal diffusivity ([chi][sub i]) to be obtained with an accuracy of about 20%. The radial profiles of [chi][sub i] for small minor radius (r/a < 0.6) were found to be flat and to take values between 0.3 and 1.1 m[sup 2]/s for H-mode plasmas with plasma current I[sub p] = 3.1 MA and toroidal field B[sub T] = 2.3T. The experimental value of [chi][sub i] is smallest for Z[sub eff] = 2.2 and increases weakly with increasing Z[sub eff]. The experimental results disagree by two orders of magnitude with predictions from an ion temperature gradient driven turbulence model. (author) 6 refs., 3 figs.
International Nuclear Information System (INIS)
Rojas-Trigos, J.B.; Marín, E.; Mansanares, A.M.; Cedeño, E.; Juárez-Gracia, G.; Calderón, A.
2014-01-01
Highlights: • A model for photopyroelectric thermal characterization of fluids is presented. • A slanted detector configuration is considered with a finite measurement cell. • The mean temperature distribution in the photopyroelectric detector, as function of the beam spot position, is calculated. • The influence of the excitation beam spot size, the thermal diffusion length and size of the sample is discussed. • The high lateral resolution of the method observed in experiments is explain. - Abstract: This work presents an extended description about the theoretical aspects related to the generation of the photopyroelectric signal in a recently proposed wedge-like heat transmission detection configuration, which recreates the well-known Angstrom method (widely used for solid samples) for accurate thermal diffusivity measurement in gases and liquids. The presented model allows for the calculation of the temperature profile detected by the pyroelectric sensor as a function of the excitation beam position, and the study of the influence on it of several parameters, such as spot size, thermal properties of the absorber layer, and geometrical parameters of the measurement cell. Through computer simulations, it has been demonstrated that a narrow temperature distribution is created at the sensor surface, independently of the lateral diffusion of heat taking place at the sample's surface
Energy Technology Data Exchange (ETDEWEB)
Kondo, Masatoshi, E-mail: kondo.masatoshi@nr.titech.ac.jp [Tokyo Institute of Technology, 2-12-1, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8550 (Japan); Nakajima, Yuu; Tsuji, Mitsuyo [Tokai University, 4-1-1 Kitakaname, Hiratsuka-shi, Kanagawa 259-1292 (Japan); Nozawa, Takashi [Japan Atomic Energy Agency, Rokkasyo-mura, Kamikita-gun, Aomori 039-3212 (Japan)
2016-11-01
Graphical abstract: Thermal diffusivities and thermal conductivities of liquid Pb–Li alloys (Pb–5Li, Pb–11Li and Pb–17Li). - Highlights: • The densities and specific heats of liquid Pb–Li alloys are evaluated based on the previous studies, and mathematically expressed in the equations with the functions of temperature and Li concentration. • The thermal diffusivities of liquid Pb–Li alloys (i.e., Pb–5Li, Pb–11Li and Pb–17Li) are obtained by laser flash method, and mathematically expressed in the equations with the functions of temperature and Li concentration. • The thermal conductivities of liquid Pb–Li alloys were evaluated and mathematically expressed in the equations with the functions of temperature and Li concentration. - Abstract: The thermophysical properties of lead lithium alloy (Pb–Li) are essential for the design of liquid Pb–Li blanket system. The purpose of the present study is to make clear the density, the thermal diffusivity and the heat conductivity of the alloys as functions of temperature and Li concentration. The densities of the solid alloys were measured by means of the Archimedean method. The densities of the alloys at 300 K as a function of Li concentration (0 at% < χ{sub Li} < 28 at%) were obtained in the equation as ρ{sub (300} {sub K)} [g/cm{sup 3}] = −6.02 × 10{sup −2} × χ{sub Li} + 11.3. The density of the liquid alloys was formulated as functions of temperature and Li concentration (0 at% < χ{sub Li} < 30 at%), and expressed in the equation as ρ [g/cm{sup 3}] = (9.00 × 10{sup −6} × T − 7.01 × 10{sup −2}) × χ{sub Li} + 11.4 − 1.19 × 10{sup −3}T. The thermal diffusivity of Pb, Pb–5Li, Pb–11Li and Pb–17Li were measured by means of laser flash method. The thermal diffusivity of Pb–17Li was obtained in the equation as α{sub Pb–17Li} [cm{sup 2}/s] = 3.46 × 10{sup −4}T + 1.05 × 10{sup −1} for the temperature range between 573 K and 773 K. The thermal conductivity of
International Nuclear Information System (INIS)
Shikama, Tatsuo; Namba, Chusei; Kosuda, Michinori; Maeda, Yukio.
1994-01-01
For measurements of thermal diffusivity of miniature-size specimens heavily irradiated by neutrons, a new Q-switched laser-flash instrument was developed. In the present instrument the time-resolution was improved to 0.1 ms by using a laser-pulse width of 25 ns. The realization of high time-resolution made it possible to measure the thermal diffusivity of thin specimens. It is expected that copper of 0.7 mm thick, and SUS 304 of 0.1 mm could be used for the measurements. In case of ATJ graphite, 0.5 mm thick specimen could be used for the reliable measurement in the temperature range of 300-1300 K. (author)
Andújar Márquez, José Manuel; Martínez Bohórquez, Miguel Ángel; Gómez Melgar, Sergio
2016-02-29
This paper presents a methodology and instrumentation system for the indirect measurement of the thermal diffusivity of a soil at a given depth from measuring its temperature at that depth. The development has been carried out considering its application to the design and sizing of very low enthalpy geothermal energy (VLEGE) systems, but it can has many other applications, for example in construction, agriculture or biology. The methodology is simple and inexpensive because it can take advantage of the prescriptive geotechnical drilling prior to the construction of a house or building, to take at the same time temperature measurements that will allow get the actual temperature and ground thermal diffusivity to the depth of interest. The methodology and developed system have been tested and used in the design of a VLEGE facility for a chalet with basement at the outskirts of Huelva (a city in the southwest of Spain). Experimental results validate the proposed approach.
International Nuclear Information System (INIS)
Jorge, M.P.P.
1992-01-01
This study consists of the determination of thermal diffusivity int he temperature range from 77 K to 300 K by the two-beam phase-lag photoacoustic method. Room temperature measurements of NTD (neutron transmutation doping) silicon suggest that the doping process does not affect its thermal properties. For the superconductor Y Ba 2 Cu 3 O 7 - x it has been verified that the sample density affects its thermal diffusivity. The validity of the experimental method on the Li K SO 4 crystal has been examined by using the thermal diffusivity of a Li F crystal and an Y 2 O 3 ceramic, at room temperature. The behavior of the thermal diffusivity as a function of the temperature for the Li K SO 4 crystal shows two anomalies which correspond at phase-transitions of this crystal in the studied temperature range. (author)
International Nuclear Information System (INIS)
Kato, Y.; Araki, N.; Kobayashi, K.; Makino, A.
1985-01-01
Design conditions of a cylindrical ceramic cell are estimated which can be used to measure the absolute value of thermal diffusivity of molten salts by applying the stepwise heating method. Molten salt is expected to be used in nuclear systems such as the Molten-Salt Reactor, the Accelerator Molten-Salt Breeder, the Fusion Reactor Blanket Coolant, the Fuel Reprocessing System, and so on
Czech Academy of Sciences Publication Activity Database
Dědeček, Petr; Rajver, D.; Čermák, Vladimír; Šafanda, Jan; Krešl, Milan
2013-01-01
Roč. 10, č. 2 (2013), 025012/1-025012/9 ISSN 1742-2132 R&D Projects: GA ČR(CZ) GAP210/11/0183; GA MŠk LM2010008 Institutional support: RVO:67985530 Keywords : ground-air temperature coupling * thermal diffusivity * conductive-convective heat transfer Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.895, year: 2013
Energy Technology Data Exchange (ETDEWEB)
Garcia Fite, J
1959-07-01
The diffusion length of thermal neutrons in graphite using the less possible quantity of material has been determined. The proceeding used was the measurement in a graphite pile which has a punctual source of rapid neutrons inside surrounded by a reflector medium (paraffin or water). The measurement was done in the following conditions: a) introducing an aluminium plate between both materials. b) Introducing a cadmium plate between both materials. (Author) 91 refs.
Energy Technology Data Exchange (ETDEWEB)
Jafarian, Mojtaba [Young Researchers and Elite Club, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Rizi, Mohsen Saboktakin, E-mail: M.saboktakin@Pa.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 8415683111 (Iran, Islamic Republic of); Department of Industrial Engineering, Lenjan Branch, Islamic Azad University, Isfahan (Iran, Islamic Republic of); Jafarian, Morteza [Young Researchers and Elite Club, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Honarmand, Mehrdad [Department of Mechanical Engineering, Tiran Branch, Islamic Azad University, Isfahan (Iran, Islamic Republic of); Javadinejad, Hamid Reza; Ghaheri, Ali [Department of Materials Engineering, Isfahan University of Technology, Isfahan 8415683111 (Iran, Islamic Republic of); Department of Industrial Engineering, Lenjan Branch, Islamic Azad University, Isfahan (Iran, Islamic Republic of); Bahramipour, Mohammad Taghi [Materials Engineering Department, Hakim Sabzevari University, Sabzevar, 397 (Iran, Islamic Republic of); Ebrahimian, Marzieh [Department of Materials Engineering, Isfahan University of Technology, Isfahan 8415683111 (Iran, Islamic Republic of); Department of Industrial Engineering, Lenjan Branch, Islamic Azad University, Isfahan (Iran, Islamic Republic of)
2016-06-01
The objective of this study is to investigate the effect of the types thermal tempering of aluminum alloy on microstructure and mechanical properties of AZ31-O Mg and Al 6061-T6 diffusion bonding. Using Optical Microscope (OM) and Scanning Electron Microscopes (SEM) equipped with EDS analysis and line scan the interfaces of joints were evaluated. The XRD analysis was carried out to characterize phase constitution near the interface zone. The mechanical properties of joints were measured using Vickers micro-hardness and shear strength. According to the results in bonding of AZ31-Mg/Al-6061-O, in less plastic deformation in magnesium alloy, diffusion rate of most magnesium atoms occurred to aluminum alloy and formation of diffusion zone with minimum micro-hardness (140 HV) and maximum shear strength (32 MPa) compared to Al 6061-T6/Mg-AZ31 bonding. Evaluation of fracture surfaces indicates an occurrence of failure from the brittle intermetallic phases. - Highlights: • Diffusion bonding AZ31 to Al-6061withoutany interlayer was successful. • Thermal tempered aluminum alloy plays a vital role in the mechanical properties of joint. • Less thickness of reaction layers and micro-hardness in bonding annealed Al- 6061 layers to AZ31 was achieved. • Fracture surfaces indicated that the onset of fracture from intermetallic compounds resulted in fracture of the cleavage.
International Nuclear Information System (INIS)
Jafarian, Mojtaba; Rizi, Mohsen Saboktakin; Jafarian, Morteza; Honarmand, Mehrdad; Javadinejad, Hamid Reza; Ghaheri, Ali; Bahramipour, Mohammad Taghi; Ebrahimian, Marzieh
2016-01-01
The objective of this study is to investigate the effect of the types thermal tempering of aluminum alloy on microstructure and mechanical properties of AZ31-O Mg and Al 6061-T6 diffusion bonding. Using Optical Microscope (OM) and Scanning Electron Microscopes (SEM) equipped with EDS analysis and line scan the interfaces of joints were evaluated. The XRD analysis was carried out to characterize phase constitution near the interface zone. The mechanical properties of joints were measured using Vickers micro-hardness and shear strength. According to the results in bonding of AZ31-Mg/Al-6061-O, in less plastic deformation in magnesium alloy, diffusion rate of most magnesium atoms occurred to aluminum alloy and formation of diffusion zone with minimum micro-hardness (140 HV) and maximum shear strength (32 MPa) compared to Al 6061-T6/Mg-AZ31 bonding. Evaluation of fracture surfaces indicates an occurrence of failure from the brittle intermetallic phases. - Highlights: • Diffusion bonding AZ31 to Al-6061withoutany interlayer was successful. • Thermal tempered aluminum alloy plays a vital role in the mechanical properties of joint. • Less thickness of reaction layers and micro-hardness in bonding annealed Al- 6061 layers to AZ31 was achieved. • Fracture surfaces indicated that the onset of fracture from intermetallic compounds resulted in fracture of the cleavage.
International Nuclear Information System (INIS)
Butenhoff, T.J.
1994-01-01
Hydrothermal processing is being developed as a method for organic destruction for the Hanford Site in Washington. Hydrothermal processing refers to the redox reactions of chemical compounds in supercritical or near-supercritical aqueous solutions. In order to design reactors for the hydrothermal treatment of complicated mixtures found in the Hanford wastes, engineers need to know the thermophysical properties of the solutions under hydrothermal conditions. The author used the laser-induced grating technique to measure the thermal diffusivity and speed of sound of hydrothermal solutions. In this non-invasive optical technique, a transient grating is produced in the hydrothermal solution by optical absorption from two crossed time-coincident nanosecond laser pulses. The grating is probed by measuring the diffraction efficiency of a third laser beam. The grating relaxes via thermal diffusion, and the thermal diffusivity can be determined by measuring the decay of the grating diffraction efficiency as a function of the pump-probe delay time. In addition, intense pump pulses produce counterpropagating acoustic waves that appear as large undulations in the transient grating decay spectrum. The speed of sound in the sample is simply the grating fringe spacing divided by the undulation period. The cell is made from a commercial high pressure fitting and is equipped with two diamond windows for optical access. Results are presented for dilute dye/water solutions with T = 400 C and pressures between 20 and 70 MPa
Ohta, Hiromichi; Ogura, Gaku; Waseda, Yoshio; Suzuki, Mustumi
1990-10-01
A simple cell and easy data processing are described for measuring the thermal diffusivity of a liquid sample at high temperatures using the laser flash method. A cell consists of a liquid sample sandwiched by two metallic plates. The front surface of one metallic plate is exposed to a single pulse of beam laser and the resulting temperature rise of the back surface of the other metallic plate is measured. The logarithmic analysis proposed by James using the initial time region of the temperature response curve of a two layered cell system has been extended to apply to the present three layered cell system in order to estimate the thermal diffusivity value of a liquid sample. Measurements of distilled water and methanol were made first and the results were found to be in good agreement with the reference data. Then, the thermal diffusivities of molten NaNO3 at 593-660 K and of molten KNO3 at 621-694 K were determined and the results also appear to agree reasonably well with those reported in the literature.
Directory of Open Access Journals (Sweden)
Terpiłowski Janusz
2014-09-01
Full Text Available Transient heat transfer is studied and compared in two planeparallel composite walls and one EPIDIAN 53 epoxy resin wall acting as a matrix for both composites. The first of the two walls is made of carbonepoxy composite; the other wall is made of glass-epoxy composite, both with comparable thickness of about 1 mm and the same number of carbon and glass fabric layers (four layers. The study was conducted for temperatures in the range of 20-120 °C. The results of the study of thermal diffusivity which characterizes the material as a heat conductor under transient conditions have a preliminary character. Three series of tests were conducted for each wall. Each series took about 24 h. The results from the three series were approximated using linear functions and were found between (0.7-1.35×10−7m2/s. In the whole range of temperature variation, the thermal diffusivity values for carbon-epoxy composite are from 1.2 to 1.5 times higher than those for the other two materials with nearly the same thermal diffusivity characteristics.
DEFF Research Database (Denmark)
Fuchs, Sven; Balling, Niels; Förster, Andrea
2015-01-01
properties (density, sonic interval transit time, hydrogen index, volume fraction of shale and photoelectric absorption index) using multivariate statistics. The application of these relations allows computing continuous borehole profiles for each rock thermal property. The uncertainties in the prediction...
Pipon, Y.; Toulhoat, N.; Moncoffre, N.; Raimbault, L.; Scheidegger, A. M.; Farges, F.; Carlot, G.
2007-05-01
In a nuclear reactor, 35Cl present as an impurity in the nuclear fuel is activated by thermal neutron capture. During interim storage or geological disposal of the nuclear fuel, 36Cl may be released from the fuel to the geo/biosphere and contribute significantly to the 'instant release fraction'. In order to elucidate the diffusion mechanisms, both irradiation and thermal effects must be assessed. This paper deals with the thermal diffusion of chlorine in depleted UO2. For this purpose, sintered UO2 pellets were implanted with 37Cl at an ion fluence of 1013 cm-2 and successively annealed in the 1175-1475 K temperature range. The implanted chlorine is used to simulate the behaviour of the displaced one due to recoil and to interactions with the fission fragments during reactor operation. The behaviour of the pristine and the implanted chlorine was investigated during thermal annealing. SIMS and μ-XAS (at the Cl-K edge) analyses show that: the thermal migration of implanted chlorine becomes significant at 1275 K; this temperature and the calculated activation energy of 4.3 eV points out the great ability of chlorine to migrate in UO2 at relatively low temperatures, the behaviour of the implanted chlorine which aggregates into 'hot spots' during annealing before its effusion is clearly different from that of the pristine one which remains homogenously distributed after annealing, the 'hot spot' and the pristine chlorine seem to be in different structural environments. Both types of chlorine are assumed to have a valence state of -I, the comparison between an U2O2Cl5 reference compound and the pristine chlorine environment shows a contribution of the U2O2Cl5 to the pristine chlorine.
International Nuclear Information System (INIS)
Pipon, Y.; Toulhoat, N.; Moncoffre, N.; Raimbault, L.; Scheidegger, A.M.; Farges, F.; Carlot, G.
2007-01-01
In a nuclear reactor, 35 Cl present as an impurity in the nuclear fuel is activated by thermal neutron capture. During interim storage or geological disposal of the nuclear fuel, 36 Cl may be released from the fuel to the geo/biosphere and contribute significantly to the 'instant release fraction'. In order to elucidate the diffusion mechanisms, both irradiation and thermal effects must be assessed. This paper deals with the thermal diffusion of chlorine in depleted UO 2 . For this purpose, sintered UO 2 pellets were implanted with 37 Cl at an ion fluence of 10 13 cm -2 and successively annealed in the 1175-1475K temperature range. The implanted chlorine is used to simulate the behaviour of the displaced one due to recoil and to interactions with the fission fragments during reactor operation. The behaviour of the pristine and the implanted chlorine was investigated during thermal annealing. SIMS and μ-XAS (at the Cl-K edge) analyses show that: (1) the thermal migration of implanted chlorine becomes significant at 1275K; this temperature and the calculated activation energy of 4.3eV points out the great ability of chlorine to migrate in UO 2 at relatively low temperatures; (2) the behaviour of the implanted chlorine which aggregates into 'hot spots' during annealing before its effusion is clearly different from that of the pristine one which remains homogenously distributed after annealing; (3) the 'hot spot' and the pristine chlorine seem to be in different structural environments. Both types of chlorine are assumed to have a valence state of -I; (4) the comparison between an U 2 O 2 Cl 5 reference compound and the pristine chlorine environment shows a contribution of the U 2 O 2 Cl 5 to the pristine chlorine
Energy Technology Data Exchange (ETDEWEB)
Fotheringham, Ulrich, E-mail: ulrich.fotheringham@schott.com [SCHOTT AG, 55014 Mainz (Germany); Wurth, Roman; Ruessel, Christian [Otto-Schott-Institut, Jena University, Jena (Germany)
2011-08-10
Highlights: {yields} Macroscopic, routine laboratory methods of the 'Thermal Analysis' type (DSC, DMA) allow a rough description of the kinetics in the nano-sized interstitial spaces of glass ceramics. {yields} These macroscopic measurements support the idea of a rigid zone around the crystals which builds up during ceramization and is part of a negative feedback loop which finally stops crystal growth and Ostwald ripening within the time window of observation. {yields} Ostwald ripening may be provoked by thermally softening said rigid zone. Under certain conditions, this gives rise to a characteristic peak in the DSC. - Abstract: According to a hypothesis by Ruessel and coworkers, the absence of Ostwald ripening during isothermal crystallization of lithium aluminosilicate (LAS) and other glass ceramics indicates the existence of a kinetic hindrance of atomic reorganization in the interstitial spaces between the crystals. Methods of Thermal Analysis (Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA)) which are sensitive to the local atomic rearrangements in the interstitial spaces (including viscous flow) are applied to find support for the idea of kinetic hindrance and the formation of a core shell structure acting as diffusion barrier. Both the DSC-measured calorimetric glass transition and the DMA-measured viscoelastic properties indicate an increase in the time constants of atomic rearrangements and diffusion by at least two orders of magnitude during ceramization. This fits to the above idea. Based on these findings, thermo analytic studies have been performed in order to find out how Ostwald ripening may be provoked.
Energy Technology Data Exchange (ETDEWEB)
Schmid, Fabian; Bierling, Bernd; Spindler, Klaus [Stuttgart Univ. (Germany). Inst. fuer Thermodynamik und Waermetechnik (ITW)
2012-07-01
The diffusion-absorption refrigeration process offers the possibility of a wear-free refrigeration system without electricity and noise. At the Institute for Thermodynamics and Thermal Engineering (Stuttgart, Federal Republic of Germany), a decentralized solar refrigeration system is developed based on this process. The expeller and the thermosiphon pump of this process are integrated in the collector, and thus are heated directly. The diffusion-absorption refrigeration process also can be used for domestic water heating by means of a second cycle in the collector. A cooling capacity of 400 W is to be achieved for each solar collector (2.5 m{sup 2}). Several refrigeration systems can be modular interconnected for higher cooling capacities. As part of the DKV Conference 2011, the construction of the plant, the first measurement data and results were presented. Since then, both the cooling capacity and the coefficient of performance of the diffusion-absorption refrigeration system could be increased significantly. For this, solvent heat exchanger, evaporator, absorber and gas heat exchanger have been optimized in terms of system efficiency. In addition, a stable system operation could be achieved by means of a bypass line. About this line, an exaggerated refrigerant already is removed in the solvent heat exchanger. In addition, a condensate pre-cooler was integrated in order to increase the efficiency. For a detailed investigation of the auxiliary gas cycle facilities, the volume flow and the concentration of the auxiliary gas circuit were examined under utilization of an ultrasonic sensor. In order to evaluate the influence factors by means of a parametric study, the mass transfer in the auxiliary gas circuit was simulated using the two-fluid model. The results of these studies, the current system configuration and the current results are presented in the contribution under consideration.
Energy Technology Data Exchange (ETDEWEB)
Zhao, X.; Liu, J. [School of Materials, University of Manchester, Manchester M1 7HS (United Kingdom); Rickerby, D.S.; Jones, R.J. [Rolls-Royce Plc., PO Box 31, Derby DE24 8BJ (United Kingdom); Xiao, P., E-mail: ping.xiao@manchester.ac.uk [School of Materials, University of Manchester, Manchester M1 7HS (United Kingdom)
2011-09-15
A strain-to-fail method has been employed to examine the interfacial adhesion of electron beam-physical vapor deposited thermal barrier coatings (TBCs) with a Pt-diffused {gamma}/{gamma}' bond coat. Based on a previously established model, the estimated interfacial toughness decreases with oxidation time of TBCs. Furthermore, the interfacial toughness value varies considerably with the use of different Young's moduli in the model. It is believed that the modulus obtained from beam bending represents the columnar structure of the TBC. In this case, the mode I interfacial toughness was found to vary from 10 J m{sup -2} for as-deposited TBCs to 0.79 J m{sup -2} for the 60 h oxidized TBCs. The degradation of adhesion could be attributed to the defect formation and impurity segregation at the TGO/bond coat interface, which is associated with the diffusion of Pt.
Energy Technology Data Exchange (ETDEWEB)
Ding Meng [Department of Physics, Jilin University, Changchun 130023 (China); Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130021 (China); Yao Bin, E-mail: binyao@jlu.edu.c [Department of Physics, Jilin University, Changchun 130023 (China); Zhao Dongxu, E-mail: dxzhao2000@yahoo.com.c [Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130021 (China); Fang Fang; Shen Dezhen; Zhang Zhenzhong [Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130021 (China)
2010-05-31
As-doped sub-micron ZnO rods were realized by a simple thermal diffusion process using a GaAs wafer as an arsenic resource. The surface of the sub-micron ZnO rods became rough and the morphology of As-doped sub-micron ZnO rods changed markedly with increasing diffusion temperature. From the results of energy-dispersive X-ray spectroscopy, X-ray diffraction and photoluminescence, arsenic elements were confirmed to be introduced into the sub-micron ZnO rods. The acceptor ionization energy was deduced to be about 110 meV based on the temperature-dependent PL spectra.
International Nuclear Information System (INIS)
Ding Meng; Yao Bin; Zhao Dongxu; Fang Fang; Shen Dezhen; Zhang Zhenzhong
2010-01-01
As-doped sub-micron ZnO rods were realized by a simple thermal diffusion process using a GaAs wafer as an arsenic resource. The surface of the sub-micron ZnO rods became rough and the morphology of As-doped sub-micron ZnO rods changed markedly with increasing diffusion temperature. From the results of energy-dispersive X-ray spectroscopy, X-ray diffraction and photoluminescence, arsenic elements were confirmed to be introduced into the sub-micron ZnO rods. The acceptor ionization energy was deduced to be about 110 meV based on the temperature-dependent PL spectra.
Vargas, E.; Cifuentes, A.; Alvarado, S.; Cabrera, H.; Delgado, O.; Calderón, A.; Marín, E.
2018-02-01
Photothermal beam deflection is a well-established technique for measuring thermal diffusivity. In this technique, a pump laser beam generates temperature variations on the surface of the sample to be studied. These variations transfer heat to the surrounding medium, which may be air or any other fluid. The medium in turn experiences a change in the refractive index, which will be proportional to the temperature field on the sample surface when the distance to this surface is small. A probe laser beam will suffer a deflection due to the refractive index periodical changes, which is usually monitored by means of a quadrant photodetector or a similar device aided by lock-in amplification. A linear relationship that arises in this technique is that given by the phase lag of the thermal wave as a function of the distance to a punctual heat source when unidimensional heat diffusion can be guaranteed. This relationship is useful in the calculation of the sample's thermal diffusivity, which can be obtained straightforwardly by the so-called slope method, if the pump beam modulation frequency is well-known. The measurement procedure requires the experimenter to displace the probe beam at a given distance from the heat source, measure the phase lag at that offset, and repeat this for as many points as desired. This process can be quite lengthy in dependence of the number points. In this paper, we propose a detection scheme, which overcomes this limitation and simplifies the experimental setup using a digital camera that substitutes all detection hardware utilizing motion detection techniques and software digital signal lock-in post-processing. In this work, the method is demonstrated using thin metallic filaments as samples.
A New Regime of Nanoscale Thermal Transport: Collective Diffusion Increases Dissipation Efficiency
2015-04-21
different regimes of thermal transport. The laser-induced thermal expansion and subsequent cooling of the nanogratings is probed using coherent extreme UV ...technique compared with previously reported MFP spectros - copy techniques. First, our approach that combines nanoheaters with the phase sensitivity of
Development of method to chemical separation of gallium-67 by thermal diffusion technique
International Nuclear Information System (INIS)
Martins, Patricia de Andrade
2012-01-01
Radioisotopes of gallium have been studied and evaluated for medical applications since 1949. Over the past 50 years 67 Ga has been widely used in the diagnosis of various diseases, including acute and chronic inflammatory lesions, bacterial or sterile and several types of tumors. In Brazil 30% of clinics that provide services for Nuclear Medicine use 67 Ga citrate and the demand for 67 G a at IPEN-CNEN/SP is 37 GBq (1 Ci)/week. The 67 Ga presents physical half-life of 3.26 days (78 hours) and decays 100% by electron capture to stable 67 Zn. Its decay includes the emission of γ rays with energies of 93.3 keV (37%), 184.6 keV (20.4%), 300.2 keV (16.6%) and 888 keV (26%). In the past 67 Ga was produced by the reaction 68 Zn (p, 2n) 67 Ga at IPEN-CNEN/SP. After irradiation, the target was dissolved in concentrated HCl and the solution percolated through a cationic resin DOWEX 50W-X8, 200-400 mesh, conditioned with 10 mol L -1 HCl. Zinc, nickel and copper were eluted in 10 mol L -1 HCl and 67 Ga 3.5 mol L -1 HCl. The final product was obtained as 67 Ga citrate. This work presents a new, fast, direct and efficient method for the chemical separation of 67 G a by thermal diffusion (heating of the target) combined with concentrated acetic acid extraction. Purification was performed by ion exchange chromatography. Natural zinc electrodeposition was performed on nickel/copper plates as substrate and the zinc deposits were adherent to the substrate, slightly shiny and uniform. The targets were irradiated with 26 MeV protons and integrated current of 10 μA.h. After irradiation, the targets were heated at 300 deg C for 2 hours and placed in contact with concentrated acetic acid for 1 hour. The average yield of extraction of 67 Ga was (72 ± 10)%. This solution was evaporated and the residue was taken up in 0.5 mol L -1 NH 4 OH. The 67 G a was purified on cationic resin Dowex 50WX8 in NH 4 OH medium. The 67 Ga recovery was (98 ± 2)%. This solution was evaporated and taken up
Bisetti, Fabrizio
2012-12-01
Simulations of ion and electron transport in flames routinely adopt plasma fluid models, which require transport coefficients to compute the mass flux of charged species. In this work, the mobility and diffusion coefficient of thermal electrons in atmospheric premixed methane/air flames are calculated and analyzed. The electron mobility is highest in the unburnt region, decreasing more than threefold across the flame due to mixture composition effects related to the presence of water vapor. Mobility is found to be largely independent of equivalence ratio and approximately equal to 0.4m 2V -1s -1 in the reaction zone and burnt region. The methodology and results presented enable accurate and computationally inexpensive calculations of transport properties of thermal electrons for use in numerical simulations of charged species transport in flames. © 2012 The Combustion Institute.
Murthy, P.V.S.N.
2011-12-26
Thermo-diffusion effect on free convection heat and mass transfer from a vertical surface embedded in a liquid saturated thermally stratified non - Darcy porous medium has been analyzed using a local non-similar procedure. The wall temperature and concentration are constant and the medium is linearly stratified in the vertical direction with respect to the thermal conditions. The fluid flow, temperature and concentration fields are affected by the complex interactions among the diffusion ratio Le, buoyancy ratio N, thermo-diffusion parameter Sr and stratification parameter ?. Non-linear interactions of all these parameters on the convective transport has been analyzed and variation of heat and mass transfer coefficients with thermo-diffusion parameter in the thermally stratified non-Darcy porous media is presented through computer generated plots.
Murthy, P.V.S.N.; El-Amin, Mohamed
2011-01-01
Thermo-diffusion effect on free convection heat and mass transfer from a vertical surface embedded in a liquid saturated thermally stratified non - Darcy porous medium has been analyzed using a local non-similar procedure. The wall temperature and concentration are constant and the medium is linearly stratified in the vertical direction with respect to the thermal conditions. The fluid flow, temperature and concentration fields are affected by the complex interactions among the diffusion ratio Le, buoyancy ratio N, thermo-diffusion parameter Sr and stratification parameter ?. Non-linear interactions of all these parameters on the convective transport has been analyzed and variation of heat and mass transfer coefficients with thermo-diffusion parameter in the thermally stratified non-Darcy porous media is presented through computer generated plots.
Sasaki, Youhei; Takehiro, Shin-ichi; Ishiwatari, Masaki; Yamada, Michio
2018-03-01
Linear stability analysis of anelastic thermal convection in a rotating spherical shell with entropy diffusivities varying in the radial direction is performed. The structures of critical convection are obtained in the cases of four different radial distributions of entropy diffusivity; (1) κ is constant, (2) κT0 is constant, (3) κρ0 is constant, and (4) κρ0T0 is constant, where κ is the entropy diffusivity, T0 is the temperature of basic state, and ρ0 is the density of basic state, respectively. The ratio of inner and outer radii, the Prandtl number, the polytropic index, and the density ratio are 0.35, 1, 2, and 5, respectively. The value of the Ekman number is 10-3 or 10-5 . In the case of (1), where the setup is same as that of the anelastic dynamo benchmark (Jones et al., 2011), the structure of critical convection is concentrated near the outer boundary of the spherical shell around the equator. However, in the cases of (2), (3) and (4), the convection columns attach the inner boundary of the spherical shell. A rapidly rotating annulus model for anelastic systems is developed by assuming that convection structure is uniform in the axial direction taking into account the strong effect of Coriolis force. The annulus model well explains the characteristics of critical convection obtained numerically, such as critical azimuthal wavenumber, frequency, Rayleigh number, and the cylindrically radial location of convection columns. The radial distribution of entropy diffusivity, or more generally, diffusion properties in the entropy equation, is important for convection structure, because it determines the distribution of radial basic entropy gradient which is crucial for location of convection columns.
Electrical conductivity and charge diffusion in thermal QCD from the lattice
Energy Technology Data Exchange (ETDEWEB)
Aarts, Gert; Allton, Chris [Department of Physics, College of Science, Swansea University Swansea SA2 8PP (United Kingdom); Amato, Alessandro [Department of Physics, College of Science, Swansea University Swansea SA2 8PP (United Kingdom); Department of Physics and Helsinki Institute of Physics P.O. Box 64, FI-00014 University of Helsinki (Finland); Giudice, Pietro [Universität Münster, Institut für Theoretische Physik Wilhelm-Klemm-Str. 9, D-48149 Münster (Germany); Hands, Simon [Department of Physics, College of Science, Swansea University Swansea SA2 8PP (United Kingdom); Skullerud, Jon-Ivar [Department of Mathematical Physics, National University of Ireland Maynooth Maynooth, Co Kildare (Ireland)
2015-02-27
We present a lattice QCD calculation of the charge diffusion coefficient, the electrical conductivity and various susceptibilities of conserved charges, for a range of temperatures below and above the deconfinement crossover. The calculations include the contributions from up, down and strange quarks. We find that the diffusion coefficient is of the order of 1/(2πT) and has a dip around the crossover temperature. Our results are obtained with lattice simulations containing 2+1 dynamical flavours on anisotropic lattices. The Maximum Entropy Method is used to construct spectral functions from correlators of the conserved vector current.
Directory of Open Access Journals (Sweden)
Othuman Mydin M.A.
2014-01-01
Full Text Available With the quest for green construction and affordable housing systems for both rural and urban populations in Malaysia, various proposals focusing on cutting down on conventional building material costs have been put forward. One vanguard suggestion has been the sourcing, development and use of alternative, non-conventional local construction materials including the prospect of using some agricultural wastes as construction materials. This research describes experimental studies on the use of coconut coir fibre as an enhancer of foamed concrete with a focus on 2 parameters which are morphology properties and thermal properties of different percentages of coconut fibre (0%, 0.2% and 0.4%. In this study the addition of coconut fibre significantly improved all the properties investigated. The results of the tests showed that the thermal properties of foamed concrete improved with an increase in the proportion of coconut fibre. Findings from this research will also be used to address the knowledge gap on the subject of foamed concrete and will provide an improved understanding and raised awareness of the potential for using waste materials for domestic construction.
Excess Entropy and Diffusivity
Indian Academy of Sciences (India)
First page Back Continue Last page Graphics. Excess Entropy and Diffusivity. Excess entropy scaling of diffusivity (Rosenfeld,1977). Analogous relationships also exist for viscosity and thermal conductivity.
International Nuclear Information System (INIS)
Kitamoto, Asashi; Shimizu, Masami; Takashima, Yoichi
1977-01-01
Advanced transport relations involving three column constants, H sup(σ), K sub(c)sup(σ) and K sub(d)sup(σ), are developed to describe the separation performance of a thermal diffusion column with continuous draw-off. These constants were related to some integral functions of velocity profile, temperature distribution, density of gas mixture and characteristic values of transport coefficients. The separation of binary gas mixture by this technique was so effective that three reasonable factors had to be introduced into the column constants in the theory. They are a circulation constant of natural convection, a definition of characteristic mean temperature and a definition of mean composition over the column. The separation performance and the column constants also varied with the distortion of velocity profile due to continuous draw-off from the top or the bottom of column. However, its effect was not large, compared with the other factors mentioned above. The theory presented here makes possible to estimate the separation performance of hot-wire type thermal diffusion column with high accuracy. (auth.)
Huang, Melin; Huang, Bormin; Huang, Allen H.
2014-10-01
For weather forecasting and research, the Weather Research and Forecasting (WRF) model has been developed, consisting of several components such as dynamic solvers and physical simulation modules. WRF includes several Land- Surface Models (LSMs). The LSMs use atmospheric information, the radiative and precipitation forcing from the surface layer scheme, the radiation scheme, and the microphysics/convective scheme all together with the land's state variables and land-surface properties, to provide heat and moisture fluxes over land and sea-ice points. The WRF 5-layer thermal diffusion simulation is an LSM based on the MM5 5-layer soil temperature model with an energy budget that includes radiation, sensible, and latent heat flux. The WRF LSMs are very suitable for massively parallel computation as there are no interactions among horizontal grid points. The features, efficient parallelization and vectorization essentials, of Intel Many Integrated Core (MIC) architecture allow us to optimize this WRF 5-layer thermal diffusion scheme. In this work, we present the results of the computing performance on this scheme with Intel MIC architecture. Our results show that the MIC-based optimization improved the performance of the first version of multi-threaded code on Xeon Phi 5110P by a factor of 2.1x. Accordingly, the same CPU-based optimizations improved the performance on Intel Xeon E5- 2603 by a factor of 1.6x as compared to the first version of multi-threaded code.
International Nuclear Information System (INIS)
Hiroe, S.; Johnson, D.W.; Goldston, R.J.
1990-01-01
The local properties such as scale lengths of the electron density (L n e ), temperature (L T e ), and pressure (L p e ), and the electron thermal diffusivity χ e (r) (m 2 /s) for r/a > 0.3 have been studied for TFTR L-mode discharges under the assumption of χ e = χ i . The scale lengths and the electron thermal diffusivity in the interior 0.3 e can be expressed as (with correlation coefficient R = 0.61), χ e (r) = 1.44 x 10 18 (r/a) 1.0 T e (r) 0.1 q(r) 0.1 /n e 0.9 (r). In the exterior region (0.55 e can be described as (with R = 0.68), χ e (r) = 2.3 x 10 3 (r/a) 1.7 T e (r) 0.7 q(r) 0.8 /n e 0.2 (r). It is interesting to note the negative n e dependence of χ e in the interior and the positive T e dependence of χ e in the exterior
Energy Technology Data Exchange (ETDEWEB)
Zankel, K [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires
1967-07-01
Angstroem method has been reviewed for its application to measurements of thermal diffusivity and conductivity on short specimens. An apparatus and a technique have been developed for rapid and precise measurements of a large variety of materials, which might also contain heat sources. This technique allows measurements at both high and low temperatures. Stainless steel, nickel and uranium monocarbide specimens were tested and the results of the thermal diffusivity measurements between 50 deg. C and 700 deg. C are presented. (author) [French] L'application de la methode d'Angstroem pour la mesure de la diffusivite et de la conductivite thermique sur des echantillons courts est examinee. Un appareillage est decrit, qui permet non seulement des mesures sur une grande variete de materiaux, mais qui est aussi concu pour des mesures rapides, precises et ou des sources thermiques peuvent etre introduites au sein de l'echantillon. La methode s'adapte egalement aux mesures a basses et hautes temperatures. Des resultats de mesure sur un echantillon en acier inoxydable, en nickel et en carbure d'uranium pour des temperatures comprises entre 50 et 700 deg. C sont reportes. (auteur)
Directory of Open Access Journals (Sweden)
Chen Shao-Hsien
2018-01-01
Full Text Available Nickel base and titanium base materials have been widely applied to engines in aerospace industry, and these engines are essential components of airplanes. The machining characteristics of aerospace materials may cause machining cutters to be worn down in a short time and thus reduce the accuracy of processing. The plasma-assisted machining adopted in the research is a kind of the complex machining method. In the cases of nickel base and titanium base alloys, the method can heat workpieces in an extremely short duration to soften the materials for the ease of cutting so that the cutting force, cutter wear, and machining cost will all be reduced. The research adopted plasma heating to soften parts of the materials and aimed to explore the heating of nickel base alloy. The temperature variation of the materials was investigated and measured by adjusting the current and feed velocity. Moreover, Inconel-718 superalloy was adopted for the comparison with nickel base alloy for the observation of the influence and change brought by heat, and the method of exponential smoothing was adopted to conduct the prediction and analysis of thermal diffusion for understanding the influence and change brought by electric current on nickel base materials. Finally, given the current from 20 A to 80 A and feed velocity from 1,000 mm/min to 3,000 mm/min, the influence of thermal diffusion was investigated and the related model was built.
Physical and mathematical models for diffusion of thermal pollutants in water
International Nuclear Information System (INIS)
Pires, E.C.; Giorgetti, M.F.; Carajilescov, P.
1983-01-01
Mathematical models, such as the Fickian model and the model at PAILY and SAYRE, have been used in the analysis of thermal pollution. In the present work, experimental simulations of thermal dispersion were made using an artificial channel with injection of hat water and measurements of the temperature field were taken. The results were compared with the results given by the mentioned models, applying the image sources method. Due to the limitations of the model of PAILY and SAYRE, it was generalized for thermal sources posicioned at any place in the channel. The model of PAILY and SAYRE proved to be more satisfactory than the Fickian model and the image sources method was considered adequate. (Author) [pt
Air Motion and Thermal Environment in Pig Housing Facilities with Diffuse Inlet
DEFF Research Database (Denmark)
Jacobsen, Lis
A ventilation system with ambient air supply through diffuse ceiling used in pig production facilities is presented. The climatic conditions were examined both experimentally and numerically in an full scale experimental room and the inlet boundary conditions of the diffuse inlet were examined...... in ambient temperature and air exchange rate. The effect of housing equipment on environmental conditions has been examined both experimental and numerically and it was found that impervious housing equipment has a significant effect on the climatic conditions close to the wall in the occupational zone...... in a wind tunnel model. In the full scale experiments the focus has been on the correlation between variations in ambient climatic conditions and changes in environmental condition in the occupational zone. It was found that the environmental conditions in the occupational zone were independent on changes...
International Nuclear Information System (INIS)
Paul, O.P.K.
1978-01-01
An approach to simulate the flux vanishing boundary condition in solving the two group coupled neutron diffusion equations in three dimensions (x, y, z) employed to calculate the flux distribution and keff of the reactor is summarised. This is of particular interest when the flux vanishing boundary in x, y, z directions is not an integral multiple of the mesh spacings in these directions. The method assumes the flux to be negative, hypothetically at the mesh points lying outside the boundary and thus the finite difference formalism for Laplacian operator, taking into account six neighbours of a mesh point in a square mesh arrangement, is expressed in a general form so as to account for the boundary mesh points of the system. This approach has been incorporated in a three dimensional diffusion code similar to TAPPS23 and has been used for IRT-2000 reactor and the results are quite satisfactory. (author)
International Nuclear Information System (INIS)
Chambarel, A.; Pumborios, M.
1992-01-01
This paper reports that many engineering problems concern the determination of a steady state solution in the case with strong thermal gradients, and results obtained using the finite-element technique are sometimes inaccurate, particularly for nonlinear problems with unadapted meshes. Building on previous results in linear problems, we propose an autoadaptive technique for nonlinear cases that uses quasi-Newtonian iterations to reevaluate an interpolation error estimation. The authors perfected an automatic refinement technique to solve the nonlinear thermal problem of temperature calculus in a cast-iron cylinder head of a diesel engine
Field studies of submerged-diffuser thermal plumes with comparisons to predictive model results
International Nuclear Information System (INIS)
Frigo, A.A.; Paddock, R.A.; Ditmars, J.D.
1976-01-01
Thermal plumes from submerged discharges of cooling water from two power plants on Lake Michigan were studied. The system for the acquisition of water temperatures and ambient conditions permitted the three-dimensional structure of the plumes to be determined. The Zion Nuclear Power Station has two submerged discharge structures separated by only 94 m. Under conditions of flow from both structures, interaction between the two plumes resulted in larger thermal fields than would be predicted by the superposition of single non-interacting plumes. Maximum temperatures in the near-field region of the plume compared favorably with mathematical model predictions. A comparison of physical-model predictions for the plume at the D. C. Cook Nuclear Plant with prototype measurements indicated good agreement in the near-field region, but differences in the far-field occurred as similitude was not preserved there
Energy Technology Data Exchange (ETDEWEB)
Barsoum, Michel [Drexel Univ., Philadelphia, PA (United States); Bentzel, Grady [Drexel Univ., Philadelphia, PA (United States); Tallman, Darin J. [Drexel Univ., Philadelphia, PA (United States); Sindelar, Robert [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Garcia-Diaz, Brenda [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hoffman, Elizabeth [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2016-04-04
The demands of Gen IV nuclear power plants for long service life under neutron irradiation at high temperature are severe. Advanced materials that would withstand high temperatures (up to 1000+ ºC) to high doses in a neutron field would be ideal for reactor internal structures and would add to the long service life and reliability of the reactors. The objective of this work is to investigate the chemical compatibility of select MAX with potential materials that are important for nuclear energy, as well as to measure the thermal transport properties as a function of neutron irradiation. The chemical counterparts chosen for this work are: pyrolytic carbon, SiC, U, Pd, FLiBe, Pb-Bi and Na, the latter 3 in the molten state. The thermal conductivities and heat capacities of non-irradiated MAX phases will be measured.
Energy Technology Data Exchange (ETDEWEB)
Robinet, J.O. [Euro-Geomat-Consulting (France)]|[Institut National des Sciences Appliquees (INSA), 35 - Rennes (France); Plas, F. [Agence Nationale pour la Gestion des Dechets Radioactifs (ANDRA), 92 - Chatenay Malabry (France)
2005-07-01
The modelling of heat, mass transfer and the behaviour coupled thermo-hydro-mechanical in swelling clay require the development of appropriate constitutive laws as well as experimental data. This former approach, allows the quantitative validation of the theoretical models. In general modelling approaches consider dominant mechanisms, (i) Fourier law for diffusion of heat, (ii) generalized Darcy law for convection of liquid water, (iii) Flick law for diffusion of water vapour, and elastic-plastic models wit h hydric hardening and thermal damage/expansion for strain-stress behaviour. Transfer of dry air and water under thermal gradient and capillary (e.g. suction) gradient in unsaturated compacted swelling clays consider evaporation, migration and condensation. These transfers take into account the capillary effect. This effect is an evaporation of liquid water in the hot part for temperature higher than 100 C associated with a, diffusion of water vapor towards cold part then condensation, and convection of liquid water with gradient of suction in the opposite direction of the water vapour diffusion. High values of the diffusion coefficient of the vapour water are considered about 10{sup -7}m{sup 2}/s. Some thermal experiments related (i) low values of the water vapour diffusion coefficient in compacted swelling clays, 2004) and (ii) a significant drying associated with a water transfer even for temperature lower than 100 C. Other enhancement phenomena are used to explain these data and observations: the vaporization is a continuous process. At short term the mechanism of drying at short term is the thermal effect on the capillary pressure (e.g. surface tension depending of temperature); the thermal gradient is a driving force. When a temperature gradient is applied, diffusion occurs in order to reach equilibrium, e.g. to make the chemical potential (m) of each component uniform throughout. This mechanism is called thermal diffusion. This paper proposes a discussion
MODELING THE THERMAL DIFFUSE SOFT AND HARD X-RAY EMISSION IN M17
International Nuclear Information System (INIS)
Velázquez, P. F.; Rodríguez-González, A.; Esquivel, A.; Rosado, M.; Reyes-Iturbide, J.
2013-01-01
We present numerical models of very young wind driven superbubbles. The parameters chosen for the simulations correspond to the particular case of the M17 nebula, but are appropriate for any young superbubble in which the wind sources have not completely dispersed their parental cloud. From the simulations, we computed the diffuse emission in the soft ([0.5-1.5] keV) and hard ([1.5-5] keV) X-ray bands. The total luminosity in our simulations agrees with the observations of Hyodo et al., about two orders of magnitude below the prediction of the standard model of Weaver et al.. The difference with respect to the standard (adiabatic) model is the inclusion of radiative cooling, which is still important in such young bubbles. We show that for this type of object the diffuse hard X-ray luminosity is significant compared to that of soft X-rays, contributing as much as 10% of the total luminosity, in contrast with more evolved bubbles where the hard X-ray emission is indeed negligible, being at least four orders of magnitude lower than the soft X-ray emission.
Energy Technology Data Exchange (ETDEWEB)
Alvarez Rivas, J L
1963-07-01
The distribution of thermal neutron flux has been measured inside and outside copper rods of several diameters, immersed in water. It has been found that these distributions can be calculated by means of elemental diffusion theory if the value of the coefficient of diffusion is changed. this parameter is truly a diffusion coefficient, which now also depends on the diameter of the rod. Through a model an expression of this coefficient is introduced which takes account of the measurements of the author and of those reported in PUGC P/928 (1995), ANL-5872 (1959), DEGR 319 (D) (1961). This model could be extended also to plane geometry. (Author) 19 refs.
Miesner, F.; Lechleiter, A.; Müller, C.
2015-07-01
Continuous monitoring of oceanic bottom water temperatures is a complicated task, even in relatively easy-to-access basins like the North or Baltic seas. Here, a method to determine annual bottom water temperature variations from inverse modeling of instantaneous measurements of temperatures and sediment thermal properties is presented. This concept is similar to climate reconstructions over several thousand years from deep borehole data. However, in contrast, the presented method aims at reconstructing the recent temperature history of the last year from sediment thermal properties and temperatures from only a few meters depth. For solving the heat equation, a commonly used forward model is introduced and analyzed: knowing the bottom water temperature variations for the preceding years and the thermal properties of the sediments, the forward model determines the sediment temperature field. The bottom water temperature variation is modeled as an annual cosine defined by the mean temperature, the amplitude and a phase shift. As the forward model operator is non-linear but low-dimensional, common inversion schemes such as the Newton algorithm can be utilized. The algorithms are tested for artificial data with different noise levels and for two measured data sets: from the North Sea and from the Davis Strait. Both algorithms used show stable and satisfying results with reconstruction errors in the same magnitude as the initial data error. In particular, the artificial data sets are reproduced with accuracy within the bounds of the artificial noise level. Furthermore, the results for the measured North Sea data show small variances and resemble the bottom water temperature variations recorded from a nearby monitoring site with relative errors smaller than 1 % in all parameters.
Lee, Jinho; Park, Chibeom; Song, Intek; Koo, Jin Young; Yoon, Taekyung; Kim, Jun Sung; Choi, Hee Cheul
2018-05-16
In this paper, we report an efficient alkali metal doping system for organic single crystals. Our system employs an enhanced diffusion method for the introduction of alkali metal into organic single crystals by controlling the sample temperature to induce secondary thermal activation. Using this system, we achieved intercalation of potassium into picene single crystals with closed packed crystal structures. Using optical microscopy and Raman spectroscopy, we confirmed that the resulting samples were uniformly doped and became K 2 picene single crystal, while only parts of the crystal are doped and transformed into K 2 picene without secondary thermal activation. Moreover, using a customized electrical measurement system, the insulator-to-semiconductor transition of picene single crystals upon doping was confirmed by in situ electrical conductivity and ex situ temperature-dependent resistivity measurements. X-ray diffraction studies showed that potassium atoms were intercalated between molecular layers of picene, and doped samples did not show any KH- nor KOH-related peaks, indicating that picene molecules are retained without structural decomposition. During recent decades, tremendous efforts have been exerted to develop high-performance organic semiconductors and superconductors, whereas as little attention has been devoted to doped organic crystals. Our method will enable efficient alkali metal doping of organic crystals and will be a resource for future systematic studies on the electrical property changes of these organic crystals upon doping.
Directory of Open Access Journals (Sweden)
J. B. McQuaid
2009-06-01
Full Text Available A new Thermal Gradient ice nucleation Diffusion Chamber (TGDC capable of investigating ice nucleation efficiency of atmospherically important aerosols, termed Ice Nuclei (IN, has been designed, constructed and validated. The TGDC can produce a range of supersaturations with respect to ice (SS_{i} over the temperature range of −10 to −34°C for sufficiently long time needed to observe the ice nucleation by the particles. The novel aspect of this new TGDC is that the chamber is run in static mode with aerosol particles supported on a Teflon substrate, which can be raised and lowered in a controlled way through the SS_{i} profile within the chamber, and nucleation events are directly observed using digital photography. The TGDC consists of two ice coated plates to which a thermal gradient is applied to produce the range of SS_{i}. The design of the TGDC gives the ability to understand time-related ice nucleation event information and to perform experiments at different temperatures and SS_{i} conditions for different IN without changing the thermal gradient within the TGDC. The temperature and SS_{i} conditions of the experimental system are validated by observing (NH_{4}_{2}SO_{4} deliquescence and the results are in good agreement with the literature data. First results are presented of the onset ice nucleation for mineral dust sampled from the Saharan Desert, including images of nucleation and statistical distributions of onset ice nucleation SS_{i} as a function of temperature. This paper illustrates how useful this new TGDC is for process level studies of ice nucleation and more experimental investigations are needed to better quantify the role of ice formation in the atmosphere.
Sealing ability and thermal diffusivity of cavity lining materials: An in vitro study
Directory of Open Access Journals (Sweden)
Prabhakar A
2008-10-01
Full Text Available Aims: The purpose of this study was to evaluate and compare the sealing ability and the thermal insulating capability of four different cavity lining materials. Materials and Methods: Forty noncarious human mandibular second premolars that were extracted for orthodontic treatment were collected, cleaned, and stored in distilled water. These premolars were randomly divided into four groups of ten teeth each for treatment with the different cavity lining materials. Group I teeth were treated with cavity varnish, group II teeth with amorphous calcium phosphate (ACP, group III teeth with dentin bonding agent, and group IV teeth with resin-modified glass ionomer cement (RMGIC. Electrical resistance and the difference in the time-temperature curve of the external surface and the pulp side [A D -A P ] of each tooth following heat and cold application for 120 s were measured before and after cavity lining placement to determine the sealing ability and thermal insulating property, respectively. Data collected were subjected to statistical analysis. For paired data, paired t-test and Wilcoxon′s signed rank test were used. One-way ANOVA was used for comparisons between multiple groups and the Mann-Whitney U test for comparisons between pairs. Results: The mean difference in electrical resistance (in KΩ of different cavity lining materials were as follows: group I = +3.53, group II = −1.00, group III = +20.43, and group IV = +11.44. The mean differences in the area (A D -A P under the time-temperature curve following heat application were as follows: group I = 6.6 mm 2 , group II = 15.3 mm 2 , group III = 130.5 mm 2 , and group IV = 412.0 mm 2 . The mean differences in the area (A D -A P under the time-temperature curve following cold application were as follows: group I = 24.5 mm 2 , group II = 3.2 mm 2 , group III = 314.9 mm 2 , and group IV = 480.5 mm 2 . Conclusion: Dentin bonding agent and RMGIC provided effective sealing of the dentinal tubules
Effect of ballooning modes on thermal transport and magnetic field diffusion in the solar corona
International Nuclear Information System (INIS)
Strauss, H.R.
1989-01-01
Presently favored mechanisms of coronal heating: current sheet dissipation and Alfven wave resonant heating: deposit heat in thin layers. Classical thermal conduction cannot explain how heat is transported across the magnetic field. If heating occurs in thin layers, large pressure gradients can be created, which can give rise to ballooning modes. These instabilities are caused by the pressure gradient and the curvature of the magnetic field, and are stabilized by magnetic tension. The modes are broad band in wavelength and should produce turbulence. A mixing length expression for the turbulent heat transport shows that it is more than adequate to rapidly convect heat into much broader layers. Furthermore, the turbulent resistivity implies that heating occurs over most of the width of these broadened layers. The broadening also implies that much shorter time scales are required for heating. The β values in the corona suggest that 1--10 turbulent layers are formed in typical loop or arch structures. copyright American Geophysical Union 1989
Effect of grit blasting on the thermal cycling behavior of diffusion aluminide/YSZ TBCs
Energy Technology Data Exchange (ETDEWEB)
Xu, Zhenhua, E-mail: zhxuciac@163.com; Huang, Guanghong; He, Limin; Mu, Rende; Wang, Kai; Dai, Jianwei
2014-02-15
Highlights: • TBCs including of CVD NiAl bond coat and EB-PVD YSZ ceramic coating with and without grit blasting process. • Grain boundary ridges are the sites for spallation damage initiation in aluminide/YSZ TBCs. • Ridges are removed, and no cavity formation and this damage initiation mode are suppressed. • Damage initiation and progression occurs at the bond coat to TGO interface leading to a buckling failure behavior. -- Abstract: Thermal barrier coating system (TBCs) including of chemical vapor deposited NiAl bond coat and electron beam physical vapor deposited Y{sub 2}O{sub 3}–stabilized-ZrO{sub 2} (YSZ) ceramic coating with and without grit blasting process were investigated. The phase structures, surface and cross-sectional morphologies, cyclic oxidation behaviors of these coatings were studied in detail. Grain boundary ridges form on the surface of aluminide bond coat prior to the deposition of the ceramic coating by EB-PVD, which are shown to be the sites for spallation damage initiation in aluminide/YSZ TBCs. When these ridges are removed, there is no cavity formation and this damage initiation mode is suppressed. Damage initiation and progression occurs at the bond coat to TGO interface leading to a buckling failure behavior. A buckle failure once started may be arrested when it runs into a region of high bond coat to TGO interface toughness. Thus, complete failure requires further loss in toughness of the bond coat to TGO interface with additional cycling. From the result of thermal cycling, an averaged four folds lifetime improvement can be achieved with samples after grit blasting of bond coat surface as compared with those samples existence in ridges on the bond coats’ surface.
Fontenla, J. M.; Avrett, E. H.; Loeser, R.
1990-01-01
The energy balance in the lower transition region is analyzed by constructing theoretical models which satisfy the energy balance constraint. The energy balance is achieved by balancing the radiative losses and the energy flowing downward from the corona. This energy flow is mainly in two forms: conductive heat flow and hydrogen ionization energy flow due to ambipolar diffusion. Hydrostatic equilibrium is assumed, and, in a first calculation, local mechanical heating and Joule heating are ignored. In a second model, some mechanical heating compatible with chromospheric energy-balance calculations is introduced. The models are computed for a partial non-LTE approach in which radiation departs strongly from LTE but particles depart from Maxwellian distributions only to first order. The results, which apply to cases where the magnetic field is either absent, or uniform and vertical, are compared with the observed Lyman lines and continuum from the average quiet sun. The approximate agreement suggests that this type of model can roughly explain the observed intensities in a physically meaningful way, assuming only a few free parameters specified as chromospheric boundary conditions.
Directory of Open Access Journals (Sweden)
Lino Becerra
2009-11-01
Full Text Available Pain is difficult to assess due to the subjective nature of self-reporting. The lack of objective measures of pain has hampered the development of new treatments as well as the evaluation of current ones. Functional MRI studies of pain have begun to delineate potential brain response signatures that could be used as objective read-outs of pain. Using Diffuse Optical Tomography (DOT, we have shown in the past a distinct DOT signal over the somatosensory cortex to a noxious heat stimulus that could be distinguished from the signal elicited by innocuous mechanical stimuli. Here we further our findings by studying the response to thermal innocuous and noxious stimuli.Innocuous and noxious thermal stimuli were applied to the skin of the face of the first division (ophthalmic of the trigeminal nerve in healthy volunteers (N = 6. Stimuli temperatures were adjusted for each subject to evoke warm (equivalent to a 3/10 and painful hot (7/10 sensations in a verbal rating scale (0/10 = no/max pain. A set of 26 stimuli (5 sec each was applied for each temperature with inter-stimulus intervals varied between 8 and 15 sec using a Peltier thermode. A DOT system was used to capture cortical responses on both sides of the head over the primary somatosensory cortical region (S1. For the innocuous stimuli, group results indicated mainly activation on the contralateral side with a weak ipsilateral response. For the noxious stimuli, bilateral activation was observed with comparable amplitudes on both sides. Furthermore, noxious stimuli produced a temporal biphasic response while innocuous stimuli produced a monophasic response.These results are in accordance with fMRI and our other DOT studies of innocuous mechanical and noxious heat stimuli. The data indicate the differentiation of DOT cortical responses for pain vs. innocuous stimuli that may be useful in assessing objectively acute pain.
Li, Haijiang; Tian, Pengyi; Lu, Hongyu; Jia, Wenpeng; Du, Haodong; Zhang, Xiangjun; Li, Qunyang; Tian, Yu
2017-02-15
Sliding between two objects under very high load generally involves direct solid-solid contact at molecular/atomic level, the mechanism of which is far from clearly disclosed yet. Those microscopic solid-solid contacts could easily lead to local melting of rough surfaces. At extreme conditions, this local melting could propagate to the seizure and welding of the entire interface. Traditionally, the microscopic solid-solid contact is alleviated by various lubricants and additives based on their improved mechanical properties. In this work, we realized the state-of-the-art of extreme pressure lubrication by utilizing the high thermal diffusivity of liquid metal, 2 orders of magnitude higher than general organic lubricants. The extreme pressure lubrication property of gallium based liquid metal (GBLM) was compared with gear oil and poly-α-olefin in a four-ball test. The liquid metal lubricates very well at an extremely high load (10 kN, the maximum capability of a four-ball tester) at a rotation speed of 1800 rpm for a duration of several minutes, much better than traditional organic lubricants which typically break down within seconds at a load of a few kN. Our comparative experiments and analysis showed that this superextreme pressure lubrication capability of GBLM was attributed to the synergetic effect of the ultrafast heat dissipation of GBLM and the low friction coefficient of FeGa 3 tribo-film. The present work demonstrated a novel way of improving lubrication capability by enhancing the lubricant thermal properties, which might lead to mechanical systems with much higher reliability.
Sadeghifar, Hamidreza; Djilali, Ned; Bahrami, Majid
2015-01-01
This paper reports on measurements of thermal conductivity of a graphite bipolar plate (BPP) as a function of temperature and its thermal contact resistance (TCR) with treated and untreated gas diffusion layers (GDLs). The thermal conductivity of the BPP decreases with temperature and its thermal contact resistance with GDLs, which has been overlooked in the literature, is found to be dominant over a relatively wide range of compression. The effects of PTFE loading, micro porous layer (MPL), compression, and BPP out-of-flatness are also investigated experimentally. It is found that high PTFE loadings, MPL and even small BPP out-of-flatness increase the BPP-GDL thermal contact resistance dramatically. The paper also presents the effect of cyclic load on the total resistance of a GDL-BPP assembly, which sheds light on the behavior of these materials under operating conditions in polymer electrolyte membrane fuel cells.
Chiodini, Giovanni; Cardellini, Carlo; Lamberti, María Clara; Agusto, Mariano; Caselli, Alberto; Liccioli, Caterina; Tamburello, Giancarlo; Tassi, Franco; Vaselli, Orlando; Caliro, Stefano
2015-10-01
The north-western sector of Caviahue caldera (Argentina), close to the active volcanic system of Copahue, is characterized by the presence of several hydrothermal sites that host numerous fumarolic emissions, anomalous soil diffuse degassing of CO2 and hot soils. In March 2014, measurements of soil CO2 fluxes in 5 of these sites (namely, Las Máquinas, Las Maquinitas I, Las Maquinitas II, Anfiteatro, and Termas de Copahue) allowed an estimation that 165 t of deeply derived CO2 is daily released. The gas source is likely related to a relatively shallow geothermal reservoir containing a single vapor phase as also suggested by both the geochemical data from the 3 deep wells drilled in the 1980s and gas geoindicators applied to the fumarolic discharges. Gas equilibria within the H-C-O gas system indicate the presence of a large, probably unique, single phase vapor zone at 200-210 °C feeding the hydrothermal manifestations of Las Máquinas, Las Maquinitas I and II and Termas de Copahue. A natural thermal release of 107 MW was computed by using CO2 as a tracer of the original vapor phase. The magmatic signature of the incondensable fumarolic gases, the wide expanse of the hydrothermal areas and the remarkable high amount of gas and heat released by fluid expulsion seem to be compatible with an active magmatic intrusion beneath this portion of the Caviahue caldera.
Heat capacity and thermal diffusivity of ScD/sub x/ and ErD/sub x/
International Nuclear Information System (INIS)
Moss, M.
1979-04-01
The heat capacity, C/sub p/ (T = 298-1000 K), and the thermal diffusivity, α(T = 623-773 K), of ScD/sub x/ and ErD/sub x/ (x = 0-1.83) have been measured. C/sub p/ of ScD/sub x/ increases with x for x = 0-1.59 over the entire temperature range, but then declines for x = 1.83. ErD/sub x/ shows a monotonic increase of C/sub p/ with x, and exhibits a sharp positive anomaly at 910 K for x = 1.82. Both materials display an excess heat capacity which is attributed to disorder in the deuterium sublattice. A minimum in α is observed for ScD/sub x/ and ErD/sub x/ at mid-range values of x where disorder is greatest; α for all samples is fairly constant with T in this limited temperature range
Energy Technology Data Exchange (ETDEWEB)
Zhen, H.S.; Leung, C.W.; Cheung, C.S. [Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong (China)
2011-02-15
Two swirl-stabilized flames, a premixed flame (PMF-s) and an inverse diffusion flame (IDF-s), were investigated experimentally in order to obtain information on their thermal, emission and heat transfer characteristics. The two flames, having different global air/fuel mixing mechanisms, were compared under identical air and fuel flow rates. Results showed that the two flames have similar visual features such as flame shape, size and structure because the Reynolds number and the swirl number which are important parameters representative of the aerodynamic characteristics of a swirling jet flow, are almost the same for the two flames. The minor dissimilarity in flame color and flame length indicates that the IDF-s is more diffusional. Both the PMF-s and IDF-s are stabilized by the internal recirculation zone (IRZ) and the IDF-s is more stable. Flame temperature is uniformly distributed in the IRZ due to the strong mixing caused by flow recirculation. The highest flame temperature is achieved at the main reaction zone and it is higher for the PMF-s due to more rapid and localized heat release. For the IDF-s, the thermal NO mechanism dominates the NO{sub x} formation. For the PMF-s, both the thermal and prompt mechanisms tend to play important roles in the global NO{sub x} emission under rich conditions. The comparison of EINO{sub x} and EICO shows that the PMF-s has lower level of NO{sub x} emission under lean combustion and lower level of CO emission under all conditions. The reason is that the air/fuel premixing in the PMF-s significantly enhances the mixedness of the supplied air/fuel mixture. The analysis of the behaviors of the impinging PMF-s and IDF-s heat transfer reveals that because the PMF-s has more rapid and localized heat release at the main reaction zone, the peak heat flux is higher than that of the IDF-s and the IDF-s has more uniform heating effect. A comparison of the overall heat transfer rates shows that, due to more complete combustion, the PMF
International Nuclear Information System (INIS)
Zhen, H.S.; Leung, C.W.; Cheung, C.S.
2011-01-01
Two swirl-stabilized flames, a premixed flame (PMF-s) and an inverse diffusion flame (IDF-s), were investigated experimentally in order to obtain information on their thermal, emission and heat transfer characteristics. The two flames, having different global air/fuel mixing mechanisms, were compared under identical air and fuel flow rates. Results showed that the two flames have similar visual features such as flame shape, size and structure because the Reynolds number and the swirl number which are important parameters representative of the aerodynamic characteristics of a swirling jet flow, are almost the same for the two flames. The minor dissimilarity in flame color and flame length indicates that the IDF-s is more diffusional. Both the PMF-s and IDF-s are stabilized by the internal recirculation zone (IRZ) and the IDF-s is more stable. Flame temperature is uniformly distributed in the IRZ due to the strong mixing caused by flow recirculation. The highest flame temperature is achieved at the main reaction zone and it is higher for the PMF-s due to more rapid and localized heat release. For the IDF-s, the thermal NO mechanism dominates the NO x formation. For the PMF-s, both the thermal and prompt mechanisms tend to play important roles in the global NO x emission under rich conditions. The comparison of EINO x and EICO shows that the PMF-s has lower level of NO x emission under lean combustion and lower level of CO emission under all conditions. The reason is that the air/fuel premixing in the PMF-s significantly enhances the mixedness of the supplied air/fuel mixture. The analysis of the behaviors of the impinging PMF-s and IDF-s heat transfer reveals that because the PMF-s has more rapid and localized heat release at the main reaction zone, the peak heat flux is higher than that of the IDF-s and the IDF-s has more uniform heating effect. A comparison of the overall heat transfer rates shows that, due to more complete combustion, the PMF-s has higher overall
Energy Technology Data Exchange (ETDEWEB)
Letellier, F.; Lardé, R.; Le Breton, J.-M., E-mail: jean-marie.lebreton@univ-rouen.fr [Groupe de Physique des Matériaux, UMR 6634 CNRS/Université et INSA de Rouen, F-76801 Saint Etienne du Rouvray (France); Lechevallier, L. [Groupe de Physique des Matériaux, UMR 6634 CNRS/Université et INSA de Rouen, F-76801 Saint Etienne du Rouvray (France); Département de GEII, Université de Cergy-Pontoise, F-95031 Cergy-Pontoise (France); Akmaldinov, K. [SPINTEC, Univ. Grenoble-Alpes/CNRS/INAC-CEA, F-38000 Grenoble (France); CROCUS Technology, F-38025 Grenoble (France); Auffret, S.; Dieny, B.; Baltz, V., E-mail: vincent.baltz@cea.fr [SPINTEC, Univ. Grenoble-Alpes/CNRS/INAC-CEA, F-38000 Grenoble (France)
2014-11-28
Magnetic devices are often subject to thermal processing steps, such as field cooling to set exchange bias and annealing to crystallize amorphous magnetic electrodes. These processing steps may result in interdiffusion and the subsequent deterioration of magnetic properties. In this study, we investigated thermally-activated diffusion in Cu/Co/IrMn/Pt exchange biased polycrystalline thin-film structures using atom probe tomography. Images taken after annealing at 400 °C for 60 min revealed Mn diffusion into Co grains at the Co/IrMn interface and along Pt grain boundaries for the IrMn/Pt stack, i.e., a Harrison type C regime. Annealing at 500 °C showed further Mn diffusion into Co grains. At the IrMn/Pt interface, annealing at 500 °C led to a type B behavior since Mn diffusion was detected both along Pt grain boundaries and also into Pt grains. The deterioration of the films' exchange bias properties upon annealing was correlated to the observed diffusion. In particular, the topmost Pt capping layer thickness turned out to be crucial since a faster deterioration of the exchange bias properties for thicker caps was observed. This is consistent with the idea that Pt acts as a getter for Mn, drawing Mn out of the IrMn layer.
Friedson, A. James; Gonzales, Erica J.
2017-11-01
We explore the conditions under which ordinary and double-diffusive thermal convection may be inhibited by water condensation in the hydrogen atmospheres of the ice giants and examine the consequences. The saturation of vapor in the condensation layer induces a vertical gradient in the mean molecular weight that stabilizes the layer against convective instability when the abundance of vapor exceeds a critical value. In this instance, the layer temperature gradient can become superadiabatic and heat must be transported vertically by another mechanism. On Uranus and Neptune, water is inferred to be sufficiently abundant for inhibition of ordinary convection to take place in their respective condensation zones. We find that suppression of double-diffusive convection is sensitive to the ratio of the sedimentation time scale of the condensates to the buoyancy period in the condensation layer. In the limit of rapid sedimentation, the layer is found to be stable to diffusive convection. In the opposite limit, diffusive convection can occur. However, if the fluid remains saturated, then layered convection is generally suppressed and the motion is restricted in form to weak, homogeneous, oscillatory turbulence. This form of diffusive convection is a relatively inefficient mechanism for transporting heat, characterized by low Nusselt numbers. When both ordinary and layered convection are suppressed, the condensation zone acts effectively as a thermal insulator, with the heat flux transported across it only slightly greater than the small value that can be supported by radiative diffusion. This may allow a large superadiabatic temperature gradient to develop in the layer over time. Once the layer has formed, however, it is vulnerable to persistent erosion by entrainment of fluid into the overlying convective envelope of the cooling planet, potentially leading to its collapse. We discuss the implications of our results for thermal evolution models of the ice giants, for
International Nuclear Information System (INIS)
Komori, S.
1996-01-01
in clarifying environmental flow phenomena. This report summarizes research on two turbulence structure and diffusion topics; turbulence structure and the gas transfer mechanism across the air-sea (air-water) interface and the heat and momentum transfer mechanism in thermally stratified flows. The first study shows the relationship between the carbon dioxide (CO 2 ) transfer mechanism across a sheared air-water interface and the turbulence structure near the interface. The results revealed that the conventional proportional relationship between CO 2 transfer velocity across the air-sea interface and mean wind speed over the sea surface is incorrect. The second study numerically clarified the significant effects of molecular diffusivity (the Prandtl number) of active heat on heat transfer in stable thermally-stratified Hows. The results obtained from the two studies are described in the next two chapters. Since the results are mainly quoted from a series of previously published and in press works by Komori et al.'s research group (see references), this report might be considered as a summary of those works
International Nuclear Information System (INIS)
Uematsu, Masashi; Yanagawa, Fumihiko
1988-01-01
The Si diffusion in Si-implanted GaAs/Al 0.5 Ga 0.5 As superlattices intermixed in the disrodering process induced by rapid thermal annealing (RTA), is investigated by means of secondary ion mass spectroscopy (SIMS). The SIMS profiles indicate that no fast Si diffusion occurs during the disordering, and the disordering occurs when the Si concentration exceeds 1 x 10 19 cm -3 , which is about three times larger than the threshold value for the disordering by furnace annealing (FA). The number of Si atoms which are allowed to pass through the heterointerface is considered to be essential for disordering. (author)
Raj, S. V.
2017-01-01
This two-part paper reports the thermophysical properties of several cold and vacuum plasma sprayed monolithic Cu and Ni-based alloy coatings. Part I presents the electrical and thermal conductivity, thermal diffusivity, and total hemispherical emissivity data while Part II reports the specific heat capacity data for these coatings. Metallic copper alloys, stoichiometric NiAl and NiCrAlY coatings were fabricated by either the cold sprayed or the vacuum plasma spray deposition processes for thermal property measurements between 77 and 1223 K. The temperature dependencies of the thermal conductivities, thermal diffusivities, electrical conductivities and total hemispherical emissivities of these cold and vacuum sprayed monolithic coatings are reported in this paper. The electrical and thermal conductivity data correlate reasonably well for Cu-8%Cr-1%Al, Cu-23%Cr-5%Al and NiAl in accordance with the Wiedemann-Franz (WF) law although a better fit is obtained using the Smith-Palmer relationship. The Lorentz numbers determined from the WF law are close to the theoretical value.
Directory of Open Access Journals (Sweden)
Settu Balachandar
2016-01-01
Full Text Available A novel mechanism is proposed, involving a novel interaction between solid-sample supporting unsteady heat flow with its ambient-humidity; invokes phase transformation of water-vapour molecule and synthesize a ‘moving optical-mark’ at sample-ambient-interface. Under tailored condition, optical-mark exhibits a characteristic macro-scale translatory motion governed by thermal diffusivity of solid. For various step-temperature inputs via cooling, position-dependent velocities of moving optical-mark are measured at a fixed distance. A new approach is proposed. ‘Product of velocity of optical-mark and distance’ versus ‘non-dimensional velocity’ is plotted. The slope reveals thermal diffusivity of solid at ambient-temperature; preliminary results obtained for Quartz-glass is closely matching with literature.
Energy Technology Data Exchange (ETDEWEB)
Pawlak, M., E-mail: mpawlak@fizyka.umk.pl [Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5/7, Toruń (Poland); Maliński, M. [Department of Electronics and Computer Science, Koszalin University of Technology, 2 Śniadeckich St., Koszalin 75-453 (Poland)
2015-01-10
Highlights: • The new method of determination of the effective infrared absorption coefficient is presented. • The method can be used for transparent samples for the excitation radiation. • The effect of aluminum foil on the PTR signal in a transmission configuration is discussed. - Abstract: In this paper we propose a new procedure of simultaneous estimation of the effective infrared optical absorption coefficient and the thermal diffusivity of solid state samples using the photothermal infrared radiometry method in the transmission configuration. The proposed procedure relies on the analysis of the frequency dependent signal obtained from the samples covered with thin aluminum foil. This method can be applied for both optically opaque and transparent samples. The proposed method is illustrated with the results of the thermal diffusivity and the effective IR absorption coefficient obtained for several Cd{sub 1−x}Mg{sub x}Se crystals.
International Nuclear Information System (INIS)
Korpisalo, A.; Suppala, I.; Kukkonen, I.; Koskinen, T.
2013-11-01
The thermal drillhole device (76 mm drillholes) used in this study for determining thermal properties of rocks in situ was developed and constructed under TERO projects in Geological Survey of Finland with Posiva in early 2000's. After the renovation of the device in 2010, the new TERO76 device has now been taken into the productive use. In addition to the numerical inversion technique a rapid interpretation tool makes it possible to calculate the first estimates of thermal properties of the measurements already in the field. The thermal properties of the measurements are estimated by using both a numerical optimization and a simple solution of infinite line model. Because of the unique measurement geometry only the thermal conductivities can directly be estimated accurately (5 %) using the late times of heating periods. The methods can't directly give the thermal diffusivities or heat capacities at a necessary accuracy. However, thermal diffusivities can be estimated by using the specific heat capacities and densities of the known rock types or the laboratory results on diffusivity-conductivity relationship of different Olkiluoto rock types. The latter technique is applied in this study. Thermal properties were measured in four shallow ONKALO drillholes (ONK-PP379, ONK-PP380, ONK-PP381, ONK-PP382) in the Demonstration tunnel 2 (ONK-TDT-4399-30) at +420 m level and in deep drillholes OL-KR46 and OL-KR56 from the surface. In the drillholes in tunnel, the average numerical values fall within 3.31 and 4.19 Wm - 1 K- 1 for the conductivities and 1.75-2.26 x 10 -6 m 2 s -1 for the diffusivities. The corresponding analytical values are within 3.19-3.99 Wm -1 K -1 and 1.68-2.15 x 10 -6 m 2 s -1 . In drillholes OL-KR46 and OL-KR56, the average numerical values fall within 3.42-4.06 and 3.30-3.77 Wm -1 K -1 for the conductivities and 1.81-2.18 and 1.75-2.02 x 10 -6 m 2 s -1 for the diffusivities. The corresponding average analytical conductivities fall within 3.22-3.81 and
Czech Academy of Sciences Publication Activity Database
Bakanov, S. P.; Smolík, Jiří; Zaripov, S. K.; Ždímal, Vladimír
2001-01-01
Roč. 32, č. 3 (2001), s. 341-350 ISSN 0021-8502 R&D Projects: GA ČR GA104/97/1198 Grant - others:RFBR(RU) 99-01-00-169 Institutional research plan: CEZ:AV0Z4072921 Keywords : thermal diffusion cloud chamber * droplet growth * continuum regime Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.605, year: 2001
International Nuclear Information System (INIS)
Orlova, N.S.
1978-01-01
Intensity of diffusion scattering of X-rays from the plane of a monocrystal of indium arsenide has been measured on the monochromatized CuKsub(α)-radiation. The samples are made of Cl indium arsenide monocrystal of the n-type with the 1x10 18 cm -3 concentration of carriers in the form of a plate with the polished parallel cut-off with the +-5' accuracy. The investigations have been carried out on the URS-5 IM X-ray diffractometer at room temperature in vacuum. Intensities of thermal diffusion scattering of the second order have been calculated by the two-atomic chain model with different mass and four interaction paramaters. Based upon the analysis of intensity of single-phonon diffusion scattering the curves of frequencies of atomic oscillations along the direction [100] have been determined. The values of frequencies obtained experimentally on the thermal diffusion scattering of X-rays are in a satisfactory agreement with the calculated data. The frequencies obtained are compared with the results of calculation and the analysis of multiphonon spectra of IR-absorption made elsewhere
International Nuclear Information System (INIS)
Zhai, W.; Zhou, K.; Hu, L.; Wei, B.
2016-01-01
Highlights: • The increasing Sn content reduces the liquidus temperature. • High Sn content results in lower enthalpy of fusion by polynomial functions. • The thermal diffusivity drops from the solid toward the semi-solid state. • Undercoolability of alloys with primary Cu_2Sb phase is stronger than others. - Abstract: The liquidus and solidus temperatures, enthalpy of fusion, and the temperature dependence of thermal diffusivity for ternary Cu_6_0_−_xSn_xSb_4_0 alloys were systematically measured by DSC and laser flash methods. It is found that both the liquidus temperature and the enthalpy of fusion decrease with the rise of Sn content, and their relationships with alloy composition were established by polynomial functions. The thermal diffusivity usually drops from the solid toward the semi-solid state. The undercoolability of those liquid Cu_6_0_−_xSn_xSb_4_0 alloys with primary Cu_2Sb solid phase is stronger than the others with primary β(SnSb) intermetallic compound, and the increase of cooling rate facilitates further undercooling. Microstructural observation indicates that both of the primary Cu_2Sb and β(SnSb) intermetallic compounds in ternary Cu_6_0_−_xSn_xSb_4_0 alloys grow in faceted mode, and develop into coarse flakes and polygonal blocks.
Ortiz Montalvo, D. L.; Kirchstetter, T. W.; Soto-García, L. L.; Mayol-Bracero, O. L.
2006-12-01
Combustion generated particles are a concern to both climate and public health due to their ability to scatter and absorb solar radiation and alter cloud properties, and because they are small enough to be inhaled and deposit in the lungs where they may cause respiratory and other health problems. Specific concern is focused on particles that originate from the combustion of diesel fuel. Diesels particles are composed mainly of carbonaceous material, especially in locations where diesel fuel sulfur is low. These particles are black due to the strongly light absorbing nature of the refractory carbon components, appropriately called black carbon (BC). This research project focuses on the uncertainty in the measurement of BC mass concentration, which is typically determined by analysis of particles collected on a filter using a thermal-optical analysis (TOA) method. Many studies have been conducted to examine the accuracy of the commonly used variations of the TOA method, which vary in their sample heating protocol, carrier gas, and optical measurement. These studies show that BC measurements are inaccurate due to the presence of organic carbon (OC) in the aerosols. OC may co-evolve with BC or char to form BC during analysis, both of which make it difficult to distinguish between the OC and BC in the sample. The goal of this study is to develop the capability of producing standard samples of known amounts of BC, either alone or mixed with other aerosol constituents, and then evaluate which TOA methods accurately determine the BC amount. An inverted diffusion flame of methane and air was used to produce particle samples containing only BC as well as samples of BC mixed with humic acid (HA). Our study found that HA is light absorbing and catalyzes the combustion of BC. It is expected that both of these attributes will challenge the ability of TOA methods in distinguishing between OC and BC, such as the simple two step TOA method which relies solely on temperature to
Shen, Xiang; Dai, Bin; Xing, Yingbin; Yang, Luyun; Li, Haiqing; Li, Jinyan; Peng, Jingang
2018-05-08
We demonstrated a kind of long-period fiber grating (LPFG), which is manufactured with a thermal diffusion treatment. The LPFG was inscribed on an ultrahigh-numerical-aperture (UHNA) fiber, highly doped with Ge and P, which was able to easily diffuse at high temperatures within a few seconds. We analyzed how the elements diffused at a high temperature over 1300 °C in the UHNA fiber. Then we developed a periodically heated technology with a CO₂ laser, which was able to cause the diffusion of the elements to constitute the modulations of an LPFG. With this technology, there is little damage to the outer structure of the fiber, which is different from the traditional LPFG, as it is periodically tapered. Since the LPFG itself was manufactured under high temperature, it can withstand higher temperatures than traditional LPFGs. Furthermore, the LPFG presents a higher sensitivity to high temperature due to the large amount of Ge doping, which is approximately 100 pm/°C. In addition, the LPFG shows insensitivity to the changing of the environment’s refractive index and strain.
Energy Technology Data Exchange (ETDEWEB)
Masuda, Jun; Fukase, Yasushi [Toshiba Machine Co., Ltd, Ooka 2068-3, Numazu-Shi, Shizuoka-Ken, 410-8510 (Japan); Yan Jiwang; Zhou Tianfeng; Kuriyagawa, Tsunemoto, E-mail: yanjw@pm.mech.tohoku.ac.jp [Department of Mechanical Systems and Design, Graduate School of Engineering, Tohoku University, Aoba 6-6-01, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)
2011-06-01
In a glass moulding press (GMP) for refractive/diffractive hybrid lenses, to improve the service life of nickel-phosphorus (Ni-P) plated moulds, it is necessary to control the diffusion of constituent elements from the mould into the release agent coating. In this study, diffusion phenomena of constituents of Ni-P plating are investigated for two types of release agent coatings, iridium-platinum (Ir-Pt) and iridium-rhenium (Ir-Re), by cross-sectional observation, compositional analysis and stress measurements. The results show that Ni atoms in the plating layer flow from regions of compressive stress to regions of tensile stress. In the case of the Ir-Pt coated mould, the diffusion of Ni is promoted from the grain boundaries between the Ni and Ni{sub 3}P phases in the plating towards the surface of the Ir-Pt coating. However, in the Ir-Re coated mould, the diffusion of Ni is suppressed because the diffusion coefficient of Ni in the Ir-Re alloy is smaller than that in the Ir-Pt alloy, although the stress state is similar in both cases. By controlling the diffusion of Ni atoms, the use of Ir-Re alloy as a release agent coating for Ni-P plated moulds is expected to lead to a high degree of durability.
International Nuclear Information System (INIS)
Boufraqech, A.
1991-01-01
Two methods for determining the diffusion parameters of thermal neutrons for non-moderator and non-multiplicator media have been developped: The first one, which is a pulsed method, is based on thermal neutrons relaxation coefficients measurement in a moderator, with and without the medium of interest that plays the role of reflector. For the experimental results interpretation using the diffusion theory, a corrective factor which takes into account the neutron cooling by diffusion has been introduced. Its dependence on the empirically obtained relaxation coefficients is in a good agreement with the calculations made in P3L2 approximation. The difference between linear extrapolation lengths of the moderator and the reflector has been taken into account, by developping the scalar fluxes in Bessel function series which automatically satisfy the boundary conditions at the extra-polated surfaces of the two media. The obtained results for Iron are in a good agreement with those in the literature. The second method is time independent, based on the 'flux albedo' measurements interpretation (Concept introduced by Amaldi and Fermi) by P3 approximation in the one group trans-port theory. The independent sources are introduced in the Marshak boundary conditions. An angular albedo matrix has been used to deal with multiple reflections and to take into account the distortion of the current vector when entring a medium, after being reflected by this latter. The results obtained by this method are slightly different from those given in the literature. The analysis of the possible sources causing this discrepancy, particulary the radial distribution of flux in cylindrical geometry and the flux depression at medium-black body interface, has shown that the origin of this discrepancy is the neutron heating by diffusion. 47 figs., 20 tabs., 39 refs. (author)
International Nuclear Information System (INIS)
Solovetskii, Yu.I.; Miroshinichenko, I.I.; Lunin, V.V.
1993-01-01
Radiation-thermal damage of the surface and the active metal phases of hydrodesulfurization Ni-Mo/Al 2 O 3 catalysts by a fast electron beam of up to 2.0 MeV energy was studied. UV-Vis diffuse reflectance spectra of the industrial and model coked systems after radiation-thermal treatment were measured. 14 refs., 2 figs
Ida, K; Funaba, H; Kado, S; Narihara, K; Tanaka, K; Takeiri, Y; Nakamura, Y; Ohyabu, N; Yamazaki, K; Yokoyama, M; Murakami, S; Ashikawa, N; deVries, P C; Emoto, M; Goto, M; Idei, H; Ikeda, K; Inagaki, S; Inoue, N; Isobe, M; Itoh, K; Kaneko, O; Kawahata, K; Khlopenkov, K; Komori, A; Kubo, S; Kumazawa, R; Liang, Y; Masuzaki, S; Minami, T; Miyazawa, J; Morisaki, T; Morita, S; Mutoh, T; Muto, S; Nagayama, Y; Nakanishi, H; Nishimura, K; Noda, N; Notake, T; Kobuchi, T; Ohdachi, S; Ohkubo, K; Oka, Y; Osakabe, M; Ozaki, T; Pavlichenko, R O; Peterson, B J; Sagara, A; Saito, K; Sakakibara, S; Sakamoto, R; Sanuki, H; Sasao, H; Sasao, M; Sato, K; Sato, M; Seki, T; Shimozuma, T; Shoji, M; Suzuki, H; Sudo, S; Tamura, N; Toi, K; Tokuzawa, T; Torii, Y; Tsumori, K; Yamamoto, T; Yamada, H; Yamada, I; Yamaguchi, S; Yamamoto, S; Yoshimura, Y; Watanabe, K Y; Watari, T; Hamada, Y; Motojima, O; Fujiwara, M
2001-06-04
Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduction of ion thermal diffusivity was observed after the mode transition from ion root to electron root as predicted by neoclassical theory when the neoclassical ion loss is more dominant than the anomalous ion loss.
DEFF Research Database (Denmark)
Tousek, J.; Touskova, J.; Ludvík, J.
2016-01-01
samples were prepared from 2 different precursors by thermal or chemical treatment at room temperature. Cyclic voltammetry and work function measurements were used for estimating the concentration of holes. The measured data were evaluated assuming the validity of band theory based on the tight......-binding model. Published data on the valence bandwidth were used for calculating the value of the overlap integral which is related to the hole effective mass. Energy band diagrams were constructed for all 3 materials. Finally, the exciton diffusion length, which is a critical parameter for the application....... It is stated that a native polythiophene prepared by treatment with acids is a prospective material for solar cells and shows a similar quality as that produced by a thermal process. © 2015 Elsevier Ltd. All rights reserved....
Energy Technology Data Exchange (ETDEWEB)
Silva, Agmar J.J.; Costa, Marysilvia F., E-mail: agmar@metalmat.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil)
2015-07-01
This work discuss firstly the effect of the ethanol fuel absorption by PVDF at 60°C through mass variation tests. A Fickian character was observed for the ethanol absorption kinetics of the aged PVDF at 60°C. In the second step, the dynamic mechanical thermal properties (E’, E’, E” and tan δ) of the PVDF were evaluated through dynamic mechanical thermal analysis (DMTA). The chemical structure of the materials was analyzed by X-ray diffraction analysis (XRD), and significant changes in the degree of crystallinity were verified after the aging. However, DMTA results showed a reduction in the storage modulus (E') of the aged PVDF, which was associated to diffusion of ethanol and swelling of the PVDF, which generated a prevailing plasticizing effect and led to reduction of its structural stiffness. (author)
Sadeghi, E.; Djilali, N.; Bahrami, M.
Heat transfer through the gas diffusion layer (GDL) is a key process in the design and operation of a proton exchange membrane (PEM) fuel cell. The analysis of this process requires determination of the effective thermal conductivity. This transport property differs significantly in the through-plane and in-plane directions due to the anisotropic micro-structure of the GDL. A novel test bed that allows separation of in-plane effective thermal conductivity and thermal contact resistance in GDLs is described in this paper. Measurements are performed using Toray carbon paper TGP-H-120 samples with varying polytetrafluoroethylene (PTFE) content at a mean temperature of 65-70 °C. The measurements are complemented by a compact analytical model that achieves good agreement with experimental data. The in-plane effective thermal conductivity is found to remain approximately constant, k ≈ 17.5 W m -1 K -1, over a wide range of PTFE content, and its value is about 12 times higher than that for through-plane conductivity.
Energy Technology Data Exchange (ETDEWEB)
Lemarechal-Dupuis, A [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires
1968-04-01
Thermal diffusion constants of the mixtures H{sub 2}-HD and H{sub 2}-HT, where HD and HT were at trace concentrations, have been measured between 90 deg. K and 450 deg. K for H{sub 2}-HD and between 190 deg. K and 450 deg. K for H{sub 2}-HT, by using the elementary effect. Furthermore, the ratio of these constants has been measured by using a thermo-gravitational column of Clusius and Dickel, at temperatures of the hot wire between 455 deg. K and 1200 deg. K, the cold wall being at room temperature. Comparison with the predictions of existing theories shows that the Chapman-Enskog theory cannot account for the thermal diffusion of mixtures containing asymmetric molecules; the possible reasons for this disagreement are discussed. Our set of measurements, combined with the results of other authors, yields precise values at well defined conditions of temperature and concentration, useful for the determination of the coefficients of the semi-empirical expansion of Waldmann and Klemm. Furthermore some aspects of the column theory according to Furry and Jones have been tested. (author) [French] Les constantes de diffusion thermique des melanges H{sub 2}-HD et H{sub 2}-HT ou HD et HT figuraient, a l'etat de traces, ont ete mesurees a l'aide de l'effet elementaire entre 90 deg. K et 450 deg. K pour le melange H{sub 2}-HD,et entre 190 deg. K et 450 deg. K pour le melange H{sub 2}-HT. D'autre part, le rapport de ces constantes a ete mesure a l'aide d'une colonne de Clusius et Dickel pour des temperatures du fil chaud variant entre 455 deg. K et 1200 deg. K, la temperature de la paroi froide etant la temperature ambiante. La comparaison avec les predictions des theories existantes montre que la theorie de Chapman- Enskog ne peut rendre compte de la constante de diffusion thermique de melanges de molecules asymetriques; les raisons de ce desaccord sont discutees. L'ensemble de ces mesures, combine aux resultats d'autres auteurs, permet d'obtenir des valeurs precises dans des
DEFF Research Database (Denmark)
Zhang, Chen; Heiselberg, Per Kvols; Pomianowski, Michal Zbigniew
2015-01-01
the opposite effect on energy performance when TABS is activated in heating or cooling mode. Finally, the air temperature distribution in the plenum and the surface temperature distribution of the diffuse ceiling point out that the air does not perfectly mix in the plenum, the air is not evenly distributed...
Energy Technology Data Exchange (ETDEWEB)
Zankel, K. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires
1967-07-01
Angstroem method has been reviewed for its application to measurements of thermal diffusivity and conductivity on short specimens. An apparatus and a technique have been developed for rapid and precise measurements of a large variety of materials, which might also contain heat sources. This technique allows measurements at both high and low temperatures. Stainless steel, nickel and uranium monocarbide specimens were tested and the results of the thermal diffusivity measurements between 50 deg. C and 700 deg. C are presented. (author) [French] L'application de la methode d'Angstroem pour la mesure de la diffusivite et de la conductivite thermique sur des echantillons courts est examinee. Un appareillage est decrit, qui permet non seulement des mesures sur une grande variete de materiaux, mais qui est aussi concu pour des mesures rapides, precises et ou des sources thermiques peuvent etre introduites au sein de l'echantillon. La methode s'adapte egalement aux mesures a basses et hautes temperatures. Des resultats de mesure sur un echantillon en acier inoxydable, en nickel et en carbure d'uranium pour des temperatures comprises entre 50 et 700 deg. C sont reportes. (auteur)
International Nuclear Information System (INIS)
Groebner, R.J.
1986-04-01
The study of ion transport in neutral beam-heated discharges in tokamaks is necessary to determine if neoclassical theory can reliably be used to predict the performance of future machines. Previous studies of ion tranport have generally been difficult due to the lack of information regarding the ion temperature profile. The standard procedure used to study ion transport has been to model the T/sub i/ profile with the assumption that the ion thermal diffusivity profile chi/sub i/(r) was equal to a multiplier times chi/sub i//sup neo/(r), the ion thermal diffusivity calculated from neoclassical theory. The multiplier was varied until the calculated T/sub i/ profile agreed with the available ion temperature data, usually T/sub i/(0) or the measured neutron rate. Values of the multiplier in the range of 1 to 10 have generally been obtained with few estimates of the uncertainties in these values. Furthermore, there have been few, if any, attempts to calculate chi/sub i/ by modeling the ion temperature profiles in other ways. As a result, the issue as to whether or not the ion transport in tokamaks is in agreement with neoclassical theory has not been definitively answered
Energy Technology Data Exchange (ETDEWEB)
Drehmann, Rico; Rupprecht, Christian; Wielage, Bernhard; Lampke, Thomas [Technische Univ. Chemnitz (Germany). Inst. fuer Werkstoffwissenschaft und Werkstofftechnik (IWW); Gilbert, Maria; Uhlig, Volker; Trimis, Dimosthenis [Technische Univ. Bergakademie Freiberg (Germany). Inst. fuer Waermetechnik und Thermodynamik (IWTT); Heuer, Volker [ALD Vacuum Technologies GmbH, Hanau (Germany)
2013-03-15
In heat treating processes as well as in high temperature brazing processes, charge carriers enable the positioning and transport of work pieces. Recently, charge carriers consisting of graphite or carbon fibre reinforced carbon (CFC) are used. The main disadvantage of charge carriers based on CFC is the undesirable carburization of the overlying components due to diffusion processes. Under this aspect, thermally sprayed coatings are applied on CFC and tested with respect to their suitability as a high-temperature diffusion barrier. The ceramic powders aluminium oxide, aluminium oxide/chromium oxide, aluminium oxide/titanium oxide and zirconium oxide/yttrium oxide are used as a coating material which is processed by means of the powder flame spraying as well as atmospheric plasma spraying. Molybdenum and silicon carbide are used as an adhesive layer. The coating materials aluminium oxide and aluminium oxide/chromium oxide on siliconized CFC presented excellent results. This supplies a large potential of application for thermally sprayed ceramic coatings on carbon-based lightweight materials.
Mihaila, Bogdan; Stan, Marius; Crapps, Justin; Yun, Di
2013-02-01
We study the coupled thermal transport, oxygen diffusion, and thermal expansion in a generic nuclear fuel rod consisting of a (U) fuel pellet separated by a helium gap from zircaloy cladding. Steady-state and time-dependent finite-element simulations with a variety of initial- and boundary-value conditions are used to study the effect of the Pu content, y, and deviation from stoichiometry, x, on the temperature and deformation profiles in this fuel element. We find that the equilibrium radial temperature and deformation profiles are most sensitive to x at small values of y. For larger values of y, the effects of oxygen and Pu content are equally important. Following a change in the heat-generation rate, the centerline temperature, the radial deformation of the fuel pellet, and the centerline deviation from stoichiometry track each other closely in (U,Pu)O, as the characteristic time scales of the heat transport and oxygen diffusion are similar. This result is different from the situation observed in the case of UO fuels.
Salaün, F.; Bedek, G.; Devaux, E.; Dupont, D.; Deranton, D.
2009-08-01
Polyurethane microparticles containing xylitol as a sweat sensor system were prepared by interfacial polymerization. The structural and thermal properties of the resultant microparticles were studied. The surface morphology and chemical structure of microparticles were investigated using an optical microscope (OM) and a Fourier-transform infrared spectroscope (FTIR), respectively. The thermal properties of samples were investigated by thermogravimetric analysis (TGA) and by differential scanning calorimetry (DSC). Thus, two types of microparticles were synthesized by varying the percentage of monomers introduced. The obtained morphology is directly related to the synthesis conditions. DSC analysis indicated that the mass content of crystalline xylitol was up to 63.8 %, which resulted in a high enthalpy of dilution of 127.7 J · g-1. Furthermore, the water release rate monitored by TGA analysis was found to be faster from the microparticles than from raw xylitol. Thus, the microparticles could be applied for thermal energy storage and moisture sensor enhancement.
Energy Technology Data Exchange (ETDEWEB)
Pereira, Thiago Martini
2009-07-01
In this work it was developed a software that calculates automatically, the thermal diffusivity value as a function of temperature in materials. The infrared thermography technique was used for data acquisition of temperature distribution as a function of time. These data were used to adjust a temperature function obtained from the homogeneous heat equation with specific boundary conditions. For that, an infrared camera (detecting from 8 {mu}m to 9 {mu}m) was calibrated to detect temperature ranging from 185 degree C up to 1300 degree C at an acquisition rate of 300 Hz. It was used, 10 samples of dental enamel and 10 samples of dentin, with 4 mm x 4 mm x 2 mm, which were obtained from bovine lower incisor teeth. These samples were irradiated with an Er:Cr:YSGG pulsed laser ({lambda} = 2,78 {mu}m). The resulting temperature was recorded 2 s prior, 10 s during irradiation and continuing for 2 more seconds after it. After each irradiation, all obtained thermal images were processed in the software, creating a file with the data of thermal diffusivity as a function of temperature. Another file with the thermal diffusivity values was also calculated after each laser pulse. The mean result of thermal diffusivity obtained for dental enamel was 0,0084 {+-} 0,001 cm2/s for the temperature interval of 220-550 degree C. The mean value for thermal diffusivity obtained for dentin was 0,0015 0,0004 cm2/s in temperatures up to 360 degree C; however, this value increases for higher temperatures. According to these results, it was possible to conclude that the use of infrared thermography, associated with the software developed in this work, is an efficient method to determine the thermal diffusivity values as a function of temperature in different materials. (author)
International Nuclear Information System (INIS)
Cintra Filho, J. de S.
1981-01-01
The fluctuating temperature field structure is studied for the case of turbulent circular pipe flow. Experimentally determined integral length scales are used in modeling this structure in terms of axisymmetric forms. It is found that the appropriate angle of axisymmetry is larger than the one for modeling the large scale velocity structure. The axisymmetric model is then used to examine the validity and the prediction capability of the Tyldesley and Silver's non-spherical eddy diffusivity theory. (Author) [pt
DEFF Research Database (Denmark)
Yu, Tao
and thermally activated building systems (TABS) for cooling and ventilation in future Danish office buildings. The new solution would have the special potential of using natural ventilation all year round even in the extremely cold seasons without any draught risk. The main focuses of this study are the energy...
International Nuclear Information System (INIS)
Shimizu, M.; Tekashita, K.
2002-01-01
A new tritium extraction system composed of a trickle-bed hydrogen/water isotopic exchange column using a hydrophobic Pt catalyst combined with an SPE-water electrolyser (EXEL-process) and a thermal diffusion column cascade was proposed for the removal of the tritium from heavy water irradiated in HMR ((Heavy Water Moderated Power Reactor), volume of heavy water = 140 m 3 and mean neutron flux = 5x10 13 n/cm 2 s). Numerical study on the extraction of tritium from the heavy water was carried out and the dimensions of proposed system were determined under the conditions that the concentration of tritium in the heavy water was kept less than 2.5 Ci/l HW . The calculation results indicated that the proposed system was designed practically. (author)
Chen, Xingyuan; Miller, Gretchen R; Rubin, Yoram; Baldocchi, Dennis D
2012-12-01
The heat pulse method is widely used to measure water flux through plants; it works by using the speed at which a heat pulse is propagated through the system to infer the velocity of water through a porous medium. No systematic, non-destructive calibration procedure exists to determine the site-specific parameters necessary for calculating sap velocity, e.g., wood thermal diffusivity and probe spacing. Such parameter calibration is crucial to obtain the correct transpiration flux density from the sap flow measurements at the plant scale and subsequently to upscale tree-level water fluxes to canopy and landscape scales. The purpose of this study is to present a statistical framework for sampling and simultaneously estimating the tree's thermal diffusivity and probe spacing from in situ heat response curves collected by the implanted probes of a heat ratio measurement device. Conditioned on the time traces of wood temperature following a heat pulse, the parameters are inferred using a Bayesian inversion technique, based on the Markov chain Monte Carlo sampling method. The primary advantage of the proposed methodology is that it does not require knowledge of probe spacing or any further intrusive sampling of sapwood. The Bayesian framework also enables direct quantification of uncertainty in estimated sap flow velocity. Experiments using synthetic data show that repeated tests using the same apparatus are essential for obtaining reliable and accurate solutions. When applied to field conditions, these tests can be obtained in different seasons and can be automated using the existing data logging system. Empirical factors are introduced to account for the influence of non-ideal probe geometry on the estimation of heat pulse velocity, and are estimated in this study as well. The proposed methodology may be tested for its applicability to realistic field conditions, with an ultimate goal of calibrating heat ratio sap flow systems in practical applications.
Mameri, A.; Tabet, F.; Hadef, A.
2017-08-01
This study addresses the influence of several operating conditions (composition and ambient pressure) on biogas diffusion flame structure and NO emissions with particular attention on thermal and chemical effect of CO2. The biogas flame is modeled by a counter flow diffusion flame and analyzed in mixture fraction space using flamelet approach. The GRI Mech-3.0 mechanism that involves 53 species and 325 reactions is adopted for the oxidation chemistry. It has been observed that flame properties are very sensitive to biogas composition and pressure. CO2 addition decreases flame temperature by both thermal and chemical effects. Added CO2 may participate in chemical reaction due to thermal dissociation (chemical effect). Excessively supplied CO2 plays the role of pure diluent (thermal effect). The ambient pressure rise increases temperature and reduces flame thickness, radiation losses and dissociation amount. At high pressure, recombination reactions coupled with chain carrier radicals reduction, diminishes NO mass fraction.
International Nuclear Information System (INIS)
Richter, Armin; Benick, Jan; Kimmerle, Achim; Hermle, Martin; Glunz, Stefan W.
2014-01-01
Thin layers of Al 2 O 3 are well known for the excellent passivation of p-type c-Si surfaces including highly doped p + emitters, due to a high density of fixed negative charges. Recent results indicate that Al 2 O 3 can also provide a good passivation of certain phosphorus-diffused n + c-Si surfaces. In this work, we studied the recombination at Al 2 O 3 passivated n + surfaces theoretically with device simulations and experimentally for Al 2 O 3 deposited with atomic layer deposition. The simulation results indicate that there is a certain surface doping concentration, where the recombination is maximal due to depletion or weak inversion of the charge carriers at the c-Si/Al 2 O 3 interface. This pronounced maximum was also observed experimentally for n + surfaces passivated either with Al 2 O 3 single layers or stacks of Al 2 O 3 capped by SiN x , when activated with a low temperature anneal (425 °C). In contrast, for Al 2 O 3 /SiN x stacks activated with a short high-temperature firing process (800 °C) a significant lower surface recombination was observed for most n + diffusion profiles without such a pronounced maximum. Based on experimentally determined interface properties and simulation results, we attribute this superior passivation quality after firing to a better chemical surface passivation, quantified by a lower interface defect density, in combination with a lower density of negative fixed charges. These experimental results reveal that Al 2 O 3 /SiN x stacks can provide not only excellent passivation on p + surfaces but also on n + surfaces for a wide range of surface doping concentrations when activated with short high-temperature treatments
Energy Technology Data Exchange (ETDEWEB)
Shimizu, M.; Ravoire, J. [Commissariat a l' Energie Atomique, Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)
1966-07-01
The natural content of tritium is so low that its measurement generally requires a preliminary enrichment. The thermal diffusion on hydrogen is studied as an enrichment method. The installation studied comprises two stages of columns of the hot-wire type, together with a device for transferring the tritium from the water sample into the hydrogen in the columns using catalytic exchange. A complete mathematical treatment for the operation of such a unit has been made and programmed for the IBM 7094 computer. An optimization has been effected by means of this program. It is shown that for similar performances, less hydrogen is retained in the case of hot-wire type columns than in the case of columns composed of concentric tubes. (authors) [French] La teneur naturelle du tritium est si faible que sa mesure demande generalement un enrichissement prealable. On etudie la diffusion thermique sur l'hydrogene comme moyen d'enrichissement. L'installation que l'on etudie comprend deux etages de colonnes du type fil chaud, et un dispositif de transfert du tritium de l'echantillon d'eau dans l'hydrogene des colonnes par echange catalytique. Un traitement mathematique complet du fonctionnement d'un tel ensemble a ete etabli et programme sur machine IBM 7094. Une optimisation a ete faite a l'aide du programme. On montre egalement qu'a performances egales, la retenue d'hydrogene est plus faible dans le cas des colonnes du type fil chaud que dans le cas des colonnes du type tubes concentriques. (auteurs)
Energy Technology Data Exchange (ETDEWEB)
Shimizu, M; Ravoire, J [Commissariat a l' Energie Atomique, Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)
1966-07-01
The natural content of tritium is so low that its measurement generally requires a preliminary enrichment. The thermal diffusion on hydrogen is studied as an enrichment method. The installation studied comprises two stages of columns of the hot-wire type, together with a device for transferring the tritium from the water sample into the hydrogen in the columns using catalytic exchange. A complete mathematical treatment for the operation of such a unit has been made and programmed for the IBM 7094 computer. An optimization has been effected by means of this program. It is shown that for similar performances, less hydrogen is retained in the case of hot-wire type columns than in the case of columns composed of concentric tubes. (authors) [French] La teneur naturelle du tritium est si faible que sa mesure demande generalement un enrichissement prealable. On etudie la diffusion thermique sur l'hydrogene comme moyen d'enrichissement. L'installation que l'on etudie comprend deux etages de colonnes du type fil chaud, et un dispositif de transfert du tritium de l'echantillon d'eau dans l'hydrogene des colonnes par echange catalytique. Un traitement mathematique complet du fonctionnement d'un tel ensemble a ete etabli et programme sur machine IBM 7094. Une optimisation a ete faite a l'aide du programme. On montre egalement qu'a performances egales, la retenue d'hydrogene est plus faible dans le cas des colonnes du type fil chaud que dans le cas des colonnes du type tubes concentriques. (auteurs)
Energy Technology Data Exchange (ETDEWEB)
Spitsberg, Irene [Materials and Process Engineering Department, GE Aircraft Engines, Evendale, OH (United States)]. E-mail: irene.spitsberg@kennametal.com; More, Karren [Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)
2006-02-15
The role of pre-oxidation surface treatments on the oxide microstructure and the failure mechanism of multi-layer thermal barrier systems based on Pt-modified NiAl bond coats and electron beam deposited thermal barrier coatings (TBCs) have been studied. The primary pre-oxidation experimental variable was the partial pressure of oxygen in the pre-oxidizing atmosphere at constant temperature and bond coat composition. The durability of TBCs deposited on surfaces following different pre-oxidation treatments were measured and compared using furnace cycling tests. The oxide layers corresponding to different levels of TBC performance were characterized microstructurally, chemically, and compositionally using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques. TBC performance was enhanced by the formation of a surface oxide having a coarse-grained columnar structure during the pre-oxidation process. Increased TBC durability was consistent with a slower oxide growth rate during exposure of the TBC to high-temperature, cyclic conditions, as was observed for this particular pre-oxidation condition. An oxide microstructure having fewer through-thickness transport pathways (grain boundaries) should also result in slower lateral oxide growth rates, consistent with a slowed rate of ratcheting as was observed in the pre-oxidized samples that had the best TBC performance. The desired surface oxide grain structure was achieved by pre-oxidizing the bond coat prior to TBC deposition at an intermediate partial pressure of oxygen.
Directory of Open Access Journals (Sweden)
Saul D. Sarria
2004-04-01
Full Text Available O resfriamento e/ou congelamento de produtos hortícolas, depois da colheita, é realizado com o objetivo de retirar o calor desses produtos, permitindo-lhes, em função disso, um tempo maior de conservação. Portanto, o conhecimento das propriedades físicas que envolvem transferência de calor do figo "Roxo de Valinhos" é útil para o cálculo de projetos e a análise de sistemas de engenharia de alimentos em geral, assim como para o emprego em equações de modelos matemáticos termodinâmicos. Neste trabalho, foram determinadas, experimentalmente, a condutividade e a difusividade térmica do figo inteiro no estádio rami e, a partir desses valores, foi determinado o calor específico. Foi utilizado o método transiente da Fonte Linear de Calor. Foi introduzida nas frutas uma sonda que contém resistência elétrica e termopares. Para manter constante a temperatura da fruta, montou-se um sistema de resfriamento a água. Encontrou-se que o figo rami apresentou um valor de condutividade térmica de 0,52 W m-1 °C, difusividade térmica de 1,56 x 10-7 m² s-1, massa específica do figo de 815,6 kg m-3 e calor específico de 4,07 kJ kg-1 °C.The post harvest cooling and/or freezing processes for horticultural products have been carried out with the objective of removing the heat from these products, allowing them a bigger period of conservation. Therefore, the knowledge of the physical properties that involve heat transference in the fig fruit "Roxo de Valinhos" is useful for calculating projects and systems of food engineering in general, as well as, for using in equations of thermodynamic mathematical models. The values of conductivity and thermal diffusivity of the whole fig fruit-rami index were determined, and from these values it was determined the value of the specific heat. For these determination it was used the transient method of the Line Heat Source. The results shown that the fig fruit has a thermal conductivity of 0.52 W m-1
International Nuclear Information System (INIS)
Zhang, X.M.; Wan, B.N.
2005-01-01
Significant improvements of plasma performance after ICRF boronization have been achieved in the full range of HT-7 operation parameters. Electron power balance is analyzed in the steady state ohmic discharges of the HT-7 tokamak. The ratio of the total radiation power to ohmic input power increases with increasing the central line-averaged electron density, but decreases with plasma current. It is obviously decreased after wall conditioning. Electron heat diffusivity χ e deduced from the power balance analysis is reduced throughout the main plasma after boronization. χ e decreases with increasing central line-averaged electron density in the parameter range of our study. After boronization, the plasma current profile is broadened and a higher current can be easily obtained on the HT-7 tokamak experiment. It is expected that the fact that the bootstrap current increases after boronization will explain these phenomena. After boronization, the plasma pressure gradient and the electron temperature near the boundary are larger than before, these factors influencing that the ratio of bootstrap current to total plasma current increases from several percent to above 10%
Energy Technology Data Exchange (ETDEWEB)
Raievski, V; Horowitz, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1955-07-01
The further method is the outcome of a technique used in the study of neutrons in scattering and slowing-down environment. In this technique, we replace the constant sources used in the classic experiences by modulated sources with a variable frequency. The object of this article is to describe the extension of the method for the mean free path for transport of thermal neutrons and also to indicate the possible applications for other sizes, as the slowing length, or the absolute value of the cross-section of the boron. (M.B.) [French] La methode qui va etre decrite est l'aboutissement d'une technique utilisee dans l'etude des milieux ou diffusent et se ralentissent des neutrons. Dans cette technique, on remplace les sources constantes utilisees dans les experiences classiques par des sources modulees, a frequence variable. L'objet de cet article est de decrire l'extension de la methode a la mesure du libre parcours moyen de transport des neutrons thermiques et egalement d'indiquer les applications possibles a la mesure d'autres grandeurs, telles que la longueur de ralentissement, ou la valeur absolue de la section de capture du bore. (M.B.)
Moriyama, Eduardo H.; Zangaro, Renato A.; Lobo, Paulo D. d. C.; Villaverde, Antonio G. J. B.; Watanabe-Sei, Ii; Pacheco, Marcos T. T.; Otsuka, Daniel K.
2002-06-01
Thermal damage in dental pulp during Nd:YAG laser irradiation have been studied by several researchers; but due to dentin inhomogeneous structure, laser interaction with dentin in the hypersensitivity treatment are not fully understood. In this work, heat distribution profile on human dentine samples irradiated with Nd:YAG laser was simulated at surface and subjacent layers. Calculations were carried out using the Crank-Nicolson's finite difference method. Sixteen dentin samples with 1,5 mm of thickness were evenly distributed into four groups and irradiated with Nd:YAG laser pulses, according to the following scheme: (I) 1 pulse of 900 mJ, (II) 2 pulses of 450 mJ, (III) 3 pulses of 300 mJ, (IV) 6 pulses of 150 mJ; corresponding to a total laser energy of 900 mJ. The pulse interval was 300ms, the pulse duration of 900 ms and irradiated surface area of 0,005 mm2. Laser induced morphological changes in dentin were observed for all the irradiated samples. The heat distribution throughout the dentin layer, from the external dentin surface to the pulpal chamber wall, was calculated for each case, in order to obtain further information about the pulsed Nd:YAG laser-oral hard tissue interaction. The simulation showed significant differences in the final temperature at the pulpal chamber, depending on the exposition time and the energy contained in the laser pulse.
Directory of Open Access Journals (Sweden)
Katy Regina Peotta Zanini
2011-07-01
Full Text Available Para alimentos que se aquecem por condução, o conhecimento da propriedade difusividade térmica permite predizer a velocidade de penetração de calor no interior do alimento. Dessa maneira, ela é fundamental para o cálculo do processamento térmico, pois conhecendo o microrganismo alvo do processo, sua resistência térmica e o perfil de penetração de calor no alimento é possível estabelecer o processo térmico adequado de forma a garantir a inativação bacteriana capaz de causar risco à saúde e assegurar a possibilidade de deterioração de um mínimo determinado. Empregando o modelo da difusão e o princípio dos processos divididos, este trabalho mostrou que é possível otimizar o tratamento térmico de modo a ser possível reduzir a perda de nutrientes de alimentos enlatados convencionalmente.For foods that are warmed by conduction, knowledge of the thermal diffusivity property makes it possible to predict the rate of heat penetration inside the food to calculate thermal treatment. Other important variables in this process are the target organism, its heat resistance and the profile of heat penetration in food, making it possible to establish the appropriate thermal process to ensure the inactivation of bacteria capable of causing health risks and ensure the minimum possible deterioration of nutrients. Using the diffusion model and the principle of divided processes, this study showed it is possible to optimize the heat treatment in order to be able to reduce loss of nutrients in canned foods.
Energy Technology Data Exchange (ETDEWEB)
Roy, W.K.; Ryon, M.G.; Hinzman, R.L. [Oak Ridge National Lab., TN (United States). Computer Science and Mathematics Div.
1996-03-01
The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued Kentucky Pollutant Discharge Elimination System permit No. KY 0004049. This action prompted the US Department of Energy (DOE) to request a stay of certain limits contained in the permit. An AO is being negotiated between KDOW, the US Enrichment Corporation (USEC), and DOE that will require that several studies be conducted, including this stream temperature evaluation study, in an effort to establish permit limitations. All issues associated with this AO have been resolved, and the AO is currently being signed by all parties involved. The proposed effluent temperature limit is 89 F (31.7 C) as a mean monthly temperature. In the interim, temperatures are not to exceed 95 F (35 C) as a monthly mean or 100 F (37.8 C) as a daily maximum. This study includes detailed monitoring of instream temperatures, benthic macroinvertebrate communities, fish communities, and a laboratory study of thermal tolerances.
Directory of Open Access Journals (Sweden)
I.L. Animasaun
2016-06-01
Full Text Available This article presents the effects of nonlinear thermal radiation and induced magnetic field on viscoelastic fluid flow toward a stagnation point. It is assumed that there exists a kind of chemical reaction between chemical species A and B. The diffusion coefficients of the two chemical species in the viscoelastic fluid flow are unequal. Since chemical species B is a catalyst at the horizontal surface, hence homogeneous and heterogeneous schemes are of the isothermal cubic autocatalytic reaction and first order reaction respectively. The transformed governing equations are solved numerically using Runge–Kutta integration scheme along with Newton’s method. Good agreement is obtained between present and published numerical results for a limiting case. The influence of some pertinent parameters on skin friction coefficient, local heat transfer rate, together with velocity, induced magnetic field, temperature, and concentration profiles is illustrated graphically and discussed. Based on all of these assumptions, results indicate that the effects of induced magnetic and viscoelastic parameters on velocity, transverse velocity and velocity of induced magnetic field are almost the same but opposite in nature. The strength of heterogeneous reaction parameter is very helpful to reduce the concentration of bulk fluid and increase the concentration of catalyst at the surface.
International Nuclear Information System (INIS)
Roy, W.K.; Ryon, M.G.; Hinzman, R.L.
1996-03-01
The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued Kentucky Pollutant Discharge Elimination System permit No. KY 0004049. This action prompted the US Department of Energy (DOE) to request a stay of certain limits contained in the permit. An AO is being negotiated between KDOW, the US Enrichment Corporation (USEC), and DOE that will require that several studies be conducted, including this stream temperature evaluation study, in an effort to establish permit limitations. All issues associated with this AO have been resolved, and the AO is currently being signed by all parties involved. The proposed effluent temperature limit is 89 F (31.7 C) as a mean monthly temperature. In the interim, temperatures are not to exceed 95 F (35 C) as a monthly mean or 100 F (37.8 C) as a daily maximum. This study includes detailed monitoring of instream temperatures, benthic macroinvertebrate communities, fish communities, and a laboratory study of thermal tolerances
International Nuclear Information System (INIS)
Roy, W.K.
1999-01-01
The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued Kentucky Pollutant Discharge Elimination System permit No. KY 0004049. This action prompted the US Department of Energy (DOE) to request a stay of certain limits contained in the permit. An AO is being negotiated between KDOW, the United States Enrichment Corporation (USEC), and DOE that will require that several studies be conducted, including this stream temperature evaluation study, in an effort to establish permit limitations. All issues associated with this AO have been resolved, and the AO is currently being signed by all parties involved. The proposed effluent temperature limit is 89 F (31.7C) as a mean monthly temperature. In the interim, temperatures are not to exceed 95 F (35 C) as a monthly mean or 100 F (37.8 C) as a daily maximum. This study includes detailed monitoring of instream temperatures, benthic macroinvertebrate communities, fish communities, and a laboratory study of thermal tolerances
Seo, K. I.; Park, J. H.; Kim, J. S.; Na, Y. H.; Choi, J. C.; Bae, J. S.
2009-10-01
Eu 2+-doped BaSi 2O 5 film phosphors on quartz substrates are fabricated by radio-frequency magnetron sputtering thermal diffusion. The BaSi 2O 5: Eu 2+ phosphor crystals have some preferred orientations that are lattice-spacing matched with the crystallized β- SiO 2 crystals, and they show pore and grain boundary-free morphology with a rod-like shape fused into the crystallized β- SiO 2 crystals. The BaSi 2O 5: Eu 2+ film phosphor has a high transparency, with a transmittance of about 30% in visible light. The BaSi 2O 5: Eu 2+ film phosphor shows 510 nm green emission from the f-d transition of the Eu 2+ ions, and in particular the best sample shows a green photoluminescence brightness of about 5% of a BaSi 2O 5: Eu 2+ powder phosphor screen. These excellences in optical properties can be explained by less optical scattering at pores or grain boundaries, and less reflection at the continuously index-changed interface.
Directory of Open Access Journals (Sweden)
Railia Karneta
2015-05-01
/s, between 0.297 and 1.389.10-7 m2/s, between 0.378 and 1.471. 10-7 m/s and between 0.2778 and 1.620. 10-7 m2/s respectively Keywords: thermal diffusivity, pempek lenjer, numerical method ABSTRAK Koeﬁsien difusivitas panas pada perebusan pempek lenjer harus diketahui, karena dapat ditentukan waktu pengolahan pempek yang tepat (optimal. Formula dan suhu akan mempengaruhi koeﬁsien difusivitas panas.Tujuan penelitian adalah menentukan koeﬁsien difusivitas panas pada perebusan pempek lenjer secara numerik. Variabel yang diukur adalah suhu sampel pada titik pusat (r0 = 0 cm, r1= 1 cm, r2= 2 cm, dan lama pemasakan pempek. Data yang diperoleh dianalisis menggunakan model difusivitas panas di titik sembarang dan model difusivitas panas di titik pusat, dengan program computer Engineering Equation Solver (EES Ver 8.91.Hasil penelitian menunjukkan bahwa koeﬁsien difusivitas panas pempek lenjer pada formula 1 adalah interval 0,321 - 1,515. 10-7 m/s, pada formula 2 adalah 0,297 - 1,389. 10-7 m2/s, pada formula 3 adalah 0,378 - 1,471. 10 Kata kunci: Difusivitas panas, pempek lenjer, metode numerik
Energy Technology Data Exchange (ETDEWEB)
Roy, W.K.
1999-01-01
The development of a biological monitoring plan for the receiving streams of the Paducah Gaseous Diffusion Plant (PGDP) began in the late 1980s, because of an Agreed Order (AO) issued in September 1987 by the Kentucky Division of Water (KDOW). Five years later, in September 1992, more stringent effluent limitations were imposed upon the PGDP operations when the KDOW reissued Kentucky Pollutant Discharge Elimination System permit No. KY 0004049. This action prompted the US Department of Energy (DOE) to request a stay of certain limits contained in the permit. An AO is being negotiated between KDOW, the United States Enrichment Corporation (USEC), and DOE that will require that several studies be conducted, including this stream temperature evaluation study, in an effort to establish permit limitations. All issues associated with this AO have been resolved, and the AO is currently being signed by all parties involved. The proposed effluent temperature limit is 89 F (31.7C) as a mean monthly temperature. In the interim, temperatures are not to exceed 95 F (35 C) as a monthly mean or 100 F (37.8 C) as a daily maximum. This study includes detailed monitoring of instream temperatures, benthic macroinvertebrate communities, fish communities, and a laboratory study of thermal tolerances.
International Nuclear Information System (INIS)
Hussein, H.M.; Sakr, A.M.; Amin, E.H.
2011-01-01
The objective of this paper is to assess the suitability and the accuracy of the deterministic diffusion method for the neutronic calculations of the TRIGA type research reactors in proposed condensed energy spectra of five and seven groups with one and three thermal groups respectively, using the calculational line: WIMSD-IAEA-69 nuclear data library/ WIMSD-5B lattice and cell calculations code/ CITVAP v3.1 core calculations code. Firstly, The assessment goes through analyzing the integral parameters - k e ff, ρ 238 , σ 235 , σ 238 , and C * - of the TRX and BAPL benchmark lattices and comparison with experimental and previous reference results using other ENDLs at the full energy spectra, which show good agreement with the references at both spectra. Secondly, evaluation of the 3D nuclear characteristics of three different cores of the TRR-1/M1 TRIGA Mark- III Thai research reactor, using the CITVAP v3.1 code and macroscopic cross-section libraries generated using the WIMSD-5B code at the proposed energy spectra separately. The results include the excess reactivities and the worth of control rods, which were compared with previous Monte Carlo results and experimental values, that show good agreement with the references at both energy spectra, albeit better accuracies are shown with the five groups spectrum. The results also includes neutron flux distributions which are settled for future comparisons with other calculational techniques, even, they are comparable to reactors and fuels of the same type. The study reflects the adequacy of using the pre-stated calculational line at the condensed energy spectra for evaluation of the neutronic parameters of the TRIGA type reactors, and future comparisons of the un-benchmarked results could assure this result for wider range of neutronics or safety-related parameters
Diffusion in molybdenum disilicide
International Nuclear Information System (INIS)
Salamon, M.; Mehrer, H.
2005-01-01
The diffusion behaviour of the high-temperature material molybdenum disilicide (MoSi 2 ) was completely unknown until recently. In this paper we present studies of Mo self-diffusion and compare our present results with our already published studies of Si and Ge diffusion in MoSi 2 . Self-diffusion of molybdenum in monocrystalline MoSi 2 was studied by the radiotracer technique using the radioisotope 99 Mo. Deposition of the radiotracer and serial sectioning after the diffusion anneals to determine the concentration-depth profiles was performed using a sputtering device. Diffusion of Mo is a very slow process. In the entire temperature region investigated (1437 to 2173 K), the 99 Mo diffusivities in both principal directions of the tetragonal MoSi 2 crystals obey Arrhenius laws, where the diffusion perpendicular to the tetragonal axis is faster by two to three orders of magnitude than parallel to it. The activation enthalpies for diffusion perpendicular and parallel to the tetragonal axis are Q perpendicular to = 468 kJ mol -1 (4.85 eV) and Q parallel = 586 kJ mol -1 (6.07 eV), respectively. Diffusion of Si and its homologous element Ge is fast and is mediated by thermal vacancies of the Si sublattice of MoSi 2 . The diffusion of Mo is by several orders of magnitude slower than the diffusion of Si and Ge. This large difference suggests that Si and Mo diffusion are decoupled and that the diffusion of Mo likely takes place via vacancies on the Mo sublattice. (orig.)
DEFF Research Database (Denmark)
Krusaa, Marie Rugholm; Hviid, Christian Anker; Kolarik, Jakub
ceiling panels. These panels make it possible to combine the heating/cooling ceiling with the diffuse ventilation method. The diffuse ventilation method or leak ventilation use larger surfaces to provide air into the room instead of diffusers. An office building is investigated an analysed on an annual...... basis in the dynamic building simulation tool IDA Indoor Climate and Energy (IDA ICE). The office building contains both offices and meeting rooms. Worst-case scenarios are investigated in the office building considering heat gains, solar gains and the temperature offset between supply water temperature...
Xie, Jiajun; Yuan, Chao; Luo, Yang; Yang, Yuanfei; Hu, Bin; Yu, Dunbo; Yan, Wenlong
2018-01-01
Rapidly quenched NdFeB ribbons with high coercivity were obtained by Nd70Cu30 diffusion process. Samples with a high coercivity of 22.02 kOe at room temperature were obtained after grain boundary diffusion with 20 wt% Nd70Cu30 alloys. The NdCu diffusion process promoted grain growth in the ribbons, and grain boundary phases were formed with Cu segregation among NdFeB grains. Coercivity above 10 kOe at 150 °C was achieved in the bonded magnets with NdCu content over 10 wt%. The flux loss of bonded magnets was reduced by ∼32% at 120 °C after diffusion treatment with only a small amount (2 wt%) of NdCu.
International Nuclear Information System (INIS)
Ogawa, Shingo; Asahara, Ryohei; Minoura, Yuya; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji; Sako, Hideki; Kawasaki, Naohiko; Yamada, Ichiko; Miyamoto, Takashi
2015-01-01
The thermal diffusion of germanium and oxygen atoms in HfO 2 /GeO 2 /Ge gate stacks was comprehensively evaluated by x-ray photoelectron spectroscopy and secondary ion mass spectrometry combined with an isotopic labeling technique. It was found that 18 O-tracers composing the GeO 2 underlayers diffuse within the HfO 2 overlayers based on Fick's law with the low activation energy of about 0.5 eV. Although out-diffusion of the germanium atoms through HfO 2 also proceeded at the low temperatures of around 200 °C, the diffusing germanium atoms preferentially segregated on the HfO 2 surfaces, and the reaction was further enhanced at high temperatures with the assistance of GeO desorption. A technique to insert atomically thin AlO x interlayers between the HfO 2 and GeO 2 layers was proven to effectively suppress both of these independent germanium and oxygen intermixing reactions in the gate stacks
Energy Technology Data Exchange (ETDEWEB)
Ogawa, Shingo, E-mail: Shingo-Ogawa@trc.toray.co.jp [Toray Research Center, Inc., 3-3-7 Sonoyama, Otsu, Shiga 520-8567 (Japan); Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Asahara, Ryohei; Minoura, Yuya; Hosoi, Takuji, E-mail: hosoi@mls.eng.osaka-u.ac.jp; Shimura, Takayoshi; Watanabe, Heiji [Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Sako, Hideki; Kawasaki, Naohiko; Yamada, Ichiko; Miyamoto, Takashi [Toray Research Center, Inc., 3-3-7 Sonoyama, Otsu, Shiga 520-8567 (Japan)
2015-12-21
The thermal diffusion of germanium and oxygen atoms in HfO{sub 2}/GeO{sub 2}/Ge gate stacks was comprehensively evaluated by x-ray photoelectron spectroscopy and secondary ion mass spectrometry combined with an isotopic labeling technique. It was found that {sup 18}O-tracers composing the GeO{sub 2} underlayers diffuse within the HfO{sub 2} overlayers based on Fick's law with the low activation energy of about 0.5 eV. Although out-diffusion of the germanium atoms through HfO{sub 2} also proceeded at the low temperatures of around 200 °C, the diffusing germanium atoms preferentially segregated on the HfO{sub 2} surfaces, and the reaction was further enhanced at high temperatures with the assistance of GeO desorption. A technique to insert atomically thin AlO{sub x} interlayers between the HfO{sub 2} and GeO{sub 2} layers was proven to effectively suppress both of these independent germanium and oxygen intermixing reactions in the gate stacks.
Thermal conductivity of technetium
International Nuclear Information System (INIS)
Minato, K.; Serizawa, H.; Fukuda, K.
1998-01-01
The thermal diffusivity of technetium was measured on a disk sample of 5 mm in diameter and 1 mm in thickness by the laser flash method from room temperature to 1173 K, and the thermal conductivity was determined by the measured thermal diffusivity and density, and the reported specific heat capacity. The thermal diffusivity of technetium decreases with increasing temperature though it is almost constant above 600 K. The thermal conductivity of technetium shows a minimum around 400 K, above which the thermal conductivity increases with temperature. The electronic and phonon components of the thermal conductivity were evaluated approximately. The increase in the thermal conductivity of technetium with temperature is due to the increase in the electronic component. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Martins, Patricia de Andrade
2012-07-01
Radioisotopes of gallium have been studied and evaluated for medical applications since 1949. Over the past 50 years {sup 67}Ga has been widely used in the diagnosis of various diseases, including acute and chronic inflammatory lesions, bacterial or sterile and several types of tumors. In Brazil 30% of clinics that provide services for Nuclear Medicine use {sup 67}Ga citrate and the demand for 67{sup G}a at IPEN-CNEN/SP is 37 GBq (1 Ci)/week. The {sup 67}Ga presents physical half-life of 3.26 days (78 hours) and decays 100% by electron capture to stable {sup 67}Zn. Its decay includes the emission of {gamma} rays with energies of 93.3 keV (37%), 184.6 keV (20.4%), 300.2 keV (16.6%) and 888 keV (26%). In the past {sup 67}Ga was produced by the reaction {sup 68}Zn (p, 2n) {sup 67}Ga at IPEN-CNEN/SP. After irradiation, the target was dissolved in concentrated HCl and the solution percolated through a cationic resin DOWEX 50W-X8, 200-400 mesh, conditioned with 10 mol L{sup -1} HCl. Zinc, nickel and copper were eluted in 10 mol L{sup -1} HCl and {sup 67}Ga 3.5 mol L{sup -1} HCl. The final product was obtained as {sup 67}Ga citrate. This work presents a new, fast, direct and efficient method for the chemical separation of 67{sup G}a by thermal diffusion (heating of the target) combined with concentrated acetic acid extraction. Purification was performed by ion exchange chromatography. Natural zinc electrodeposition was performed on nickel/copper plates as substrate and the zinc deposits were adherent to the substrate, slightly shiny and uniform. The targets were irradiated with 26 MeV protons and integrated current of 10 {mu}A.h. After irradiation, the targets were heated at 300 deg C for 2 hours and placed in contact with concentrated acetic acid for 1 hour. The average yield of extraction of {sup 67}Ga was (72 {+-} 10)%. This solution was evaporated and the residue was taken up in 0.5 mol L{sup -1} NH{sub 4}OH. The 67{sup G}a was purified on cationic resin Dowex 50WX8
DEFF Research Database (Denmark)
Lestinen, Sami; Kilpeläinen, Simo; Kosonen, Risto
2018-01-01
and turbulent mixing that can further yield a draught discomfort in an occupied zone. The main objective was to investigate large-scale airflow patterns and fluctuations as a result of interaction of buoyancy flows and diffuse ceiling flow. Experiments were performed in a test room of 5.5 m (length) x 3.8 m...
International Nuclear Information System (INIS)
Wehinger, Björn; Krisch, Michael; Bosak, Alexeï; Chernyshov, Dmitry; Bulat, Sergey; Ezhov, Victor
2014-01-01
Single crystals of ice Ih, extracted from the subglacial Lake Vostok accretion ice layer (3621 m depth) were investigated by means of diffuse x-ray scattering and inelastic x-ray scattering. The diffuse scattering was identified as mainly inelastic and rationalized in the frame of ab initio calculations for the ordered ice XI approximant. Together with Monte-Carlo modelling, our data allowed reconsidering previously available neutron diffuse scattering data of heavy ice as the sum of thermal diffuse scattering and static disorder contribution. (paper)
International Nuclear Information System (INIS)
Buckler, A.N.
1978-10-01
Details of the coding techniques, with flow diagrams are given for the correlation code DELILAH which is a replacement for the SAMSON code for SGHW and other thermal systems. An improved method of rejecting inaccurate channel power measurements is described in detail. A list of the input data requirements for the code will be published separately. (author)
Space thermal control development
Hoover, M. J.; Grodzka, P. G.; Oneill, M. J.
1971-01-01
The results of experimental investigations on a number of various phase change materials (PCMs) and PCMs in combination with metals and other materials are reported. The evaluations include the following PCM system performance characteristics: PCM and PCM/filler thermal diffusivities, the effects of long-term thermal cycling, PCM-container compatibility, and catalyst effectiveness and stability. Three PCMs demonstrated performance acceptable enough to be considered for use in prototype aluminum thermal control devices. These three PCMs are lithium nitrate trihydrate with zinc hydroxy nitrate catalyst, acetamide, and myristic acid. Of the fillers tested, aluminum honeycomb filler was found to offer the most increase in system thermal diffusivity.
Shetty, Anil N; Chiang, Sharon; Maletic-Savatic, Mirjana; Kasprian, Gregor; Vannucci, Marina; Lee, Wesley
2014-01-01
In this article, we discuss the theoretical background for diffusion weighted imaging and diffusion tensor imaging. Molecular diffusion is a random process involving thermal Brownian motion. In biological tissues, the underlying microstructures restrict the diffusion of water molecules, making diffusion directionally dependent. Water diffusion in tissue is mathematically characterized by the diffusion tensor, the elements of which contain information about the magnitude and direction of diffusion and is a function of the coordinate system. Thus, it is possible to generate contrast in tissue based primarily on diffusion effects. Expressing diffusion in terms of the measured diffusion coefficient (eigenvalue) in any one direction can lead to errors. Nowhere is this more evident than in white matter, due to the preferential orientation of myelin fibers. The directional dependency is removed by diagonalization of the diffusion tensor, which then yields a set of three eigenvalues and eigenvectors, representing the magnitude and direction of the three orthogonal axes of the diffusion ellipsoid, respectively. For example, the eigenvalue corresponding to the eigenvector along the long axis of the fiber corresponds qualitatively to diffusion with least restriction. Determination of the principal values of the diffusion tensor and various anisotropic indices provides structural information. We review the use of diffusion measurements using the modified Stejskal-Tanner diffusion equation. The anisotropy is analyzed by decomposing the diffusion tensor based on symmetrical properties describing the geometry of diffusion tensor. We further describe diffusion tensor properties in visualizing fiber tract organization of the human brain.
DEFF Research Database (Denmark)
Zhang, Chen; Yu, Tao; Heiselberg, Per Kvols
cooling capacity, energy saving, low investment cost and low noise level; while the limitations include condensation risk and the limit on the room geometry. Furthermore, the crucial design parameters are summarized and their effects on the system performance are discussed. In addition to the stand...... is not well structured with this system. These become the motivations in developing the design guide. This design guide aims to establish a systematic understanding of diffuse ceiling ventilation and provide assistance in designing of such a system. The guide is targeted at design engineers, architects...... and manufacturers and the users of diffuse ceiling technology. The design guide introduces the principle and key characteristics of room air distribution with diffuse ceiling ventilation. It provides an overview of potential benefit and limitations of this technology. The benefits include high thermal comfort, high...
International Nuclear Information System (INIS)
Yeh, H.-M.
2010-01-01
The effect of the increment in the number of concentric-tube thermal diffusion columns on the recovery of deuterium from H 2 -HD-D 2 system with fixed total sum of column heights, has been investigated. The equations for predicting the degrees of separation in single-column, double-column and triple-column devices have been derived. Considerable improvement in recovery can be achieved if a multi-column device with larger number of column is employed, instead of a single-column device with column height equal to the same total sum of column heights, especially for the case of higher flow-rate operation and larger total sum of column heights.
Directory of Open Access Journals (Sweden)
Savio Figueira Corrêa
2008-09-01
Full Text Available In order to determine the penetration of the thermal wave in the papaya fruit pulp (Carica papaya L., cv. Golden, thermal diffusivity of the pulp was obtained measuring temperature at four different depths. Measurements were carried out initially with the fruit on the first stage of maturity. The changes of the thermal diffusivity were expressed as a function of ripening. A temporal decrease of the thermal diffusivity was observed. Chemical (pH, soluble solids and total titratable acidity and physical (pulp firmness properties were measured as well and the results were compared to the thermal diffusivity change.Para determinar a penetração da onda térmica na polpa do fruto do mamoeiro (Carica papaya L., cv. Golden, a difusividade térmica foi obtida medindo a temperatura da polpa em quatro diferentes profundidades. As medidas foram realizadas inicialmente no estádio I de maturação do fruto, e as variações da difusividade térmica foram expressas em função do amadurecimento. Foi observada a diminuição da difusividade térmica no tempo. Propriedades químicas (pH, sólidos solúveis e acidez titulável e física (firmeza da polpa também foram determinadas, e os resultados, comparados com as variações da difusividade térmica.
International Nuclear Information System (INIS)
Carlen, E.A.
1984-01-01
In Nelson's stochastic mechanics, quantum phenomena are described in terms of diffusions instead of wave functions. These diffusions are formally given by stochastic differential equations with extremely singular coefficients. Using PDE methods, we prove the existence of solutions. This reult provides a rigorous basis for stochastic mechanics. (orig.)
Directory of Open Access Journals (Sweden)
HADEF AMAR
2016-03-01
Full Text Available Highly exothermic reactions are responsible for the formation of harmful polluting chemical species to humans and the biosphere. In this context, nitrogen oxides (NOx are pollutants that are the subject of special attention on the part of regulators. In this work we studied the impact of a co-flow swirl on the internal structure of a turbulent diffusion flame H2-N2/Air and its role in reducing the formation of NO, which is modeled by the concept of laminar flamelet, while the flow field is modeled by the standard model k-ε, with a correction term for round jets.The results show good agreement with data from the experimental data.
Characterization of Cu3SbS3 thin films grown by thermally diffusing Cu2S and Sb2S3 layers
Hussain, Arshad; Ahmed, Rashid; Ali, N.; Shaari, A.; Luo, Jing-Ting; Fu, Yong Qing
2017-01-01
Copper antimony sulphide (Cu3SbS3) with a p-type conductivity and optical band gaps in the range of 1.38 to 1.84 eV is considered to be a promising solar harvesting material with non-toxic and economical elements. In this study, we reported the fabrication of Cu3SbS3 thin films using successive thermal evaporation of Cu2S and Sb2S3 layers followed by annealing in an argon atmosphere at a temperature range of 300-375°C. The structural and optical properties of the as-deposited and annealed fil...
Diffusion in liquids a theoretical and experimental study
Tyrrell, H J V
1984-01-01
Diffusion in Liquids: A Theoretical and Experimental Study aims to discuss the principles, applications, and advances in the field of diffusion, thermal diffusion, and thermal conduction in liquid systems. The book covers topics such as the principles of non-equilibrium thermodynamics; diffusion in binary and multicompetent systems; and experimental methods of studying diffusion processes in liquids. Also covered in the book are topics such as the theoretical interpretations of diffusion coefficients; hydrodynamic and kinetic theories; and diffusion in electrolyte systems. The text is recommen
Directory of Open Access Journals (Sweden)
Dulal Pal
2017-03-01
Full Text Available The study of magnetohydrodynamic (MHD convective heat and mass transfer near a stagnation-point flow over stretching/shrinking sheet of nanofluids is presented in this paper by considering thermal radiation, Ohmic heating, viscous dissipation and heat source/sink parameter effects. Non-similarity method is adopted for the governing basic equations before they are solved numerically using Runge-Kutta-Fehlberg method using shooting technique. The numerical results are validated by comparing the present results with previously published results. The focus of this paper is to study the effects of some selected governing parameters such as Richardson number, radiation parameter, Schimdt number, Eckert number and magnetic parameter on velocity, temperature and concentration profiles as well as on skin-friction coefficient, local Nusselt number and Sherwood number.
Diffusion of condenser water discharge
International Nuclear Information System (INIS)
Iwakiri, Toshio
1977-01-01
Thermal and nuclear power stations in Japan are mostly located in coastal area, and the cooling water is discharged into sea as warm water. Recently, large interest is taken in this matter, and it is desirable to predict the diffusion of warm discharge accurately and to take effective measures for lowering the temperature. As for the methods of predicting the diffusion of warm discharge, simplified estimation, mathematical analysis and hydrographical model experiment are used corresponding to objects and conditions. As for the measures to lower temperature, the method of discharging warm water into deep sea bottom was confirmed to be very effective. In this paper, the phenomena of diffusion of warm discharge in sea, the methods of predicting the diffusion of warm discharge, and the deep sea discharge as the measure for lowering temperature are outlined. The factors concerning the diffusion of warm discharge in sea are the conditions of discharge, topography and sea state, and the diffusion is roughly divided into mixing diffusion in the vicinity of warm water outlet and eddy diffusion in distant region. It is difficult to change artificially the conditions of diffusion in distant region, and the measures of raising the rate of dilution in near region are effective, therefore the deep sea discharge is adopted. (Kako, I.)
Fractional Diffusion Equations and Anomalous Diffusion
Evangelista, Luiz Roberto; Kaminski Lenzi, Ervin
2018-01-01
Preface; 1. Mathematical preliminaries; 2. A survey of the fractional calculus; 3. From normal to anomalous diffusion; 4. Fractional diffusion equations: elementary applications; 5. Fractional diffusion equations: surface effects; 6. Fractional nonlinear diffusion equation; 7. Anomalous diffusion: anisotropic case; 8. Fractional Schrödinger equations; 9. Anomalous diffusion and impedance spectroscopy; 10. The Poisson–Nernst–Planck anomalous (PNPA) models; References; Index.
Plasma diffusion due to magnetic field fluctuations
International Nuclear Information System (INIS)
Okuda, H.; Lee, W.W.; Lin, A.T.
1979-01-01
Plasma diffusion due to magnetic field fluctuations has been studied in two dimensions for a plasma near thermal equilibrium and when the fluctuations are suprathermal. It is found that near thermal equilibrium electron diffusion varies as B -2 when the collisionless skin depth is greater than the thermal electron gyroradius and is generally smaller than the diffusion due to collisions or electrostatic fluctuations for a low-β plasma. When the suprathermal magnetic fluctuation exists because of macroscopic plasma currents, electron diffusion is enhanced due to the coalescence of current filaments and magnetic islands. Magnetic field energy is found to condense to the longest wavelength available in the system and stays there longer than the electron diffusion time scale
Energy Technology Data Exchange (ETDEWEB)
Van Craeynest, J C; Weilbacher, J C; Lallement, R [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires
1969-07-01
We have built two types of apparatus to measure the thermal diffusivity of ceramic fuels. The first apparatus, based on Angstrom's method, operates between 0 deg. C and 1000 deg. C. Satisfactory results have been obtained for iron, nickel and molybdenum. The other apparatus, based on Cowan's method, operates between 1000 deg. C and 2000 deg. C on thin slabs. The thermal conductivity of UO{sub 2} has been measured from 0 deg. C to 2000 deg. C. There is a good agreement between our results and the well known values for UO{sub 2}. (authors) [French] Afin d'etudier la conductibilite thermique des combustibles ceramiques, nous avons mis au point deux types d'appareils nous permettant de mesurer la diffusivite thermique {alpha}, la conductibilite etant egale au produit de la diffusivite par la densite et la chaleur specifique. Un premier type d'appareil base sur la methode d'Angstroem nous permet d'obtenir des resultats de diffusivite sur echantillon de fabrication courante entre 0 deg.C et 1000 deg. C. Une serie de mesures a ete effectuee sur le fer, le nickel et le molybdene afin de controler le bon fonctionnement des appareils. Un deuxieme type d'appareil base sur la methode de Cowan nous permet d'atteindre la diffusivite thermique d'echantillons minces entre 1000 deg. C et 2000 deg. C. Un controle des resultats obtenus sur l'oxyde d'uranium a moyenne et haute temperature nous permet de conclure a un tres bon accord entre nos resultats et ceux de la litterature. (auteurs)
Energy Technology Data Exchange (ETDEWEB)
Bardóczi, L.; Rhodes, T. L.; Carter, T. A.; Crocker, N. A.; Peebles, W. A. [University of California Los Angeles, Los Angeles, California 90095 (United States); Grierson, B. A. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
2016-05-15
Neoclassical tearing modes (NTMs) often lead to the decrease of plasma performance and can lead to disruptions, which makes them a major impediment in the development of operating scenarios in present toroidal fusion devices. Recent gyrokinetic simulations predict a decrease of plasma turbulence and cross-field transport at the O-point of the islands, which in turn affects the NTM dynamics. In this paper, a heat transport model of magnetic islands employing spatially non-uniform cross-field thermal diffusivity (χ{sub ⊥}) is presented. This model is used to derive χ{sub ⊥} at the O-point from electron temperature data measured across 2/1 NTM islands in DIII-D. It was found that χ{sub ⊥} at the O-point is 1 to 2 orders of magnitude smaller than the background plasma transport, in qualitative agreement with gyrokinetic predictions. As the anomalously large values of χ{sub ⊥} are often attributed to turbulence driven transport, the reduction of the O-point χ{sub ⊥} is consistent with turbulence reduction found in recent experiments. Finally, the implication of reduced χ{sub ⊥} at the O-point on NTM dynamics was investigated using the modified Rutherford equation that predicts a significant effect of reduced χ{sub ⊥} at the O-point on NTM saturation.
Integrated Temperature Sensors based on Heat Diffusion
Van Vroonhoven, C.P.L.
2015-01-01
This thesis describes the theory, design and implementation of a new class of integrated temperature sensors, based on heat diffusion. In such sensors, temperature is sensed by measuring the time it takes for heat to diffuse through silicon. An on-chip thermal delay can be determined by geometry and
Mid infrared upconversion spectroscopy using diffuse reflectance
DEFF Research Database (Denmark)
Sanders, Nicolai Højer; Kehlet, Louis M.; Dam, Jeppe Seidelin
2014-01-01
specifically that upconversion methods can be deployed using a diffuse reflectance setup where the test sample is irradiated by a thermal light source, i.e. a globar. The diffuse reflectance geometry is particularly well suited when a transmission setup cannot be used. This situation may happen for highly...
International Nuclear Information System (INIS)
Anderson, R.C.
1976-01-01
A method is described for joining beryllium to beryllium by diffusion bonding. At least one surface portion of at least two beryllium pieces is coated with nickel. A coated surface portion is positioned in a contiguous relationship with another surface portion and subjected to an environment having an atmosphere at a pressure lower than ambient pressure. A force is applied on the beryllium pieces for causing the contiguous surface portions to abut against each other. The contiguous surface portions are heated to a maximum temperature less than the melting temperature of the beryllium, and the applied force is decreased while increasing the temperature after attaining a temperature substantially above room temperature. A portion of the applied force is maintained at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions
International Nuclear Information System (INIS)
Lalis, A.; Rouviere, R.; Simon, G.
1976-01-01
A multipassage diffuser having 2p passages comprises a leak-tight cylindrical enclosure closed by a top cover and a bottom end-wall, parallel porous tubes which are rigidly assembled in sectors between tube plates and through which the gas mixture flows, the tube sectors being disposed at uniform intervals on the periphery of the enclosure. The top tube plates are rigidly fixed to an annular header having the shape of a half-torus and adapted to communicate with the tubes of the corresponding sector. Each passage is constituted by a plurality of juxtaposed sectors in which the mixture circulates in the same direction, the header being divided into p portions limited by radial partition-walls and each constituting two adjacent passages. The diffuser is provided beneath the bottom end-wall with p-1 leak-tight chambers each adapted to open into two different portions of the header, and with two collector-chambers each fitted with a nozzle for introducing the gas mixture and discharging the fraction of the undiffused mixture. By means of a central orifice formed in the bottom end-wall the enclosure communicates with a shaft for discharging the diffused fraction of the gas mixture
Energy Technology Data Exchange (ETDEWEB)
Gerl, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1968-01-01
An experimental study of diffusion under a thermal gradient shows that the heat of transport Q-bar* for self-diffusion in the noble metals is very low (a few hundredths of I eV) and relatively large in Fe{alpha} (+ 1,7 {+-} 0,8 eV). The apparent heat of transport of Sb in Cu, measured by the 'thin layer technique' is -0.21 {+-}0,05 eV.The influence of the density of sources and sinks of vacancies on the observed vacancy flux is determined by a calculation involving the thermodynamics of irreversible processes; when the mean distance between sources and sinks is larger than a certain limiting value, the vacancy flux vanishes.The contribution to the heat of transport of electron-defect (q*e) and phonon-defect (q*p) collisions is calculated using a semi-classical approach and by a quantum mechanical method; q*e is related to the resistivity {delta} -{rho}{sub d} and to the thermoelectric power of the defect at its stable position and at its saddle-point. A relation between q*e and the effective valency Z* of the defect allows a determination of {delta}{sub {rho}}{sub d} at the saddle-point. Numerical values of q*e are given for some impurities in noble metals. (author) [French] L'etude experimentale de la diffusion sous gradient de temperature montre que la chaleur de transport d'autodiffusion des metaux nobles est tres faible (quelques centiemes d'eV), alors que celle de Fe{alpha} est relativement elevee (+1,7 {+-} 0,8 eV). La chaleur de transport apparente de Sb dans Cu, mesuree par la technique de la couche mince, est (-0.21 {+-} 0.05 eV). L'influence de la densite de sources et puits de lacunes sur le flux de lacunes observe est determinee en appliquant le formalisme de la thermodynamique des processus irreversibles; si la distance moyenne entre sources et puits excede une certaine valeur limite, le flux de lacunes devient pratiquement nul. La contribution des chocs electrons-defaut (q*e) et phonons-defaut (q*p) a la chaleur de transport,est calcul theoriquement a
Energy Technology Data Exchange (ETDEWEB)
Gerl, M. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1968-01-01
An experimental study of diffusion under a thermal gradient shows that the heat of transport Q-bar* for self-diffusion in the noble metals is very low (a few hundredths of I eV) and relatively large in Fe{alpha} (+ 1,7 {+-} 0,8 eV). The apparent heat of transport of Sb in Cu, measured by the 'thin layer technique' is -0.21 {+-}0,05 eV.The influence of the density of sources and sinks of vacancies on the observed vacancy flux is determined by a calculation involving the thermodynamics of irreversible processes; when the mean distance between sources and sinks is larger than a certain limiting value, the vacancy flux vanishes.The contribution to the heat of transport of electron-defect (q*e) and phonon-defect (q*p) collisions is calculated using a semi-classical approach and by a quantum mechanical method; q*e is related to the resistivity {delta} -{rho}{sub d} and to the thermoelectric power of the defect at its stable position and at its saddle-point. A relation between q*e and the effective valency Z* of the defect allows a determination of {delta}{sub {rho}}{sub d} at the saddle-point. Numerical values of q*e are given for some impurities in noble metals. (author) [French] L'etude experimentale de la diffusion sous gradient de temperature montre que la chaleur de transport d'autodiffusion des metaux nobles est tres faible (quelques centiemes d'eV), alors que celle de Fe{alpha} est relativement elevee (+1,7 {+-} 0,8 eV). La chaleur de transport apparente de Sb dans Cu, mesuree par la technique de la couche mince, est (-0.21 {+-} 0.05 eV). L'influence de la densite de sources et puits de lacunes sur le flux de lacunes observe est determinee en appliquant le formalisme de la thermodynamique des processus irreversibles; si la distance moyenne entre sources et puits excede une certaine valeur limite, le flux de lacunes devient pratiquement nul. La contribution des chocs electrons-defaut (q*e) et phonons-defaut (q*p) a la chaleur de
Thermal transfer in multilayer materials
Energy Technology Data Exchange (ETDEWEB)
Bouayad, H.; Mokhtari, A.; Martin, C.; Fauchais, P. [Laboratoire de Materiaux Ceramiques et Traitements de Surface, 87 - Limoges (France)
1993-12-31
It is easier to measure the thermal diffusivity (a) of material rather than its thermal conductivity (k), a simple relationship (k=a cp) allowing to calculate k provided and cp are measured. However this relationship applies only if the considered material is homogenous. For composite materials, especially for multilayers ones, we have developed an analytical model and a numerical one. The first one allows to determine the thermal diffusivity and conductivity of a two-layer material. The second one allows to determine the thermal diffusivity of one of the layers provided the values of (a) are known for the two other layers (for a two or three-layer material). The use of the two models to calculate the apparent diffusivity of a two layer material results in values in fairly good agreement. (Authors). 4 refs., 3 figs., 3 tabs.
International Nuclear Information System (INIS)
Habib, S.
1994-01-01
We consider a simple quantum system subjected to a classical random force. Under certain conditions it is shown that the noise-averaged Wigner function of the system follows an integro-differential stochastic Liouville equation. In the simple case of polynomial noise-couplings this equation reduces to a generalized Fokker-Planck form. With nonlinear noise injection new ''quantum diffusion'' terms rise that have no counterpart in the classical case. Two special examples that are not of a Fokker-Planck form are discussed: the first with a localized noise source and the other with a spatially modulated noise source
Hereditary Diffuse Gastric Cancer
... Hereditary Diffuse Gastric Cancer Request Permissions Hereditary Diffuse Gastric Cancer Approved by the Cancer.Net Editorial Board , 10/2017 What is hereditary diffuse gastric cancer? Hereditary diffuse gastric cancer (HDGC) is a rare ...
Watson, E. B.; Cherniak, D. J.
1997-05-01
Oxygen diffusion in natural, non-metamict zircon was characterized under both dry and water-present conditions at temperatures ranging from 765°C to 1500°C. Dry experiments were performed at atmospheric pressure by encapsulating polished zircon samples with a fine powder of 18O-enriched quartz and annealing the sealed capsules in air. Hydrothermal runs were conducted in cold-seal pressure vessels (7-70 MPa) or a piston cylinder apparatus (400-1000 MPa) on zircon samples encapsulated with both 18O-enriched quartz and 18O water. Diffusive-uptake profiles of 18O were measured in all samples with a particle accelerator, using the 18O(p, α) 15N reaction. For dry experimental conditions at 1100-1500°C, the resulting oxygen diffusivities (24 in all) are well described by: D dry (m 2/s) = 1.33 × 10 -4exp(-53920/T) There is no suggestion of diffusive anisotropy. Under wet conditions at 925°C, oxygen diffusion shows little or no dependence upon P H 2O in the range 7-1000 MPa, and is insensitive to total pressure as well. The results of 27 wet experiments at 767-1160°C and 7-1000 MPa can be described a single Arrhenius relationship: D wet (m 2/s) = 5.5 × 10 -12exp(-25280/T) The insensitivity of oxygen diffusion to P H 2O means that applications to geologic problems can be pursued knowing only whether the system of interest was 'wet' (i.e., P H 2O > 7MPa ) or 'dry'. Under dry conditions (presumably rare in the crust), zircons are extremely retentive of their oxygen isotopic signatures, to the extent that δ 18O would be perturbed at the center of a 200 μm zircon only during an extraordinarily hot and protracted event (e.g., 65 Ma at 900°C). Under wet conditions, δ 18O may or may not be retained in the central regions of individual crystals, cores or overgrowth rims, depending upon the specific thermal history of the system.
Thermal and optical properties of porous silicon
Directory of Open Access Journals (Sweden)
Silva A. Ferreira da
2001-01-01
Full Text Available Thermal diffusivity and optical absorption have been investigated for porous silicon, at room temperature, using photoacoustic spectroscopy. The experimental results obtained conform well with the existing studies recently published. The value obtained for thermal diffusivity is 0.045 ± 0.002 cm²/s.The absorption onsets show energy structures, differing from the ordinary semiconductor of bulk type.
Laboratory measurements of rock thermal properties
DEFF Research Database (Denmark)
Bording, Thue Sylvester; Balling, N.; Nielsen, S.B.
The thermal properties of rocks are key elements in understanding and modelling the temperature field of the subsurface. Thermal conductivity and thermal diffusivity can be measured in the laboratory if rock samples can be provided. We have introduced improvements to the divided bar and needle...... probe methods to be able to measure both thermal conductivity and thermal diffusivity. The improvements we implement include, for both methods, a combination of fast numerical finite element forward modelling and a Markov Chain Monte Carlo inversion scheme for estimating rock thermal parameters...
Diffusion archeology for diffusion progression history reconstruction.
Sefer, Emre; Kingsford, Carl
2016-11-01
Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring - perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial diffusion data. Here, we tackle the problem of reconstructing a diffusion history from one or more snapshots of the diffusion state. This ability can be invaluable to learn when certain computer nodes are infected or which people are the initial disease spreaders to control future diffusions. We formulate this problem over discrete-time SEIRS-type diffusion models in terms of maximum likelihood. We design methods that are based on submodularity and a novel prize-collecting dominating-set vertex cover (PCDSVC) relaxation that can identify likely diffusion steps with some provable performance guarantees. Our methods are the first to be able to reconstruct complete diffusion histories accurately in real and simulated situations. As a special case, they can also identify the initial spreaders better than the existing methods for that problem. Our results for both meme and contaminant diffusion show that the partial diffusion data problem can be overcome with proper modeling and methods, and that hidden temporal characteristics of diffusion can be predicted from limited data.
Mechanical, Hygric and Thermal Properties of Flue Gas Desulfurization Gypsum
Directory of Open Access Journals (Sweden)
P. Tesárek
2004-01-01
Full Text Available The reference measurements of basic mechanical, thermal and hygric parameters of hardened flue gas desulfurization gypsum are carried out. Moisture diffusivity, water vapor diffusion coefficient, thermal conductivity, volumetric heat capacity and linear thermal expansion coefficient are determined with the primary aim of comparison with data obtained for various types of modified gypsum in the future.
Diffused zircaloy 2/stainless steel junctions
International Nuclear Information System (INIS)
Jacques, F.
1964-01-01
The diffusion permits to realize joints between two different materials, in fact of the formation of a liquid phase at the contact face. The study of the tensile properties allowed the determination of the ideal conditions for the diffusion treatment which are, within 2 and 3 minutes for a temperature within 1020 C and 1030 C. The characteristics of the so obtained joints were, studied: mechanical properties, tightness, resistance to thermal cycling. Analysis of the thermal stress, owing to the differential dilatation of the two materials mode the object of a particular study. The investigation on the diffusion zone, includes specially, an analysis of the constituents distribution formed during the diffusion treatment. (author) [fr
Self-diffusion and solute diffusion in alloys under irradiation: Influence of ballistic jumps
International Nuclear Information System (INIS)
Roussel, Jean-Marc; Bellon, Pascal
2002-01-01
We have studied the influence of ballistic jumps on thermal and total diffusion of solvent and solute atoms in dilute fcc alloys under irradiation. For the diffusion components that result from vacancy migration, we introduce generalized five-frequency models, and show that ballistic jumps produce decorrelation effects that have a moderate impact on self-diffusion but that can enhance or suppress solute diffusion by several orders of magnitude. These could lead to new irradiation-induced transformations, especially in the case of subthreshold irradiation conditions. We also show that the mutual influence of thermal and ballistic jumps results in a nonadditivity of partial diffusion coefficients: the total diffusion coefficient under irradiation may be less than the sum of the thermal and ballistic diffusion coefficients. These predictions are confirmed by kinetic Monte Carlo simulations. Finally, it is shown that the method introduced here can be extended to take into account the effect of ballistic jumps on the diffusion of dumbbell interstitials in dilute alloys
Analysis of current diffusive ballooning mode
International Nuclear Information System (INIS)
Yagi, M.; Azumi, M.; Itoh, K.; Itoh, S.; Fukuyama, A.
1993-04-01
The current diffusive ballooning mode is analysed in the tokamak plasma. This mode is destabilized by the current diffusivity (i.e., the electron viscosity) and stabilized by the thermal conductivity and ion viscosity. By use of the ballooning transformation, the eigenmode equation is solved. Analytic solution is obtained by the strong ballooning limit. Numerical calculation is also performed to confirm the analytic theory. The growth rate of the mode and the mode structure are analysed. The stability boundary is derived in terms of the current diffusivity, thermal conductivity, ion viscosity and the pressure gradient for the given shear parameter. This result is applied to express the thermal conductivity in terms of the pressure gradient, magnetic configurational parameters (such as the safety factor, shear and aspect ratio) and the Prandtl numbers. (author)
Energy Technology Data Exchange (ETDEWEB)
Sallaberry, F.; Garcia de Jalon, A.; Ramirez, L.; Olano, X.; Bernad, I.; Erice, R.
2008-07-01
In this paper we will show the results of the analysis of factors that influence the estimation of optical efficiency of solar thermal collectors testes according to the European standard UNE-EN 12975-2. Indoor tests with solar simulator involve control of the spectrum of its lamps to ensure that the difference with the Sun one does not change the optical efficiency {eta}{sub 0} of the collector. For outdoor tests, the diffuse radiation should be control as well. In the laboratory (LCS) of CENER, solar collectors tests are done according to part 6.1 of the standard UNE{sub E}N 12975-2 in continuous solar simulator. This study estimated the spectral correction applied to the estimation of optical efficiency of some solar collectors, with different selective materials. Likewise, we will weight the influence of terms related to diffuse radiation and spectral distribution. (Author)
Thermal Pyrolytic Graphite Enhanced Components
Hardesty, Robert E. (Inventor)
2015-01-01
A thermally conductive composite material, a thermal transfer device made of the material, and a method for making the material are disclosed. Apertures or depressions are formed in aluminum or aluminum alloy. Plugs are formed of thermal pyrolytic graphite. An amount of silicon sufficient for liquid interface diffusion bonding is applied, for example by vapor deposition or use of aluminum silicon alloy foil. The plugs are inserted in the apertures or depressions. Bonding energy is applied, for example by applying pressure and heat using a hot isostatic press. The thermal pyrolytic graphite, aluminum or aluminum alloy and silicon form a eutectic alloy. As a result, the plugs are bonded into the apertures or depressions. The composite material can be machined to produce finished devices such as the thermal transfer device. Thermally conductive planes of the thermal pyrolytic graphite plugs may be aligned in parallel to present a thermal conduction path.
SOME MOISTURE DEPENDENT THERMAL PROPERTIES AND ...
African Journals Online (AJOL)
The thermal heat conductivity, specific heat capacity, thermal heat diffusivity and bulk density of Prosopis africana seeds were determined as a function of moisture content. Specific heat capacity was measured by the method of mixture while the thermal heat conductivity was measured by the guarded hot plate method.
Diffusion and transport coefficients in synthetic opals
International Nuclear Information System (INIS)
Sofo, J. O.; Mahan, G. D.
2000-01-01
Opals are structures composed of close-packed spheres in the size range of nano to micrometers. They are sintered to create small necks at the points of contact. We have solved the diffusion problem in such structures. The relation between the diffusion coefficient and the thermal and electrical conductivity is used to estimate the transport coefficients of opal structures as a function of the neck size and the mean free path of the carriers. The theory presented is also applicable to the diffusion problem in other periodic structures. (c) 2000 The American Physical Society
Diffusing diffusivity: Rotational diffusion in two and three dimensions
Jain, Rohit; Sebastian, K. L.
2017-06-01
We consider the problem of calculating the probability distribution function (pdf) of angular displacement for rotational diffusion in a crowded, rearranging medium. We use the diffusing diffusivity model and following our previous work on translational diffusion [R. Jain and K. L. Sebastian, J. Phys. Chem. B 120, 3988 (2016)], we show that the problem can be reduced to that of calculating the survival probability of a particle undergoing Brownian motion, in the presence of a sink. We use the approach to calculate the pdf for the rotational motion in two and three dimensions. We also propose new dimensionless, time dependent parameters, αr o t ,2 D and αr o t ,3 D, which can be used to analyze the experimental/simulation data to find the extent of deviation from the normal behavior, i.e., constant diffusivity, and obtain explicit analytical expressions for them, within our model.
International Nuclear Information System (INIS)
Tiwari, G.P.; Kale, G.B.; Patil, R.V.
1999-01-01
The article presents a brief survey of process of diffusion in solids. It is emphasised that the essence of diffusion is the mass transfer through the atomic jumps. To begin with formal equations for diffusion coefficient are presented. This is followed by discussions on mechanisms of diffusion. Except for solutes which form interstitial solid solution, diffusion in majority of cases is mediated through exchange of sites between an atom and its neighbouring vacancy. Various vacancy parameters such as activation volume, correlation factor, mass effect etc are discussed and their role in establishing the mode of diffusion is delineated. The contribution of dislocations and grain boundaries in diffusion process is brought out. The experimental determination of different types of diffusion coefficients are described. Finally, the pervasive nature of diffusion process in number of commercial processes is outlined to show the importance of diffusion studies in materials science and technology. (author)
Thermal conductivity of supercooled water.
Biddle, John W; Holten, Vincent; Sengers, Jan V; Anisimov, Mikhail A
2013-04-01
The heat capacity of supercooled water, measured down to -37°C, shows an anomalous increase as temperature decreases. The thermal diffusivity, i.e., the ratio of the thermal conductivity and the heat capacity per unit volume, shows a decrease. These anomalies may be associated with a hypothesized liquid-liquid critical point in supercooled water below the line of homogeneous nucleation. However, while the thermal conductivity is known to diverge at the vapor-liquid critical point due to critical density fluctuations, the thermal conductivity of supercooled water, calculated as the product of thermal diffusivity and heat capacity, does not show any sign of such an anomaly. We have used mode-coupling theory to investigate the possible effect of critical fluctuations on the thermal conductivity of supercooled water and found that indeed any critical thermal-conductivity enhancement would be too small to be measurable at experimentally accessible temperatures. Moreover, the behavior of thermal conductivity can be explained by the observed anomalies of the thermodynamic properties. In particular, we show that thermal conductivity should go through a minimum when temperature is decreased, as Kumar and Stanley observed in the TIP5P model of water. We discuss physical reasons for the striking difference between the behavior of thermal conductivity in water near the vapor-liquid and liquid-liquid critical points.
Diffusion archeology for diffusion progression history reconstruction
Sefer, Emre; Kingsford, Carl
2015-01-01
Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring — perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial d...
Inverse diffusion theory of photoacoustics
International Nuclear Information System (INIS)
Bal, Guillaume; Uhlmann, Gunther
2010-01-01
This paper analyzes the reconstruction of diffusion and absorption parameters in an elliptic equation from knowledge of internal data. In the application of photoacoustics, the internal data are the amount of thermal energy deposited by high frequency radiation propagating inside a domain of interest. These data are obtained by solving an inverse wave equation, which is well studied in the literature. We show that knowledge of two internal data based on well-chosen boundary conditions uniquely determines two constitutive parameters in diffusion and Schrödinger equations. Stability of the reconstruction is guaranteed under additional geometric constraints of strict convexity. No geometric constraints are necessary when 2n internal data for well-chosen boundary conditions are available, where n is spatial dimension. The set of well-chosen boundary conditions is characterized in terms of appropriate complex geometrical optics solutions
Contribution of thermal expansion and
Directory of Open Access Journals (Sweden)
O.I.Pursky
2007-01-01
Full Text Available A theoretical model is developed to describe the experimental results obtained for the isobaric thermal conductivity of rare gas solids (RGS. The isobaric thermal conductivity of RGS has been analysed within Debye approximation with regard to the effect of thermal expansion. The suggested model takes into consideration the fact that thermal conductivity is determined by U-processes while above the phonon mobility edge it is determined by "diffusive" modes migrating randomly from site to site. The mobility edge ω0 is determined from the condition that the phonon mean-free path restricted by the U-processes cannot be smaller than half of the phonon wavelength.
Czech Academy of Sciences Publication Activity Database
Krbal, M.; Wágner, T.; Frumar, M.; Vlček, Milan; Frumarová, Božena
2006-01-01
Roč. 47, č. 2 (2006), s. 193-197 ISSN 0031-9090. [Solid State Chemistry VI. Praha, 13.09.2004-17.09.2004] Institutional research plan: CEZ:AV0Z40500505 Keywords : diffusion and dissolution * As-S-Se films Subject RIV: CA - Inorganic Chemistry Impact factor: 0.577, year: 2006
An inverse diffusivity problem for the helium production–diffusion equation
International Nuclear Information System (INIS)
Bao, Gang; Xu, Xiang
2012-01-01
Thermochronology is a technique for the extraction of information about the thermal history of rocks. Such information is crucial for determining the depth below the surface at which rocks were located at a given time (Bao G et al 2011 Commun. Comput. Phys. 9 129). Mathematically, extracting the time–temperature path can be formulated as an inverse diffusivity problem for the helium production–diffusion equation which is the underlying process of thermochronology. In this paper, to reconstruct the diffusivity which depends on space only and accounts for the structural information of rocks, a local Hölder conditional stability is obtained by a Carleman estimate. A uniqueness result is also proven for extracting the thermal history, i.e. identifying the time-dependant part of the diffusion coefficient, provided that it is analytical with respect to time. Numerical examples are presented to illustrate the validity and effectiveness of the proposed regularization scheme. (paper)
Multicomponent diffusion in two-temperature magnetohydrodynamics
International Nuclear Information System (INIS)
Ramshaw, J.D.; Chang, C.H.
1996-01-01
A recent hydrodynamic theory of multicomponent diffusion in multitemperature gas mixtures [J. D. Ramshaw, J. Non-Equilib. Thermodyn. 18, 121 (1993)] is generalized to include the velocity-dependent Lorentz force on charged species in a magnetic field B. This generalization is used to extend a previous treatment of ambipolar diffusion in two-temperature multicomponent plasmas [J. D. Ramshaw and C. H. Chang, Plasma Chem. Plasma Process. 13, 489 (1993)] to situations in which B and the electrical current density are nonzero. General expressions are thereby derived for the species diffusion fluxes, including thermal diffusion, in both single- and two-temperature multicomponent magnetohydrodynamics (MHD). It is shown that the usual zero-field form of the Stefan-Maxwell equations can be preserved in the presence of B by introducing generalized binary diffusion tensors dependent on B. A self-consistent effective binary diffusion approximation is presented that provides explicit approximate expressions for the diffusion fluxes. Simplifications due to the small electron mass are exploited to obtain an ideal MHD description in which the electron diffusion coefficients drop out, resistive effects vanish, and the electric field reduces to a particularly simple form. This description should be well suited for numerical calculations. copyright 1996 The American Physical Society
Isotope Fractionation by Diffusion in Liquids (Final Technical Report)
Energy Technology Data Exchange (ETDEWEB)
Richter, Frank [Univ. of Chicago, IL (United States)
2016-11-09
The overall objective of the DOE-funded research by grant DE-FG02-01ER15254 was document and quantify kinetic isotope fractionations during chemical and thermal (i.e., Soret) diffusion in liquids (silicate melts and water) and in the later years to include alloys and major minerals such as olivine and pyroxene. The research involved both laboratory experiments and applications to natural settings. The key idea is that major element zoning on natural geologic materials is common and can arise for either changes in melt composition during cooling and crystallization or from diffusion. The isotope effects associated with diffusion that we have documented are the key for determining whether or not the zoning observed in a natural system was the result of diffusion. Only in those cases were the zoning is demonstrably due to diffusion can use independently measured rates of diffusion to constrain the thermal evolution of the system.
Determination of oxygen diffusion kinetics during thin film ruthenium oxidation
Coloma Ribera, R.; van de Kruijs, Robbert Wilhelmus Elisabeth; Yakshin, Andrey; Bijkerk, Frederik
2015-01-01
In situ X-ray reflectivity was used to reveal oxygen diffusion kinetics for thermal oxidation of polycrystalline ruthenium thin films and accurate determination of activation energies for this process. Diffusion rates in nanometer thin RuO2 films were found to show Arrhenius behaviour. However, a
Gas-induced friction and diffusion of rigid rotors
Martinetz, Lukas; Hornberger, Klaus; Stickler, Benjamin A.
2018-05-01
We derive the Boltzmann equation for the rotranslational dynamics of an arbitrary convex rigid body in a rarefied gas. It yields as a limiting case the Fokker-Planck equation accounting for friction, diffusion, and nonconservative drift forces and torques. We provide the rotranslational friction and diffusion tensors for specular and diffuse reflection off particles with spherical, cylindrical, and cuboidal shape, and show that the theory describes thermalization, photophoresis, and the inverse Magnus effect in the free molecular regime.
Spin-diffusions and diffusive molecular dynamics
Farmer, Brittan; Luskin, Mitchell; Plecháč, Petr; Simpson, Gideon
2017-12-01
Metastable configurations in condensed matter typically fluctuate about local energy minima at the femtosecond time scale before transitioning between local minima after nanoseconds or microseconds. This vast scale separation limits the applicability of classical molecular dynamics (MD) methods and has spurned the development of a host of approximate algorithms. One recently proposed method is diffusive MD which aims at integrating a system of ordinary differential equations describing the likelihood of occupancy by one of two species, in the case of a binary alloy, while quasistatically evolving the locations of the atoms. While diffusive MD has shown itself to be efficient and provide agreement with observations, it is fundamentally a model, with unclear connections to classical MD. In this work, we formulate a spin-diffusion stochastic process and show how it can be connected to diffusive MD. The spin-diffusion model couples a classical overdamped Langevin equation to a kinetic Monte Carlo model for exchange amongst the species of a binary alloy. Under suitable assumptions and approximations, spin-diffusion can be shown to lead to diffusive MD type models. The key assumptions and approximations include a well-defined time scale separation, a choice of spin-exchange rates, a low temperature approximation, and a mean field type approximation. We derive several models from different assumptions and show their relationship to diffusive MD. Differences and similarities amongst the models are explored in a simple test problem.
Helium diffusion in nickel at high temperatures
International Nuclear Information System (INIS)
Philipps, V.
1980-09-01
Helium has been implanted at certain temperatures between 800 and 1250 0 C into single and polycrystalline Ni-samples with implantation depths between 15 and 90 μm. Simultaneously the helium reemission from the sample is measured by a mass-spectrometer. It has been shown that the time dependence of the observed reemission rate is governed by volume diffusion of the helium. Measuring this time dependence as a function of temperature the helium diffusion constant has been determined. The He-diffusion is interpreted as a interstitial diffusion hindered by thermal vacancies. Depending on the implantation depth more or less of the implanted helium remains in the sample and forms large helium bubbles. (orig./GSCH)
SNAP - a three dimensional neutron diffusion code
International Nuclear Information System (INIS)
McCallien, C.W.J.
1993-02-01
This report describes a one- two- three-dimensional multi-group diffusion code, SNAP, which is primarily intended for neutron diffusion calculations but can also carry out gamma calculations if the diffusion approximation is accurate enough. It is suitable for fast and thermal reactor core calculations and for shield calculations. SNAP can solve the multi-group neutron diffusion equations using finite difference methods. The one-dimensional slab, cylindrical and spherical geometries and the two-dimensional case are all treated as simple special cases of three-dimensional geometries. Numerous reflective and periodic symmetry options are available and may be used to reduce the number of mesh points necessary to represent the system. Extrapolation lengths can be specified at internal and external boundaries. (Author)
Diffusion in reactor materials
International Nuclear Information System (INIS)
Fedorov, G.B.; Smirnov, E.A.
1984-01-01
The monograph contains a brief description of the principles underlying the theory of diffusion, as well as modern methods of studying diffusion. Data on self-diffusion and diffusion of impurities in a nuclear fuel and fissionable materials (uranium, plutonium, thorium, zirconium, titanium, hafnium, niobium, molybdenum, tungsten, beryllium, etc.) is presented. Anomalous diffusion, diffusion of components, and interdiffusion in binary and ternary alloys were examined. The monograph presents the most recent reference material on diffusion. It is intended for a wide range of researchers working in the field of diffusion in metals and alloys and attempting to discover new materials for application in nuclear engineering. It will also be useful for teachers, research scholars and students of physical metallurgy
Thermal Properties of G-348 Graphite
Energy Technology Data Exchange (ETDEWEB)
McEligot, Donald M. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Swank, W. David [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cottle, David L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Valentin, Francisco I. [City Univ. (CUNY), NY (United States)
2017-04-01
Fundamental measurements have been obtained in the INL Graphite Characterization Laboratory to deduce the temperature dependence of thermal conductivity for G-348 isotropic graphite, which has been used by City College of New York in thermal experiments related to gas-cooled nuclear reactors. Measurements of thermal diffusivity, mass, volume and thermal expansion were converted to thermal conductivity in accordance with ASTM Standard Practice C781-08 (R-2014). Data are tabulated and a preliminary correlation for the thermal conductivity is presented as a function of temperature from laboratory temperature to 1000C.
Fire suppression as a thermal implosion
Novozhilov, Vasily
2017-01-01
The present paper discusses the possibility of the thermal implosion scenario. This process would be a reverse of the well known thermal explosion (autoignition) phenomenon. The mechanism for thermal implosion scenario is proposed which involves quick suppression of the turbulent diffusion flame. Classical concept of the thermal explosion is discussed first. Then a possible scenario for the reverse process (thermal implosion) is discussed and illustrated by a relevant mathematical model. Based on the arguments presented in the paper, thermal implosion may be observed as an unstable equilibrium point on the generalized Semenov diagram for turbulent flame, however this hypothesis requires ultimate experimental confirmation.
Transient thermal camouflage and heat signature control
Yang, Tian-Zhi; Su, Yishu; Xu, Weikai; Yang, Xiao-Dong
2016-09-01
Thermal metamaterials have been proposed to manipulate heat flux as a new way to cloak or camouflage objects in the infrared world. To date, however, thermal metamaterials only operate in the steady-state and exhibit detectable, transient heat signatures. In this letter, the theoretical basis for a thermal camouflaging technique with controlled transient diffusion is presented. This technique renders an object invisible in real time. More importantly, the thermal camouflaging device instantaneously generates a pre-designed heat signature and behaves as a perfect thermal illusion device. A metamaterial coating with homogeneous and isotropic thermal conductivity, density, and volumetric heat capacity was fabricated and very good camouflaging performance was achieved.
International Nuclear Information System (INIS)
Reus, K.W.
1979-01-01
This thesis is concerned with the back-diffusion method of calculating the mutual diffusion coefficient of two gases. The applicability of this method for measuring diffusion coefficients at temperatures up to 1300 K is considered. A further aim of the work was to make a contribution to the description of the interatomic potential energy of noble gases at higher energies as a function of the internuclear distance. This was achieved with the measured diffusion coefficients, especially with those for high temperatures. (Auth.)
Diffusion Under Geometrical Constraint
Ogawa, Naohisa
2014-01-01
Here we discus the diffusion of particles in a curved tube. This kind of transport phenomenon is observed in biological cells and porous media. To solve such a problem, we discuss the three dimensional diffusion equation with a confining wall forming a thinner tube. We find that the curvature appears in a effective diffusion coefficient for such a quasi-one-dimensional system. As an application to higher dimensional case, we discuss the diffusion in a curved surface with ...
Diffuse charge dynamics in ionic thermoelectrochemical systems
Stout, Robert F.; Khair, Aditya S.
2017-08-01
Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1 /D κ2 , where D is the Brownian diffusion coefficient of both ion species, and κ-1 is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L2/D , where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion
Diffuse charge dynamics in ionic thermoelectrochemical systems.
Stout, Robert F; Khair, Aditya S
2017-08-01
Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1/Dκ^{2}, where D is the Brownian diffusion coefficient of both ion species, and κ^{-1} is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L^{2}/D, where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion
DEFF Research Database (Denmark)
Zhang, Chen
Diffuse ceiling ventilation is an innovative ventilation concept where the suspended ceiling serves as air diffuser to supply fresh air into the room. Compared with conventional ventilation systems, diffuse ceiling ventilation can significantly reduce or even eliminate draught risk due to the low...
An application of gold diffusion for defect investigation in silicon
International Nuclear Information System (INIS)
Feklisova, O.V.; Yakimov, E.B.
2009-01-01
The application of gold diffusion for defect investigation in Si is illustrated by the diffusion experiments carried out on crystals containing grown-in or specially introduced defects. The efficiency of gold diffusion experiments for monitoring the concentration and spatial distribution of these defects is shown. The effect of vacancy type defects on gold diffusion is illustrated by investigations of nitrogen-doped FZ Si and of Cz Si after rapid thermal annealing. In both these cases the gold depth profile is distinctive for trap limited diffusion. The effect of sinks for self-interstitials on gold diffusion is illustrated by the results obtained on the plastically deformed Si. It is shown that in silicon deformed at relatively low temperatures the gold diffusion is to a great extent determined by the defects in the dislocation trails while in high temperature deformed Si the sinks for self-interstitials are associated with dislocations themselves.
Determination of thermal conductivity of magnesium-alloys
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
An indirect method, Angstroms method was adopted and an instrument was designed to determine the thermal conductivity of magnesium metal and alloys. Angstroms method is an axial periodic heat flow technique by which the thermal diffusivity can be measured directly. Then thermal conductivity can be obtained with relation to thermal diffusivity. Compared with the recommended data from the literature the fitted values of the thermal diffiusivity correspond with 3%, and the credible probability of the thermal conductivity in the range of 0-450 ℃ is about 95%. The method is applicable in the given temperature range.
Fractional diffusion equations and anomalous diffusion
Evangelista, Luiz Roberto
2018-01-01
Anomalous diffusion has been detected in a wide variety of scenarios, from fractal media, systems with memory, transport processes in porous media, to fluctuations of financial markets, tumour growth, and complex fluids. Providing a contemporary treatment of this process, this book examines the recent literature on anomalous diffusion and covers a rich class of problems in which surface effects are important, offering detailed mathematical tools of usual and fractional calculus for a wide audience of scientists and graduate students in physics, mathematics, chemistry and engineering. Including the basic mathematical tools needed to understand the rules for operating with the fractional derivatives and fractional differential equations, this self-contained text presents the possibility of using fractional diffusion equations with anomalous diffusion phenomena to propose powerful mathematical models for a large variety of fundamental and practical problems in a fast-growing field of research.
Microclimatic control in the museum environment: Air diffusion performance
Energy Technology Data Exchange (ETDEWEB)
Ascione, Fabrizio; Minichiello, Francesco [DETEC, University of Naples Federico II, P.le Tecchio 80, 80125 Naples, NA (Italy)
2010-06-15
For the conservation of cultural heritage, museums need appropriate HVAC systems. Besides the time stability of the microclimatic parameters in the exhibition rooms, a high spatial uniformity is necessary and, thus, an optimal performance of the air diffusion systems. Using numerical codes based on Building Energy Performance Simulation (BEPS) and Computational Fluid Dynamics (CFD) techniques, in this paper an analysis has been carried out to compare different suitable air diffusion equipments, as regards uniformity of thermal-hygrometric and kinetic fields in a modelled typical exhibition room. For various part load conditions, the values of thermal-hygrometric parameters in different volumes of the room have been evaluated, as well as an innovative spatial thermal-hygrometric performance index. Globally estimating indoor temperature, relative humidity and their uniformity, for high exhibition rooms (5 m) the swirling diffusers have shown the best average performances, followed by the perimetrical stripes of slot diffusers, while for very high rooms (9 m) nozzles have resulted preferable. (author)
Determination of oxygen diffusion kinetics during thin film ruthenium oxidation
Energy Technology Data Exchange (ETDEWEB)
Coloma Ribera, R., E-mail: r.colomaribera@utwente.nl; Kruijs, R. W. E. van de; Yakshin, A. E.; Bijkerk, F. [MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)
2015-08-07
In situ X-ray reflectivity was used to reveal oxygen diffusion kinetics for thermal oxidation of polycrystalline ruthenium thin films and accurate determination of activation energies for this process. Diffusion rates in nanometer thin RuO{sub 2} films were found to show Arrhenius behaviour. However, a gradual decrease in diffusion rates was observed with oxide growth, with the activation energy increasing from about 2.1 to 2.4 eV. Further exploration of the Arrhenius pre-exponential factor for diffusion process revealed that oxidation of polycrystalline ruthenium joins the class of materials that obey the Meyer-Neldel rule.
Effective diffusion of confined active Brownian swimmers
Sandoval, Mario; Dagdug, Leonardo
2014-11-01
We find theoretically the effect of confinement and thermal fluctuations, on the diffusivity of a spherical active swimmer moving inside a two-dimensional narrow cavity of general shape. The explicit formulas for the effective diffusion coefficient of a swimmer moving inside two particular cavities are presented. We also compare our analytical results with Brownian Dynamics simulations and we obtain excellent agreement. L.D. thanks Consejo Nacional de Ciencia y Tecnologia (CONACyT) Mexico, for partial support by Grant No. 176452. M. S. thanks CONACyT and Programa de Mejoramiento de Profesorado (PROMEP) for partially funding this work under Grant No. 103.5/13/6732.
Diffusion and evaporation of a liquid droplet
Shukla, K. N.
1980-06-01
The process of evaporation and diffusion of a spherical liquid droplet in an atmosphere of noncondensable gas is studied theoretically. An equation for the shrinkage of the radius of the droplet is derived on the basis of continuity and momentum equations. Further, a conjugate problem consisting of the energy and mass balance for the gaseous environment is formulated. An approximation of thin thermal and diffusion boundary-layers is introduced to simplify the analysis. Results are presented for methanol-nitrogen, ammonia-nitrogen, and sodium-argon systems. It has been observed that the droplet of highly viscous fluid exhibits rapid contraction.
Energy Technology Data Exchange (ETDEWEB)
Park, Kyung Bae; Chung, Jae Hun; Hwang, Gwang Seok; Jung, Eui Han; Kwon, Oh Myoung [Korea University, Seoul (Korea, Republic of)
2014-12-15
We present a method to quantitatively measure the thermal conductivity of one-dimensional nanostructures by utilizing scanning thermal wave microscopy (STWM) at a nanoscale spatial resolution. In this paper, we explain the principle for measuring the thermal diffusivity of one-dimensional nanostructures using STWM and the theoretical analysis procedure for quantifying the thermal diffusivity. The SWTM measurement method obtains the thermal conductivity by measuring the thermal diffusivity, which has only a phase lag relative to the distance corresponding to the transferred thermal wave. It is not affected by the thermal contact resistances between the heat source and nanostructure and between the nanostructure and probe. Thus, the heat flux applied to the nanostructure is accurately obtained. The proposed method provides a very simple and quantitative measurement relative to conventional measurement techniques.
Preisach hysteresis model for non-linear 2D heat diffusion
International Nuclear Information System (INIS)
Jancskar, Ildiko; Ivanyi, Amalia
2006-01-01
This paper analyzes a non-linear heat diffusion process when the thermal diffusivity behaviour is a hysteretic function of the temperature. Modelling this temperature dependence, the discrete Preisach algorithm as general hysteresis model has been integrated into a non-linear multigrid solver. The hysteretic diffusion shows a heating-cooling asymmetry in character. The presented type of hysteresis speeds up the thermal processes in the modelled systems by a very interesting non-linear way
Metric diffusion along foliations
Walczak, Szymon M
2017-01-01
Up-to-date research in metric diffusion along compact foliations is presented in this book. Beginning with fundamentals from the optimal transportation theory and the theory of foliations; this book moves on to cover Wasserstein distance, Kantorovich Duality Theorem, and the metrization of the weak topology by the Wasserstein distance. Metric diffusion is defined, the topology of the metric space is studied and the limits of diffused metrics along compact foliations are discussed. Essentials on foliations, holonomy, heat diffusion, and compact foliations are detailed and vital technical lemmas are proved to aide understanding. Graduate students and researchers in geometry, topology and dynamics of foliations and laminations will find this supplement useful as it presents facts about the metric diffusion along non-compact foliation and provides a full description of the limit for metrics diffused along foliation with at least one compact leaf on the two dimensions.
CSIR Research Space (South Africa)
Osburn, L
2010-01-01
Full Text Available Thermal comfort is influenced by environmental parameters as well as other influences including asymmetric heating and cooling conditions. Additionally, some aspects of thermal comfort may be exploited so as to enable a building to operate within a...
International Nuclear Information System (INIS)
Wong, Alexander; Glaister, Jeffrey; Cameron, Andrew; Haider, Masoom
2013-01-01
Prostate cancer is one of the leading causes of cancer death in the male population. Fortunately, the prognosis is excellent if detected at an early stage. Hence, the detection and localization of prostate cancer is crucial for diagnosis, as well as treatment via targeted focal therapy. New imaging techniques can potentially be invaluable tools for improving prostate cancer detection and localization. In this study, we introduce a new form of diffusion magnetic resonance imaging called correlated diffusion imaging, where the tissue being imaged is characterized by the joint correlation of diffusion signal attenuation across multiple gradient pulse strengths and timings. By taking into account signal attenuation at different water diffusion motion sensitivities, correlated diffusion imaging can provide improved delineation between cancerous tissue and healthy tissue when compared to existing diffusion imaging modalities. Quantitative evaluation using receiver operating characteristic (ROC) curve analysis, tissue class separability analysis, and visual assessment by an expert radiologist were performed to study correlated diffusion imaging for the task of prostate cancer diagnosis. These results are compared with that obtained using T2-weighted imaging and standard diffusion imaging (via the apparent diffusion coefficient (ADC)). Experimental results suggest that correlated diffusion imaging provide improved delineation between healthy and cancerous tissue and may have potential as a diagnostic tool for cancer detection and localization in the prostate gland. A new form of diffusion magnetic resonance imaging called correlated diffusion imaging (CDI) was developed for the purpose of aiding radiologists in cancer detection and localization in the prostate gland. Preliminary results show CDI shows considerable promise as a diagnostic aid for radiologists in the detection and localization of prostate cancer
International Nuclear Information System (INIS)
Garrett, G.A.; Shacter, J.
1978-01-01
A gaseous diffusion system is described comprising a plurality of diffusers connected in cascade to form a series of stages, each of the diffusers having a porous partition dividing it into a high pressure chamber and a low pressure chamber, and means for combining a portion of the enriched gas from a succeeding stage with a portion of the enriched gas from the low pressure chamber of each stage and feeding it into one extremity of the high pressure chamber thereof
Inpainting using airy diffusion
Lorduy Hernandez, Sara
2015-09-01
One inpainting procedure based on Airy diffusion is proposed, implemented via Maple and applied to some digital images. Airy diffusion is a partial differential equation with spatial derivatives of third order in contrast with the usual diffusion with spatial derivatives of second order. Airy diffusion generates the Airy semigroup in terms of the Airy functions which can be rewritten in terms of Bessel functions. The Airy diffusion can be used to smooth an image with the corresponding noise elimination via convolution. Also the Airy diffusion can be used to erase objects from an image. We build an algorithm using the Maple package ImageTools and such algorithm is tested using some images. Our results using Airy diffusion are compared with the similar results using standard diffusion. We observe that Airy diffusion generates powerful filters for image processing which could be incorporated in the usual packages for image processing such as ImageJ and Photoshop. Also is interesting to consider the possibility to incorporate the Airy filters as applications for smartphones and smart-glasses.
Diffusion in compacted betonite
International Nuclear Information System (INIS)
Muurinen, A.; Rantanen, J.
1985-01-01
The objective of this report is to collect the literature bearing on the diffusion in compacted betonite, which has been suggested as possible buffer material for the disposal of spent fuel. Diffusion in a porous, water-saturated material is usually described as diffusion in the pore-water where sorption on the solid matter can delay the migration in the instationary state. There are also models which take into consideration that the sorbed molecules can also move while being sorbed. Diffusion experiments in compacted bentonite have been reported by many authors. Gases, anions, cations and actinides have been used as diffusing molecules. The report collects the results and the information on the measurement methods. On the basis of the results can be concluded that different particles possibly follow different diffusion mechanisms. The parameters which affect the diffusion seem to be for example the size, the electric charge and the sorption properties of the diffusing molecule. The report also suggest the parameters to be used in the diffusion calculation of the safety analyses of spent fuel disposal. (author)
Diffusion Based Photon Mapping
DEFF Research Database (Denmark)
Schjøth, Lars; Fogh Olsen, Ole; Sporring, Jon
2007-01-01
. To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination features......, while eliminating noise. We call our method diffusion based photon mapping....
Diffusion Based Photon Mapping
DEFF Research Database (Denmark)
Schjøth, Lars; Olsen, Ole Fogh; Sporring, Jon
2006-01-01
. To address this problem we introduce a novel photon mapping algorithm based on nonlinear anisotropic diffusion. Our algorithm adapts according to the structure of the photon map such that smoothing occurs along edges and structures and not across. In this way we preserve the important illumination features......, while eliminating noise. We call our method diffusion based photon mapping....
Adaptation and Cultural Diffusion.
Ormrod, Richard K.
1992-01-01
Explores the role of adaptation in cultural diffusion. Explains that adaptation theory recognizes the lack of independence between innovations and their environmental settings. Discusses testing and selection, modification, motivation, and cognition. Suggests that adaptation effects are pervasive in cultural diffusion but require a broader, more…
Modelling of Innovation Diffusion
Directory of Open Access Journals (Sweden)
Arkadiusz Kijek
2010-01-01
Full Text Available Since the publication of the Bass model in 1969, research on the modelling of the diffusion of innovation resulted in a vast body of scientific literature consisting of articles, books, and studies of real-world applications of this model. The main objective of the diffusion model is to describe a pattern of spread of innovation among potential adopters in terms of a mathematical function of time. This paper assesses the state-of-the-art in mathematical models of innovation diffusion and procedures for estimating their parameters. Moreover, theoretical issues related to the models presented are supplemented with empirical research. The purpose of the research is to explore the extent to which the diffusion of broadband Internet users in 29 OECD countries can be adequately described by three diffusion models, i.e. the Bass model, logistic model and dynamic model. The results of this research are ambiguous and do not indicate which model best describes the diffusion pattern of broadband Internet users but in terms of the results presented, in most cases the dynamic model is inappropriate for describing the diffusion pattern. Issues related to the further development of innovation diffusion models are discussed and some recommendations are given. (original abstract
Directory of Open Access Journals (Sweden)
Matthew A. Brodsky
2012-08-01
Full Text Available Background: It is generally agreed that diffusion of botulinum toxin occurs, but the extent of the spread and its clinical importance are disputed. Many factors have been suggested to play a role but which have the most clinical relevance is a subject of much discussion.Methods: This review discusses the variables affecting diffusion, including protein composition and molecular size as well as injection factors (e.g., volume, dose, injection method. It also discusses data on diffusion from comparative studies in animal models and human clinical trials that illustrate differences between the available botulinum toxin products (onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, and rimabotulinumtoxinB.Results: Neither molecular weight nor the presence of complexing proteins appears to affect diffusion; however, injection volume, concentration, and dose all play roles and are modifiable. Both animal and human studies show that botulinum toxin products are not interchangeable, and that some products are associated with greater diffusion and higher rates of diffusion-related adverse events than others.Discussion: Each of the botulinum toxins is a unique pharmacologic entity. A working knowledge of the different serotypes is essential to avoid unwanted diffusion-related adverse events. In addition, clinicians should be aware that the factors influencing diffusion may range from properties intrinsic to the drug to accurate muscle selection as well as dilution, volume, and dose injected.
Review on mathematical basis for thermal conduction equation
Energy Technology Data Exchange (ETDEWEB)
Park, D. G.; Kim, H. M
2007-10-15
In the view point of thermal conductivity measurement technology, It is very useful to understand mathematical theory of thermal conduction equation in order to evaluation of measurement data and to solve diverse technical problem in measurement. To approach this mathematical theory, thermal conduction equation is derived by Fourier thermal conduction law. Since thermal conduction equation depends on the Lapacian operator basically, mathematical meaning of Lapalacian and various diffusion equation including Laplacian have been studied. Stum-Liouville problem and Bessel function were studied in this report to understand analytical solution of various diffusion equation.
Review on mathematical basis for thermal conduction equation
International Nuclear Information System (INIS)
Park, D. G.; Kim, H. M.
2007-10-01
In the view point of thermal conductivity measurement technology, It is very useful to understand mathematical theory of thermal conduction equation in order to evaluation of measurement data and to solve diverse technical problem in measurement. To approach this mathematical theory, thermal conduction equation is derived by Fourier thermal conduction law. Since thermal conduction equation depends on the Lapacian operator basically, mathematical meaning of Lapalacian and various diffusion equation including Laplacian have been studied. Stum-Liouville problem and Bessel function were studied in this report to understand analytical solution of various diffusion equation
Efficient thermal diode with ballistic spacer
Chen, Shunda; Donadio, Davide; Benenti, Giuliano; Casati, Giulio
2018-03-01
Thermal rectification is of importance not only for fundamental physics, but also for potential applications in thermal manipulations and thermal management. However, thermal rectification effect usually decays rapidly with system size. Here, we show that a mass-graded system, with two diffusive leads separated by a ballistic spacer, can exhibit large thermal rectification effect, with the rectification factor independent of system size. The underlying mechanism is explained in terms of the effective size-independent thermal gradient and the match or mismatch of the phonon bands. We also show the robustness of the thermal diode upon variation of the model's parameters. Our finding suggests a promising way for designing realistic efficient thermal diodes.
Diffusion in Coulomb crystals.
Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K
2011-07-01
Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.
Michaud, Georges; Richer, Jacques
2015-01-01
This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling. In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...
Degenerate nonlinear diffusion equations
Favini, Angelo
2012-01-01
The aim of these notes is to include in a uniform presentation style several topics related to the theory of degenerate nonlinear diffusion equations, treated in the mathematical framework of evolution equations with multivalued m-accretive operators in Hilbert spaces. The problems concern nonlinear parabolic equations involving two cases of degeneracy. More precisely, one case is due to the vanishing of the time derivative coefficient and the other is provided by the vanishing of the diffusion coefficient on subsets of positive measure of the domain. From the mathematical point of view the results presented in these notes can be considered as general results in the theory of degenerate nonlinear diffusion equations. However, this work does not seek to present an exhaustive study of degenerate diffusion equations, but rather to emphasize some rigorous and efficient techniques for approaching various problems involving degenerate nonlinear diffusion equations, such as well-posedness, periodic solutions, asympt...
Development of irradiated UO2 thermal conductivity model
International Nuclear Information System (INIS)
Lee, Chan Bock; Bang Je-Geon; Kim Dae Ho; Jung Youn Ho
2001-01-01
Thermal conductivity model of the irradiated UO 2 pellet was developed, based upon the thermal diffusivity data of the irradiated UO 2 pellet measured during thermal cycling. The model predicts the thermal conductivity by multiplying such separate correction factors as solid fission products, gaseous fission products, radiation damage and porosity. The developed model was validated by comparison with the variation of the measured thermal diffusivity data during thermal cycling and prediction of other UO 2 thermal conductivity models. Since the developed model considers the effect of gaseous fission products as a separate factor, it can predict variation of thermal conductivity in the rim region of high burnup UO 2 pellet where the fission gases in the matrix are precipitated into bubbles, indicating that decrease of thermal conductivity by bubble precipitation in rim region would be significantly compensated by the enhancing effect of fission gas depletion in the UO 2 matrix. (author)
Cherniak, D. J.; Zhang, X. Y.; Nakamura, M.; Watson, E. B.
2004-09-01
We report measurements of oxygen diffusion in natural monazites under both dry, 1-atm conditions and hydrothermal conditions. For dry experiments, 18O-enriched CePO4 powder and monazite crystals were sealed in Ag-Pd capsules with a solid buffer (to buffer at NNO) and annealed in 1-atm furnaces. Hydrothermal runs were conducted in cold-seal pressure vessels, where monazite grains were encapsulated with 18O-enriched water. Following the diffusion anneals, oxygen concentration profiles were measured with Nuclear Reaction Analysis (NRA) using the reaction 18O(p,α)15N. Over the temperature range 850-1100 °C, the Arrhenius relation determined for dry diffusion experiments on monazite is given by: Under wet conditions at 100 MPa water pressure, over the temperature range 700-880 °C, oxygen diffusion can be described by the Arrhenius relationship: Oxygen diffusion under hydrothermal conditions has a significantly lower activation energy for diffusion than under dry conditions, as has been found the case for many other minerals, both silicate and nonsilicate. Given these differences in activation energies, the differences between dry and wet diffusion rates increase with lower temperatures; for example, at 600 °C, dry diffusion will be more than 4 orders of magnitude slower than diffusion under hydrothermal conditions. These disparate diffusivities will result in pronounced differences in the degree of retentivity of oxygen isotope signatures. For instance, under dry conditions (presumably rare in the crust) and high lower-crustal temperatures (∼800 °C), monazite cores of 70-μm radii will preserve O isotope ratios for about 500,000 years; by comparison, they would be retained at this temperature under wet conditions for about 15,000 years.
OH+ IN DIFFUSE MOLECULAR CLOUDS
International Nuclear Information System (INIS)
Porras, A. J.; Federman, S. R.; Welty, D. E.; Ritchey, A. M.
2014-01-01
Near ultraviolet observations of OH + and OH in diffuse molecular clouds reveal a preference for different environments. The dominant absorption feature in OH + arises from a main component seen in CH + (that with the highest CH + /CH column density ratio), while OH follows CN absorption. This distinction provides new constraints on OH chemistry in these clouds. Since CH + detections favor low-density gas with small fractions of molecular hydrogen, this must be true for OH + as well, confirming OH + and H 2 O + observations with the Herschel Space Telescope. Our observed correspondence indicates that the cosmic ray ionization rate derived from these measurements pertains to mainly atomic gas. The association of OH absorption with gas rich in CN is attributed to the need for a high enough density and molecular fraction before detectable amounts are seen. Thus, while OH + leads to OH production, chemical arguments suggest that their abundances are controlled by different sets of conditions and that they coexist with different sets of observed species. Of particular note is that non-thermal chemistry appears to play a limited role in the synthesis of OH in diffuse molecular clouds
International Nuclear Information System (INIS)
Aspden, G.J.; Howard, R.S.
1988-01-01
The patent concerns high temperature thermal insulation of large vessels, such as the primary vessel of a liquid metal cooled nuclear reactor. The thermal insulation consists of multilayered thermal insulation modules, and each module comprises a number of metal sheet layers sandwiched between a back and front plate. The layers are linked together by straps and clips to control the thickness of the module. (U.K.)
Thermal properties of nonstoichiometry uranium dioxide
Kavazauri, R.; Pokrovskiy, S. A.; Baranov, V. G.; Tenishev, A. V.
2016-04-01
In this paper, was developed a method of oxidation pure uranium dioxide to a predetermined deviation from the stoichiometry. Oxidation was carried out using the thermogravimetric method on NETZSCH STA 409 CD with a solid electrolyte galvanic cell for controlling the oxygen potential of the environment. 4 samples uranium oxide were obtained with a different ratio of oxygen-to-metal: O / U = 2.002, O / U = 2.005, O / U = 2.015, O / U = 2.033. For the obtained samples were determined basic thermal characteristics of the heat capacity, thermal diffusivity, thermal conductivity. The error of heat capacity determination is equal to 5%. Thermal diffusivity and thermal conductivity of the samples decreased with increasing deviation from stoichiometry. For the sample with O / M = 2.033, difference of both values with those of stoichiometric uranium dioxide is close to 50%.
Results on positron diffusion in Si
International Nuclear Information System (INIS)
Nielsen, B.; Lynn, K.G.; Vehanen, A.; Schultz, P.J.
1984-10-01
Positron diffusion in Si(100) and Si(111) has been measured using a variable energy positron beam. The diffusion related parameter, E 0 is found to be 4.2 +- 0.2 keV, significantly longer than previously reported values. The positron diffusion coefficient is estimated at D/sub +/ = 2.3 +- 0.4 cm 2 /sec, the uncertainty arising mainly from the characteristics of the assumed positron implantation profile. A drastic reduction in E 0 is found after heating the sample to 1300 0 K, showing that previously reported low values of E 0 are associated with the thermal history of the sample. A high sensitivity to defects introduced by low energy ion bombardment is found, and the defect recovery was followed during heat treatments. Reconstruction of the Si(111) surface into the so-called 7 x 7 structure had no detectable influence on the positron diffusion behavior. No changes in the positron diffusion was observed after covering the surface with atomic hydrogen. However the yield of positronium formation at the surface was enhanced, attributed to an increased density of states at the surface
International Nuclear Information System (INIS)
Black, J.H.
1987-01-01
The author defines and discusses the nature of diffuse interstellar clouds. He discusses how they contribute to the general extinction of starlight. The atomic and molecular species that have been identified in the ultraviolet, visible, and near infrared regions of the spectrum of a diffuse cloud are presented. The author illustrates some of the practical considerations that affect absorption line observations of interstellar atoms and molecules. Various aspects of the theoretical description of diffuse clouds required for a full interpretation of the observations are discussed
Infrared diffuse interstellar bands
Galazutdinov, G. A.; Lee, Jae-Joon; Han, Inwoo; Lee, Byeong-Cheol; Valyavin, G.; Krełowski, J.
2017-05-01
We present high-resolution (R ˜ 45 000) profiles of 14 diffuse interstellar bands in the ˜1.45 to ˜2.45 μm range based on spectra obtained with the Immersion Grating INfrared Spectrograph at the McDonald Observatory. The revised list of diffuse bands with accurately estimated rest wavelengths includes six new features. The diffuse band at 15 268.2 Å demonstrates a very symmetric profile shape and thus can serve as a reference for finding the 'interstellar correction' to the rest wavelength frame in the H range, which suffers from a lack of known atomic/molecular lines.
International Nuclear Information System (INIS)
Mundy, J.N.; Rothman, S.J.; Lam, N.Q.; Nowicki, L.J.; Hoff, H.A.
1978-01-01
The lack of understanding of self-diffusion in Group VI metals together with the wide scatter in the measured values of tungsten self-diffusion has prompted the present measurements to be made over a wide temperature range (1/2Tsub(m) to Tsub(m)). The diffusion coefficients have been measured in the temperature range 1430-2630 0 C. The present measurements show non-linear Arrhenius behavior but a reliable two-exponential fit of the data should await further measurements. (Auth.)
Diffusion of zinc into an unpassivated surface of indium phosphide
International Nuclear Information System (INIS)
Budko, T.O.; Gushchinskaya, E.V.; Emelyanenko, Yu.S.; Malyshev, S.A.
1989-01-01
Peculiarities are studied of the diffusion of Zn into an unpassivated surface of InP in an open gasflow system. In the region where the carrier concentration profile is described by an erfc (error function compliment), the diffusion coefficient and activation energy are determined. It is shown that thermal processes cause changes in the charge state of Zn in InP which result in a variation of the carrier profile in the semiconductor. (author)