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Sample records for electrically-conducting forced convection

  1. Lorentz force sigmometry: a novel technique for measuring the electrical conductivity of solid and liquid metals

    NASA Astrophysics Data System (ADS)

    Alkhalil, Shatha; Kolesnikov, Yurii; Thess, André

    2015-11-01

    In this paper, a novel method to measure the electrical conductivity of solid and molten metals is described. We term the method ‘Lorentz force sigmometry’, where the term ‘sigmometry’ refers to the letter sigma σ, often used to denote the electrical conductivity. The Lorentz force sigmometry method is based on the phenomenon of eddy currents generation in a moving conductor exposed to a magnetic field. Based on Ampere’s law, the eddy currents in turn generate a secondary magnetic field; as a result, the Lorentz force acts to brake the conductor. Owing to Newton’s third law, a measurable force, which is equal to the Lorentz force and is directly proportional to the electrical conductivity of the conductive fluid or solid, acts on the magnet. We present the results of the measurements performed on solids along with the initial measurements on fluids with a eutectic alloy composition of Ga67In20.5Sn12.5; detailed measurements on molten metals are still in progress and will be published in the future. We conducted a series of experiments and measured the properties of known electrical conductive metals, including aluminum and copper, to compute the calibration factor of the device, and then used the same calibration factor to estimate the unknown electrical conductivity of a brass bar. The predicted electrical conductivity of the brass bar was compared with the conductivity measured with a commercial device called ‘SigmaTest’ the observed error was less than 0.5%.

  2. Electro-Convective and Non-Equilibrium Electro-Osmotic Instability of Electric Conduction from an Electrolyte Solution into a Charge Selective Solid

    NASA Astrophysics Data System (ADS)

    Rubinstein, Isaak

    2006-03-01

    Electro-convection is reviewed as a mechanism of mixing in the diffusion layer of a strong electrolyte adjacent to a charge-selective solid, such as an ion exchange (electrodialysis) membrane or an electrode. Two types of electro-convection in strong electrolytes may be distinguished: bulk electro-convection , due to the action of the electric field upon the residual space charge of a quasi-electro-neutral bulk solution, and convection induced by electro-osmotic slip, due to electric forces acting in the thin electric double layer of either quasi-equilibrium or non-equilibrium type near the solid/liquid interface. According to recent studies, the latter appears to be the likely source of mixing in the diffusion layer, leading to `over-limiting' conductance in electrodialysis. Electro-convection near a uniform charge selective solid/liquid interface sets on as a result of hydrodynamic instability of one-dimensional steady state electric conduction through such an interface. We discuss instabilities of this kind appearing in the full electro-convective and limiting non-equilibrium electro-osmotic formulations. The short- and long-wave aspects of these instabilities are discussed along with the wave-number selection principles and possible sources of low frequency excess electric noise experimentally observed in these systems.

  3. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Allen, Philip B.

    1979-01-01

    Examines Drude's classical (1900) theory of electrical conduction, details the objections to and successes of the 1900 theory, and investigates the Quantum (1928) theory of conduction, reviewing its successes and limitations. (BT)

  4. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Hershey, David R.; Sand, Susan

    1993-01-01

    Explains how electrical conductivity (EC) can be used to measure ion concentration in solutions. Describes instrumentation for the measurement, temperature dependence and EC, and the EC of common substances. (PR)

  5. Vegetation forcing and convective motion

    SciTech Connect

    Hong, X.; Leach, M.J.; Raman, S.

    1995-04-01

    A large irrigated vegetation area in a semiarid or relatively dry location is a strong surface forcing of thermal circulations. Several observational studies have found that such thermally induced mesoscale circulation may contribute to the triggering and development of convective clouds. In the western United States, extensive areas of irrigated farmland are surrounded by hot, dry surfaces, such as a steppe. Substantial gradients of sensible heating in the horizontal direction lead to a {open_quotes}farm breeze{close_quotes} circulation from the cooler agricultural area to the warmer steppes found at Boardman, Oregon. These thermally forced circulations may trigger convection by the related convergence and updraft motion under favorable atmospheric conditions. The role of vegetative covering in convective motion is investigated using a mesoscale numerical model. Two- and three-dimensional simulations are described. The effects of atmospheric stability, moisture in the lower atmosphere, moisture in the upper atmosphere, and horizontal heating scale on thermally induced clouds are studied. The horizontal scale of inhomogeneity is also studied using the two-dimensional model. Finally, a realistic vegetation distribution similar to that of the Boardman Regional Flux Experiment is used in the three-dimensional simulations.

  6. Electrical conductivity in Langmuir-Blodgett films of n-alkyl cyanobiphenyls using current sensing atomic force microscope

    SciTech Connect

    Gayathri, H. N.; Suresh, K. A.

    2015-06-28

    We report our studies on the nanoscale electrical conductivity in monolayers of n-alkyl cyanobiphenyl materials deposited on solid surface. Initially, the 8CB, 9CB, and 10CB monolayer films were prepared by the Langmuir technique at air-water interface and characterized by surface manometry and Brewster angle microscopy. The monolayer films were transferred on to solid substrates by the Langmuir-Blodgett (L-B) technique. The 8CB, 9CB, and 10CB monolayer L-B films were deposited on freshly cleaved mica and studied by atomic force microscope (AFM), thereby measuring the film thickness as ∼1.5 nm. The electrical conductivity measurements were carried out on 9CB and 10CB monolayer L-B films deposited onto highly ordered pyrolytic graphite using current sensing AFM. The nanoscale current-voltage (I-V) measurements show a non-linear variation. The nature of the curve indicates electron tunneling to be the mechanism for electrical conduction. Furthermore, analysis of the I-V curve reveals a transition in the electron conduction mechanism from direct tunneling to injection tunneling. From the transition voltage, we have estimated the values of barrier height for 9CB and 10CB to be 0.71 eV and 0.37 eV, respectively. For both 9CB and 10CB, the effective mass of electron was calculated to be 0.021 m{sub e} and 0.065 m{sub e}, respectively. These parameters are important in the design of molecular electronic devices.

  7. The electrical conduction of conjugated molecular CAMs studied by a conductive atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shin-ichi; Ogawa, Kazufumi

    2006-09-01

    Monomolecular layers containing pyrrolyl groups between two parallel Pt electrodes on a glass substrate by a chemical adsorption technique using N-[11-(trichlorosilyl)undecyl] pyrrole (PNN) were studied. Polymerization with pure water by applying a DC voltage of 10 V between the two Pt electrodes was carried out, and several electric paths were formed between the two Pt electrodes were identified. Conductive probe of an atomic force microscopy (AFM) was used to examine the electrical polymerized paths through the surface of the polypyrrolyl group in a chemically adsorbed monomolecular layer. With a measurement volume of about 0.2 nm (thickness of the monomolecular layer) × 100 μm (the average width of an electric path) × 100 μm (the distance between the Pt electrode and the Au-covered AFM tip), the resistance at room temperature of one electric path was 5 kΩ under ambient conditions. From the results conducted in an atmosphere, the conductivity of a super-long conjugated polypyrrolyl group without any dopant in a lateral direction was ohmically estimated to be at least 5.0 × 10 5 s/m.

  8. Subcooled forced convection boiling of trichlorotrifluoroethane

    NASA Technical Reports Server (NTRS)

    Dougall, R. S.; Panian, D. J.

    1972-01-01

    Experimental heat-transfer data were obtained for the forced-convection boiling of trichlorotrifluoroethane (R-113 or Freon-113) in a vertical annular test annular test section. The 97 data points obtained covered heat transfer by forced convection, local boiling, and fully-developed boiling. Correlating methods were obtained which accurately predicted the heat flux as a function of wall superheat (boiling curve) over the range of parameters studied.

  9. Supercritical droplet gasification experiments with forced convection

    NASA Technical Reports Server (NTRS)

    Litchford, Ron; Parigger, Chris; Jeng, San-Mou

    1992-01-01

    Preliminary results of a comprehensive experimental program are presented which offer the first direct observations of suspended n-heptane droplet gasifications in pure nitrogen with forced convection without the interference to optical probing associated with a flame. Measurements show attainment of a wet-bulb temperature until reduced pressures exceed about 1.0 under supercritical gas temperatures. Thereafter, temperature measurements indicate fully transient heat-up through the critical temperature. The surface is found to regress in a continuous manner with the measured temperature approaching the critical value at the end of the droplet lifetime under supercritical conditions with very mild level of convection. At increased level of convection for the same ambient conditions, similar sized droplets will undergo significant deformation during the gasification process until partially convected away as a dense vapor cloud as the critical temperature is approached.

  10. Forced Convection Heat Transfer in Circular Pipes

    ERIC Educational Resources Information Center

    Tosun, Ismail

    2007-01-01

    One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…

  11. Magnetospheric Convection as a Global Force Phenomenon

    NASA Astrophysics Data System (ADS)

    Siscoe, G.

    2007-12-01

    Since 1959 when Thomas Gold showed that motions in the magnetosphere were possible despite plasma being frozen to the magnetic field, magnetospheric convection as a subject of study has gone through several stages (to be reviewed) leading to a recent one that integrates convection into a global system of balance of forces. This area of research has opened by focusing on the region 1 current system as a carrier of force between the solar wind and the ionosphere/thermosphere fluid. An important result to emerge from it is the realization that the force that the solar wind delivers to the magnetosphere in being transferred by the region 1 current system to the ionosphere/thermosphere fluid is amplified by about an order of magnitude. (Vasyliunas refers to this as "leveraging.") The apparent violation of Newton's Third Law results from the main participants in the force balance being not the solar wind force but the JxB force on the ionosphere/thermosphere fluid and the mu-dot-grad-B force on the Earth's dipole. This talk extends the study by considering the global force-balance problem separately for the Pedersen current (a completion of the region 1 problem), the Hall current (thus introducing the region 2 current system), and the Cowling current (bringing in the substorm current wedge). The approach is through representing the ionosphere/thermosphere fluid by the shallow water equations. Novelties that result include force balance by means of tidal bulges and tidal bores.

  12. Electrically conductive cellulose composite

    DOEpatents

    Evans, Barbara R.; O'Neill, Hugh M.; Woodward, Jonathan

    2010-05-04

    An electrically conductive cellulose composite includes a cellulose matrix and an electrically conductive carbonaceous material incorporated into the cellulose matrix. The electrical conductivity of the cellulose composite is at least 10 .mu.S/cm at 25.degree. C. The composite can be made by incorporating the electrically conductive carbonaceous material into a culture medium with a cellulose-producing organism, such as Gluconoacetobacter hansenii. The composites can be used to form electrodes, such as for use in membrane electrode assemblies for fuel cells.

  13. Electrically conductive diamond electrodes

    DOEpatents

    Swain, Greg; Fischer, Anne ,; Bennett, Jason; Lowe, Michael

    2009-05-19

    An electrically conductive diamond electrode and process for preparation thereof is described. The electrode comprises diamond particles coated with electrically conductive doped diamond preferably by chemical vapor deposition which are held together with a binder. The electrodes are useful for oxidation reduction in gas, such as hydrogen generation by electrolysis.

  14. Forced convection modulates gas exchange in cnidarians

    PubMed Central

    Patterson, Mark R.; Sebens, Kenneth P.

    1989-01-01

    Boundary layer thickness is a potentially important component of the diffusive pathway for gas exchange in aquatic organisms. The soft coral Alcyonium siderium (Octocorallia) and sea anemone Metridium senile (Actiniaria) exhibit significant increases in respiration with water flow over a range of Reynolds numbers encountered subtidally. A nondimensional mass transfer analysis of the effect of forced convection demonstrates the importance of the state of the organism's boundary layer in regulating metabolism in these invertebrates. Flow-modulated gas exchange may limit secondary productivity in subtidal environments. PMID:16594087

  15. Electrically conductive material

    DOEpatents

    Singh, J.P.; Bosak, A.L.; McPheeters, C.C.; Dees, D.W.

    1993-09-07

    An electrically conductive material is described for use in solid oxide fuel cells, electrochemical sensors for combustion exhaust, and various other applications possesses increased fracture toughness over available materials, while affording the same electrical conductivity. One embodiment of the sintered electrically conductive material consists essentially of cubic ZrO[sub 2] as a matrix and 6-19 wt. % monoclinic ZrO[sub 2] formed from particles having an average size equal to or greater than about 0.23 microns. Another embodiment of the electrically conductive material consists essentially at cubic ZrO[sub 2] as a matrix and 10-30 wt. % partially stabilized zirconia (PSZ) formed from particles having an average size of approximately 3 microns. 8 figures.

  16. Electrically conductive material

    DOEpatents

    Singh, Jitendra P.; Bosak, Andrea L.; McPheeters, Charles C.; Dees, Dennis W.

    1993-01-01

    An electrically conductive material for use in solid oxide fuel cells, electrochemical sensors for combustion exhaust, and various other applications possesses increased fracture toughness over available materials, while affording the same electrical conductivity. One embodiment of the sintered electrically conductive material consists essentially of cubic ZrO.sub.2 as a matrix and 6-19 wt. % monoclinic ZrO.sub.2 formed from particles having an average size equal to or greater than about 0.23 microns. Another embodiment of the electrically conductive material consists essentially at cubic ZrO.sub.2 as a matrix and 10-30 wt. % partially stabilized zirconia (PSZ) formed from particles having an average size of approximately 3 microns.

  17. Performance of thermal adhesives in forced convection

    NASA Technical Reports Server (NTRS)

    Kundu, Nikhil K.

    1993-01-01

    Cooling is critical for the life and performance of electronic equipment. In most cases cooling may be achieved by natural convection but forced convection may be necessary for high wattage applications. Use of conventional type heat sinks may not be feasible from the viewpoint of specific applications and the costs involved. In a heat sink, fins can be attached to the well by ultrasonic welding, by soldering, or with a number of industrially available thermal adhesives. In this paper, the author investigates the heat transfer characteristics of several adhesives and compares them with ultrasonic welding and theoretically calculated values. This experiment was conducted in an air flow chamber. Heat was generated by using heaters mounted on the well. Thermstrate foil, Uniset A401, and Aremco 571 adhesives were tested along with an ultrasonically welded sample. Ultrasonic welding performed far better than the adhesives and Thermstrate foil. This type of experiment can be adapted for a laboratory exercise in an upper level heat transfer course. It gives students an exposure to industrial applications that help them appreciate the importance of the course material.

  18. Electrically conductive composite material

    DOEpatents

    Clough, Roger L.; Sylwester, Alan P.

    1989-01-01

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

  19. Electrically conductive composite material

    DOEpatents

    Clough, R.L.; Sylwester, A.P.

    1988-06-20

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

  20. Natural and forced convection during solidification

    NASA Astrophysics Data System (ADS)

    Neufeld, Jerome A.

    The following work marries theoretical and experimental approaches to study the interaction of an external shear flow with a solidifying porous medium. The porous medium, a dendritic 'mushy layer', is created when a super-eutectic binary alloy is cooled leading to solid crystals bathed in an interstitial fluid which is compositionally enriched. This compositional enrichment leads to natural buoyant instabilities in the solidifying porous medium coupled with instabilities in the adjoining liquid layer. Theoretically, the effect of an external shear flow on the convective instabilities inherent to this mushy layer is investigated using a linear stability analysis. The external flow is coupled to advective perturbations in the liquid and to flow in the mush through a perturbed mush-liquid interface. A complete numerical solution of the stability of the system is performed and a critical porous medium Rayleigh number is found which is a function of both the external flow speed and the wavenumber of the interfacial perturbations. By neglecting the effects of buoyancy in the liquid and solving only for the pressure perturbations on the corrugated mush-liquid interface induced by the external flow, a reduced model is constructed and solved analytically. These theoretical results are compared with experimental observations obtained in a laboratory flume in which an ammonium-chloride solution is solidified from below at a constant rate. The experimental results reveal that at flow speeds above critical, convection is forced within the mush leading to a series of zero solid fraction tesselations aligned perpendicular to the applied shear flow. The results of the experiments compare favorably to the linear stability analysis.

  1. Forced-convective vitrification with liquid cryogens.

    PubMed

    Lyu, Shaw-Ruey; Huang, Jen-Hung; Shih, Wei-Hung; Chen, Yung-Jiun; Hsieh, Wen-Hsin

    2013-06-01

    Cell cryopreservation by vitrification generally requires using vitrification solutions with high concentrations of cryoprotectants (CPAs), which are toxic and induce osmotic stresses associated with the addition and removal of CPAs. To increase the cooling rate and reduce the CPA concentration required for vitrification, this study proposed an innovative approach, named forced-convective vitrification with liquid cryogens, in which liquid oxygen at a temperature below its boiling point (LOX(bbp)) was used as the cryogen to reduce the generation of insulating bubbles of gaseous oxygen and the sample was subjected to a constant velocity to remove insulation bubbles from the sample. Results show that changing the cryogen from liquid nitrogen at its boiling temperature (LN(abp)) to LOX(bbp), increasing the sample velocity and reducing the test solution volume increased the cooling rate and thereby decreased the CPA concentration required for vitrification. Using the same velocity (1.2 m/s), the cooling rate achieved with LOX(bbp) was 2.3-fold greater than that achieved with LN(abp). With LOX(bbp), the increase in the sample velocity from 0.2 to 1.2 m/s enhanced the cooling rate by 1.9 times. With LOX(bbp), a velocity of 1.2m/s and a test solution volume of 1.73 μl, the CPA concentration required for vitrification decreased to 25%. These results indicate that the new approach described here can reduce the CPA concentration required for vitrification, and thus decreases the toxicity and osmotic stresses associated with adding and removing the CPA. PMID:23545291

  2. Electrical Conductivity in Textiles

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Copper is the most widely used electrical conductor. Like most metals, though, it has several drawbacks: it is heavy, expensive, and can break. Fibers that conduct electricity could be the solutions to these problems, and they are of great interest to NASA. Conductive fibers provide lightweight alternatives to heavy copper wiring in a variety of settings, including aerospace, where weight is always a chief concern. This is an area where NASA is always seeking improved materials. The fibers are also more cost-effective than metals. Expenditure is another area where NASA is always looking to make improvements. In the case of electronics that are confined to small spaces and subject to severe stress, copper is prone to breaking and losing connection over time. Flexible conductive fibers eliminate that problem. They are more supple and stronger than brittle copper and, thus, find good use in these and similar situations. While clearly a much-needed material, electrically conductive fibers are not readily available. The cost of new technology development, with all the pitfalls of troubleshooting production and the years of testing, and without the guarantee of an immediate market, is often too much of a financial hazard for companies to risk. NASA, however, saw the need for electrical fibers in its many projects and sought out a high-tech textile company that was already experimenting in this field, Syscom Technology, Inc., of Columbus, Ohio. Syscom was founded in 1993 to provide computer software engineering services and basic materials research in the areas of high-performance polymer fibers and films. In 1999, Syscom decided to focus its business and technical efforts on development of high-strength, high-performance, and electrically conductive polymer fibers. The company developed AmberStrand, an electrically conductive, low-weight, strong-yet-flexible hybrid metal-polymer YARN.

  3. Electrically Conductive Porous Membrane

    NASA Technical Reports Server (NTRS)

    Burke, Kenneth Alan (Inventor)

    2014-01-01

    The present invention relates to an electrically conductive membrane that can be configured to be used in fuel cell systems to act as a hydrophilic water separator internal to the fuel cell, or as a water separator used with water vapor fed electrolysis cells, or as a water separator used with water vapor fed electrolysis cells, or as a capillary structure in a thin head pipe evaporator, or as a hydrophobic gas diffusion layer covering the fuel cell electrode surface in a fuel cell.

  4. Driving forces: Slab subduction and mantle convection

    NASA Technical Reports Server (NTRS)

    Hager, Bradford H.

    1988-01-01

    Mantle convection is the mechanism ultimately responsible for most geological activity at Earth's surface. To zeroth order, the lithosphere is the cold outer thermal boundary layer of the convecting mantle. Subduction of cold dense lithosphere provides tha major source of negative buoyancy driving mantle convection and, hence, surface tectonics. There are, however, importnat differences between plate tectonics and the more familiar convecting systems observed in the laboratory. Most important, the temperature dependence of the effective viscosity of mantle rocks makes the thermal boundary layer mechanically strong, leading to nearly rigid plates. This strength stabilizes the cold boundary layer against small amplitude perturbations and allows it to store substantial gravitational potential energy. Paradoxically, through going faults at subduction zones make the lithosphere there locally weak, allowing rapid convergence, unlike what is observed in laboratory experiments using fluids with temperature dependent viscosities. This bimodal strength distribution of the lithosphere distinguishes plate tectonics from simple convection experiments. In addition, Earth has a buoyant, relatively weak layer (the crust) occupying the upper part of the thermal boundary layer. Phase changes lead to extra sources of heat and bouyancy. These phenomena lead to observed richness of behavior of the plate tectonic style of mantle convection.

  5. Electrically conductive alternating copolymers

    DOEpatents

    Aldissi, M.; Jorgensen, B.S.

    1987-08-31

    Polymers which are soluble in common organic solvents and are electrically conductive, but which also may be synthesized in such a manner that they become nonconductive. Negative ions from the electrolyte used in the electrochemical synthesis of a polymer are incorporated into the polymer during the synthesis and serve as a dopant. A further electrochemical step may be utilized to cause the polymer to be conductive. The monomer repeat unit is comprised of two rings, a pyrrole molecule joined to a thienyl group, or a furyl group, or a phenyl group. The individual groups of the polymers are arranged in an alternating manner. For example, the backbone arrangement of poly(furylpyrrole) is -furan-pyrrole-furan-pyrrole- furan-pyrrole. An alkyl group or phenyl group may be substituted for either or both of the hydrogen atoms of the pyrrole ring.

  6. Parabolic flight experiment "Convection in a Cylinder" - Convection patterns in varying buoyancy forces

    NASA Astrophysics Data System (ADS)

    Dahley, N.; Futterer, B.; Egbers, C.; Crumeyrolle, O.; Mutabazi, I.

    2011-12-01

    Within the project "Convection in a Cylinder" (CiC) heat transfer enhancement is studied for the case of two concentric, vertically aligned cylinders. The cylindrical gap is filled with a dielectric liquid, which viscosity is just few times higher than that of water. The inner cylinder is heated and the outer one is cooled. This setup in a gravitational buoyancy field leads to a fluid movement in a single convective cell with hot fluid rising at the inner boundary and cold fluid sinking at the outer boundary. The top and bottom part of the system shows horizontal movement, again in boundary layers. The strengthening of temperature gradient induces instabilities of that convective motion. If we vary the buoyancy force by means of electro-hydrodynamic effects, the patterns of convection differ from those instabilities rising only from variation of the temperature gradient.

  7. Electrically conductive anodized aluminum coatings

    NASA Technical Reports Server (NTRS)

    Alwitt, Robert S. (Inventor); Liu, Yanming (Inventor)

    2001-01-01

    A process for producing anodized aluminum with enhanced electrical conductivity, comprising anodic oxidation of aluminum alloy substrate, electrolytic deposition of a small amount of metal into the pores of the anodized aluminum, and electrolytic anodic deposition of an electrically conductive oxide, including manganese dioxide, into the pores containing the metal deposit; and the product produced by the process.

  8. A study of forced convection boiling under reduced gravity

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1992-01-01

    This report presents the results of activities conducted over the period 1/2/85-12/31/90, in which the study of forced convection boiling under reduced gravity was initiated. The study seeks to improve the understanding of the basic processes that constitute forced convection boiling by removing the buoyancy effects which may mask other phenomena. Specific objectives may also be expressed in terms of the following questions: (1) what effects, if any, will the removal of body forces to the lowest possible levels have on the forced convection boiling heat transfer processes in well-defined and meaningful circumstances? (this includes those effects and processes associated with the nucleation or onset of boiling during the transient increase in heater surface temperature, as well as the heat transfer and vapor bubble behaviors with established or steady-state conditions); and (2) if such effects are present, what are the boundaries of the relevant parameters such as heat flux, heater surface superheat, fluid velocity, bulk subcooling, and geometric/orientation relationships within which such effects will be produced?

  9. Forced convection heat transfer to air/water vapor mixtures

    NASA Technical Reports Server (NTRS)

    Richards, D. R.; Florschuetz, L. W.

    1984-01-01

    Heat transfer coefficients were measured using both dry and humid air in the same forced convection cooling scheme and were compared using appropriate nondimensional parameters (Nusselt, Prandtl and Reynolds numbers). A forced convection scheme with a complex flow field, two dimensional arrays of circular jets with crossflow, was utilized with humidity ratios (mass ratio of water vapor to air) up to 0.23. The dynamic viscosity, thermal conductivity and specific heat of air, steam and air/steam mixtures are examined. Methods for determining gaseous mixture properties from the properties of their pure components are reviewed as well as methods for determining these properties with good confidence. The need for more experimentally determined property data for humid air is discussed. It is concluded that dimensionless forms of forced convection heat transfer data and empirical correlations based on measurements with dry air may be applied to conditions involving humid air with the same confidence as for the dry air case itself, provided that the thermophysical properties of the humid air mixtures are known with the same confidence as their dry air counterparts.

  10. Electrically Conductive Paints for Satellites

    NASA Technical Reports Server (NTRS)

    Gilligan, J. E.; Wolf, R. E.; Ray, C.

    1977-01-01

    A program was conducted to develop and test electrically conductive paint coatings for spacecraft. A wide variety of organic and inorganic coatings were formulated using conductive binders, conductive pigments, and similar approaches. Z-93, IITRI's standard specification inorganic thermal control coating, exhibits good electrical properties and is a very space-stable coating system. Several coatings based on a conductive pigment (antimony-doped tin oxide) in silicone and silicate binders offer considerable promise. Paint systems using commercially available conductive polymers also appear to be of interest, but will require substantial development. Evaluations were made based on electrical conductivity, paint physical properties, and the stability of spectral reflectance in space environment testing.

  11. Combined forced and free convection in a curved duct

    NASA Technical Reports Server (NTRS)

    Yam, Clement G.; Dwyer, Harry A.

    1992-01-01

    The purpose of this study is to investigate the flow and heat transfer characteristics of a combined forced and free convection flow in a curved duct. Solutions are obtained by solving the low Mach number model of the Navier-Stokes equation using a control volume method. The finite-volume method was developed with the use of a predictor-corrector numerical scheme and some new variations of the classical projection method. Solutions indicated that the existence of a buoyancy force has changed the entire flow structure inside a curved duct. Reversed flow at both inner and outer bend is observed. For moderate Reynolds number, the upstream section of the duct was significantly influenced by the free convection processes. In general, heat transfer is strong at the inner bend of the beginning of the heated section and at the outer bend on the last half of the heated section. The maximum velocity location is strongly influenced by the combined effects of buoyancy and centrifugal forces. A strong buoyancy force can reduce the strength of the secondary flow where it plays an important role in mixing.

  12. Evaluation of T-111 forced-convection loop tested with lithium at 1370 C. [free convection

    NASA Technical Reports Server (NTRS)

    Devan, J. H.; Long, E. L., Jr.

    1975-01-01

    A T-111 alloy (Ta-8% W-2% Hf) forced-convection loop containing molten lithium was operated 3000 hr at a maximum temperature of 1370 C. Flow velocities up to 6.3 m/sec were used, and the results of this forced-convection loop are very similar to those observed in lower velocity thermal-convection loops of T-111 containing lithium. Weight changes were determined at 93 positions around the loop. The maximum dissolution rate occurred at the maximum wall temperature of the loop and was less than 1.3 microns/year. Mass transfer of hafnium, nitrogen, and, to a lesser extent, carbon occurred from the hotter to cooler regions. Exposed surfaces in the highest temperature region were found to be depleted in hafnium to a depth of 60 microns with no detectable change in tungsten content. There was some loss in room-temperature tensile strength for specimens exposed to lithium at 1370 C, attributable to depletion of hafnium and nitrogen and to attendant grain growth.

  13. Electrical Conductivity in Transition Metals

    ERIC Educational Resources Information Center

    Talbot, Christopher; Vickneson, Kishanda

    2013-01-01

    The aim of this "Science Note" is to describe how to test the electron-sea model to determine whether it accurately predicts relative electrical conductivity for first-row transition metals. In the electron-sea model, a metal crystal is viewed as a three-dimensional array of metal cations immersed in a sea of delocalised valence…

  14. Electrically conductive rigid polyurethane foam

    DOEpatents

    Neet, Thomas E.; Spieker, David A.

    1985-03-19

    A rigid, polyurethane foam comprises about 2-10 weight percent, based on the total foam weight, of a carbon black which is CONDUCTEX CC-40-220 or CONDUCTEX SC, whereby the rigid polyurethane foam is electrically conductive and has essentially the same mechanical properties as the same foam without carbon black added.

  15. Electrically conductive rigid polyurethane foam

    DOEpatents

    Neet, T.E.; Spieker, D.A.

    1983-12-08

    A rigid, moldable polyurethane foam comprises about 2 to 10 weight percent, based on the total foam weight, of a carbon black which is CONDUCTEX CC-40-220 or CONDUCTEX SC, whereby the rigid polyurethane foam is electrically conductive and has essentially the same mechanical properties as the same foam without carbon black added.

  16. Electrically Conductive Anodized Aluminum Surfaces

    NASA Technical Reports Server (NTRS)

    Nguyen, Trung Hung

    2006-01-01

    Anodized aluminum components can be treated to make them sufficiently electrically conductive to suppress discharges of static electricity. The treatment was conceived as a means of preventing static electric discharges on exterior satin-anodized aluminum (SAA) surfaces of spacecraft without adversely affecting the thermal-control/optical properties of the SAA and without need to apply electrically conductive paints, which eventually peel off in the harsh environment of outer space. The treatment can also be used to impart electrical conductivity to anodized housings of computers, medical electronic instruments, telephoneexchange equipment, and other terrestrial electronic equipment vulnerable to electrostatic discharge. The electrical resistivity of a typical anodized aluminum surface layer lies between 10(exp 11) and 10(exp 13) Omega-cm. To suppress electrostatic discharge, it is necessary to reduce the electrical resistivity significantly - preferably to < or = 10(exp 9) Omega-cm. The present treatment does this. The treatment is a direct electrodeposition process in which the outer anodized surface becomes covered and the pores in the surface filled with a transparent, electrically conductive metal oxide nanocomposite. Filling the pores with the nanocomposite reduces the transverse electrical resistivity and, in the original intended outer-space application, the exterior covering portion of the nanocomposite would afford the requisite electrical contact with the outer-space plasma. The electrical resistivity of the nanocomposite can be tailored to a value between 10(exp 7) and 10(exp 12) Omega-cm. Unlike electrically conductive paint, the nanocomposite becomes an integral part of the anodized aluminum substrate, without need for adhesive bonding material and without risk of subsequent peeling. The electrodeposition process is compatible with commercial anodizing production lines. At present, the electronics industry uses expensive, exotic

  17. Lox droplet vaporization in a supercritical forced convective environment

    NASA Technical Reports Server (NTRS)

    Hsiao, Chia-Chun; Yang, Vigor

    1994-01-01

    A systematic investigation has been conducted to study the effects of ambient flow conditions (i.e. pressure and velocity) on supercritical droplet gasification in a forced-convective environment. The model is based on the time-dependent conservation equations in axisymmetric coordinates, and accommodates thermodynamic nonidealities and transport anomalies. In addition, an efficient scheme for evaluating thermophysical properties over the entire range of fluid thermodynamic states is established. The analysis allows a thorough examination of droplet behavior during its entire lifetime, including transient gasification, dynamic deformation, and shattering. A parametric study of droplet vaporization rate in terms of ambient pressure and Reynolds number is also conducted.

  18. Combined effects of a magnetic field and a helical force on the onset of a rotating Rayleigh-Bénard convection with free-free boundaries

    NASA Astrophysics Data System (ADS)

    Chabi Orou, Jean Bio; Pomalégni, Gisèle

    2015-11-01

    We investigate the combined effects of rotation , magnetic field and helical force on the onset of stationary and oscillatory convection in a horizontal electrically conducting fluid layer heated from below with free-free boundary conditions. For this investigation the linear stability analysis studied by Chandrasekhar (1961) is used. We obtain the condition for the formation of a single large scale structure. In (Pomalégni et al., 2014) it was shown the existence of a critical value Scr of the intensity of the helical force for which the apparition of two cells at marginal stability for the oscillatory convection is obtained. Then, we have shown here how the increasing of parameter Ta influences this critical value of the helical force intensity.

  19. Metallization and electrical conductivity of hydrogen in Jupiter.

    PubMed

    Nellis, W J; Weir, S T; Mitchell, A C

    1996-08-16

    Electrical conductivities of molecular hydrogen in Jupiter were calculated by scaling electrical conductivities measured at shock pressures in the range of 10 to 180 gigapascals (0.1 to 1.8 megabars) and temperatures to 4000 kelvin, representative of conditions inside Jupiter. Jupiter's magnetic field is caused by convective dynamo motion of electrically conducting fluid hydrogen. The data imply that Jupiter should become metallic at 140 gigapascals in the fluid, and the electrical conductivity in the jovian molecular envelope at pressures up to metallization is about an order of magnitude larger than expected previously. The large magnetic field is produced in the molecular envelope closer to the surface than previously thought. PMID:8688072

  20. Membrane species mobility under in-lipid-membrane forced convection.

    PubMed

    Hu, Shu-Kai; Huang, Ling-Ting; Chao, Ling

    2016-08-17

    Processing and managing cell membrane proteins for characterization while maintaining their intact structure is challenging. Hydrodynamic flow has been used to transport membrane species in supported lipid bilayers (SLBs) where the hydrophobic cores of the membrane species can be protected during processing. However, the forced convection mechanism of species embedded in lipid bilayers is still unclear. Developing a controlled SLB platform with a practical model to predict the membrane species mobility in the platform under in-lipid-membrane forced convection is imperative to ensure the practical applicability of SLBs in processing and managing membrane species with various geometrical properties. The mobility of membrane species is affected by the driving force from the aqueous environment in addition to the frictions from the lipid bilayer, in which both lipid leaflets may exhibit different speeds relative to that of the moving species. In this study, we developed a model, based on the applied driving force and the possible frictional resistances that the membrane species encounter, to predict how the mobility under in-lipid-membrane forced convection is influenced by the sizes of the species' hydrophilic portion in the aqueous environment and the hydrophobic portion embedded in the membrane. In addition, we used a microfluidic device for controlling the flow to arrange the lipid membrane and the tested membrane species in the desirable locations in order to obtain a SLB platform which can provide clear mobility responses of the species without disturbance from the species dispersion effect. The model predictions were consistent with the experimental observations, with the sliding friction coefficient between the upper leaflet and the hydrophilic portion of the species as the only regressed parameter. The result suggests that not only the lateral drag frictions from the lipid layers but also the sliding frictions between the species and the lipid layer planes

  1. Electrically conductive polymer concrete overlays

    NASA Astrophysics Data System (ADS)

    Fontana, J. J.; Webster, R. P.

    1984-08-01

    The use of cathodic protection to prevent the corrosion of reinforcing steel in concrete structures has been well established. Application of a durable, skid-resistant electrically conductive polymer concrete overlay would advance the use of cathodic protection for the highway industry. Laboratory studies indicate that electrically conductive polymer concrete overlays using conductive fillers, such as calcined coke breeze, in conjunction with polyester or vinyl ester resins have resistivities of 1 to 10 ohm-cm. Both multiple-layer and premixed mortar-type overlays were made. Shear bond strengths of the conductive overlays to concrete substrates vary from 600 to 1300 psi, with the premixed overlays having bond strengths 50 to 100% higher than the multiple-layer overlays.

  2. Electrically conductive polymer concrete coatings

    DOEpatents

    Fontana, J.J.; Elling, D.; Reams, W.

    1988-05-26

    A sprayable electrically conductive polymer concrete coating for vertical and overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt% calcined coke breeze, 40 wt% vinyl ester resin with 3.5 wt% modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag. 4 tabs.

  3. Electrically conductive polymer concrete coatings

    DOEpatents

    Fontana, J.J.; Elling, D.; Reams, W.

    1990-03-13

    A sprayable electrically conductive polymer concrete coating for vertical d overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt % calcined coke breeze, 40 wt % vinyl ester with 3.5 wt % modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag.

  4. Electrically conductive polymer concrete coatings

    DOEpatents

    Fontana, Jack J.; Elling, David; Reams, Walter

    1990-01-01

    A sprayable electrically conductive polymer concrete coating for vertical d overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt % calcined coke breeze, 40 wt % vinyl ester with 3.5 wt % modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag.

  5. Electrical conduction in polymer dielectrics

    NASA Technical Reports Server (NTRS)

    Cotts, D. B.

    1985-01-01

    The use of polymer dielectrics with moderate resistivities could reduce or eliminate problems associated with spacecraft charging. The processes responsible for conduction and the properties of electroactive polymers are reviewed, and correlations drawn between molecular structure and electrical conductivity. These structure-property relationships led to the development of several new electroactive polymer compositions and the identification of several systems that have the requisite thermal, mechanical, environmental and electrical properties for use in spacecraft.

  6. Numerical study of forced convective heat transfer around airships

    NASA Astrophysics Data System (ADS)

    Dai, Qiumin; Fang, Xiande

    2016-02-01

    Forced convective heat transfer is an important factor that affects the thermal characteristics of airships. In this paper, the steady state forced convective heat transfer around an ellipsoid is numerically investigated. The numerical simulation is carried out by commercial computational fluid dynamic (CFD) software over the extended Re range from 20 to 108 and the aspect ratio from 2 to 4. Based on the regression and optimization with software, a new piecewise correlation of the Nusselt number at constant wall temperature for ellipsoid is proposed, which is suitable for applications to airships and other ellipse shaped bodies such as elliptical balloons. The thermal characteristics of a stratospheric airship in midsummer located in the north hemisphere are numerical studied. The helium temperature predicated using the new correlation is compared to those predicted by correlations applicable for spheres and flat plates. The results show that the helium temperature obtained using the new correlation at noon is about 5.4 K lower than that using the correlation of spheres and about 2.1 K higher than that of flat plates.

  7. ARM - Midlatitude Continental Convective Clouds - Single Column Model Forcing (xie-scm_forcing)

    DOE Data Explorer

    Xie, Shaocheng; McCoy, Renata; Zhang, Yunyan

    2012-10-25

    The constrained variational objective analysis approach described in Zhang and Lin [1997] and Zhang et al. [2001]was used to derive the large-scale single-column/cloud resolving model forcing and evaluation data set from the observational data collected during Midlatitude Continental Convective Clouds Experiment (MC3E), which was conducted during April to June 2011 near the ARM Southern Great Plains (SGP) site. The analysis data cover the period from 00Z 22 April - 21Z 6 June 2011. The forcing data represent an average over the 3 different analysis domains centered at central facility with a diameter of 300 km (standard SGP forcing domain size), 150 km and 75 km, as shown in Figure 1. This is to support modeling studies on various-scale convective systems.

  8. Electrical conductivity of ice VII

    PubMed Central

    Okada, Taku; Iitaka, Toshiaki; Yagi, Takehiko; Aoki, Katsutoshi

    2014-01-01

    It was discovered that a peak appears near a pressure of Pc = 10 GPa in the electrical conductivity of ice VII as measured through impedance spectroscopy in a diamond anvil cell (DAC) during the process of compression from 2 GPa to 40 GPa at room temperature. The activation energy for the conductivity measured in the cooling/heating process between 278 K and 303 K reached a minimum near Pc. Theoretical modelling and molecular dynamics simulations suggest that the origin of this unique peak is the transition of the major charge carriers from the rotational defects to the ionic defects. PMID:25047728

  9. LOX droplet vaporization in a supercritical forced convective environment

    NASA Technical Reports Server (NTRS)

    Hsiao, Chia-Chun; Yang, Vigor

    1993-01-01

    Modern liquid rocket engines often use liquid oxygen (LOX) and liquid hydrogen (LH2) as propellants to achieve high performance, with the engine operational conditions in the supercritical regimes of the propellants. Once the propellant exceeds its critical state, it essentially becomes a puff of dense fluid. The entire field becomes a continuous medium, and no distinct interfacial boundary between the liquid and gas exists. Although several studies have been undertaken to investigate the supercritical droplet behavior at quiescent conditions, very little effort has been made to address the fundamental mechanisms associated with LOX droplet vaporization in a supercritical, forced convective environment. The purpose is to establish a theoretical framework within which supercritical droplet dynamics and vaporization can be studied systematically by means of an efficient and robust numerical algorithm.

  10. Boiling inception in trichlorotrifluoroethane during forced convection at high pressures

    NASA Technical Reports Server (NTRS)

    Dougall, R. S.; Lippert, T. E.

    1972-01-01

    The inception of bubbles during forced convection was studied experimentally by using trichlorotrifluoroethane (R-113 or Freon-113). The experiments were performed in a rectangular channel, 12.7 x 9.5 mm in cross section. Heating was from a 3.2 mm wide strip embedded in the longer side of the channel. The pressures studied ranged from 3.6 to 20.7 bar, mass velocities from 700 to 600 kg/sq m/sec, and inlet subcoolings from 26 to 97 C. Photographs of the flow were used to determine when bubbles first appeared on the heated surface. These data were compared with wall temperature measurements and inception theories. A reasonable method for calculating the complete boiling curve was found to agree with these results.

  11. Forced convection heat transfer to air/water vapor mixtures

    NASA Technical Reports Server (NTRS)

    Richards, D. R.; Florschuetz, L. W.

    1986-01-01

    Heat transfer coefficients were measured using both dry air and air/water vapor mixtures in the same forced convection cooling test rig (jet array impingement configurations) with mass ratios of water vapor to air up to 0.23. The primary objective was to verify by direct experiment that selected existing methods for evaluation of viscosity and thermal conductivity of air/water vapor mixtures could be used with confidence to predict heat transfer coefficients for such mixtures using as a basis heat transfer data for dry air only. The property evaluation methods deemed most appropriate require as a basis a measured property value at one mixture composition in addition to the property values for the pure components.

  12. Development of a mechanistic model for forced convection subcooled boiling

    NASA Astrophysics Data System (ADS)

    Shaver, Dillon R.

    The focus of this work is on the formulation, implementation, and testing of a mechanistic model of subcooled boiling. Subcooled boiling is the process of vapor generation on a heated wall when the bulk liquid temperature is still below saturation. This is part of a larger effort by the US DoE's CASL project to apply advanced computational tools to the simulation of light water reactors. To support this effort, the formulation of the dispersed field model is described and a complete model of interfacial forces is formulated. The model has been implemented in the NPHASE-CMFD computer code with a K-epsilon model of turbulence. The interfacial force models are built on extensive work by other authors, and include novel formulations of the turbulent dispersion and lift forces. The complete model of interfacial forces is compared to experiments for adiabatic bubbly flows, including both steady-state and unsteady conditions. The same model is then applied to a transient gas/liquid flow in a complex geometry of fuel channels in a sodium fast reactor. Building on the foundation of the interfacial force model, a mechanistic model of forced-convection subcooled boiling is proposed. This model uses the heat flux partitioning concept and accounts for condensation of bubbles attached to the wall. This allows the model to capture the enhanced heat transfer associated with boiling before the point of net generation of vapor, a phenomenon consistent with existing experimental observations. The model is compared to four different experiments encompassing flows of light water, heavy water, and R12 at different pressures, in cylindrical channels, an internally heated annulus, and a rectangular channel. The experimental data includes axial and radial profiles of both liquid temperature and vapor volume fraction, and the agreement can be considered quite good. The complete model is then applied to simulations of subcooled boiling in nuclear reactor subchannels consistent with the

  13. Forced Convection and Sedimentation Past a Flat Plate

    NASA Technical Reports Server (NTRS)

    Pelekasis, Nikolaos A.; Acrivos, Andreas

    1995-01-01

    The steady laminar flow of a well-mixed suspension of monodisperse solid spheres, convected steadily past a horizontal flat plate and sedimenting under the action of gravity, is examined. It is shown that, in the limit as Re approaches infinity and epsilon approaches 0, where Re is the bulk Reynolds number and epsilon is the ratio of the particle radius a to the characteristic length scale L, the analysis for determining the particle concentration profile has several aspects in common with that of obtaining the temperature profile in forced-convection heat transfer from a wall to a fluid stream moving at high Reynolds and Prandtl numbers. Specifically, it is found that the particle concentration remains uniform throughout the O(Re(exp -1/2)) thick Blasius boundary layer except for two O(epsilon(exp 2/3)) thin regions on either side of the plate, where the concentration profile becomes non-uniform owing to the presence of shear-induced particle diffusion which balances the particle flux due to convection and sedimentation. The system of equations within this concentration boundary layer admits a similarity solution near the leading edge of the plate, according to which the particle concentration along the top surface of the plate increases from its value in the free stream by an amount proportional to X(exp 5/6), with X measuring the distance along the plate, and decreases in a similar fashion along the underside. But, unlike the case of gravity settling on an inclined plate in the absence of a bulk flow at infinity considered earlier, here the concentration profile remains continuous everywhere. For values of X beyond the region near the leading edge, the particle concentration profile is obtained through the numerical solution of the relevant equations. It is found that, as predicted from the similarity solution, there exists a value of X at which the particle concentration along the top side of the plate attains its maximum value phi(sub m) and that, beyond this

  14. Computation of forced laminar convection in rotating cavities

    NASA Astrophysics Data System (ADS)

    Chew, J. W.

    1985-05-01

    Finite difference solutions are presented for forced laminar convection in a rotating cylindrical cavity with radial outflow. This forms a simple model of the cooling flow between two compressor disks in a gas turbine engine. If the fluid enters the cavity from a uniform radial source, it is shown that the local Nusselt number changes from that of a 'free disk' near the center of the cavity to that for Ekman layer flow at larger radii. With an axial inlet, the flow, and consequently, the heat transfer, is more complex. If vortex breakdown occurs, then the results are very similar to those for the radial inlet case, but otherwise a wall jet forms on the downstream disk, and the heat transfer from this disk may be several times that for the upstream disk. Variation of mean Nusselt number with rotational speed is qualitatively similar to previously published experimental measurements in turbulent flow. The effect of Prandtl number on heat transfer has also been demonstrated.

  15. Forced convective melting at an evolving ice-water interface

    NASA Astrophysics Data System (ADS)

    Ramudu, Eshwan; Hirsh, Benjamin; Olson, Peter; Gnanadesikan, Anand

    2015-11-01

    The intrusion of warm Circumpolar Deep Water into the ocean cavity between the base of ice shelves and the sea bed in Antarctica causes melting at the ice shelves' basal surface, producing a turbulent melt plume. We conduct a series of laboratory experiments to investigate how the presence of forced convection (turbulent mixing) changes the delivery of heat to the ice-water interface. We also develop a theoretical model for the heat balance of the system that can be used to predict the change in ice thickness with time. In cases of turbulent mixing, the heat balance includes a term for turbulent heat transfer that depends on the friction velocity and an empirical coefficient. We obtain a new value for this coefficient by comparing the modeled ice thickness against measurements from a set of nine experiments covering one order of magnitude of Reynolds numbers. Our results are consistent with the altimetry-inferred melting rate under Antarctic ice shelves and can be used in climate models to predict their disintegration. This work was supported by NSF grant EAR-110371.

  16. Electrically Conductive Metal Nanowire Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Luo, Xiaoxiong

    This thesis investigates electrically conductive polymer nanocomposites formulated with metal nanowires for electrostatic discharge and electromagnetic interference shielding. Copper nanowires (CuNWs) of an average length of 1.98 mum and diameter of 25 +/- 4 nm were synthesized. The oxidation reaction of the CuNWs in air can be divided into two stages at weight of 111.2% on TGA curves. The isoconversional activation energies determined by Starink method were used to fit the different master plots. Johnson-Mehl-Avrami (JMA) equation gave the best fit. The surface atoms of the CuNWs are the sites for the random nucleation and the crystallite strain in the CuNWs is the driving force for the growth of nuclei mechanism during the oxidation process. To improve the anti-oxidation properties of the CuNWs, silver was coated onto the surface of the CuNWs in Ag-amine solution. The prepared silver coated CuNWs (AgCuNWs) with silver content of 66.52 wt. %, diameter of 28--33 nm exhibited improved anti-oxidation behavior. The electrical resistivity of the AgCuNW/low density polyethylene (LDPE) nanocomposites is lower than that of the CuNW/LDPE nanocomposites with the same volume percentage of fillers. The nanocomposites formulated with CuNWs and polyethylenes (PEs) were compared to study the different interaction between the CuNWs and the different types of PE matrices. The electrical conductivity of the different PE matrices filled with the same concentrations of CuNWs correlated well with the level of the CuNW dispersion. The intermolecular force and entanglement resulting from the different macromolecular structures such as molecular weight and branching played an important role in the dispersion, electrical properties and rheological behaviour of the CuNW/PE nanocomposites. Ferromagnetic polycrystalline nickel nanowires (NiNWs) were synthesized with uniform diameter of ca. 38 nm and an average length of 2.68 mum. The NiNW linear low density polyethylene (LLDPE

  17. Electrically conducting ternary amorphous fully oxidized materials and their application

    NASA Technical Reports Server (NTRS)

    Giauque, Pierre (Inventor); Nicolet, Marc (Inventor); Gasser, Stefan M. (Inventor); Kolawa, Elzbieta A. (Inventor); Cherry, Hillary (Inventor)

    2004-01-01

    Electrically active devices are formed using a special conducting material of the form Tm--Ox mixed with SiO2 where the materials are immiscible. The immiscible materials are forced together by using high energy process to form an amorphous phase of the two materials. The amorphous combination of the two materials is electrically conducting but forms an effective barrier.

  18. Forced-convection boiling tests performed in parallel simulated LMR fuel assemblies

    SciTech Connect

    Rose, S.D.; Carbajo, J.J.; Levin, A.E.; Lloyd, D.B.; Montgomery, B.H.; Wantland, J.L.

    1985-04-21

    Forced-convection tests have been carried out using parallel simulated Liquid Metal Reactor fuel assemblies in an engineering-scale sodium loop, the Thermal-Hydraulic Out-of-Reactor Safety facility. The tests, performed under single- and two-phase conditions, have shown that for low forced-convection flow there is significant flow augmentation by thermal convection, an important phenomenon under degraded shutdown heat removal conditions in an LMR. The power and flows required for boiling and dryout to occur are much higher than decay heat levels. The experimental evidence supports analytical results that heat removal from an LMR is possible with a degraded shutdown heat removal system.

  19. Electrically conductive fibers thermally isolate temperature sensor

    NASA Technical Reports Server (NTRS)

    De Waard, R.; Norton, B.

    1966-01-01

    Mounting assembly provides thermal isolation and an electrical path for an unbacked thermal sensor. The sensor is suspended in the center of a plastic mounting ring from four plastic fibers, two of which are coated with an electrically conductive material and connected to electrically conductive coatings on the ring.

  20. Preparation of Electrically Conductive Polymeric Membranes

    NASA Astrophysics Data System (ADS)

    Encinas, J. C.; Castillo-Ortega, M. M.; Rodríguez, F.; Castaño, V. M.

    2015-10-01

    Cellulose acetate porous membranes, coated with polyaniline, were chemically modified with polyelectrolytes to produce films of varying and controlled porosity and electrical conductivity. The highest electrical conductivity was obtained in membranes prepared with poly(styrene sulfonate) with large pore sizes. The electrical properties as well as scanning electron microscopy (SEM) images are discussed.

  1. System and method for determining velocity of electrically conductive fluid

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A. (Inventor); Korman, Valentin (Inventor); Markusic, Thomas E. (Inventor); Stanojev, Boris Johann (Inventor)

    2008-01-01

    A flowing electrically-conductive fluid is controlled between an upstream and downstream location thereof to insure that a convection timescale of the flowing fluid is less than a thermal diffusion timescale of the flowing fluid. First and second nodes of a current-carrying circuit are coupled to the fluid at the upstream location. A current pulse is applied to the current-carrying circuit so that the current pulse travels through the flowing fluid to thereby generate a thermal feature therein at the upstream location. The thermal feature is convected to the downstream location where it is monitored to detect a peak associated with the thermal feature so-convected. The velocity of the fluid flow is determined using a time-of-flight analysis.

  2. A Study of Nucleate Boiling with Forced Convection in Microgravity

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1999-01-01

    The ultimate objective of basic studies of flow boiling in microgravity is to improve the understanding of the processes involved, as manifested by the ability to predict its behavior. This is not yet the case for boiling heat transfer even in earth gravity, despite the considerable research activity over the past 30 years. The elements that constitute the nucleate boiling process - nucleation, growth, motion, and collapse of the vapor bubbles (if the bulk liquid is subcooled) - are common to both pool and flow boiling. It is well known that the imposition of bulk liquid motion affects the vapor bubble behavior relative to pool boiling, but does not appear to significantly influence the heat transfer. Indeed, it has been recommended in the past that empirical correlations or experimental data of pool boiling be used for design purposes with forced convection nucleate boiling. It is anticipated that such will most certainly not be possible for boiling in microgravity, based on observations made with pool boiling in microgravity. In earth gravity buoyancy will act to remove the vapor bubbles from the vicinity of the heater surface regardless of how much the imposed bulk velocity is reduced, depending, of course, on the geometry of the system. Vapor bubbles have been observed to dramatically increase in size in pool boiling in microgravity, and the heat flux at which dryout took place was reduced considerably below what is generally termed the critical heat flux (CHF) in earth gravity, depending on the bulk liquid subcooling. However, at heat flux levels below dryout, the nucleate pool boiling process was enhanced considerably over that in earth gravity, in spite of the large vapor bubbles formed in microgravity and perhaps as a consequence. These large vapor bubbles tended to remain in the vicinity of the heater surface, and the enhanced heat transfer appeared to be associated with the presence of what variously has been referred to as a liquid microlayer between the

  3. Electrically Conductive Polyimide Films Containing Gold Surface

    NASA Technical Reports Server (NTRS)

    Caplan, Maggie L.; Stoakley, Diane M.; St. Clair, Anne K.

    1994-01-01

    Polyimide films exhibiting high thermo-oxidative stability and including electrically conductive surface layers containing gold made by casting process. Many variations of basic process conditions, ingredients, and sequence of operations possible, and not all resulting versions of process yield electrically conductive films. Gold-containing layer formed on film surface during cure. These metallic gold-containing polyimides used in film and coating applications requiring electrical conductivity, high reflectivity, exceptional thermal stability, and/or mechanical integrity. They also find commercial potential in areas ranging from thin films for satellite antennas to decorative coatings and packaging.

  4. Mathematical Modelling of Force Convection in a Two-Phase Thermosyphon in Conjugate Formulation

    NASA Astrophysics Data System (ADS)

    Nurpeiis, Atlant; Nee, Alexander

    2016-02-01

    A nonlinear non-stationary problem of the conductive-convective heat transfer is addressed (under forced convection conditions) in the thermosyphon of rectangular cross-section. The thermal energy supply is carried out through the lower horizontal border. The mathematical model is formulated in dimensionless variables of "velocity vorticity vector - current function - temperature". The current and temperature distribution lines are obtained, illustrating the effect of the Reynolds number on the thermodynamic structures formation in the analyzed object.

  5. Electrically conductive connection for an electrode

    SciTech Connect

    Hornack, Thomas R.; Chilko, Robert J.

    1986-01-01

    An electrically conductive connection for an electrode assembly of an electrolyte cell in which aluminum is produced by electrolysis in a molten salt is described. The electrode assembly comprises an electrode flask and a conductor rod. The flask has a collar above an area of minimum flask diameter. The electrically conductive connection comprises the electrode flask, the conductor rod and a structure bearing against the collar and the conductor rod for pulling the conductor rod into compressive and electrical contact with the flask.

  6. Electrically conductive polyimides containing silver trifluoroacetylacetonate

    NASA Technical Reports Server (NTRS)

    Rancourt, James D. (Inventor); Stoakley, Diane M. (Inventor); Caplan, Maggie L. (Inventor); St. Clair, Anne K. (Inventor); Taylor, Larry T. (Inventor)

    1996-01-01

    Polyimides with enhanced electrical conductivity are produced by adding a silver ion-containing additive to the polyamic acid resin formed by the condensation of an aromatic dianhydride with an aromatic diamine. After thermal treatment the resulting polyimides had surface conductivities in the range of 1.7.times.10.sup.-3 4.5 .OMEGA..sup.-1 making them useful in low the electronics industry as flexible, electrically conductive polymeric films and coatings.

  7. Convection

    NASA Astrophysics Data System (ADS)

    Britz, Dieter

    Convection has long been coupled with electrochemistry, and the name hydrodynamic voltammetry has become standard. In electroanalytical chemistry we mainly seek reproducible conditions. These are almost always attained by systems in which a steady convective state is achieved, although not always. Thus, the once popular dropping mercury electrode (see texts such as [74, 257]) has convection around it, but is never in steady state; it might be called a reproducible periodic dynamic state.

  8. Multi-crystalline silicon solidification under controlled forced convection

    NASA Astrophysics Data System (ADS)

    Cablea, M.; Zaidat, K.; Gagnoud, A.; Nouri, A.; Chichignoud, G.; Delannoy, Y.

    2015-05-01

    Multi-crystalline silicon wafers have a lower production cost compared to mono-crystalline wafers. This comes at the price of reduced quality in terms of electrical properties and as a result the solar cells made from such materials have a reduced efficiency. The presence of different impurities in the bulk material plays an important role during the solidification process. The impurities are related to different defects (dislocations, grain boundaries) encountered in multi-crystalline wafers. Applying an alternative magnetic field during the solidification process has various benefits. Impurities concentration in the final ingot could be reduced, especially metallic species, due to a convective term added in the liquid that reduces the concentration of impurities in the solute boundary layer. Another aspect is the solidification interface shape that is influenced by the electromagnetic stirring. A vertical Bridgman type furnace was used in order to study the solidification process of Si under the influence of a travelling magnetic field able to induce a convective flow in the liquid. The furnace was equipped with a Bitter type three-phase electromagnet that provides the required magnetic field. A numerical model of the furnace was developed in ANSYS Fluent commercial software. This paper presents experimental and numerical results of this approach, where interface markings were performed.

  9. Studies of Forced-Convection Heat Transfer Augmentation in Large Containment Enclosures

    SciTech Connect

    Kuhn, S.Z.; Peterson, P.F.

    2001-06-17

    Heat transfer enhancement due to jet mixing inside a cylindrical enclosure is discussed. This work addresses conservative heat transfer assumptions regarding mixing and condensation that have typically been incorporated into passive containment design analyses. This research presents the possibility for increasing decay heat removal of passive containment systems under combined natural and forced convection. Eliminating these conservative assumptions could result in a changed containment design and reduce the construction cost. It is found that the ratio of forced- and free-convection Nusselt numbers can be predicted as a function of the Archimedes number and a correlated factor accounting for jet orientation and enclosure geometry.

  10. A numerical study of Li-SF6 wick combustion - Forced and mixed convective burning

    NASA Technical Reports Server (NTRS)

    Damaso, R. C.; Chen, L.-D.

    1992-01-01

    A numerical study is conducted to study Li-SF6 wick diffusion flames under mixed convective burning conditions at a pressure of 0.01 MPa. Both planar and cylindrical wicks are considered. The model is based on a conserved scalar approach. The objective of this study is to assess the effects of particular parameters on the burning rate and heat transfer. The flat-plate solution yields a fuel mass burning rate per unit surface area following the x exp -1/2 dependence of the classical similarity solution, where x is the streamwise distance. Cylindrical wick geometries yield enhanced burning rates over planar wicks. For the case of mixed convective burning, the burning rate results approach either the forced or natural convective burning limits as ambient streamwise velocity is changed. Critical Richardson numbers specifying these burning limits are determined for a given condition. Reducing gravity results in a lower burning rate because the influence of natural convection is diminished. Under reduced gravity of 1/1000 of the sea-level value, mixed convective burning nearly resembles forced convection.

  11. Electrical conductivity of Al-bearing bridgmanite

    NASA Astrophysics Data System (ADS)

    Yoshino, T.; Kamada, S.; Ohtani, E.; Hirao, N.

    2015-12-01

    Electrical conductivity measurements of bridgmanite with various Al contents and constant Mg# 90 at room temperature up to 2000 K and 26-28 GPa were performed in Kawai-type multianvil apparatus using impedance spectroscopic analyses. The incorporation of Al into bridgmanite significantly raises the electrical conductivity but it is small conductivity variation with respect to the amount of Al. Synchrotron Mössbauer spectroscopy of recovered samples showed a significant amount of ferric iron in aluminous bridgmanite. The mobility of charge carriers in bridgmanite was calculated from the conductivity and Fe3+/ΣFe. A relation between the logarithm of electrical conductivity and reciprocal temperature is consistent with Fe2+-Fe3+ electron hopping (small polaron) as the dominant conduction mechanism at low temperatures (< 1400 K) and ionic conduction at high temperatures (> 1600 K). Taking various conduction mechanisms into account, we develop an electrical conductivity model for aluminous bridgmanite as a function of Al and Fe content. This conductivity model suggests that the electrical conductivity of aluminous bridgmanite has a maximum at around 0.13 Al per formula unit, and further increase of Al in bridgmanite reduces the conductivity. The conductivity increase observed in the uppermost lower mantle by electromagnetic studies can be explained by increases of Fe and Na content in combination with substitution of Al into bridgmanite with increasing pressure due to the gradual decomposition of majorite garnet.

  12. Electrical Conductivity of Ferritin Proteins by Conductive AFM

    NASA Technical Reports Server (NTRS)

    Xu, Degao; Watt, Gerald D.; Harb, John N.; Davis, Robert C.

    2005-01-01

    Electrical conductivity measurements were performed on single apoferritin and holoferritin molecules by conductive atomic force microscopy. Conductivity of self-assembled monolayer films of ferritin molecules on gold surfaces was also measured. Holoferritin was 5-25 times more conductive than apoferritin, indicating that for holoferritin most electron-transfer goes through the ferrihydrite core. With 1 V applied, the average electrical currents through single holoferritin and apoferritin molecules were 2.6 PA and 0.19 PA, respectively.

  13. MHD Forced Convective Laminar Boundary Layer Flow from a Convectively Heated Moving Vertical Plate with Radiation and Transpiration Effect

    PubMed Central

    Uddin, Md. Jashim; Khan, Waqar A.; Ismail, A. I. Md.

    2013-01-01

    A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to whilst the magnetic field and mass transfer velocity are taken to be proportional to where is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

  14. MHD forced convective laminar boundary layer flow from a convectively heated moving vertical plate with radiation and transpiration effect.

    PubMed

    Uddin, Md Jashim; Khan, Waqar A; Ismail, A I Md

    2013-01-01

    A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to x(m) whilst the magnetic field and mass transfer velocity are taken to be proportional to x((m-1)/2) where x is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

  15. Electrically conductive proppant and methods for detecting, locating and characterizing the electrically conductive proppant

    DOEpatents

    Cannan, Chad; Bartel, Lewis; Palisch, Terrence; Aldridge, David

    2015-01-13

    Electrically conductive proppants and methods for detecting, locating, and characterizing same are provided. The electrically conductive proppant can include a substantially uniform coating of an electrically conductive material having a thickness of at least 500 nm. The method can include injecting a hydraulic fluid into a wellbore extending into a subterranean formation at a rate and pressure sufficient to open a fracture therein, injecting into the fracture a fluid containing the electrically conductive proppant, electrically energizing the earth at or near the fracture, and measuring three dimensional (x, y, and z) components of electric and magnetic field responses at a surface of the earth or in an adjacent wellbore.

  16. The Role of Ascent-Forced Convection in Orographic Precipitation: Results from the DOMEX Field Campaign

    NASA Astrophysics Data System (ADS)

    Minder, J. R.; Smith, R. B.; Nugent, A. D.; Kirshbaum, D. J.

    2011-12-01

    Shallow convection is a pervasive feature of orographic precipitation, but its detailed role remains poorly understood. The mountainous Caribbean island of Dominica is a natural laboratory for isolating the role of shallow convection in orographic rainfall. It lies in a region of persistent easterly trade wind flow, and receives much of its rainfall from shallow convection that is forced mechanically by ascent of easterly flow over the Dominican terrain. The Dominica Experiment (DOMEX) has focused on convective orographic precipitation over the island from 2007-2011. The first phase of the project developed a climatology of rainfall and theories to explain the observed enhancement over the terrain. The second phase of the project (Apr-May 2011) has provided a detailed view of 20 individual rainfall events with data from: surface gauges, time-lapse photography, operational radar scans, a mountaintop weather station, and both in situ and remote observations from the University of Wyoming King Air research aircraft. Focusing on ascent--forced convection during DOMEX has revealed a number of the key processes that control the rainfall. Upwind of the island, clouds and water vapor anomalies exist that appear to play a crucial role in seeding the convection over the terrain and determining its vigor. Over the windward slopes the air is readily lifted with little flow deflection. Strong convective cells rapidly develop to produce large rainfall rates. Over the lee slopes of the terrain there is an abrupt transition to a deep and turbulent plunging flow that quickly eliminates convective clouds, but allows for the spillover of rainfall. The air that passes over the island is transformed such that low-levels are dried, warmed and decelerated, and the downwind wake becomes less hospitable to trade wind cumuli.

  17. The electrical conductivity of eclogite in Tibet

    NASA Astrophysics Data System (ADS)

    Guo, Y.; Wang, D.

    2011-12-01

    Qinghai-Tibet Plateau is known as its huge crust and complicated plateau plate tectonics. To understand the geodynamics of this plateau, a variety of geology surveys and geophysical observations were carried out. MT results reveal that the high conductivity zones widely present both in the crust and the mantle. These conductivity anomalies were interpreted as the presence of melt by many researchers. The eclogite is considered as one of candidate rock constituting the lower crust and uppermost mantle. Thus, the electrical conductivity eclogite may provide available information to understand the electrical structure of the crust and the mantle beneath Tibet. The starting material is natural eclogite collected from Pianshishan area, which is located in the middle of Qiangtang. The electrical conductivity of eclogite was measured by using the impedance spectrum method at 1.5, 2.5, 3.5 GPa and 372 ~ 803 K. Oxygen fugacity was controlled by the Mo-MoO2 buffer, The sample temperatures were monitored by a NiCr-NiAl thermocouple. The results show that the pressure weakly affect the electrical conductivity of eclogite. The electrical conductivity of eclogite varies from -5.5 S / m to -1.75 S / m with the temperature increased. The electrical conductivity curves change the slope and alter the conduction mechanism at various pressures. The low-temperature activation enthalpy at 1.5, 2.5, 3.5 GP are 0.380, 0.405, 0.446 eV, whereas high-temperature activation enthalpy are 0.986, 0.986, 1.023 eV, respectively. This results were entrapped to Earth's interior and compared with the magnetotelluric(MT) observations, our model is consistent with one of the electrical conductivity structures derived from geophysical observations.

  18. Effect of a forced Couette flow on coupled convective and morphological instabilities during unidirectional solidification

    NASA Technical Reports Server (NTRS)

    Coriell, S. R.; Mcfadden, G. B.; Boisvert, R. F.; Sekerka, R. F.

    1984-01-01

    The effect of a forced Couette flow, parallel to a horizontal crystal-melt interface during directional solidification of an alloy of lead containing tin, on the onset of convective and morphological instabilities, is calculated numerically via a linear stability analysis. Such a flow does not affect perturbations with wave vectors perpendicular to the flow. For perturbations with wave vectors parallel to the flow, the onset of morphological instability is somewhat suppressed and thermosolutal convection is greatly suppressed. When instabilities occur, they are oscillatory and correspond to travelling waves. For values of the crystal growth velocity for which mixed morphological and convective modes occur, the presence of a forced flow produces sufficient decoupling to allow otherwise degenerate branches to be identified.

  19. Weight and water loss in the neonate in natural and forced convection.

    PubMed Central

    Thompson, M H; Stothers, J K; McLellan, N J

    1984-01-01

    We describe a simple method of determining weight loss and hence water loss of infants in incubators. Unlike previously reported methods, it does not interfere with the microenvironment surrounding the infant. Weight loss of 16 term and 32 preterm infants was measured in both forced and natural convection. No significant increase in water loss was observed in the term infants but in the preterm infants the mean loss in natural convection was 0.85 g/kg/hour compared with 1.26 g/kg/hour in forced convection: in the most extreme situation it was doubled. This water loss represents a substantial energy loss and suggestions to minimise it are discussed. Images Fig. 1 PMID:6497432

  20. Electrically conductive containment vessel for molten aluminum

    DOEpatents

    Holcombe, C.E.; Scott, D.G.

    1984-06-25

    The present invention is directed to a containment vessel which is particularly useful in melting aluminum. The vessel of the present invention is a multilayered vessel characterized by being electrically conductive, essentially nonwettable by and nonreactive with molten aluminum. The vessel is formed by coating a tantalum substrate of a suitable configuration with a mixture of yttria and particulate metal 10 borides. The yttria in the coating inhibits the wetting of the coating while the boride particulate material provides the electrical conductivity through the vessel. The vessel of the present invention is particularly suitable for use in melting aluminum by ion bombardment.

  1. Electrically conductive containment vessel for molten aluminum

    DOEpatents

    Holcombe, Cressie E.; Scott, Donald G.

    1985-01-01

    The present invention is directed to a containment vessel which is particularly useful in melting aluminum. The vessel of the present invention is a multilayered vessel characterized by being electrically conductive, essentially nonwettable by and nonreactive with molten aluminum. The vessel is formed by coating a tantalum substrate of a suitable configuration with a mixture of yttria and particulate metal borides. The yttria in the coating inhibits the wetting of the coating while the boride particulate material provides the electrical conductivity through the vessel. The vessel of the present invention is particularly suitable for use in melting aluminum by ion bombardment.

  2. Electrically conductive connection for an electrode

    DOEpatents

    Hornack, T.R.; Chilko, R.J.

    1986-09-02

    An electrically conductive connection for an electrode assembly of an electrolyte cell in which aluminum is produced by electrolysis in a molten salt is described. The electrode assembly comprises an electrode flask and a conductor rod. The flask has a collar above an area of minimum flask diameter. The electrically conductive connection comprises the electrode flask, the conductor rod and a structure bearing against the collar and the conductor rod for pulling the conductor rod into compressive and electrical contact with the flask. 2 figs.

  3. Forced-to-natural convection transition tests in parallel simulated liquid metal reactor fuel assemblies

    SciTech Connect

    Levin, A.E. ); Montgomery, B.H. )

    1990-01-01

    The Thermal-Hydraulic Out of Reactor Safety (THORS) Program at Oak Ridge National Laboratory (ORNL) had as its objective the testing of simulated, electrically heated liquid metal reactor (LMR) fuel assemblies in an engineering-scale, sodium loop. Between 1971 and 1985, the THORS Program operated 11 simulated fuel bundles in conditions covering a wide range of normal and off-normal conditions. The last test series in the Program, THORS-SHRS Assembly 1, employed two parallel, 19-pin, full-length, simulated fuel assemblies of a design consistent with the large LMR (Large Scale Prototype Breeder -- LSPB) under development at that time. These bundles were installed in the THORS Facility, allowing single- and parallel-bundle testing in thermal-hydraulic conditions up to and including sodium boiling and dryout. As the name SHRS (Shutdown Heat Removal System) implies, a major objective of the program was testing under conditions expected during low-power reactor operation, including low-flow forced convection, natural convection, and forced-to-natural convection transition at various powers. The THORS-SHRS Assembly 1 experimental program was divided up into four phases. Phase 1 included preliminary and shakedown tests, including the collection of baseline steady-state thermal-hydraulic data. Phase 2 comprised natural convection testing. Forced convection testing was conducted in Phase 3. The final phase of testing included forced-to-natural convection transition tests. Phases 1, 2, and 3 have been discussed in previous papers. The fourth phase is described in this paper. 3 refs., 2 figs.

  4. Experimental investigation of forced-convection heat-transfer characteristics of lead-bismuth eutectic

    NASA Technical Reports Server (NTRS)

    Lubarsky, Bernard

    1951-01-01

    The forced-convection heat-transfer characteristics of lead-bismuth eutectic were experimentally investigated. Experimental values of Nusselt number for lead-bismuth fell considerably below predicted values. The addition of a wetting agent did not change the heat transfer characteristics.

  5. Electrically conducting polymers for aerospace applications

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Gaier, James R.; Good, Brian S.; Sharp, G. R.; Meador, Michael A.

    1991-01-01

    Current research on electrically conducting polymers from 1974 to the present is reviewed focusing on the development of materials for aeronautic and space applications. Problems discussed include extended pi-systems, pyrolytic polymers, charge-transfer systems, conductive matrix resins for composite materials, and prospects for the use of conducting polymers in space photovoltaics.

  6. Electrically-Conductive Polyaramid Cable And Fabric

    NASA Technical Reports Server (NTRS)

    Orban, Ralph F.

    1988-01-01

    Tows coated with metal provide strength and conductance. Cable suitable for use underwater made of electrically conductive tows of metal-coated polyaramid filaments surrounded by electrically insulating jacket. Conductive tows used to make conductive fabrics. Tension borne by metal-coated filaments, so upon release, entire cable springs back to nearly original length without damage.

  7. Universal thermal and electrical conductivity from holography

    NASA Astrophysics Data System (ADS)

    Jain, Sachin

    2010-11-01

    It is known from earlier work of Iqbal, Liu [1] that the boundary transport coefficients such as electrical conductivity (at vanishing chemical potential), shear viscosity etc. at low frequency and finite temperature can be expressed in terms of geometrical quantities evaluated at the horizon. In the case of electrical conductivity, at zero chemical potential gauge field fluctuation and metric fluctuation decouples, resulting in a trivial flow from horizon to boundary. In the presence of chemical potential, the story becomes complicated due to the fact that gauge field and metric fluctuation can no longer be decoupled. This results in a nontrivial flow from horizon to boundary. Though horizon conductivity can be expressed in terms of geometrical quantities evaluated at the horizon, there exist no such neat result for electrical conductivity at the boundary. In this paper we propose an expression for boundary conductivity expressed in terms of geometrical quantities evaluated at the horizon and thermodynamic quantities. We also consider the theory at finite cutoff recently constructed in [2], at radius r c outside the horizon and give an expression for cutoff dependent electrical conductivity ( σ( r c )), which interpolates smoothly between horizon conductivity σ H ( r c → r h ) and boundary conductivity σ B ( r c → ∞). Using the results about the conductivity we gain much insight into the universality of thermal conductivity to viscosity ratio proposed in [3].

  8. Potential Aerosol Indirect Effects on Atmospheric Circulation and Radiative Forcing through Deep Convection

    SciTech Connect

    Fan, Jiwen; Rosenfeld, Daniel; Ding, Yanni; Leung, Lai-Yung R.; Li, Zhanqing

    2012-05-10

    Aerosol indirect effects, i.e., the interactions of aerosols with clouds by serving as cloud condensation nuclei (CCN) or ice nuclei (IN), constitute the largest uncertainty in climate forcing and projection. Previous IPCC reported aerosol indirect forcing is negative, which does not account for aerosol-convective cloud interactions because the complex processes involved are poorly understood and represented in climate models. Here we report that aerosol indirect effect on deep convective cloud systems can lead to enhanced regional convergence and a strong top-of atmosphere (TOA) warming. Aerosol invigoration effect on convection can result in a strong radiative warming in the atmosphere (+5.6 W m-2) due to strong night-time warming, a lofted latent heating, and a reduced diurnal temperature difference, all of which could remarkably impact regional circulation and modify weather systems. We further elucidated how aerosols change convective intensity, diabatic heating, and regional circulation under different environmental conditions and concluded that wind shear and cloud base temperature play key roles in determining the significance of aerosol invigoration effect for convective systems.

  9. Determination of forced convective heat transfer coefficients for subsonic flows over heated asymmetric NANA 4412 airfoil

    NASA Astrophysics Data System (ADS)

    Dag, Yusuf

    Forced convection over traditional surfaces such as flat plate, cylinder and sphere have been well researched and documented. Data on forced convection over airfoil surfaces, however, remain very scanty in literature. High altitude vehicles that employ airfoils as lifting surfaces often suffer leading edge ice accretions which have tremendous negative consequences on the lifting capabilities and stability of the vehicle. One of the ways of mitigating the effect of ice accretion involves judicious leading edge convective cooling technique which in turn depends on the accuracy of convective heat transfer coefficient used in the analysis. In this study empirical investigation of convective heat transfer measurements on asymmetric airfoil is presented at different angle of attacks ranging from 0° to 20° under subsonic flow regime. The top and bottom surface temperatures are measured at given points using Senflex hot film sensors (Tao System Inc.) and used to determine heat transfer characteristics of the airfoils. The model surfaces are subjected to constant heat fluxes using KP Kapton flexible heating pads. The monitored temperature data are then utilized to determine the heat convection coefficients modelled empirically as the Nusselt Number on the surface of the airfoil. The experimental work is conducted in an open circuit-Eiffel type wind tunnel, powered by a 37 kW electrical motor that is able to generate subsonic air velocities up to around 41 m/s in the 24 square-inch test section. The heat transfer experiments have been carried out under constant heat flux supply to the asymmetric airfoil. The convective heat transfer coefficients are determined from measured surface temperature and free stream temperature and investigated in the form of Nusselt number. The variation of Nusselt number is shown with Reynolds number at various angles of attacks. It is concluded that Nusselt number increases with increasing Reynolds number and increase in angle of attack from 0

  10. Ray-tracing simulations vs. satellite observations of gravity waves forced by deep convection

    NASA Astrophysics Data System (ADS)

    Kalisch, Silvio; Trinh, Thai; Chun, Hye-Yeong; Ern, Manfred; Preusse, Peter; Eckermann, Stephen D.; Riese, Martin

    2015-04-01

    Gravity waves (GW) are a prominent coupling mechanism between their tropospheric sources and the upper stratosphere to mesosphere region. They contribute prominently to the wave driving of the Quasi-biennial-oscillation (QBO) in the tropics and other large scale circulations like the Brewer-Dobson circulation. One important dynamic source of GWs is convection. Convective GWs have considerable short horizontal wavelengths and are therefore not entirely observable by infrared limb-sounding satellite instruments. For this reason, we present the results of GW ray-tracing calculations from convective sources up to the mesosphere. We utilized the Gravity wave Regional Or Global RAy-Tracer (GROGRAT) to perform the GW trajectory calculations. The launch conditions for each GW were calculated using the convective GW source scheme from Yonsei University (South Korea) to quantify the excitation by deep convection. Heating rates, cloud data, and atmospheric background data were provided by the MERRA dataset for the estimation of convective forcing by deep convection and as the atmospheric background for the ray-tracing calculations afterwards. The resulting momentum flux distributions are in remarkable coincidence with typical geographic regions of deep convection in the tropics. Additionally, the momentum flux distributions of higher latitude regions are simulated using a standard launch distribution for GWs. In order to validate our findings we compare our simulation results with satellite measurements of temperature amplitudes and momentum flux from infrared limb-sounding satellite instruments. These validations are complemented with an in-depth analysis of the observational filter for two different satellite instruments (HIRDLS and SABER). Scanning geometry, limitations in the detection of short wavelengths, aliasing effects, and the detector sensitivity are taken into account to quantify the level of uncertainty in our results. This analysis finally shows a good agreement

  11. A Study of Nucleate Boiling with Forced Convection in Microgravity

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1996-01-01

    Boiling is a rather imprecise term applied to the process of evaporation in which the rate of liquid-vapor phase change is large. In seeking to determine the role and significance of body forces on the process, of which buoyancy or gravity is just one agent, it becomes necessary to define the term more precisely. It is generally characterized by the formation and growth of individual vapor bubbles arising from heat transfer to the liquid, either at a solid/liquid or liquid/liquid interface, or volumetrically. The terms 'bubble' boiling and 'nucleate' boiling are frequently used, in recognition of the interactions of surface tension and other forces in producing discrete bubbles at distinctive locations (although not always). Primary considerations are that evaporation can occur only at existing liquid-vapor interfaces, so that attention must be given to the formation of an interface (the nucleation process), and that the latent heat for this evaporation can come only from the superheated liquid, so that attention must also be given to the temperature distributions in the liquid.

  12. Forced Convective Thermal Transport and Flow Stability Characteristics in Near-Critical Supercritical Fluid

    NASA Astrophysics Data System (ADS)

    Hasan, Nusair; Farouk, Bakhtier

    2013-11-01

    Forced convective thermal transport characteristics of supercritical carbon dioxide in vertical flow are numerically investigated. A tube with a circular cross-section and heated side-wall is considered. A real-fluid model for representing the thermo-physical properties of the supercritical fluid along with the fully compressible form of the Navier-Stokes equations and an implicit time-marching scheme is used to solve the problem. Thermo-physical properties of near-critical supercritical fluids show diverging characteristics. Large variations of density of near-critical supercritical fluid in forced convective flow can induce thermo-hydraulic instability similar to density wave oscillations. The developed numerical model is used for studying the effect of geometrical parameters of the tube, wall heat flux and pressure on steady-state convective thermal transport as well as the stability behavior of the supercritical fluid near its critical point. The enhancement or deterioration of heat transfer caused by the temperature-induced variation of physical properties (especially specific heat) is also investigated, as well as the effect of buoyancy on the forced convective flow.

  13. Numerical calculation of the drag force induced by natural convection of spheres at low Grashof numbers

    SciTech Connect

    Dudek, D.; Fletcher, T.H.

    1987-02-01

    When a heated solid sphere is introduced into an ambient fluid, a natural convective flow occurs which results in a drag force on the sphere. This study involves the numerical calculation of both the steady-state and the transient natural convective drag force around spheres at low Grashof numbers. Numerical techniques are taken from Geoola and Cornish. An empirical expression is suggested for the total drag coefficient for Grashof numbers ranging from 4 x 10/sup -4/ to 0.5 and Prandtl number = 0.72: log C/sub DT/ = 1.25 + 0.31 log Gr - 0.097(log Gr)/sup 2/. The dimensionless time required to reach 90% of the steady-state drag force can be approximated by the second-order polynomial: log t/sub 90%/ = 1.32 - log Gr - 0.11(Gr)/sup 2/.

  14. Electrically conductive palladium containing polyimide films

    NASA Technical Reports Server (NTRS)

    Taylor, L. T.; St.clair, A. K.; Carver, V. C.; Furtsch, T. A. (Inventor)

    1982-01-01

    Lightweight, high temperature resistant, electrically conductive, palladium containing polyimide films and methods for their preparation are described. A palladium (II) ion-containing polyamic acid solution is prepared by reacting an aromatic dianhydride with an equimolar quantity of a palladium II ion-containing salt or complex and the reactant product is cast as a thin film onto a surface and cured at approximately 300 C to produce a flexible electrically conductive cyclic palladium containing polyimide. The source of palladium ions is selected from the group of palladium II compounds consisting of LiPdCl4, PdS(CH3)2Cl2Na2PdCl4, and PdCl2. The films have application to aerodynamic and space structures and in particular to the relieving of space charging effects.

  15. Electrical conductivity in sprite streamer channels

    NASA Astrophysics Data System (ADS)

    Gordillo-Vázquez, F. J.; Luque, A.

    2010-08-01

    We study the electrical conductivity of a sprite streamer channel at three different altitudes (63 km, 70 km and 80 km). We discuss the hypothesis that the electrical conductivity stays constant along the full length of a streamer channel, contrary to expectations based on scaling laws. We then apply this hypothesis and extrapolations from a numerical electrodynamical simulation to study the air plasma kinetics after the passage of a streamer. We test two possible scenarios for the physical origin of trailing sprite emissions: a single pulse and a single pulse with a delayed re-enhancement of the electric field up to the breakdown value. Our simulations show that VLF observations agree with persistent electric fields in the sprite that last several milliseconds and that associative detachment of O- ions may significantly affect the atmospheric conductivity in the presence of sprites.

  16. Electrically conducting polyimide film containing tin complexes

    NASA Technical Reports Server (NTRS)

    St. Clair, Anne K. (Inventor); Ezzell, Stephen A. (Inventor); Taylor, Larry T. (Inventor); Boston, Harold G. (Inventor)

    1996-01-01

    Disclosed is a thermally-stable SnO.sub.2 -surfaced polyimide film wherein the electrical conductivity of the SnO.sub.2 surface is within the range of about 3.0.times.10.sup.-3 to about 1.times.10.sup.-2 ohms.sup.-1,. Also disclosed is a method of preparing this film from a solution containing a polyamic acid and SnCl.sub.4 (DMSO).sub.2.

  17. Electrical conductivity of acidic sulfate solution

    NASA Astrophysics Data System (ADS)

    Majima, Hiroshi; Peters, Ernest; Awakura, Yasuhiro; Park, Sung Kook

    1987-03-01

    The electrical conductivities of the aqueous solution system of H2SO4-MSO4 (involving ZnSO4, MgSO4, Na2SO4, and (NH4)2SO4), reported by Tozawa et al., were examined in terms of a (H2O) and H+ ion concentration. The equations to compute the concentrations of various species in aqueous sulfuric acid solutions containing metal sulfates were derived for a typical example of the H2SO4-ZnSO4-MgSO4-(Na2SO4)-H2O system. It was found that the H+ ion concentrations in concentrated sulfuric acid solutions corresponding to practical zinc electrowinning solutions are very high and remain almost constant with or without the addition of metal sulfates. The addition of metal sulfates to aqueous sulfuric acid solution causes a decrease in electrical conductivity, and this phenomenon is attributed to a decrease in water activity, which reflects a decrease in the amount of free water. The relationship between conductivity and water activity at a constant H+ ion concentration is independent of the kind of sulfates added. On the other hand, any increase in H+ ion concentration results in an increase in electrical conductivity. A novel method for the prediction of electrical conductivity of acidic sulfate solution is proposed that uses the calculated data of water activity and the calculated H+ ion concentration. Also, the authors examined an extension of the Robinson-Bower equation to calculate water activity in quarternary solutions based on molarity instead of molality, and found that such calculated values are in satisfactory agreement with those determined experimentally by a transpiration method.

  18. Convectively Forced Gravity Waves and their Sensitivity to Heating Profile and Atmospheric Structure

    NASA Astrophysics Data System (ADS)

    Halliday, Oliver; Parker, Douglas; Griffiths, Stephen; Vosper, Simon; Stirling, Alison

    2016-04-01

    It has been known for some time that convective heating is communicated to its environment by gravity waves. Despite this, the radiation of gravity waves in macro-scale models, which are typically forced at the grid-scale by meso-scale parameterization schemes, is not well understood. We present here theoretical work directed toward improving our fundamental understanding of convectively forced gravity wave effects at the meso-scale, in order to begin to address this problem. Starting with the hydrostatic, non-rotating, 2D, Boussinesq equations in a slab geometry, we find a radiating, analytical solution to prescribed sensible heat forcing for both the vertical velocity and potential temperature response. Both Steady and pulsed heating with adjustable horizontal structure is considered. From these solutions we construct a simple model capable of interrogating the spatial and temporal sensitivity to chosen heating functions of the remote forced response in particular. By varying the assumed buoyancy frequency, the influence of the model stratosphere on the upward radiation of gravity waves, and in turn, on the tropospheric response can be understood. Further, we find that the macro-scale response to convection is highly dependent on the radiation characteristics of gravity waves, which are in turn dependent upon the temporal and spatial structure of the source, and upper boundary condition of the domain.

  19. Electric conductivity of plasma in solar wind

    NASA Technical Reports Server (NTRS)

    Chertkov, A. D.

    1995-01-01

    One of the most important parameters in MHD description of the solar wind is the electric conductivity of plasma. There exist now two quite different approaches to the evaluation of this parameter. In the first one a value of conductivity taken from the most elaborated current theory of plasma should be used in calculations. The second one deals with the empirical, phenomenological value of conductivity. E.g.: configuration of interplanetary magnetic field, stretched by the expanding corona, depends on the magnitude of electrical conductivity of plasma in the solar wind. Knowing the main empirical features of the field configuration, one may estimate the apparent phenomenological value of resistance. The estimations show that the electrical conductivity should be approximately 10(exp 13) times smaller than that calculated by Spitzer. It must be noted that the empirical value should be treated with caution. Due to the method of its obtaining it may be used only for 'large-scale' description of slow processes like coronal expansion. It cannot be valid for 'quick' processes, changing the state of plasma, like collisions with obstacles, e.g., planets and vehicles. The second approach is well known in large-scale planetary hydrodynamics, stemming from the ideas of phenomenological thermodynamics. It could formulate real problems which should be solved by modern plasma physics, oriented to be adequate for complicated processes in space.

  20. Effects of vertically ribbed surface roughness on the forced convective heat losses in central receiver systems

    NASA Astrophysics Data System (ADS)

    Uhlig, Ralf; Frantz, Cathy; Fritsch, Andreas

    2016-05-01

    External receiver configurations are directly exposed to ambient wind. Therefore, a precise determination of the convective losses is a key factor in the prediction and evaluation of the efficiency of the solar absorbers. Based on several studies, the forced convective losses of external receivers are modeled using correlations for a roughened cylinder in a cross-flow of air. However at high wind velocities, the thermal efficiency measured during the Solar Two experiment was considerably lower than the efficiency predicted by these correlations. A detailed review of the available literature on the convective losses of external receivers has been made. Three CFD models of different level of detail have been developed to analyze the influence of the actual shape of the receiver and tower configuration, of the receiver shape and of the absorber panels on the forced convective heat transfer coefficients. The heat transfer coefficients deduced from the correlations have been compared to the results of the CFD simulations. In a final step the influence of both modeling approaches on the thermal efficiency of an external tubular receiver has been studied in a thermal FE model of the Solar Two receiver.

  1. Effects of aerosol optical properties on deep convective clouds and radiative forcing

    SciTech Connect

    Fan, Jiwen; Zhang, Renyi; Tao, Wei-Kuo; Mohr, Karen I

    2008-04-23

    The aerosol radiative effects (ARE) on the deep convective clouds are investigated by using a spectral-bin cloud-resolving model coupled with a radiation scheme and an explicit land surface model. The sensitivity of cloud properties and the associated radiative forcing to aerosol single-scattering albedo (SSA) are examined. The ARE on cloud properties is pronounced for mid-visible SSA of 0.85. Relative to the case without ARE, the cloud fraction and optical depth decrease by about 18% and 20%, respectively. Ice particle number concentrations, liquid water path, ice water path, and droplet size decrease by more than 15% when the ARE is introduced. The ARE causes a surface cooling of about 0.35 K and significantly high heating rates in the lower troposphere (about 0.6 K day-1 higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection explains the less cloudiness, lower cloud optical depth, less LWP and IWP, smaller droplet size, and less precipitation resulting from the ARE. The daytime-mean direct forcing induced by black carbon is about 2.2 W m-2 at the top of atmosphere (TOA) and -17.4 W m-2 at the surface for SSA of 0.85. The semi-direct forcing is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Both the TOA and surface total radiative forcing values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect forcing. Aerosol direct and semi-direct effects are very sensitive to SSA when aerosol optical depth is high. Because the positive semi-direct forcing compensates the negative direct forcing at the surface, the surface temperature and heat fluxes decrease less significantly with the increase of aerosol absorption (decreasing SSA). The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced

  2. Aerosol Radiative Effects on Deep Convective Clouds and Associated Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Fan, J.; Zhang, R.; Tao, W.-K.; Mohr, I.

    2007-01-01

    The aerosol radiative effects (ARE) on the deep convective clouds are investigated by using a spectral-bin cloud-resolving model (CRM) coupled with a radiation scheme and an explicit land surface model. The sensitivity of cloud properties and the associated radiative forcing to aerosol single-scattering albedo (SSA) are examined. The ARE on cloud properties is pronounced for mid-visible SSA of 0.85. Relative to the case excluding the ARE, cloud fraction and optical depth decrease by about 18% and 20%, respectively. Cloud droplet and ice particle number concentrations, liquid water path (LWP), ice water path (IWP), and droplet size decrease significantly when the ARE is introduced. The ARE causes a surface cooling of about 0.35 K and significantly high heating rates in the lower troposphere (about 0.6K/day higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection and the more desiccation of cloud layers explain the less cloudiness, lower cloud optical depth, LWP and IWP, smaller droplet size, and less precipitation. The daytime-mean direct forcing induced by black carbon is about 2.2 W/sq m at the top of atmosphere (TOA) and -17.4 W/sq m at the surface for SSA of 0.85. The semi-direct forcing is positive, about 10 and 11.2 W/sq m at the TOA and surface, respectively. Both the TOA and surface total radiative forcing values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect forcing. Aerosol direct and semi-direct effects are very sensitive to SSA. Because the positive semi-direct forcing compensates the negative direct forcing at the surface, the surface temperature and heat fluxes decrease less significantly with the increase of aerosol absorption (decreasing SSA). The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable and dryer atmosphere due to enhanced surface cooling and

  3. Effects of aerosol optical properties on deep convective clouds and radiative forcing

    NASA Astrophysics Data System (ADS)

    Fan, Jiwen; Zhang, Renyi; Tao, Wei-Kuo; Mohr, Karen I.

    2008-04-01

    The aerosol radiative effects (ARE) on the deep convective clouds are investigated by using a spectral-bin cloud-resolving model coupled with a radiation scheme and an explicit land surface model. The sensitivity of cloud properties and the associated radiative forcing to aerosol single-scattering albedo (SSA) are examined. The ARE on cloud properties is pronounced for mid-visible SSA of 0.85. Relative to the case without ARE, the cloud fraction and optical depth decrease by about 18% and 20%, respectively. Ice particle number concentrations, liquid water path, ice water path, and droplet size decrease by more than 15% when the ARE is introduced. The ARE causes a surface cooling of about 0.35 K and significantly high heating rates in the lower troposphere (about 0.6 K day-1 higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection explains the less cloudiness, lower cloud optical depth, less LWP and IWP, smaller droplet size, and less precipitation resulting from the ARE. The daytime-mean direct forcing induced by black carbon is about 2.2 W m-2 at the top of atmosphere (TOA) and -17.4 W m-2 at the surface for SSA of 0.85. The semi-direct forcing is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Both the TOA and surface total radiative forcing values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect forcing. Aerosol direct and semi-direct effects are very sensitive to SSA when aerosol optical depth is high. Because the positive semi-direct forcing compensates the negative direct forcing at the surface, the surface temperature and heat fluxes decrease less significantly with the increase of aerosol absorption (decreasing SSA). The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced surface cooling and atmospheric heating.

  4. Simulation of forced convection-infrared reflow soldering with nitrogen injection

    SciTech Connect

    Son, Y.S.; Bergman, T.L.; Hyun, M.T.

    1995-12-31

    In this paper, forced convection reflow soldering is simulated using an existing numerical model which accounts for multimode effects and is capable of predicting large and small scale thermal and species concentration phenomena. Soldering is performed in an oven equipped with porous panel heaters through which air or nitrogen is introduced to the reflow environment. The gas is injected selectively through top or bottom infrared heaters in order to (1) dampen gas temperature fluctuations which can be established by thermal buoyancy forces and (2) minimize nitrogen use. The results reveal the utility of general process models of the reflow operation as applied to oven design. The effects of mixed convection on heat and gas species transport in the oven are also revealed, and the potential impact on the solidification process is discussed.

  5. Forced-convection Heat Transfer to Water at High Pressures and Temperatures in the Nonboiling Region

    NASA Technical Reports Server (NTRS)

    Kaufman, S J; Henderson, R W

    1951-01-01

    Forced-convection heat-transfer data have been obtained for water flowing in an electrically heated tube of circular cross section at water pressures of 200 and 2000 pounds per square inch, and temperatures in the nonboiling region, for water velocities ranging between 5 and 25 feet per second. The results indicate that conventional correlations can be used to predict heat-transfer coefficients for water at pressures up to 2000 pounds per square inch and temperatures in the nonboiling region.

  6. Performance characteristics of a thermal energy storage module - A transient PCM/forced convection conjugate analysis

    NASA Technical Reports Server (NTRS)

    Cao, Y.; Faghri, A.

    1991-01-01

    The performance of a thermal energy storage module is simulated numerically. The change of phase of the phase-change material (PCM) and the transient forced convective heat transfer for the transfer fluid with low Prandtl numbers are solved simultaneously as a conjugate problem. A parametric study and a system optimization are conducted. The numerical results show that module geometry is crucial to the design of a space-based thermal energy storage system.

  7. Extinction of a bacterial colony under forced convection in pie geometry.

    PubMed

    Shnerb, N M

    2001-01-01

    The extinction of a bacterial colony, as it is forced to migrate into a hostile environment, is analyzed in pie geometry. Under convection, separation of the radial and the azimuthal degrees of freedom is not possible, so the linearized evolution operator is diagonalized numerically. Some characteristic scales are compared with the results of recent experiments, and the "integrable" limit of the theory in the narrow growth region is studied. PMID:11304286

  8. Estimation of boundary heat flux using experimental temperature data in turbulent forced convection flow

    NASA Astrophysics Data System (ADS)

    Parwani, Ajit K.; Talukdar, Prabal; Subbarao, P. M. V.

    2014-09-01

    Heat flux at the boundary of a duct is estimated using the inverse technique based on conjugate gradient method (CGM) with an adjoint equation. A two-dimensional inverse forced convection hydrodynamically fully developed turbulent flow is considered. The simulations are performed with temperature data measured in the experimental test performed on a wind tunnel. The results show that the present numerical model with CGM is robust and accurate enough to estimate the strength and position of boundary heat flux.

  9. Estimation of boundary heat flux using experimental temperature data in turbulent forced convection flow

    NASA Astrophysics Data System (ADS)

    Parwani, Ajit K.; Talukdar, Prabal; Subbarao, P. M. V.

    2015-03-01

    Heat flux at the boundary of a duct is estimated using the inverse technique based on conjugate gradient method (CGM) with an adjoint equation. A two-dimensional inverse forced convection hydrodynamically fully developed turbulent flow is considered. The simulations are performed with temperature data measured in the experimental test performed on a wind tunnel. The results show that the present numerical model with CGM is robust and accurate enough to estimate the strength and position of boundary heat flux.

  10. Response of High Latitude Birkeland Currents and Ionospheric Convection to Transitions in Solar Wind Forcing

    NASA Astrophysics Data System (ADS)

    Anderson, B. J.; Korth, H.; Merkin, V. G.; Barnes, R. J.; Ruohoniemi, J. M.

    2014-12-01

    Recent results from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) indicate that at least some transitions from northward to southward IMF produce a specific sequence in the development of large-scale Birkeland currents. First, a set of Region 1 and Region 2 currents forms on the dayside restricted to within a few hours of noon. After about 40 minutes, currents strongly intensify on the nightside, first near midnight local time associated with substorm onset, and then progressively further toward the dayside via dawn and dusk. Only after an hour or more after the transition to stronger solar wind forcing, is the complete Region 1, Region 2 current system developed. The results imply that the initial response to a transition from weak to strong forcing is convection into the polar cap and lobes without strong return convection to the dayside from the nightside magnetosphere. Return convection from the nightside begins with substorm onset and progresses to the dayside. This analysis is extended by examining a large number of transitions from prolonged auroral quiescence, associated with northward IMF, to southward IMF and the development of large-scale Region 1/Region 2 Birkeland currents, to assess whether the above progression holds in general. In addition, transition events to particularly intense driving, for example, associated with shocks are examined to assess how this ordering of events may be changed for onsets of particularly intense solar wind forcing.

  11. Film boiling heat transfer from a sphere in natural and forced convection of freon-113

    SciTech Connect

    Dix, D.; Orozco, J. )

    1990-01-01

    Boiling heat transfer fluxes were measured on a 3.84-cm hollow copper sphere, in both forced convection and pool boiling, as a function of angular position in Freon 113. This paper reports on forced-convection tests run at speeds of 0.5 to 1.9 m/s. These tests were conducted in the stable film boiling region of the boiling curve. Significant heat transfer rates were measured in the vapor wake region of the sphere for flow film boiling. Video observations of the boiling process revealed that the flow film boiling vapor removal mechanism consisted of periodic formation and detachment of a vapor wake in the rear of the sphere. For pool boiling it was found that the heated surface had a uniform rate of energy dissipation in the stable film boiling regime, whereas in forced convection the film boiling rate was dependent on angular position. Pool film boiling tests also showed multiple humps (more than one maximum heat flux) in the boiling curve when the liquid was subcooled.

  12. Material transport in a convective surface mixed layer under weak wind forcing

    NASA Astrophysics Data System (ADS)

    Mensa, Jean A.; Özgökmen, Tamay M.; Poje, Andrew C.; Imberger, Jörg

    2015-12-01

    Flows in the upper ocean mixed layer are responsible for the transport and dispersion of biogeochemical tracers, phytoplankton and buoyant pollutants, such as hydrocarbons from an oil spill. Material dispersion in mixed layer flows subject to diurnal buoyancy forcing and weak winds (| u10 | = 5m s-1) are investigated using a non-hydrostatic model. Both purely buoyancy-forced and combined wind- and buoyancy-forced flows are sampled using passive tracers, as well as 2D and 3D particles to explore characteristics of horizontal and vertical dispersion. It is found that the surface tracer patterns are determined by the convergence zones created by convection cells within a time scale of just a few hours. For pure convection, the results displayed the classic signature of Rayleigh-Benard cells. When combined with a wind stress, the convective cells become anisotropic in that the along-wind length scale gets much larger than the cross-wind scale. Horizontal relative dispersion computed by sampling the flow fields using both 2D and 3D passive particles is found to be consistent with the Richardson regime. Relative dispersion is an order of magnitude higher and 2D surface releases transition to Richardson regime faster in the wind-forced case. We also show that the buoyancy-forced case results in significantly lower amplitudes of scale-dependent horizontal relative diffusivity, kD(ℓ), than those reported by Okubo (1970), while the wind- and buoyancy-forced case shows a good agreement with Okubo's diffusivity amplitude, and the scaling is consistent with Richardson's 4/3rd law, kD ∼ ℓ4/3. These modeling results provide a framework for measuring material dispersion by mixed layer flows in future observational programs.

  13. Thermal and electrical conductivity of iron at Earth's core conditions.

    PubMed

    Pozzo, Monica; Davies, Chris; Gubbins, David; Alfè, Dario

    2012-05-17

    The Earth acts as a gigantic heat engine driven by the decay of radiogenic isotopes and slow cooling, which gives rise to plate tectonics, volcanoes and mountain building. Another key product is the geomagnetic field, generated in the liquid iron core by a dynamo running on heat released by cooling and freezing (as the solid inner core grows), and on chemical convection (due to light elements expelled from the liquid on freezing). The power supplied to the geodynamo, measured by the heat flux across the core-mantle boundary (CMB), places constraints on Earth's evolution. Estimates of CMB heat flux depend on properties of iron mixtures under the extreme pressure and temperature conditions in the core, most critically on the thermal and electrical conductivities. These quantities remain poorly known because of inherent experimental and theoretical difficulties. Here we use density functional theory to compute these conductivities in liquid iron mixtures at core conditions from first principles--unlike previous estimates, which relied on extrapolations. The mixtures of iron, oxygen, sulphur and silicon are taken from earlier work and fit the seismologically determined core density and inner-core boundary density jump. We find both conductivities to be two to three times higher than estimates in current use. The changes are so large that core thermal histories and power requirements need to be reassessed. New estimates indicate that the adiabatic heat flux is 15 to 16 terawatts at the CMB, higher than present estimates of CMB heat flux based on mantle convection; the top of the core must be thermally stratified and any convection in the upper core must be driven by chemical convection against the adverse thermal buoyancy or lateral variations in CMB heat flow. Power for the geodynamo is greatly restricted, and future models of mantle evolution will need to incorporate a high CMB heat flux and explain the recent formation of the inner core. PMID:22495307

  14. Electrical Conduction in Transition-Metal Salts

    NASA Astrophysics Data System (ADS)

    Grado-Caffaro, M. A.; Grado-Caffaro, M.

    2016-04-01

    We predict that a given transition-metal salt as, for example, a K2CuCl4·2H2O-type compound, can behave as an electrical conductor in the paramagnetic case. In fact, we determine the electrical conductance in a salt of this type. This conductance is found to be quantised in agreement with previous well-known results. Related mathematical expressions in the context of superexchange interaction are obtained. In addition, we determine the corresponding (macroscopically viewed) current density and the associated electron wave functions.

  15. Electrical conductivity in the early universe

    NASA Astrophysics Data System (ADS)

    Baym, Gordon; Heiselberg, Henning

    1997-10-01

    We calculate the electrical conductivity in the early universe at temperatures below as well as above the electroweak vacuum scale, Tc~=100 GeV. Debye and dynamical screening of electric and magnetic interactions leads to a finite conductivity, σel~T/α ln(1/α), at temperatures well below Tc. At temperatures above, W+/- charge-exchange processes-analogous to color exchange through gluons in QCD-effectively stop left-handed charged leptons. However, right-handed leptons can carry current, resulting in σel/T being only a factor ~cos4 θW smaller than at temperatures below Tc.

  16. Numerical recovery of certain discontinuous electrical conductivities

    NASA Technical Reports Server (NTRS)

    Bryan, Kurt

    1991-01-01

    The inverse problem of recovering an electrical conductivity of the form Gamma(x) = 1 + (k-1)(sub Chi(D)) (Chi(D) is the characteristic function of D) on a region omega is a subset of 2-dimensional Euclid space from boundary data is considered, where D is a subset of omega and k is some positive constant. A linearization of the forward problem is formed and used in a least squares output method for approximately solving the inverse problem. Convergence results are proved and some numerical results presented.

  17. Electrical Conductivity Calculations from the Purgatorio Code

    SciTech Connect

    Hansen, S B; Isaacs, W A; Sterne, P A; Wilson, B G; Sonnad, V; Young, D A

    2006-01-09

    The Purgatorio code [Wilson et al., JQSRT 99, 658-679 (2006)] is a new implementation of the Inferno model describing a spherically symmetric average atom embedded in a uniform plasma. Bound and continuum electrons are treated using a fully relativistic quantum mechanical description, giving the electron-thermal contribution to the equation of state (EOS). The free-electron density of states can also be used to calculate scattering cross sections for electron transport. Using the extended Ziman formulation, electrical conductivities are then obtained by convolving these transport cross sections with externally-imposed ion-ion structure factors.

  18. Effect of forced convection on the collision and interaction between nanoparticles and ultramicroelectrode.

    PubMed

    Jiang, Jing; Huang, Xinjian; Wang, Lishi

    2016-04-01

    Detection of nanoparticle (NP) collision events at ultramicroelectrode (UME) has emerged as a new methodology for the investigation of single NP in recent years. Although the method was widely employed, some fundamental knowledge such as how the NP moves to and interacts with the UME remain less understood. It was generally recognized that the recorded rate of collision was determined by diffusion that should follow Fick's first law. However, significant lower collision frequency compared with that of predicted by theory were frequently reported. Experiments carried out by us suggest that the collision frequency will increase dramatically if forced convection (stir or flow injection) is applied during detection. Furthermore, the collision frequency gradually increases to a maximum and then decreases, along with the increase of the convection intensity. This phenomenon is interpreted as follows: (a) there are two steps for a freely moving NP to generate a detectable collision signal. The first step is the move of NP from bulk solution to the surface of the UME which is mass transfer limited; the second step is the landing of NP on the surface of UME which is affected by many factors and is the critical step; (b) there is a barrier that must be overcame before the contact between freely moving NP and UME. Forced convection with moderate intensity can not only increase the mass transfer rate but also help to overcome this barrier and thus enhance the collision frequency; (c) the landing of NP on the surface of UME can be suppressed by stronger convections, because NP will be swept away by hydrodynamic force. PMID:26802274

  19. [The electrical conductivity of triggered lightning channel].

    PubMed

    Zhang, Hua-ming; Yuan, Ping; Su, Mao-gen; Lü, Shi-hua

    2007-10-01

    Spectra of return strokes for artificial triggered lightning were obtained by optical multi-channel analyzer (OMA) in Shandong region. Compared with previous spectra of natural lightning, additional lines of ArI 602.5 nm and ArII 666.5 nm were observed. Under the model of local thermodynamic equilibrium, electronic temperatures of the lightning channel plasma were obtained according to the relative line intensities. Meanwhile, with semi-empirical method the electron density was obtained by Halpha line Stark broadening. In combination with plasma theory, electrical conductivity of the lightning channel has been calculated for the first time, and the characteristic of conductivity for lightning channel was also discussed. The relation between the electrical conductivity of channel and the return stroke current was analyzed, providing reference data for further work on computing return stroke current. Results show that the lightning channel is a good conductor, and electrons are the main carrier of channel current. The brightness of artificial triggered lightning channel is usually higher than that of natural lightning, and its current is smaller than that of the natural lightning. PMID:18306764

  20. Stationary cylindrical vortex in a viscous electrically conducting fluid

    NASA Astrophysics Data System (ADS)

    Baikin, A. N.; Golovin, S. V.

    2013-07-01

    An exact solution of the magnetohydrodynamic equations is constructed which describes steady vortex flow in a stationary cylinder on the axis of which a conductor carrying a known current is located. The solution is obtained under the assumption that the fluid is viscous and has finite electrical conductivity and that the magnetic field has only the axial and azimuthal components in a cylindrical coordinate system. It is found that the action of the Lorentz force is compensated by changing the pressure. Fluid flow occurs from the periphery to the axis of the cylinder under a pressure gradient, with flow rotation and swirling. The fluid flow causes a concentration of the magnetic lines near the axis of the cylinder, providing an exponential decrease in the magnetic field strength with distance from the axis. This flow can be considered as a model of a local increase in the magnetic field strength due to the transfer of its force lines by the flow of the electrically conducting fluid.

  1. Details of Exact Low Prandtl Number Boundary-Layer Solutions for Forced and For Free Convection

    NASA Technical Reports Server (NTRS)

    Sparrow, E. M.; Gregg, J. L.

    1959-01-01

    A detailed report is given of exact (numerical) solutions of the laminar-boundary-layer equations for the Prandtl number range appropriate to liquid metals (0.003 to 0.03). Consideration is given to the following situations: (1) forced convection over a flat plate for the conditions of uniform wall temperature and uniform wall heat flux, and (2) free convection over an isothermal vertical plate. Tabulations of the new solutions are given in detail. Results are presented for the heat-transfer and shear-stress characteristics; temperature and velocity distributions are also shown. The heat-transfer results are correlated in terms of dimensionless parameters that vary only slightly over the entire liquid-metal range. Previous analytical and experimental work on low Prandtl number boundary layers is surveyed and compared with the new exact solutions.

  2. Inductive Measurement of Plasma Jet Electrical Conductivity

    NASA Technical Reports Server (NTRS)

    Turner, Matthew W.; Hawk, Clark W.; Litchford, Ron J.

    2005-01-01

    An inductive probing scheme, originally developed for shock tube studies, has been adapted to measure explosive plasma jet conductivities. In this method, the perturbation of an applied magnetic field by a plasma jet induces a voltage in a search coil, which, in turn, can be used to infer electrical conductivity through the inversion of a Fredholm integral equation of the first kind. A 1-inch diameter probe was designed and constructed, and calibration was accomplished by firing an aluminum slug through the probe using a light-gas gun. Exploratory laboratory experiments were carried out using plasma jets expelled from 15-gram high explosive shaped charges. Measured conductivities were in the range of 3 kS/m for unseeded octol charges and 20 kS/m for seeded octol charges containing 2% potassium carbonate by mass.

  3. Making Complex Electrically Conductive Patterns on Cloth

    NASA Technical Reports Server (NTRS)

    Chu, Andrew; Fink, Patrick W.; Dobbins, Justin A.; Lin, Greg Y.; Scully, Robert C.; Trevino, Robert

    2008-01-01

    A method for automated fabrication of flexible, electrically conductive patterns on cloth substrates has been demonstrated. Products developed using this method, or related prior methods, are instances of a technology known as 'e-textiles,' in which electrically conductive patterns ar formed in, and on, textiles. For many applications, including high-speed digital circuits, antennas, and radio frequency (RF) circuits, an e-textile method should be capable of providing high surface conductivity, tight tolerances for control of characteristic impedances, and geometrically complex conductive patterns. Unlike prior methods, the present method satisfies all three of these criteria. Typical patterns can include such circuit structures as RF transmission lines, antennas, filters, and other conductive patterns equivalent to those of conventional printed circuits. The present method overcomes the limitations of the prior methods for forming the equivalent of printed circuits on cloth. A typical fabrication process according to the present method involves selecting the appropriate conductive and non-conductive fabric layers to build the e-textile circuit. The present method uses commercially available woven conductive cloth with established surface conductivity specifications. Dielectric constant, loss tangent, and thickness are some of the parameters to be considered for the non-conductive fabric layers. The circuit design of the conductive woven fabric is secured onto a non-conductive fabric layer using sewing, embroidery, and/or adhesive means. The portion of the conductive fabric that is not part of the circuit is next cut from the desired circuit using an automated machine such as a printed-circuit-board milling machine or a laser cutting machine. Fiducials can be used to align the circuit and the cutting machine. Multilayer circuits can be built starting with the inner layer and using conductive thread to make electrical connections between layers.

  4. The electrical conductivity of sodium polysulfide melts

    SciTech Connect

    Meihui Wang

    1992-06-01

    The sodium polysulfide melt has been described by a macroscopic model. This model considers the melt to be composed of sodium cations, monosulfide anions, and neutral sulfur solvent. The transport equations of concentrated-solution theory are used to derived the governing equations for this binaryelectrolyte melt model. These equations relate measurable transport properties to fundamental transport parameters. The focus of this research is to measure the electrical conductivity of sodium polysulfide melts and calculate one of fundamental transport parameters from the experimental data. The conductance cells used in the conductivity measurements are axisymmetric cylindrical cells with a microelectrode. The electrode effects, including double-layer capacity, charge transfer resistance, and concentration overpotential, were minimized by the use of the alternating current at an adequately high frequency. The high cell constants of the conductance cells not only enhanced the experimental accuracy but also made the electrode effects negligible. The electrical conductivities of sodium polysulfide Na{sub 2}S{sub 4} and Na{sub 2}S{sub 5} were measured as a function of temperature (range: 300 to 360{degree}C). Variations between experiments were only up to 2%. The values of the Arrhenius activation energy derived from the experimental data are about 33 kJ/mol. The fundamental transport parameter which quantifies the interaction within sodium cations and monosulfide anions are of interest and expected to be positive. Values of it were calculated from the experimental conductivity data and most of them are positive. Some negative values were obtained probably due to the experimental errors of transference number, diffusion coefficient, density or conductivity data.

  5. Numerical and experimental study of flows in a rotating annulus with local convective forcing.

    NASA Astrophysics Data System (ADS)

    Scolan, Hélène; Su, Sylvie; Wright, Susie; Young, Roland M. B.; Read, Peter

    2016-04-01

    We present a numerical and experimental study of flows in a rotating annulus convectively forced by local thermal forcing via a heated annular ring at the bottom near the external wall and a cooled circular disk near the centre at the top surface of the annulus. This new configuration is a variant of the classical thermally-driven annulus analogue of the atmosphere circulation, where thermal forcing was previously applied uniformly on the sidewalls. Two vertically and horizontally displaced heat sources/sinks are arranged so that, in the absence of background rotation, statically unstable Rayleigh-Bénard convection would be induced above the source and beneath the sink, thereby relaxing strong constraints placed on background temperature gradients in previous experimental configurations to better mimic in fine local vigorous convection events in tropics and polar regions whilst also facilitating baroclinic motion in midlatitude regions in the Earth's atmosphere. By using the Met Office/ Oxford Rotating Annulus Laboratory (MORALS) code, we have investigated a series of equilibrated, 2D axisymmetric flows for a large range of dimensionless parameters and characterized them in terms of velocity and temperature fields. Several distinct and different flow regimes were identified, depending upon the rotation rate and strength of differential heating. These regimes will be presented with reference to variations of horizontal Ekman layer thickness versus the thermal boundary layer thickness and corresponding scalings for various quantities such as the azimuthal velocity or the heat transport. Experimental investigation of the same setup is carried out with a 1m diameter cylindrical container on a rotating platform: local heating is produced with an electrically heated annular ring at the bottom of the tank and cooling is imposed through a circular disk near the centre of the tank at the upper surface, cooled with circulating water. Different unstable circulation regimes

  6. A perturbation solution for forced convection in a porous-saturated duct

    NASA Astrophysics Data System (ADS)

    Hooman, K.

    2008-01-01

    Fully developed forced convection through a porous medium bounded by two isoflux parallel plates is investigated analytically on the basis of a Brinkman-Forchheimer model. The matched asymptotic expansion method is applied for small values of the Darcy number. For the case of large Darcy number the solution for the Brinkman-Forchheimer momentum equation is found in terms of an asymptotic expansion. With the velocity distribution determined, the energy equation is solved using the same asymptotic technique. The results for limiting cases are found to be in good agreement with those available in the literature and the numerical results obtained here.

  7. Heat and momentum transfer model studies applicable to once-through, forced convection potassium boiling

    NASA Technical Reports Server (NTRS)

    Sabin, C. M.; Poppendiek, H. F.

    1971-01-01

    A number of heat transfer and fluid flow mechanisms that control once-through, forced convection potassium boiling are studied analytically. The topics discussed are: (1) flow through tubes containing helical wire inserts, (2) motion of droplets entrained in vapor flow, (3) liquid phase distribution in boilers, (4) temperature distributions in boiler tube walls, (5) mechanisms of heat transfer regime change, and (6) heat transfer in boiler tubes. Whenever possible, comparisons of predicted and actual performances are made. The model work presented aids in the prediction of operating characteristics of actual boilers.

  8. A theoretical study of the spheroidal droplet evaporation in forced convection

    NASA Astrophysics Data System (ADS)

    Li, Jie; Zhang, Jian

    2014-11-01

    In many applications, the shape of a droplet may be assumed to be an oblate spheroid. A theoretical study is conducted on the evaporation of an oblate spheroidal droplet under forced convection conditions. Closed-form analytical expressions of the mass evaporation rate for an oblate spheroid are derived, in the regime of controlled mass-transfer and heat-transfer, respectively. The variation of droplet size during the evaporation process is presented in the regime of shrinking dynamic model. Comparing with the droplets having the same surface area, an increase in the aspect ratio enhances the mass evaporation rate and prolongs the burnout time.

  9. Experimental Validation Data for Computational Fluid Dynamics of Forced Convection on a Vertical Flat Plate

    SciTech Connect

    Harris, Jeff R.; Lance, Blake W.; Smith, Barton L.

    2015-08-10

    We present computational fluid dynamics (CFD) validation dataset for turbulent forced convection on a vertical plate. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions (BCs) and system response quantities (SRQs). Important inflow quantities for Reynolds-Averaged Navier-Stokes (RANS). CFD are also measured. Data are acquired at two heating conditions and cover the range 40,000 < Rex < 300,000, 357 < Reδ2 < 813, and 0.02 < Gr/Re2 < 0.232.

  10. Experimental Validation Data for Computational Fluid Dynamics of Forced Convection on a Vertical Flat Plate

    DOE PAGESBeta

    Harris, Jeff R.; Lance, Blake W.; Smith, Barton L.

    2015-08-10

    We present computational fluid dynamics (CFD) validation dataset for turbulent forced convection on a vertical plate. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions (BCs) and system response quantities (SRQs). Important inflow quantities for Reynolds-Averaged Navier-Stokes (RANS). CFD are also measured. Data are acquired at two heating conditions and cover the range 40,000 < Rex < 300,000, 357 < Reδ2 < 813, and 0.02 < Gr/Re2 < 0.232.

  11. Single-drop reactive extraction/extractive reaction with forced convective diffusion and interphase mass transfer

    NASA Technical Reports Server (NTRS)

    Kleinman, Leonid S.; Red, X. B., Jr.

    1995-01-01

    An algorithm has been developed for time-dependent forced convective diffusion-reaction having convection by a recirculating flow field within the drop that is hydrodynamically coupled at the interface with a convective external flow field that at infinity becomes a uniform free-streaming flow. The concentration field inside the droplet is likewise coupled with that outside by boundary conditions at the interface. A chemical reaction can take place either inside or outside the droplet, or reactions can take place in both phases. The algorithm has been implemented, and for comparison results are shown here for the case of no reaction in either phase and for the case of an external first order reaction, both for unsteady behavior. For pure interphase mass transfer, concentration isocontours, local and average Sherwood numbers, and average droplet concentrations have been obtained as a function of the physical properties and external flow field. For mass transfer enhanced by an external reaction, in addition to the above forms of results, we present the enhancement factor, with the results now also depending upon the (dimensionless) rate of reaction.

  12. Photovoltaic device having light transmitting electrically conductive stacked films

    DOEpatents

    Weber, Michael F.; Tran, Nang T.; Jeffrey, Frank R.; Gilbert, James R.; Aspen, Frank E.

    1990-07-10

    A light transmitting electrically conductive stacked film, useful as a light transmitting electrode, including a first light transmitting electrically conductive layer, having a first optical thickness, a second light transmitting layer, having a second optical thickness different from the optical thickness of the first layer, and an electrically conductive metallic layer interposed between and in initimate contact with the first and second layers.

  13. Role of EHD motion in the electrical conduction of liquids in a blade-plane geometry

    SciTech Connect

    Haidara, M.; Atten, P.

    1985-05-01

    A blade-plane electrode assembly is used to study electrical conduction in divergent fields and, more generally, to investigate high field conduction of dielectric liquids. The stationary current-voltage characteristics show two regimes of conduction: a quasi-ohmic regime and a V /SUP a/ one, V being the applied voltage and 3 < ..cap alpha.. < 6. The latter regime corresponds to dominance of charge injection by the blade, as revealed by the field distribution obtained by the Kerr technique. A liquid motion is induced by the Coulomb force which convects charge carriers and results in a decrease of the first transit time following the application of a voltage step. The transient injection currents exhibit a dependence upon the elapsed time during which no voltage is applied, and the possible origin of this phenomenon is discussed. Measurement of the liquid velocity by laser Doppler anemometry also exhibits two different laws of variation with applied voltage consistent with the two current regimes. In the steady-state conditions of the injection-dominant regime, the square of the measured velocity component w/sup 2/ varies as the electrical power input IV (I being the current). This is tentatively interpreted by the viscous dominated character of the induced motion.

  14. New method for electrical conductivity temperature compensation.

    PubMed

    McCleskey, R Blaine

    2013-09-01

    Electrical conductivity (κ) measurements of natural waters are typically referenced to 25 °C (κ25) using standard temperature compensation factors (α). For acidic waters (pH < 4), this can result in a large κ25 error (δκ25). The more the sample temperature departs from 25 °C, the larger the potential δκ25. For pH < 4, the hydrogen ion transport number becomes substantial and its mode of transport is different from most other ions resulting in a different α. A new method for determining α as a function of pH and temperature is presented. Samples with varying amounts of H2SO4 and NaCl were used to develop the new α, which was then applied to 65 natural water samples including acid mine waters, geothermal waters, seawater, and stream waters. For each sample, the κ and pH were measured at several temperatures from 5 to 90 °C and κ25 was calculated. The δκ25 ranged from -11 to 9% for the new method as compared to -42 to 25% and -53 to 27% for the constant α (0.019) and ISO-7888 methods, respectively. The new method for determining α is a substantial improvement for acidic waters and performs as well as or better than the standard methods for circumneutral waters. PMID:23895179

  15. Magnetic flowmeter for electrically conductive liquid

    DOEpatents

    Skladzien, Stanley B.; Raue, Donald J.

    1982-01-01

    A magnetic flowmeter includes first and second tube sections each having ls of non-magnetic material. The first tube is suitably connected to a process for passing a flow of an electrically conductive fluid to be measured. The second tube is established as a reference containing a still medium and is maintained at the same temperature as the first tube. A rotatable magnet assembly is disposed between the two tubes with at least two magnets attached to radially extending arms from a central shaft. Each magnet includes an air gap suitably sized to pass astraddle the diameter along a portion of the length of each of the two tubes. The magnets are provided in matched pairs spaced 180.degree. apart such that signals will be simultaneously generated in signal leads attached to each of the two tubes. By comparing the signals from the two tubes and varying the rotating speed of the magnet assembly until the signals are equal, or attain a maximum, the flow velocity of the fluid within the first tube can be determined. Through temperature monitoring and appropriate heaters, the two tubes are maintained at the same temperature.

  16. Magnetic flowmeter for electrically conductive liquid

    DOEpatents

    Skladzien, S.B.; Raue, D.J.

    1980-08-18

    A magnetic flowmeter includes first and second tube sections each having walls of non-magnetic material. The first tube is suitably connected to a process for passing a flow of an electrically conductive fluid to be measured. The second tube is established as a reference containing a still medium and is maintained at the same temperature as the first tube. A rotatable magnet assembly is disposed between the two tubes with at least two magnets attached to radially extending arms from a central shaft. Each magnet includes an air gap suitably sized to pass astraddle the diameter along a portion of the length of each of the two tubes. Two magnets are provided in matched pairs spaced 180/sup 0/ apart such that signals will be simultaneously generated in signal leads attached to each of the two tubes. By comparing the signals from the two tubes and varying the rotating speed of the magnet assembly until the signals are equal, or attain a maximum, the flow velocity of the fluid within the first tube can be determined. Through temperature monitoring and appropriate heaters, the two tubes are maintained at the same temperature.

  17. Dislocation electrical conductivity of synthetic diamond films

    SciTech Connect

    Samsonenko, S. N. Samsonenko, N. D.

    2009-05-15

    A relationship between the electric resistance of single-crystal homoepitaxial and polycrystalline diamond films and their internal structure has been investigated. It is established that the electrical conductivity of undoped homoepitaxial and polycrystalline diamond films is directly related to the dislocation density in them. A relation linking the resistivity {rho} ({approx}10{sup 13}-10{sup 15} {omega} cm) with the dislocation density {gamma} ({approx}10{sup 14}-4 x 10{sup 16} m{sup -2}) is obtained. The character of this correlation is similar for both groups of homoepitaxial and polycrystalline diamond films. Thin ({approx}1-8 {mu}m) homoepitaxial and polycrystalline diamond films with small-angle dislocation boundaries between mosaic blocks exhibit dislocation conductivity. The activation energy of dislocation acceptor centers was calculated from the temperature dependence of the conductivity and was found to be {approx}0.3 eV. The conduction of thick diamond films (h > 10 {mu}m) with the resistivity {rho} {approx} 10{sup 8} {omega} cm is determined by the conduction of intercrystallite boundaries, which have a nondiamond hydrogenated structure. The electronic properties of the diamond films are compared with those of natural semiconductor diamonds of types IIb and Ic, in which dislocation acceptor centers have activation energies in the range 0.2-0.35 eV and are responsible for hole conduction.

  18. Anisotropy of electrical conductivity in dry olivine

    SciTech Connect

    Du Frane, W L; Roberts, J J; Toffelmier, D A; Tyburczy, J A

    2005-04-13

    [1] The electrical conductivity ({sigma}) was measured for a single crystal of San Carlos olivine (Fo{sub 89.1}) for all three principal orientations over oxygen fugacities 10{sup -7} < fO{sub 2} < 10{sup 1} Pa at 1100, 1200, and 1300 C. Fe-doped Pt electrodes were used in conjunction with a conservative range of fO{sub 2}, T, and time to reduce Fe loss resulting in data that is {approx}0.15 log units higher in conductivity than previous studies. At 1200 C and fO{sub 2} = 10{sup -1} Pa, {sigma}{sub [100]} = 10{sup -2.27} S/m, {sigma}{sub [010]} = 10{sup -2.49} S/m, {sigma}{sub [001]} = 10{sup -2.40} S/m. The dependences of {sigma} on T and fO{sub 2} have been simultaneously modeled with undifferentiated mixed conduction of small polarons and Mg vacancies to obtain steady-state fO{sub 2}-independent activation energies: Ea{sub [100]} = 0.32 eV, Ea{sub [010]} = 0.56 eV, Ea{sub [001]} = 0.71 eV. A single crystal of dry olivine would provide a maximum of {approx}10{sup 0.4} S/m azimuthal {sigma} contrast for T < 1500 C. The anisotropic results are combined to create an isotropic model with Ea = 0.53 eV.

  19. Electrically conducting superhydrophobic microtextured carbon nanotube nanocomposite

    NASA Astrophysics Data System (ADS)

    Caffrey, Paul O.; Gupta, Mool C.

    2014-09-01

    We report a simple and inexpensive method of producing an electrically conductive superhydrophobic polymer surface by adding multiwall carbon nanotubes directly into the polymer poly(dimethylsiloxane) (PDMS) matrix and replicating micro/nanotexture using a replication master prepared by ultrafast-laser microtexturing process. No additional coatings on conducting PDMS are required to achieve water contact angles greater than 161°. The conductivity can be controlled by changing the percent MWCNT added to PDMS and at a bulk loading of 4.4 wt% we report a conductivity improvement over pure PDMS by a factor of more than 1011 with electrical resistivity ρ = 761 Ω cm. This combined behavior of a conductive, superhydrophobic nanocomposite has exciting applications for allowing a new class of enclosures providing EMI shielding, water repellency and sensing to provide built-in temperature feedback. The effect of temperature on the nanocomposite was investigated and a negative temperature coefficient of resistance (-0.037 Ω/K) similar to that of a thermistor was observed.

  20. The effects of buoyancy on the critical heat flux in forced convection

    NASA Technical Reports Server (NTRS)

    Brusstar, Matthew J.; Merte, Herman, Jr.

    1993-01-01

    The critical heat flux (CHF) in forced convection over a flat surface at relatively low flow velocities has been found, not unexpectedly, to depend upon the orientation of the buoyancy. The CHF for R-113 was measured at various heating surface orientations for test section Reynolds numbers ranging between 3000 and 6500. In this flow range, the buoyancy force acting on the vapor generally dominates over the flow inertia, yet the inertia would still be substantial were gravity to be reduced. In the experiments of this study, the CHF is determined for heating surface orientations ranging from 0 deg to 360 deg, for flow velocities between 4 cm/s and 35 cm/s, and for subcoolings between 2.8 C and 22.2 C. The results presented here demonstrate the strong influence of buoyancy at low flow velocities, which diminishes as the flow velocity and subcooling are increased.

  1. Fundamental Study of Local Heat Transfer in Forced Convective Boiling of Ammonia on Vertical Flat Plate

    NASA Astrophysics Data System (ADS)

    Kim, Jeong-Hun; Arima, Hirofumi; Ikegami, Yasuyuki

    In the present study, the fundamental experiments that investigate characteristics of local heat transfer in forced convective boiling on vertical flat plate with 2-mm channel height are taken to realize plate type compact evaporator for OTEC or STEC. The experiments are performed with ammonia as the working fluid. The experiments are also carried out with the following test conditions; saturated pressure = 0.7, 0.8, 0.9 MPa, mass flux = 7.5, 10, 15 kg/(m2•s), heat flux = 15, 20, 25 kW/m2 and inlet quality = 0.1 ~ 0.4 [-]. The result shows that the wall superheated temperature of forced convective boiling is lower than that of pool boiling. And the heat transfer coefficient increases with an increase in quality and the decrease in the local heat flux and saturated pressure for prescribed experimental conditions. However, local heat transfer coefficients are not affected by mass fluxes in the prescribed experimental conditions. An empirical correlation that can predict the local heat transfer coefficient on vertical flat plate within experimental conditions is also proposed.

  2. Temporal stability of electrical conductivity in a sandy soil

    NASA Astrophysics Data System (ADS)

    Pedrera-Parrilla, Aura; Brevik, Eric C.; Giráldez, Juan V.; Vanderlinden, Karl

    2016-07-01

    Understanding of soil spatial variability is needed to delimit areas for precision agriculture. Electromagnetic induction sensors which measure the soil apparent electrical conductivity reflect soil spatial variability. The objectives of this work were to see if a temporally stable component could be found in electrical conductivity, and to see if temporal stability information acquired from several electrical conductivity surveys could be used to better interpret the results of concurrent surveys of electrical conductivity and soil water content. The experimental work was performed in a commercial rainfed olive grove of 6.7 ha in the `La Manga' catchment in SW Spain. Several soil surveys provided gravimetric soil water content and electrical conductivity data. Soil electrical conductivity values were used to spatially delimit three areas in the grove, based on the first principal component, which represented the time-stable dominant spatial electrical conductivity pattern and explained 86% of the total electrical conductivity variance. Significant differences in clay, stone and soil water contents were detected between the three areas. Relationships between electrical conductivity and soil water content were modelled with an exponential model. Parameters from the model showed a strong effect of the first principal component on the relationship between soil water content and electrical conductivity. Overall temporal stability of electrical conductivity reflects soil properties and manifests itself in spatial patterns of soil water content.

  3. Damage Detection in Electrically Conductive Structures

    NASA Astrophysics Data System (ADS)

    Anderson, Todd A.

    2002-12-01

    High-technology systems are in need of structures that perform with increased functionality and a reduction in weight, while simultaneously maintaining a high level of performance and reliability. To accomplish this, structural elements must be designed more efficiently and with increased functionality, thereby creating multifunctional structures (MFS). Through the addition of carbon fibers, nanotubes, or particles, composite structures can be made electrically conductive while simultaneously increasing their strength and stiffness to weight ratios. Using the electrical properties of these structures for the purpose of damage detection and location for health and usage monitoring is of particular interest for aerospace structures. One such method for doing this is Electrical Impedance Tomography (EIT). With EIT, an electric current is applied through a pair of electrodes and the electric potential is recorded at other monitoring electrodes around the area of study. An inverse solution of the governing Maxwell equations is then required to determine the conductivities of discrete areas within the region of interest. However, this method is nearly ill-posed and computationally intensive as it focuses on imaging small changes in conductivity within the region of interest. For locating damage in a medium with an otherwise homogeneous conductivity, an alternative approach is to search for parameters such as the damage location and size. Towards those ends, this study develops an Artificial Neural Network (ANN) to determine the state of an electrically conductive region based on applied reference current and electrical potentials at electrodes around the periphery of the region. A significant benefit of the ANN approach is that once trained, the solution of an inverse problem does not require costly computations of the inverse problem. This method also takes advantage of the pattern recognition abilities of neural networks and is a robust solution method in the presence

  4. Electrically conductive polyurethanes for biomedical applications

    NASA Astrophysics Data System (ADS)

    Williams, Charles M.; Nash, M. A.; Poole-Warren, Laura A.

    2005-02-01

    Electrical interfacing with neural tissue poses significant problems due to host response to the material. This response generally leads to fibrous encapsulation and increased impedance across the electrode. In neural electrodes such as cochlear implants, an elastomeric material like silicone is used as an insulator for the metal electrode. This project ultimately aims to produce a polymer electrode with elastomeric mechanical properties, metal like conductivity and capability. The approach taken was to produce a nanocomposite elastomeric material based on polyurethane (PU) and carbon nanotubes. Carbon nanotubes are ideal due to their high aspect ratio as well as being a ballistic conductor. The choice of PU is based on its elastomeric properties, processability and biocompatibility. Multi-walled nanotubes (MWNTs) were dispersed ultrasonically in various dispersive solutions before being added at up to 20wt% to a 5wt% PU (Pellethane80A) in Dimethylacetamide (DMAc). Films were then solvent cast in a vacuum oven overnight. The resulting films were tested for conductivity using a two-probe technique and mechanically tested using an Instron tensiometer. The percolation threshold (p) of the PU/MWNT films occurred at loadings of between 7 and 10 wt% in this polymer system. Conductivity of the films (above p) was comparable to those for similar systems reported in the literature at up to approximately 7x10-2 Scm-1. Although PU stiffness increased with increased %loading of nanotubes, all composites were highly flexible and maintained elastomeric properties. From these preliminary results we have demonstrated electrical conductivity. So far it is evident that a superior percolation threshold is dependent on the degree of dispersion of the nanotubes. This has prompted work into investigating other preparations of the films, including melt-processing and electrospinning.

  5. Experimental study of forced convection heat transfer during upward and downward flow of helium at high pressure and high temperature

    SciTech Connect

    Francisco Valentin; Narbeh Artoun; Masahiro Kawaji; Donald M. McEligot

    2015-08-01

    Fundamental high pressure/high temperature forced convection experiments have been conducted in support of the development of a Very High Temperature Reactor (VHTR) with a prismatic core. The experiments utilize a high temperature/high pressure gas flow test facility constructed for forced convection and natural circulation experiments. The test section has a single 16.8 mm ID flow channel in a 2.7 m long, 108 mm OD graphite column with four 2.3kW electric heater rods placed symmetrically around the flow channel. This experimental study presents the role of buoyancy forces in enhancing or reducing convection heat transfer for helium at high pressures up to 70 bar and high temperatures up to 873 degrees K. Wall temperatures have been compared among 10 cases covering the inlet Re numbers ranging from 500 to 3,000. Downward flows display higher and lower wall temperatures in the upstream and downstream regions, respectively, than the upward flow cases due to the influence of buoyancy forces. In the entrance region, convection heat transfer is reduced due to buoyancy leading to higher wall temperatures, while in the downstream region, buoyancyinduced mixing causes higher convection heat transfer and lower wall temperatures. However, their influences are reduced as the Reynolds number increases. This experimental study is of specific interest to VHTR design and validation of safety analysis codes.

  6. Single-drop reactive extraction/extractive reaction with forced convective diffusion and interphase mass transfer

    NASA Technical Reports Server (NTRS)

    Kleinman, Leonid S.; Reed, X. B., Jr.

    1995-01-01

    An algorithm has been developed for the forced convective diffusion-reaction problem for convection inside and outside a droplet by a recirculating flow field hydrodynamically coupled at the droplet interface with an external flow field that at infinity becomes a uniform streaming flow. The concentration field inside the droplet is likewise coupled with that outside by boundary conditions at the interface. A chemical reaction can take place either inside or outside the droplet or reactions can take place in both phases. The algorithm has been implemented and results are shown here for the case of no reaction and for the case of an external first order reaction, both for unsteady behavior. For pure interphase mass transfer, concentration isocontours, local and average Sherwood numbers, and average droplet concentrations have been obtained as a function of the physical properties and external flow field. For mass transfer enhanced by an external reaction, in addition to the above forms of results, we present the enhancement factor, with the results now also depending upon the (dimensionless) rate of reaction.

  7. Non-Darcian forced convection analysis in an annulus partially filled with a porous material

    SciTech Connect

    Chikh, S.; Boumedien, A.; Bouhadef, K.; Lauriat, G.

    1995-12-01

    Numerical solutions are presented for fully developed forced convection in concentric annuli partially filled with a porous medium. The porous medium is attached at the inner cylinder, which is maintained at uniform heat flux or at uniform wall temperature while the outer cylinder is adiabatic. The Brinkman-Forchheimer-extended Darcy model was used to model the flow inside the porous medium. The dependence of the fluid flow and heat transfer on several parameters of the problem is thoroughly documented. The inertia coefficient at which the inertial effects reduce the flow rate by 5% is determined as a function of the Darcy number for various thicknesses of the porous substrate. It is also shown that a critical thickness at which the value of the Nusselt number reaches a minimum does not exist if the effective thermal conductivity of the fluid-saturated porous medium is much higher than the fluid conductivity.

  8. Finite difference analysis for developing laminar flow in circular tubes applied to forced and combined convection

    NASA Astrophysics Data System (ADS)

    Collins, M. W.

    1980-03-01

    The complete two-dimensional partial differential equations for developing laminar flow in a circular tube have been treated by a finite difference analysis. Property variation with temperature, especially that of viscosity, is allowed for in a flexible manner. The continuity and momentum equations, and then the energy equations, are solved by direct elimination at each axial step, and a marching procedure used in the axial direction. The stepwise energy balance is rigidly satisfied throughout by using it as a constituent equation in place of the 'explicit' wall thermal boundary condition normally used. The analysis predicts the complete developing hydrodynamic and thermal fields, together with friction factors and heat transfer coefficients. It has been tested for a range of fluid velocity and thermal boundary conditions and for various fluids, including high viscosity oils, water and air. Predictions for constant wall temperature presented here are for forced and combined convection and are compared with experimental data of Test and Zeldin and Schmidt.

  9. Effect of finite length on forced convection heat transfer from cylinders

    NASA Astrophysics Data System (ADS)

    Quarmby, A.; Al-Fakhri, A. A. M.

    1980-04-01

    Forced convection heat transfer from single cylinders of finite length is investigated experimentally with particular reference to the effect of aspect (length/diameter) ratio of the cylinder. It is found that for aspect ratios greater than 4 there is little further effect as aspect ratio increases to infinity. The disagreement between the correlations proposed by Zukauskas (1972) and Morgan (1975) is considered and resolved in favor of the Zukauskas correlation. A correlation is proposed for heat transfer from cylinders of low aspect ratio which in the limit agrees with the correlation for large aspect ratios and with the generally accepted correlation for turbulent heat transfer from isothermal flat plates for small aspect ratios.

  10. Application of a finite volume based method of lines to turbulent forced convection in circular tubes

    SciTech Connect

    Campo, A.; Tebeest, K.; Lacoa, U.; Morales, J.C.

    1996-10-01

    A semianalytic analysis of in-tube turbulent forced convection is performed whose special computational feature is the combination of the method of lines, the finite volume technique, and a radial coordinate transformation. First, a numerical solution of the momentum equation was obtained by a simple Runge-Kutta integration scheme. Second, the energy equation was reformulated into a system of ordinary differential equations of first order. Each equation in the system controls the temperature along a line in a mesh consisting of concentric lines. Reliable analytic solutions for the temperature distribution of fluids in the region of thermal development can be determined for combinations of Reynolds and Prandtl numbers. Predicted results for the distributions of mean bulk temperature and local Nusselt numbers for air, water, and oils compare satisfactorily with the available experimental data.

  11. Forced convection analysis for generalized Burgers nanofluid flow over a stretching sheet

    NASA Astrophysics Data System (ADS)

    Khan, Masood; Khan, Waqar Azeem

    2015-10-01

    This article reports the two-dimensional forced convective flow of a generalized Burgers fluid over a linearly stretched sheet under the impacts of nano-sized material particles. Utilizing appropriate similarity transformations the coupled nonlinear partial differential equations are converted into a set of coupled nonlinear ordinary differential equations. The analytic results are carried out through the homotopy analysis method (HAM) to investigate the impact of various pertinent parameters for the velocity, temperature and concentration fields. The obtained results are presented in tabular form as well as graphically and discussed in detail. The presented results show that the rate of heat transfer at the wall and rate of nanoparticle volume fraction diminish with each increment of the thermophoresis parameter. While incremented values of the Brownian motion parameter lead to a quite opposite effect on the rates of heat transfer and nanoparticle volume fraction at the wall.

  12. Effect of Heated Perimeter on Forced Convection Heat Transfer of he i at a Supercritical Pressure

    NASA Astrophysics Data System (ADS)

    Doi, D.; Shiotsu, M.; Shirai, Y.; Hama, K.

    2008-03-01

    The forced convection heat transfer coefficients were measured on two pairs of test plates all 6.0 mm in width and located face to face on inner walls of a rectangular duct. Each pair having length of 20 mm and 80 mm, respectively, was connected in series electrically. The rectangular duct was 420 mm in length and 5 mm×6 mm in inner cross section. The experiments were performed for inlet temperatures from 2.2 to 6.5 K, flow velocities from 0.1 to 5.6 m/s, and at a supercritical pressure of 2.8 atm. Comparison of the obtained Nusselt numbers with the former results with a single test plate showed the clear effect of a heated perimeter. Non-dimensional heat transfer equation including the effect of heated perimeter is presented.

  13. Stability improvement of AC superconducting magnet by forced-convection cooling

    SciTech Connect

    Ishigohka, T.; Kasuya, A.; Ninomiya, A.

    1996-07-01

    The authors propose a new improved cooling system of an AC(50/60Hz) superconducting magnet introducing a forced-convection flow of liquid helium. In this system, the flow through the cooling channel between the winding layers is generated by a screw rotating in a cylinder surrounding the magnet. A small experimental device composed of an AC superconducting magnet and a rotating screw was manufactured. The screw was rotated by an extended driving shaft. The experimental result shows that the stability of the magnet is improved by the rotation of the screw. That is, the thermal disturbance (heater input power) which generates the quench of the magnet increases as the rotational speed of the screw does. It is expected that this technique can be successfully applied to superconducting AC power apparatuses as transformers or reactors.

  14. Numerical simulation of combined natural and forced convection during thermal-hydraulic transients. [LMFBR

    SciTech Connect

    Domanus, H.M.; Sha, W.T.

    1981-01-01

    The single-phase COMMIX (COMponent MIXing) computer code performs fully three-dimensional, transient, thermal-hydraulic analyses of liquid-sodium LMFBR components. It solves the conservation equations of mass, momentum, and energy as a boundary-value problem in space and as an initial-value problem in time. The concepts of volume porosity, surface permeability and distributed resistance, and heat source have been employed in quasi-continuum (rod-bundle) applications. Results from three transient simulations involving forced and natural convection are presented: (1) a sodium-filled horizontal pipe initially of uniform temperature undergoing an inlet velocity rundown transient, as well as an inlet temperature transient; (2) a 19-pin LMFBR rod bundle undergoing a velocity transient; and, (3) a simulation of a water test of a 1/10-scale outlet plenum undergoing both velocity and temperature transients.

  15. Method of forming an electrically conductive cellulose composite

    DOEpatents

    Evans, Barbara R.; O'Neill, Hugh M.; Woodward, Jonathan

    2011-11-22

    An electrically conductive cellulose composite includes a cellulose matrix and an electrically conductive carbonaceous material incorporated into the cellulose matrix. The electrical conductivity of the cellulose composite is at least 10 .mu.S/cm at 25.degree. C. The composite can be made by incorporating the electrically conductive carbonaceous material into a culture medium with a cellulose-producing organism, such as Gluconoacetobacter hansenii. The composites can be used to form electrodes, such as for use in membrane electrode assemblies for fuel cells.

  16. Diabatically Forced Frontogenesis Near Surface As Trigger For The Release of Strong Convection

    NASA Astrophysics Data System (ADS)

    Kurz, Manfred

    One prerequisite for the formation of mesoscale convective systems is the existance of moist potentially unstable air masses in the lower troposphere. For the release of the instability, however, often an ascending motion is necessary in order to destroy stable layers on top of the moist air which would prevent convection, and to bring the air to saturation. In this respect the macroscale ascent ahead of an approaching upper trough may function as trigger for the release of convection. Another favourable process is the ascending motion of the warm air within circulations across a frontal zone which undergoes a frontogenesis either in the horizontal wind field or by diabatic effects. During summer time real fronts between different air masses are often ill defined over the continent, and circulatory motions in their neighbourhood remain rather weak. There is, however, a mechanism which may lead to the formation of a very strong temperature contrast near surface within short time. That happens at the edge of larger cloud and precipitation areas during day time due to the different diabatic heat fluxes across the cloud edge: Whereas the temperature below the cloud masses remains more or less constant or is even reduced by evaporation of falling rain, it rapidly increases due to heating from the ground in the area with no or only few clouds. As consequence of this diabatically forced frontogenesis a solenoidally direct circulation across the newly established frontal zone is released with ascent of the heated air, descent of the cooler air and an ageostrophic motion from the cold towards the warm air near surface. At the same time the pressure rises - at least relatively - in the cold air and falls in the warm air so that a pressure gradient is built up between both air masses. If the warm air is potentially unstable, the ascent within the circulation may lead to the release of the instability and the formation of convective clouds ahead of the cloud edge and parallel

  17. Electrical conduction in organic charge transfer complexes under pressure: A theoretical view

    NASA Astrophysics Data System (ADS)

    Singh, Yadunath

    2016-05-01

    We propose a theoretical view of temperature dependent electrical conductivity in organic charge transfer complexes and radical ion salts. Understanding of the basic conduction mechanism under high pressure in these systems is our aim. The mechanism is discussed mainly on the basis of molecular orbital overlap theory, role of charge transfer forces and charge density waves etc.

  18. Free and forced convective cooling of pipe-type electric cables. Volume 1: forced cooling of cables. Final report

    SciTech Connect

    Chato, J.C.; Crowley, J.M.

    1981-05-01

    A multi-faceted research program has been performed to investigate in detail several aspects of free and forced convective cooling of underground electric cable systems. There were two main areas of investigation. The first one reported in this volume dealt with the fluid dynamic and thermal aspects of various components of the cable system. In particular, friction factors for laminar flow in the cable pipes with various configurations were determined using a finite element technique; the temperature distributions and heat transfer in splices were examined using a combined analytical numerical technique; the pressure drop and heat transfer characteristics of cable pipes in the transitional and turbulent flow regime were determined experimentally in a model study; and full-scale model experimental work was carried out to determine the fluid dynamic and thermal characteristics of entrance and exit chambers for the cooling oil. The second major area of activity, reported in volume 2, involved a feasibility study of an electrohydrodynamic pump concept utilizing a traveling electric field generated by a pumping cable. Experimental studies in two different configurations as well as theoretical calculations showed that an electrohydrodynamic pump for the moving of dielectric oil in a cable system is feasible.

  19. Determination of forced convection parameters by interferometric imaging of the concentration field during growth of KDP crystals

    NASA Astrophysics Data System (ADS)

    Verma, Sunil; Muralidhar, K.

    2011-07-01

    Growth of a potassium dihydrogen phosphate (KDP) crystal from its aqueous solution has been considered under forced convection conditions. The KDP crystal is grown in a conventional top hanging geometry. Forced convection conditions are created by rotating the crystal about a vertical axis. The rotational RPM is varied in a cycle, creating an accelerated rotation (AR) paradigm. The effect of varying the rotational RPM on the concentration field around the crystal was investigated. Mach-Zehnder interferometry was adopted as an optical technique to image the evolving concentration fields. Six different experiments were performed to obtain the specific set of time periods and rotation rates of the acceleration cycle that result in a uniform concentration field around the growing crystal. The Reynolds number, an index of the strength of forced convection, was optimized through the experiments. The optimized parameters of the accelerated rotation cycle were found to be as follows: maximum rotation rate of 32 RPM, spin up period=40 s, spin down period=40 s, steady period=40 s, and stationary period=40 s. The parametric study further revealed that concentration was highly sensitive to the maximum rotation rate adopted during the AR cycle. It did not depend crucially on the time periods that could be varied by as much as ±25% around the respective average values. Finally, a KDP crystal was grown using the optimized forced convection parameters and the crystal quality was found to be good.

  20. Energetic dynamics of a rotating horizontal convection model with wind forcing

    NASA Astrophysics Data System (ADS)

    Zemskova, Varvara; White, Brian; Scotti, Alberto

    2015-11-01

    We present a new test case for rotating horizontal convection, where the flow is driven by differential buoyancy forcing along a horizontal surface. This simple model is used to understand and quantify the influence of surface heating and cooling and wind stress on the Meridional Overturning Circulation. The domain is a rectangular basin with surface cooling at both ends (the poles) and surface warming in the middle (equatorial) region. To model the effect of the Antarctic Circumpolar Current, reentrant channel is placed near the Southern pole. Free-slip boundary conditions are imposed in the closed box, while zonally periodic boundary conditions are enforced in the channel. The problem is solved numerically using a 3D DNS model based on a finite-volume AMR solver for the Boussinesq Navier-Stokes equations with rotation. The relative contributions of surface buoyancy and wind forcing and the energetic balance are analyzed at a Rayleigh number of 108 and a relatively high aspect ratio of [5, 10, 1] in zonal, meridional and vertical directions, respectively. The overall dynamics, including large-scale overturning, baroclinic eddying, and turbulent mixing are investigated using the local Available Potential Energy framework introduced in [Scotti and White, J. Fluid Mech., 2014]. This research is part of the Blue Waters sustained-petascale computing project, supported by the NSF (awards OCI-0725070, ACI-1238993 and ACI-14-44747) and the state of Illinois.

  1. Polyelectrolyte multilayers impart healability to highly electrically conductive films.

    PubMed

    Li, Yang; Chen, Shanshan; Wu, Mengchun; Sun, Junqi

    2012-08-28

    Healable, electrically conductive films are fabricated by depositing Ag nanowires on water-enabled healable polyelectrolyte multilayers. The easily achieved healability of the polyelectrolyte multilayers is successfully imparted to the Ag nanowire layer. These films conveniently restore electrical conductivity lost as a result of damage by cuts several tens of micrometers wide when water is dropped on the cuts. PMID:22807199

  2. Improving the electrical conductivity of PEDOT:PSS films by binary secondary doping

    NASA Astrophysics Data System (ADS)

    Zhu, Zhengyou; Liu, Congcong; Xu, Jingkun; Jiang, Qinglin; Shi, Hui; Liu, Endou

    2016-01-01

    In this work, the electrical conductivity of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) films was effectively enhanced by binary secondary doping. Initially, doping with 5 vol.% dimethyl sulfoxide (DMSO) improved the electrical conductivity from 0.3 S cm-1 to 437 S cm-1 and a further increase to 950 S cm-1 was achieved by adding LiClO4. The conductivity value we report here is one of the highest reported for pretreated PEDOT:PSS films. The obtained maximum electrical conductivity is almost 3000 times higher than that shown by pristine PEDOT:PSS films. The increase in the electrical conductivity is ascribed to the synergistic effect of the two dopants. Fourier transform infrared spectra indicated the absence of any changes to the chemical structure of PEDOT:PSS. Atomic force microscopy images demonstrate an increased surface roughness and suggest the occurrence of conformational changes of PEDOT chains from the coiled to coil-extended one, which is the key reason for the electrical conductivity enhancement. The pretreatments we propose here are rapid, simple and effective for the large-scale preparation of high-conductivity PEDOT:PSS films. [Figure not available: see fulltext.

  3. Hot stage and sample cell design for the solidification of transparent materials with and without forced convection

    NASA Technical Reports Server (NTRS)

    Kaukler, W. F.

    1984-01-01

    A temperature gradient stage design for optical microscopy is described. Exceptional thermal stability is the major feature. The stage is used to study crystal growth phenomena occurring at the solid-liquid interface. The apparatus is designed to use transparent organic solutions as models for the study of metal-like solidification. The stage provides a controlled thermal environment for unidirectional solidification of low melting temperature materials. Freezing rate is regulated by mechanically sliding in the stage a thin glass cell containing the materials being studied. Two cell assemblies are described. One type is used for convection-free and the other for controlled forced convection studies of the solidification interface.

  4. Investigation of combined free and forced convection in a 2 x 6 rod bundle during controlled flow transients

    SciTech Connect

    Bates, J.M.; Khan, E.U.

    1980-10-01

    An experimental study was performed to obtain local fluid velocity and temperature measurements in the mixed (combined free and forced) convection regime for specific flow coastdown transients. A brief investigation of steady-state flows for the purely free-convection regime was also completed. The study was performed using an electrically heated 2 x 6 rod bundle contained in a flow housing. In addition a transient data base was obtained for evaluating the COBRA-WC thermal-hydraulic computer program (a modified version of the COBRA-IV code).

  5. Conceptual Design of Forced Convection Molten Salt Heat Transfer Testing Loop

    SciTech Connect

    Manohar S. Sohal; Piyush Sabharwall; Pattrick Calderoni; Alan K. Wertsching; S. Brandon Grover

    2010-09-01

    This report develops a proposal to design and construct a forced convection test loop. A detailed test plan will then be conducted to obtain data on heat transfer, thermodynamic, and corrosion characteristics of the molten salts and fluid-solid interaction. In particular, this report outlines an experimental research and development test plan. The most important initial requirement for heat transfer test of molten salt systems is the establishment of reference coolant materials to use in the experiments. An earlier report produced within the same project highlighted how thermophysical properties of the materials that directly impact the heat transfer behavior are strongly correlated to the composition and impurities concentration of the melt. It is therefore essential to establish laboratory techniques that can measure the melt composition, and to develop purification methods that would allow the production of large quantities of coolant with the desired purity. A companion report describes the options available to reach such objectives. In particular, that report outlines an experimental research and development test plan that would include following steps: •Molten Salts: The candidate molten salts for investigation will be selected. •Materials of Construction: Materials of construction for the test loop, heat exchangers, and fluid-solid corrosion tests in the test loop will also be selected. •Scaling Analysis: Scaling analysis to design the test loop will be performed. •Test Plan: A comprehensive test plan to include all the tests that are being planned in the short and long term time frame will be developed. •Design the Test Loop: The forced convection test loop will be designed including extensive mechanical design, instrument selection, data acquisition system, safety requirements, and related precautionary measures. •Fabricate the Test Loop. •Perform the Tests. •Uncertainty Analysis: As a part of the data collection, uncertainty analysis will

  6. Electrical conductivity of zirconia stabilized with scandia and yttria

    SciTech Connect

    Kaneko, Hiroyuki; Jin, Fuxue; Taimatsu, Hitoshi . Dept. of Materials Engineering and Applied Chemistry); Kusakabe, Hirotatsu . Tsukuba Research Lab.)

    1993-03-01

    Electrical conductivity of zirconia stabilized with scandia and yttria (Sc[sub 2]O[sub 3] + Y[sub 2]O[sub 3] = 8 mol%) has been measured by the complex impedance method in the temperature range 573 to 1,173 K. With increasing Sc[sub 2]O[sub 3] concentration, electrical conductivity increases at temperatures above 640K, but it decreases below this temperature. Electrical conductivity in the electrolytes examined is a result of two processes: an activation energy of 59 to 79 kJ/mol predominant at high temperatures and an activation energy of 109 to 125 kJ/mol predominant at low temperatures.

  7. Skin-friction drag analysis from the forced convection modeling in simplified underwater swimming.

    PubMed

    Polidori, G; Taïar, R; Fohanno, S; Mai, T H; Lodini, A

    2006-01-01

    This study deals with skin-friction drag analysis in underwater swimming. Although lower than profile drag, skin-friction drag remains significant and is the second and only other contribution to total drag in the case of underwater swimming. The question arises whether varying the thermal gradient between the underwater swimmer and the pool water may modify the surface shear stress distribution and the resulting skin-friction drag acting on a swimmer's body. As far as the authors are aware, such a question has not previously been addressed. Therefore, the purpose of this study was to quantify the effect of this thermal gradient by using the integral formalism applied to the forced convection theory. From a simplified model in a range of pool temperatures (20-30 degrees C) it was demonstrated that, whatever the swimming speeds, a 5.3% reduction in the skin-friction drag would occur with increasing average boundary-layer temperature provided that the flow remained laminar. However, as the majority of the flow is actually turbulent, a turbulent flow analysis leads to the major conclusion that friction drag is a function of underwater speed, leading to a possible 1.5% reduction for fast swimming speeds above 1m/s. Furthermore, simple correlations between the surface shear stress and resulting skin-friction drag are derived in terms of the boundary-layer temperature, which may be readily used in underwater swimming situations. PMID:16153653

  8. Nanofluid flow and forced convection heat transfer over a stretching surface considering heat source

    NASA Astrophysics Data System (ADS)

    Mohammadpour, M.; Valipour, P.; Shambooli, M.; Ayani, M.; Mirparizi, M.

    2015-07-01

    In this paper, magnetic field effects on the forced convection flow of a nanofluid over a stretching surface in the presence of heat generation/absorption are studied. The equations of continuity, momentum and energy are transformed into ordinary differential equations and solved numerically using the fourth-order Runge-Kutta integration scheme featuring the shooting technique. Different types of nanoparticles as copper (Cu), silver (Ag), alumina (Al2O3) and titania (TiO2) with water as their base fluid has been considered. The influence of significant parameters, such as magnetic parameter, volume fraction of the nanoparticles, heat generation/absorption parameter, velocity ratio parameter and temperature index parameter on the flow and heat transfer characteristics are discussed. The results show that the values of temperature profiles increase with increasing heat generation/absorption and volume fraction of the nanoparticles but they decrease with increasing velocity ratio parameter and temperature index parameter. Also, it can be found that selecting silver as nanoparticle leads to the highest heat transfer enhancement.

  9. Regressed relations for forced convection heat transfer in a direct injection stratified charge rotary engine

    NASA Technical Reports Server (NTRS)

    Lee, Chi M.; Schock, Harold J.

    1988-01-01

    Currently, the heat transfer equation used in the rotary combustion engine (RCE) simulation model is taken from piston engine studies. These relations have been empirically developed by the experimental input coming from piston engines whose geometry differs considerably from that of the RCE. The objective of this work was to derive equations to estimate heat transfer coefficients in the combustion chamber of an RCE. This was accomplished by making detailed temperature and pressure measurements in a direct injection stratified charge (DISC) RCE under a range of conditions. For each specific measurement point, the local gas velocity was assumed equal to the local rotor tip speed. Local physical properties of the fluids were then calculated. Two types of correlation equations were derived and are described in this paper. The first correlation expresses the Nusselt number as a function of the Prandtl number, Reynolds number, and characteristic temperature ratio; the second correlation expresses the forced convection heat transfer coefficient as a function of fluid temperature, pressure and velocity.

  10. Residual stress measurements in forced convective quenched steel bars by means of neutron diffraction

    SciTech Connect

    Hernandez-Morales, B.; Hawbolt, B.E.; Brimacombe, J.K.

    1996-12-31

    The residual stress distributions in 38.1 mm-dia., forced convective quenched bars of interstitial-free (IF), 1045 carbon, and alloyed steels were determined by neutron diffraction. The IF and 1045 carbon steel quenched bars exhibited compressive axial and circumferential (hoop) residual stresses near the surface and tensile values at the center. The radial residual stresses were tensile at all radial positions, decreasing towards zero near the surface. In contrast, the measured axial and circumferential components of the residual stress tensor in the alloyed eutectoid steel quenched bar were tensile near the surface and decreased to compressive values at the center. The radial component showed a maximum compressive value at the center and approached zero close to the surface. Metallographic analysis and hardness testing of the three steel specimens, revealed that the IF steel had transformed completely to ferrite, while the 1045 carbon steel bar transformed to martensite near the surface and a mixture of pearlite, ferrite and martensite at the center. On the other hand, the alloyed eutectoid steel specimen transformed entirely to martensite with small amounts of bainite near the center of the rod. The observed differences in the residual stress distributions in the three steels were explained based on the sequence of phase transformations that took place during quenching.

  11. Multirelaxation-time lattice Boltzmann model for droplet heating and evaporation under forced convection.

    PubMed

    Albernaz, Daniel; Do-Quang, Minh; Amberg, Gustav

    2015-04-01

    We investigate the evaporation of a droplet surrounded by superheated vapor with relative motion between phases. The evaporating droplet is a challenging process, as one must take into account the transport of mass, momentum, and heat. Here a lattice Boltzmann method is employed where phase change is controlled by a nonideal equation of state. First, numerical simulations are compared to the D(2) law for a vaporizing static droplet and good agreement is observed. Results are then presented for a droplet in a Lagrangian frame under a superheated vapor flow. Evaporation is described in terms of the temperature difference between liquid-vapor and the inertial forces. The internal liquid circulation driven by surface-shear stresses due to convection enhances the evaporation rate. Numerical simulations demonstrate that for higher Reynolds numbers, the dynamics of vaporization flux can be significantly affected, which may cause an oscillatory behavior on the droplet evaporation. The droplet-wake interaction and local mass flux are discussed in detail. PMID:25974585

  12. Multirelaxation-time lattice Boltzmann model for droplet heating and evaporation under forced convection

    NASA Astrophysics Data System (ADS)

    Albernaz, Daniel; Do-Quang, Minh; Amberg, Gustav

    2015-04-01

    We investigate the evaporation of a droplet surrounded by superheated vapor with relative motion between phases. The evaporating droplet is a challenging process, as one must take into account the transport of mass, momentum, and heat. Here a lattice Boltzmann method is employed where phase change is controlled by a nonideal equation of state. First, numerical simulations are compared to the D2 law for a vaporizing static droplet and good agreement is observed. Results are then presented for a droplet in a Lagrangian frame under a superheated vapor flow. Evaporation is described in terms of the temperature difference between liquid-vapor and the inertial forces. The internal liquid circulation driven by surface-shear stresses due to convection enhances the evaporation rate. Numerical simulations demonstrate that for higher Reynolds numbers, the dynamics of vaporization flux can be significantly affected, which may cause an oscillatory behavior on the droplet evaporation. The droplet-wake interaction and local mass flux are discussed in detail.

  13. Forced convective heat transfer in boundary layer flow of Sisko fluid over a nonlinear stretching sheet.

    PubMed

    Munir, Asif; Shahzad, Azeem; Khan, Masood

    2014-01-01

    The major focus of this article is to analyze the forced convective heat transfer in a steady boundary layer flow of Sisko fluid over a nonlinear stretching sheet. Two cases are studied, namely (i) the sheet with variable temperature (PST case) and (ii) the sheet with variable heat flux (PHF case). The heat transfer aspects are investigated for both integer and non-integer values of the power-law index. The governing partial differential equations are reduced to a system of nonlinear ordinary differential equations using appropriate similarity variables and solved numerically. The numerical results are obtained by the shooting method using adaptive Runge Kutta method with Broyden's method in the domain[Formula: see text]. The numerical results for the temperature field are found to be strongly dependent upon the power-law index, stretching parameter, wall temperature parameter, material parameter of the Sisko fluid and Prandtl number. In addition, the local Nusselt number versus wall temperature parameter is also graphed and tabulated for different values of pertaining parameters. Further, numerical results are validated by comparison with exact solutions as well as previously published results in the literature. PMID:24949738

  14. Forced convection heat transfer and hydraulic losses in porous carbon foam

    SciTech Connect

    Straatman, Anthony G; Gallego, Nidia C

    2007-01-01

    Experiments and computations are presented to quantify the convective heat transfer and the hydraulic loss that is obtained by forcing water through blocks of graphitic foam (GF) heated from one side. Experiments have been conducted in a small-scale water tunnel instrumented to measure the pressure drop and the temperature rise of water passing through the foam and the base temperature and heat flux into the foam block. The experimental data were then used to calibrate a thermal non-equilibrium finite-volume model to facilitate comparisons between GF and aluminum foam. Comparisons of the pressure drop indicate that both normal and compressed aluminum foams are significantly more permeable than GF. Results of the heat transfer indicate that the maximum possible heat dissipation from a given surface is reached using very thin layers of aluminum foam due to the inability of the foam to entrain heat into its internal structure. In contrast, graphitic foam is able to entrain heat deep into the foam structure due to its high extended surface efficiency and thus much more heat can be transferred from a given surface area. The higher extended surface efficiency is mainly due to the combination of moderate porosity and higher solid-phase conductivity.

  15. Kinetics modeling of the drying of sunflower stem (Helianthus annuus L.) in a forced convection tunnel

    NASA Astrophysics Data System (ADS)

    López, R.; Vaca, M.; Terres, H.; Lizardi, A.; Morales, J.; Flores, J.; Chávez, S.

    2015-01-01

    The sunflower is an annual plant native to the Americas. It possesses a large inflorescence (flowering head), and its name is derived from the flower's shape and image, which is often used to capture the sun. The plant has a rough, broad, hairy stem, coarsely toothed, with rough leaves, and circular flower heads. The sunflower seeds are appreciated for their oil, which has become a widespread cooking ingredient. Leaves of the sunflower can be used as cattle feed, while the stems contain a fiber that may be used in paper production. Recently this flower has been used in phytoremediation of soils, contaminated with heavy metals. Sunflower has been probed as an efficient phytoextractor of chromium, lead, aluminum, zinc, cadmium from soil. In this work we present the experimental results of the drying of the sunflower stem, cut in 100 mm longitudinal sections, with diameters in the range of 11-18 mm. The aim was to obtain a dry and easy-to-handle final product, since these plants were originally cultivated in order to extract heavy metals from a polluted soil. The dried stems could then be easily confined or sent to recycle premises to concentrate the metals. The drying process was done in forced convection within a hot air tunnel. The used temperature was 60 °C, the velocity of air was 3 m/s and the required times were 8 hours. The initial average wet mass was 28 g and the final value was 5 g, resulting in the aimed product.

  16. Heat Transfer Enhancement in Forced Convective Boiling in Microchannels by Periodic Electrospun Nanofiber Coatings

    NASA Astrophysics Data System (ADS)

    Yarin, Alexander; Freystein, Martin; Kolberg, Felix; Sinha-Ray, Sumit; Sahu, Rakesh; Spiegel, Lucas; Gambaryan-Roisman, Tatiana; Stephan, Peter

    2015-03-01

    To enhance heat transfer in forced convective boiling the microchannel bottom was amended by a nano-texture - periodic rectangular mats of electrospun polymer nanofibers. The fibers were ~ 300-500 nm in diameter and the mat thicknesses were about 6-15 μm. The test fluid was FC-72 and the flow in microchannels contained trains of Taylor bubbles. The role of the nanofibers was to retain the warm microchannel bottom wet, to prevent dry-out and thus to enhance the heat removal rate. In the present experiments the time-average heat flux and heat transfer coefficient at the nanofiber-coated domains were found to be 1.5-2 times higher than those at the uncoated ones. Accordingly, a significant decrease (by 5-8 K) in the superheat was observed at the same Re of 387 and power supply of 36.1 kW/m2. At a higher Re of 432 and lower power supply of 28.1 kW/m2 similar trends in the heat removal rate and surface superheat were found. The significant enhancement of the heat transfer results from the fact that nanofiber mats facilitate wetting of surface under passing Taylor bubbles, thus delaying formation of vapor flow at the channel bottom. The interstices of the nanofiber mat act as the nucleation sites facilitating formation of tiny bubbles, which eventually results in a higher heat removal rate from the surface at a reduced superheat.

  17. Experimental study of an upward sub-cooled forced convection in a rectangular channel

    NASA Astrophysics Data System (ADS)

    Kouidri, A.; Madani, B.; Roubi, B.; Hamadouche, A.

    2016-07-01

    The upward sub-cooled forced convection in a rectangular channel is investigated experimentally. The aim of the present work is the studying of the local heat transfer phenomena. Concerning the experimentation: the n-pentane is used as a working fluid, the independent variables are: the velocity in the range from 0.04 to 0.086 m/s and heat flux density with values between 1.8 and 7.36 W/cm2. The results show that the local Nusselt number distribution is not uniform along the channel; however, uniformity is observed in the mean Nusselt number for Reynolds under 1600. On the other hand, a new correlation to predict the local fluid temperature is established as a function of local wall temperature. The wall's heat is dissipated under the common effect of the sub-cooled regime; therefore, the local heat transfer coefficient is increased. The study of the thermal equilibrium showed that for Reynolds less than 1500; almost all of the heat flux generated by the heater cartridges is absorbed by the fluid.

  18. Control of dynamical self-assembly of strongly Brownian nanoparticles through convective forces induced by ultrafast laser

    NASA Astrophysics Data System (ADS)

    Ilday, Serim; Akguc, Gursoy B.; Tokel, Onur; Makey, Ghaith; Yavuz, Ozgun; Yavuz, Koray; Pavlov, Ihor; Ilday, F. Omer; Gulseren, Oguz

    We report a new dynamical self-assembly mechanism, where judicious use of convective and strong Brownian forces enables effective patterning of colloidal nanoparticles that are almost two orders of magnitude smaller than the laser beam. Optical trapping or tweezing effects are not involved, but the laser is used to create steep thermal gradients through multi-photon absorption, and thereby guide the colloids through convective forces. Convective forces can be thought as a positive feedback mechanism that helps to form and reinforce pattern, while Brownian motion act as a competing negative feedback mechanism to limit the growth of the pattern, as well as to increase the possibilities of bifurcation into different patterns, analogous to the competition observed in reaction-diffusion systems. By steering stochastic processes through these forces, we are able to gain control over the emergent pattern such as to form-deform-reform of a pattern, to change its shape and transport it spatially within seconds. This enables us to dynamically initiate and control large patterns comprised of hundreds of colloids. Further, by not relying on any specific chemical, optical or magnetic interaction, this new method is, in principle, completely independent of the material type being assembled.

  19. Numerical investigation of 22 seconds of convection under the effect of dielectrophoretic force in an annular gap

    NASA Astrophysics Data System (ADS)

    Crumeyrolle, Olivier; Egbers, Christoph; Mutabazi, Innocent; Dahley, M. Norman; Smieszek, Marlene

    2012-07-01

    We investigate numerically the thermal convection of an annular dielectric liquid sheet under the effect of the dielectrophoretic force, as observed when a dielectric liquid is permeated by an inhomogeneous electric field. This is of particular interest for space applications as natural convection cannot appear and forced convection from moving parts such as pumps is undesirable due to the expected wearing and lower reliability. Hence heat exchanger relying on the dielectrophoretic force to create convection could provide light, compact and reliable heat exchanger for aerospace cooling systems \\cite{crumeyrolleP}. We investigate the case of a radius ratio equal to 0.5 and Prandtl number of 65. This setup is under experimental investigation at LAS, BTU Cottbus, both on ground and during parabolic flight. The 3D linear stability analysis, that takes the finite size of the system into account, shows that the critical mode is non-axisymmetric and under the form of two counteroriented helices, rather than under the form of rolls as predicted in past investigations\\cite{crumeyrolleT}. Due to the short duration of microgravity during parabolic flight (22 seconds), 3D time-dependent DNS are required with realistic initial conditions. The simulations show that the helices are difficult to observe, as the flow pattern is dominated by convection plumes. We report that transient thermal transfer at the inner cylinder is strongly enhanced by those structures, while the thermal transfer close to the outer cylinder is weaker. J.S. Paschkewitz and {D.M.} Pratt, Exp. Therm. Fluid Sci., 21,, 187 (2000). M. Takashima, Q. J. Mech. appl. Math. 33,, 93 (1980).

  20. Electrical conductivity of chlorite at high pressures and high temperatures

    NASA Astrophysics Data System (ADS)

    Eymard, I.; Mibe, K.; Reynard, B.

    2012-12-01

    In the mantle wedge of subduction zones, high electrical-conductivity bodies have been observed. In order to understand the cause of high-conductivity body in subduction zones, we measured the electrical conductivity of polycrystalline chlorite, at pressures from 2 to 4 GPa and at high temperatures up to 850K using complex impedance spectroscopy in a multi-anvil high-pressure apparatus. The electrical conductivity increased slightly with increasing pressure. The obtained electrical conductivity values are higher than serpentine and talc (Reynard et al., 2011; Guo et al., 2011) and are slightly lower than brucite (Fujita et al., 2007). Although the obtained values are higher compared to serpentine, the presence of chlorite alone is not high enough to explain high-conductivity bodies in subduction-zones. Instead, the presence of some amount of saline fluids is inferred.

  1. Measurement of electrical conductivity for a biomass fire.

    PubMed

    Mphale, Kgakgamatso; Heron, Mal

    2008-08-01

    A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples to measure fuel surface temperature and used as a cavity for microwaves with a laboratory quality 2-port vector network analyzer to determine electrical conductivity from S-parameters. Electrical conductivity for vegetation material flames is important for numerical prediction of flashover in high voltage power transmission faults research. Vegetation fires that burn under high voltage transmission lines reduce flashover voltage by increasing air electrical conductivity and temperature. Analyzer determined electrical conductivity ranged from 0.0058 - 0.0079 mho/m for a fire with a maximum temperature of 1240 K. PMID:19325812

  2. Non-Contact Electrical Conductivity Measurement Technique for Molten Metals

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Ishikawa, T.

    1998-01-01

    A non-contact technique of measuring the electrical conductivity (or resistivity) of conducting liquids while they are levitated by the high temperature electrostatic levitator in a high vacuum is reported.

  3. Electrical conductivity of rocks at high pressures and temperatures

    NASA Technical Reports Server (NTRS)

    Parkhomenko, E. I.; Bondarenko, A. T.

    1986-01-01

    The results of studies of the electrical conductivity in the most widely distributed types of igneous rocks, at temperatures of up to 1200 C, at atmospheric pressure, and also at temperatures of up to 700 C and at pressures of up to 20,000 kg/sq cm are described. The figures of electrical conductivity, of activaation energy and of the preexponential coefficient are presented and the dependence of these parameters on the petrochemical parameters of the rocks are reviewed. The possible electrical conductivities for the depository, granite and basalt layers of the Earth's crust and of the upper mantle are presented, as well as the electrical conductivity distribution to the depth of 200 to 240 km for different geological structures.

  4. Temperature-dependent electrical conductivity of soda-lime glass

    NASA Technical Reports Server (NTRS)

    Bunnell, L. Roy; Vertrees, T. H.

    1993-01-01

    The objective of this educational exercise was to demonstrate the difference between the electrical conductivity of metals and ceramics. A list of the equipment and supplies and the procedure for the experiment are presented.

  5. Measurement of Electrical Conductivity for a Biomass Fire

    PubMed Central

    Mphale, Kgakgamatso; Heron, Mal

    2008-01-01

    A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples to measure fuel surface temperature and used as a cavity for microwaves with a laboratory quality 2-port vector network analyzer to determine electrical conductivity from S-parameters. Electrical conductivity for vegetation material flames is important for numerical prediction of flashover in high voltage power transmission faults research. Vegetation fires that burn under high voltage transmission lines reduce flashover voltage by increasing air electrical conductivity and temperature. Analyzer determined electrical conductivity ranged from 0.0058 - 0.0079 mho/m for a fire with a maximum temperature of 1240 K. PMID:19325812

  6. Magnetothermal Convection of Water with the Presence or Absence of a Magnetic Force Acting on the Susceptibility Gradient.

    PubMed

    Maki, Syou

    2016-01-01

    Heat transfer of magnetothermal convection with the presence or absence of the magnetic force acting on the susceptibility gradient (fsc) was examined by three-dimensional numerical computations. Thermal convection of water enclosed in a shallow cylindrical vessel (diameter over vessel height = 6.0) with the Rayleigh-Benard model was adopted as the model, under the conditions of Prandtl number 6.0 and Ra number 7000, respectively. The momentum equations of convection were nondimensionalized, which involved the term of fsc and the term of magnetic force acting on the magnetic field gradient (fb). All the computations resulted in axisymmetric steady rolls. The values of the averaged Nu, the averaged velocity components U, V, and W, and the isothermal distributions and flow patterns were almost completely the same, regardless of the presence or absence of the term of fsc. As a result, we found that the effect of fsc was extremely small, although much previous research emphasized the effect with paramagnetic solutions under an unsteady state. The magnitude of fsc depends not only on magnetic conditions (magnitudes of magnetic susceptibility and magnetic flux density), but also on the thermal properties of the solution (thermal conductivity, thermal diffusivity, and viscosity). Therefore the effect of fb becomes dominant on the magnetothermal convection. Active control over the density gradient with temperature will be required to advance heat transfer with the effect of fsc. PMID:27606823

  7. Electrically conductive, black thermal control coatings for space craft application. II - Silicone matrix formulation

    NASA Technical Reports Server (NTRS)

    Hribar, V. F.; Bauer, J. L.; O'Donnell, T. P.

    1986-01-01

    Five black electrically conductive thermal-control coatings have been formulated and tested for application on the Galileo spacecraft. The coatings consisted of organic and inorganic systems applied on titanium and aluminum surfaces. The coatings were tested under simulated space environment conditions. Coated specimens were subjected to thermal radiation and convective and conductive heating from -196 to 538 C. Mechanical, physical, thermal, electrical, and optical characteristics, formulation, mixing, application, surface preparation of substrates, and a method of determining electrical resistance are presented for the silicone matrix formulation designated as GF-580.

  8. Chapter A6. Section 6.3. Specific Electrical Conductance

    USGS Publications Warehouse

    Radtke, Dean B.; Davis, Jerri V.; Wilde, Franceska D.

    2005-01-01

    Electrical conductance is a measure of the capacity of a substance to conduct an electrical current. The specific electrical conductance (conductivity) of water is a function of the types and quantities of dissolved substances it contains, normalized to a unit length and unit cross section at a specified temperature. This section of the National Field Manual (NFM) describes U.S. Geological Survey (USGS) guidance and protocols for measurement of conductivity in ground and surface waters.

  9. The electrical conductivity of weakly ionized plasma containing dust particles

    NASA Astrophysics Data System (ADS)

    Li, Hui; Wu, Jian; Yuan, Chengxun; Zhou, Zhongxiang

    2016-07-01

    The effect of charged dust particle on the electrical conductivity of weakly ionized dusty plasma is investigated. It is shown that the additional collision provided by charged dust particles can significantly alter the electrical conductivity of electron-ion plasma. The numerical results indicated that these effects are mainly determined by dust radius, density as well as the charge numbers on dust surface. The obtained results will support an enhanced understanding of the electromagnetic wave propagation processes in dusty plasma.

  10. Electrical Conductivity of the Lower-Mantle Ferropericlase

    SciTech Connect

    Lin, J F; Weir, S T; Jackson, D D; Evans, W J; Vohra, Y K; Qiu, W; Yoo, C S

    2007-04-19

    Electrical conductivity of the lower-mantle ferropericlase-(Mg{sub 0.75},Fe{sub 0.25})O has been studied using designer diamond anvils to pressures over one megabar and temperatures up to 500 K. The electrical conductivity of (Mg{sub 0.75},Fe{sub 0.25})O gradually rises by an order of magnitude up to 50 GPa but decreases by a factor of approximately three between 50 to 70 GPa. This decrease in the electrical conductivity is attributed to the electronic high-spin to low-spin transition of iron in ferropericlase. That is, the electronic spin transition of iron results in a decrease in the mobility and/or density of the charge transfer carriers in the low-spin ferropericlase. The activation energy of the low-spin ferropericlase is 0.27 eV at 101 GPa, similar to that of the high-spin ferropericlase at relatively low temperatures. Our results indicate that low-spin ferropericlase exhibits lower electrical conductivity than high-spin ferropericlase, which needs to be considered in future geomagnetic models for the lower mantle. The extrapolated electrical conductivity of the low-spin ferropericlase, together with that of silicate perovskite, at the lower mantle pressure-temperature conditions is consistent with the model electrical conductivity profile of the lower mantle.

  11. The effect of water on the electrical conductivity of olivine.

    PubMed

    Wang, Duojun; Mookherjee, Mainak; Xu, Yousheng; Karato, Shun-ichiro

    2006-10-26

    It is well known that water (as a source of hydrogen) affects the physical and chemical properties of minerals--for example, plastic deformation and melting temperature--and accordingly plays an important role in the dynamics and geochemical evolution of the Earth. Estimating the water content of the Earth's mantle by direct sampling provides only a limited data set from shallow regions (<200 km depth). Geophysical observations such as electrical conductivity are considered to be sensitive to water content, but there has been no experimental study to determine the effect of water on the electrical conductivity of olivine, the most abundant mineral in the Earth's mantle. Here we report a laboratory study of the dependence of the electrical conductivity of olivine aggregates on water content at high temperature and pressure. The electrical conductivity of synthetic polycrystalline olivine was determined from a.c. impedance measurements at a pressure of 4 GPa for a temperature range of 873-1,273 K for water contents of 0.01-0.08 wt%. The results show that the electrical conductivity is strongly dependent on water content but depends only modestly on temperature. The water content dependence of conductivity is best explained by a model in which electrical conduction is due to the motion of free protons. A comparison of the laboratory data with geophysical observations suggests that the typical oceanic asthenosphere contains approximately 10(-2) wt% water, whereas the water content in the continental upper mantle is less than approximately 10(-3) wt%. PMID:17066032

  12. Dimensionless correlations for forced convection in liquid metals: Part I. single-phase flow

    NASA Astrophysics Data System (ADS)

    Argyropoulos, Stavros A.; Mikrovas, Anthony C.; Doutre, Don A.

    2001-04-01

    Two main objectives were addressed in this article. First, a dimensionless heat-transfer correlation for single-phase flow forced convection in liquid aluminum has been derived using a novel experimental method. An aluminum sphere was rotated with a specific tangential velocity in liquid aluminum. Its melting time was measured and correlated with the convective heat-transfer characteristics. The resulting correlation has the following form: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGceaqabeaadaqdaa% qaaGqaaiaa-5eacaWF1bWaaSbaaSqaaiaadseaaeqaaaaakiabg2da% 9iaaikdacqGHRaWkcaaIXaGaaGimamaaCaaaleqabaGaaGOmaiaac6% cacaaI4aGaaGymaiaaigdaaaGccqGHxdaTciGGsbGaaiyzamaaDaaa% leaacaWGebaabaGaaGimaiaac6cacaaI1aGaaGioaiaaiwdaaaGccq% GHxdaTciGGqbGaaiOCamaaCaaaleqabaGaaGOmaiaac6cacaaIZaGa% aGioaiaaiAdaaaaakeaacaaI1aGaaGymaiaaiAdacaaIYaGaeyizIm% QaciOuaiaacwgadaWgaaWcbaGaamiraaqabaGccqGHKjYOcaaIYaGa% aGymaiaacYcacaaIYaGaaG4naiaaiodacaGGSaqefeKCPfgBaGqbai% aa+bcaciGGqbGaaiOCaiabgIKi7kaaicdacaGGUaGaaGimaiaaigda% caaI0aaaaaa!690C! begin{gathered} overline {Nu_D } = 2 + 10^{2.811} × operatorname{Re} _D^{0.585} × Pr ^{2.386} \\ 5162 ≤slant operatorname{Re} _D ≤slant 21,273, Pr ≈ 0.014 \\ The second objective of the study was to assess the accuracy of various correlations using an annular channel, which was available at an independent setting, at the Alcan Research and Development Laboratory. The correlations investigated were those derived from the current experimental work as well as those derived by other investigators, as presented in their respective published work. Results indicated that when applied to liquid metals, theoretically derived equations as

  13. Micro-gravity: Superconducting coils for crystal growth. Influence of the levitation force on natural convection in the fluid

    NASA Astrophysics Data System (ADS)

    Quettier, L.; Vincent-Viry, O.; Mailfert, A.; Juster, F. P.

    2003-04-01

    This paper presents a novel design of superconducting coils able to generate a micro-gravity environment for protein crystal growth in aqueous solution. The structures have been calculated thanks to a method for “inverse source synthesis problem" developed at the GREEN Choice of the angular offset between the directions of magnetic force field and magnetic field in the working area as well as convection phenomena are also studied.

  14. Investigation of free-forced convection flows in cavity-type receivers. Final yearly report, 1979-1980

    SciTech Connect

    Humphrey, J.A.C.

    1982-01-01

    A summary is provided of the first of three years of experimental and theoretical research on free-forced convection flows in cavity-type solar receivers. New experimental and theoretical results are presented and discussed. The implication of these findings, with respect to the future thrust of the research program, is clarified as well as is possible at the present time. Following various related conclusions a summary and tentative schedule of work projected for year two of research are presented.

  15. Forced convection flow boiling and two-phase flow phenomena in a microchannel

    NASA Astrophysics Data System (ADS)

    Na, Yun Whan

    2008-07-01

    The present study was performed to numerically analyze the evaporation phenomena through the liquid-vapor interface and to investigate bubble dynamics and heat transfer behavior during forced convective flow boiling in a microchannel. Flow instabilities of two-phase flow boiling in a microchannel were studied as well. The main objective of this research is to investigate the fundamental mechanisms of two-phase flow boiling in a microchannel and provide predictive tools to design thermal management systems, for example, microchannel heat sinks. The numerical results obtained from this study were qualitatively and quantitatively compared with experimental results in the open literature. Physical and mathematical models, accounting for evaporating phenomena through the liquid-vapor interface in a microchannel at constant heat flux and constant wall temperature, have been developed, respectively. The heat transfer mechanism is affected by the dominant heat conduction through the thin liquid film and vaporization at the liquid-vapor interface. The thickness of the liquid film and the pressure of the liquid and vapor phases were simultaneously solved by the governing differential equations. The developed semi-analytical evaporation model that takes into account of the interfacial phenomena and surface tension effects was used to obtain solutions numerically using the fourth-order Runge-Kutta method. The effects of heat flux 19 and wall temperature on the liquid film were evaluated. The obtained pressure drops in a microchannel were qualitatively consistent with the experimental results of Qu and Mudawar (2004). Forced convective flow boiling in a single microchannel with different channel heights was studied through a numerical simulation to investigate bubble dynamics, flow patterns, and heat transfer. The momentum and energy equations were solved using the finite volume method while the liquid-vapor interface of a bubble is captured using the VOF (Volume of Fluid

  16. Investigation on magnetoacoustic signal generation with magnetic induction and its application to electrical conductivity reconstruction.

    PubMed

    Ma, Qingyu; He, Bin

    2007-08-21

    A theoretical study on the magnetoacoustic signal generation with magnetic induction and its applications to electrical conductivity reconstruction is conducted. An object with a concentric cylindrical geometry is located in a static magnetic field and a pulsed magnetic field. Driven by Lorentz force generated by the static magnetic field, the magnetically induced eddy current produces acoustic vibration and the propagated sound wave is received by a transducer around the object to reconstruct the corresponding electrical conductivity distribution of the object. A theory on the magnetoacoustic waveform generation for a circular symmetric model is provided as a forward problem. The explicit formulae and quantitative algorithm for the electrical conductivity reconstruction are then presented as an inverse problem. Computer simulations were conducted to test the proposed theory and assess the performance of the inverse algorithms for a multi-layer cylindrical model. The present simulation results confirm the validity of the proposed theory and suggest the feasibility of reconstructing electrical conductivity distribution based on the proposed theory on the magnetoacoustic signal generation with magnetic induction. PMID:17671355

  17. Gravity Wave Forcing of the Mesosphere and Lower Thermosphere: Mountain and Convective Waves Ascending Vertically (MaCWAVE)

    NASA Technical Reports Server (NTRS)

    Fritts, David C.

    2004-01-01

    The specific objectives of this research effort included the following: 1) Quantification of gravity wave propagation throughout the lower and middle atmosphere in order to define the roles of topographic and convective sources and filtering by mean and low-frequency winds in defining the wave field and wave fluxes at greater altitudes; 2) The influences of wave instability processes in constraining wave amplitudes and fluxes and generating turbulence and transport; 3) Gravity wave forcing of the mean circulation and thermal structure in the presence of variable motion fields and wave-wave interactions, since the mean forcing may be a small residual when wave interactions, anisotropy, and momentum and heat fluxes are large; 4) The statistical forcing and variability imposed on the thermosphere at greater altitudes by the strong wave forcing and interactions occurring in the MLTI.

  18. Calibration-free electrical conductivity measurements for highly conductive slags

    SciTech Connect

    MACDONALD,CHRISTOPHER J.; GAO,HUANG; PAL,UDAY B.; VAN DEN AVYLE,JAMES A.; MELGAARD,DAVID K.

    2000-05-01

    This research involves the measurement of the electrical conductivity (K) for the ESR (electroslag remelting) slag (60 wt.% CaF{sub 2} - 20 wt.% CaO - 20 wt.% Al{sub 2}O{sub 3}) used in the decontamination of radioactive stainless steel. The electrical conductivity is measured with an improved high-accuracy-height-differential technique that requires no calibration. This method consists of making continuous AC impedance measurements over several successive depth increments of the coaxial cylindrical electrodes in the ESR slag. The electrical conductivity is then calculated from the slope of the plot of inverse impedance versus the depth of the electrodes in the slag. The improvements on the existing technique include an increased electrochemical cell geometry and the capability of measuring high precision depth increments and the associated impedances. These improvements allow this technique to be used for measuring the electrical conductivity of highly conductive slags such as the ESR slag. The volatilization rate and the volatile species of the ESR slag measured through thermogravimetric (TG) and mass spectroscopy analysis, respectively, reveal that the ESR slag composition essentially remains the same throughout the electrical conductivity experiments.

  19. Multi-rate flowing Wellbore electric conductivity logging method

    SciTech Connect

    Tsang, Chin-Fu; Doughty, Christine

    2003-04-22

    The flowing wellbore electric conductivity logging method involves the replacement of wellbore water by de-ionized or constant-salinity water, followed by constant pumping with rate Q, during which a series of fluid electric conductivity logs are taken. The logs can be analyzed to identify depth locations of inflow, and evaluate the transmissivity and electric conductivity (salinity) of the fluid at each inflow point. The present paper proposes the use of the method with two or more pumping rates. In particular it is recommended that the method be applied three times with pumping rates Q, Q /2, and 2Q. Then a combined analysis of the multi-rate data allows an efficient means of determining transmissivity and salinity values of all inflow points along a well with a confidence measure, as well as their inherent or far-field pressure heads. The method is illustrated by a practical example.

  20. Electrical conduction in macroscopically oriented deoxyribonucleic and hyaluronic acid samples

    NASA Astrophysics Data System (ADS)

    Kutnjak, Zdravko; Lahajnar, Gojmir; Filipič, Cene; Podgornik, Rudolf; Nordenskiöld, Lars; Korolev, Nikolay; Rupprecht, Allan

    2005-04-01

    Measurements of the quasistatic and frequency dependent electrical conductivity below 1 MHz were carried out on wet-spun, macroscopically oriented, calf thymus deoxyribonucleic (DNA) and umbilical cord hyaluronic acid (HA) bulk samples. The frequency dependence of the electrical conductivity in the frequency range of approximately 10-3-106Hz of both materials is surprisingly rather similar. Temperature dependence of the quasistatic electrical conductivity above the low temperature saturation plateau can be well described by the activated Arrhenius law with the activation energy of ≈0.8eV for both DNA and HA. We discuss the meaning of these findings for the possible conduction mechanism in these particular charged polyelectrolytes.

  1. An electrical conductivity model for fractal porous media

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Cai, Jianchao; Hu, Xiangyun; Han, Qi

    2015-06-01

    Archie's equation is an empirical electrical conductivity-porosity model that has been used to predict the formation factor of porous rock for more than 70 years. However, the physical interpretation of its parameters, e.g., the cementation exponent m, remains questionable. In this study, a theoretical electrical conductivity equation is derived based on the fractal characteristics of porous media. The proposed model is expressed in terms of the tortuosity fractal dimension (DT), the pore fractal dimension (Df), the electrical conductivity of the pore liquid, and the porosity. The empirical parameter m is then determined from physically based parameters, such as DT and Df. Furthermore, a distinct interrelationship between DT and Df is obtained. We find a reasonably good match between the predicted formation factor by our model and experimental data.

  2. Electrically conductive resinous bond and method of manufacture

    DOEpatents

    Snowden, Jr., Thomas M.; Wells, Barbara J.

    1987-01-01

    A method of bonding elements together with a bond of high strength and good electrical conductivity which comprises: applying an unfilled polyimide resin between surfaces of the elements to be bonded, heat treating said unfilled polyimide resin in stages between a temperature range of about 40.degree. to 365.degree. C. to form a strong adhesive bond between said elements, applying a metal-filled polyimide resin overcoat between said elements so as to provide electrical connection therebetween, and heat treating said metal-filled polyimide resin with substantially the same temperature profile as the unfilled polyimide resin. The present invention is also concerned with an adhesive, resilient, substantially void free bonding combination for providing a high strength, electrically conductive adhesive attachment between electrically conductive elements which comprises a major amount of an unfilled polyimide resin and a minor amount of a metal-filled polyimide resin.

  3. Electrically conductive resinous bond and method of manufacture

    DOEpatents

    Snowden, T.M. Jr.; Wells, B.J.

    1985-01-01

    A method of bonding elements together with a bond of high strength and good electrical conductivity which comprises: applying an unfilled polyimide resin between surfaces of the elements to be bonded, heat treating said unfilled polyimide resin in stages between a temperature range of about 40 to 365/sup 0/C to form a strong adhesive bond between said elements, applying a metal-filled polyimide resin overcoat between said elements so as to provide electrical connection therebetween, and heat treating said metal-filled polyimide resin with substantially the same temperature profile as the unfilled polyimide resin. The present invention is also concerned with an adhesive, resilient, substantially void free bonding combination for providing a high strength, electrically conductive adhesive attachment between electrically conductive elements which comprises a major amount of an unfilled polyimide resin and a minor amount of a metal-filled polyimide resin.

  4. Sintering, Microstructure, and Electrical Conductivity of Zirconia-Molybdenum Cermet

    NASA Astrophysics Data System (ADS)

    Guo, Yanling; Tang, Lei; Zhang, Jieyu

    2015-08-01

    Monolithic zirconia-molybdenum ( m-ZrO2/Mo) cermets of different compositions (5-40 vol.% Mo) and different initial Mo particles sizes (0.08-13 μm) were prepared by traditional powder metallurgy process. The influences of metal content and initial particle sizes on the densification behavior, microstructure, and electrical conductivity of the cermets were studied. A percolation threshold value was obtained about 17.1 vol.% molybdenum fraction, above which a sharp increase in the electrical conductivity was observed. The temperature dependence of the electrical conductivity of cermets was studied. The cermet containing 5 vol.% Mo showed the ionic nature of the conductivity, while the metallic nature was observed in the samples of Mo fraction up to 16 vol.%. The activation of conductivity for ionic type of conductivity and the temperature coefficient of resistivity as well as the effect of porosity on electronic type conductivity are discussed.

  5. Measuring the local electrical conductivity of human brain tissue

    NASA Astrophysics Data System (ADS)

    Akhtari, M.; Emin, D.; Ellingson, B. M.; Woodworth, D.; Frew, A.; Mathern, G. W.

    2016-02-01

    The electrical conductivities of freshly excised brain tissues from 24 patients were measured. The diffusion-MRI of the hydrogen nuclei of water molecules from regions that were subsequently excised was also measured. Analysis of these measurements indicates that differences between samples' conductivities are primarily due to differences of their densities of solvated sodium cations. Concomitantly, the sample-to-sample variations of their diffusion constants are relatively small. This finding suggests that non-invasive in-vivo measurements of brain tissues' local sodium-cation density can be utilized to estimate its local electrical conductivity.

  6. Electrically conductive doped block copolymer of polyacetylene and polyisoprene

    DOEpatents

    Aldissi, Mahmoud

    1985-01-01

    An electrically conductive block copolymer of polyisoprene and polyacetyl and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I.sub.2 to give it an electrical conductivity in the metallic regime.

  7. Electrical conductivity of Cs2CuCl4 crystals

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.

    2016-05-01

    The electrical conductivity of Cs2CuCl4 single crystals, synthesized by crystallization from aqueous solutions in the CsCl-CuCl2-H2O system, has been investigated. The temperature dependence of the electrical conductivity of crystals in a temperature range of 338-584 K exhibits no anomalies. The electrical transfer activation enthalpy is Δ H σ = 0.72 ± 0.05 eV and the conductivity is σ = 3 × 10-4 S/cm at 584 K. The most likely carriers in Cs2CuCl4 are Cs+ cations, which transfer electric charge according to the vacancy mechanism.

  8. Electrical conductivity measurements on silicate melts using the loop technique

    NASA Technical Reports Server (NTRS)

    Waff, H. S.

    1976-01-01

    A new method is described for measurement of the electrical conductivity of silicate melts under controlled oxygen partial pressure at temperatures to 1550 C. The melt samples are suspended as droplets on platinum-rhodium loops, minimizing iron loss from the melt due to alloying with platinum, and providing maximum surface exposure of the melt to the oxygen-buffering gas atmosphere. The latter provides extremely rapid equilibration of the melt with the imposed oxygen partial pressure. The loop technique involves a minimum of setup time and cost, provides reproducible results to within + or - 5% and is well suited to electrical conductivity studies on silicate melts containing redox cations.

  9. Corrosion-protective coatings from electrically conducting polymers

    SciTech Connect

    Thompson, K.G.; Bryan, C.J.; Benicewicz, B.C.; Wrobleski, D.A.

    1991-12-31

    In a joint research effort involving the Kennedy Space Center and the Los Alamos National Laboratory, electrically conductive polymer coatings have been developed as corrosion-protective coatings for metal surfaces. At the Kennedy Space Center, the launch environment consists of marine, severe solar, and intermittent high acid/elevated temperature conditions. Electrically conductive polymer coatings have been developed which impart corrosion resistance to mild steel when exposed to saline and acidic environments. Such coatings also seem to promote corrosion resistance in areas of mild steel where scratches exist in the protective coating. Such coatings appear promising for many commercial applications.

  10. Corrosion-protective coatings from electrically conducting polymers

    NASA Technical Reports Server (NTRS)

    Thompson, Karen Gebert; Bryan, Coleman J.; Benicewicz, Brian C.; Wrobleski, Debra A.

    1991-01-01

    In a joint effort between NASA Kennedy and LANL, electrically conductive polymer coatings were developed as corrosion protective coatings for metal surfaces. At NASA Kennedy, the launch environment consist of marine, severe solar, and intermittent high acid and/or elevated temperature conditions. Electrically conductive polymer coatings were developed which impart corrosion resistance to mild steel when exposed to saline and acidic environments. Such coatings also seem to promote corrosion resistance in areas of mild steel where scratches exist in the protective coating. Such coatings appear promising for many commercial applications.

  11. Electrically conducting porphyrin and porphyrin-fullerene electropolymers

    DOEpatents

    Gust, Jr., John Devens; Liddell, Paul Anthony; Gervaldo, Miguel Andres; Bridgewater, James Ward; Brennan, Bradley James; Moore, Thomas Andrew; Moore, Ana Lorenzelli

    2014-03-11

    Compounds with aryl ring(s) at porphyrin meso position(s) bearing an amino group in position 4 relative to the porphyrin macrocycle, and at least one unsubstituted 5 (hydrogen-bearing) meso position with the 10-, 15-, and/or 20-relationship to the aryl ring bearing the amino group, and metal complexes thereof, feature broad spectral absorption throughout the visible region. These compounds are electropolymerized to form electrically conducting porphyrin and porphyrin-fullerene polymers that are useful in photovoltaic applications. The structure of one such electrically conducting porphyrin polymer is shown below. ##STR00001##

  12. Contamination from electrically conductive silicone tubing during aerosol chemical analysis

    SciTech Connect

    Yu, Yong; Alexander, M. L.; Perraud, Veronique; Bruns, Emily; Johnson, Stan; Ezell, Michael J.; Finlayson-Pitts, Barbara J.

    2009-06-01

    Electrically conductive silicone tubing is used to minimize losses in sampling lines during the analysis of airborne particle size distributions and number concentrations. We report contamination from this tubing using gas chromatography-mass spectrometry (GC-MS) of filter-collected samples as well as by particle mass spectrometry. Comparison of electrically conductive silicone and stainless steel tubing showed elevated siloxanes only for the silicone tubing. The extent of contamination increased with length of tubing to which the sample was exposed, and decreased with increasing relative humidity.

  13. Electrostatic Discharge Sensitivity and Electrical Conductivity of Composite Energetic Materials

    SciTech Connect

    Michael A. Daniels; Daniel J. Prentice; Chelsea Weir; Michelle L. Pantoya; Gautham Ramachandran; Tim Dallas

    2013-02-01

    Composite energetic material response to electrical stimuli was investigated and a correlation between electrical conductivity and ignition sensitivity was examined. The composites consisted of micrometer particle aluminum combined with another metal, metal oxide, or fluoropolymer. Of the nine tested mixtures, aluminum with copper oxide was the only mixture to ignite by electrostatic discharge with minimum ignition energy (MIE) of 25 mJ and an electrical conductivity of 1246.25 nS; two orders of magnitude higher than the next composite. This study showed a similar trend in MIE for ignition triggered by a discharged spark compared with a thermal hot wire source.

  14. UV-induced surface electrical conductivity jump of polymer nanocomposites

    SciTech Connect

    Chen Guangxin; Miyauchi, Masahiro; Shimizu, Hiroshi

    2008-05-19

    A method of improving the electrical conductivity of polymer nanocomposites under UV irradiation was described. An anatase TiO{sub 2}-grafted carbon nanotube could function as a conductive filler and a photocatalyst when it compounds with a poly(L-lactide) to produce a composite. After UV irradiation, the decomposition of the polymer only occurred on the surface of a poly(L-lactide)/TiO{sub 2} grafted carbon nanotube composite and not on bulk, resulting in an electrical conductivity jump as high as six orders of magnitude.

  15. Numerical study of forced convection in a turbulent heat sink made of several rows of blocks of square form

    NASA Astrophysics Data System (ADS)

    Bouchenafa, Rachid; Saim, Rachid; Abboudi, Said

    2015-09-01

    Forced convection is a phenomenon associated with the heat transfer fluid flows. The presence of convection affects simultaneously the thermal and hydrodynamic fields, the problem is thus coupled. This form of heat transfer inside ducts occurs in many practical applications such as solar collectors, heat exchangers, cooling of electronic components as well as chemical and nuclear. In this work, we are interested primarily for a numerical study of thermo-hydraulic performances of an incompressible turbulent flow of air through a heat sink composed of several rows of bars of square section. Profiles and the axial velocity fields, as well as profiles and the distribution of the Nusselt number are plotted for all the geometry considered and chosen for different sections. The effects of geometrical parameters of the model and the operating parameters on the dynamic and thermal behavior of the air are analyzed.

  16. On the impact of forced roll convection on vertical turbulent transport in cold air outbreaks

    NASA Astrophysics Data System (ADS)

    Gryschka, Micha; Fricke, Jens; Raasch, Siegfried

    2014-11-01

    We investigated the impact of roll convection on the convective boundary layer and vertical transports in different cold air outbreak (CAO) scenarios using large eddy simulations (LES). The organization of convection into rolls was triggered by upstream heterogeneities in the surface temperature, representing ice and water. By changing the sea ice distribution in our LES, we were able to simulate a roll and a nonroll case for each scenario. Furthermore, the roll wavelength was varied by changing the scale of the heterogeneity. The characteristics of the simulated rolls and cloud streets, such as aspect ratios, orientation of the roll axes, and downstream extensions of single rolls agreed closely with observations in CAO situations. The vertical turbulent fluxes, calculated for each simulation, were decomposed into contributions from rolls and from unorganized turbulence. Even though our results confirmed that rolls triggered by upstream heterogeneities can substantially contribute to vertical turbulent fluxes, the total fluxes were not affected by the rolls.

  17. Soil water sensor response to bulk electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water monitoring using electromagnetic (EM) sensors can facilitate observations of water content at high temporal and spatial resolutions. These sensors measure soil dielectric permittivity (Ka) which is largely a function of volumetric water content. However, bulk electrical conductivity BEC c...

  18. ION AND TEMPERATURE DEPENDENCE OF ELECTRICAL CONDUCTANCE FOR NATURAL WATERS

    EPA Science Inventory

    Four empirical equations describing the temperature dependence of electrical conductance of aqueous solutions are compared for the case of single electrolytes. The best method uses a modified Walden product where the log of the ratio between the conductances at two temperatures i...

  19. Electrically conductive polycrystalline diamond and particulate metal based electrodes

    DOEpatents

    Swain, Greg M.; Wang, Jian

    2005-04-26

    An electrically conducting and dimensionally stable diamond (12, 14) and metal particle (13) electrode produced by electrodepositing the metal on the diamond is described. The electrode is particularly useful in harsh chemical environments and at high current densities and potentials. The electrode is particularly useful for generating hydrogen, and for reducing oxygen and oxidizing methanol in reactions which are of importance in fuel cells.

  20. SOIL ELECTRICAL CONDUCTIVITY AS A MANAGEMENT TOOL IN PRECISION FORESTRY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Apparent soil electrical conductivity (ECa) is a useful measurement and indicator of relative productivity of agronomic crops on some soil types. In non-saline soils, spatial variation in soil ECa is strongly related to texture, topsoil depth and profile variations; factors which spatially correlate...

  1. Mechanically stiff, electrically conductive composites of polymers and carbon nanotubes

    DOEpatents

    Worsley, Marcus A.; Kucheyev, Sergei O.; Baumann, Theodore F.; Kuntz, Joshua D.; Satcher, Jr., Joe H.; Hamza, Alex V.

    2015-07-21

    Using SWNT-CA as scaffolds to fabricate stiff, highly conductive polymer (PDMS) composites. The SWNT-CA is immersing in a polymer resin to produce a SWNT-CA infiltrated with a polymer resin. The SWNT-CA infiltrated with a polymer resin is cured to produce the stiff and electrically conductive composite of carbon nanotube aerogel and polymer.

  2. INCREASING INFORMATION WITH MULTIPLE SOIL ELECTRICAL CONDUCTIVITY DATASETS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maps of apparent electrical conductivity (ECa) of the soil profile are widely used in precision agriculture practice and research. Because ECa is often strongly related to clay content, soil water holding capacity, and other soil physical properties that also relate to crop productivity, ECa maps ca...

  3. Estimating depth to argillic soil horizons using apparent electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maps of apparent electrical conductivity (ECa) of the soil profile are widely used in precision agriculture practice and research. A number of ECa sensors are commercially available, each with a unique response function (i.e., the relative contribution of soil at each depth to the integrated ECa rea...

  4. Electrical Conductivity of Thick Films Made from Silver Methylcarbamate Paste

    NASA Astrophysics Data System (ADS)

    Liu, Jianguo; Jiang, Min; Zeng, Xiaoyan

    2013-10-01

    We have explored the electrical conductivity of thick films made from silver methylcarbamate paste using metallic silver as the electrically conductive phase. The paste was composed of 30 wt.% to 90 wt.% organic vehicle and 10 wt.% to 70 wt.% functional phase precursor (silver methylcarbamate). After the paste was sintered, films with thickness of 4.50 μm to 12.70 μm were obtained, in which the elemental percentage of silver varied from about 5 wt.% to above 99 wt.%. Experiments showed that both the electrical conductivity and the elemental percentage were mainly affected by the initial silver content in the paste and the parameters of the sintering process. For given sintering conditions, higher initial silver content led to higher elemental percentage of silver, improving the electrical conductivity of the thick film. The conditions of the sintering process had a significant influence on the evaporation and decomposition rates of the paste components, the elemental percentage of silver, and the microstructure of the thick film. Higher temperatures, longer times, lower heating rates, and more oxygen-rich sintering atmospheres were found to accelerate the evaporation and decomposition and increase the elemental percentage of silver, both of which served to enhance the electrical conductivity. For initial silver contents less than about 10 wt.%, the lowest electrical resistivity of the thick film only reached the order of 10-4 Ω cm, irrespective of the sintering conditions. For contents between 10 wt.% and 25 wt.%, it was possible to attain lowest resistivity values on the order of 10-5 Ω cm. Above 25 wt.%, the lowest resistivity could reach 10-6 Ω cm, comparable to that of bulk silver.

  5. A critical review of predictive models for the onset of significant void in forced-convection subcooled boiling

    SciTech Connect

    Dorra, H.; Lee, S.C.; Bankoff, S.G.

    1993-06-01

    This predictive models for the onset of significant void (OSV) in forced-convection subcooled boiling are reviewed and compared with extensive data. Three analytical models and seven empirical correlations are considered in this review. These models and correlations are put onto a common basis and are compared, again on a common basis, with a variety of data. The evaluation of their range of validity and applicability under various operating conditions are discussed. The results show that the correlations of Saha-Zuber seems to be the best model to predict OSV in vertical subcooled boiling flow.

  6. A Global Model of Mantle Convection that Incorporates Plate Bending Forces, Slab Pull, and Seismic Constraints on the Plate Stress.

    NASA Astrophysics Data System (ADS)

    Lewis, K.; Buffett, B.; Becker, T.

    2008-12-01

    We introduce a global mantle convection model employing mantle density anomalies inferred from seismic tomography to determine present day plate motions. Our approach addresses two aspects that are not usually considered in previous work. First, we include forces associated with the bending of subducting plates. The bending forces oppose the plate motion, and may be comparable in magnitude to other important forces at subduction zones, including slab pull. Second, our model incorporates data from the Global CMT Catalog. We use the focal mechanisms of earthquakes associated with subducting slabs to estimate the relative occurrence of compressional and tensional axes in the down-dip direction of subducting slabs. This information is used to infer the state of stress in the subducting slab, which we use to calculate slab pull forces. We investigate regional variations in slab pull by comparing plate motions derived using seismic constraints with those derived using slab pull forces based solely on the age of subducting plates. Furthermore, we constrain the rheology of subducted plates by comparing plate motions predicted with and without bending forces. Although our current model uses only radial variations in mantle viscosity, we include the capability of permitting lateral variations in viscosity by calculating buoyancy and plate-driven flows using Citcom

  7. Design of Test Loops for Forced Convection Heat Transfer Studies at Supercritical State

    NASA Astrophysics Data System (ADS)

    Balouch, Masih N.

    Worldwide research is being conducted to improve the efficiency of nuclear power plants by using supercritical water (SCW) as the working fluid. One such SCW reactor considered for future development is the CANDU-Supercritical Water Reactor (CANDU-SCWR). For safe and accurate design of the CANDU-SCWR, a detailed knowledge of forced-convection heat transfer in SCW is required. For this purpose, two supercritical fluid loops, i.e. a SCW loop and an R-134a loop are developed at Carleton University. The SCW loop is designed to operate at pressures as high as 28 MPa, temperatures up to 600 °C and mass fluxes of up to 3000 kg/m2s. The R-134a loop is designed to operate at pressures as high as 6 MPa, temperatures up to 140 °C and mass fluxes in the range of 500-6000 kg/m2s. The test loops designs allow for up to 300 kW of heating power to be imparted to the fluid. Both test loops are of the closed-loop design, where flow circulation is achieved by a centrifugal pump in the SCW loop and three parallel-connected gear pumps in the R-134a loop, respectively. The test loops are pressurized using a high-pressure nitrogen cylinder and accumulator assembly, which allows independent control of the pressure, while simultaneously dampening pump induced pressure fluctuations. Heat exchangers located upstream of the pumps control the fluid temperature in the test loops. Strategically located measuring instrumentation provides information on the flow rate, pressure and temperature in the test loops. The test loops have been designed to accommodate a variety of test-section geometries, ranging from a straight circular tube to a seven-rod bundle, achieving heat fluxes up to 2.5 MW/m2 depending on the test-section geometry. The design of both test loops allows for easy reconfiguration of the test-section orientation relative to the gravitational direction. All the test sections are of the directly-heated design, where electric current passing through the pressure retaining walls of the

  8. Numerical investigation of laminar forced convection in Newtonian and non-Newtonian flows in eccentric annuli

    NASA Astrophysics Data System (ADS)

    Fang, Pingping

    1998-12-01

    An extended numerical investigation of fully developed, forced convective laminar flows with heat transfer in eccentric annuli has been carried out. Both Newtonian and non-Newtonian (power-law or Ostwald-de Waele) fluids are studied, representing typical applications in petrochemical, bio-chemical, personal care products, polymer/plastic extrusion and food industries. For the heat transfer problem, with an insulated outer surface, two types of thermal boundary conditions have been considered: Constant wall temperature (T), and uniform axial heat flux with constant peripheral temperature (H1) on the inner surface of the annulus. The governing differential equations for momentum and energy conservation are solved by finite-difference methods. Velocity and temperature distributions in the flow cross section, the wall shear-stress distribution, and isothermal f Re, Nu i,T and Nu i,H1 values for different eccentric annuli (0/leɛ/*/le0.6,/ 0.2/le r/sp/*/le0.8) are presented. In Newtonian flows, the eccentricity is found to have a very strong influence on the flow and temperature fields. In an annulus with relatively large inner cylinder eccentricity, the flow tends to stagnate in the narrow section and has higher peak velocities in the wide section of the annulus. There is considerable flow maldistribution in the azimuthal direction, which in turn produces greater nonuniformity in the temperature field and a consequent degradation in the average heat transfer. Also, the H1 wall condition sustains higher heat transfer coefficients relative to the T boundary condition on the inner surface. For viscous, power-law type non-Newtonian flows, both shear thinning (n<1) and shear thickening (n>1) fluids are considered. Here, the non-linear shear behavior of the fluid is found to further aggravate the flow and temperature maldistribution, and once again the eccentricity is seen to exhibit a very strong influence on the friction and heat transfer behavior. Finally, the

  9. Properties of forced convection experimental with silicon carbide based nano-fluids

    NASA Astrophysics Data System (ADS)

    Soanker, Abhinay

    -fluids. The nano-fluid properties were tested at three different volume concentrations; 0.55%, 1% and 1.6%. Thermal conductivity was measured for the three-volume concentration as function of temperature. Thermal conductivity enhancement increased with the temperature and may be attributed to increased Brownian motion of colloidal particles at higher temperatures. Measured thermal conductivity values are compared with results obtained by theoretical model derived in this work. Effect of temperature and volume concentration on viscosity was also measured and reported. Viscosity increase and related consequences are important issues for the use of nano-fluids. Extensive measurements of heat transfer and pressure drop for forced convection in circular pipes with nano-fluids was also conducted. Parameters such as heat transfer coefficient, Nusselt number, pressure drop and a thermal hydraulic performance factor that takes into account the gains made by increase in thermal conductivity as well as penalties related to increase in pressure drop are evaluated for laminar and transition flow regimes. No significant improvement in heat transfer (Nusselt number) compared to its based fluid was observed. It is also observed that the values evaluated for the thermal-hydraulic performance factor (change in heat transfer/change in pressure drop) was under unity for many flow conditions indicating poor overall applicability of SiC based nano-fluids.

  10. Free and Forced Convection in High Permeability Porous Media: Impact on Gas Flux at the Earth-atmosphere Interface

    NASA Astrophysics Data System (ADS)

    Weisbrod, N.; Levintal, E.; Dragila, M. I.; Kamai, T.

    2015-12-01

    Gas movement within the earth's subsurface and its exchange with the atmosphere is one of the principal elements contributing to soil and atmospheric function. As the soil permeability increases, gas circulation by convective mechanisms becomes significantly greater than the diffusion. Two of the convective mechanisms, which can be of great importance, are being explored in this research. The first one is thermal convection venting (TCV), which develops when there are unstable density gradients. The second mechanism is wind induced convection (WIC), which develops due to surface winds that drive air movement. Here, we report the results of a study on the relationships between the porous media permeability and particle size, and the development and magnitude of TCV and WIC with the development of thermal differences and surface winds. The research included large high-permeability column experiments carried out under highly controlled laboratory conditions, using well-defined single-sized spherical particles while surface winds and thermal differences were forced and monitored. CO2 enriched air, functioned as a tracer, was used to quantify the impact of TCV and WIC on gas migration in the porous media. Results show that in homogenous porous media a permeability range of 10-7 to 10-6 m2 is the threshold value for TCV onset under standard atmospheric conditions. Adding surface wind with an average velocity of 1.5 m s-1 resulted in WIC effect to a depth of -0.3 m in most experimental settings; however, it did not caused additional air circulation at the reference depth of -0.9 m. Furthermore, given the appropriate conditions, a combined effect of TCV and WIC did significantly increase the overall media ventilation. Simulations of temperature profiles in soil under that permeability, showed that as the thermal gradient changes with depth and is a continuous function, TCV cells can be developed in local sections of the profile, not necessarily reaching the atmosphere.

  11. Electrical conductivity of albite melts at high pressures

    NASA Astrophysics Data System (ADS)

    Ni, H.; Keppler, H.

    2009-12-01

    High electrical conductivity observed from magnetotelluric/geomagnetic depth sounding is probably associated with the presence of silicate melts. We investigated electrical conductivity of albite melts, both anhydrous and hydrous with 2.0-5.4 wt% H2O, at 300-1500°C and 0.9-1.8 GPa in a piston-cylinder apparatus. Anhydrous glass was synthesized by fusing oxides and carbonates in 1-bar furnace, and hydrous glasses were prepared by fusing the mixture of glass powder and water in a TZM vessel. A glass cylinder was enclosed between a platinum rod as inner electrode and a Pt-Rh capsule as outer electrode. Platinum wires were used to connect both electrodes to a Solartron 1260 impedance analyzer for conductivity measurements at 3M to 3 HZ. A type-S thermocouple, which was separated from the conductivity circuit, was used to monitor temperature. Furthermore, a Mo foil was employed to reduce the interference from heating circuit. Experimental results demonstrate that the electrical conductivity of albite melt follows an Arrhenius relationship in both glass (<700°C) and liquid (>1100°C) region. In both cases, electrical conductivity increases with water content but decreases with pressure. In the glass region, electrical conductivity can be modelled as logσ = 3.5734 + 0.25534C - (4264+160.43P)/T, where σ is conductivity in S/m, C is water content in wt%, P is pressure in GPa, and T is temperature in K. The above expression implies an activation energy of 82 kJ/mol and an activation volume of 3.1 cc/mol. In the liquid region, electrical conductivity can be modelled as logσ = 2.6906 + 0.065915C - (2339+371.97P)/T, which implies an activation energy of 45 kJ/mol and an activation volume of 7.1 cc/mol. The dominating conduction mechanism in albite melts is suggested to be the motion of sodium cation.

  12. Forced organization of flute-type turbulence by convective cell injection

    SciTech Connect

    Iizuka, S.; Huld, T.; Pecseli, H.L.; Rasmussen, J.J.

    1988-03-14

    Nonlinear interactions between flute-type turbulence and an externally excited convective cell in a strongly magnetized plasma are investigated. During the interaction the azimuthal-mode-number spectrum of the turbulence is deformed and a broad spectrum evolves, indicating an inverse cascade. As a result of a modification in phase and amplitude of the fluctuations, an organized structure is created in turbulence. The macroscopic behavior is well explained by a Van der Pol--type equation.

  13. Vertical microphysical profiles of convective clouds as a tool for obtaining aerosol cloud-mediated climate forcings

    SciTech Connect

    Rosenfeld, Daniel

    2015-12-23

    Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Developing and validating this methodology was possible thanks to the ASR/ARM measurements of CCN and vertical updraft profiles. Validation against ground-based CCN instruments at the ARM sites in Oklahoma, Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25º restricts the satellite coverage to ~25% of the world area in a single day. This methodology will likely allow overcoming the challenge of quantifying the aerosol indirect effect and facilitate a substantial reduction of the uncertainty in anthropogenic climate forcing.

  14. Electrical Conductivity of HgTe at High Temperatures

    NASA Technical Reports Server (NTRS)

    Li, C.; Lehoczky, S. L.; Su, C.-H.; Scripa, R. N.

    2004-01-01

    The electrical conductivity of HgTe was measured using a rotating magnetic field method from 300 K to the melting point (943 K). A microscopic theory for electrical conduction was used to calculate the expected temperature dependence of the HgTe conductivity. A comparison between the measured and calculated conductivities was used to obtain the estimates of the temperature dependence of Gamma(sub 6)-Gamma(sub 8) energy gap from 300 K to 943 K. The estimated temperature coefficient for the energy gap was comparable to the previous results at lower temperatures (less than or equal to 300 K). A rapid increase in the conductivity just above 300 K and a subsequent decrease at 500 K is attributed to band crossover effects. This paper describes the experimental approach and some of the theoretical calculation details.

  15. Experiment of electrical conductivity at low temperature (preliminary measurement)

    SciTech Connect

    Zhao, Y.; Wang, H.

    1998-07-01

    A muon collider needs very large amount of RF power, how to reduce the RF power consumption is of major concern. Thus the application of liquid nitrogen cooling has been proposed. However, it is known that the electrical conductivity depends on many factors and the data from different sources vary in a wide range, especially the data of conductivity of beryllium has no demonstration in a real application. Therefore it is important to know the conductivity of materials, which are commercially available, and at a specified frequency. Here, the results of the preliminary measurement on the electrical conductivity of copper at liquid nitrogen temperature are summarized. Addressed also are the data fitting method and the linear expansion of copper.

  16. A Structural Electrical Conductivity Model for Oxide Melts

    NASA Astrophysics Data System (ADS)

    Thibodeau, Eric; Jung, In-Ho

    2016-02-01

    A structural electrical conductivity model for oxide melts was developed based on the Nernst-Einstein relationship of ionic conductivity. In the description of ionic conductivity, the effective diffusivities of cations in oxide slags were described as a function of the polymerization of the melt. The polymerization of oxide melts was calculated from the Modified Quasichemical Model, taking into account the short-range ordering in slags. The parameters of this conductivity model were fixed to reproduce the electrical conductivity data in unary and binary melts, and the model can well predict the conductivity data in ternary and higher order system without any additional model parameters. The model is successfully applied to the CaO-MgO-MnO-PbO-Al2O3-SiO2 system.

  17. Electrical conductivity and dielectric property of fly ash geopolymer pastes

    NASA Astrophysics Data System (ADS)

    Hanjitsuwan, Sakonwan; Chindaprasirt, Prinya; Pimraksa, Kedsarin

    2011-02-01

    The electrical conductivity and dielectric property of fly ash geopolymer pastes in a frequency range of 100 Hz-10 MHz were studied. The effects of the liquid alkali solution to ash ratios (L/A) were analyzed. The mineralogical compositions and microstructures of fly ash geopolymer materials were also investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The 10 mol sodium hydroxide solution and sodium silicate solution at a sodium silicate-to-sodium hydroxide ratio of 1.0 were used in making geopolymer pastes. The pastes were cured at 40°C. It is found that the electrical conductivity and dielectric constant are dependent on the frequency range and L/A ratios. The conductivity increases but the dielectric constant decreases with increasing frequency.

  18. Carbonatite melts and electrical conductivity in the asthenosphere.

    PubMed

    Gaillard, Fabrice; Malki, Mohammed; Iacono-Marziano, Giada; Pichavant, Michel; Scaillet, Bruno

    2008-11-28

    Electrically conductive regions in Earth's mantle have been interpreted to reflect the presence of either silicate melt or water dissolved in olivine. On the basis of laboratory measurements, we show that molten carbonates have electrical conductivities that are three orders of magnitude higher than those of molten silicate and five orders of magnitude higher than those of hydrated olivine. High conductivities in the asthenosphere probably indicate the presence of small amounts of carbonate melt in peridotite and can therefore be interpreted in terms of carbon concentration in the upper mantle. We show that the conductivity of the oceanic asthenosphere can be explained by 0.1 volume percent of carbonatite melts on average, which agrees with the carbon dioxide content of mid-ocean ridge basalts. PMID:19039132

  19. Tuning Electrical Conductivity of Inorganic Minerals with Carbon Nanomaterials.

    PubMed

    Kovalchuk, Anton A; Tour, James M

    2015-12-01

    Conductive powders based on Barite or calcium carbonate with chemically converted graphene (CCG) were successfully synthesized by adsorption of graphene oxide (GO) or graphene oxide nanoribbons (GONRs) onto the mineral surfaces and subsequent chemical reduction with hydrazine. The efficient adsorption of GO or GONRs on the surface of Barite and calcium carbonate-based mineral particles results in graphene-wrapped hybrid materials that demonstrate a concentration dependent electrical conductivity that increases with the GO or GONR loading. PMID:26544547

  20. Electrical conductivity of carbonbearing granulite at raised temperatures and pressures

    NASA Astrophysics Data System (ADS)

    Glover, Paul W. J.; Vine, F. J.

    1992-12-01

    IT has long been recognized that the electrical conductivity of the lower continental crust is anomalously high. Both pore-saturating brines1-5 and conducting films of carbon at grain boundaries6-10 have been proposed to explain this, but the evidence remains inconclusive. Here we report measurements of electrical conductivity at high temperatures and pressures11-13 on samples of carbon-bearing and carbon-free granulites with a range of electrolyte saturations. The application of pressure to nominally dry carbon-free samples reduces the electrical conductivity as a result of a progressive reduction in pore connectivity, whereas the carbon-bearing samples show an increase in conductivity under the same conditions-an effect that we ascribe to reconnection of carbon conduction pathways during compaction. Moreover, we find a greater increase in conductivity with temperature for the carbon-bearing samples. In the light of work indicating that the abundance of carbon in high-grade rocks has been underestimated in the past7,8, our results provide strong evidence for the role of carbon in lower-crustal conductivity.

  1. Predicting permeability and electrical conductivity of sedimentary rocks from microgeometry

    SciTech Connect

    Schlueter, E.M.; Cook, N.G.W. California Univ., Berkeley, CA . Dept. of Materials Science and Mineral Engineering); Zimmerman, R.W.; Witherspoon, P.A. )

    1991-02-01

    The determination of hydrologic parameters that characterize fluid flow through rock masses on a large scale (e.g., hydraulic conductivity, capillary pressure, and relative permeability) is crucial to activities such as the planning and control of enhanced oil recovery operations, and the design of nuclear waste repositories. Hydraulic permeability and electrical conductivity of sedimentary rocks are predicted from the microscopic geometry of the pore space. The cross-sectional areas and perimeters of the individual pores are estimated from two-dimensional scanning electron micrographs of rock sections. The hydraulic and electrical conductivities of the individual pores are determined from these geometrical parameters, using Darcy's law and Ohm's law. Account is taken of the fact that the cross-sections are randomly oriented with respect to the channel axes, and for possible variation of cross-sectional area along the length of the pores. The effective medium theory from solid-state physics is then used to determine an effective average conductance of each pore. Finally, the pores are assumed to be arranged on a cubic lattice, which allows the calculation of overall macroscopic values for the permeability and the electrical conductivity. Preliminary results using Berea, Boise, Massilon and Saint-Gilles sandstones show reasonably close agreement between the predicted and measured transport properties. 12 refs., 5 figs., 1 tab.

  2. On the electrical conductivity of Ti-implanted alumina

    SciTech Connect

    Salvadori, M. C.; Teixeira, F. S.; Cattani, M.; Nikolaev, A.; Savkin, K. P.; Oks, E. M.; Park, H.-K.; Phillips, L.; Yu, K. M.; Brown, I. G.

    2012-03-15

    Ion implantation of metal species into insulators provides a tool for the formation of thin, electrically conducting, surface layers with experimenter-controlled resistivity. High energy implantation of Pt and Ti into alumina accelerator components has been successfully employed to control high voltage surface breakdown in a number of cases. In the work described here we have carried out some basic investigations related to the origin of this phenomenon. By comparison of the results of alumina implanted with Ti at 75 keV with the results of prior investigations of polymers implanted with Pt at 49 eV and Au at 67 eV, we describe a physical model of the effect based on percolation theory and estimate the percolation parameters for the Ti-alumina composite. We estimate that the percolation dose threshold is about 4 x 10{sup 16} cm{sup -2} and the maximum dose for which the system remains an insulator-conductor composite is about 10 x 10{sup 16} cm{sup -2}. The saturation electrical conductivity is estimated to be about 50 S/m. We conclude that the observed electrical conductivity properties of Ti-implanted alumina can be satisfactorily described by percolation theory.

  3. Composite yarns of multiwalled carbon nanotubes with metallic electrical conductivity.

    PubMed

    Randeniya, Lakshman K; Bendavid, Avi; Martin, Philip J; Tran, Canh-Dung

    2010-08-16

    Unique macrostructures known as spun carbon-nanotube fibers (CNT yarns) can be manufactured from vertically aligned forests of multiwalled carbon nanotubes (MWCNTs). These yarns behave as semiconductors with room-temperature conductivities of about 5 x 10(2) S cm(-1). Their potential use as, for example, microelectrodes in medical implants, wires in microelectronics, or lightweight conductors in the aviation industry has hitherto been hampered by their insufficient electrical conductivity. In this Full Paper, the synthesis of metal-CNT composite yarns, which combine the unique properties of CNT yarns and nanocrystalline metals to obtain a new class of materials with enhanced electrical conductivity, is presented. The synthesis is achieved using a new technique, self-fuelled electrodeposition (SFED), which combines a metal reducing agent and an external circuit for transfer of electrons to the CNT surface, where the deposition of metal nanoparticles takes place. In particular, the Cu-CNT and Au-CNT composite yarns prepared by this method have metal-like electrical conductivities (2-3 x 10(5) S cm(-1)) and are mechanically robust against stringent tape tests. However, the tensile strengths of the composite yarns are 30-50% smaller than that of the unmodified CNT yarn. The SFED technique described here can also be used as a convenient means for the deposition of metal nanoparticles on solid electrode supports, such as conducting glass or carbon black, for catalytic applications. PMID:20665629

  4. Electrical conduction by interface states in semiconductor heterojunctions

    NASA Astrophysics Data System (ADS)

    El Yacoubi, M.; Evrard, R.; Nguyen, N. D.; Schmeits, M.

    2000-04-01

    Electrical conduction in semiconductor heterojunctions containing defect states in the interface region is studied. As the classical drift-diffusion mechanism cannot in any case explain electrical conduction in semiconductor heterojunctions, tunnelling involving interface states is often considered as a possible conduction path. A theoretical treatment is made where defect states in the interface region with a continuous energy distribution are included. Electrical conduction through this defect band then allows the transit of electrons from the conduction band of one semiconductor to the valence band of the second component. The analysis is initiated by electrical measurements on n-CdS/p-CdTe heterojunctions obtained by chemical vapour deposition of CdS on (111) oriented CdTe single crystals, for which current-voltage and capacitance-frequency results are shown. The theoretical analysis is based on the numerical resolution of Poisson's equation and the continuity equations of electrons, holes and defect states, where a current component corresponding to the defect band conduction is explicitly included. Comparison with the experimental curves shows that this formalism yields an efficient tool to model the conduction process through the interface region. It also allows us to determine critical values of the physical parameters when a particular step in the conduction mechanism becomes dominant.

  5. Simulation of forced convection in a channel with nanofluid by the lattice Boltzmann method

    PubMed Central

    2013-01-01

    This paper presents a numerical study of the thermal performance of fins mounted on the bottom wall of a horizontal channel and cooled with either pure water or an Al2O3-water nanofluid. The bottom wall of the channel is heated at a constant temperature and cooled by mixed convection of laminar flow at a relatively low temperature. The results of the numerical simulation indicate that the heat transfer rate of fins is significantly affected by the Reynolds number (Re) and the thermal conductivity of the fins. The influence of the solid volume fraction on the increase of heat transfer is more noticeable at higher values of the Re. PMID:23594696

  6. Combined effect of buoyancy force and Navier slip on MHD flow of a nanofluid over a convectively heated vertical porous plate.

    PubMed

    Mutuku-Njane, Winifred Nduku; Makinde, Oluwole Daniel

    2013-01-01

    We examine the effect of magnetic field on boundary layer flow of an incompressible electrically conducting water-based nanofluids past a convectively heated vertical porous plate with Navier slip boundary condition. A suitable similarity transformation is employed to reduce the governing partial differential equations into nonlinear ordinary differential equations, which are solved numerically by employing fourth-order Runge-Kutta with a shooting technique. Three different water-based nanofluids containing copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are taken into consideration. Graphical results are presented and discussed quantitatively with respect to the influence of pertinent parameters, such as solid volume fraction of nanoparticles (φ), magnetic field parameter (Ha), buoyancy effect (Gr), Eckert number (Ec), suction/injection parameter (f w ), Biot number (Bi), and slip parameter ( β ), on the dimensionless velocity, temperature, skin friction coefficient, and heat transfer rate. PMID:24222749

  7. Combined Effect of Buoyancy Force and Navier Slip on MHD Flow of a Nanofluid over a Convectively Heated Vertical Porous Plate

    PubMed Central

    2013-01-01

    We examine the effect of magnetic field on boundary layer flow of an incompressible electrically conducting water-based nanofluids past a convectively heated vertical porous plate with Navier slip boundary condition. A suitable similarity transformation is employed to reduce the governing partial differential equations into nonlinear ordinary differential equations, which are solved numerically by employing fourth-order Runge-Kutta with a shooting technique. Three different water-based nanofluids containing copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are taken into consideration. Graphical results are presented and discussed quantitatively with respect to the influence of pertinent parameters, such as solid volume fraction of nanoparticles (φ), magnetic field parameter (Ha), buoyancy effect (Gr), Eckert number (Ec), suction/injection parameter (fw), Biot number (Bi), and slip parameter (β), on the dimensionless velocity, temperature, skin friction coefficient, and heat transfer rate. PMID:24222749

  8. Experimental study of Cu-water nanofluid forced convective flow inside a louvered channel

    NASA Astrophysics Data System (ADS)

    Khoshvaght-Aliabadi, M.; Hormozi, F.; Zamzamian, A.

    2015-03-01

    Heat transfer enhancement plays a very important role for energy saving in plate-fin heat exchangers. In the present study, the influences of simultaneous utilization of a louvered plate-fin channel and copper-base deionized water nanofluid on performance of these exchangers are experimentally explored. The effects of flow rate (2-5 l/min) and nanoparticles weight fraction (0-0.4 %) on heat transfer and pressure drop characteristics are determined. Experimental results indicate that the use of louvered channel instead of the plain one can improve the heat transfer performance. Likewise, addition of small amounts of copper nanoparticles to the base fluid augments the convective heat transfer coefficient remarkably. The maximum rise of 21.7 % in the convective heat transfer coefficient is observed for the 0.4 % wt nanofluid compared to the base fluid. Also, pumping power for the base fluid and nanofluids are calculated based on the measured pressure drop in the louvered channel. The average increase in pumping power is 11.8 % for the nanofluid with 0.4 % wt compared to the base fluid. Applied performance criterion shows a maximum performance index of 1.167 for the nanofluid with 0.1 % wt Finally, two correlations are proposed for Nusselt number and friction factor which fit the experimental data with in ±10 %.

  9. Experimental study of Cu-water nanofluid forced convective flow inside a louvered channel

    NASA Astrophysics Data System (ADS)

    Khoshvaght-Aliabadi, M.; Hormozi, F.; Zamzamian, A.

    2014-09-01

    Heat transfer enhancement plays a very important role for energy saving in plate-fin heat exchangers. In the present study, the influences of simultaneous utilization of a louvered plate-fin channel and copper-base deionized water nanofluid on performance of these exchangers are experimentally explored. The effects of flow rate (2-5 l/min) and nanoparticles weight fraction (0-0.4 %) on heat transfer and pressure drop characteristics are determined. Experimental results indicate that the use of louvered channel instead of the plain one can improve the heat transfer performance. Likewise, addition of small amounts of copper nanoparticles to the base fluid augments the convective heat transfer coefficient remarkably. The maximum rise of 21.7 % in the convective heat transfer coefficient is observed for the 0.4 % wt nanofluid compared to the base fluid. Also, pumping power for the base fluid and nanofluids are calculated based on the measured pressure drop in the louvered channel. The average increase in pumping power is 11.8 % for the nanofluid with 0.4 % wt compared to the base fluid. Applied performance criterion shows a maximum performance index of 1.167 for the nanofluid with 0.1 % wt Finally, two correlations are proposed for Nusselt number and friction factor which fit the experimental data with in ±10 %.

  10. CMB topography and electrical conductivity as additional constraints for the lowermost mantle thermo-chemical structure

    NASA Astrophysics Data System (ADS)

    Deschamps, F.; Yin, Y.; Tackley, P. J.

    2013-12-01

    A variety of seismic observations, including tomographic models, indicate that the lowermost mantle is strongly heterogeneous. Seismic observations further support a thermo-chemical origin for the large scale heterogeneities. In particular, the large low-shear wave velocity provinces (LLSVP) observed by global tomographic images are better explained by a combination of thermal and chemical anomalies. Despite the accuracy of seismic information, uncertainties and trade-off still prevent the determination of a detailed lower mantle thermo-chemical structure. For instance, the nature of chemical heterogeneities and the exact role played by the post-perovskite phase transition are still debated. Additional constraints are needed to discriminate between the possible models of structure and dynamics of the lower mantle. Here, we consider two potential additional constraints, the electrical conductivity and the dynamic topography at the core-mantle boundary (CMB). Unlike density and seismic velocities, electrical conductivity increases with temperature. In addition, it strongly varies with the iron and silicate content. Using appropriate mineral physics data, we calculated a 3D distribution of electrical conductivity in lower mantle from the thermo-chemical structure inferred by probabilistic tomography, which maps iron and silicate excess in the LLSVP. In the lowermost mantle, we observe a belt of high conductivity, with maximum values around 20 S/m located in the LLSVP. Such a belt may trigger electric currents in the lowermost mantle and induce magnetic field variations with period of one year or more. It may thus be seen by global models of electrical conductivity. Unfortunately, such models do not sample yet regions deeper than 2000 km. A second, independent constraint we explored is the dynamic topography at the CMB. We used stagYY to calculate the dynamic topography associated with several models of thermo-chemical convection, and observe strong differences