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Sample records for heat transport header

  1. Large variable conductance heat pipe. Transverse header

    NASA Technical Reports Server (NTRS)

    Edelstein, F.

    1975-01-01

    The characteristics of gas-loaded, variable conductance heat pipes (VCHP) are discussed. The difficulties involved in developing a large VCHP header are analyzed. The construction of the large capacity VCHP is described. A research project to eliminate some of the problems involved in large capacity VCHP operation is explained.

  2. Method for producing a heat exchanger having a flat tube and header pipes

    SciTech Connect

    Koisuka, M.; Aoki, H.

    1987-07-07

    This patent describes a method for producing a heat exchanger comprising a flat metal tube of an aluminum alloy for conveying fluid, and two header pipes joined respectively onto opposite ends of the flat tube, which comprises the steps of preparing the flat tube and the header pipes of an aluminum alloy other than a brazing filler metal, and preparing two brazing filler members of an aluminum alloy brazing filler metal. Each of the header pipes has an axial slot in a side wall for receiving an end of the flat tube. Each brazing filler member comprises an elongated plate portion arcuately curved transversely with a lengthwise elongated opening and with a flat sleeve portion projecting from an outer surface of the elongated plate portion overlying the elongated opening in registration. The sleeve portion has an inner surface congruent with the perimeter of the elongated opening, the sleeve portion inner surface and the elongated opening having an inner contour slightly larger than the outer contour of the flat tube; inserting each of opposite ends of the flat tube through both the sleeve portion and the elongated opening of a respective brazing filler member. It inserts each of the flat tube ends into a respective one of the header pipes through the axial slot while bringing the arcuately curved plate portions in contact with the outer surface of the corresponding header pipe. Brazing filler members are heated together with the header pipes and end portions of the flat tube to melt the brazing filler members. Header pipes are joined and brazed to the corresponding ends of the flat tube.

  3. ALMA Binary Data Transport Mechanism using VOTable Headers

    NASA Astrophysics Data System (ADS)

    Wicenec, A.; Meuss, H.; Pisano, J.

    2006-07-01

    ALMA will produce very large data rates and volumes. In full operation the correlator will generate up to 60 MB/s of visibility data. These data have to be transported from the correlator on the high site (5000 m) to the ALMA archive, the telescope calibration and the quick-look subsystems, which are all located at the low site (2500 m) some 40 km away. A dedicated fiber connection between the sites is under construction and the interfaces between the subsystems are under development. The actual transport format produced by the correlator has been defined and implemented and is described in this paper in more detail. The format is derived from the SOAP with attachments [1], but instead of the SOAP XML envelope it is using a slightly modified VOTable [2] to keep the description of the binary data. The VOTable uses content ID pointers (CID, RFC2111 [3]) to refer to the binary parts contained in the same Multipart/Related (RFC2387 [4]) container. Such Multipart/Related containers are constructed for each ALMA integration and sent through a multimedia streaming connection implemented in CORBA (TAO[5, 6]).

  4. Heat transport system

    DOEpatents

    Pierce, Bill L.

    1978-01-01

    A heat transport system of small size which can be operated in any orientation consists of a coolant loop containing a vaporizable liquid as working fluid and includes in series a vaporizer, a condenser and two one-way valves and a pressurizer connected to the loop between the two valves. The pressurizer may be divided into two chambers by a flexible diaphragm, an inert gas in one chamber acting as a pneumatic spring for the system.

  5. Heat transport system

    DOEpatents

    Harkness, Samuel D.

    1982-01-01

    A falling bed of ceramic particles receives neutron irradiation from a neutron-producing plasma and thereby transports energy as heat from the plasma to a heat exchange location where the ceramic particles are cooled by a gas flow. The cooled ceramic particles are elevated to a location from which they may again pass by gravity through the region where they are exposed to neutron radiation. Ceramic particles of alumina, magnesia, silica and combinations of these materials are contemplated as high-temperature materials that will accept energy from neutron irradiation. Separate containers of material incorporating lithium are exposed to the neutron flux for the breeding of tritium that may subsequently be used in neutron-producing reactions. The falling bed of ceramic particles includes velocity partitioning between compartments near to the neutron-producing plasma and compartments away from the plasma to moderate the maximum temperature in the bed.

  6. Heat transport system

    DOEpatents

    Harkness, S.D.

    A falling bed of ceramic particles receives neutron irradiation from a neutron-producing plasma and thereby transports energy as heat from the plasma to a heat exchange location where the ceramic particles are cooled by a gas flow. The cooled ceramic particles are elevated to a location from which they may again pass by gravity through the region where they are exposed to neutron radiation. Ceramic particles of alumina, magnesia, silica and combinations of these materials are contemplated as high-temperature materials that will accept energy from neutron irradiation. Separate containers of material incorporating lithium are exposed to the neutron flux for the breeding of tritium that may subsequently be used in neutron-producing reactions. The falling bed of ceramic particles includes velocity partitioning between compartments near to the neutron-producing plasma and compartments away from the plasma to moderate the maximum temperature in the bed.

  7. Heat transport through atomic contacts.

    PubMed

    Mosso, Nico; Drechsler, Ute; Menges, Fabian; Nirmalraj, Peter; Karg, Siegfried; Riel, Heike; Gotsmann, Bernd

    2017-02-06

    Heat transport and dissipation at the nanoscale severely limit the scaling of high-performance electronic devices and circuits. Metallic atomic junctions serve as model systems to probe electrical and thermal transport down to the atomic level as well as quantum effects that occur in one-dimensional (1D) systems. Whereas charge transport in atomic junctions has been studied intensively in the past two decades, heat transport remains poorly characterized because it requires the combination of a high sensitivity to small heat fluxes and the formation of stable atomic contacts. Here we report heat-transfer measurements through atomic junctions and analyse the thermal conductance of single-atom gold contacts at room temperature. Simultaneous measurements of charge and heat transport reveal the proportionality of electrical and thermal conductance, quantized with the respective conductance quanta. This constitutes a verification of the Wiedemann-Franz law at the atomic scale.

  8. Survey of Header Compression Techniques

    NASA Technical Reports Server (NTRS)

    Ishac, Joseph

    2001-01-01

    This report provides a summary of several different header compression techniques. The different techniques included are: (1) Van Jacobson's header compression (RFC 1144); (2) SCPS (Space Communications Protocol Standards) header compression (SCPS-TP, SCPS-NP); (3) Robust header compression (ROHC); and (4) The header compression techniques in RFC2507 and RFC2508. The methodology for compression and error correction for these schemes are described in the remainder of this document. All of the header compression schemes support compression over simplex links, provided that the end receiver has some means of sending data back to the sender. However, if that return path does not exist, then neither Van Jacobson's nor SCPS can be used, since both rely on TCP (Transmission Control Protocol). In addition, under link conditions of low delay and low error, all of the schemes perform as expected. However, based on the methodology of the schemes, each scheme is likely to behave differently as conditions degrade. Van Jacobson's header compression relies heavily on the TCP retransmission timer and would suffer an increase in loss propagation should the link possess a high delay and/or bit error rate (BER). The SCPS header compression scheme protects against high delay environments by avoiding delta encoding between packets. Thus, loss propagation is avoided. However, SCPS is still affected by an increased BER (bit-error-rate) since the lack of delta encoding results in larger header sizes. Next, the schemes found in RFC2507 and RFC2508 perform well for non-TCP connections in poor conditions. RFC2507 performance with TCP connections is improved by various techniques over Van Jacobson's, but still suffers a performance hit with poor link properties. Also, RFC2507 offers the ability to send TCP data without delta encoding, similar to what SCPS offers. ROHC is similar to the previous two schemes, but adds additional CRCs (cyclic redundancy check) into headers and improves

  9. Heat transport in nonuniform superconductors

    NASA Astrophysics Data System (ADS)

    Richard, Caroline; Vorontsov, Anton B.

    2016-08-01

    We calculate electronic energy transport in inhomogeneous superconductors using a fully self-consistent nonequilibrium quasiclassical Keldysh approach. We develop a general theory and apply it to a superconductor with an order parameter that forms domain walls of the type encountered in the Fulde-Ferrell-Larkin-Ovchinnikov state. The heat transport in the presence of a domain wall is inherently anisotropic and nonlocal. The bound states in the nonuniform region play a crucial role and control heat transport in several ways: (i) they modify the spectrum of quasiparticle states and result in Andreev reflection processes and (ii) they hybridize with the impurity band and produce a local transport environment with properties very different from those in a uniform superconductor. As a result of this interplay, heat transport becomes highly sensitive to temperature, magnetic field, and disorder. For strongly scattering impurities, we find that the transport across domain walls at low temperatures is considerably more efficient than in the uniform superconducting state.

  10. Acoustically enhanced heat transport

    NASA Astrophysics Data System (ADS)

    Ang, Kar M.; Yeo, Leslie Y.; Friend, James R.; Hung, Yew Mun; Tan, Ming K.

    2016-01-01

    We investigate the enhancement of heat transfer in the nucleate boiling regime by inducing high frequency acoustic waves (f ˜ 106 Hz) on the heated surface. In the experiments, liquid droplets (deionized water) are dispensed directly onto a heated, vibrating substrate. At lower vibration amplitudes (ξs ˜ 10-9 m), the improved heat transfer is mainly due to the detachment of vapor bubbles from the heated surface and the induced thermal mixing. Upon increasing the vibration amplitude (ξs ˜ 10-8 m), the heat transfer becomes more substantial due to the rapid bursting of vapor bubbles happening at the liquid-air interface as a consequence of capillary waves travelling in the thin liquid film between the vapor bubble and the air. Further increases then lead to rapid atomization that continues to enhance the heat transfer. An acoustic wave displacement amplitude on the order of 10-8 m with 106 Hz order frequencies is observed to produce an improvement of up to 50% reduction in the surface temperature over the case without acoustic excitation.

  11. Acoustically enhanced heat transport

    SciTech Connect

    Ang, Kar M.; Hung, Yew Mun; Tan, Ming K.; Yeo, Leslie Y.

    2016-01-15

    We investigate the enhancement of heat transfer in the nucleate boiling regime by inducing high frequency acoustic waves (f ∼ 10{sup 6} Hz) on the heated surface. In the experiments, liquid droplets (deionized water) are dispensed directly onto a heated, vibrating substrate. At lower vibration amplitudes (ξ{sub s} ∼ 10{sup −9} m), the improved heat transfer is mainly due to the detachment of vapor bubbles from the heated surface and the induced thermal mixing. Upon increasing the vibration amplitude (ξ{sub s} ∼ 10{sup −8} m), the heat transfer becomes more substantial due to the rapid bursting of vapor bubbles happening at the liquid-air interface as a consequence of capillary waves travelling in the thin liquid film between the vapor bubble and the air. Further increases then lead to rapid atomization that continues to enhance the heat transfer. An acoustic wave displacement amplitude on the order of 10{sup −8} m with 10{sup 6} Hz order frequencies is observed to produce an improvement of up to 50% reduction in the surface temperature over the case without acoustic excitation.

  12. Acoustically enhanced heat transport.

    PubMed

    Ang, Kar M; Yeo, Leslie Y; Friend, James R; Hung, Yew Mun; Tan, Ming K

    2016-01-01

    We investigate the enhancement of heat transfer in the nucleate boiling regime by inducing high frequency acoustic waves (f ∼ 10(6) Hz) on the heated surface. In the experiments, liquid droplets (deionized water) are dispensed directly onto a heated, vibrating substrate. At lower vibration amplitudes (ξs ∼ 10(-9) m), the improved heat transfer is mainly due to the detachment of vapor bubbles from the heated surface and the induced thermal mixing. Upon increasing the vibration amplitude (ξs ∼ 10(-8) m), the heat transfer becomes more substantial due to the rapid bursting of vapor bubbles happening at the liquid-air interface as a consequence of capillary waves travelling in the thin liquid film between the vapor bubble and the air. Further increases then lead to rapid atomization that continues to enhance the heat transfer. An acoustic wave displacement amplitude on the order of 10(-8) m with 10(6) Hz order frequencies is observed to produce an improvement of up to 50% reduction in the surface temperature over the case without acoustic excitation.

  13. Solar heat transport fluid

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The progress made on the development and delivery of noncorrosive fluid subsystems is reported. These subsystems are to be compatible with closed-loop solar heating or combined heating and hot water systems. They are also to be compatible with both metallic and non-metallic plumbing systems. At least 100 gallons of each type of fluid recommended by the contractor will be delivered under the contract. The performance testing of a number of fluids is described.

  14. Header design evaluation. Final report

    SciTech Connect

    Stubenhofer, R.L.

    1993-08-01

    An evaluation was conducted of two new six-pin header designs. This evaluation consisted of designing, evaluating, procuring, and building contact module subassemblies with each of the two designs. The study was initiated as a result of the high scrap costs associated with the current product design. Two new designs were found to be feasible alternative to the current design.

  15. Vapor phase heat transport systems

    NASA Astrophysics Data System (ADS)

    Hedstrom, J. C.; Neeper, D. A.

    1985-09-01

    Progress in theoretical and experimental investigations of various forms of a vapor transport system for solar space heating is described, which could also be applied to service water heating. The refrigerant is evaporated in a solar collector, which may be located on the external wall or roof of a building. The vapor is condensed in a passively discharged thermal storage unit located within the building. The condensed liquid can be returned to the collector either by a motor-driven pump or by a completely passive self-pumping mechanism in which the vapor pressure lifts the liquid from the condenser to the collector. The theoretical investigation analyzes this self-pumping scheme. Experiments in solar test cells compared the operation of both passive and active forms of the vapor system with the operation of a passive water wall. The vapor system operates as expected, with potential advantages over other passive systems in design flexibility and energy yield.

  16. Visualization of heat transport in heat pipes using thermocamera

    NASA Astrophysics Data System (ADS)

    Nemec, Patrik; Čaja, Alexander; Lenhard, Richard

    2010-10-01

    Heat pipes, as passive elements show a high level of reliability when taking heat away and they can take away heat flows having a significantly higher density than systems with forced convection. A heat pipe is a hermetically closed duct, filled with working fluid. Transport of heat in heat pipes is procured by the change of state of the working fluid from liquid state to steam and vice versa and depends on the hydrodynamic and heat processes in the pipe. This study have been focused on observing the impact these processes have on the heat process, the transport of heat within the heat pipe with the help of thermovision. The experiment is oriented at scanning the changes in the surface temperatures of the basic structural types of capillary heat pipes in vertical position.

  17. Macroscopic heat transport equations and heat waves in nonequilibrium states

    NASA Astrophysics Data System (ADS)

    Guo, Yangyu; Jou, David; Wang, Moran

    2017-03-01

    Heat transport may behave as wave propagation when the time scale of processes decreases to be comparable to or smaller than the relaxation time of heat carriers. In this work, a generalized heat transport equation including nonlinear, nonlocal and relaxation terms is proposed, which sums up the Cattaneo-Vernotte, dual-phase-lag and phonon hydrodynamic models as special cases. In the frame of this equation, the heat wave propagations are investigated systematically in nonequilibrium steady states, which were usually studied around equilibrium states. The phase (or front) speed of heat waves is obtained through a perturbation solution to the heat differential equation, and found to be intimately related to the nonlinear and nonlocal terms. Thus, potential heat wave experiments in nonequilibrium states are devised to measure the coefficients in the generalized equation, which may throw light on understanding the physical mechanisms and macroscopic modeling of nanoscale heat transport.

  18. Optimizing header strength utilizing finite element analyses

    NASA Astrophysics Data System (ADS)

    Burchett, S. N.

    Finite element techniques have been successfully applied as a design tool in the optimization of high strength headers for pyrotechnic-driven actuators. These techniques have been applied to three aspects of the design process of a high strength header. The design process was a joint effort of experts from several disciplines including design engineers, material scientists, test engineers, manufacturing engineers, and structural analysts. Following material selection, finite element techniques were applied to evaluate the residual stresses due to manufacturing which were developed in the high strength glass ceramic-to-metal seal headers. Results from these finite element analyses were used to identify header designs which were manufacturable and had a minimum residual stress state. Finite element techniques were than applied to obtain the response of the header due to pyrotechnic burn. The results provided realistic upper bounds on the pressure containment ability of various preliminary header designs and provided a quick and inexpensive method of strengthening and refining the designs. Since testing of the headers was difficult and sometimes destructive, results of the analyses were also used to interpret test results and identify failure modes. In this paper, details of the finite element element techniques including the models used, material properties, material failure models, and loading will be presented. Results from the analyses showing the header failure process will also be presented. This paper will show that significant gains in capability and understanding can result when finite element techniques are included as an integral part of the design process of complicated high strength headers.

  19. A 2.2 sq m /24 sq ft/ self-controlled deployable heat pipe radiator - Design and test

    NASA Technical Reports Server (NTRS)

    Edelstein, F.

    1975-01-01

    An all heat pipe, deployable radiator has been developed which can effectively control pumped fluid loop temperatures under varying loads using variable conductance panel heat pipes. The 2.2 sq m (24 sq ft) aluminum panel can be coupled to either a fluid header or a flexible heat pipe header capable of transporting 850 watts in a 90-deg bent configuration. Test results support the feasibility of using this system to passively control Freon-21 loop temperatures.

  20. Roll-forming tubes to header plates

    NASA Technical Reports Server (NTRS)

    Kramer, K.

    1976-01-01

    Technique has been developed for attaching and sealing tubes to header plates using a unique roll-forming tool. Technique is useful for attaching small tubes which are difficult to roll into conventional grooves in header plate tube holes, and for attaching when welding, brazing, or soldering is not desirable.

  1. Heat transport system, method and material

    DOEpatents

    Musinski, Donald L.

    1987-01-01

    A heat transport system, method and composite material in which a plurality of hollow spherical shells or microspheres having an outside diameter of less than or equal to 500 microns are encapsulated or embedded within a bulk material. Each shell has captured therein a volatile working fluid, such that each shell operates as a microsized heat pipe for conducting heat through the composite structure.

  2. Standardizing Documentation of FITS Headers

    NASA Astrophysics Data System (ADS)

    Hourcle, Joseph

    2014-06-01

    Although the FITS file format[1] can be self-documenting, human intervention is often needed to read the headers to write the necessary transformations to make a given instrument team's data compatible with our preferred analysis package. External documentation may be needed to determine what the values are of coded values or unfamiliar acronyms.Different communities have interpreted keywords slightly differently. This has resulted in ambiguous fields such as DATE-OBS, which could be either the start or mid-point of an observation.[2]Conventions for placing units and additional information within the comments of a FITS card exist, but they require re-writing the FITS file. This operation can be quite costly for large archives, and should not be taken lightly when dealing with issues of digital preservation.We present what we believe is needed for a machine-actionable external file describing a given collection of FITS files. We seek comments from data producers, archives, and those writing software to help develop a single, useful, implementable standard.References:[1] Pence, et.al. 2010, http://dx.doi.org/10.1051/0004-6361/201015362[2] Rots, et.al, (in preparation), http://hea-www.cfa.harvard.edu arots/TimeWCS/

  3. Heat transport system, method and material

    DOEpatents

    Musinski, D.L.

    1987-04-28

    A heat transport system, method and composite material are disclosed in which a plurality of hollow spherical shells or microspheres having an outside diameter of less than or equal to 500 microns are encapsulated or embedded within a bulk material. Each shell has captured therein a volatile working fluid, such that each shell operates as a microsized heat pipe for conducting heat through the composite structure. 1 fig.

  4. Clustering header categories extracted from web tables

    NASA Astrophysics Data System (ADS)

    Nagy, George; Embley, David W.; Krishnamoorthy, Mukkai; Seth, Sharad

    2015-01-01

    Revealing related content among heterogeneous web tables is part of our long term objective of formulating queries over multiple sources of information. Two hundred HTML tables from institutional web sites are segmented and each table cell is classified according to the fundamental indexing property of row and column headers. The categories that correspond to the multi-dimensional data cube view of a table are extracted by factoring the (often multi-row/column) headers. To reveal commonalities between tables from diverse sources, the Jaccard distances between pairs of category headers (and also table titles) are computed. We show how about one third of our heterogeneous collection can be clustered into a dozen groups that exhibit table-title and header similarities that can be exploited for queries.

  5. Heat transport in active harmonic chains

    SciTech Connect

    Zheng, Mei C.; Ellis, Fred M.; Kottos, Tsampikos; Fleischmann, Ragnar; Geisel, Theo; Prosen, Tomaz

    2011-08-15

    We show that a harmonic lattice model with amplifying and attenuating elements, when coupled to two thermal baths, exhibits unique heat transport properties. Some of these novel features include anomalous nonequilibrium steady-state heat currents, negative differential thermal conductance, as well as nonreciprocal heat transport. We find that when these elements are arranged in a PT-symmetric manner, the domain of existence of the nonequilibrium steady state is maximized. We propose an electronic experimental setup based on resistive-inductive-capacitive (RLC) transmission lines, where our predictions can be tested.

  6. Yields in stripper header vs conventional header in dryland cropping systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Differences in crop residue quality can impact the amount of soil water storage in semi-arid no-till systems of the West Central Great Plains. Using a stripper header as opposed to a conventional-reel type header to harvest small grains impacts the quality of the crop residue left in the field. Pr...

  7. Heat transport across structural boundaries

    NASA Astrophysics Data System (ADS)

    Shaubach, R. M.

    1985-06-01

    A description of a program which uses heat-pipe principles in the design of prototype rotating thermal joints for the NASA centralized thermal control system, as well as of the first six months of work, during which the contract goals were met, is given. The design requirements include operating in a temperature range from 0 to 40 C, transferring 10 kilowatts with an overall temperature drop of 5 C, and rotating a total of 60,000 revolutions at 2 rpm with a 1700 inch pound moment loading. The predicted and required performance for the rotating joint are compared and the results are presented in a table. Consideration is also given to Phase II of the program.

  8. Capillary heat transport and fluid management device

    NASA Technical Reports Server (NTRS)

    Owen, James W. (Inventor)

    1988-01-01

    A passive heat transporting and fluid management apparatus including a housing in the form of an extruded body member having flat upper and lower surfaces is disclosed. A main liquid channel and at least two vapor channels extend longitudinally through the housing from a heat input end to a heat output end. The vapor channels have sintered powdered metal fused about the peripheries to form a porous capillary wick structure. A substantial number of liquid arteries extend transversely through the wicks adjacent the respective upper and lower surfaces of the housing, the arteries extending through the wall of the housing between the vapor channels and the main liquid channel and open into the main liquid channel. Liquid from the main channel enters the artery at the heat input end, wets the wick and is vaporized. When the vapor is cooled at the heat output end, the condensed vapor refills the wick and the liquid reenters the main liquid channel.

  9. Enabling IP Header Compression in COTS Routers via Frame Relay on a Simplex Link

    NASA Technical Reports Server (NTRS)

    Nguyen, Sam P.; Pang, Jackson; Clare, Loren P.; Cheng, Michael K.

    2010-01-01

    NASA is moving toward a networkcentric communications architecture and, in particular, is building toward use of Internet Protocol (IP) in space. The use of IP is motivated by its ubiquitous application in many communications networks and in available commercial off-the-shelf (COTS) technology. The Constellation Program intends to fit two or more voice (over IP) channels on both the forward link to, and the return link from, the Orion Crew Exploration Vehicle (CEV) during all mission phases. Efficient bandwidth utilization of the links is key for voice applications. In Voice over IP (VoIP), the IP packets are limited to small sizes to keep voice latency at a minimum. The common voice codec used in VoIP is G.729. This new algorithm produces voice audio at 8 kbps and in packets of 10-milliseconds duration. Constellation has designed the VoIP communications stack to use the combination of IP/UDP/RTP protocols where IP carries a 20-byte header, UDP (User Datagram Protocol) carries an 8-byte header, and RTP (Real Time Transport Protocol) carries a 12-byte header. The protocol headers total 40 bytes and are equal in length to a 40-byte G.729 payload, doubling the VoIP latency. Since much of the IP/UDP/RTP header information does not change from IP packet to IP packet, IP/UDP/RTP header compression can avoid transmission of much redundant data as well as reduce VoIP latency. The benefits of IP header compression are more pronounced at low data rate links such as the forward and return links during CEV launch. IP/UDP/RTP header compression codecs are well supported by many COTS routers. A common interface to the COTS routers is through frame relay. However, enabling IP header compression over frame relay, according to industry standard (Frame Relay IP Header Compression Agreement FRF.20), requires a duplex link and negotiations between the compressor router and the decompressor router. In Constellation, each forward to and return link from the CEV in space is treated

  10. Vibrational Heat Transport in Molecular Junctions.

    PubMed

    Segal, Dvira; Agarwalla, Bijay Kumar

    2016-05-27

    We review studies of vibrational energy transfer in a molecular junction geometry, consisting of a molecule bridging two heat reservoirs, solids or large chemical compounds. This setup is of interest for applications in molecular electronics, thermoelectrics, and nanophononics, and for addressing basic questions in the theory of classical and quantum transport. Calculations show that system size, disorder, structure, dimensionality, internal anharmonicities, contact interaction, and quantum coherent effects are factors that combine to determine the predominant mechanism (ballistic/diffusive), effectiveness (poor/good), and functionality (linear/nonlinear) of thermal conduction at the nanoscale. We review recent experiments and relevant calculations of quantum heat transfer in molecular junctions. We recount the Landauer approach, appropriate for the study of elastic (harmonic) phononic transport, and outline techniques that incorporate molecular anharmonicities. Theoretical methods are described along with examples illustrating the challenge of reaching control over vibrational heat conduction in molecules.

  11. Vibrational Heat Transport in Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Segal, Dvira; Agarwalla, Bijay Kumar

    2016-05-01

    We review studies of vibrational energy transfer in a molecular junction geometry, consisting of a molecule bridging two heat reservoirs, solids or large chemical compounds. This setup is of interest for applications in molecular electronics, thermoelectrics, and nanophononics, and for addressing basic questions in the theory of classical and quantum transport. Calculations show that system size, disorder, structure, dimensionality, internal anharmonicities, contact interaction, and quantum coherent effects are factors that combine to determine the predominant mechanism (ballistic/diffusive), effectiveness (poor/good), and functionality (linear/nonlinear) of thermal conduction at the nanoscale. We review recent experiments and relevant calculations of quantum heat transfer in molecular junctions. We recount the Landauer approach, appropriate for the study of elastic (harmonic) phononic transport, and outline techniques that incorporate molecular anharmonicities. Theoretical methods are described along with examples illustrating the challenge of reaching control over vibrational heat conduction in molecules.

  12. Miniature Heat Transport System for Nanosatellite Technology

    NASA Technical Reports Server (NTRS)

    Douglas, Donya M,

    1999-01-01

    The scientific understanding of key physical processes between the Sun and the Earth require simultaneous measurements from many vantage points in space. Nano-satellite technologies will enable a class of constellation missions for the NASA Space Science Sun-Earth Connections. This recent emphasis on the implementation of smaller satellites leads to a requirement for development of smaller subsystems in several areas. Key technologies under development include: advanced miniaturized chemical propulsion; miniaturized sensors; highly integrated, compact electronics; autonomous onboard and ground operations; miniatures low power tracking techniques for orbit determination; onboard RF communications capable of transmitting data to the ground from far distances; lightweight efficient solar array panels; lightweight, high output battery cells; lightweight yet strong composite materials for the nano-spacecraft and deployer-ship structures. These newer smaller systems may have higher power densities and higher thermal transport requirements than seen on previous small satellites. Furthermore, the small satellites may also have a requirement to maintain thermal control through extended earth shadows, possibly up to 8 hours long. Older thermal control technology, such as heaters, thermostats, and heat pipes, may not be sufficient to meet the requirements of these new systems. Conversely, a miniature two-phase heat transport system (Mini-HTS) such as a Capillary Pumped Loop (CPL) or Loop Heat Pipe (LBP) is a viable alternative. A Mini-HTS can provide fine temperature control, thermal diode action, and a highly efficient means of heat transfer. The Mini-HTS would have power capabilities in the range of tens of watts or less and provide thermal control over typical spacecraft ranges. The Mini-HTS would allow the internal portion of the spacecraft to be thermally isolated from the external radiator, thus protecting the internal components from extreme cold temperatures during an

  13. Increased ocean heat transports and warmer climate

    NASA Technical Reports Server (NTRS)

    Rind, D.; Chandler, M.

    1991-01-01

    The impact of an increased ocean heat transport on climate is investigated in the framework of the GISS GMC model described by Hansen et al. (1983), using two scenarios: one starting from warmer polar temperatures/no sea ice and the other from the current ocean conditions. A 20-percent increase in cross-equatorial heat transport was sufficient to melt all sea ice; it resulted in a climate that was 2 C warmer for the global average, with values some 20-deg warmer at high altitudes and 1-deg warmer near the equator. It is suggested that the hydrological and dynamical changes associated with this different climate regime may be self-sustaining and, as such, would account for the high-latitude warmth of climates in the Mesozoic and Tertiary periods and the decadenal-scale climate fluctuations during the Holocene.

  14. Vapor-phase heat-transport system

    NASA Astrophysics Data System (ADS)

    Hedstrom, J. C.

    1983-11-01

    A vapor-phase heat-transport system is being tested in one of the passive test cells at Los Alamos. The system consists of one selective-surface collector and a condenser inside a water storage tank. The refrigerant, R-11, can be returned to the collector by gravity or with a pump. Results from several operating configurations are presented, together with a comparison with other passive systems. A new self-pumping concept is presented.

  15. Vapor-phase heat-transport system

    NASA Astrophysics Data System (ADS)

    Hedstrom, J. C.

    A vapor-phase heat-transport system is being tested in one of the passive test cells at Los Alamos. The system consists of one selective-surface collector and a condenser inside a water storage tank. The refrigerant, R-11, can be returned to the collector by gravity or with a pump. Results from several operating configurations are presented, together with a comparison with other passive systems. A new self-pumping concept is presented.

  16. Implementation and Evaluation of the Enhanced Header Compression (IPHC) for 6LoWPAN

    NASA Astrophysics Data System (ADS)

    Ludovici, Alessandro; Calveras, Anna; Catalan, Marisa; Gómez, Carles; Paradells, Josep

    6LoWPAN defines how to carry IPv6 packets over IEEE 802.15.4 low power wireless or sensor networks. Limited bandwidth, memory and energy resources require a careful application of IPv6 in a LoWPAN. The IEEE 802.15.4 standard defines a maximum frame size of 127 bytes that decreases to 102 bytes considering the header overhead. A further reduction is due to the security, network and transport protocols header overhead that, in case of IPv6 and UDP, leave only 33 bytes for application data. A compression algorithm is necessary in order to reduce the overhead and save space in data payload. This paper describes and compares the proposed IPv6 header compression mechanisms for 6LoWPAN environments.

  17. Fast atomic transport without vibrational heating

    SciTech Connect

    Torrontegui, E.; Ibanez, S.; Chen Xi; Ruschhaupt, A.; Guery-Odelin, D.; Muga, J. G.

    2011-01-15

    We use the dynamical invariants associated with the Hamiltonian of an atom in a one dimensional moving trap to inverse engineer the trap motion and perform fast atomic transport without final vibrational heating. The atom is driven nonadiabatically through a shortcut to the result of adiabatic, slow trap motion. For harmonic potentials this only requires designing appropriate trap trajectories, whereas perfect transport in anharmonic traps may be achieved by applying an extra field to compensate the forces in the rest frame of the trap. The results can be extended to atom stopping or launching. The limitations due to geometrical constraints, energies, and accelerations involved are analyzed along with the relation to previous approaches based on classical trajectories or ''fast-forward'' and ''bang-bang'' methods, which can be integrated in the invariant-based framework.

  18. Thermal Transport Model for Heat Sink Design

    NASA Technical Reports Server (NTRS)

    Chervenak, James A.; Kelley, Richard L.; Brown, Ari D.; Smith, Stephen J.; Kilbourne, Caroline a.

    2009-01-01

    A document discusses the development of a finite element model for describing thermal transport through microcalorimeter arrays in order to assist in heat-sinking design. A fabricated multi-absorber transition edge sensor (PoST) was designed in order to reduce device wiring density by a factor of four. The finite element model consists of breaking the microcalorimeter array into separate elements, including the transition edge sensor (TES) and the silicon substrate on which the sensor is deposited. Each element is then broken up into subelements, whose surface area subtends 10 10 microns. The heat capacity per unit temperature, thermal conductance, and thermal diffusivity of each subelement are the model inputs, as are the temperatures of each subelement. Numerical integration using the Finite in Time Centered in Space algorithm of the thermal diffusion equation is then performed in order to obtain a temporal evolution of the subelement temperature. Thermal transport across interfaces is modeled using a thermal boundary resistance obtained using the acoustic mismatch model. The document concludes with a discussion of the PoST fabrication. PoSTs are novel because they enable incident x-ray position sensitivity with good energy resolution and low wiring density.

  19. Modeling Vapor and Heat Transport on Io

    NASA Astrophysics Data System (ADS)

    Allen, D. R.; Howell, R. R.

    2012-12-01

    length scales of sulfur deposition that were intermediate between our Ingersoll adapted model and the Moreno scaled lengths. Assumptions that we made in order to simplify our models are likely contributing to the differences in length scales between our radial model and the Moreno model. Results from these sulfur transport models will be presented. In addition to the sulfur transport models, we are beginning to develop models to investigate the role of sulfur in modifying the temperatures. Models of horizontal transport of sulfur in and around the patera and of vertical transport of sulfur from depth within the patera will explore the role of sulfur in modifying the temperatures. Horizontal transport models probe the ability of sulfur to redistribute the heat around the patera creating lower temperatures and uniform temperature profiles. Vertical transport models explore the ability to bring heat from depth and to produce the light deposits in the images. This work was supported in part by NASA JDAP grant NNX09AE06G. References: Ingersoll, A.P. (1989), Io meteorology: How atmospheric pressure is controlled locally by volcanoes and surface frosts, Icarus, 81, 298-313. Moreno, M.A., G. Schubert, J. Baumgardner, M.G. Kivelson, and D.A. Paige (1991), Io's volcanic and sublimation atmospheres, Icarus, 93, 63-81.

  20. Convective heat transport in geothermal systems

    SciTech Connect

    Lippmann, M.J.; Bodvarsson, G.S.

    1986-08-01

    Most geothermal systems under exploitation for direct use or electrical power production are of the hydrothermal type, where heat is transferred essentially by convection in the reservoir, conduction being secondary. In geothermal systems, buoyancy effects are generally important, but often the fluid and heat flow patterns are largely controlled by geologic features (e.g., faults, fractures, continuity of layers) and location of recharge and discharge zones. During exploitation, these flow patterns can drastically change in response to pressure and temperature declines, and changes in recharge/discharge patterns. Convective circulation models of several geothermal systems, before and after start of fluid production, are described, with emphasis on different characteristics of the systems and the effects of exploitation on their evolution. Convective heat transport in geothermal fields is discussed, taking into consideration (1) major geologic features; (2) temperature-dependent rock and fluid properties; (3) fracture- versus porous-medium characteristics; (4) single- versus two-phase reservoir systems; and (5) the presence of noncondensible gases.

  1. Apparatus for downward transport of heat

    DOEpatents

    Neeper, D.A.; Hedstrom, J.C.

    1985-08-05

    An apparatus for the downward transport of heat by vaporization of a working fluid, usually from a collector which can be powered by the sun to a condenser which drains the condensed working fluid to a lower reservoir, is controled by a control valve which is operationally dependent upon the level of working fluid in either the lower reservoir or an upper reservoir which feeds the collector. Condensed working fluid is driven from the lower to the upper reservoir by vaporized working fluid whose flow is controled by the controll valve. The upper reservoir is in constant communication with the condenser which prevents a buildup in temperature/pressure as the apparatus goes through successive pumping cycles.

  2. Functionalization mediates heat transport in graphene nanoflakes

    PubMed Central

    Han, Haoxue; Zhang, Yong; Wang, Nan; Samani, Majid Kabiri; Ni, Yuxiang; Mijbil, Zainelabideen Y.; Edwards, Michael; Xiong, Shiyun; Sääskilahti, Kimmo; Murugesan, Murali; Fu, Yifeng; Ye, Lilei; Sadeghi, Hatef; Bailey, Steven; Kosevich, Yuriy A.; Lambert, Colin J.; Liu, Johan; Volz, Sebastian

    2016-01-01

    The high thermal conductivity of graphene and few-layer graphene undergoes severe degradations through contact with the substrate. Here we show experimentally that the thermal management of a micro heater is substantially improved by introducing alternative heat-escaping channels into a graphene-based film bonded to functionalized graphene oxide through amino-silane molecules. Using a resistance temperature probe for in situ monitoring we demonstrate that the hotspot temperature was lowered by ∼28 °C for a chip operating at 1,300 W cm−2. Thermal resistance probed by pulsed photothermal reflectance measurements demonstrated an improved thermal coupling due to functionalization on the graphene–graphene oxide interface. Three functionalization molecules manifest distinct interfacial thermal transport behaviour, corroborating our atomistic calculations in unveiling the role of molecular chain length and functional groups. Molecular dynamics simulations reveal that the functionalization constrains the cross-plane phonon scattering, which in turn enhances in-plane heat conduction of the bonded graphene film by recovering the long flexural phonon lifetime. PMID:27125636

  3. Functionalization mediates heat transport in graphene nanoflakes

    NASA Astrophysics Data System (ADS)

    Han, Haoxue; Zhang, Yong; Wang, Nan; Samani, Majid Kabiri; Ni, Yuxiang; Mijbil, Zainelabideen Y.; Edwards, Michael; Xiong, Shiyun; Sääskilahti, Kimmo; Murugesan, Murali; Fu, Yifeng; Ye, Lilei; Sadeghi, Hatef; Bailey, Steven; Kosevich, Yuriy A.; Lambert, Colin J.; Liu, Johan; Volz, Sebastian

    2016-04-01

    The high thermal conductivity of graphene and few-layer graphene undergoes severe degradations through contact with the substrate. Here we show experimentally that the thermal management of a micro heater is substantially improved by introducing alternative heat-escaping channels into a graphene-based film bonded to functionalized graphene oxide through amino-silane molecules. Using a resistance temperature probe for in situ monitoring we demonstrate that the hotspot temperature was lowered by ~28 °C for a chip operating at 1,300 W cm-2. Thermal resistance probed by pulsed photothermal reflectance measurements demonstrated an improved thermal coupling due to functionalization on the graphene-graphene oxide interface. Three functionalization molecules manifest distinct interfacial thermal transport behaviour, corroborating our atomistic calculations in unveiling the role of molecular chain length and functional groups. Molecular dynamics simulations reveal that the functionalization constrains the cross-plane phonon scattering, which in turn enhances in-plane heat conduction of the bonded graphene film by recovering the long flexural phonon lifetime.

  4. Heating and Cooling System Design for a Modern Transportable Container

    SciTech Connect

    Berger, Jason E.

    2015-06-01

    Sandia National Laboratories (SNL) has been tasked with the design of a modern transportable container (MTC) for use in high reliability transportation environments. The container is required to transport cargo capable of generating its own heat and operate under the United States’ climatic extremes. In response to these requirements, active heating and cooling is necessary to maintain a controlled environment inside the container. The following thesis project documents the design of an active heating, active cooling, and combined active heating and cooling system (now referred to as active heating and cooling systems) through computational thermal analyses, scoping of commercial system options, and mechanical integration with the container’s structure.

  5. Heat pipe radiators for space

    NASA Technical Reports Server (NTRS)

    Sellers, J. P.

    1976-01-01

    Analysis of the data heat pipe radiator systems tested in both vacuum and ambient environments was continued. The systems included (1) a feasibility VCHP header heat-pipe panel, (2) the same panel reworked to eliminate the VCHP feature and referred to as the feasibility fluid header panel, and (3) an optimized flight-weight fluid header panel termed the 'prototype.' A description of freeze-thaw thermal vacuum tests conducted on the feasibility VCHP was included. In addition, the results of ambient tests made on the feasibility fluid header are presented, including a comparison with analytical results. A thermal model of a fluid header heat pipe radiator was constructed and a computer program written. The program was used to make a comparison of the VCHP and fluid-header concepts for both single and multiple panel applications. The computer program was also employed for a parametric study, including optimum feeder heat pipe spacing, of the prototype fluid header.

  6. ONE MILLION GALLON WATER TANK, PUMP HEADER PIPE (AT LEFT), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    ONE MILLION GALLON WATER TANK, PUMP HEADER PIPE (AT LEFT), HEADER BYPASS PIPE (AT RIGHT), AND PUMPHOUSE FOUNDATIONS. Looking northeast - Edwards Air Force Base, Air Force Rocket Propulsion Laboratory, Flame Deflector Water System, Test Area 1-120, north end of Jupiter Boulevard, Boron, Kern County, CA

  7. Possible role of oceanic heat transport in Early Eocene climate

    NASA Astrophysics Data System (ADS)

    Sloan, L. Cirbus; Walker, James C. G.; Moore, T. C.

    1995-04-01

    Increased oceanic heat transport has often been cited as a means of maintaining warm high-latitude surface temperatures in many intervals of the geologic past, including the early Eocene. Although the excess amount of oceanic heat transport required by warm high latitude sea surface temperatures can be calculated empirically, determining how additional oceanic heat transport would take place has yet to be accomplished. That the mechanisms of enhanced poleward oceanic heat transport remain undefined in paleoclimate reconstructions is an important point that is often overlooked. Using early Eocene climate as an example, we consider various ways to produce enhanced poleward heat transport and latitudinal energy redistribution of the sign and magnitude required by interpreted early Eocene conditions. Our interpolation of early Eocene paleotemperature data indicate that an ˜30% increase in poleward heat transport would be required to maintain Eocene high-latitude temperatures. This increased heat transport appears difficult to accomplish by any means of ocean circulation if we use present ocean circulation characteristics to evaluate early Eocene rates. Either oceanic processes were very different from those of the present to produce the early Eocene climate conditions or oceanic heat transport was not the primary cause of that climate. We believe that atmospheric processes, with contributions from other factors, such as clouds, were the most likely primary cause of early Eocene climate.

  8. Possible role of oceanic heat transport in early Eocene climate.

    PubMed

    Sloan, L C; Walker, J C; Moore, T C

    1995-04-01

    Increased oceanic heat transport has often been cited as a means of maintaining warm high-latitude surface temperatures in many intervals of the geologic past, including the early Eocene. Although the excess amount of oceanic heat transport required by warm high latitude sea surface temperatures can be calculated empirically, determining how additional oceanic heat transport would take place has yet to be accomplished. That the mechanisms of enhanced poleward oceanic heat transport remain undefined in paleoclimate reconstructions is an important point that is often overlooked. Using early Eocene climate as an example, we consider various ways to produce enhanced poleward heat transport and latitudinal energy redistribution of the sign and magnitude required by interpreted early Eocene conditions. Our interpolation of early Eocene paleotemperature data indicate that an approximately 30% increase in poleward heat transport would be required to maintain Eocene high-latitude temperatures. This increased heat transport appears difficult to accomplish by any means of ocean circulation if we use present ocean circulation characteristics to evaluate early Eocene rates. Either oceanic processes were very different from those of the present to produce the early Eocene climate conditions or oceanic heat transport was not the primary cause of that climate. We believe that atmospheric processes, with contributions from other factors, such as clouds, were the most likely primary cause of early Eocene climate.

  9. Electric heating for high-temperature heat transport fluids

    NASA Astrophysics Data System (ADS)

    Holmes, J. T.

    1985-12-01

    Recent experiences with electric resistance heaters at the solar Central Receiver Test Facility are described. These heaters are used to preheat or maintain equipment used with molten nitrate salt or liquid sodium heat transfer fluids. Results of extensive testing performed to improve the reliability of similar heating systems used in the development program for the sodium-cooled liquid metal fast breeder nuclear reactor are also reviewed. Recommendations are made for increasing the reliability of trace heating systems for high-melting-point heat transfer fluids including thermal design, heating element selection, installation, insulation, and controls.

  10. Development and testing of heat transport fluids for use in active solar heating and cooling systems

    NASA Technical Reports Server (NTRS)

    Parker, J. C.

    1981-01-01

    Work on heat transport fluids for use with active solar heating and cooling systems is described. Program objectives and how they were accomplished including problems encountered during testing are discussed.

  11. Increased Efficiency Thermoelectric Generator With Convective Heat Transport

    DTIC Science & Technology

    2011-02-25

    term in the denominator is the reversible Seebeck thermal power input. The second and third terms are, respectively, Joule heating and conductive heat...heat transport functions, respectively, for Joule heating and conduction from the hot to cold ends. Figure 1 presents the effect of δ on efficiency...present, as it facilitates the convective effect when present. There is to be no possibility of a convective effect as being studied during this

  12. Warmtetransport in Kleding bij Aanstraling met Warmte (Heat Transport in Clothing during Irradiation with Heat)

    DTIC Science & Technology

    1990-01-22

    the thermal insulation of clothing . Ergonomics 2S, 1617-1632. Nielsen, B., Kasson, K. en Aschengreen, F.E. (1988). Heat balance during exercise in...the sun. Eur. J. Appl. Physiol. 58, 189-196. Nielsen, B. (1989). Solar heat load: heat balance during exercise in clothed subjects. Manuscript voor Eur...Institute for Perception, Soesterberg, The Netherlands Heat transport in clothing during irradiation vith heat A.M.J. Pieters and W.A. Lotens ABSTRACT A

  13. Experimental Study of Heat Transport in Fractured Network

    NASA Astrophysics Data System (ADS)

    Pastore, Nicola; Cherubini, Claudia; Giasi, Concetta I.; Allegretti, Nicoletta M.; Redondo, Jose M.; Tarquis, Ana Maria

    2015-04-01

    Fractured rocks play an important role in transport of natural resources or contaminants transport through subsurface systems. In recent years, interest has grown in investigating heat transport by means of tracer tests, driven by the important current development of geothermal applications. In literature different methods are available for predicting thermal breakthrough in fractured reservoirs based on the information coming from tracer tests. Geothermal energy is one of the largest sources of renewable energies that are extracted from the earth. The growing interest in this new energy source has stimulated attempts to develop methods and technologies for extracting energy also from ground resource at low temperature. An example is the exploitation of low enthalpy geothermal energy that can be obtained at any place with the aid of ground-source heat pump system from the soil, rock and groundwater. In such geothermal systems the fluid movement and thermal behavior in the fractured porous media is very important and critical. Existing theory of fluid flow and heat transport through porous media is of limited usefulness when applied to fractured rocks. Many field and laboratory tracer tests in fractured media show that fracture -matrix exchange is more significant for heat than mass tracers, thus thermal breakthrough curves (BTCs) are strongly controlled by matrix thermal diffusivity. In this study the behaviour of heat transport in a fractured network at bench scale has been investigated. Heat tracer tests on an artificially created fractured rock sample have been carried out. The observed thermal BTCs obtained with six thermocouple probes located at different locations in the fractured medium have been modeled with the Explicit Network Model (ENM) based an adaptation of Tang's solution for solute transport in a semi-infinite single fracture embedded in a porous matrix. The ENM model is able to represent the behavior of observed heat transport except where the

  14. An Overview of Liquid Fluoride Salt Heat Transport Technology

    SciTech Connect

    Cetiner, Mustafa Sacit; Holcomb, David Eugene

    2010-01-01

    Liquid fluoride salts are a leading candidate heat transport medium for high-temperature applications. This report provides an overview of the current status of liquid salt heat transport technology. The report includes a high-level, parametric evaluation of liquid fluoride salt heat transport loop performance to allow intercomparisons between heat-transport fluid options as well as providing an overview of the properties and requirements for a representative loop. Much of the information presented here derives from the earlier molten salt reactor program and a significant advantage of fluoride salts, as high temperature heat transport media is their consequent relative technological maturity. The report also includes a compilation of relevant thermophysical properties of useful heat transport fluoride salts. Fluoride salts are both thermally stable and with proper chemistry control can be relatively chemically inert. Fluoride salts can, however, be highly corrosive depending on the container materials selected, the salt chemistry, and the operating procedures used. The report also provides an overview of the state-of-the-art in reduction-oxidation chemistry control methodologies employed to minimize salt corrosion as well as providing a general discussion of heat transfer loop operational issues such as start-up procedures and freeze-up vulnerability.

  15. Meridional heat transport at the onset of winter stratospheric warming

    NASA Technical Reports Server (NTRS)

    Conte, M.

    1981-01-01

    A continuous vertical flow of energy toward high altitude was verified. This process produced a dynamic instability of the stratospheric polar vortex. A meridional heat transport ws primed toward the north, which generated a warming trend.

  16. Decomposing the meridional heat transport in the climate system

    NASA Astrophysics Data System (ADS)

    Yang, Haijun; Li, Qing; Wang, Kun; Sun, Yu; Sun, Daoxun

    2015-05-01

    The meridional heat transport (MHT) in the climate system is investigated using a state-of-the-art coupled climate model (CESM1.0). This work decomposes the MHT and studies their physics in detail. The meridional ocean heat transport (OHT) can be decomposed into the contributions from the Euler mean circulation, bolus circulation, sub-mesoscale circulation and dissipation. The Euler mean heat transport dominates the total OHT in most latitudes, except that in the Southern Ocean (40-50°S) where the OHT is determined by the eddy-induced circulation and dissipation. In the Indo-Pacific the OHT is fulfilled by the wind-driven circulation, which dominates the total global OHT in the tropics. In the Atlantic the OHT is carried by both the wind-driven circulation and the thermohaline circulation, and the latter dominates the total OHT in the mid-high latitudes. The meridional atmosphere heat transport consists of the dry static energy (DSE) and latent energy (LE) transport. In the tropics the LE transport is equatorward and compensates partially the poleward DSE transport. In the extratropics, the LE and DSE are poleward and reinforce one another, both of which are dominated by the eddy components. The LE transport can be considered as the "joint air-sea mode" since the ocean controls the moisture supply. It can be also precisely obtained from the evaporation minus precipitation over the ocean and thus this work quantifies the individual ocean basin contributions to the LE transport.

  17. 111. AIR CONDENSATE PUMP. NOTE MAIN DISCHARGE HEADER ABOVE STEAMEND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    111. AIR CONDENSATE PUMP. NOTE MAIN DISCHARGE HEADER ABOVE STEAM-END CYLINDER. NOTE ALSO, THE 30' DISCHARGE VALVE AND ACTUATER TO THE LEFT OF THE PUMP. - Lakeview Pumping Station, Clarendon & Montrose Avenues, Chicago, Cook County, IL

  18. Detail of second floor window with splayed brick header, east ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of second floor window with splayed brick header, east elevation; camera facing west. - Mare Island Naval Shipyard, Rubber Shop, California Avenue, west side across from Dry Dock 1 near Ninth Street, Vallejo, Solano County, CA

  19. Latent heat effects in subsurface heat transport modelling and their impact on palaeotemperature reconstructions

    NASA Astrophysics Data System (ADS)

    Mottaghy, Darius; Rath, Volker

    2006-01-01

    In cold regions the thermal regime is strongly affected by freezing or melting processes, consuming or releasing large amounts of latent heat. This changes enthalpy by orders of magnitude. We present a numerical approach for the implementation of these effects into a 3-D finite-difference heat transport model. The latent heat effect can be handled by substituting an apparent heat capacity for the volumetric heat capacity of unfrozen soil in the heat transfer equation. The model is verified by the analytical solution of the heat transport equation including phase change. We found significant deviations of temperature profiles when applying the latent heat effect on forward calculations of deep temperature logs. Ground surface temperature histories derived from synthetic data and field data from NE Poland underline the importance of considering freezing processes. In spite of its limitations, the proposed method is appropriate for the study of long-period climatic changes.

  20. Thaw flow control for liquid heat transport systems

    DOEpatents

    Kirpich, Aaron S.

    1989-01-01

    In a liquid metal heat transport system including a source of thaw heat for use in a space reactor power system, the thaw flow throttle or control comprises a fluid passage having forward and reverse flow sections and a partition having a plurality of bleed holes therein to enable fluid flow between the forward and reverse sections. The flow throttle is positioned in the system relatively far from the source of thaw heat.

  1. An Overview of Liquid Fluoride Salt Heat Transport Systems

    SciTech Connect

    Holcomb, David Eugene; Cetiner, Sacit M

    2010-09-01

    Heat transport is central to all thermal-based forms of electricity generation. The ever increasing demand for higher thermal efficiency necessitates power generation cycles transitioning to progressively higher temperatures. Similarly, the desire to provide direct thermal coupling between heat sources and higher temperature chemical processes provides the underlying incentive to move toward higher temperature heat transfer loops. As the system temperature rises, the available materials and technology choices become progressively more limited. Superficially, fluoride salts at {approx}700 C resemble water at room temperature being optically transparent and having similar heat capacity, roughly three times the viscosity, and about twice the density. Fluoride salts are a leading candidate heat-transport material at high temperatures. Fluoride salts have been extensively used in specialized industrial processes for decades, yet they have not entered widespread deployment for general heat transport purposes. This report does not provide an exhaustive screening of potential heat transfer media and other high temperature liquids such as alkali metal carbonate eutectics or chloride salts may have economic or technological advantages. A particular advantage of fluoride salts is that the technology for their use is relatively mature as they were extensively studied during the 1940s-1970s as part of the U.S. Atomic Energy Commission's program to develop molten salt reactors (MSRs). However, the instrumentation, components, and practices for use of fluoride salts are not yet developed sufficiently for commercial implementation. This report provides an overview of the current understanding of the technologies involved in liquid salt heat transport (LSHT) along with providing references to the more detailed primary information resources. Much of the information presented here derives from the earlier MSR program. However, technology has evolved over the intervening years, and

  2. Anisotropic Heat Transport in the Presence of Resonant Magnetic Perturbations

    NASA Astrophysics Data System (ADS)

    Held, Eric; Kruger, Scott

    2009-05-01

    Heat transport in the H-mode tokamak edge is significantly modified by the presence of resonant magnetic perturbations. Application of collisional transport models to this problem ignores the fact that temperatures at the top of the edge pedestal may be several keV. Here, we compare the effective radial heat transport predicted by local (diffusive) and nonlocal (integral) forms for the parallel heat flux. Accurately predicting this effective radial heat transport becomes important when significant magnetic field line stochasticity is present, as in the case of overlapping magnetic perturbations. For such cases, the integral form for the parallel heat transport correctly assesses the effects of temperature perturbations all along the magnetic field line and yields predictions that vary substantially from the diffusive closure, which relies only on the local temperature gradient. Quantitative comparisons of effective radial transport are given for single helicity and multiple helicity magnetic perturbations in cylindrical and toroidal geometry, with emphasis given to a toroidal case with a narrow pedestal width and a high temperature at the top of the pedestal. E. D. Held, J. D. Callen, C. C. Hegna, C. R. Sovinec, T. A. Gianakon,and S. E. Kruger, Phys Plasmas, 11, 2419 (2004).

  3. Anisotropic Heat Transport in the Presence of Resonant Magnetic Perturbations

    NASA Astrophysics Data System (ADS)

    Kruger, Scott; Held, Eric

    2008-11-01

    Heat transport in the H-mode tokamak edge is significantly modified by the presence of resonant magnetic perturbations. Application of collisional transport models to this problem ignores the fact that temperatures at the top of the edge pedestal may be several keV. Here, we compare the effective radial heat transport predicted by local (diffusive) and nonlocal [1] (integral) forms for the parallel heat flux. Accurately predicting this effective radial heat transport becomes important when significant magnetic field line stochasticity is present, as in the case of overlapping magnetic perturbations. For such cases, the integral form for the parallel heat transport correctly assesses the effects of temperature perturbations all along the magnetic field line and yields predictions that vary substantially from the diffusive closure, which relies only on the local temperature gradient. Quantitative comparisons of effective radial transport are given for single helicity and multiple helicity magnetic perturbations in cylindrical and toroidal geometry, with emphasis given to a toroidal case with a narrow pedestal width and a high temperature at the top of the pedestal. [0pt] [1] E. D. Held, J. D. Callen, C. C. Hegna, C. R. Sovinec, T. A. Gianakon, and S. E. Kruger, Phys Plasmas, 11, 2419 (2004).

  4. An oceanic heat transport pathway to the Amundsen Sea Embayment

    NASA Astrophysics Data System (ADS)

    Rodriguez, Angelica R.; Mazloff, Matthew R.; Gille, Sarah T.

    2016-05-01

    The Amundsen Sea Embayment (ASE) on the West Antarctic coastline has been identified as a region of accelerated glacial melting. A Southern Ocean State Estimate (SOSE) is analyzed over the 2005-2010 time period in the Amundsen Sea region. The SOSE oceanic heat budget reveals that the contribution of parameterized small-scale mixing to the heat content of the ASE waters is small compared to advection and local air-sea heat flux, both of which contribute significantly to the heat content of the ASE waters. Above the permanent pycnocline, the local air-sea flux dominates the heat budget and is controlled by seasonal changes in sea ice coverage. Overall, between 2005 and 2010, the model shows a net heating in the surface above the pycnocline within the ASE. Sea water below the permanent pycnocline is isolated from the influence of air-sea heat fluxes, and thus, the divergence of heat advection is the major contributor to increased oceanic heat content of these waters. Oceanic transport of mass and heat into the ASE is dominated by the cross-shelf input and is primarily geostrophic below the permanent pycnocline. Diagnosis of the time-mean SOSE vorticity budget along the continental shelf slope indicates that the cross-shelf transport is sustained by vorticity input from the localized wind-stress curl over the shelf break.

  5. Multi-decadal Variability of Heat Transport in the Arctic

    NASA Astrophysics Data System (ADS)

    Outten, S.; Ezau, I.

    2015-12-01

    The meridional transport of heat from the tropics to the poles, where it can be radiated out to space, is a vital component for maintaining the Earth's climate. Understanding the decadal to multi-decadal changes of these transports provides an insight into the natural variability of the climate system and into the flow of heat into the Arctic. Jacob Bjerknes proposed that the total energy transported by the climate system should remain approximately constant if the ocean heat storage and fluxes at the top-of-the-atmosphere were unchanging [Bjerknes, 1964]. Since heat is transported by the atmosphere and ocean, any large anomalies in the atmospheric heat transport should be balanced by opposing variations in the ocean heat transport, and vice versa; a process that has since been named Bjerknes Compensation. Bjerknes compensation has been identified in the 600-year control run of the Bergen Climate Model by examining the anomalies of the implied meridional heat transports in both the ocean and atmosphere (Figure 1). These anomalies show strong anti-correlation (r = -0.72, p ≤ 0.05), and a multi-decadal variability with a period of approximately 60-80 years. Spatial patterns associated with this multi-decadal variability highlight part of the underlying mechanism which occurs through changes in the sea-ice cover in the Arctic, which lead to strong ocean-atmosphere fluxes and the formation of a thermal low that changes the large scale flow over the Northern Hemisphere. The anomalies in atmospheric heat transport are not only found to be well correlated to the anomalies in Arctic sea-ice, but also to the strength of the sub-polar gyre, suggesting a possible feedback of the atmosphere to the ocean on multi-decadal timescales. Bjerknes Compensation has also been identified in the NorESM model, a member of the CMIP5 archive. Figure 1: Meridional heat transport anomalies at 67N in the atmosphere (solid) and ocean (dashed), for the 600 year control run of the

  6. Passive vapor transport solar heating systems

    SciTech Connect

    Hedstrom, J.C.; Neeper, D.A.

    1985-01-01

    In the systems under consideration, refrigerant is evaporated in a solar collector and condensed in thermal storage for space or water heating located within the building at a level below that of the collector. Condensed liquid is lifted to an accumulator above the collector by the vapor pressure generated in the collector. Tests of two systems are described, and it is concluded that one of these systems offers distinct advantages.

  7. Heat transport measurements in turbulent rotating Rayleigh-Benard convection

    SciTech Connect

    Ecke, Robert E; Liu, Yuanming

    2008-01-01

    We present experimental heat transport measurements of turbulent Rayleigh-Benard convection with rotation about a vertical axis. The fluid, water with Prandtl number ({sigma}) about 6, was confined in a cell which had a square cross section of 7.3 cm x 7.3 cm and a height of 9.4 cm. Heat transport was measured for Rayleigh numbers 2 x 10{sup 5} < Ra < 5 x 10{sup 8} and Taylor numbers 0 < Ta < 5 x 10{sup 9}. We show the variation of normalized heat transport, the Nusselt number, at fixed dimensional rotation rate {Omega}{sub D}, at fixed Ra varying Ta, at fixed Ta varying Ra, and at fixed Rossby number Ro. The scaling of heat transport in the range 10{sup 7} to about 10{sup 9} is roughly 0.29 with a Ro dependent coefficient or equivalently is also well fit by a combination of power laws of the form a Ra{sup 1/5} + b Ra{sup 1/3} . The range of Ra is not sufficient to differentiate single power law or combined power law scaling. The overall impact of rotation on heat transport in turbulent convection is assessed.

  8. The importance of planetary rotation period for ocean heat transport.

    PubMed

    Cullum, J; Stevens, D; Joshi, M

    2014-08-01

    The climate and, hence, potential habitability of a planet crucially depends on how its atmospheric and ocean circulation transports heat from warmer to cooler regions. However, previous studies of planetary climate have concentrated on modeling the dynamics of atmospheres, while dramatically simplifying the treatment of oceans, which neglects or misrepresents the effect of the ocean in the total heat transport. Even the majority of studies with a dynamic ocean have used a simple so-called aquaplanet that has no continental barriers, which is a configuration that dramatically changes the ocean dynamics. Here, the significance of the response of poleward ocean heat transport to planetary rotation period is shown with a simple meridional barrier--the simplest representation of any continental configuration. The poleward ocean heat transport increases significantly as the planetary rotation period is increased. The peak heat transport more than doubles when the rotation period is increased by a factor of ten. There are also significant changes to ocean temperature at depth, with implications for the carbon cycle. There is strong agreement between the model results and a scale analysis of the governing equations. This result highlights the importance of both planetary rotation period and the ocean circulation when considering planetary habitability.

  9. The Importance of Planetary Rotation Period for Ocean Heat Transport

    PubMed Central

    Stevens, D.; Joshi, M.

    2014-01-01

    Abstract The climate and, hence, potential habitability of a planet crucially depends on how its atmospheric and ocean circulation transports heat from warmer to cooler regions. However, previous studies of planetary climate have concentrated on modeling the dynamics of atmospheres, while dramatically simplifying the treatment of oceans, which neglects or misrepresents the effect of the ocean in the total heat transport. Even the majority of studies with a dynamic ocean have used a simple so-called aquaplanet that has no continental barriers, which is a configuration that dramatically changes the ocean dynamics. Here, the significance of the response of poleward ocean heat transport to planetary rotation period is shown with a simple meridional barrier—the simplest representation of any continental configuration. The poleward ocean heat transport increases significantly as the planetary rotation period is increased. The peak heat transport more than doubles when the rotation period is increased by a factor of ten. There are also significant changes to ocean temperature at depth, with implications for the carbon cycle. There is strong agreement between the model results and a scale analysis of the governing equations. This result highlights the importance of both planetary rotation period and the ocean circulation when considering planetary habitability. Key Words: Exoplanet—Oceans—Rotation—Climate—Habitability. Astrobiology 14, 645–650. PMID:25041658

  10. Io Volcanism: Modeling Vapor And Heat Transport

    NASA Astrophysics Data System (ADS)

    Allen, Daniel R.; Howell, R. R.

    2010-10-01

    Loki is a large, active volcanic source on Jupiter's moon, Io, whose overall temperatures are well explained by current cooling models, but there are unexplainable subtleties. Using the SO2 atmospheric models of Ingersoll (1989) as a starting point, we are investigating how volatiles, specifically sulfur, are transported on the surface and how they modify the temperatures at Loki and other volcanoes. Voyager images reveal light colored deposits, colloquially called "sulfur bergs,” on Loki's dark patera floor that may be sulfur fumaroles. Galileo images show the presence of red short-chain sulfur deposits around the patera. We are investigating the mechanisms that lead to these features. The light deposits are a few kilometers across. Calculations of the mean free paths for day time conditions on Io indicate lengths on the order of 0.1 km while poorly constrained night time conditions indicate mean free paths about 100 times greater, on the order of what is needed to produce the deposits under ballistic conditions. Preliminary calculations reveal horizontal transport length scales for diffuse transport in a collisional atmosphere of approximately 30 km for sublimating S8 sulfur at 300 K. These length scales would be sufficient to move the sulfur from the warm patera floor to the locations of the red sulfur deposits. At a typical Loki temperature of 300 K, the sublimation/evaporation rate of S8 is a few tens of microns/day. It then requires just a few days to deposit an optically thick 100 µm layer of material. Preliminary length scales and sublimation rates are thus of sufficient scale to produce the deposits. Investigations into the sulfur transport and its effect on temperature are ongoing.

  11. Effect of Joule heating on electrokinetic transport.

    PubMed

    Cetin, Barbaros; Li, Dongqing

    2008-03-01

    The Joule heating (JH) is a ubiquitous phenomenon in electrokinetic flow due to the presence of electrical potential gradient and electrical current. JH may become pronounced for applications with high electrical potential gradients or with high ionic concentration buffer solutions. In this review, an in-depth look at the effect of JH on electrokinetic processes is provided. Theoretical modeling of EOF and electrophoresis (EP) with the presence of JH is presented and the important findings from the previous studies are examined. A numerical study of a fused-silica capillary PCR reactor powered by JH is also presented to extend the discussion of favorable usage of JH.

  12. Heat transport in bubbling turbulent convection

    PubMed Central

    Lakkaraju, Rajaram; Stevens, Richard J. A. M.; Oresta, Paolo; Verzicco, Roberto; Lohse, Detlef; Prosperetti, Andrea

    2013-01-01

    Boiling is an extremely effective way to promote heat transfer from a hot surface to a liquid due to numerous mechanisms, many of which are not understood in quantitative detail. An important component of the overall process is that the buoyancy of the bubble compounds with that of the liquid to give rise to a much-enhanced natural convection. In this article, we focus specifically on this enhancement and present a numerical study of the resulting two-phase Rayleigh–Bénard convection process in a cylindrical cell with a diameter equal to its height. We make no attempt to model other aspects of the boiling process such as bubble nucleation and detachment. The cell base and top are held at temperatures above and below the boiling point of the liquid, respectively. By keeping this difference constant, we study the effect of the liquid superheat in a Rayleigh number range that, in the absence of boiling, would be between 2 × 106 and 5 × 109. We find a considerable enhancement of the heat transfer and study its dependence on the number of bubbles, the degree of superheat of the hot cell bottom, and the Rayleigh number. The increased buoyancy provided by the bubbles leads to more energetic hot plumes detaching from the cell bottom, and the strength of the circulation in the cell is significantly increased. Our results are in general agreement with recent experiments on boiling Rayleigh–Bénard convection. PMID:23696657

  13. Heat transport in bubbling turbulent convection.

    PubMed

    Lakkaraju, Rajaram; Stevens, Richard J A M; Oresta, Paolo; Verzicco, Roberto; Lohse, Detlef; Prosperetti, Andrea

    2013-06-04

    Boiling is an extremely effective way to promote heat transfer from a hot surface to a liquid due to numerous mechanisms, many of which are not understood in quantitative detail. An important component of the overall process is that the buoyancy of the bubble compounds with that of the liquid to give rise to a much-enhanced natural convection. In this article, we focus specifically on this enhancement and present a numerical study of the resulting two-phase Rayleigh-Bénard convection process in a cylindrical cell with a diameter equal to its height. We make no attempt to model other aspects of the boiling process such as bubble nucleation and detachment. The cell base and top are held at temperatures above and below the boiling point of the liquid, respectively. By keeping this difference constant, we study the effect of the liquid superheat in a Rayleigh number range that, in the absence of boiling, would be between 2 × 10(6) and 5 × 10(9). We find a considerable enhancement of the heat transfer and study its dependence on the number of bubbles, the degree of superheat of the hot cell bottom, and the Rayleigh number. The increased buoyancy provided by the bubbles leads to more energetic hot plumes detaching from the cell bottom, and the strength of the circulation in the cell is significantly increased. Our results are in general agreement with recent experiments on boiling Rayleigh-Bénard convection.

  14. High heat flux transport by microbubble emission boiling

    NASA Astrophysics Data System (ADS)

    Suzuki, Koichi

    2007-10-01

    In highly subcooled flow boiling, coalescing bubbles on the heating surface collapse to many microbubbles in the beginning of transition boiling and the heat flux increases higher than the ordinary critical heat flux. This phenomenon is called Microbubble Emission Boiling, MEB. It is generated in subcooled flow boiling and the maximum heat flux reaches about 1 kW/cm2(10 MW/m2) at liquid subcooling of 40 K and liquid velocity of 0.5 m/s for a small heating surface of 10 mm×10 mm which is placed at the bottom surface of horizontal rectangular channel. The high pressure in the channel is observed at collapse of the coalescing bubbles and it is closely related the size of coalescing bubbles. Periodic pressure waves are observed in MEB and the heat flux increases linearly in proportion to the pressure frequency. The frequency is considered the frequency of liquid-solid exchange on the heating surface. For the large sized heating surface of 50 mm length×20 mm width, the maximum heat flux obtained is 500 W/cm2 (5 MW/m2) at liquid subcooling of 40 K and liquid velocity of 0.5 m/s. This is considerably higher heat flux than the conventional cooling limit in power electronics. It is difficult to remove the high heat flux by MEB for a longer heating surface than 50 mm by single channel type. A model of advanced cooling device is introduced for power electronics by subcooled flow boiling with impinging jets. Themaxumum cooling heat flux is 500 W/cm2 (5 MW/m2). Microbubble emission boiling is useful for a high heat flux transport technology in future power electronics used in a fuel-cell power plant and a space facility.

  15. Laboratory experimental investigation of heat transport in fractured media

    NASA Astrophysics Data System (ADS)

    Cherubini, Claudia; Pastore, Nicola; Giasi, Concetta I.; Allegretti, Nicoletta Maria

    2017-01-01

    Low enthalpy geothermal energy is a renewable resource that is still underexploited nowadays in relation to its potential for development in society worldwide. Most of its applications have already been investigated, such as heating and cooling of private and public buildings, road defrosting, cooling of industrial processes, food drying systems or desalination. Geothermal power development is a long, risky and expensive process. It basically consists of successive development stages aimed at locating the resources (exploration), confirming the power generating capacity of the reservoir (confirmation) and building the power plant and associated structures (site development). Different factors intervene in influencing the length, difficulty and materials required for these phases, thereby affecting their cost. One of the major limitations related to the installation of low enthalpy geothermal power plants regards the initial development steps that are risky and the upfront capital costs that are huge. Most of the total cost of geothermal power is related to the reimbursement of invested capital and associated returns. In order to increase the optimal efficiency of installations which use groundwater as a geothermal resource, flow and heat transport dynamics in aquifers need to be well characterized. Especially in fractured rock aquifers these processes represent critical elements that are not well known. Therefore there is a tendency to oversize geothermal plants. In the literature there are very few studies on heat transport, especially on fractured media. This study is aimed at deepening the understanding of this topic through heat transport experiments in fractured networks and their interpretation. Heat transfer tests have been carried out on the experimental apparatus previously employed to perform flow and tracer transport experiments, which has been modified in order to analyze heat transport dynamics in a network of fractures. In order to model the obtained

  16. Nonlocal heat transport in a stochastic magnetic field

    SciTech Connect

    Rax, J.M.; White, R.B.

    1991-12-01

    Heat transport in a stochastic magnetic field configuration is shown to be nonlocal. Collisional transport processes, in such a disordered media, cannot always be reduced to a standard diffusion process, and the concept of a diffusion coefficient is meaningless for a wide range of typical tokamak parameters. In the nonlocal regime the relaxation of a gradient is described by an integral equation, involving a nonlocal propagator. This propagator is calculated, and the relation to previous results is elucidated. 15 refs.

  17. Miniature Heat Transport System for Spacecraft Thermal Control

    NASA Technical Reports Server (NTRS)

    Ochterbeck, Jay M.; Ku, Jentung (Technical Monitor)

    2002-01-01

    Loop heat pipes (LHP) are efficient devices for heat transfer and use the basic principle of a closed evaporation-condensation cycle. The advantage of using a loop heat pipe over other conventional methods is that large quantities of heat can be transported through a small cross-sectional area over a considerable distance with no additional power input to the system. By using LHPs, it seems possible to meet the growing demand for high-power cooling devices. Although they are somewhat similar to conventional heat pipes, LHPs have a whole set of unique properties, such as low pressure drops and flexible lines between condenser and evaporator, that make them rather promising. LHPs are capable of providing a means of transporting heat over long distances with no input power other than the heat being transported because of the specially designed evaporator and the separation of liquid and vapor lines. For LHP design and fabrication, preliminary analysis on the basis of dimensionless criteria is necessary because of certain complicated phenomena that take place in the heat pipe. Modeling the performance of the LHP and miniaturizing its size are tasks and objectives of current research. In the course of h s work, the LHP and its components, including the evaporator (the most critical and complex part of the LHP), were modeled with the corresponding dimensionless groups also being investigated. Next, analysis of heat and mass transfer processes in the LHP, selection of the most weighted criteria from known dimensionless groups (thermal-fluid sciences), heat transfer rate limits, (heat pipe theory), and experimental ratios which are unique to a given heat pipe class are discussed. In the third part of the report, two-phase flow heat and mass transfer performances inside the LHP condenser are analyzed and calculated for Earth-normal gravity and microgravity conditions. On the basis of recent models and experimental databanks, an analysis for condensing two-phase flow regimes

  18. Heat transport in the Hadean mantle: From heat pipes to plates

    NASA Astrophysics Data System (ADS)

    Kankanamge, Duminda G. J.; Moore, William B.

    2016-04-01

    Plate tectonics is a unique feature of Earth, and it plays a dominant role in transporting Earth's internally generated heat. It also governs the nature, shape, and the motion of the surface of Earth. The initiation of plate tectonics on Earth has been difficult to establish observationally, and modeling of the plate breaking process has not consistently accounted for the nature of the preplate tectonic Earth. We have performed numerical simulations of heat transport in the preplate tectonic Earth to understand the transition to plate tectonic behavior. This period of time is dominated by volcanic heat transport called the heat pipe mode of planetary cooling. These simulations of Earth's mantle include heat transport by melting and melt segregation (volcanism), Newtonian temperature-dependent viscosity, and internal heating. We show that when heat pipes are active, the lithosphere thickens and lithospheric isotherms are kept flat by the solidus. Both of these effects act to suppress plate tectonics. As volcanism wanes, conduction begins to control lithospheric thickness, and large slopes arise at the base of the lithosphere. This produces large lithospheric stress and focuses it on the thinner regions of the lithosphere resulting in plate breaking events.

  19. Unidirectional Heat Transport Driven by Rotating Cholesteric Droplets

    NASA Astrophysics Data System (ADS)

    Sato, Sayumi; Bono, Shinji; Tabe, Yuka

    2017-02-01

    When a cholesteric liquid crystal (LC) is submitted to a thermal gradient, it exhibits continuous director rotation. The phenomenon is called the Lehmann effect and is understood as a thermomechanical coupling in chiral LCs without mirror symmetry. Since the Lehmann effect is considered to possess time-reversal symmetry, one can expect the inverse process, i.e., rotating chiral LCs to pump heat along the rotational axis. We report the first observation of heat transport driven by rotating cholesteric droplets. This result suggests a new function of the cholesterics as a micro heat pump.

  20. Distribution of air-water mixtures in parallel vertical channels as an effect of the header geometry

    SciTech Connect

    Marchitto, Annalisa; Fossa, Marco; Guglielmini, Giovanni

    2009-07-15

    Uneven phase distribution in heat exchangers is a cause of severe reductions in thermal performances of refrigeration equipment. To date, no general design rules are available to avoid phase separation in manifolds with several outlet channels, and even predicting the phase and mass distribution in parallel channels is a demanding task. In the present paper, measurements of two-phase air-water distributions are reported with reference to a horizontal header supplying 16 vertical upward channels. The effects of the operating conditions, the header geometry and the inlet port nozzle were investigated in the ranges of liquid and gas superficial velocities of 0.2-1.2 and 1.5-16.5 m/s, respectively. Among the fitting devices used, the insertion of a co-axial, multi-hole distributor inside the header confirmed the possibility of greatly improving the liquid and gas flow distribution by the proper selection of position, diameter and number of the flow openings between the supplying distributor and the system of parallel channels connected to the header. (author)

  1. Heat pipe heat transport system for the Stirling Space Power Converter (SSPC)

    NASA Technical Reports Server (NTRS)

    Alger, Donald L.

    1992-01-01

    Life issues relating to a sodium heat pipe heat transport system are described. The heat pipe system provides heat, at a temperature of 1050 K, to a 50 kWe Stirling engine/linear alternator power converter called the Stirling Space Power Converter (SSPC). The converter is being developed under a National Aeronautics and Space Administration program. Since corrosion of heat pipe materials in contact with sodium can impact the life of the heat pipe, a literature review of sodium corrosion processes was performed. It was found that the impurity reactions, primarily oxygen, and dissolution of alloy elements were the two corrosion process likely to be operative in the heat pipe. Approaches that are being taken to minimize these corrosion processes are discussed.

  2. Classical heat transport in anharmonic molecular junctions: exact solutions.

    PubMed

    Liu, Sha; Agarwalla, Bijay Kumar; Wang, Jian-Sheng; Li, Baowen

    2013-02-01

    We study full counting statistics for classical heat transport through anharmonic or nonlinear molecular junctions formed by interacting oscillators. An analytical result of the steady-state heat flux for an overdamped anharmonic junction with arbitrary temperature bias is obtained. It is found that the thermal conductance can be expressed in terms of a temperature-dependent effective force constant. The role of anharmonicity is identified. We also give the general formula for the second cumulant of heat in steady state, as well as the average geometric heat flux when two system parameters are modulated adiabatically. We present an anharmonic example for which all cumulants for heat can be obtained exactly. For a bounded single oscillator model with mass we found that the cumulants are independent of the nonlinear potential.

  3. Phonon hydrodynamics and its applications in nanoscale heat transport

    NASA Astrophysics Data System (ADS)

    Guo, Yangyu; Wang, Moran

    2015-09-01

    Phonon hydrodynamics is an effective macroscopic method to study heat transport in dielectric solid and semiconductor. It has a clear and intuitive physical picture, transforming the abstract and ambiguous heat transport process into a concrete and evident process of phonon gas flow. Furthermore, with the aid of the abundant models and methods developed in classical hydrodynamics, phonon hydrodynamics becomes much easier to implement in comparison to the current popular approaches based on the first-principle method and kinetic theories involving complicated computations. Therefore, it is a promising tool for studying micro- and nanoscale heat transport in rapidly developing micro and nano science and technology. However, there still lacks a comprehensive account of the theoretical foundations, development and implementation of this approach. This work represents such an attempt in providing a full landscape, from physical fundamental and kinetic theory of phonons to phonon hydrodynamics in view of descriptions of phonon systems at microscopic, mesoscopic and macroscopic levels. Thus a systematical kinetic framework, summing up so far scattered theoretical models and methods in phonon hydrodynamics as individual cases, is established through a frame of a Chapman-Enskog solution to phonon Boltzmann equation. Then the basic tenets and procedures in implementing phonon hydrodynamics in nanoscale heat transport are presented through a review of its recent wide applications in modeling thermal transport properties of nanostructures. Finally, we discuss some pending questions and perspectives highlighted by a novel concept of generalized phonon hydrodynamics and possible applications in micro/nano phononics, which will shed more light on more profound understanding and credible applications of this new approach in micro- and nanoscale heat transport science.

  4. Mechanisms of heat transport across a nano-scale gap in heat assisted magnetic recording

    NASA Astrophysics Data System (ADS)

    Budaev, Bair V.; Bogy, David B.

    2012-06-01

    This paper compares different mechanisms of heat transport across nano-scale gaps and discusses the role of electromagnetic phenomena in heat transport in general nano-scale layered structures. The results of the analysis suggest that heat transfer across sub-5 nm gaps like that appearing in prototypes of heat assisted magnetic recording (HAMR) systems is dominated by direct intermolecular interactions between the separated bodies and is little affected by electromagnetic radiation. The analysis further suggests that local heating for HAMR with sub-5 nm spacing can be more efficiently achieved by a Joule heater that is simpler to fabricate than laser-based optical systems and is less destructive for the nano-scale transducers than laser radiation, which may lead to their structural damage and short duration life of nanoscale transducers.

  5. Self-pumping solar heating system with geyser pumping action

    SciTech Connect

    Haines, E.L.; Bartera, R.E.

    1984-10-23

    A self-pumping solar heating system having a collector including a multitude of small diameter riser tubes from which heated liquid is pumped into a header by a geyser action. A vapor condenser assures a header pressure conducive to bubble nucleation in the riser tube upper end segments. The level of liquid within the header or its outlet is higher than the liquid level in the riser tubes to produce a gravity imbalance capable of circulating heated liquid past a storage heat exchanger, below the header, and then upwardly through the closed vapor condenser in the header prior to return to a collector inlet manifold. A modified header utilizes an open vapor condenser in vapor communication with the collector header.

  6. Single-electron heat diode: Asymmetric heat transport between electronic reservoirs through Coulomb islands

    NASA Astrophysics Data System (ADS)

    Ruokola, Tomi; Ojanen, Teemu

    2011-06-01

    We introduce a functional nanoscale device, a single-electron heat diode, consisting of two quantum dots or metallic islands coupled to electronic reservoirs by tunnel contacts. Electron transport through the system is forbidden but the capacitive coupling between the two dots allows electronic fluctuations to transmit heat between the reservoirs. When the reservoir temperatures are biased in the forward direction, heat flow is enabled by a four-step sequential tunneling cycle, while in the reverse-biased configuration this process is suppressed due to Coulomb blockade effects. In an optimal setup the leakage heat current in the reverse direction is only a few percent of the forward current.

  7. Predicting Heat Transport across Multiple Devices with Neural Networks

    NASA Astrophysics Data System (ADS)

    Luna, C. J.; Budny, R. V.; Meneghini, O.; Smith, S. P.; Penna, J.

    2014-10-01

    Three multi-layer, feed-forward, back-propagation neural networks have been built and trained on heat transport data from DIII-D, TFTR, and JET, respectively. A comparative analysis shows that previous success of neural networks in predicting heat transport in DIII-D is reproduced for both TFTR and JET. The effect of using different neural network topologies has been investigated across all of the devices. It is found that the neural networks can consistently predict the total species' heat fluxes for all of the devices, however they have difficulty in predicting the individual components of the heat fluxes in presence of significant transient variations in stored energy (i.e. non steady-state conditions). Such limitation has been addressed by providing the time-derivative information of the plasma parameters that are input to the neural network. Finally, an attempt is made to draw a connection between the most consistently successful neural network topologies and their relevance to the physics of heat transport in tokamak plasmas. Supported in part by U.S. DoE Contracts No. DE-AC02-09CH1146 and No. DE-FG02-95ER54309.

  8. Studies of local electron heat transport on TFTR

    SciTech Connect

    Fredrickson, E.D.; Chang, Z.Y.; Janos, A.; McGuire, K.M.; Scott, S.; Taylor, G.

    1993-08-16

    The anomalously fast relaxation of the perturbations to the electron temperature profile caused by a sawtooth crash has been studied extensively on TFTR. We will show that on a short timescale the heat pulse is not simply diffusive as has been generally assumed, but that modeling of the heat pulse requires a transient enhancement in {chi}{sub e} following the sawtooth crash. It will be shown that the time-dependent enhancement in {chi}{sub e} predicted by non-linear thermal transport models, i.e., incremental {chi} models or the Rebut-Lallia-Watkins transport model, is much smaller than that required to explain the anomalies in the heat pulse propagation.

  9. Coupling of volatile transport and internal heat flow on Triton

    NASA Technical Reports Server (NTRS)

    Brown, Robert H.; Kirk, Randolph L.

    1994-01-01

    Recently Brown et al. (1991) showed that Triton's internal heat source could amount to 5-20% of the absorbed insolation on Triton, thus significantly affecting volatile transport and atmospheric pressure. Subsequently, Kirk and Brown (1991a) used simple analytical models of the effect of internal heat on the distribution of volatiles on Triton's surface, confirming the speculation of Brown et al. that Triton's internal heat flow could strongly couple to the surface volatile distribution. To further explore this idea, we present numerical models of the permanent distribution of nitrogen ice on Triton that include the effects of sunlight, the two-dimensional distribution of internal heat flow, the coupling of internal heat flow to the surface distribution of nitrogen ice, and the finite viscosity of nitrogen ice. From these models we conclude that: (1) The strong vertical thermal gradient induced in Triton's polar caps by internal heat-flow facilitates viscous spreading to lower latitudes, thus opposing the poleward transport of volatiles by sunlight, and, for plausible viscosities and nitrogen inventories, producing permanent caps of considerable latitudinal extent; (2) It is probable that there is a strong coupling between the surface distribution of nitrogen ice on Triton and internal heat flow; (3) Asymmetries in the spatial distribution of Triton's heat flow, possibly driven by large-scale, volcanic activity or convection in Triton's interior, can result in permanent polar caps of unequal latitudinal extent, including the case of only one permanent polar cap; (4) Melting at the base of a permanent polar cap on Triton caused by internal heat flow can significantly enhance viscous spreading, and, as an alternative to the solid-state greenhouse mechanism proposed by Brown et al. (1990), could provide the necessary energy, fluids, and/or gases to drive Triton's geyser-like plumes; (5) The atmospheric collapse predicted to occur on Triton in the next 20 years

  10. XTRN - Automatic Code Generator For C Header Files

    NASA Technical Reports Server (NTRS)

    Pieniazek, Lester A.

    1990-01-01

    Computer program XTRN, Automatic Code Generator for C Header Files, generates "extern" declarations for all globally visible identifiers contained in input C-language code. Generates external declarations by parsing input text according to syntax derived from C. Automatically provides consistent and up-to-date "extern" declarations and alleviates tedium and errors involved in manual approach. Written in C and Unix Shell.

  11. On mobile element transport in heated Abee. [chondrite thermal metamorphism

    NASA Technical Reports Server (NTRS)

    Ikramuddin, M.; Lipschutz, M. E.; Gibson, E. K., Jr.

    1979-01-01

    Abee chondrite samples were heated at 700 C for one week at 0.00001 to 0.001 atm Ne or at 0.00001 atm H2. Samples heated in Ne showed greater loss of Bi and Se and greater retention of Zn than those heated in H2. An inverse relationship between Zn retention and ambient Ne pressure was found. Seven trace elements (Ag, Co, Cs, Ga, In, Te, and Tl) were retained or lost to the same extent regardless of the heating conditions. Variations in the apparent activation energy for C above and below 700 C suggest that diffusive loss from different hosts and/or different mobile transport processes over the temperature range may have been in effect.

  12. Particle model for nonlocal heat transport in fusion plasmas.

    PubMed

    Bufferand, H; Ciraolo, G; Ghendrih, Ph; Lepri, S; Livi, R

    2013-02-01

    We present a simple stochastic, one-dimensional model for heat transfer in weakly collisional media as fusion plasmas. Energies of plasma particles are treated as lattice random variables interacting with a rate inversely proportional to their energy schematizing a screened Coulomb interaction. We consider both the equilibrium (microcanonical) and nonequilibrium case in which the system is in contact with heat baths at different temperatures. The model exhibits a characteristic length of thermalization that can be associated with an interaction mean free path and one observes a transition from ballistic to diffusive regime depending on the average energy of the system. A mean-field expression for heat flux is deduced from system heat transport properties. Finally, it is shown that the nonequilibrium steady state is characterized by long-range correlations.

  13. A simple Boltzmann transport equation for ballistic to diffusive transient heat transport

    SciTech Connect

    Maassen, Jesse Lundstrom, Mark

    2015-04-07

    Developing simplified, but accurate, theoretical approaches to treat heat transport on all length and time scales is needed to further enable scientific insight and technology innovation. Using a simplified form of the Boltzmann transport equation (BTE), originally developed for electron transport, we demonstrate how ballistic phonon effects and finite-velocity propagation are easily and naturally captured. We show how this approach compares well to the phonon BTE, and readily handles a full phonon dispersion and energy-dependent mean-free-path. This study of transient heat transport shows (i) how fundamental temperature jumps at the contacts depend simply on the ballistic thermal resistance, (ii) that phonon transport at early times approach the ballistic limit in samples of any length, and (iii) perceived reductions in heat conduction, when ballistic effects are present, originate from reductions in temperature gradient. Importantly, this framework can be recast exactly as the Cattaneo and hyperbolic heat equations, and we discuss how the key to capturing ballistic heat effects is to use the correct physical boundary conditions.

  14. Radiation Transport through cylindrical foams with heated walls

    NASA Astrophysics Data System (ADS)

    Baker, Kevin; MacLaren, Steve; Kallman, Joshua; Heinz, Ken; Hsing, Warren

    2012-10-01

    Radiation transport through low density SiO2 foams has been experimentally studied on the Omega laser. In particular these experiments examined the effects on radiation transport when the boundaries of the SiO2 foam are heated such that energy loss to the boundaries is minimized. The initial density of the SiO2 foams was determined by taking an x-ray radiograph of the foams using a monochromatic Henke source at multiple x-ray energies. The radiation drive used to both study the transport in the SiO2 foam as well as to heat the higher density CRF wall was generated in a laser-heated gold hohlraum using ˜7.5 kJ of the laser energy. The time-dependent spatial profile of the heat wave breaking out of the SiO2 foam was detected with an x-ray streak camera coupled with a soft x-ray transmission grating. The Omega DANTE diagnostic measured the radiation drive in the hohlraum and the Omega VISAR diagnostic monitored the spatial temperature gradient in the foam section of the hohlraum.

  15. Fractional-order theory of heat transport in rigid bodies

    NASA Astrophysics Data System (ADS)

    Zingales, Massimiliano

    2014-11-01

    The non-local model of heat transfer, used to describe the deviations of the temperature field from the well-known prediction of Fourier/Cattaneo models experienced in complex media, is framed in the context of fractional-order calculus. It has been assumed (Borino et al., 2011 [53], Mongioví and Zingales, 2013 [54]) that thermal energy transport is due to two phenomena: (i) A short-range heat flux ruled by a local transport equation; (ii) A long-range thermal energy transfer proportional to a distance-decaying function, to the relative temperature and to the product of the interacting masses. The distance-decaying function is assumed in the functional class of the power-law decay of the distance yielding a novel temperature equation in terms of α-order Marchaud fractional-order derivative (0⩽α⩽1). Thermodynamical consistency of the model is provided in the context of Clausius-Plank inequality. The effects induced by the boundary conditions on the temperature field are investigated for diffusive as well as ballistic local heat flux. Deviations of the temperature field from the linear distributions in the neighborhood of the thermostated zones of small-scale conductors are qualitatively predicted by the used fractional-order heat transport model, as shown by means of molecular dynamics simulations.

  16. Water, heat and salt transport through the Strait of Otranto

    NASA Astrophysics Data System (ADS)

    Yari, Sadegh; Gačić, Miroslav; Kovačević, Vedrana; Cardin, Vanessa

    2010-05-01

    The water, heat and salt transports through the Strait of Otranto are estimated applying direct method to historical current and hydrographical data (from December 94 through November 95). A variational inverse method based on a variational principle and a finite element solver is used to reconstruct the current, temperature and salinity fields across the Strait section from sparse measurements. The mean annual inflow and outflow water transport rates are estimated as 0.901±0.039 Sv and -0.939±0.315 Sv, respectively, and the net transport for the period of study is equal to -0.032±0.208 Sv. Thus, on a yearly time interval, the inflow and the outflow are practically compensated. The heat and salt transports due to advection process are estimated for five monthly periods, namely December 1994, February, May, August and November 1995. Considering these five periods representative of the seasonal cycle during the year, their average values show that there is a net heat advection into the Adriatic Sea on a yearly basis. The estimated value of advected heat and the corresponding error are 2.408±0.490 TW, which is equivalent to a heat gain of 17.37±3.53 W m-2 for the whole basin. This value is compared to the heat loss of -36±152 (std) W m-2 through the air-sea interface calculated by means of bulk formulas over the Adriatic Sea. The two values are expected to be balance each other in order to close the heat budget of the basin. The possible reasons for this difference to occur are discussed. On a yearly basis, the salt transport is estimated as an input of salt equal to 0.05×106 Kg s-1. The average annual fresh water budget is estimated as -0.002 Sv, equivalent to the mass of fresh water of 2.00×106Kg s-1 or to the level of 0.45 m yr-1 for the entire Adriatic Sea. The import of salt that is less than the gain of fresh water is in agreement with the fact that the Adriatic Sea is a dilution basin.

  17. 46 CFR 52.05-45 - Circumferential joints in pipes, tubes and headers (modifies PW-41).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Circumferential joints in pipes, tubes and headers... Circumferential joints in pipes, tubes and headers (modifies PW-41). (a) Circumferential welded joints of pipes, tubes and headers shall be as required by PW-41 of section I of the ASME Boiler and Pressure Vessel...

  18. 46 CFR 52.05-45 - Circumferential joints in pipes, tubes and headers (modifies PW-41).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Circumferential joints in pipes, tubes and headers... Circumferential joints in pipes, tubes and headers (modifies PW-41). (a) Circumferential welded joints of pipes, tubes and headers shall be as required by PW-41 of section I of the ASME Boiler and Pressure Vessel...

  19. 46 CFR 52.05-45 - Circumferential joints in pipes, tubes and headers (modifies PW-41).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Circumferential joints in pipes, tubes and headers... Circumferential joints in pipes, tubes and headers (modifies PW-41). (a) Circumferential welded joints of pipes, tubes and headers shall be as required by PW-41 of section I of the ASME Boiler and Pressure Vessel...

  20. 46 CFR 52.05-45 - Circumferential joints in pipes, tubes and headers (modifies PW-41).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Circumferential joints in pipes, tubes and headers... Circumferential joints in pipes, tubes and headers (modifies PW-41). (a) Circumferential welded joints of pipes, tubes and headers shall be as required by PW-41 of section I of the ASME Boiler and Pressure Vessel...

  1. 46 CFR 52.05-45 - Circumferential joints in pipes, tubes and headers (modifies PW-41).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Circumferential joints in pipes, tubes and headers... Circumferential joints in pipes, tubes and headers (modifies PW-41). (a) Circumferential welded joints of pipes, tubes and headers shall be as required by PW-41 of section I of the ASME Boiler and Pressure Vessel...

  2. Radiant heat test of Perforated Metal Air Transportable Package (PMATP).

    SciTech Connect

    Gronewald, Patrick James; Oneto, Robert; Mould, John; Pierce, Jim Dwight

    2003-08-01

    A conceptual design for a plutonium air transport package capable of surviving a 'worst case' airplane crash has been developed by Sandia National Laboratories (SNL) for the Japan Nuclear Cycle Development Institute (JNC). A full-scale prototype, designated as the Perforated Metal Air Transport Package (PMATP) was thermally tested in the SNL Radiant Heat Test Facility. This testing, conducted on an undamaged package, simulated a regulation one-hour aviation fuel pool fire test. Finite element thermal predictions compared well with the test results. The package performed as designed, with peak containment package temperatures less than 80 C after exposure to a one-hour test in a 1000 C environment.

  3. Local and nonlocal parallel heat transport in general magnetic fields

    SciTech Connect

    Del-Castillo-Negrete, Diego B; Chacon, Luis

    2011-01-01

    A novel approach for the study of parallel transport in magnetized plasmas is presented. The method avoids numerical pollution issues of grid-based formulations and applies to integrable and chaotic magnetic fields with local or nonlocal parallel closures. In weakly chaotic fields, the method gives the fractal structure of the devil's staircase radial temperature profile. In fully chaotic fields, the temperature exhibits self-similar spatiotemporal evolution with a stretched-exponential scaling function for local closures and an algebraically decaying one for nonlocal closures. It is shown that, for both closures, the effective radial heat transport is incompatible with the quasilinear diffusion model.

  4. Microscopic theory and quantum simulation of atomic heat transport

    NASA Astrophysics Data System (ADS)

    Marcolongo, Aris; Umari, Paolo; Baroni, Stefano

    2016-01-01

    Quantum simulation methods based on electronic-structure theory are deemed unfit to cope with atomic heat transport within the Green-Kubo formalism, because quantum-mechanical energy densities and currents are inherently ill-defined at the atomic scale. We show that, although this difficulty would also affect classical simulations, thermal conductivity is indeed insensitive to such ill-definedness by virtue of a kind of gauge invariance resulting from energy extensivity and conservation. On the basis of these findings, we derive an expression for the adiabatic energy flux from density-functional theory, which allows heat transport to be simulated using ab initio equilibrium molecular dynamics. Our methodology is demonstrated by comparing its predictions to those of classical equilibrium and ab initio non-equilibrium (Müller-Plathe) simulations for a liquid-argon model, and by applying it to heavy water at ambient conditions.

  5. Solar coronal loop heating by cross-field wave transport

    NASA Technical Reports Server (NTRS)

    Amendt, Peter; Benford, Gregory

    1989-01-01

    Solar coronal arches heated by turbulent ion-cyclotron waves may suffer significant cross-field transport by these waves. Nonlinear processes fix the wave-propagation speed at about a tenth of the ion thermal velocity, which seems sufficient to spread heat from a central core into a large cool surrounding cocoon. Waves heat cocoon ions both through classical ion-electron collisions and by turbulent stochastic ion motions. Plausible cocoon sizes set by wave damping are in roughly kilometers, although the wave-emitting core may be only 100 m wide. Detailed study of nonlinear stabilization and energy-deposition rates predicts that nearby regions can heat to values intermediate between the roughly electron volt foot-point temperatures and the about 100 eV core, which is heated by anomalous Ohmic losses. A volume of 100 times the core volume may be affected. This qualitative result may solve a persistent problem with current-driven coronal heating; that it affects only small volumes and provides no way to produce the extended warm structures perceptible to existing instruments.

  6. Climate in the Absence of Ocean Heat Transport

    NASA Astrophysics Data System (ADS)

    Rose, B. E. J.

    2015-12-01

    The energy transported by the oceans to mid- and high latitudes is small compared to the atmosphere, yet exerts an outsized influence on the climate. A key reason is the strong interaction between ocean heat transport (OHT) and sea ice extent. I quantify this by comparing a realistic control climate simulation with a slab ocean simulation in which OHT is disabled. Using the state-of-the-art CESM with a realistic present-day continental configuration, I show that the absence of OHT leads to a 23 K global cooling and massive expansion of sea ice to near 30º latitude in both hemisphere. The ice expansion is asymmetric, with greatest extent in the South Pacific and South Indian ocean basins. I discuss implications of this enormous and asymmetric climate change for atmospheric circulation, heat transport, and tropical precipitation. Parameter sensitivity studies show that the simulated climate is far more sensitive to small changes in ice surface albedo in the absence of OHT, with some perturbations sufficient to cause a runaway Snowball Earth glaciation. I conclude that the oceans are responsible for an enormous global warming by mitigating an otherwise very potent sea ice albedo feedback, but that the magnitude of this effect is still rather uncertain. I will also present some ideas on adapting the simple energy balance model to account for the enhanced sensitivity of sea ice to heating from the ocean.

  7. Heat transport modelling in EXTRAP T2R

    NASA Astrophysics Data System (ADS)

    Frassinetti, L.; Brunsell, P. R.; Cecconello, M.; Drake, J. R.

    2009-02-01

    A model to estimate the heat transport in the EXTRAP T2R reversed field pinch (RFP) is described. The model, based on experimental and theoretical results, divides the RFP electron heat diffusivity χe into three regions, one in the plasma core, where χe is assumed to be determined by the tearing modes, one located around the reversal radius, where χe is assumed not dependent on the magnetic fluctuations and one in the extreme edge, where high χe is assumed. The absolute values of the core and of the reversal χe are determined by simulating the electron temperature and the soft x-ray and by comparing the simulated signals with the experimental ones. The model is used to estimate the heat diffusivity and the energy confinement time during the flat top of standard plasmas, of deep F plasmas and of plasmas obtained with the intelligent shell.

  8. Transport phenomena of crystal growth—heat and mass transfer

    NASA Astrophysics Data System (ADS)

    Rudolph, Peter

    2010-07-01

    Selected fundamentals of transport processes and their importance for crystal growth are given. First, principal parameters and equations of heat and mass transfer, like thermal flux, radiation and diffusion are introduced. The heat- and mass- balanced melt-solid and solution-solid interface velocities are derived, respectively. The today's significance of global numeric simulation for analysis of thermo-mechanical stress and related dislocation dynamics within the growing crystal is shown. The relation between diffusion and kinetic regime is discussed. Then, thermal and solutal buoyancy-driven and Marangoni convections are introduced. Their important interplay with the diffusion boundary layer, component and particle incorporation as well as morphological interface stability is demonstrated. Non-steady crystallization phenomena (striations) caused by convective fluctuations are considered. Selected results of global 3D numeric modeling are shown. Finally, advanced methods to control heat and mass transfer by external forces, such as accelerated container rotation, ultrasonic vibration and magnetic fields are discussed.

  9. Finite element analysis of heat transport in a hydrothermal zone

    SciTech Connect

    Bixler, N.E.; Carrigan, C.R.

    1987-01-01

    Two-phase heat transport in the vicinity of a heated, subsurface zone is important for evaluation of nuclear waste repository design and estimation of geothermal energy recovery, as well as prediction of magma solidification rates. Finite element analyses of steady, two-phase, heat and mass transport have been performed to determine the relative importance of conduction and convection in a permeable medium adjacent to a hot, impermeable, vertical surface. The model includes the effects of liquid flow due to capillarity and buoyancy and vapor flow due to pressure gradients. Change of phase, with its associated latent heat effects, is also modeled. The mechanism of capillarity allows for the presence of two-phase zones, where both liquid and vapor can coexist, which has not been considered in previous investigations. The numerical method employs the standard Galerkin/finite element method, using eight-node, subparametric or isoparametric quadrilateral elements. In order to handle the extreme nonlinearities inherent in two-phase, nonisothermal, porous-flow problems, steady-state results are computed by integrating transients out to a long time (a method that is highly robust).

  10. Theoretical analysis of the maximum heat transport in triangular grooves: A study of idealized micro heat pipes

    SciTech Connect

    Peterson, G.P.; Ma, H.B.

    1995-12-31

    A mathematical model for predicting the minimum meniscus radius and the maximum heat transport in micro heat pipes is presented. In this model, a theoretical minimum meniscus radius was found and used to calculate the capillary heat transport limit based on the physical characteristics and geometry. A control volume technique was employed to determine the flow characteristics of wickless micro heat pipes, and incorporate the effects of the frictional vapor-liquid interaction on the liquid flow. Unlike previous models, this model for the first time considers the true characteristics of micro heat pipes to determine the minimum meniscus radius and the maximum heat transport capacity. In order to compare the heat transport and flow characteristics, an effective hydraulic diameter was defined and the resulting model was solved numerically. The results indicate that the heat transport capacity of micro heat pipes is strongly dependent on the apex channel angle of the liquid arteries, the contact angle of the liquid flow, the length of the heat pipe, the vapor flow velocity and characteristics, and the tilt angle. In addition, the analysis presented here provides a mechanism, which for a given set of conditions, allows the geometry to be optimized and a micro heat pipe designed with a maximum heat transport capacity. This investigation will help optimize the design of micro heat pipes, making them capable of operating at increased power levels with greater reliability.

  11. Transport lattice models of heat transport in skin with spatially heterogeneous, temperature-dependent perfusion

    PubMed Central

    Gowrishankar, TR; Stewart, Donald A; Martin, Gregory T; Weaver, James C

    2004-01-01

    Background Investigation of bioheat transfer problems requires the evaluation of temporal and spatial distributions of temperature. This class of problems has been traditionally addressed using the Pennes bioheat equation. Transport of heat by conduction, and by temperature-dependent, spatially heterogeneous blood perfusion is modeled here using a transport lattice approach. Methods We represent heat transport processes by using a lattice that represents the Pennes bioheat equation in perfused tissues, and diffusion in nonperfused regions. The three layer skin model has a nonperfused viable epidermis, and deeper regions of dermis and subcutaneous tissue with perfusion that is constant or temperature-dependent. Two cases are considered: (1) surface contact heating and (2) spatially distributed heating. The model is relevant to the prediction of the transient and steady state temperature rise for different methods of power deposition within the skin. Accumulated thermal damage is estimated by using an Arrhenius type rate equation at locations where viable tissue temperature exceeds 42°C. Prediction of spatial temperature distributions is also illustrated with a two-dimensional model of skin created from a histological image. Results The transport lattice approach was validated by comparison with an analytical solution for a slab with homogeneous thermal properties and spatially distributed uniform sink held at constant temperatures at the ends. For typical transcutaneous blood gas sensing conditions the estimated damage is small, even with prolonged skin contact to a 45°C surface. Spatial heterogeneity in skin thermal properties leads to a non-uniform temperature distribution during a 10 GHz electromagnetic field exposure. A realistic two-dimensional model of the skin shows that tissue heterogeneity does not lead to a significant local temperature increase when heated by a hot wire tip. Conclusions The heat transport system model of the skin was solved by

  12. Why convective heat transport in the solar nebula was inefficient

    NASA Technical Reports Server (NTRS)

    Cassen, P.

    1993-01-01

    The radial distributions of the effective temperatures of circumstellar disks associated with pre-main sequence (T Tauri) stars are relatively well-constrained by ground-based and spacecraft infrared photometry and radio continuum observations. If the mechanisms by which energy is transported vertically in the disks are understood, these data can be used to constrain models of the thermal structure and evolution of solar nebula. Several studies of the evolution of the solar nebula have included the calculation of the vertical transport of heat by convection. Such calculations rely on a mixing length theory of transport and some assumption regarding the vertical distribution of internal dissipation. In all cases, the results of these calculations indicate that transport by radiation dominates that by convection, even when the nebula is convectively unstable. A simple argument that demonstrates the generality (and limits) of this result, regardless of the details of mixing length theory or the precise distribution of internal heating is presented. It is based on the idea that the radiative gradient in an optically thick nebula generally does not greatly exceed the adiabatic gradient.

  13. Heat transport dynamics at a sandy intertidal zone

    NASA Astrophysics Data System (ADS)

    Befus, Kevin M.; Cardenas, M. Bayani; Erler, Dirk V.; Santos, Isaac R.; Eyre, Bradley D.

    2013-06-01

    Intertidal zones are spatially complex and temporally dynamic environments. Coastal groundwater discharge, including submarine groundwater discharge, may provide stabilizing conditions for intertidal zone permeable sediments. In this study, we integrated detailed time series temperature observations, porewater pressure measurements, and two-dimensional electrical resistivity tomography profiles to understand the coupled hydraulic-thermal regime of a tropical sandy intertidal zone in a fringing coral reef lagoon (Rarotonga, Cook Islands). We found three heating patterns across the 15 m study transect over tidal and diel periods: (1) a highly variable thermal regime dominated by swash infiltration and changes in saturation state in the upper foreshore with net heat import into the sediment, (2) a groundwater-supported underground stable, cool region just seaward of the intertidal slope break also importing heat into the subsurface, and (3) a zone of seawater recirculation that sustained consistently warm subsurface temperatures that exported heat across the sediment-water interface. Simple calculations suggested thermal conduction as the main heat transport mechanism for the shallow intertidal sediment, but deeper and/or multidimensional groundwater flow was required to explain temperature patterns beyond 20 cm depth. Temperature differences between the distinct hydrodynamic zones of the foreshore site resulted in significant thermal gradients that persisted beyond tidal and diel periods. The thermal buffering of intertidal zones by coastal groundwater systems, both at surface seeps and in the shallow subsurface, can be responsible for thermal refugia for some coastal organisms and hotspots for biogeochemical reactions.

  14. Thermal balance and quantum heat transport in nanostructures thermalized by local Langevin heat baths.

    PubMed

    Sääskilahti, K; Oksanen, J; Tulkki, J

    2013-07-01

    Modeling of thermal transport in practical nanostructures requires making tradeoffs between the size of the system and the completeness of the model. We study quantum heat transfer in a self-consistent thermal bath setup consisting of two lead regions connected by a center region. Atoms both in the leads and in the center region are coupled to quantum Langevin heat baths that mimic the damping and dephasing of phonon waves by anharmonic scattering. This approach treats the leads and the center region on the same footing and thereby allows for a simple and physically transparent thermalization of the system, enabling also perfect acoustic matching between the leads and the center region. Increasing the strength of the coupling reduces the mean-free path of phonons and gradually shifts phonon transport from ballistic regime to diffusive regime. In the center region, the bath temperatures are determined self-consistently from the requirement of zero net energy exchange between the local heat bath and each atom. By solving the stochastic equations of motion in frequency space and averaging over noise using the general fluctuation-dissipation relation derived by Dhar and Roy [J. Stat. Phys. 125, 801 (2006)], we derive the formula for thermal current, which contains the Caroli formula for phonon transmission function and reduces to the Landauer-Büttiker formula in the limit of vanishing coupling to local heat baths. We prove that the bath temperatures measure local kinetic energy and can, therefore, be interpreted as true atomic temperatures. In a setup where phonon reflections are eliminated, the Boltzmann transport equation under gray approximation with full phonon dispersion is shown to be equivalent to the self-consistent heat bath model. We also study thermal transport through two-dimensional constrictions in square lattice and graphene and discuss the differences between the exact solution and linear approximations.

  15. Parallel heat transport in integrable and chaotic magnetic fields

    SciTech Connect

    Del-Castillo-Negrete, Diego B; Chacon, Luis

    2012-01-01

    The study of transport in magnetized plasmas is a problem of fundamental interest in controlled fusion, space plasmas, and astrophysics research. Three issues make this problem particularly chal- lenging: (i) The extreme anisotropy between the parallel (i.e., along the magnetic field), , and the perpendicular, , conductivities ( / may exceed 1010 in fusion plasmas); (ii) Magnetic field lines chaos which in general complicates (and may preclude) the construction of magnetic field line coordinates; and (iii) Nonlocal parallel transport in the limit of small collisionality. Motivated by these issues, we present a Lagrangian Green s function method to solve the local and non-local parallel transport equation applicable to integrable and chaotic magnetic fields in arbitrary geom- etry. The method avoids by construction the numerical pollution issues of grid-based algorithms. The potential of the approach is demonstrated with nontrivial applications to integrable (magnetic island chain), weakly chaotic (devil s staircase), and fully chaotic magnetic field configurations. For the latter, numerical solutions of the parallel heat transport equation show that the effective radial transport, with local and non-local closures, is non-diffusive, thus casting doubts on the appropriateness of the applicability of quasilinear diffusion descriptions. General conditions for the existence of non-diffusive, multivalued flux-gradient relations in the temperature evolution are derived.

  16. Heat and salt transport throughout the North Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Yang, Lina; Yuan, Dongliang

    2016-11-01

    Absolute geostrophic currents in the North Pacific Ocean are calculated using the P-vector method and gridded Argo profiling data from January 2004 to December 2012. Three-dimensional structures and seasonal variability of meridional heat transport (MHT) and meridional salt transport (MST) are analyzed. The results show that geostrophic and Ekman components are generally opposite in sign, with the southward geostrophic component dominating in the subtropics and the northward Ekman component dominating in the tropics. In combination with the net surface heat flux and the MST through the Bering Strait, the MHT and MST of the western boundary currents (WBCs) are estimated for the first time. The results suggest that the WBCs are of great importance in maintaining the heat and salt balance of the North Pacific. The total interior MHT and MST in the tropics show nearly the same seasonal variability as that of the Ekman components, consistent with the variability of zonal wind stress. The geostrophic MHT in the tropics is mainly concentrated in the upper layers, while MST with large amplitude and annual variation can extend much deeper. This suggests that shallow processes dominate MHT in the North Pacific, while MST can be affected by deep ocean circulation. In the extratropical ocean, both MHT and MST are weak. However, there is relatively large and irregular seasonal variability of geostrophic MST, suggesting the importance of the geostrophic circulation in the MST of that area.

  17. Entropy flux and anomalous axial heat transport at the nanoscale

    NASA Astrophysics Data System (ADS)

    Sellitto, A.; Cimmelli, V. A.; Jou, D.

    2013-02-01

    The form and the role of the entropy flux in the thermodynamic analysis of the transport equations are essentially open questions in nonequilibrium thermodynamics. In particular, nonlocal heat-transport equations at nanoscale may exhibit some peculiar behaviors which seem to violate well-known statements of the second law of thermodynamics. Here we examine one of these behaviors in axial heat transport from the perspective of a generalized entropy flux, i.e., J(s)=q/T+k, and show that such a generalization allows it to be consistent with the second law. In contrast with previous formal analyses, this paper provides an explicit form for the nonclassical part of the entropy flux, that is, k=ℓ2/(λT2)∇qT·q and links it to a concrete physical phenomenon which is accessible to current experimental possibilities for systems with sufficiently long mean-free path ℓ, whereas for short enough ℓ the classical results are recovered. The derivation of the nonclassical part of the entropy flux is obtained within the frame of extended irreversible thermodynamics from two different perspectives, namely, a 13-field theory with higher-order fluxes and a 4-field theory with higher-order gradients.

  18. S-PRIME Heat Transport and Heat Rejection Subsystems Design Optimization

    NASA Astrophysics Data System (ADS)

    Moriarty, Michael P.

    1994-07-01

    The purpose of this paper is to describe the design status of the Rocketdyne space power reactor, incore, multicell, evolutionary (S-PRIME) design of the heat transport and heat rejection subsystems. The basic design concept is similar to that described previously; however, several detail design changes have resulted from changes in requirements. Improved definition of the various loop components has evolved from the performance of various trade studies. Overall layouts of the subsystem have been completed and the majority of the components are ready for preliminary design. The design will provide for the safe and reliable cooling of the nuclear reactor in a proven lightweight configuration.

  19. Momentum transport and non-local transport in heat-flux-driven magnetic reconnection in HEDP

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Fox, Will; Bhattacharjee, Amitava

    2016-10-01

    Strong magnetic fields are readily generated in high-energy-density plasmas and can affect the heat confinement properties of the plasma. Magnetic reconnection can in turn be important as an inverse process, which destroys or reconfigures the magnetic field. Recent theory has demonstrated a novel physics regime for reconnection in high-energy-density plasmas where the magnetic field is advected into the reconnection layer by plasma heat flux via the Nernst effect. In this work we elucidate the physics of the electron dissipation layer in this heat-flux-driven regime. Through fully kinetic simulation and a new generalized Ohm's law, we show that momentum transport due to the heat-flux-viscosity effect provides the dissipation mechanism to allow magnetic field line reconnection. Scaling analysis and simulations show that the characteristic width of the current sheet in this regime is several electron mean-free-paths. These results additionally show a coupling between non-local transport and momentum transport, which in turn affects the dynamics of the magnetic field. This work was supported by the U.S. Department of Energy under Contract No. DE-SC0008655.

  20. Cascade: a review of heat transport and plant design issues

    SciTech Connect

    Murray, K.A.; McDowell, M.W.

    1984-07-31

    A conceptual heat transfer loop for Cascade, a centrifugal-action solid-breeder reaction chamber, has been investigated and results are presented. The Cascade concept, a double-cone-shaped reaction chamber, rotates along its horizontal axis. Solid Li/sub 2/O or other lithium-ceramic granules are injected tangentially through each end of the chamber. The granules cascade axially from the smaller radii at the ends to the larger radius at the center, where they are ejected into a stationary granule catcher. Heat and tritium are then removed from the granules and the granules are reinjected into the chamber. A 50% dense Li/sub 2/O granule throughput of 2.8 m/sup 3//s is transferred from the reaction chamber to the steam generators via continuous bucket elevators. The granules then fall by gravity through 4 vertical steam generators. The entire transport system is maintained at the same vacuum conditions present inside the reaction chamber.

  1. Tropical Cyclone-Induced Ocean Mixing and Ocean Heat Transport

    NASA Astrophysics Data System (ADS)

    Sriver, R. L.; Huber, M.

    2004-12-01

    Turbulent mixing driven by tropical cyclones (TCs) creates cool sea surface temperature (SST) anomalies in their wakes. Restoration to `normal' SST patterns must be driven by anomalous (with respect to climatological values) surface fluxes. The upward turbulent mixing of cool water and the anomalous post-storm heat fluxes into the ocean should drive a substantial amount of poleward ocean heat transport (OHT) and significantly perturb the meridional overturning circulation. Given the sensitivity of TC activity to SSTs, strong feedbacks may exist that alter SST gradients and link TC activity to the mean climate state through OHT. A recent study estimates the magnitude of the TC-induced OHT to be on the order of 1015 Watts, representing the majority of the present-day total annual heat transported by the Earth's oceans (Emanuel, 2001, 2002, 2003). Here we analyze a variety of the latest SST and ocean heat content re-analyses datasets, including ECMWF ERA-40, and calculate SST anomalies for the majority of strong TCs occurring during the last forty years. Using SST anomalies, we attempt to quantify the annually averaged global OHT attributable to TC-induced mixing and compare between datasets and measurements/observations. Surface flux data along storm paths are extracted from ERA-40 data, and radiative energy imbalances within storm wakes are also used to calculate the implied OHT. Results are compared with satellite-based climatologies in the period in which they overlap and differences between reanalysis and satellite-based estimates of TC-induced OHT are described.

  2. Universal heat transport in Sr2RuO4.

    PubMed

    Suzuki, M; Tanatar, M A; Kikugawa, N; Mao, Z Q; Maeno, Y; Ishiguro, T

    2002-06-03

    We present the temperature dependence of the thermal conductivity kappa(T) of the unconventional superconductor Sr2RuO4 down to low temperatures ( approximately 100 mK). In the T-->0 K limit we found a finite residual term in kappa/T, providing clear evidence for the superconducting state with an unconventional pairing. The residual term remains unchanged for samples with different T(c), demonstrating the universal character of heat transport in this spin-triplet superconductor. The low-temperature behavior of kappa suggests the strong impurity scattering with a phase shift close to pi/2. A criterion for the observation of universality is experimentally deduced.

  3. Linear delta-f simulations of nonlocal electron heat transport

    NASA Astrophysics Data System (ADS)

    Brunner, S.; Valeo, E.; Krommes, J. A.

    2000-07-01

    Nonlocal electron heat transport calculations are carried out by making use of some of the techniques developed previously for extending the δf method to transport time scale simulations [S. Brunner, E. Valeo, and J. Krommes, Phys. Plasmas 6, 4504 (1999)]. By considering the relaxation of small amplitude temperature perturbations of an homogeneous Maxwellian background, only the linearized Fokker-Planck equation has to be solved, and direct comparisons can be made with the equivalent, nonlocal hydrodynamic approach [V. Yu. Bychenkov et al., Phys. Rev. Lett. 75, 4405 (1995)]. A quasineutrality-conserving algorithm is derived for computing the self-consistent electric fields driving the return currents. In the low-collisionality regime, results illustrate the importance of taking account of nonlocality in both space and time.

  4. Topological angular momentum and radiative heat transport in closed orbits

    NASA Astrophysics Data System (ADS)

    Silveirinha, Mário G.

    2017-03-01

    We study the role of topological edge states of light in the transport of thermally generated radiation in a closed cavity at a thermodynamic equilibrium. It is shown that even in the zero temperature limit—when the field fluctuations are purely quantum mechanical—there is a persistent flow of electromagnetic momentum in the cavity in closed orbits, deeply rooted in the emergence of spatially separated unidirectional edge state channels. It is highlighted that the electromagnetic orbital angular momentum of the system is nontrivial, and that the energy circulation is towards the same direction as that determined by incomplete cyclotron orbits near the cavity walls. Our findings open inroads in topological photonics and suggest that topological states of light can determine novel paradigms in the context of radiative heat transport.

  5. A Reactive-Heat-Pipe for Combined Heat Generation and Transport

    DTIC Science & Technology

    1977-12-01

    Pumping Heights for Different Temperatures. . . 70 22 Effect of Flow Losses on System Thermal Performance with No Argon in the Condenser...73 23 Flow Losses in the Vapor Transport System with Argon in the Condenser ................... 75 24 Temperature Distributions in a Reactive-Heat...shroud flow of inert gas, usually argon. The inert gas is recirculated through a vent system . The outer shroud flow prevents the direct contact

  6. Experimental determination of soil heat storage for the simulation of heat transport in a coastal wetland

    USGS Publications Warehouse

    Swain, Michael; Swain, Matthew; Lohmann, Melinda; Swain, Eric

    2012-01-01

    Two physical experiments were developed to better define the thermal interaction of wetland water and the underlying soil layer. This information is important to numerical models of flow and heat transport that have been developed to support biological studies in the South Florida coastal wetland areas. The experimental apparatus consists of two 1.32. m diameter by 0.99. m tall, trailer-mounted, well-insulated tanks filled with soil and water. A peat-sand-soil mixture was used to represent the wetland soil, and artificial plants were used as a surrogate for emergent wetland vegetation based on size and density observed in the field. The tanks are instrumented with thermocouples to measure vertical and horizontal temperature variations and were placed in an outdoor environment subject to solar radiation, wind, and other factors affecting the heat transfer. Instruments also measure solar radiation, relative humidity, and wind speed.Tests indicate that heat transfer through the sides and bottoms of the tanks is negligible, so the experiments represent vertical heat transfer effects only. The temperature fluctuations measured in the vertical profile through the soil and water are used to calibrate a one-dimensional heat-transport model. The model was used to calculate the thermal conductivity of the soil. Additionally, the model was used to calculate the total heat stored in the soil. This information was then used in a lumped parameter model to calculate an effective depth of soil which provides the appropriate heat storage to be combined with the heat storage in the water column. An effective depth, in the model, of 5.1. cm of wetland soil represents the heat storage needed to match the data taken in the tank containing 55.9. cm of peat/sand/soil mix. The artificial low-density laboratory sawgrass reduced the solar energy absorbed by the 35.6. cm of water and 55.9. cm of soil at midday by less than 5%. The maximum heat transfer into the underlying peat-sand-soil mix

  7. Experimental determination of soil heat storage for the simulation of heat transport in a coastal wetland

    NASA Astrophysics Data System (ADS)

    Swain, Michael; Swain, Matthew; Lohmann, Melinda; Swain, Eric

    2012-02-01

    SummaryTwo physical experiments were developed to better define the thermal interaction of wetland water and the underlying soil layer. This information is important to numerical models of flow and heat transport that have been developed to support biological studies in the South Florida coastal wetland areas. The experimental apparatus consists of two 1.32 m diameter by 0.99 m tall, trailer-mounted, well-insulated tanks filled with soil and water. A peat-sand-soil mixture was used to represent the wetland soil, and artificial plants were used as a surrogate for emergent wetland vegetation based on size and density observed in the field. The tanks are instrumented with thermocouples to measure vertical and horizontal temperature variations and were placed in an outdoor environment subject to solar radiation, wind, and other factors affecting the heat transfer. Instruments also measure solar radiation, relative humidity, and wind speed. Tests indicate that heat transfer through the sides and bottoms of the tanks is negligible, so the experiments represent vertical heat transfer effects only. The temperature fluctuations measured in the vertical profile through the soil and water are used to calibrate a one-dimensional heat-transport model. The model was used to calculate the thermal conductivity of the soil. Additionally, the model was used to calculate the total heat stored in the soil. This information was then used in a lumped parameter model to calculate an effective depth of soil which provides the appropriate heat storage to be combined with the heat storage in the water column. An effective depth, in the model, of 5.1 cm of wetland soil represents the heat storage needed to match the data taken in the tank containing 55.9 cm of peat/sand/soil mix. The artificial low-density laboratory sawgrass reduced the solar energy absorbed by the 35.6 cm of water and 55.9 cm of soil at midday by less than 5%. The maximum heat transfer into the underlying peat

  8. Validation of the SOLPS Parallel Heat Transport Model

    NASA Astrophysics Data System (ADS)

    Canik, J. M.; Briesemeister, A. R.; Lasnier, C. J.; McLean, A. G.; Makowski, M. A.; Leonard, A. W.; Watkins, J. G.

    2014-10-01

    Recent SOLPS 2D fluid plasma/neutrals edge transport simulations have shown a consistent under-prediction of radiated power that when accounted for allows simulations to successfully match high resolution divertor and scrape-off-layer density (ne) and temperature (Te) measurements near detached conditions in DIII-D. The parallel heat transport model has been evaluated in simulations with the upstream ne and Te and divertor heat flux matched to experiments. Simulations of L-mode discharges near detachment onset require either increased carbon sources or hydrogenic recombination radiation to match measured radiative losses. With this increase, the poloidal Te profile shows good agreement with 2D divertor Thomson scattering data, including an extended region with very low Te, which cannot be reproduced without the additional radiative loss. Similar scaling of the radiated power also results in agreement for the Te profile measured in H-mode experiments; however, in this case the plasma data show a poloidally extended region of high ne that is not captured in simulations. Work supported by the US DOE under DE-AC05-00ER22725, DE-FC02-04ER54698 and DE-AC52-07NA27344.

  9. Simulation of fluid, heat transport to estimate desert stream infiltration

    USGS Publications Warehouse

    Kulongoski, J.T.; Izbicki, J.A.

    2008-01-01

    In semiarid regions, the contribution of infiltration from intermittent streamflow to ground water recharge may be quantified by comparing simulations of fluid and heat transport beneath stream channels to observed ground temperatures. In addition to quantifying natural recharge, streamflow infiltration estimates provide a means to characterize the physical properties of stream channel sediments and to identify suitable locations for artificial recharge sites. Rates of winter streamflow infiltration along stream channels are estimated based on the cooling effect of infiltrated water on streambed sediments, combined with the simulation of two-dimensional fluid and heat transport using the computer program VS2DH. The cooling effect of ground water is determined by measuring ground temperatures at regular intervals beneath stream channels and nearby channel banks in order to calculate temperature-depth profiles. Additional data inputs included the physical, hydraulic, and thermal properties of unsaturated alluvium, and monthly ground temperatures measurements over an annual cycle. Observed temperatures and simulation results can provide estimates of the minimum threshold for deep infiltration, the variability of infiltration along stream channels, and also the frequency of infiltration events.

  10. Optomechanical design of the grating laser beam combiner (GLBC) laser diode header

    NASA Technical Reports Server (NTRS)

    Rall, Jonathan A. R.; Spadin, Paul L.

    1989-01-01

    A laser diode header has been fabricated for a grating laser beam combiner (GLBC). The laser diode header provides the thermal control, the drive electronics, and the optical system necessary for proper operation of the beam combiner. The diode header is required to provide diffraction limited optical performance while providing correction for worst case defocus aberration, 0.6 mrad excess divergence, and worst case decenter aberration, 1.0 mrad pointing error. The design of the header considered the mechanical design and the optical design together resulting in a small, self-contained header with 0.7 mrad range for focus correction and +/- 2.5 mrad of beam steering. The complete diode header is currently undergoing optical and mechanical performance testing.

  11. Surface flux and ocean heat transport convergence contributions to seasonal and interannual variations of ocean heat content

    NASA Astrophysics Data System (ADS)

    Roberts, C. D.; Palmer, M. D.; Allan, R. P.; Desbruyeres, D. G.; Hyder, P.; Liu, C.; Smith, D.

    2017-01-01

    We present an observation-based heat budget analysis for seasonal and interannual variations of ocean heat content (H) in the mixed layer (Hmld) and full-depth ocean (Htot). Surface heat flux and ocean heat content estimates are combined using a novel Kalman smoother-based method. Regional contributions from ocean heat transport convergences are inferred as a residual and the dominant drivers of Hmld and Htot are quantified for seasonal and interannual time scales. We find that non-Ekman ocean heat transport processes dominate Hmld variations in the equatorial oceans and regions of strong ocean currents and substantial eddy activity. In these locations, surface temperature anomalies generated by ocean dynamics result in turbulent flux anomalies that drive the overlying atmosphere. In addition, we find large regions of the Atlantic and Pacific oceans where heat transports combine with local air-sea fluxes to generate mixed layer temperature anomalies. In all locations, except regions of deep convection and water mass transformation, interannual variations in Htot are dominated by the internal rearrangement of heat by ocean dynamics rather than the loss or addition of heat at the surface. Our analysis suggests that, even in extratropical latitudes, initialization of ocean dynamical processes could be an important source of skill for interannual predictability of Hmld and Htot. Furthermore, we expect variations in Htot (and thus thermosteric sea level) to be more predictable than near surface temperature anomalies due to the increased importance of ocean heat transport processes for full-depth heat budgets.

  12. Heat- and mass-transport in aqueous silica nanofluids

    NASA Astrophysics Data System (ADS)

    Turanov, A. N.; Tolmachev, Yuriy V.

    2009-10-01

    Using the transient hot wire and pulsed field gradient nuclear magnetic resonance methods we determined the thermal conductivity and the solvent self-diffusion coefficient (SDC) in aqueous suspensions of quasi-monodisperse spherical silica nanoparticles. The thermal conductivity was found to increase at higher volume fraction of nanoparticles in accordance with the effective medium theory albeit with a smaller slope. On the other hand, the SDC was found to decrease with nanoparticle volume fraction faster than predicted by the effective medium theory. These deviations can be explained by the presence of an interfacial heat-transfer resistance and water retention by the nanoparticles, respectively. We found no evidence for anomalous enhancement in the transport properties of nanofluids reported earlier by other groups.

  13. Heat conduction in multifunctional nanotrusses studied using Boltzmann transport equation

    NASA Astrophysics Data System (ADS)

    Dou, Nicholas G.; Minnich, Austin J.

    2016-01-01

    Materials that possess low density, low thermal conductivity, and high stiffness are desirable for engineering applications, but most materials cannot realize these properties simultaneously due to the coupling between them. Nanotrusses, which consist of hollow nanoscale beams architected into a periodic truss structure, can potentially break these couplings due to their lattice architecture and nanoscale features. In this work, we study heat conduction in the exact nanotruss geometry by solving the frequency-dependent Boltzmann transport equation using a variance-reduced Monte Carlo algorithm. We show that their thermal conductivity can be described with only two parameters, solid fraction and wall thickness. Our simulations predict that nanotrusses can realize unique combinations of mechanical and thermal properties that are challenging to achieve in typical materials.

  14. Nuclear reactor heat transport system component low friction support system

    DOEpatents

    Wade, Elman E.

    1980-01-01

    A support column for a heavy component of a liquid metal fast breeder reactor heat transport system which will deflect when the pipes leading coolant to and from the heavy component expand or contract due to temperature changes includes a vertically disposed pipe, the pipe being connected to the heavy component by two longitudinally spaced cycloidal dovetail joints wherein the distal end of each of the dovetails constitutes a part of the surface of a large diameter cylinder and the centerlines of these large diameter cylinders intersect at right angles and the pipe being supported through two longitudinally spaced cycloidal dovetail joints wherein the distal end of each of the dovetails constitutes a part of the surface of a large diameter cylinder and the centerlines of these large diameter cylinders intersect at right angles, each of the cylindrical surfaces bearing on a flat and horizontal surface.

  15. Seasonal Cycle of Ocean Heat Transport and its Projected Changes

    NASA Astrophysics Data System (ADS)

    Yang, D.; Saenko, O.

    2011-12-01

    Seasonal cycle of ocean heat transport (OHT) and its projected changes are analyzed using the second-generation Canadian Earth System Model (CanESM2). The future anthropogenic forcing is assessed using two newly-developed representative concentration pathways (RCPs) of greenhouse gases and aerosols (RCP 4.5 and RCP 8.5). Consistent with some previous results based on eddy-permitting models, it is found that much of the seasonal variability of meridional circulation in the CanESM2 ocean is captured by the seasonal cycle of meridional Ekman fluxes, compensated by deep-reaching barotropic return flows. Since the seasonal cycle of zonal wind stress is projected to change at some latitudes, both in the Northern and Southern hemispheres, the projected seasonal variability of OHT essentially follows these changes in the wind.

  16. Heat conduction in multifunctional nanotrusses studied using Boltzmann transport equation

    SciTech Connect

    Dou, Nicholas G.; Minnich, Austin J.

    2016-01-04

    Materials that possess low density, low thermal conductivity, and high stiffness are desirable for engineering applications, but most materials cannot realize these properties simultaneously due to the coupling between them. Nanotrusses, which consist of hollow nanoscale beams architected into a periodic truss structure, can potentially break these couplings due to their lattice architecture and nanoscale features. In this work, we study heat conduction in the exact nanotruss geometry by solving the frequency-dependent Boltzmann transport equation using a variance-reduced Monte Carlo algorithm. We show that their thermal conductivity can be described with only two parameters, solid fraction and wall thickness. Our simulations predict that nanotrusses can realize unique combinations of mechanical and thermal properties that are challenging to achieve in typical materials.

  17. Energy Conversion Advanced Heat Transport Loop and Power Cycle

    SciTech Connect

    Oh, C. H.

    2006-08-01

    The Department of Energy and the Idaho National Laboratory are developing a Next Generation Nuclear Plant (NGNP) to serve as a demonstration of state-of-the-art nuclear technology. The purpose of the demonstration is two fold 1) efficient low cost energy generation and 2) hydrogen production. Although a next generation plant could be developed as a single-purpose facility, early designs are expected to be dual-purpose. While hydrogen production and advanced energy cycles are still in its early stages of development, research towards coupling a high temperature reactor, electrical generation and hydrogen production is under way. Many aspects of the NGNP must be researched and developed in order to make recommendations on the final design of the plant. Parameters such as working conditions, cycle components, working fluids, and power conversion unit configurations must be understood. Three configurations of the power conversion unit were demonstrated in this study. A three-shaft design with 3 turbines and 4 compressors, a combined cycle with a Brayton top cycle and a Rankine bottoming cycle, and a reheated cycle with 3 stages of reheat were investigated. An intermediate heat transport loop for transporting process heat to a High Temperature Steam Electrolysis (HTSE) hydrogen production plant was used. Helium, CO2, and an 80% nitrogen, 20% helium mixture (by weight) were studied to determine the best working fluid in terms cycle efficiency and development cost. In each of these configurations the relative component size were estimated for the different working fluids. The relative size of the turbomachinery was measured by comparing the power input/output of the component. For heat exchangers the volume was computed and compared. Parametric studies away from the baseline values of the three-shaft and combined cycles were performed to determine the effect of varying conditions in the cycle. This gives some insight into the sensitivity of these cycles to various

  18. Experimental Characterization of the Electron Heat Transport in Low-Density ASDEX Upgrade Plasmas

    SciTech Connect

    Ryter, F.; Imbeaux, F.; Leuterer, F.; Fahrbach, H.-U.; Suttrop, W.; ASDEX Upgrade Team

    2001-06-11

    The electron heat transport is investigated in ASDEX Upgrade conventional L -mode plasmas with pure electron heating provided by electron-cyclotron heating (ECH) at low density. Under these conditions, steady-state and ECH modulation experiments indicate without ambiguity that electron heat transport exhibits a clear threshold in {nabla}T{sub e}/T{sub e} and also suggest that it has a gyro-Bohm character.

  19. Heat and momentum transport scalings in vertical convection

    NASA Astrophysics Data System (ADS)

    Shishkina, Olga

    2016-11-01

    For vertical convection, where a fluid is confined between two differently heated isothermal vertical walls, we investigate the heat and momentum transport, which are measured, respectively, by the Nusselt number Nu and the Reynolds number Re . For laminar vertical convection we derive analytically the dependence of Re and Nu on the Rayleigh number Ra and the Prandtl number Pr from our boundary layer equations and find two different scaling regimes: Nu Pr 1 / 4 Ra 1 / 4 , Re Pr - 1 / 2 Ra 1 / 2 for Pr << 1 and Nu Pr0 Ra 1 / 4 , Re Pr-1 Ra 1 / 2 for Pr >> 1 . Direct numerical simulations for Ra from 105 to 1010 and Pr from 0.01 to 30 are in excellent ageement with our theoretical findings and show that the transition between the regimes takes place for Pr around 0.1. We summarize the results from and present new theoretical and numerical results for transitional and turbulent vertical convection. The work is supported by the Deutsche Forschungsgemeinschaft (DFG) under the Grant Sh 405/4 - Heisenberg fellowship.

  20. Experimental simulation of latent heat thermal energy storage and heat pipe thermal transport for dish concentrator solar receiver

    NASA Technical Reports Server (NTRS)

    Narayanan, R.; Zimmerman, W. F.; Poon, P. T. Y.

    1981-01-01

    Test results on a modular simulation of the thermal transport and heat storage characteristics of a heat pipe solar receiver (HPSR) with thermal energy storage (TES) are presented. The HPSR features a 15-25 kWe Stirling engine power conversion system at the focal point of a parabolic dish concentrator operating at 827 C. The system collects and retrieves solar heat with sodium pipes and stores the heat in NaF-MgF2 latent heat storage material. The trials were run with a single full scale heat pipe, three full scale TES containers, and an air-cooled heat extraction coil to replace the Stirling engine heat exchanger. Charging and discharging, constant temperature operation, mixed mode operation, thermal inertial, etc. were studied. The heat pipe performance was verified, as were the thermal energy storage and discharge rates and isothermal discharges.

  1. The nature of the sunspot phenomenon. I - Solutions of the heat transport equation

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1974-01-01

    It is pointed out that sunspots represent a disruption in the uniform flow of heat through the convective zone. The basic sunspot structure is, therefore, determined by the energy transport equation. The solutions of this equation for the case of stochastic heat transport are examined. It is concluded that a sunspot is basically a region of enhanced, rather than inhibited, energy transport and emissivity. The heat flow equations are discussed and attention is given to the shallow depth of the sunspot phenomenon. The sunspot is seen as a heat engine of high efficiency which converts most of the heat flux into hydromagnetic waves.

  2. Photothermal heating in metal-embedded microtools for material transport

    NASA Astrophysics Data System (ADS)

    Villangca, Mark; Palima, Darwin; Bañas, Andrew; Glückstad, Jesper

    2016-03-01

    Material transport is an important mechanism in microfluidics and drug delivery. The methods and solutions found in literature involve passively diffusing structures, microneedles and chemically fueled structures. In this work, we make use of optically actuated microtools with embedded metal layer as heating element for controlled loading and release. The new microtools take advantage of the photothermal-induced convection current to load and unload cargo. We also discuss some challenges encountered in realizing a self-contained polymerized microtool. Microfluidic mixing, fluid flow control and convection currents have been demonstrated both experimentally and numerically for static metal thin films or passively floating nanoparticles. Here we show an integration of aforementioned functionalities in an optically fabricated and actuated microtool. As proof of concept, we demonstrate loading and unloading of beads. This can be extended to controlled transport and release of genetic material, bio-molecules, fluorescent dyes. We envisioned these microtools to be an important addition to the portfolio of structure-mediated contemporary biophotonics.

  3. Aluminum heat exchanger

    SciTech Connect

    Koisuka, M.; Aoki, H.

    1986-11-04

    This patent describes a heat exchanger comprising a flat metal tube for conducting fluid having opposite first and second ends, of metal fins fixed onto outer surfaces of the flat metal tube, first and second header pipes fixedly mounted on the opposite ends of the flat metal tube, respectively, so that the flat metal tube communicates with the interior of the header pipes. Each of the header pipes has a first end that is open and a second end that is closed. An inlet tube is connected to the first end of the first header pipe, and an outlet tube is connected to the first end of the second header pipe. The improvement described here comprises one of the inlet and outlet tubes having an end portion inserted into the first end of the corresponding interconnected header pipe. The end portion has a cut-away portion in the form of a first axial slit extending axially inwardly from an open end at the adjacent end of the one tube. The first axial slit has an axial intermediate portion slightly smaller than the thickness of the flat metal tube, and a tapered portion diverging towards the open end of the first axial slit, and the first end of the flat metal tube extends into the corresponding interconnected header pipe and is closely fitted into the first axial slit.

  4. Tuning heat transport in trapped-ion chains across a structural phase transition

    NASA Astrophysics Data System (ADS)

    Ruiz, A.; Alonso, D.; Plenio, M. B.; del Campo, A.

    2014-06-01

    We analyze the heat transport in an ion chain that is confined in a strongly anisotropic Paul trap. To drive a heat current across the chain different pairs of counterpropagating laser beams are applied to the ions on the edges. The lasers behave as heat reservoirs operating at different temperatures, and a nonequilibrium heat flow can be sustained. The control of the spatial distribution of the ions in the chain by variation of the trapping frequencies makes ion chains an ideal testbed to study heat transport properties in finite open systems of low dimensionality with tunable nonlinearities. We explore heat transport across a structural phase transition between the linear and zigzag configurations, identifying the condition for optimal heat transport.

  5. The impact of oceanic heat transport on the mean meridional circulation

    NASA Astrophysics Data System (ADS)

    Knietzsch, Marc-Andre; Lucarini, Valerio; Lunkeit, Frank

    2014-05-01

    A general circulation model of intermediate complexity and an idealized earthlike aquaplanet setup are used to study the impact of oceanic heat transport on the mean meridional circulation. Oceanic heat transport is prescribed by a q-flux following Rose et al. (2012) with peak at 27°. Annual means of 30 years of investigation are used. The mean meridional circulation is studied by means of the zonal mean mass stream function. It shows that the mean circulation weakens with increasing oceanic heat transport especially the Hadley cell. The margin between the Hadley and the Ferrel cell is shifted poleward. Hence the Hadley cell expands with increasing oceanic heat transport. If the maximum magnitude of oceanic heat transport exceeds 3 PW, the whole tropical Hadley circulation shifts poleward and a weak inverse cell develops in the deep tropics. The diagnostic equation of the zonal mean mass stream function called Kuo-Eliassen equation is used to investigate the forcings of the mean meridional circulation. These are the meridional gradient of diabatic heating, the meridional gradient of eddy heat flux divergence and the vertical gradient of eddy momentum flux convergence. Frictional effects are ignored. Increasing oceanic heat transport affects the zonal mean diabatic heating distribution leading to a decreasing of its meridional gradient with increasing oceanic heat transport. With increasing oceanic heat transport the region of baroclinic unstable waves shifts poleward and both the eddy fluxes and their gradients decline. This leads to a weakening of the eddy flux driven Ferrel cell. Furthermore the poleward shifting of the eddy influenced region leads to Hadley cell's expansion and Ferrel cell's poleward shifting. The whole Hadley circulation is shifted poleward, if the oceanic heat transport leads to a poleward shifting of the diabatic heating maximum away from the equator.

  6. Phishtest: Measuring the Impact of Email Headers on the Predictive Accuracy of Machine Learning Techniques

    ERIC Educational Resources Information Center

    Tout, Hicham

    2013-01-01

    The majority of documented phishing attacks have been carried by email, yet few studies have measured the impact of email headers on the predictive accuracy of machine learning techniques in detecting email phishing attacks. Research has shown that the inclusion of a limited subset of email headers as features in training machine learning…

  7. Proso Millet Harvest: A Comparison of Conventional Harvest and Direct Harvest with a Stripper Header

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This research was conducted to determine if proso millet can be harvested with a stripper header. Stripper headers use extremely fast rotating metal teeth to rip the seed off the plant and leave the majority of residue standing in the field as opposed to cutting off the entire plant and running tha...

  8. DOS-HEATING6: A general conduction code with nuclear heat generation derived from DOT-IV transport calculations

    SciTech Connect

    Williams, M.L.; Yuecel, A.; Nadkarny, S.

    1988-05-01

    The HEATING6 heat conduction code is modified to (a) read the multigroup particle fluxes from a two-dimensional DOT-IV neutron- photon transport calculation, (b) interpolate the fluxes from the DOT-IV variable (optional) mesh to the HEATING6 control volume mesh, and (c) fold the interpolated fluxes with kerma factors to obtain a nuclear heating source for the heat conduction equation. The modified HEATING6 is placed as a module in the ORNL discrete ordinates system (DOS), and has been renamed DOS-HEATING6. DOS-HEATING6 provides the capability for determining temperature distributions due to nuclear heating in complex, multi-dimensional systems. All of the original capabilities of HEATING6 are retained for the nuclear heating calculation; e.g., generalized boundary conditions (convective, radiative, finned, fixed temperature or heat flux), temperature and space dependent thermal properties, steady-state or transient analysis, general geometry description, etc. The numerical techniques used in the code are reviewed and the user input instructions and JCL to perform DOS-HEATING6 calculations are presented. Finally a sample problem involving coupled DOT-IV and DOS-HEATING6 calculations of a complex space-reactor configurations described, and the input and output of the calculations are listed. 10 refs., 11 figs., 6 tabs.

  9. Shape optimized headers and methods of manufacture thereof

    SciTech Connect

    Perrin, Ian James

    2013-11-05

    Disclosed herein is a shape optimized header comprising a shell that is operative for collecting a fluid; wherein an internal diameter and/or a wall thickness of the shell vary with a change in pressure and/or a change in a fluid flow rate in the shell; and tubes; wherein the tubes are in communication with the shell and are operative to transfer fluid into the shell. Disclosed herein is a method comprising fixedly attaching tubes to a shell; wherein the shell is operative for collecting a fluid; wherein an internal diameter and/or a wall thickness of the shell vary with a change in pressure and/or a change in a fluid flow rate in the shell; and wherein the tubes are in communication with the shell and are operative to transfer fluid into the shell.

  10. Automatic computed tomography patient dose calculation using DICOM header metadata.

    PubMed

    Jahnen, A; Kohler, S; Hermen, J; Tack, D; Back, C

    2011-09-01

    The present work describes a method that calculates the patient dose values in computed tomography (CT) based on metadata contained in DICOM images in support of patient dose studies. The DICOM metadata is preprocessed to extract necessary calculation parameters. Vendor-specific DICOM header information is harmonized using vendor translation tables and unavailable DICOM tags can be completed with a graphical user interface. CT-Expo, an MS Excel application for calculating the radiation dose, is used to calculate the patient doses. All relevant data and calculation results are stored for further analysis in a relational database. Final results are compiled by utilizing data mining tools. This solution was successfully used for the 2009 CT dose study in Luxembourg. National diagnostic reference levels for standard examinations were calculated based on each of the countries' hospitals. The benefits using this new automatic system saved time as well as resources during the data acquisition and the evaluation when compared with earlier questionnaire-based surveys.

  11. Pyrolysis of epoxies used for thermal-battery headers

    SciTech Connect

    Guidotti, R.A.; Thornberg, S.M.; Campbell-Domme, B.

    1995-08-01

    Thermally activated batteries use an epoxy for encapsulation of the electrical feedthroughs in the header of the battery. When the thermal battery is thermally abused, the encapsulant can pyrolyze and generate large internal pressures. This causes the battery to vent in extreme cases. The nature of these gases has never been adequately documented. Therefore, a study was undertaken to address this deficiency. The pyrolysis of various encapsulants that have been used, or are being considered for use, in thermally activated batteries was studied over a temperature range of 155 to 455 C. The composition of the pyrolysis decomposition products was determined by gas chromatography/mass spectrometry (GS/MS). This determination is helpful in assessing the potential environmental and health effect for personnel exposed to such gases. In addition, the thermal stability of the various epoxies was measured by thermogravimetric analysis (TGA).

  12. Evaluating two process scale chromatography column header designs using CFD.

    PubMed

    Johnson, Chris; Natarajan, Venkatesh; Antoniou, Chris

    2014-01-01

    Chromatography is an indispensable unit operation in the downstream processing of biomolecules. Scaling of chromatographic operations typically involves a significant increase in the column diameter. At this scale, the flow distribution within a packed bed could be severely affected by the distributor design in process scale columns. Different vendors offer process scale columns with varying design features. The effect of these design features on the flow distribution in packed beds and the resultant effect on column efficiency and cleanability needs to be properly understood in order to prevent unpleasant surprises on scale-up. Computational Fluid Dynamics (CFD) provides a cost-effective means to explore the effect of various distributor designs on process scale performance. In this work, we present a CFD tool that was developed and validated against experimental dye traces and tracer injections. Subsequently, the tool was employed to compare and contrast two commercially available header designs.

  13. Determining the Cause of a Header Failure in a Natural Gas Production Facility

    SciTech Connect

    Matthes, S.A.; Covino, B.S., Jr.; Bullard, S.J.; Ziomek-Moroz, M.; Holcomb, G.R.

    2007-03-01

    An investigation was made into the premature failure of a gas-header at the Rocky Mountain Oilfield Testing Center (RMOTC) natural gas production facility. A wide variety of possible failure mechanisms were considered: design of the header, deviation from normal pipe alloy composition, physical orientation of the header, gas composition and flow rate, type of corrosion, protectiveness of the interior oxide film, time of wetness, and erosion-corrosion. The failed header was examined using metallographic techniques, scanning electron microscopy, and microanalysis. A comparison of the failure site and an analogous site that had not failed, but exhibited similar metal thinning was also performed. From these studies it was concluded that failure resulted from erosion-corrosion, and that design elements of the header and orientation with respect to gas flow contributed to the mass loss at the failure point.

  14. Enhanced heat transport in environmental systems using microencapsulated phase change materials

    NASA Technical Reports Server (NTRS)

    Colvin, D. P.; Mulligan, J. C.; Bryant, Y. G.

    1992-01-01

    A methodology for enhanced heat transport and storage that uses a new two-component fluid mixture consisting of a microencapsulated phase change material (microPCM) for enhanced latent heat transport is outlined. SBIR investigations for NASA, USAF, SDIO, and NSF since 1983 have demonstrated the ability of the two-component microPCM coolants to provide enhancements in heat transport up to 40 times over that of the carrier fluid alone, enhancements of 50 to 100 percent in the heat transfer coefficient, practically isothermal operation when the coolant flow is circulated in an optimal manner, and significant reductions in pump work.

  15. Compensation of Meridional Heat Transport: Testing the Bjerknes Hypothesis in a Freshening World

    NASA Astrophysics Data System (ADS)

    Wang, Y.

    2012-04-01

    The compensation between the meridional heat transports in the atmosphere and ocean is studied through a coupled model water hosing experiments. It is found that the Bjerknes compensation hypothesis is valid in the extratropics. In the tropics, the atmospheric heat transport (AHT) overcompensates the total oceanic heat transport, because of an enhanced wind-driven oceanic heat transport (OHT) in the Pacific-Indian Oceans. The water hosing in the high latitude Atlantic weakens the Atlantic meridional overturning circulation and thus the northward Atlantic OHT significantly. This leads to an enhanced interhemispheric SST gradient across the global tropics and in turn an enhanced (weakened) atmosphere Hadley Cell in the Northern (Southern) Hemisphere. The enhanced Hadley Cell itself increases the northward AHT, compensating the reduced Atlantic OHT. Meanwhile, it increases the surface trade wind and in turn the wind-driven northward OHT in the Pacific-Indian Oceans, leading to an overcompensation of the northward heat transport.

  16. Interface Exchange as an Indicator for Eddy Heat Transport

    SciTech Connect

    Petersen, Mark R.; Williams, Sean J.; Hecht, Matthew W.; Maltrud, Mathew E.; Hamann, Bernd; Patchett, John M.; Ahrens, James P.

    2012-06-12

    The ocean contains many large-scale, long-lived vortices, called mesoscale eddies, that are believed to have a role in the transport and redistribution of salt, heat, and nutrients throughout the ocean. Determining this role, however, has proven to be a challenge, since the mechanics of eddies are only partly understood; a standard definition for these ocean eddies does not exist and, therefore, scientifically meaningful, robust methods for eddy extraction, characterization, tracking and visualization remain a challenge. In order to shed light on the nature and potential roles of eddies, we have combined our previous research on eddy identification and tracking, and have used those approaches as the basis for analysis-driven computational experiments on the nature of eddies. Based on the resulting visualizations of eddy behavior, we have devised a new metric to characterize the transfer of water into and out of eddies across their boundary, and have developed visualization methods for this new metric to provide clues about the role eddies play in the global ocean and, potentially, climate change.

  17. Variability in North Atlantic heat content and heat transport in a coupled ocean-atmosphere GCM

    NASA Astrophysics Data System (ADS)

    Dong, B.; Sutton, R. T.

    2002-06-01

    A coupled ocean-atmosphere general circulation model has been used to study the variations of North Atlantic upper ocean heat content (OHC), sea surface temperature (SST) and ocean heat transport (OHT), and the relationships between these three quantities. We find that OHC anomalies, and salinity anomalies, propagate anti-cyclonically around the North Atlantic subtropical gyre. They propagate eastward in midlatitudes and westward in low latitudes. Both the advection of mean temperature by anomalous currents and the advection of temperature anomalies by mean currents are responsible for these zonal propagations. In addition to zonal propagations, upper ocean temperature anomalies propagate southward in the eastern North Atlantic, where subduction plays a dominant role. Variability in the northward OHT in the Atlantic is primarily governed by variability in the ocean circulation rather than variability in temperatures. Fluctuations in OHT are the major cause of anomalies in OHC and SST in the Gulf Stream extension region. This is true both for interannual variability and for decadal variability. On interannual time scales, however, surface fluxes also make a significant contribution. Analysis of the relationships of OHT with OHC and SST suggests that a knowledge of OHT fluctuations could be used to predict variations in OHC, and therefore sea surface temperatures, several years in advance.

  18. Numerical modeling for energy transport and isochoric heating in ultra-fast heated high Z target

    NASA Astrophysics Data System (ADS)

    Mishra, Rohini; Sentoku, Yasuhiko; Hakel, Peter; Mancini, Roberto C.

    2010-11-01

    Collisional Particle-in-Cell (PIC) code is an effective tool to study extreme energy density conditions achieved in intense laser-solid interactions. In the continuous process of developing PIC code, we have recently implemented models to incorporate dynamic ionizations, namely Saha and Thomas Fermi, and radiation cooling (due to Bremsstrahlung and line emissions). We have also revised the existing collision model to take into account bounded electrons in dynamically ionizing target (partially ionized target). One-dimensional PIC simulation of a gold target with new collision model shows strong local heating in a micron distance due to shorter stopping range of fast electrons, which reflects the increased collision frequency due to bound electrons. The peak temperature in the heated region drops significantly due to the radiation cooling to a level of a few hundred eV from keV. We also discuss the target Z dependence on radiation loss and two-dimensional effects such as the resistive magnetic fields in the hot electron transport in metal targets.

  19. Spin-dependent heat transport and thermal boundary resistance

    NASA Astrophysics Data System (ADS)

    Jeong, Taehee

    In this thesis, thermal conductivity change depending on the magnetic configurations has been studied. In order to make different magnetic configurations, we developed a spin valve structure, which has high MR ratio and low saturation field. The high MR ratio was achieved using Co/Cu multilayer and 21A or 34A thick Cu layer. The low saturation field was obtained by implementing different coercivities of the successive ferromagnetic layers. For this purpose, Co/Cu/Cu tri-layered structure was used with the thicknesses of the Co layers; 15 A and 30 A. For the thermal conductivity measurement, a three-omega method was employed with a thermally isolated microscale rod. We fabricated the microscale rod using optical lithography and MEMS process. Then the rod was wire-bonded to a chip-carver for further electrical measurement. For the thermal conductivity measurement, we built the three-omega measurement system using two lock-in amplifiers and two differential amplifiers. A custom-made electromagnet was added to the system to investigate the impact of magnetic field. We observed titanic thermal conductivity change depending on the magnetic configurations of the Co/Cu/Co multilayer. The thermal conductivity change was closely correlated with that of the electric conductivity in terms of the spin orientation, but the thermal conductivity was much more sensitive than that of the electric conductivity. The relative thermal conductivity change was 50% meanwhile that of electric resistivity change was 8.0%. The difference between the two ratios suggests that the scattering mechanism for charge and heat transport in the Co/Cu/Co multilayer is different. The Lorentz number in Weidemann-Franz law is also spin-dependent. Thermal boundary resistance between metal and dielectrics was also studied in this thesis. The thermal boundary resistance becomes critical for heat transport in a nanoscale because the thermal boundary resistance can potentially determine overall heat transport

  20. Diabatic heating, divergent circulation and moisture transport in the African monsoon system

    SciTech Connect

    Hagos, Samson M.; Zhang, Chidong

    2009-12-24

    The dynamics of the West African monsoon system is studied through the diagnosis of the roles of diabatic heating in the divergent circulation and moisture transport. The divergent circulation is partitioned into latent-heating and non-latent-heating (the sum of surface sensible heat flux and radiative heating) driven components based on its field properties and its relationship with diabatic heating profiles. Roles of latent and non-latent diabatic heating in the moisture transport of the monsoon system are thus distinguished. The gradient in surface sensible heat flux between the Saharan heat-low and the Gulf of Guinea drives a shallow meridional circulation, which transports moisture far into the continent on the northern side of the monsoon rain band and thereby promotes the seasonal northward migration of monsoon precipitation. In contrast, the circulation directly associated with latent heating is deep and the corresponding moisture convergence maximum is within the region of precipitation and thus enhances local monsoon precipitation. Meanwhile, latent heating also induces dry air advection from the north. The seasonal northward migration of precipitation is encouraged by neither of the two effects. On the other hand, the divergent circulation forced by remote latent heating influences local moisture distribution through advection. Specifically by bringing Saharan air from the north, and driving moisture to the adjacent oceans, global latent heating has an overall drying effect over the Sahel.

  1. Impact of model resolution for on-shelf heat transport along the West Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Graham, Jennifer A.; Dinniman, Michael S.; Klinck, John M.

    2016-10-01

    The flux of warm deep water onto Antarctic continental shelves plays a vital role in determining water mass properties adjacent to the continent. A regional model, with two different grid resolutions, has been used to simulate ocean processes along the West Antarctic Peninsula. At both 4 km and 1.5 km resolution, the model reproduces the locations of warm intrusions, as shown through comparison with observations from instrumented seals. However, the 1.5 km simulation shows greater on-shelf heat transport, leading to improved representation of heat content on the shelf. This increased heat transport is associated with increased eddy activity, both at the shelf-break and in the deep ocean off-shore. Cross-shelf troughs are key locations of on-shelf heat transport. Comparison of two troughs, Belgica and Marguerite, shows differing responses to increased resolution. At higher resolution, there is an increased on-shelf volume transport at Belgica Trough, but not at Marguerite Trough. This is likely related to the differing structure of the shelf-break jet between these two locations. The increased heat flux at Marguerite Trough is attributed to increased heat content in the on-shelf transport. Increased eddy activity off-shelf may lead to greater cross-front heat transport, and therefore increased heat available above the continental slope. While these simulations differ in their magnitude of heat transport, both show similar patterns of variability. Variations in wind stress lead to variations in speed of the shelf-break jet, and therefore on-shelf heat transport. These results demonstrate the importance of model resolution for understanding cross-shelf transport around Antarctica.

  2. Heat transport in metals irradiated by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Kanavin, A. P.; Smetanin, I. V.; Isakov, V. A.; Afanasiev, Yu. V.; Chichkov, B. N.; Wellegehausen, B.; Nolte, S.; Momma, C.; Tünnermann, A.

    1998-06-01

    Different regimes of heat propagation in metals irradiated by subpicosecond laser pulses are studied on the basis of a two-temperature diffusion model. Analytical solutions for the heat conduction equation, corresponding to the different temperature dependences of the electron thermal conductivity, are obtained. It is shown that in case of a strong electron-lattice nonequilibrium, the heat penetration depth grows linearly with time, and the heat propagation velocity decreases with increasing laser fluence. Investigations of this ``counterintuitive'' regime of heat propagation are performed.

  3. Why ocean heat transport warms the global mean climate

    NASA Astrophysics Data System (ADS)

    Herweijer, Celine; Seager, Richard; Winton, Michael; Clement, Amy

    2005-08-01

    Observational and modelling evidence suggest that poleward ocean heat transport (OHT) can vary in response to both natural climate variability and greenhouse warming. Recent modelling studies have shown that increased OHT warms both the tropical and global mean climates. Using two different coupled climate models with mixed-layer oceans, with and without OHT, along with a coupled model with a fixed-current ocean component in which the currents are uniformly reduced and increased by 50%, an attempt is made to explain why this may happen.OHT warms the global mean climate by 1 to 1.6K in the atmospheric general circulation (AGCM) ML model and 3.5K in the AGCM fixed current model. In each model the warming is attributed to an increase in atmospheric greenhouse trapping, primarily clear-sky greenhouse trapping, and a reduction in albedo. This occurs as OHT moistens the atmosphere, particularly at subtropical latitudes. This is not purely a thermodynamic response to the reduction in planetary albedo at these latitudes. It is a change in atmospheric circulation that both redistributes the water vapour and allows for a global atmospheric moistening—a positive 'dynamical' water vapour feedback. With increasing OHT the atmospheric water vapour content increases as atmospheric convection spreads out of the deep tropics. The global mean planetary albedo is decreased with increased OHT. This change is explained by a decrease in subtropical and mid-latitude low cloudiness, along with a reduction in high-latitude surface albedo due to decreased sea ice. The climate models with the mixed layer oceans underestimate both the subtropical low cloud cover and the high-latitude sea ice/surface albedo, and consequently have a smaller warming response to OHT.

  4. Anomalous heat transport and condensation in convection of cryogenic helium.

    PubMed

    Urban, Pavel; Schmoranzer, David; Hanzelka, Pavel; Sreenivasan, Katepalli R; Skrbek, Ladislav

    2013-05-14

    When a hot body A is thermally connected to a cold body B, the textbook knowledge is that heat flows from A to B. Here, we describe the opposite case in which heat flows from a colder but constantly heated body B to a hotter but constantly cooled body A through a two-phase liquid-vapor system. Specifically, we provide experimental evidence that heat flows through liquid and vapor phases of cryogenic helium from the constantly heated, but cooler, bottom plate of a Rayleigh-Bénard convection cell to its hotter, but constantly cooled, top plate. The bottom plate is heated uniformly, and the top plate is cooled by heat exchange with liquid helium maintained at 4.2 K. Additionally, for certain experimental conditions, a rain of helium droplets is detected by small sensors placed in the cell at about one-half of its height.

  5. Global anomalous transport of ICRH- and NBI-heated fast ions

    NASA Astrophysics Data System (ADS)

    Wilkie, G. J.; Pusztai, I.; Abel, I.; Dorland, W.; Fülöp, T.

    2017-04-01

    By taking advantage of the trace approximation, one can gain an enormous computational advantage when solving for the global turbulent transport of impurities. In particular, this makes feasible the study of non-Maxwellian transport coupled in radius and energy, allowing collisions and transport to be accounted for on similar time scales, as occurs for fast ions. In this work, we study the fully-nonlinear ITG-driven trace turbulent transport of locally heated and injected fast ions. Previous results indicated the existence of MeV-range minorities heated by cyclotron resonance, and an associated density pinch effect. Here, we build upon this result using the t3core code to solve for the distribution of these minorities, consistently including the effects of collisions, gyrokinetic turbulence, and heating. Using the same tool to study the transport of injected fast ions, we contrast the qualitative features of their transport with that of the heated minorities. Our results indicate that heated minorities are more strongly affected by microturbulence than injected fast ions. The physical interpretation of this difference provides a possible explanation for the observed synergy when neutral beam injection (NBI) heating is combined with ion cyclotron resonance heating (ICRH). Furthermore, we move beyond the trace approximation to develop a model which allows one to easily account for the reduction of anomalous transport due to the presence of fast ions in electrostatic turbulence.

  6. A computational approach to calculate the heat of transport of aqueous solutions

    NASA Astrophysics Data System (ADS)

    di Lecce, Silvia; Albrecht, Tim; Bresme, Fernando

    2017-03-01

    Thermal gradients induce concentration gradients in alkali halide solutions, and the salt migrates towards hot or cold regions depending on the average temperature of the solution. This effect has been interpreted using the heat of transport, which provides a route to rationalize thermophoretic phenomena. Early theories provide estimates of the heat of transport at infinite dilution. These values are used to interpret thermodiffusion (Soret) and thermoelectric (Seebeck) effects. However, accessing heats of transport of individual ions at finite concentration remains an outstanding question both theoretically and experimentally. Here we discuss a computational approach to calculate heats of transport of aqueous solutions at finite concentrations, and apply our method to study lithium chloride solutions at concentrations >0.5 M. The heats of transport are significantly different for Li+ and Cl‑ ions, unlike what is expected at infinite dilution. We find theoretical evidence for the existence of minima in the Soret coefficient of LiCl, where the magnitude of the heat of transport is maximized. The Seebeck coefficient obtained from the ionic heats of transport varies significantly with temperature and concentration. We identify thermodynamic conditions leading to a maximization of the thermoelectric response of aqueous solutions.

  7. A computational approach to calculate the heat of transport of aqueous solutions

    PubMed Central

    Di Lecce, Silvia; Albrecht, Tim; Bresme, Fernando

    2017-01-01

    Thermal gradients induce concentration gradients in alkali halide solutions, and the salt migrates towards hot or cold regions depending on the average temperature of the solution. This effect has been interpreted using the heat of transport, which provides a route to rationalize thermophoretic phenomena. Early theories provide estimates of the heat of transport at infinite dilution. These values are used to interpret thermodiffusion (Soret) and thermoelectric (Seebeck) effects. However, accessing heats of transport of individual ions at finite concentration remains an outstanding question both theoretically and experimentally. Here we discuss a computational approach to calculate heats of transport of aqueous solutions at finite concentrations, and apply our method to study lithium chloride solutions at concentrations >0.5 M. The heats of transport are significantly different for Li+ and Cl− ions, unlike what is expected at infinite dilution. We find theoretical evidence for the existence of minima in the Soret coefficient of LiCl, where the magnitude of the heat of transport is maximized. The Seebeck coefficient obtained from the ionic heats of transport varies significantly with temperature and concentration. We identify thermodynamic conditions leading to a maximization of the thermoelectric response of aqueous solutions. PMID:28322266

  8. Simulating water, solute, and heat transport in the subsurface with the VS2DI software package

    USGS Publications Warehouse

    Healy, R.W.

    2008-01-01

    The software package VS2DI was developed by the U.S. Geological Survey for simulating water, solute, and heat transport in variably saturated porous media. The package consists of a graphical preprocessor to facilitate construction of a simulation, a postprocessor for visualizing simulation results, and two numerical models that solve for flow and solute transport (VS2DT) and flow and heat transport (VS2DH). The finite-difference method is used to solve the Richards equation for flow and the advection-dispersion equation for solute or heat transport. This study presents a brief description of the VS2DI package, an overview of the various types of problems that have been addressed with the package, and an analysis of the advantages and limitations of the package. A review of other models and modeling approaches for studying water, solute, and heat transport also is provided. ?? Soil Science Society of America. All rights reserved.

  9. All-optical packet header and payload separation for un-slotted optical packet switched networks

    NASA Astrophysics Data System (ADS)

    Ji, Wei; Zhang, Min; Ye, Peida

    2005-11-01

    A novel all-optical header and payload separation technique that can be utilized in un-slotted optical packet switched networks is presented. The technique uses a modified TOAD for packet header extraction with differential modulation scheme and two SOAs that perform a simple XOR operation between the packet and its self-derived header to get the separated payload. The main virtue of this system is simple structure and need not any additional continuous pulses. Through numerical simulations, the operating characteristics of the scheme are illustrated. In addition, the parameters of the system are discussed and designed to optimize the operation performance.

  10. Device for passive downward heat transport - Design criteria and operational results

    NASA Astrophysics Data System (ADS)

    de Beni, G.; Friesen, R.; Thoma, H.; Veneroni, R.

    A semi-continuous device for passive downward heat transport has been designed, built and operated. Heat is transported as latent heat of vaporization as in a heat pipe; the return of the liquid is obtained through the action of an energy accumulator containing an inert gas and charged by the vapour itself during the transport of heat. The capability of winning the difference in level is exchanged with a difference of a few degrees centigrade between evaporator and condenser. The laboratory device worked with a difference in level of 1.7 m. Working under pressure, differences in level of 10 meters and more can be attained. A typical application can be the storage of heat available from solar collectors.

  11. Comparison of local and regional heat transport processes into the subsurface urban heat island of Karlsruhe, Germany

    NASA Astrophysics Data System (ADS)

    Benz, Susanne; Bayer, Peter; Menberg, Kathrin; Blum, Philipp

    2014-05-01

    Temperatures in shallow urban ground are typically elevated. They manifest as subsurface urban heat islands, which are observed worldwide in different metropolitan areas and which have a site-specific areal extent and intensity. As of right now the governing heat transport processes accumulating heat in the subsurface of cities are insufficiently understood. Based on a spatial assessment of groundwater temperatures, six individual heat flux processes could be identified: (1) heat flux from elevated ground surface temperatures (GST), (2) heat flux from basements of buildings, (3) reinjection of thermal waste water, (4) sewage drains, (5) sewage leakage, and (6) district heating. In this study, the contributions of these processes are quantified on local and regional scales for the city of Karlsruhe in Germany. For the regional scale, the Regionalized Monte Carlo (RMC) method is used. This method applies a single Monte Carlo (MC) simulation for the entire study area. At relatively low data demand, the RMC method provides basic insights into the heat contribution for the entire city. For the local scale, the Local Monte Carlo (LMC) method was developed and applied. This method analyzes all dominant heat fluxes spatially dependent by performing an MC simulation for each arbitrary sized pixel of the study area (here 10 x 10 m). This more intricate approach allows for a spatial representation of all heat flux processes, which is necessary for the local planning of geothermal energy use. In order to evaluate the heat transport processes on a regional scale, we compared the mean annual thermal energies that result from the individual heat flux processes. Both methods identify the heat flux from elevated GST and the heat flux from buildings as the dominant regional processes. However, reinjection of thermal wastewater is by far the most dominant local heat flux processes with an average heat flux of 16 ± 2 W/m2 in the affected areas. Although being dominant on the regional

  12. Modulated heat pulse propagation and partial transport barriers in chaotic magnetic fields

    DOE PAGES

    del-Castillo-Negrete, Diego; Blazevski, Daniel

    2016-04-01

    Direct numerical simulations of the time dependent parallel heat transport equation modeling heat pulses driven by power modulation in 3-dimensional chaotic magnetic fields are presented. The numerical method is based on the Fourier formulation of a Lagrangian-Green's function method that provides an accurate and efficient technique for the solution of the parallel heat transport equation in the presence of harmonic power modulation. The numerical results presented provide conclusive evidence that even in the absence of magnetic flux surfaces, chaotic magnetic field configurations with intermediate levels of stochasticity exhibit transport barriers to modulated heat pulse propagation. In particular, high-order islands and remnants of destroyed flux surfaces (Cantori) act as partial barriers that slow down or even stop the propagation of heat waves at places where the magnetic field connection length exhibits a strong gradient. The key parameter ismore » $$\\gamma=\\sqrt{\\omega/2 \\chi_\\parallel}$$ that determines the length scale, $$1/\\gamma$$, of the heat wave penetration along the magnetic field line. For large perturbation frequencies, $$\\omega \\gg 1$$, or small parallel thermal conductivities, $$\\chi_\\parallel \\ll 1$$, parallel heat transport is strongly damped and the magnetic field partial barriers act as robust barriers where the heat wave amplitude vanishes and its phase speed slows down to a halt. On the other hand, in the limit of small $$\\gamma$$, parallel heat transport is largely unimpeded, global transport is observed and the radial amplitude and phase speed of the heat wave remain finite. Results on modulated heat pulse propagation in fully stochastic fields and across magnetic islands are also presented. In qualitative agreement with recent experiments in LHD and DIII-D, it is shown that the elliptic (O) and hyperbolic (X) points of magnetic islands have a direct impact on the spatio-temporal dependence of the amplitude and the time delay

  13. Modulated heat pulse propagation and partial transport barriers in chaotic magnetic fields

    SciTech Connect

    del-Castillo-Negrete, Diego; Blazevski, Daniel

    2016-04-01

    Direct numerical simulations of the time dependent parallel heat transport equation modeling heat pulses driven by power modulation in 3-dimensional chaotic magnetic fields are presented. The numerical method is based on the Fourier formulation of a Lagrangian-Green's function method that provides an accurate and efficient technique for the solution of the parallel heat transport equation in the presence of harmonic power modulation. The numerical results presented provide conclusive evidence that even in the absence of magnetic flux surfaces, chaotic magnetic field configurations with intermediate levels of stochasticity exhibit transport barriers to modulated heat pulse propagation. In particular, high-order islands and remnants of destroyed flux surfaces (Cantori) act as partial barriers that slow down or even stop the propagation of heat waves at places where the magnetic field connection length exhibits a strong gradient. The key parameter is $\\gamma=\\sqrt{\\omega/2 \\chi_\\parallel}$ that determines the length scale, $1/\\gamma$, of the heat wave penetration along the magnetic field line. For large perturbation frequencies, $\\omega \\gg 1$, or small parallel thermal conductivities, $\\chi_\\parallel \\ll 1$, parallel heat transport is strongly damped and the magnetic field partial barriers act as robust barriers where the heat wave amplitude vanishes and its phase speed slows down to a halt. On the other hand, in the limit of small $\\gamma$, parallel heat transport is largely unimpeded, global transport is observed and the radial amplitude and phase speed of the heat wave remain finite. Results on modulated heat pulse propagation in fully stochastic fields and across magnetic islands are also presented. In qualitative agreement with recent experiments in LHD and DIII-D, it is shown that the elliptic (O) and hyperbolic (X) points of magnetic islands have a direct impact on the spatio-temporal dependence of the amplitude and the time delay of modulated heat

  14. A tunnel wick 100,000 watt-inch heat pipe.

    NASA Technical Reports Server (NTRS)

    Kosson, R.; Hembach, R.; Edelstein, F.; Tawil, M.

    1972-01-01

    The tunnel wick is a new type of heat pipe artery which can prime in a gravity environment by temperature-induced pressure differences between interior and exterior. The paper discusses the concept and its application in the design of room-temperature high-transport-capacity heat pipes. The analytical model of the system is summarized; and performance data obtained with the aid of a related computer program is included. Test data verifying the concept is presented for several pipes, including an eight-foot-long, 0.9-inch ID heat pipe, using ammonia working fluid, with a transport capacity in excess of 150,000 watt-inches. A brief discussion of potential applications for this type of heat pipe includes a variable conductance device to serve as a radiator header and a high capacity heat transport system.

  15. ANALYZING NUMERICAL ERRORS IN DOMAIN HEAT TRANSPORT MODELS USING THE CVBEM.

    USGS Publications Warehouse

    Hromadka, T.V.

    1987-01-01

    Besides providing an exact solution for steady-state heat conduction processes (Laplace-Poisson equations), the CVBEM (complex variable boundary element method) can be used for the numerical error analysis of domain model solutions. For problems where soil-water phase change latent heat effects dominate the thermal regime, heat transport can be approximately modeled as a time-stepped steady-state condition in the thawed and frozen regions, respectively. The CVBEM provides an exact solution of the two-dimensional steady-state heat transport problem, and also provides the error in matching the prescribed boundary conditions by the development of a modeling error distribution or an approximate boundary generation.

  16. Heat transport in metals irradiated by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Kanavin, Andrei P.; Afanasiev, Yuri V.; Chichkov, Boris N.; Isakov, Vladimir A.; Smetanin, Igor V.

    2000-02-01

    Different regimes of heat propagation in metals irradiated by subpicosecond laser pulses are studied on the basis of two-temperature diffusion model. New analytical solutions for the heat conduction equation, corresponding to the different temperature dependences of the electron thermal conductivity (formula available n paper), are found. It is shown that in case of a strong electron-lattice nonequilibrium, the heat penetration depth grows linearly with time, lT varies direct as t, in opposite to the ordinary diffusionlike behavior, lT varies direct as t1/2. Moreover, the heat propagation velocity decreases with increasing laser fluence.

  17. The roles of surface heat flux and ocean heat transport convergence in determining Atlantic Ocean temperature variability

    NASA Astrophysics Data System (ADS)

    Grist, Jeremy P.; Josey, Simon A.; Marsh, Robert; Good, Simon A.; Coward, Andrew. C.; de Cuevas, Beverly A.; Alderson, Steven G.; New, Adrian L.; Madec, Gurvan

    2010-08-01

    The temperature variability of the Atlantic Ocean is investigated using an eddy-permitting (1/4°) global ocean model (ORCA-025) forced with historical surface meteorological fields from 1958 to 2001. The simulation of volume-averaged temperature and the vertical structure of the zonally averaged temperature trends are compared with those from observations. In regions with a high number of observations, in particular above a depth of 500 m and between 22° N and 65° N, the model simulation and the dataset are in good agreement. The relative contribution of variability in ocean heat transport (OHT) convergence and net surface heat flux to changes in ocean heat content is investigated with a focus on three regions: the subpolar and subtropical gyres and the tropics. The surface heat flux plays a relatively minor role in year-to-year changes in the subpolar and subtropical regions, but in the tropical North Atlantic, its role is of similar significance to the ocean heat transport convergence. The strongest signal during the study period is a cooling of the subpolar gyre between 1970 and 1990, which subsequently reversed as the mid-latitude OHT convergence transitioned from an anomalously weak to an anomalously strong state. We also explore whether model OHT anomalies can be linked to surface flux anomalies through a Hovmöller analysis of the Atlantic sector. At low latitudes, increased ocean heat gain coincides with anomalously strong northward transport, whereas at mid-high latitudes, reduced ocean heat loss is associated with anomalously weak heat transport.

  18. Investigation of ion and electron heat transport of high-Te ECH heated discharges in the large helical device

    DOE PAGES

    Pablant, N. A.; Satake, S.; Yokoyama, M.; ...

    2016-01-28

    An analysis of the radial electric field and heat transport, both for ions and electrons, is presented for a high-more » $${{T}_{\\text{e}}}$$ electron cyclotron heated (ECH) discharge on the large helical device (LHD). Transport analysis is done using the task3d transport suite utilizing experimentally measured profiles for both ions and electrons. Ion temperature and perpendicular flow profiles are measured using the recently installed x-ray imaging crystal spectrometer diagnostic (XICS), while electron temperature and density profiles are measured using Thomson scattering. The analysis also includes calculated ECH power deposition profiles as determined through the travis ray-tracing code. This is the first time on LHD that this type of integrated transport analysis with measured ion temperature profiles has been performed without NBI, allowing the heat transport properties of plasmas with only ECH heating to be more clearly examined. For this study, a plasma discharge is chosen which develops a high central electron temperature ($${{T}_{\\text{eo}}}=9$$ keV) at moderately low densities ($${{n}_{\\text{eo}}}=1.5\\times {{10}^{19}}$$ m-3). The experimentally determined transport properties from task3d are compared to neoclassical predictions as calculated by the gsrake and fortec-3d codes. The predicted electron fluxes are seen to be an order of magnitude less than the measured fluxes, indicating that electron transport is largely anomalous, while the neoclassical and measured ion heat fluxes are of the same magnitude. Neoclassical predictions of a strong positive ambipolar electric field ($${{E}_{\\text{r}}}$$ ) in the plasma core are validated through comparisons to perpendicular flow measurements from the XICS diagnostic. Furthermore, this provides confidence that the predictions are producing physically meaningful results for the particle fluxes and radial electric field, which are a key component in correctly predicting plasma confinement.« less

  19. A non-equilibrium model for soil heating and moisture transport during extreme surface heating

    NASA Astrophysics Data System (ADS)

    Massman, W. J.

    2015-03-01

    With increasing use of prescribed fire by land managers and increasing likelihood of wildfires due to climate change comes the need to improve modeling capability of extreme heating of soils during fires. This issue is addressed here by developing a one-dimensional non-equilibrium model of soil evaporation and transport of heat, soil moisture, and water vapor, for use with surface forcing ranging from daily solar cycles to extreme conditions encountered during fires. The model employs a linearized Crank-Nicolson scheme for the conservation equations of energy and mass and its performance is evaluated against dynamic soil temperature and moisture observations obtained during laboratory experiments on soil samples exposed to surface heat fluxes ranging between 10 000 and 50 000 W m-2. The Hertz-Knudsen equation is the basis for constructing the model's non-equilibrium evaporative source term. The model includes a dynamic residual soil moisture as a function of temperature and soil water potential, which allows the model to capture some of the dynamic aspects of the strongly bound soil moisture that seems to require temperatures well beyond 150 °C to fully evaporate. Furthermore, the model emulates the observed increase in soil moisture ahead of the drying front and the hiatus in the soil temperature rise during the strongly evaporative stage of drying. It also captures the observed rapid evaporation of soil moisture that occurs at relatively low temperatures (50-90 °C). Sensitivity analyses indicate that the model's success results primarily from the use of a temperature and moisture potential dependent condensation coefficient in the evaporative source term. The model's solution for water vapor density (and vapor pressure), which can exceed one standard atmosphere, cannot be experimentally verified, but they are supported by results from (earlier and very different) models developed for somewhat different purposes and for different porous media. Overall, this non

  20. Is the Standard Definition of Poleward Heat Transport Appropriate in Climate Research?

    NASA Astrophysics Data System (ADS)

    Liang, Minyi; Czaja, Arnaud; Graversen, Rune; Tailleux, Remi

    2016-04-01

    In this paper, a problem with the standard definition of poleward heat transport is highlighted. This, we argue, arises because of the dependence of the standard definition on an arbitrary reference state for moist static energy. This dependence may result in large uncertainty in the estimates of ocean-atmosphere coupling, the signature in heat transport of the atmospheric storm track and annular modes of variability. A new definition is proposed to address the problem, which removes unrealistically large fluctuations (4PW) found when using the standard definition. A practical way to implement the new formulation is also discussed. The new heat transport definition is shown to lead to better correlations with climate indices compared to the traditional definition. In particular a clear relationship between the AO, El Niño and heat transport emerges in our analysis. In addition, it also produces different time sequence of event with large/weak poleward heat transport. It is hoped that the new heat transport definition may shed light on studies exploring the link between energy transport and climate variability.

  1. Effects of toroidal rotation on electron heat transport via changes in inertial force and impurity density

    NASA Astrophysics Data System (ADS)

    Narita, E.; Honda, M.; Yoshida, M.; Hayashi, N.; Urano, H.; Ide, S.

    2017-04-01

    Two types of JT-60U discharges are studied with an emphasis on toroidal rotation: in one discharge, which is characterized by the existence of an internal transport barrier (ITB), electron heat transport in the core region is affected by the toroidal rotation direction, while in the other discharge, which is a conventional H-mode plasma without an ITB, the clear correlation between the toroidal rotation direction and electron heat transport is not observed. In both discharges, the impurity density is also found to vary together with the rotation velocity profile. With a flux-tube gyrokinetic code, we have found that the effects of the changes in the rotation velocity profile and the impurity density on electron heat transport are different between these discharges. Including the effects explains the tendency observed in the experiments. First, regarding the rotation velocity profile, which influences heat transport through the inertial force, the dependence of heat transport on the rotation direction changes, according to the gradient of the rotation velocity. Next, an increase in the impurity density stabilizes the ion temperature gradient mode, but can destabilize the trapped electron mode. Therefore, it is found that the difference in the impact of the impurity density on electron heat transport in these discharges can be attributed to the difference in the dominant instability.

  2. Changes in Tropical Precipitation at the Mid-Holocene: Role of the Oceanic Heat Transport

    NASA Astrophysics Data System (ADS)

    Liu, X.; Battisti, D. S.; Donohoe, A.

    2015-12-01

    There is ample geological and geochemical evidence that precipitation in the tropics is largely different from today at the mid-Holocene, an era roughly 6,000 years ago when the Northern Hemisphere summer (winter) insolation was stronger (weaker) than today. These insolation differences are caused mainly by the precession of the earth's rotational axis, or called "precessional forcing". Using the mid-Holocene experiments of PMIP3, we studied changes in the zonal mean tropical precipitation, and its associated change in cross-equatorial energy transport. A northward movement of the zonal mean precipitation in the mid-Holocene is seen in 10 out of 13 PMIP3 models, with a correspondingly anomalous southward atmospheric heat transport across the equator. The slope is 3.0º per PW, close to the estimate given by Donohoe et al. (2013). The changes in cross-equatorial atmospheric heat transport are dictated by changes in the hemispheric asymmetry of heating from the surface, which in turn are associated with changes in the cross-equatorial oceanic heat transport: an anomalous northward oceanic heat transport at the equator is seen in all of the PMIP3 models. Analysis on this anomalous oceanic heat transport reveals that changes in the wind-driven gyre in the Pacific Ocean are primarily responsible for the changes in cross-equatorial ocean heat transport. Specifically, stronger easterly anomalies north of the equator in the western Pacific drives an anomalous northward mass transport, and therefore accomplishes an anomalous northward heat transport across the equator by acting on the asymmetric mean-state zonal temperature. The wind anomalies responsible for this anomalous ocean heat transport are seen in every PMIP3 model, as well as an ECHAM4-slab ocean model, indicating that it is atmospherically driven and independent of the changes in ocean heat transport. It also explains the consistency of ocean heat transport change, and eventually the relative consistency of zonal

  3. Analysis of KMnO/sub 4//NaOH battery header cleaning procedure

    SciTech Connect

    Douglas, S.C.; Bunker, B.C.; Proctor-Puissant, P.M.; Hallett, S.G.; Yelton, W.G.

    1988-12-01

    KMnO/sub 4//NaOH solutions are used to remove the oxides that form on the stainless steel conductor of battery headers during high-temperature glass sealing operations. The cleaning procedure has been evaluated to determine if these corrosive solutions damage TA-23 glass insulators to a degree that would make the headers unacceptable. Battery headers and solid pieces of TA-23 glass were tested, and a colorimetric method was developed to analyze reaction products in the solutions. The analyses showed that the solutions contained 1--10 ..mu..g SiO/sub 2/per mL, indicating minimal deterioration of the glass. The procedure is an acceptable method for cleaning battery headers containing TA-23 glass insulators. 11 refs., 4 figs., 2 tabs.

  4. Directional heat transport through thermal reflection meta-device

    NASA Astrophysics Data System (ADS)

    Hu, Run; Zhou, Shuling; Shu, Weicheng; Xie, Bin; Ma, Yupu; Luo, Xiaobing

    2016-12-01

    Directional heat transfer may be hard to realize due to the fact that heat transfer is diffusive. In this paper, we try to take one step forward based on the transformation thermodynamics. A special structure and meta-device is proposed to "reflect" the heat flow directionally-just like the mirror to the light beam, in which the heat flow just one-time changes the direction rather than gradually changing the directions in isotropic materials. The benefits of such thermal reflection meta-device are discussed by comparing the corresponding thermal resistance with the same structures of isotropic materials. The proposed meta-device is verified to possess the low thermal resistance and high heat transfer ability with least energy loss, and can be made by nature-existing isotropic materials with specific structures.

  5. Development and Analysis of Advanced High-Temperature Technology for Nuclear Heat Transport and Power Conversion

    SciTech Connect

    Per F. Peterson

    2010-03-01

    This project by the Thermal Hydraulics Research Laboratory at U.C. Berkeley Studied advanced high-temperature heat transport and power conversion technology, in support of the Nuclear Hydrogen Initiative and Generation IV.

  6. Intestinal transport of hexoses in the rat following chronic heat exposure

    NASA Technical Reports Server (NTRS)

    Carpenter, M.; Musacchia, X. J.

    1979-01-01

    The study examines intestinal transport of sugars (D-glucose and D-galactose) in vitro and assesses organ maintenance in chronically heat-exposed rats. The results suggest that the response of intestinal absorption to heat exposure in the rat involves changes in intestinal weight and in glucose utilization. Despite the reduction in total intestinal weight, the ability of intestinal tissue to transport hexose per unit weight remains stable. Differences in intestinal weight and glucose utilization between pair-fed and heat-exposed animals suggest that the intestinal response to chronic heat exposure is not solely a function of the amount of food consumed. Alterations of hexose transport appear to be related to altered glucose metabolism and not altered transport capacity.

  7. ANALYZING NUMERICAL ERRORS IN DOMAIN HEAT TRANSPORT MODELS USING THE CVBEM.

    USGS Publications Warehouse

    Hromadka, T.V.; ,

    1985-01-01

    Besides providing an exact solution for steady-state heat conduction processes (Laplace Poisson equations), the CVBEM (complex variable boundary element method) can be used for the numerical error analysis of domain model solutions. For problems where soil water phase change latent heat effects dominate the thermal regime, heat transport can be approximately modeled as a time-stepped steady-state condition in the thawed and frozen regions, respectively. The CVBEM provides an exact solution of the two-dimensional steady-state heat transport problem, and also provides the error in matching the prescribed boundary conditions by the development of a modeling error distribution or an approximative boundary generation. This error evaluation can be used to develop highly accurate CVBEM models of the heat transport process, and the resulting model can be used as a test case for evaluating the precision of domain models based on finite elements or finite differences.

  8. Ocean heat transport in Simple Ocean Data Assimilation: Structure and mechanisms

    NASA Astrophysics Data System (ADS)

    Zheng, Yangxing; Giese, Benjamin S.

    2009-11-01

    The trend and variability of global ocean heat transport for the period 1958-2004 are investigated using the Simple Ocean Data Assimilation (SODA) analysis. The ocean model is forced with the European Center for Medium Range Weather Forecast (ECMWF) ERA-40 atmospheric reanalysis winds from 1958 to 2001 and with QuikSCAT winds from 2002 to 2004. The assimilation is based on a sequential estimation algorithm, with observations from the historical archive of hydrographic profiles supplemented by ship intake measurements, moored hydrographic observations and remotely sensed sea surface temperature. Heat transport is calculated using temperature and velocity from the ocean analysis. Mean heat transport from the analysis generally agrees with previously published estimates from observational and modeling studies. Trends of heat transport show a range of behaviors. In the Atlantic and Pacific Oceans there is mostly increasing poleward heat transport with two important exceptions. In the Atlantic Ocean there is decreasing heat transport around 50°N and 60°N, and in both the Atlantic and Pacific Oceans there is decreasing heat transport near 10°S. There is also prominent interannual and decadal variability in all of the ocean basins. The results suggest that ocean heat transport variability is primarily determined by the strength of the meridional overturning circulation (MOC), which is controlled by complex processes governing fresh water flux in the northern North Atlantic and surface wind stress. However, the role of temperature variability increases at high latitude, particularly in the northern North Atlantic Ocean. Eddies play an important role in heat transport in the Gulf Stream and its extension in the Atlantic Ocean, and the Kuroshio and its extension in the Pacific Ocean and enhanced Subtropical cells (STCs) affect heat transport estimates in the tropics. In the northern North Atlantic Ocean, a small increase in meridional heat transport and a slight weakening

  9. Radiative heat transport instability in a laser produced inhomogeneous plasma

    SciTech Connect

    Bychenkov, V. Yu.; Rozmus, W.

    2015-08-15

    A laser produced high-Z plasma in which an energy balance is achieved due to radiation emission and radiative heat transfer supports ion acoustic instability. A linear dispersion relation is derived, and instability is compared to the radiation cooling instability [R. G. Evans, Plasma Phys. Controlled Fusion 27, 751 (1985)]. Under conditions of indirect drive fusion experiments, the driving term for the instability is the radiative heat flux and, in particular, the density dependence of the radiative heat conductivity. A specific example of thermal Bremsstrahlung radiation source has been considered. This instability may lead to plasma jet formation and anisotropic x-ray generation, thus affecting inertial confinement fusion related experiments.

  10. Eddy heat and salt transports in the South China Sea and their seasonal modulations

    NASA Astrophysics Data System (ADS)

    Chen, Gengxin; Gan, Jianping; Xie, Qiang; Chu, Xiaoqing; Wang, Dongxiao; Hou, Yijun

    2012-05-01

    This study describes characteristics of eddy (turbulent) heat and salt transports, in the basin-scale circulation as well as in the embedded mesoscale eddy found in the South China Sea (SCS). We first showed the features of turbulent heat and salt transports in mesoscale eddies using sea level anomaly (SLA) data, in situ hydrographic data, and 375 Argo profiles. We found that the transports were horizontally variable due to asymmetric distributions of temperature and salinity anomalies and that they were vertically correlated with the thermocline and halocline depths in the eddies. An existing barrier layer caused the halocline and eddy salt transport to be relatively shallow. We then analyzed the transports in the basin-scale circulation using an eddy diffusivity method and the sea surface height data, the Argo profiles, and the climatological hydrographic data. We found that relatively large poleward eddy heat transports occurred to the east of Vietnam (EOV) in summer and to the west of the Luzon Islands (WOL) in winter, while a large equatorward heat transport was located to the west of the Luzon Strait (WLS) in winter. The eddy salt transports were mostly similar to the heat transports but in the equatorward direction due to the fact that the mean salinity in the upper layer in the SCS tended to decrease toward the equator. Using a 21/2-layer reduced-gravity model, we conducted a baroclinic instability study and showed that the baroclinic instability was critical to the seasonal variation of eddy kinetic energy (EKE) and thus the eddy transports. EOV, WLS, and WOL were regions with strong baroclinic instability, and, thus, with intensified eddy transports in the SCS. The combined effects of vertical velocity shear, latitude, and stratification determined the intensity of the baroclinic instability, which intensified the eddy transports EOV during summer and WLS and WOL during winter.

  11. Heat transport measurements in turbulent rotating Rayleigh-Bénard convection.

    PubMed

    Liu, Yuanming; Ecke, Robert E

    2009-09-01

    We present experimental heat transport measurements of turbulent Rayleigh-Bénard convection with rotation about a vertical axis. The fluid, water with a Prandtl number (sigma) of about 6, was confined in a cell with a square cross section of 7.3 x 7.3 cm2 and a height of 9.4 cm. Heat transport was measured for Rayleigh numbers 2 x 10(5)heat transport, the Nusselt number, at fixed dimensional rotation rate OmegaD, at fixed Ra varying Ta, at fixed Ta varying Ra, and at fixed Rossby number Ro. The scaling of heat transport in the range of 10(7) to about 10(9) is roughly 0.29 with a Ro-dependent coefficient or equivalently is also well fit by a combination of power laws of the form a Ra1/5+b Ra1/3. The range of Ra is not sufficient to differentiate single power law or combined power-law scaling. The data are roughly consistent with an assumption that the enhancement of heat transport owing to rotation is proportional to the number of vortical structures penetrating the boundary layer. We also compare indirect measures of thermal and Ekman boundary layer thicknesses to assess their potential role in controlling heat transport in different regimes of Ra and Ta.

  12. DYNAMICS OF WATER TRANSPORT AND STORAGE IN CONIFERS STUDIED WITH DEUTERIUM AND HEAT TRACING TECHNIQUES

    EPA Science Inventory

    The volume and complexity of their vascular systems make the dynamics of long-distance water transport difficult to study. We used heat and deuterated water (D2O) as tracers to characterize whole-tree water transport and storage properties in individual trees belonging to the co...

  13. A statistical analysis of avalanching heat transport in stationary enhanced core confinement regimes

    SciTech Connect

    Tokunaga, S.; Jhang, Hogun; Kim, S. S.; Diamond, P. H.

    2012-09-15

    We present a statistical analysis of heat transport in stationary enhanced confinement regimes obtained from flux-driven gyrofluid simulations. The probability density functions of heat flux in improved confinement regimes, characterized by the Nusselt number, show significant deviation from Gaussian, with a markedly fat tail, implying the existence of heat avalanches. Two types of avalanching transport are found to be relevant to stationary states, depending on the degree of turbulence suppression. In the weakly suppressed regime, heat avalanches occur in the form of quasi-periodic (QP) heat pulses. Collisional relaxation of zonal flow is likely to be the origin of these QP heat pulses. This phenomenon is similar to transient limit cycle oscillations observed prior to edge pedestal formation in recent experiments. On the other hand, a spectral analysis of heat flux in the strongly suppressed regime shows the emergence of a 1/f (f is the frequency) band, suggesting the presence of self-organized criticality (SOC)-like episodic heat avalanches. This episodic 1/f heat avalanches have a long temporal correlation and constitute the dominant transport process in this regime.

  14. Transports and budgets of volume, heat, and salt from a global eddy-resolving ocean model

    SciTech Connect

    McCann, M.P.; Semtner, A.J. Jr.; Chervin, R.M.

    1994-07-01

    The results from an integration of a global ocean circulation model have been condensed into an analysis of the volume, heat, and salt transports among the major ocean basins. Transports are also broken down between the model`s Ekman, thermocline, and deep layers. Overall, the model does well. Horizontal exchanges of mass, heat, and salt between ocean basins have reasonable values: and the volume of North Atlantic Deep Water (NADW) transport is in general agreement with what limited observations exist. On a global basis the zonally integrated meridional heat transport is poleward at all latitudes except for the latitude band 30{degrees}S to 45{degrees}S. This anomalous transport is most likely a signature of the model`s inability to form Antarctic Intermediate (AAIW) and Antarctic bottom water (AABW) properly. Eddy heat transport is strong at the equator where its convergence heats the equatorial Pacific about twice as much as it heats the equatorial Atlantic. The greater heating in the Pacific suggests that mesoscale eddies may be a vital mechanism for warming and maintaining an upwelling portion of the global conveyor-belt circulation. The model`s fresh water transport compares well with observations. However, in the Atlantic there is an excessive southward transport of fresh water due to the absence of the Mediterranean outflow and weak northward flow of AAIW. Perhaps the model`s greatest weakness is the lack of strong AAIW and AABW circulation cells. Accurate thermohaline forcing in the North Atlantic (based on numerous hydrographic observations) helps the model adequately produce NADW. In contrast, the southern ocean is an area of sparse observation. Better thermohaline observations in this area may be needed if models such as this are to produce the deep convection that will achieve more accurate simulations of the global 3-dimensional circulation. 41 refs., 18 figs., 1 tab.

  15. Effect of correlations on heat transport in a magnetized strongly coupled plasma

    NASA Astrophysics Data System (ADS)

    Ott, T.; Bonitz, M.; Donkó, Z.

    2015-12-01

    In a classical ideal plasma, a magnetic field is known to reduce the heat conductivity perpendicular to the field, whereas it does not alter the one along the field. Here we show that, in strongly correlated plasmas that are observed at high pressure and/or low temperature, a magnetic field reduces the perpendicular heat transport much less and even enhances the parallel transport. These surprising observations are explained by the competition of kinetic, potential, and collisional contributions to the heat conductivity. Our results are based on first-principle molecular dynamics simulations of a one-component plasma.

  16. Operational demonstration of a field of high performance flat plate collectors with isothermal heat transport

    NASA Astrophysics Data System (ADS)

    Merges, V.; Klippel, E.

    1983-12-01

    A solar plant with 21 sq m of highly efficient flat plate collectors and which requires no electricity is described. Heat transport is provided by saturated steam that condenses in a four cubic meter storage tank. The operation temperature is set by the buffer gas pressure between 100 and 140 C, and an absorption chiller is simulated as a heat consumer. The solar collectors were observed to exhibit high performance. Heat transport and temperature control offered high reliability and the thermal stratification in the tank was satisfactory. The positive result permits the design and construction of larger solar plants following the same technical principles.

  17. Modeling of heat transport through Fractures with emphasis to roughness and aperture variability

    NASA Astrophysics Data System (ADS)

    Nigon, Benoit; Englert, Andreas; Pascal, Christophe

    2015-04-01

    Fractured media are characterized by multi-scale heterogeneities implying high spatial variability of hydraulic properties. At the fracture network scale, spatial organization of fluxes is controlled by the fracture network geometry, itself characterized by fracture connectivity, fracture density, and the respective lengths and apertures of the fractures within the network. At the fracture scale, the variability of the fluxes is mainly controlled by fracture roughness and aperture variability. The multi-scale heterogeneities of fractured rocks imply complexities for prediction of solute and heat transport in space and time, and often lead to the so-called "anomalous transport" behavior. In homogeneous media, heat transport can be described using Fourier's law opening the possibility to apply the advection-dispersion equation to predict transport behavior. However, in real fractured media a "non-Fourier transport" often dominates. The latter phenomenon, characterized by asymmetric breakthrough shape, early breakthrough and long tailing cannot be described by the classical advection-dispersion equation. In the present study, we focus on heat transport within a single fracture and we explore the respective roles of fracture roughness and aperture variability. Fracture roughness has two main effects on heat transport, flow channeling and a spatial variation of heat exchange area between fluid and rock. Fracture aperture variability controls the variability of fracture flow, and thus induces spatial variation of heat transport in a fracture. Micro- to macro-scale fracture roughness measurements will be performed in the field and the laboratory using a terrestrial LIDAR, a X-Ray CT-Scanner Alpha, and a Microscope Keyence VHX 100. Thereafter the measurements will be used to better describe fracture geometry taking in account discontinuity type. To further improve the understanding of heat transfer between fracture and matrix, we will numerically model heat transport as

  18. Nonlinear heat transport in mesoscopic conductors: Rectification, Peltier effect, and Wiedemann-Franz law

    NASA Astrophysics Data System (ADS)

    López, Rosa; Sánchez, David

    2013-07-01

    We investigate nonlinear heat properties in mesoscopic conductors using a scattering theory of transport. Our approach is based on a leading-order expansion in both the electrical and thermal driving forces. Beyond linear response, the transport coefficients are functions of the nonequilibrium screening potential that builds up in the system due to interactions. Within a mean-field approximation, we self-consistently calculate the heat rectification properties of a quantum dot attached to two terminals. We discuss nonlinear contributions to the Peltier effect and find departures from the Wiedemann-Franz law in the nonlinear regime of transport.

  19. Heat and fresh water transport by eddies into the Gulf of Alaska

    NASA Astrophysics Data System (ADS)

    Crawford, William R.

    2005-04-01

    Anticyclonic mesoscale eddies form in winter along the continental margin of Canada and Southeast Alaska between the latitudes of 51N and 60N and drift westward into the Gulf of Alaska, carrying warmer, fresher water away from the continental margin. Detailed measurements of temperature and salinity between 1995 and 2001 were examined to determine the amount of heat and fresh water transported seaward by several eddies that formed west of the Queen Charlotte Islands. Eddies formed in a typical winter carry about 30×10 18 J of heat into the gulf, which is about 35% to 60% of the heat transported northward each winter along the continental margin toward this region. The observed range of eddy heat transport is 10 19 to 10 20 J. Largest observed eddy heat transport coincided with increased northward heat flow along the continental margin during the El Niño winter of 1997/1998. Fresh-water volume was determined by evaluating the amount of fresh water required to reduce the salinity from a reference level to that observed in eddies. This volume varied from 0 to 70 km 3, and was largest during the 1997/1998 El Niño winter. Eddies formed in a typical winter transport 50 km 3 of fresh water seaward, which is about 15% of the estimated fresh-water input to the continental margin in winter between the Columbia River and 54N attributed to local runoff, plus direct rainfall and flow in major rivers.

  20. Role of ocean heat transport in climates of tidally locked exoplanets around M dwarf stars

    PubMed Central

    Hu, Yongyun; Yang, Jun

    2014-01-01

    The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar radiation between the dayside and nightside. Previous work has focused on the role of atmospheric heat transport in preventing atmospheric collapse on the nightside for terrestrial exoplanets in the habitable zone around M dwarfs. In the present paper, we carry out simulations with a fully coupled atmosphere–ocean general circulation model to investigate the role of ocean heat transport in climate states of tidally locked habitable exoplanets around M dwarfs. Our simulation results demonstrate that ocean heat transport substantially extends the area of open water along the equator, showing a lobster-like spatial pattern of open water, instead of an “eyeball.” For sufficiently high-level greenhouse gases or strong stellar radiation, ocean heat transport can even lead to complete deglaciation of the nightside. Our simulations also suggest that ocean heat transport likely narrows the width of M dwarfs’ habitable zone. This study provides a demonstration of the importance of exooceanography in determining climate states and habitability of exoplanets. PMID:24379386

  1. Heat transport in the Red Lake Bog, Glacial Lake Agassiz Peatlands

    USGS Publications Warehouse

    McKenzie, J.M.; Siegel, D.I.; Rosenberry, D.O.; Glaser, P.H.; Voss, C.I.

    2007-01-01

    We report the results of an investigation on the processes controlling heat transport in peat under a large bog in the Glacial Lake Agassiz Peatlands. For 2 years, starting in July 1998, we recorded temperature at 12 depth intervals from 0 to 400 cm within a vertical peat profile at the crest of the bog at sub-daily intervals. We also recorded air temperature 1 m above the peat surface. We calculate a peat thermal conductivity of 0.5 W m-1 ??C-1 and model vertical heat transport through the peat using the SUTRA model. The model was calibrated to the first year of data, and then evaluated against the second year of collected heat data. The model results suggest that advective pore-water flow is not necessary to transport heat within the peat profile and most of the heat is transferred by thermal conduction alone in these waterlogged soils. In the spring season, a zero-curtain effect controls the transport of heat through shallow depths of the peat. Changes in local climate and the resulting changes in thermal transport still may cause non-linear feedbacks in methane emissions related to the generation of methane deeper within the peat profile as regional temperatures increase. Copyright ?? 2006 John Wiley & Sons, Ltd.

  2. Role of ocean heat transport in climates of tidally locked exoplanets around M dwarf stars.

    PubMed

    Hu, Yongyun; Yang, Jun

    2014-01-14

    The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar radiation between the dayside and nightside. Previous work has focused on the role of atmospheric heat transport in preventing atmospheric collapse on the nightside for terrestrial exoplanets in the habitable zone around M dwarfs. In the present paper, we carry out simulations with a fully coupled atmosphere-ocean general circulation model to investigate the role of ocean heat transport in climate states of tidally locked habitable exoplanets around M dwarfs. Our simulation results demonstrate that ocean heat transport substantially extends the area of open water along the equator, showing a lobster-like spatial pattern of open water, instead of an "eyeball." For sufficiently high-level greenhouse gases or strong stellar radiation, ocean heat transport can even lead to complete deglaciation of the nightside. Our simulations also suggest that ocean heat transport likely narrows the width of M dwarfs' habitable zone. This study provides a demonstration of the importance of exooceanography in determining climate states and habitability of exoplanets.

  3. Combined Heat, Air, Moisture, and Pollutants Transport in Building Environmental Systems

    NASA Astrophysics Data System (ADS)

    Zhang, Jianshun Jensen S.

    Combined heat, air, moisture and pollutants transport (CHAMP) exists across multi-scales of a building environmental system (BES): around the building, through the building shell/envelope, inside a multizone building, and in the micro-environments around occupants. This paper reviews previous work and presents a system model for simulating these transport processes and their impacts on indoor environmental quality. Components of the system model include a multizone network flow model for whole building, a room model for air and pollutant movement in ventilated spaces, a coupled heat, air, moisture, and pollutant transport model for building shell, an HVAC model for describing the dynamics of the heating, ventilating and air-conditioning (HVAC) system, and shared databases of weather conditions, transport properties of building materials, and volatile organic compounds (VOCs) emissions from building materials and furnishings. The interactions among the different components, and challenges in developing the CHAMP system model for intelligent control of BES are also discussed.

  4. Oxygen transport membrane system and method for transferring heat to catalytic/process reactors

    DOEpatents

    Kelly, Sean M; Kromer, Brian R; Litwin, Michael M; Rosen, Lee J; Christie, Gervase Maxwell; Wilson, Jamie R; Kosowski, Lawrence W; Robinson, Charles

    2014-01-07

    A method and apparatus for producing heat used in a synthesis gas production is provided. The disclosed method and apparatus include a plurality of tubular oxygen transport membrane elements adapted to separate oxygen from an oxygen containing stream contacting the retentate side of the membrane elements. The permeated oxygen is combusted with a hydrogen containing synthesis gas stream contacting the permeate side of the tubular oxygen transport membrane elements thereby generating a reaction product stream and radiant heat. The present method and apparatus also includes at least one catalytic reactor containing a catalyst to promote the stream reforming reaction wherein the catalytic reactor is surrounded by the plurality of tubular oxygen transport membrane elements. The view factor between the catalytic reactor and the plurality of tubular oxygen transport membrane elements radiating heat to the catalytic reactor is greater than or equal to 0.5.

  5. Oxygen transport membrane system and method for transferring heat to catalytic/process reactors

    DOEpatents

    Kelly, Sean M.; Kromer, Brian R.; Litwin, Michael M.; Rosen, Lee J.; Christie, Gervase Maxwell; Wilson, Jamie R.; Kosowski, Lawrence W.; Robinson, Charles

    2016-01-19

    A method and apparatus for producing heat used in a synthesis gas production process is provided. The disclosed method and apparatus include a plurality of tubular oxygen transport membrane elements adapted to separate oxygen from an oxygen containing stream contacting the retentate side of the membrane elements. The permeated oxygen is combusted with a hydrogen containing synthesis gas stream contacting the permeate side of the tubular oxygen transport membrane elements thereby generating a reaction product stream and radiant heat. The present method and apparatus also includes at least one catalytic reactor containing a catalyst to promote the steam reforming reaction wherein the catalytic reactor is surrounded by the plurality of tubular oxygen transport membrane elements. The view factor between the catalytic reactor and the plurality of tubular oxygen transport membrane elements radiating heat to the catalytic reactor is greater than or equal to 0.5

  6. Remote joule heating assisted carrier transport in MWCNTs probed at nanosecond time scale.

    PubMed

    Mishra, Abhishek; Shrivastava, Mayank

    2016-10-19

    Quantum model of joule heating relies on electron-phonon scattering in the high field region (hot side contact), which locally increases phonon population and forms hot spots. Hot spots in the high field region are known to suffer carrier transport. In this work, for the first time we report remote joule heating of the cold side contact, i.e. zero electric field region, through multi-walled CNTs (MWCNTs), which is discovered to assist in carrier transport through the MWCNT channels. To precisely capture the dynamics of remote joule heating assisted carrier transport, MWCNTs are probed at nanosecond time scales. This leverages investigations at time scales comparable to characteristic thermal diffusion times and allows electron-phonon interactions and the nature of carrier transport to be probed under non-equilibrium conditions.

  7. Modification of the finite element heat and mass transfer code (FEHMN) to model multicomponent reactive transport

    SciTech Connect

    Viswanathan, H.S.

    1995-12-31

    The finite element code FEHMN is a three-dimensional finite element heat and mass transport simulator that can handle complex stratigraphy and nonlinear processes such as vadose zone flow, heat flow and solute transport. Scientists at LANL have been developed hydrologic flow and transport models of the Yucca Mountain site using FEHMN. Previous FEHMN simulations have used an equivalent K{sub d} model to model solute transport. In this thesis, FEHMN is modified making it possible to simulate the transport of a species with a rigorous chemical model. Including the rigorous chemical equations into FEHMN simulations should provide for more representative transport models for highly reactive chemical species. A fully kinetic formulation is chosen for the FEHMN reactive transport model. Several methods are available to computationally implement a fully kinetic formulation. Different numerical algorithms are investigated in order to optimize computational efficiency and memory requirements of the reactive transport model. The best algorithm of those investigated is then incorporated into FEHMN. The algorithm chosen requires for the user to place strongly coupled species into groups which are then solved for simultaneously using FEHMN. The complete reactive transport model is verified over a wide variety of problems and is shown to be working properly. The simulations demonstrate that gas flow and carbonate chemistry can significantly affect {sup 14}C transport at Yucca Mountain. The simulations also provide that the new capabilities of FEHMN can be used to refine and buttress already existing Yucca Mountain radionuclide transport studies.

  8. Size effects in long-term quasistatic heat transport.

    PubMed

    Panasyuk, George Y; Yerkes, Kirk L

    2013-06-01

    We consider finite-size effects on heat transfer between thermal reservoirs mediated by a quantum system, where the number of modes in each reservoir is finite. Our approach is based on the generalized quantum Langevin equation and the thermal reservoirs are described as ensembles of oscillators within the Drude-Ullersma model. A general expression for the heat current between the thermal reservoirs in the long-time quasistatic regime, when an observation time is of the order of Δ(-1) and Δ is the mode spacing constant of a thermal reservoir, is obtained. The resulting equations that govern the long-time relaxation for the mode temperatures and the average temperatures of the reservoirs are derived and approximate analytical solutions are found. The obtained time dependencies of the temperatures and the resulting heat current reveal peculiarities at t=2πm/Δ with non-negative integers m and the heat current vanishes nonmonotonically when t→∞. The validity of Fourier's law for a chain of finite-size macroscopic subsystems is considered. As is shown, for characteristic times of the order of Δ(-1) the temperatures of subsystems' modes deviate from each other and the validity of Fourier's law cannot be established. In a case when deviations of initial temperatures of the subsystems from their average value are small, t→∞ asymptotic values for the mode temperatures do not depend on a mode's number and are the same as if Fourier's law were valid for all times.

  9. Size effects in long-term quasistatic heat transport

    NASA Astrophysics Data System (ADS)

    Panasyuk, George Y.; Yerkes, Kirk L.

    2013-06-01

    We consider finite-size effects on heat transfer between thermal reservoirs mediated by a quantum system, where the number of modes in each reservoir is finite. Our approach is based on the generalized quantum Langevin equation and the thermal reservoirs are described as ensembles of oscillators within the Drude-Ullersma model. A general expression for the heat current between the thermal reservoirs in the long-time quasistatic regime, when an observation time is of the order of Δ-1 and Δ is the mode spacing constant of a thermal reservoir, is obtained. The resulting equations that govern the long-time relaxation for the mode temperatures and the average temperatures of the reservoirs are derived and approximate analytical solutions are found. The obtained time dependencies of the temperatures and the resulting heat current reveal peculiarities at t=2πm/Δ with non-negative integers m and the heat current vanishes nonmonotonically when t→∞. The validity of Fourier's law for a chain of finite-size macroscopic subsystems is considered. As is shown, for characteristic times of the order of Δ-1 the temperatures of subsystems' modes deviate from each other and the validity of Fourier's law cannot be established. In a case when deviations of initial temperatures of the subsystems from their average value are small, t→∞ asymptotic values for the mode temperatures do not depend on a mode's number and are the same as if Fourier's law were valid for all times.

  10. Heat Treatments of ZnSe Starting Materials for Physical Vapor Transport

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Palosz, W.; Feth, S.; Lehoczky, S. L.

    1998-01-01

    The effect of different heat treatments on stoichiometry and residual gas pressure in ZnSe physical vapor transport system was investigated. The dependence of the amount and composition of the residual gas on various heat treatment procedures is reported. Heat treatment of ZnSe starting materials by baking under the condition of dynamic vacuum to adjust its stoichiometry was performed and the effectiveness of the treatment was confirmed by the measurements of the partial pressure of Se2, P(sub Se2), in equilibrium with the heat treated samples. Optimum heat treatment procedures on the ZnSe starting material for the physical vapor transport process are discussed and verified experimentally.

  11. Absorption of intense microwaves and ion acoustic turbulence due to heat transport

    SciTech Connect

    De Groot, J.S.; Liu, J.M.; Matte, J.P.

    1994-02-04

    Measurements and calculations of the inverse bremsstrahlung absorption of intense microwaves are presented. The isotropic component of the electron distribution becomes flat-topped in agreement with detailed Fokker-Planck calculations. The plasma heating is reduced due to the flat-topped distributions in agreement with calculations. The calculations show that the heat flux at high microwave powers is very large, q{sub max} {approx} 0.3 n{sub e}v{sub e}T{sub e}. A new particle model to, calculate the heat transport inhibition due to ion acoustic turbulence in ICF plasmas is also presented. One-dimensional PIC calculations of ion acoustic turbulence excited due to heat transport are presented. The 2-D PIC code is presently being used to perform calculations of heat flux inhibition due to ion acoustic turbulence.

  12. Heat Treatments of ZnSe Starting Materials for Physical Vapor Transport

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Palosz, W.; Feth, S.; Lehoczky, S. L.

    1997-01-01

    The effect of different heat treatments on stoichiometry and residual gas pressure in ZnSe physical vapor transport system was investigated. The dependence of the amount and composition of the residual gas on various heat treatment procedures is reported. Heat treatment of ZnSe starting materials by baking under the condition of dynamic vacuum to adjust its stoichiometry was performed and the effectiveness of the treatment was confirmed by the measurements of the partial pressure of Se2, P(sub Se2), in equilibrium with the heat treated samples. Optimum heat treatment procedures on the ZnSe starting material for the physical vapor transport process are discussed and verified experimentally.

  13. Effect of wind forcing on the meridional heat transport in a coupled climate model: equilibrium response

    NASA Astrophysics Data System (ADS)

    Yang, Haijun; Dai, Haijin

    2015-09-01

    The effect of the ocean surface winds on the meridional heat transports is studied in a coupled model. Shutting down the global surface winds causes significant reductions in both wind-driven and thermohaline ocean circulations, resulting in a remarkable decrease in the poleward oceanic heat transport (OHT). The sea surface temperature responds with significant warming in the equator and cooling off the equator, causing an enhancement and equatorward shift in the Hadley cell. This increases the poleward atmospheric heat transport (AHT), which in turn compensates the decrease in the OHT. This compensation implies a fundamental constraint in changes of ocean-atmosphere energy transports. Several other compensation changes are also identified. For the OHT components, the changes in the Eulerian mean and bolus OHT are compensated with each other in the Southern Ocean, since a stronger wind driven Ekman transport is associated with a stronger meridional density gradient (stronger bolus circulation) and vice versa. For the AHT components, the changes in the dry static energy (DSE) and latent energy transports are compensated within the tropics (30°N/S), because a stronger Hadley cell causes a stronger equatorward convergence of moisture. In the extratropics, the changes in the mean and eddy DSE transports show perfect compensation, as a result of the equatorward shift of the Ferrell Cell and enhancement of atmospheric baroclinicity in mid-high latitudes, particularly over the North Atlantic. This work also shows how the Earth's climate is trying to maintain the balance between two hemispheres: the ocean in the Northern Hemisphere is colder than that in the Southern Hemisphere due to much reduced northward heat transports cross the Equator in the Atlantic, therefore, the atmosphere responds to the ocean with temperature colder in the Southern Hemisphere than in the Northern Hemisphere by transporting more heat northward cross the equator over the Pacific, in association

  14. The general circulation and meridional heat transport of the subtropical South Atlantic determined by inverse methods

    NASA Technical Reports Server (NTRS)

    Fu, L.-L.

    1981-01-01

    The circulation and meridional heat transport of the subtropical South Atlantic Ocean are determined through the application of the inverse method of Wunsch (1978) to hydrographic data from the IGY and METEOR expeditions. Meridional circulation results of the two data sets agree on a northward mass transport of about 20 million metric tons/sec for waters above the North Atlantic Deep Water (NADW), and a comparable southward transport of deep waters. Additional gross features held in common are the Benguela, South Equatorial and North Brazilian Coastal currents' northward transport of the Surface Water, and the deflection of the southward-flowing NADW from the South American Coast into the mid ocean by a seamount chain near 20 deg S. Total heat transport is equatorward, with a magnitude of 0.8 X 10 to the 15th W near 30 deg S and indistinguishable from zero near 8 deg S.

  15. CONSEQUENCES OF MAGNETIC FIELD STRUCTURE FOR HEAT TRANSPORT IN MAGNETOHYDRODYNAMICS

    SciTech Connect

    Li Shule; Frank, Adam; Blackman, Eric

    2012-03-20

    Interfaces between hot and cold magnetized plasmas exist in various astrophysical contexts, for example, where hot outflows impinge on an ambient interstellar medium. It is of interest to understand how the structure of the magnetic field spanning the interface affects the temporal evolution of the temperature gradient. Here, we explore the relation between the magnetic field topology and the heat transfer rate by adding various fractions of tangled versus ordered field across a hot-cold interface that allows the system to evolve to a steady state. We find a simple mathematical relation for the rate of heat conduction as a function of the initial ratio of ordered-to-tangled field across the interface. We discuss potential implications for the astrophysical context of magnetized wind blown bubbles around evolved stars.

  16. Water and heat transport in boreal soils: implications for soil response to climate change.

    PubMed

    Fan, Zhaosheng; Neff, Jason C; Harden, Jennifer W; Zhang, Tingjun; Veldhuis, Hugo; Czimczik, Claudia I; Winston, Gregory C; O'Donnell, Jonathan A

    2011-04-15

    Soil water content strongly affects permafrost dynamics by changing the soil thermal properties. However, the movement of liquid water, which plays an important role in the heat transport of temperate soils, has been under-represented in boreal studies. Two different heat transport models with and without convective heat transport were compared to measurements of soil temperatures in four boreal sites with different stand ages and drainage classes. Overall, soil temperatures during the growing season tended to be over-estimated by 2-4°C when movement of liquid water and water vapor was not represented in the model. The role of heat transport in water has broad implications for site responses to warming and suggests reduced vulnerability of permafrost to thaw at drier sites. This result is consistent with field observations of faster thaw in response to warming in wet sites compared to drier sites over the past 30 years in Canadian boreal forests. These results highlight that representation of water flow in heat transport models is important to simulate future soil thermal or permafrost dynamics under a changing climate.

  17. Water and heat transport in boreal soils: Implications for soil response to climate change

    USGS Publications Warehouse

    Fan, Z.; Neff, J.C.; Harden, J.W.; Zhang, T.; Veldhuis, H.; Czimczik, C.I.; Winston, G.C.; O'Donnell, J. A.

    2011-01-01

    Soil water content strongly affects permafrost dynamics by changing the soil thermal properties. However, the movement of liquid water, which plays an important role in the heat transport of temperate soils, has been under-represented in boreal studies. Two different heat transport models with and without convective heat transport were compared to measurements of soil temperatures in four boreal sites with different stand ages and drainage classes. Overall, soil temperatures during the growing season tended to be over-estimated by 2-4??C when movement of liquid water and water vapor was not represented in the model. The role of heat transport in water has broad implications for site responses to warming and suggests reduced vulnerability of permafrost to thaw at drier sites. This result is consistent with field observations of faster thaw in response to warming in wet sites compared to drier sites over the past 30. years in Canadian boreal forests. These results highlight that representation of water flow in heat transport models is important to simulate future soil thermal or permafrost dynamics under a changing climate. ?? 2011 Elsevier B.V.

  18. Transient conductive, radiative heat transfer coupled with moisture transport in attic insulations

    NASA Astrophysics Data System (ADS)

    Gorthala, R.; Harris, K. T.; Roux, J. A.; McCarty, T. A.

    1994-01-01

    A transient, one-dimensional thermal model that incorporates combined conduction, radiation heat transfer, and moisture transport for residential attic insulations has been developed. The governing equations are the energy equation, the radiative transport equation for volumetric radiation within the insulation batt, and the species equations for bound H2O and vapor H2O. A simultaneous solution procedure with a Eulerian control volume-based finite difference method was used to solve the energy equation and the species equations. The method of discrete ordinates was used in solving the radiative transport equation. For H2O transport, both diffusion of vapor H2O and bound H2O and moisture adsorption/desorption within the insulation binder are included in the model. The experimental data measured at an occupied North Mississippi residence for R19STD (standard R19 fiberglass insulation batt without a foil radiant barrier) were used to validate the model which predicted heat fluxes for summer, spring, winter, and fall seasonal conditions. These predictions were compared with the measured heat flux data and the predictions from the dry model (without the moisture transport). Various profiles such as temperature-time histories, relative humidity time histories, spatial H2O concentrations, spatial temperatures, and spatial heat fluxes are presented to explain the overall heat transfer behavior.

  19. Pump, and earth-testable spacecraft capillary heat transport loop using augmentation pump and check valves

    NASA Technical Reports Server (NTRS)

    Baker, David (Inventor)

    1998-01-01

    A spacecraft includes heat-generating payload equipment, and a heat transport system with a cold plate thermally coupled to the equipment and a capillary-wick evaporator, for evaporating coolant liquid to cool the equipment. The coolant vapor is coupled to a condenser and in a loop back to the evaporator. A heated coolant reservoir is coupled to the loop for pressure control. If the wick is not wetted, heat transfer will not begin or continue. A pair of check valves are coupled in the loop, and the heater is cycled for augmentation pumping of coolant to and from the reservoir. This augmentation pumping, in conjunction with the check valves, wets the wick. The wick liquid storage capacity allows the augmentation pump to provide continuous pulsed liquid flow to assure continuous vapor transport and a continuously operating heat transport system. The check valves are of the ball type to assure maximum reliability. However, any type of check valve can be used, including designs which are preloaded in the closed position. The check valve may use any ball or poppet material which resists corrosion. For optimum performance during testing on Earth, the ball or poppet would have neutral buoyancy or be configured in a closed position when the heat transport system is not operating. The ball may be porous to allow passage of coolant vapor.

  20. Characteristics of turbulence transport for momentum and heat in particle-laden turbulent vertical channel flows

    NASA Astrophysics Data System (ADS)

    Liu, Caixi; Tang, Shuai; Shen, Lian; Dong, Yuhong

    2017-03-01

    The dynamic and thermal performance of particle-laden turbulent flow is investigated via direction numerical simulation combined with the Lagrangian point-particle tracking under the condition of two-way coupling, with a focus on the contributions of particle feedback effect to momentum and heat transfer of turbulence. We take into account the effects of particles on flow drag and Nusselt number and explore the possibility of drag reduction in conjunction with heat transfer enhancement in particle-laden turbulent flows. The effects of particles on momentum and heat transfer are analyzed, and the possibility of drag reduction in conjunction with heat transfer enhancement for the prototypical case of particle-laden turbulent channel flows is addressed. We present results of turbulence modification and heat transfer in turbulent particle-laden channel flow, which shows the heat transfer reduction when large inertial particles with low specific heat capacity are added to the flow. However, we also found an enhancement of the heat transfer and a small reduction of the flow drag when particles with high specific heat capacity are involved. The present results show that particles, which are active agents, interact not only with the velocity field, but also the temperature field and can cause a dissimilarity in momentum and heat transport. This demonstrates that the possibility to increase heat transfer and suppress friction drag can be achieved with addition of particles with different thermal properties.

  1. Transient in-plane thermal transport in nanofilms with internal heating

    PubMed Central

    Cao, Bing-Yang

    2016-01-01

    Wide applications of nanofilms in electronics necessitate an in-depth understanding of nanoscale thermal transport, which significantly deviates from Fourier's law. Great efforts have focused on the effective thermal conductivity under temperature difference, while it is still ambiguous whether the diffusion equation with an effective thermal conductivity can accurately characterize the nanoscale thermal transport with internal heating. In this work, transient in-plane thermal transport in nanofilms with internal heating is studied via Monte Carlo (MC) simulations in comparison to the heat diffusion model and mechanism analyses using Fourier transform. Phonon-boundary scattering leads to larger temperature rise and slower thermal response rate when compared with the heat diffusion model based on Fourier's law. The MC simulations are also compared with the diffusion model with effective thermal conductivity. In the first case of continuous internal heating, the diffusion model with effective thermal conductivity under-predicts the temperature rise by the MC simulations at the initial heating stage, while the deviation between them gradually decreases and vanishes with time. By contrast, for the one-pulse internal heating case, the diffusion model with effective thermal conductivity under-predicts both the peak temperature rise and the cooling rate, so the deviation can always exist. PMID:27118903

  2. Modulated heat pulse propagation and partial transport barriers in chaotic magnetic fields

    NASA Astrophysics Data System (ADS)

    del-Castillo-Negrete, Diego; Blazevski, Daniel

    2016-04-01

    Direct numerical simulations of the time dependent parallel heat transport equation modeling heat pulses driven by power modulation in three-dimensional chaotic magnetic fields are presented. The numerical method is based on the Fourier formulation of a Lagrangian-Green's function method that provides an accurate and efficient technique for the solution of the parallel heat transport equation in the presence of harmonic power modulation. The numerical results presented provide conclusive evidence that even in the absence of magnetic flux surfaces, chaotic magnetic field configurations with intermediate levels of stochasticity exhibit transport barriers to modulated heat pulse propagation. In particular, high-order islands and remnants of destroyed flux surfaces (Cantori) act as partial barriers that slow down or even stop the propagation of heat waves at places where the magnetic field connection length exhibits a strong gradient. Results on modulated heat pulse propagation in fully stochastic fields and across magnetic islands are also presented. In qualitative agreement with recent experiments in large helical device and DIII-D, it is shown that the elliptic (O) and hyperbolic (X) points of magnetic islands have a direct impact on the spatio-temporal dependence of the amplitude of modulated heat pulses.

  3. Analysis for Heat Transfer in a High Current-Passing Carbon Nanosphere Using Nontraditional Thermal Transport Model.

    PubMed

    Hol C Y; Chen, B C; Tsai, Y H; Ma, C; Wen, M Y

    2015-11-01

    This paper investigates the thermal transport in hollow microscale and nanoscale spheres subject to electrical heat source using nontraditional thermal transport model. Working as supercapacitor electrodes, carbon hollow micrometer- and nanometer-sized spheres needs excellent heat transfer characteristics to maintain high specific capacitance, long cycle life, and high power density. In the nanoscale regime, the prediction of heat transfer from the traditional heat conduction equation based on Fourier's law deviates from the measured data. Consequently, the electrical heat source-induced heat transfer characteristics in hollow micrometer- and nanometer-sized spheres are studied using nontraditional thermal transport model. The effects of parameters on heat transfer in the hollow micrometer- and nanometer-sized spheres are discussed in this study. The results reveal that the heat transferred into the spherical interior, temperature and heat flux in the hollow sphere decrease with the increasing Knudsen number when the radius of sphere is comparable to the mean free path of heat carriers.

  4. Modeling electron heat transport during magnetic field buildup in SSPX

    SciTech Connect

    Hua, D.D.; Hooper, E.B.; Fowler, T.K.

    1997-10-01

    A model for spheromak magnetic field buildup and electron thermal transport, including a thermal diffusivity associated with magnetic turbulence during helicity injection is applied to a SSPX equilibrium, with a maximum final magnetic field of 1.3 T. Magnetic field-buildup times of 1.0 X 10-3, 5.0 X 10-4 and 1.0 X 10-4 s were used in the model to examine their effects on electron thermal transport. It is found that at transport run time of 4 x 10-3 s, the fastest buildup-time results in the highest final temperature profile, with a core temperature of 0.93 kev while requiring the lowest input energy at 140 KJ. The results show that within the model the most rapid buildup rate generates the highest electron temperature at the fastest rate and at the lowest consumption of energy. However, the peak power requirements are large (> 600 MW for the fastest buildup case examined).

  5. The effects of increasing humidity on heat transport by extratropical waves

    NASA Astrophysics Data System (ADS)

    Geen, Ruth; Czaja, Arnaud; Haigh, Joanna D.

    2016-08-01

    This study emphasizes the separate contributions of the warm and cold sectors of extratropical cyclones to poleward heat transport. Aquaplanet simulations are performed with an intermediate complexity climate model in which the response of the atmosphere to a range of values of saturation vapor pressure is assessed. These simulations reveal stronger poleward transport of latent heat in the warm sector as saturation vapor pressure is increased and an unexpected increase in poleward sensible heat transport in the cold sector. The latter results nearly equally from changes in the background stability of the atmosphere at low levels and changes in the temporal correlation between wind and temperature fields throughout the troposphere. Increased stability at low level reduces the likelihood that movement of cooler air over warmer water results in an absolutely unstable temperature profile, leading to less asymmetric damping of temperature and meridional velocity anomalies in cold and warm sectors.

  6. Dynamical transition of heat transport in a physical gel near the sol-gel transition

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kazuya U.; Oikawa, Noriko; Kurita, Rei

    2015-12-01

    We experimentally study heat transport in a gelatin solution near a reversible sol-gel transition point where viscosity strongly depends on temperature. We visualize the temperature field and velocity field using thermochromic liquid crystals and polystyrene latex particles, respectively. During the initial stages of heating, we find that heat transport undergoes a dynamical transition from conductive to convective. Subsequently, during later stages, we observe that the transport dynamics are much more complex than conventional thermal convections. At the sample’s surface we observe the formation of stagnant domains, which lack fluid flow. Their formation is not due to the effects of local cooling. We determine that it is the dynamics of these stagnant domains that induce convective-conductive-convective transitions.

  7. Dynamical transition of heat transport in a physical gel near the sol-gel transition

    PubMed Central

    Kobayashi, Kazuya U.; Oikawa, Noriko; Kurita, Rei

    2015-01-01

    We experimentally study heat transport in a gelatin solution near a reversible sol-gel transition point where viscosity strongly depends on temperature. We visualize the temperature field and velocity field using thermochromic liquid crystals and polystyrene latex particles, respectively. During the initial stages of heating, we find that heat transport undergoes a dynamical transition from conductive to convective. Subsequently, during later stages, we observe that the transport dynamics are much more complex than conventional thermal convections. At the sample’s surface we observe the formation of stagnant domains, which lack fluid flow. Their formation is not due to the effects of local cooling. We determine that it is the dynamics of these stagnant domains that induce convective-conductive-convective transitions. PMID:26690696

  8. Constraints on oceanic meridional heat transport from combined measurements of oxygen and carbon

    NASA Astrophysics Data System (ADS)

    Resplandy, L.; Keeling, R. F.; Stephens, B. B.; Bent, J. D.; Jacobson, A.; Rödenbeck, C.; Khatiwala, S.

    2016-11-01

    Despite its importance to the climate system, the ocean meridional heat transport is still poorly quantified. We identify a strong link between the northern hemisphere deficit in atmospheric potential oxygen (APO = O_2 + 1.1 × CO_2) and the asymmetry in meridional heat transport between northern and southern hemispheres. The recent aircraft observations from the HIPPO campaign reveal a northern APO deficit in the tropospheric column of -10.4 ± 1.0 per meg, double the value at the surface and more representative of large-scale air-sea fluxes. The global northward ocean heat transport asymmetry necessary to explain the observed APO deficit is about 0.7-1.1 PW, which corresponds to the upper range of estimates from hydrographic sections and atmospheric reanalyses.

  9. Nanoscale heat transport via electrons and phonons by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Lin, Keng-Hua

    Nanoscale heat transport has become a crucial research topic due to the growing importance of nanotechnology for manufacturing, energy conversion, medicine and electronics. Thermal transport properties at the nanoscale are distinct from the macroscopic ones since the sizes of nanoscale features, such as free surfaces and interfaces, are comparable to the wavelengths and mean free paths of the heat carriers (electrons and phonons), and lead to changes in thermal transport properties. Therefore, understanding how the nanoscale features and energy exchange between the heat carriers affect thermal transport characteristics are the goals of this research. Molecular dynamics (MD) is applied in this research to understand the details of nanoscale heat transport. The advantage of MD is that the size effect, anharmonicity, atomistic structure, and non-equilibrium behavior of the system can all be captured since the dynamics of atoms are described explicitly in MD. However, MD neglects the thermal role of electrons and therefore it is unable to describe heat transport in metal or metal-semiconductor systems accurately. To address this limitation of MD, we develop a method to simulate electronic heat transport by implementing electronic degrees of freedom to MD. In this research, nanoscale heat transport in semiconductor, metal, and metal-semiconductor systems is studied. Size effects on phonon thermal transport in SiGe superlattice thin films and nanowires are studied by MD. We find that, opposite to the macroscopic trend, superlattice thin films can achieve lower thermal conductivity than nanowires at small scales due to the change of phonon nature caused by adjusting the superlattice periodic length and specimen length. Effects of size and electron-phonon coupling rate on thermal conductivity and thermal interface resistivity in Al and model metal-semiconductor systems are studied by MD with electronic degrees of freedom. The results show that increasing the specimen

  10. Unified model of tectonics and heat transport in a frigid Enceladus

    PubMed Central

    Gioia, Gustavo; Chakraborty, Pinaki; Marshak, Stephen; Kieffer, Susan W.

    2007-01-01

    Recent data from the Cassini spacecraft have revealed that Enceladus, the 500-km-diameter moon of Saturn, has a southern hemisphere with a distinct arrangement of tectonic features, intense heat flux, and geyser-like plumes. How did the tectonic features form? How is the heat transported from depth? To address these questions, we formulate a simple model that couples the mechanics and thermodynamics of Enceladus and gives a unified explanation of the salient tectonic features, the plumes, and the transport of heat from a source at a depth of tens of kilometers to the surface. Our findings imply that tiny, icy moons can develop complex surficial geomorphologies, high heat fluxes, and geyser-like activity even if they do not have hot, liquid, and/or convecting interiors. PMID:17699628

  11. Unified model of tectonics and heat transport in a frigid Enceladus.

    PubMed

    Gioia, Gustavo; Chakraborty, Pinaki; Marshak, Stephen; Kieffer, Susan W

    2007-08-21

    Recent data from the Cassini spacecraft have revealed that Enceladus, the 500-km-diameter moon of Saturn, has a southern hemisphere with a distinct arrangement of tectonic features, intense heat flux, and geyser-like plumes. How did the tectonic features form? How is the heat transported from depth? To address these questions, we formulate a simple model that couples the mechanics and thermodynamics of Enceladus and gives a unified explanation of the salient tectonic features, the plumes, and the transport of heat from a source at a depth of tens of kilometers to the surface. Our findings imply that tiny, icy moons can develop complex surficial geomorphologies, high heat fluxes, and geyser-like activity even if they do not have hot, liquid, and/or convecting interiors.

  12. Evaluating MT3DMS for heat transport simulation of closed geothermal systems.

    PubMed

    Hecht-Méndez, Jozsef; Molina-Giraldo, Nelson; Blum, Philipp; Bayer, Peter

    2010-01-01

    Owing to the mathematical similarities between heat and mass transport, the multi-species transport model MT3DMS should be able to simulate heat transport if the effects of buoyancy and changes in viscosity are small. Although in several studies solute models have been successfully applied to simulate heat transport, these studies failed to provide any rigorous test of this approach. In the current study, we carefully evaluate simulations of a single borehole ground source heat pump (GSHP) system in three scenarios: a pure conduction situation, an intermediate case, and a convection-dominated case. Two evaluation approaches are employed: first, MT3DMS heat transport results are compared with analytical solutions. Second, simulations by MT3DMS, which is finite difference, are compared with those by the finite element code FEFLOW and the finite difference code SEAWAT. Both FEFLOW and SEAWAT are designed to simulate heat flow. For each comparison, the computed results are examined based on residual errors. MT3DMS and the analytical solutions compare satisfactorily. MT3DMS and SEAWAT results show very good agreement for all cases. MT3DMS and FEFLOW two-dimensional (2D) and three-dimensional (3D) results show good to very good agreement, except that in 3D there is somewhat deteriorated agreement close to the heat source where the difference in numerical methods is thought to influence the solution. The results suggest that MT3DMS can be successfully applied to simulate GSHP systems, and likely other systems with similar temperature ranges and gradients in saturated porous media.

  13. Solar-energy heats a transportation test center--Pueblo, Colorado

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Petroleum-base, thermal energy transport fluid circulating through 583 square feet of flat-plate solar collectors accumulates majority of energy for space heating and domestic hot-water of large Test Center. Report describes operation, maintenance, and performance of system which is suitable for warehouses and similar buildings. For test period from February 1979 to January 1980, solar-heating fraction was 31 percent, solar hot-water fraction 79 percent.

  14. Estimating the effect of shallow groundwater on diurnal heat transport in a vadose zone

    NASA Astrophysics Data System (ADS)

    Jiang, Jianmei; Zhao, Lin; Zhai, Zhe

    2016-09-01

    The influence of shallow groundwater on the diurnal heat transport of the soil profile was analyzed using a soil sensor automatic monitoring system that continuously measures temperature and water content of soil profiles to simulate heat transport based on the Philip and de Vries (PDV) model. Three experiments were conducted to measure soil properties at depths of 5 cm, 10 cm, 20 cm, and 30 cm when groundwater tables reached 10 cm, 30 cm, and 60 cm (Experiments I, II, and III). Results show that both the soil temperature near shallow groundwater and the soil water content were effectively simulated by the PDV model. The root mean square errors of the temperature at depths of 5 cm, 10 cm, and 20 cm were 1.018°C, 0.909°C, and 0.255°C, respectively. The total heat flux generated the convergent and divergent planes in space-time fields with valley values of-161.5W•m-2 at 7:30 and-234.6W•m-2 at 11:10 in Experiments II and III, respectively. The diurnal heat transport of the saturated soil occurred in five stages, while that of saturated-unsaturated and unsaturated soil profiles occurred in four stages because high moisture content led to high thermal conductivity, which hastened the heat transport.

  15. Heat and mass transport during a groundwater replenishment trial in a highly heterogeneous aquifer

    NASA Astrophysics Data System (ADS)

    Seibert, Simone; Prommer, Henning; Siade, Adam; Harris, Brett; Trefry, Mike; Martin, Michael

    2014-12-01

    Changes in subsurface temperature distribution resulting from the injection of fluids into aquifers may impact physiochemical and microbial processes as well as basin resource management strategies. We have completed a 2 year field trial in a hydrogeologically and geochemically heterogeneous aquifer below Perth, Western Australia in which highly treated wastewater was injected for large-scale groundwater replenishment. During the trial, chloride and temperature data were collected from conventional monitoring wells and by time-lapse temperature logging. We used a joint inversion of these solute tracer and temperature data to parameterize a numerical flow and multispecies transport model and to analyze the solute and heat propagation characteristics that prevailed during the trial. The simulation results illustrate that while solute transport is largely confined to the most permeable lithological units, heat transport was also affected by heat exchange with lithological units that have a much lower hydraulic conductivity. Heat transfer by heat conduction was found to significantly influence the complex temporal and spatial temperature distribution, especially with growing radial distance and in aquifer sequences with a heterogeneous hydraulic conductivity distribution. We attempted to estimate spatially varying thermal transport parameters during the data inversion to illustrate the anticipated correlations of these parameters with lithological heterogeneities, but estimates could not be uniquely determined on the basis of the collected data.

  16. Analytical study of Joule heating effects on electrokinetic transportation in capillary electrophoresis.

    PubMed

    Xuan, Xiangchun; Li, Dongqing

    2005-02-04

    Electric fields are often used to transport fluids (by electroosmosis) and separate charged samples (by electrophoresis) in microfluidic devices. However, there exists inevitable Joule heating when electric currents are passing through electrolyte solutions. Joule heating not only increases the fluid temperature, but also produces temperature gradients in cross-stream and axial directions. These temperature effects make fluid properties non-uniform, and hence alter the applied electric potential field and the flow field. The mass species transport is also influenced. In this paper we develop an analytical model to study Joule heating effects on the transport of heat, electricity, momentum and mass species in capillary-based electrophoresis. Close-form formulae are derived for the temperature, applied electrical potential, velocity, and pressure fields at steady state, and the transient concentration field as well. Also available are the compact formulae for the electric current and the volume flow rate through the capillary. It is shown that, due to the thermal end effect, sharp temperature drops appear close to capillary ends, where sharp rises of electric field are required to meet the current continuity. In order to satisfy the mass continuity, pressure gradients have to be induced along the capillary. The resultant curved fluid velocity profile and the increase of molecular diffusion both contribute to the dispersion of samples. However, Joule heating effects enhance the sample transport velocity, reducing the analysis time in capillary electrophoretic separations.

  17. Heat-driven spin transport in a ferromagnetic metal

    SciTech Connect

    Xu, Yadong; Yang, Bowen; Tang, Chi; Jiang, Zilong; Shi, Jing; Schneider, Michael; Whig, Renu

    2014-12-15

    As a non-magnetic heavy metal is attached to a ferromagnet, a vertically flowing heat-driven spin current is converted to a transverse electric voltage, which is known as the longitudinal spin Seebeck effect (SSE). If the ferromagnet is a metal, this voltage is also accompanied by voltages from two other sources, i.e., the anomalous Nernst effect in both the ferromagnet and the proximity-induced ferromagnetic boundary layer. By properly identifying and carefully separating those different effects, we find that in this pure spin current circuit the additional spin current drawn by the heavy metal generates another significant voltage by the ferromagnetic metal itself which should be present in all relevant experiments.

  18. Momentum and heat transport scalings in laminar vertical convection.

    PubMed

    Shishkina, Olga

    2016-05-01

    We derive the dependence of the Reynolds number Re and the Nusselt number Nu on the Rayleigh number Ra and the Prandtl number Pr in laminar vertical convection (VC), where a fluid is confined between two differently heated isothermal vertical walls. The boundary layer equations in laminar VC yield two limiting scaling regimes: Nu∼Pr^{1/4}Ra^{1/4}, Re∼Pr^{-1/2}Ra^{1/2} for Pr≪1 and Nu∼Pr^{0}Ra^{1/4}, Re∼Pr^{-1}Ra^{1/2} for Pr≫1. These theoretical results are in excellent agreement with direct numerical simulations for Ra from 10^{5} to 10^{10} and Pr from 10^{-2} to 30. The transition between the regimes takes place for Pr around 10^{-1}.

  19. Ballistic heat transport in laser generated nano-bubbles.

    PubMed

    Lombard, Julien; Biben, Thierry; Merabia, Samy

    2016-08-04

    Nanobubbles generated by laser heated plasmonic nanoparticles are of interest for biomedical and energy harvesting applications. Of utmost importance is the maximal size of these transient bubbles. Here, we report hydrodynamic phase field simulations of the dynamics of laser induced nanobubbles, with the aim to understand which physical processes govern their maximal size. We show that the nanobubble maximal size and lifetime are to a large extent controlled by the ballistic thermal flux which is present inside the bubble. Taking into account this thermal flux, we can reproduce the fluence dependence of the maximal nanobubble radius as reported experimentally. We also discuss the influence of the laser pulse duration on the number of nanobubbles generated and their maximal size. These studies represent a significant step toward the optimization of the nanobubble size, which is of crucial importance for photothermal cancer therapy applications.

  20. A predictive transport modeling code for ICRF-heated tokamaks

    SciTech Connect

    Phillips, C.K.; Hwang, D.Q. . Plasma Physics Lab.); Houlberg, W.; Attenberger, S.; Tolliver, J.; Hively, L. )

    1992-02-01

    In this report, a detailed description of the physic included in the WHIST/RAZE package as well as a few illustrative examples of the capabilities of the package will be presented. An in depth analysis of ICRF heating experiments using WHIST/RAZE will be discussed in a forthcoming report. A general overview of philosophy behind the structure of the WHIST/RAZE package, a summary of the features of the WHIST code, and a description of the interface to the RAZE subroutines are presented in section 2 of this report. Details of the physics contained in the RAZE code are examined in section 3. Sample results from the package follow in section 4, with concluding remarks and a discussion of possible improvements to the package discussed in section 5.

  1. Screening for heat transport by groundwater in closed geothermal systems.

    PubMed

    Ferguson, Grant

    2015-01-01

    Heat transfer due to groundwater flow can significantly affect closed geothermal systems. Here, a screening method is developed, based on Peclet numbers for these systems and Darcy's law. Conduction-only conditions should not be expected where specific discharges exceed 10(-8)  m/s. Constraints on hydraulic gradients allow for preliminary screening for advection based on rock or soil types. Identification of materials with very low hydraulic conductivity, such as shale and intact igneous and metamorphic rock, allow for analysis with considering conduction only. Variability in known hydraulic conductivity allows for the possibility of advection in most other rocks and soil types. Further screening relies on refinement of estimates of hydraulic gradients and hydraulic conductivity through site investigations and modeling until the presence or absence of conduction can be confirmed.

  2. Spin current draining effect on heat-driven spin transport

    NASA Astrophysics Data System (ADS)

    Xu, Yadong; Yang, Bowen; Tang, Chi; Jiang, Zilong; Shi, Jing; Schneider, Michael; Whig, Renu

    As a non-magnetic heavy metal is attached to a ferromagnet, a vertically flowing heat-driven spin current is converted to a transverse electric voltage, which is known as the longitudinal spin Seebeck effect. If the ferromagnet is a metal, this voltage is also accompanied by voltages from two other sources, i.e. the anomalous Nernst effect in both the ferromagnet and the proximity-induced ferromagnetic boundary layer. In this work, we have investigated these phenomena in NiFe/Cu/heavy metal multilayer structure. By identifying and carefully separating those effects, we find that in this pure spin current circuit the additional spin current drawn by the heavy metal generates another voltage in the ferromagnetic metal via the inverse spin Hall effect. The research was supported by the DOE BES Award #DE-FG02-07ER46351 and DARPA/DMEA under H94003-10-2-1004.

  3. Anisotropic heat transport in integrable and chaotic 3-D magnetic fields

    SciTech Connect

    Del-Castillo-Negrete, Diego B; Blazevski, D.; Chacon, Luis

    2012-01-01

    A study of anisotropic heat transport in 3-D chaotic magnetic fields is presented. The approach is based on the recently proposed Lagrangian-Green s function (LG) method in Ref. [1] that allows an efficient and accurate integration of the parallel transport equation applicable to general magnetic fields with local or non-local parallel flux closures. We focus on reversed shear magnetic field configurations known to exhibit separatrix reconnection and shearless transport barriers. The role of reconnection and magnetic field line chaos on temperature transport is studied. Numerical results are presented on the anomalous relaxation of radial temperature gradients in the presence of shearless Cantori partial barri- ers. Also, numerical evidence of non-local effective radial temperature transport in chaotic fields is presented. Going beyond purely parallel transport, the LG method is generalized to include finite perpendicular diffusivity, and the problem of temperature flattening inside a magnetic island is studied.

  4. Ballistic heat transport in laser generated nano-bubbles

    NASA Astrophysics Data System (ADS)

    Lombard, Julien; Biben, Thierry; Merabia, Samy

    2016-08-01

    Nanobubbles generated by laser heated plasmonic nanoparticles are of interest for biomedical and energy harvesting applications. Of utmost importance is the maximal size of these transient bubbles. Here, we report hydrodynamic phase field simulations of the dynamics of laser induced nanobubbles, with the aim to understand which physical processes govern their maximal size. We show that the nanobubble maximal size and lifetime are to a large extent controlled by the ballistic thermal flux which is present inside the bubble. Taking into account this thermal flux, we can reproduce the fluence dependence of the maximal nanobubble radius as reported experimentally. We also discuss the influence of the laser pulse duration on the number of nanobubbles generated and their maximal size. These studies represent a significant step toward the optimization of the nanobubble size, which is of crucial importance for photothermal cancer therapy applications.Nanobubbles generated by laser heated plasmonic nanoparticles are of interest for biomedical and energy harvesting applications. Of utmost importance is the maximal size of these transient bubbles. Here, we report hydrodynamic phase field simulations of the dynamics of laser induced nanobubbles, with the aim to understand which physical processes govern their maximal size. We show that the nanobubble maximal size and lifetime are to a large extent controlled by the ballistic thermal flux which is present inside the bubble. Taking into account this thermal flux, we can reproduce the fluence dependence of the maximal nanobubble radius as reported experimentally. We also discuss the influence of the laser pulse duration on the number of nanobubbles generated and their maximal size. These studies represent a significant step toward the optimization of the nanobubble size, which is of crucial importance for photothermal cancer therapy applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR02144A

  5. Optimization of creep properties of welded header-stub tube connection for lif extension

    SciTech Connect

    Ram, R.; Cunningham, G.; Roberts, B.

    1996-12-31

    The failure of boiler tubes is the predominant cause of boiler outages. From a life-extension point of view, the critical components are large diameter thick-wall high-temperature headers. The primary aim of this research is to numerically analyze the stresses in the boiler tube-header weld connection and study the behavior of the material as it creeps. The focus is on the initial thermoelastic stresses at the beginning of operation and the distribution of stresses after approximately twenty years of operation when the stresses have relaxed. The study calculates creep life fractions of the assembly after twenty years of service.

  6. Investigation of heat and momentum transport in turbulent flows via numerical simulations

    NASA Technical Reports Server (NTRS)

    Kim, John

    1988-01-01

    Turbulent transport of heat is studied by examining the flow fields obtained from a direct simulation of a turbulent channel flow. The turbulence structures associated with the velocity and scalar fields are presented using air (Pr = 0.71) as the medium. A comparison is made between the wall-layer structures identified by the temperature field and the structures found in the velocity field. Consideration is also given to the role of the organized turbulence structures in scalar transport.

  7. Modification of the finite element heat and mass transfer code (FEHM) to model multicomponent reactive transport

    SciTech Connect

    Viswanathan, H.S.

    1996-08-01

    The finite element code FEHMN, developed by scientists at Los Alamos National Laboratory (LANL), is a three-dimensional finite element heat and mass transport simulator that can handle complex stratigraphy and nonlinear processes such as vadose zone flow, heat flow and solute transport. Scientists at LANL have been developing hydrologic flow and transport models of the Yucca Mountain site using FEHMN. Previous FEHMN simulations have used an equivalent Kd model to model solute transport. In this thesis, FEHMN is modified making it possible to simulate the transport of a species with a rigorous chemical model. Including the rigorous chemical equations into FEHMN simulations should provide for more representative transport models for highly reactive chemical species. A fully kinetic formulation is chosen for the FEHMN reactive transport model. Several methods are available to computationally implement a fully kinetic formulation. Different numerical algorithms are investigated in order to optimize computational efficiency and memory requirements of the reactive transport model. The best algorithm of those investigated is then incorporated into FEHMN. The algorithm chosen requires for the user to place strongly coupled species into groups which are then solved for simultaneously using FEHMN. The complete reactive transport model is verified over a wide variety of problems and is shown to be working properly. The new chemical capabilities of FEHMN are illustrated by using Los Alamos National Laboratory`s site scale model of Yucca Mountain to model two-dimensional, vadose zone {sup 14}C transport. The simulations demonstrate that gas flow and carbonate chemistry can significantly affect {sup 14}C transport at Yucca Mountain. The simulations also prove that the new capabilities of FEHMN can be used to refine and buttress already existing Yucca Mountain radionuclide transport studies.

  8. An alternative treatment of heat flow for charge transport in semiconductor devices

    SciTech Connect

    Grupen, Matt

    2009-12-15

    A unique thermodynamic model of Fermi gases suitable for semiconductor device simulation is presented. Like other models, such as drift diffusion and hydrodynamics, it employs moments of the Boltzmann transport equation derived using the Fermi-Dirac distribution function. However, unlike other approaches, it replaces the concept of an electron thermal conductivity with the heat capacity of an ideal Fermi gas to determine heat flow. The model is used to simulate a field-effect transistor and show that the external current-voltage characteristics are strong functions of the state space available to the heated Fermi distribution.

  9. Local momentum and heat fluxes in transient transport processes and inhomogeneous systems.

    PubMed

    Chen, Youping; Diaz, Adrian

    2016-11-01

    This work examines existing formalisms for the derivation of microscopic momentum and heat fluxes. Both analytical and simulation results are provided to show that the widely used flux formulas are not applicable to transient transport processes or highly inhomogeneous systems, e.g., materials with atomically sharp interfaces. A method is formulated for formally deriving microscopic momentum and heat fluxes through the integral representation of conservation laws. The resulting flux formulas are mathematically rigorous, fully consistent with the physical concepts of momentum and heat fluxes, and applicable to nonequilibrium transient processes in atomically inhomogeneous systems with general many-body forces.

  10. Local momentum and heat fluxes in transient transport processes and inhomogeneous systems

    NASA Astrophysics Data System (ADS)

    Chen, Youping; Diaz, Adrian

    2016-11-01

    This work examines existing formalisms for the derivation of microscopic momentum and heat fluxes. Both analytical and simulation results are provided to show that the widely used flux formulas are not applicable to transient transport processes or highly inhomogeneous systems, e.g., materials with atomically sharp interfaces. A method is formulated for formally deriving microscopic momentum and heat fluxes through the integral representation of conservation laws. The resulting flux formulas are mathematically rigorous, fully consistent with the physical concepts of momentum and heat fluxes, and applicable to nonequilibrium transient processes in atomically inhomogeneous systems with general many-body forces.

  11. Transport of volume, heat, and salt towards the Arctic in the Faroe Current 1993-2013

    NASA Astrophysics Data System (ADS)

    Hansen, B.; Larsen, K. M. H.; Hátún, H.; Kristiansen, R.; Mortensen, E.; Østerhus, S.

    2015-09-01

    The flow of warm and saline water from the Atlantic Ocean, across the Greenland-Scotland Ridge, into the Nordic Seas - the Atlantic inflow - is split into three separate branches. The most intense of these branches is the inflow between Iceland and the Faroe Islands (Faroes), which is focused into the Faroe Current, north of the Faroes. The Atlantic inflow is an integral part of the North Atlantic thermohaline circulation (THC), which is projected to weaken during the 21st century and might conceivably reduce the oceanic heat and salt transports towards the Arctic. Since the mid-1990s, hydrographic properties and current velocities of the Faroe Current have been monitored along a section extending north from the Faroe shelf. From these in situ observations, time series of volume, heat, and salt transport have previously been reported, but the high variability of the transport has made it difficult to establish whether there are trends. Here, we present results from a new analysis of the Faroe Current where the in situ observations have been combined with satellite altimetry. For the period 1993 to 2013, we find the average volume transport of Atlantic water in the Faroe Current to be 3.8 ± 0.5 Sv (1 Sv = 106 m3 s-1) with a heat transport relative to 0 °C of 124 ± 15 TW (1 TW = 1012 W). Consistent with other results for the Northeast Atlantic component of the THC, we find no indication of weakening. The transports of the Faroe Current, on the contrary, increased. The overall increase over the 2 decades of observation was 9 ± 8 % for volume transport and 18 ± 9 % for heat transport (95 % confidence intervals). During the same period, the salt transport relative to the salinity of the deep Faroe Bank Channel overflow (34.93) more than doubled, potentially strengthening the feedback on thermohaline intensity. The increased heat and salt transports are partly caused by the increased volume transport and partly by increased temperatures and salinities of the

  12. The role of individual cyclones for atmospheric latent and sensible heat transport into the European Arctic

    NASA Astrophysics Data System (ADS)

    Sodemann, H.; Stohl, A.

    2010-12-01

    The bulk of the atmospheric latent heat transport induced by extratropical cyclones is organized in the warm conveyor belt, also known as atmospheric rivers. In order to enhance the process understanding of atmospheric sensible and latent heat transport with these structures into the European Arctic, the magnitude and variability of the energy flux from individual cyclones in this region was studied. We applied a moisture source tracking algorithm embedded in the limited-area numerical weather prediction model (NWP) Climate High-Resolution Model (CHRM) to trace the evaporation sources and transport of water vapour from different latitude bands of the North Atlantic Ocean. September 2002 and December 2006 were chosen as initial analysis periods, since a particularly large number of cyclones (including former hurricanes) traveled within the North Atlantic storm track during these months. The main findings are that latent heat (LH) from more southerly source regions is transported at higher altitudes. Stronger storms draw latent heat from a larger area (further south), and the ensuing precipitation will hence on average originate from further south as well. Most long-range transport of LH occurs in the cold frontal bands. Individual cyclones are the main source of sub-monthly LH flux variability, and can cause up to 4-sigma variation of the mean flux. LH flux is almost permanently net positive (northward), unlike for sensible heat (SH) and other energy fluxes. Most LH that is "permanently" transferred to north of 60°N in the Atlantic storm track originates from directly south of that latitude, implying on average short atmospheric moisture lifetimes, and hence a fast energy turnover. We compare these findings to results from a Lagrangian moisture tracking method based on the FLEXPART model. Remarks with regard to differences in the transport conditions of latent head in such structures along the North American West Coast and the Norwegian West Coast will be made.

  13. A conceptual model of oceanic heat transport in the Snowball Earth scenario

    NASA Astrophysics Data System (ADS)

    Comeau, Darin; Kurtze, Douglas A.; Restrepo, Juan M.

    2016-12-01

    Geologic evidence suggests that the Earth may have been completely covered in ice in the distant past, a state known as Snowball Earth. This is still the subject of controversy, and has been the focus of modeling work from low-dimensional models up to state-of-the-art general circulation models. In our present global climate, the ocean plays a large role in redistributing heat from the equatorial regions to high latitudes, and as an important part of the global heat budget, its role in the initiation a Snowball Earth, and the subsequent climate, is of great interest. To better understand the role of oceanic heat transport in the initiation of Snowball Earth, and the resulting global ice covered climate state, the goal of this inquiry is twofold: we wish to propose the least complex model that can capture the Snowball Earth scenario as well as the present-day climate with partial ice cover, and we want to determine the relative importance of oceanic heat transport. To do this, we develop a simple model, incorporating thermohaline dynamics from traditional box ocean models, a radiative balance from energy balance models, and the more contemporary "sea glacier" model to account for viscous flow effects of extremely thick sea ice. The resulting model, consisting of dynamic ocean and ice components, is able to reproduce both Snowball Earth and present-day conditions through reasonable changes in forcing parameters. We find that including or neglecting oceanic heat transport may lead to vastly different global climate states, and also that the parameterization of under-ice heat transfer in the ice-ocean coupling plays a key role in the resulting global climate state, demonstrating the regulatory effect of dynamic ocean heat transport.

  14. A low-frequency wave motion mechanism enables efficient energy transport in carbon nanotubes at high heat fluxes.

    PubMed

    Zhang, Xiaoliang; Hu, Ming; Poulikakos, Dimos

    2012-07-11

    The great majority of investigations of thermal transport in carbon nanotubes (CNTs) in the open literature focus on low heat fluxes, that is, in the regime of validity of the Fourier heat conduction law. In this paper, by performing nonequilibrium molecular dynamics simulations we investigated thermal transport in a single-walled CNT bridging two Si slabs under constant high heat flux. An anomalous wave-like kinetic energy profile was observed, and a previously unexplored, wave-dominated energy transport mechanism is identified for high heat fluxes in CNTs, originated from excited low frequency transverse acoustic waves. The transported energy, in terms of a one-dimensional low frequency mechanical wave, is quantified as a function of the total heat flux applied and is compared to the energy transported by traditional Fourier heat conduction. The results show that the low frequency wave actually overtakes traditional Fourier heat conduction and efficiently transports the energy at high heat flux. Our findings reveal an important new mechanism for high heat flux energy transport in low-dimensional nanostructures, such as one-dimensional (1-D) nanotubes and nanowires, which could be very relevant to high heat flux dissipation such as in micro/nanoelectronics applications.

  15. Direct estimate of water, heat, and salt transport through the Strait of Otranto

    NASA Astrophysics Data System (ADS)

    Yari, Sadegh; Kovačević, Vedrana; Cardin, Vanessa; Gačić, Miroslav; Bryden, Harry L.

    2012-09-01

    The transport of water volume, salt and heat was calculated using continuous measurements of currents in the Otranto Strait for a one-year period in 1994-95. Temperature and salinity data sets, available from five hydrographic surveys, were used to obtain the seasonal temperature and salinity distributions at the Otranto transect. The Variational Inverse Method (VIM) was applied to reconstruct spatial distributions of the de-tided low-pass inflowing current component, salinity and temperature. Errors associated with estimates of transports are influenced by the data coverage: the higher the spatial resolution, the smaller the error and vice versa. Volume transport reaches a maximum in winter and spring and attains its minimum in summer. The obtained volume transport [˜1 Sv (106 m3s-1)] should be considered a lower limit value since in that period the Adriatic was producing relatively small quantities of deep water due to the inflow of low-salinity (high buoyancy) waters and relatively mild winters. Comparing the mean advective heat input and the air-sea heat loss, the same order of magnitude between the two has been obtained which is satisfactory considering the possible errors of the two approaches. The relative importance of the eddy heat transport to the total transport is estimated to be only about 5% and thus it can be neglected in a first approximation. The salt transport estimates show a net input, suggesting a salinity increase during the period of study; this was confirmed from the long-term salinity data in the Southern Adriatic.

  16. Micropaleontological evidence for increased meridional heat transport in the North Atlantic Ocean during the pliocene

    USGS Publications Warehouse

    Dowsett, H.J.; Cronin, T. M.; Poore, R.Z.; Thompson, R.S.; Whatley, R.C.; Wood, A.M.

    1992-01-01

    The Middle Pliocene (???3 million years ago) has been identified as the last time the Earth was significantly warmer than it was during the Last Interglacial and Holocene. A quantitative micropaleontological paleotemperature transect from equator to high latitudes in the North Atlantic indicates that Middle Pliocene warmth involved increased meridional oceanic heat transport.

  17. Mass and heat transport in the two-phase Buckley-Leverett model

    NASA Astrophysics Data System (ADS)

    Akhmetzyanov, Atlas V.; Kushner, Alexei G.; Lychagin, Valentin V.

    2017-03-01

    In this article we study the initial boundary value problem for two-phase heat and mass transport in porous media described by the Buckley-Leverett model. We outline a method to construct asymptotic solutions of the initial boundary problem and show how to overcome singularities in solutions and shock waves.

  18. Measurements of Combined Axial Mass and Heat Transport in He II.

    ERIC Educational Resources Information Center

    Johnson, Warren W.; Jones, Michael C.

    An experiment was performed that allowed measurements of both axial mass and heat transport of He-II (the superfluid phase of helium 4) in a long tube. The apparatus allowed the pressure difference and the temperature difference across the flow tube to each be independently adjusted, and the resulting steady-state values of net fluid velocity and…

  19. 3D Numerical Simulation of Turbulent Buoyant Flow and Heat Transport in a Curved Open Channel

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A three-dimensional buoyancy-extended version of kappa-epsilon turbulence model was developed for simulating the turbulent flow and heat transport in a curved open channel. The density- induced buoyant force was included in the model, and the influence of temperature stratification on flow field was...

  20. Competing orders in LSCO probed by heat transport

    NASA Astrophysics Data System (ADS)

    Li, Shiyan; Hawthorn, D. G.; Taillefer, Louis; Yamada, K.

    2006-03-01

    We elucidate the nature of the thermal metal-to-insulator transition in La2-xSrxCuO4 (LSCO) [1] through measurements of the thermal conductivity κ performed very close to the transition, down to temperatures as low as 50 mK and in magnetic fields H up to 17 T. For a single crystal with x = 0.15, a monotonic increase in the residual linear term κ0/T is observed up to 17 T, as expected for a d-wave superconductor. For a crystal with x = 0.144, however, we observe an initial increase in κ0/T at low field, followed by a decrease when H exceeds a critical field H^*. This result is consistent with recent neutron scattering measurements on a similar sample [2], which show that static spin-density-wave (SDW) order is not present in zero field, but sets in at a critical magnetic field H^*, and then co-exists/competes with superconductivity (SC) for H > H^*. Taken together, these two measurements reveal that the SC phase gives way to a phase which is both magnetic and insulating, whether by increasing magnetic field or by decreasing doping. Using low-energy quasiparticle transport, we map out the T = 0 field-doping (H-x) phase diagram of LSCO. [1] D.G. Hawthorn et al., Phys. Rev. Lett. 90, 197004 (2003); X.F. Sun et al., Phys. Rev. Lett. 90, 117004 (2003). [2] B. Khaykovich et al., Phys. Rev. B 71, 220508(R) (2005).

  1. Dissolved gas exsolution to enhance gas production and transport during bench-scale electrical resistance heating

    NASA Astrophysics Data System (ADS)

    Hegele, P. R.; Mumford, K. G.

    2015-05-01

    Condensation of volatile organic compounds in colder zones can be detrimental to the performance of an in situ thermal treatment application for the remediation of chlorinated solvent source zones. A novel method to increase gas production and limit convective heat loss in more permeable, potentially colder, zones involves the injection and liberation of dissolved gas from solution during heating. Bench-scale electrical resistance heating experiments were performed with a dissolved carbon dioxide and sodium chloride solution to investigate exsolved gas saturations and transport regimes at elevated, but sub-boiling, temperatures. At sub-boiling temperatures, maximum exsolved gas saturations of Sg = 0.12 were attained, and could be sustained when the carbon dioxide solution was injected during heating rather than emplaced prior to heating. This gas saturation was estimated to decrease groundwater relative permeability to krw = 0.64. Discontinuous gas transport was observed above saturations of Sg = 0.07, demonstrating the potential of exsolved CO2 to bridge vertical gas transport through colder zones.

  2. Performance and heat transfer characteristics of the laser-heated rocket - A future space transportation system

    NASA Technical Reports Server (NTRS)

    Shoji, J. M.; Larson, V. R.

    1976-01-01

    The application of advanced liquid-bipropellant rocket engine analysis techniques has been utilized for prediction of the potential delivered performance and the design of thruster wall cooling schemes for laser-heated rocket thrusters. Delivered specific impulse values greater than 1000 lbf-sec/lbm are potentially achievable based on calculations for thrusters designed for 10-kW and 5000-kW laser beam power levels. A thruster wall-cooling technique utilizing a combination of regenerative cooling and a carbon-seeded hydrogen boundary layer is presented. The flowing carbon-seeded hydrogen boundary layer provides radiation absorption of the heat radiated from the high-temperature plasma. Also described is a forced convection thruster wall cooling design for an experimental test thruster.

  3. Role of the magnetic island and low- k turbulence on radial electron heat transport

    NASA Astrophysics Data System (ADS)

    Choi, M. J.; Park, H. K.; in, Y.; Ko, S. H.; Kim, H. S.; Bae, C.; Kwon, J. M.; Lee, W.; Lee, K. D.; Lee, H. H.; Ko, W. H.; Lee, S. H.; Lee, J. H.; Ko, J.; Kim, J.; Woo, M. H.; Jeong, M.; Park, B. H.; Yun, G. S.; Lee, J.; Kim, M.; Luhmann, N. C., Jr.

    2016-10-01

    Magnetic islands can enhance or reduce the radial transport either by reconnecting field lines or producing the poloidal flow shear across the rational surface. Both cases have been observed in the KSTAR L-mode plasmas. In the first case, the temperature inside the q = 2 surface decreases severely ( 25%) with the enhanced transport by the rotating m / n = 2 / 1 magnetic island. However, in the case where the 2/1 magnetic island is driven and locked by the n = 1 resonant magnetic perturbation, the transport is reduced and the electron temperature (Te) gradient is increased across the island with a clear poloidal flow shear. The poloidal flow shear has been identified utilizing electron cyclotron emission imaging (ECEI) measurements of the low-k turbulent Te fluctuations driven by the increased Te gradient. In addition, the interaction between the Te turbulence and magnetic island causes the transient heat transport events and affects the transport characteristics near the q = 2 region.

  4. The role of atmospheric heat transport and regional feedbacks in the Arctic warming at equilibrium

    NASA Astrophysics Data System (ADS)

    Yoshimori, Masakazu; Abe-Ouchi, Ayako; Laîné, Alexandre

    2017-01-01

    It is well known that the Arctic warms much more than the rest of the world even under spatially quasi-uniform radiative forcing such as that due to an increase in atmospheric CO2 concentration. While the surface albedo feedback is often referred to as the explanation of the enhanced Arctic warming, the importance of atmospheric heat transport from the lower latitudes has also been reported in previous studies. In the current study, an attempt is made to understand how the regional feedbacks in the Arctic are induced by the change in atmospheric heat transport and vice versa. Equilibrium sensitivity experiments that enable us to separate the contributions of the Northern Hemisphere mid-high latitude response to the CO2 increase and the remote influence of surface warming in other regions are carried out. The result shows that the effect of remote forcing is predominant in the Arctic warming. The dry-static energy transport to the Arctic is reduced once the Arctic surface warms in response to the local or remote forcing. The feedback analysis based on the energy budget reveals that the increased moisture transport from lower latitudes, on the other hand, warms the Arctic in winter more effectively not only via latent heat release but also via greenhouse effect of water vapor and clouds. The change in total atmospheric heat transport determined as a result of counteracting dry-static and latent heat components, therefore, is not a reliable measure for the net effect of atmospheric dynamics on the Arctic warming. The current numerical experiments support a recent interpretation based on the regression analysis: the concurrent reduction in the atmospheric poleward heat transport and future Arctic warming predicted in some models does not imply a minor role of the atmospheric dynamics. Despite the similar magnitude of poleward heat transport change, the Arctic warms more than the Southern Ocean even in the equilibrium response without ocean dynamics. It is shown that a

  5. Decadal variation of the North Atlantic meridional heat transport and its relation to atmospheric processes

    NASA Astrophysics Data System (ADS)

    Martin, T.; Ruprecht, E.

    2007-02-01

    The effects of the meridional heat transport in the North Atlantic Ocean (HTR) on the north hemispheric climate are studied using the results of the coupled model ECHAM5/MPI-OM. Significant correlations exist between HTR and atmospheric processes over the Nordic Seas and the Eurasian continent only for low (periods longer than 40 years) and intermediate frequency variations (periods between 25 and 40 years). A positive HTR anomaly at 30°N is highly correlated with turbulent heat fluxes around 50°N. The transport through 70°N is directly related to the fluxes over the Nordic seas. From the correlation pattern with the atmospheric surface temperature and pressure one can conclude that the heat anomalies propagate along the cyclone tracks towards northeast over the Eurasian continent. The HRT anomalies are negatively correlated with the pressure over the Nordic seas and with the winter time anticyclone intensity over Siberia.

  6. Heat transport in the quasi-single-helicity islands of EXTRAP T2R

    NASA Astrophysics Data System (ADS)

    Frassinetti, L.; Brunsell, P. R.; Drake, J.

    2009-03-01

    The heat transport inside the magnetic island generated in a quasi-single-helicity regime of a reversed-field pinch device is studied by using a numerical code that simulates the electron temperature and the soft x-ray emissivity. The heat diffusivity χe inside the island is determined by matching the simulated signals with the experimental ones. Inside the island, χe turns out to be from one to two orders of magnitude lower than the diffusivity in the surrounding plasma, where the magnetic field is stochastic. Furthermore, the heat transport properties inside the island are studied in correlation with the plasma current and with the amplitude of the magnetic fluctuations.

  7. [The design of heat dissipation of the field low temperature box for storage and transportation].

    PubMed

    Wei, Jiancang; Suin, Jianjun; Wu, Jian

    2013-02-01

    Because of the compact structure of the field low temperature box for storage and transportation, which is due to the same small space where the compressor, the condenser, the control circuit, the battery and the power supply device are all placed in, the design for heat dissipation and ventilation is of critical importance for the stability and reliability of the box. Several design schemes of the heat dissipation design of the box were simulated using the FLOEFD hot fluid analysis software in this study. Different distributions of the temperature field in every design scheme were constructed intimately in the present study. It is well concluded that according to the result of the simulation analysis, the optimal heat dissipation design is decent for the field low temperature box for storage and transportation, and the box can operate smoothly for a long time using the results of the design.

  8. Qualifying the use of RIS data for patient dose by comparison with DICOM header data.

    PubMed

    Wilde, R; Charnock, P; McDonald, S; Moores, B M

    2011-09-01

    A system was developed in 2008 to calculate patient doses using Radiology Information System (RIS) data and presents these data as a patient dose audit. One of the issues with this system was the quality of user-entered data. It has been shown that Digital Imaging and Communication in Medicine (DICOM) header data can be used to perform dose audits with a high level of data accuracy. This study aims to show that using RIS data for dose audits is not only a viable alternative to using DICOM header data, but that it has advantages. A new system was developed to pull header data from DICOM images easily and was installed on a workstation within a hospital department. Data were recovered for a common set of examinations using both RIS and DICOM header data. The data were compared on a result-by-result basis to check for consistency of common fields between RIS and DICOM, as well as assessing the value of data fields uncommon to both systems. The study shows that whilst RIS is not as accurate as DICOM, it does provide enough accurate data and that it has other advantages over using a DICOM approach. These results suggest that a 'best of both worlds' may be achievable using Modality Performed Procedure Step (MPPS).

  9. Providing integrity, authenticity, and confidentiality for header and pixel data of DICOM images.

    PubMed

    Al-Haj, Ali

    2015-04-01

    Exchange of medical images over public networks is subjected to different types of security threats. This has triggered persisting demands for secured telemedicine implementations that will provide confidentiality, authenticity, and integrity for the transmitted images. The medical image exchange standard (DICOM) offers mechanisms to provide confidentiality for the header data of the image but not for the pixel data. On the other hand, it offers mechanisms to achieve authenticity and integrity for the pixel data but not for the header data. In this paper, we propose a crypto-based algorithm that provides confidentially, authenticity, and integrity for the pixel data, as well as for the header data. This is achieved by applying strong cryptographic primitives utilizing internally generated security data, such as encryption keys, hashing codes, and digital signatures. The security data are generated internally from the header and the pixel data, thus a strong bond is established between the DICOM data and the corresponding security data. The proposed algorithm has been evaluated extensively using DICOM images of different modalities. Simulation experiments show that confidentiality, authenticity, and integrity have been achieved as reflected by the results we obtained for normalized correlation, entropy, PSNR, histogram analysis, and robustness.

  10. Phonon and magnon heat transport and drag effects

    NASA Astrophysics Data System (ADS)

    Heremans, Joseph P.

    2014-03-01

    Thermoelectric generators and coolers constitute today's solid-state energy converters. The two goals in thermoelectrics research are to enhance the thermopower while simultaneously maintaining a high electrical conductivity of the same material, and to minimize its lattice thermal conductivity without affecting its electronic properties. Up to now the lattice thermal conductivity has been minimized by using alloy scattering and, more recently, nanostructuring. In the first part of the talk, a new approach to minimize the lattice thermal conductivity is described that affects phonon scattering much more than electron scattering. This can be done by selecting potential thermoelectric materials that have a very high anharmonicity, because this property governs phonon-phonon interaction probability. Several possible types of chemical bonds will be described that exhibit such high anharmonicity, and particular emphasis will be put on solids with highly-polarizable lone-pair electrons, such as the rock salt I-V-VI2 compounds (e.g. NaSbSe2). The second part of the talk will give an introduction to a completely new class of solid-state thermal energy converters based on spin transport. One configuration for such energy converters is based on the recently discovered spin-Seebeck effect (SSE). This quantity is expressed in the same units as the conventional thermopower, and we have recently shown that it can be of the same order of magnitude. The main advantage of SSE converters is that the problem of optimization is now distributed over two different materials, a ferromagnet in which a flux of magnetization is generated by a thermal gradient, and a normal metal where the flux of magnetization is converted into electrical power. The talk will focus on the basic physics behind the spin-Seebeck effect. Recent developments will then be described based on phonon-drag of spin polarized electrons. This mechanism has made it possible to reach magnitudes of SSE that are comparable

  11. Water and heat transport in hilly red soil of southern China: II. Modeling and simulation.

    PubMed

    Lu, Jun; Huang, Zhi-Zhen; Han, Xiao-Fei

    2005-05-01

    Simulation models of heat and water transport have not been rigorously tested for the red soils of southern China. Based on the theory of nonisothermal water-heat coupled transfer, a simulation model, programmed in Visual Basic 6.0, was developed to predict the coupled transfer of water and heat in hilly red soil. A series of soil column experiments for soil water and heat transfer, including soil columns with closed and evaporating top end, were used to test the simulation model. Results showed that in the closed columns, the temporal and spatial distribution of moisture and heat could be very well predicted by the model, while in the evaporating columns, the simulated soil water contents were somewhat different from the observed ones. In the heat flow equation from Taylor and Lary (1964), the effects of soil water evaporation on the heat flow is not involved, which may be the main reason for the differences between simulated and observed results. The predicted temperatures were not in agreement with the observed one with thermal conductivities calculated by de Vries and Wierenga equations, so that it is suggested that K(h), soil heat conductivity, be multiplied by 8.0 for the first 6.5 h and by 1.2 later on. Sensitivity analysis of soil water and heat coefficients showed that the saturated hydraulic conductivity, K(S), and the water diffusivity, D(theta), had great effects on soil water transport; the variation of soil porosity led to the difference of soil thermal properties, and accordingly changed temperature redistribution, which would affect water redistribution.

  12. Thermal transport in shock wave–compressed solids using pulsed laser heating

    SciTech Connect

    La Lone, B. M.; Capelle, G.; Stevens, G. D.; Turley, W. D.; Veeser, L. R.

    2014-07-01

    A pulsed laser heating method was developed for determining thermal transport properties of solids under shock-wave compression. While the solid is compressed, a laser deposits a known amount of heat onto the sample surface, which is held in the shocked state by a transparent window. The heat from the laser briefly elevates the surface temperature and then diffuses into the interior via one-dimensional heat conduction. The thermal effusivity is determined from the time history of the resulting surface temperature pulse, which is recorded with optical pyrometry. Thermal effusivity is the square root of the product of thermal conductivity and volumetric heat capacity and is the key thermal transport parameter for relating the surface temperature to the interior temperature of the sample in a dynamic compression experiment. Therefore, this method provides information that is needed to determine the thermodynamic state of the interior of a compressed metal sample from a temperature measurement at the surface. The laser heat method was successfully demonstrated on tin that was shock compressed with explosives to a stress and temperature of ~25 GPa and ~1300 K. In this state, tin was observed to have a thermal effusivity of close to twice its ambient value. The implications on determining the interior shock wave temperature of tin are discussed.

  13. Thermal transport in shock wave–compressed solids using pulsed laser heating

    SciTech Connect

    La Lone, B. M. Capelle, G.; Stevens, G. D.; Turley, W. D.; Veeser, L. R.

    2014-07-15

    A pulsed laser heating method was developed for determining thermal transport properties of solids under shock-wave compression. While the solid is compressed, a laser deposits a known amount of heat onto the sample surface, which is held in the shocked state by a transparent window. The heat from the laser briefly elevates the surface temperature and then diffuses into the interior via one-dimensional heat conduction. The thermal effusivity is determined from the time history of the resulting surface temperature pulse, which is recorded with optical pyrometry. Thermal effusivity is the square root of the product of thermal conductivity and volumetric heat capacity and is the key thermal transport parameter for relating the surface temperature to the interior temperature of the sample in a dynamic compression experiment. Therefore, this method provides information that is needed to determine the thermodynamic state of the interior of a compressed metal sample from a temperature measurement at the surface. The laser heat method was successfully demonstrated on tin that was shock compressed with explosives to a stress and temperature of ∼25 GPa and ∼1300 K. In this state, tin was observed to have a thermal effusivity of close to twice its ambient value. The implications on determining the interior shock wave temperature of tin are discussed.

  14. Electron heat transport comparison in the Large Helical Device and TJ-II

    NASA Astrophysics Data System (ADS)

    García, J.; Dies, J.; Castejón, F.; Yamazaki, K.

    2007-10-01

    The electron heat transport in the Large Helical Device (LHD) [K. Ida, T. Shimozuma, H. Funaba et al., Phys. Rev. Lett. 91, 085003 (2003)] and TJ-II [F. Castejón, V. Tribaldos, I. García-Cortés, E. de la Luna, J. Herranz, I. Pastor, T. Estrada, and TJ-II Team, Nucl. Fusion 42, 271 (2002)] is analyzed by means of the TOTAL [K. Yamazaki and T. Amano, Nucl. Fusion 32, 4 (1992)] and PRETOR-Stellarator [J. Dies, F. Castejon, J. M. Fontdecaba, J. Fontanet, J. Izquierdo, G. Cortes, and C. Alejaldre, Proceedings of the 29th European Physical Society Conference on Plasma Physics and Controlled Fusion, Montreux, 2002, Europhysics Conference Abstracts, 2004, Vol. 26B, P-5.027] plasma simulation codes and assuming a global transport model mixing GyroBohm-like drift wave model and other drift wave model with shorter wavelength. The stabilization of the GyroBohm-like model by the E ×B shear has been also taken into account. Results show how such kind of electron heat transport can simulate experimental evidence in both devices, leading to the electron internal transport barrier (eITB) formation in the LHD and to the so-called "enhanced heat confinement regimes" in TJ-II when electron density is low enough. Therefore, two sources for the anomalous electron heat transport can coexist in plasmas with eITB; however, for each device the relative importance of anomalous and neoclassical transport can be different.

  15. Topics in quantum transport of charge and heat in solid state systems

    NASA Astrophysics Data System (ADS)

    Choi, Yunjin

    In the thesis, we present a series of investigations for quantum transport of charge and heat in solid state systems. The first topic of the thesis focuses on the fundamental quantum problems which can be studied with electron transport along with the correlations of detectors to measure physical properties. We theoretically describe a generalized ``which-path'' measurement using a pair of coupled electronic Mach-Zehnder Interferometers. In the second topic of thesis, we investigate an operational approach to measure the tunneling time based on the Larmor clock. To handle the cases of indirect measurement from the first and second topics, we introduce the contextual values formalism. The form of the contextual values provides direct physical insight into the measurement being performed, providing information about the correlation strength between system and detector, the measurement inefficiency, the proper background removal, and the conditioned average value of the system operator. Additionally, the weak interaction limit of these conditioned averages produces weak values of the system operator and an additional detector dependent disturbance term for both cases. In our treatment of the third topic of the thesis, we propose a three terminal heat engine based on semiconductor superlattices for energy harvesting. The periodicity of the superlattice structure creates an energy miniband, giving an energy window to allow electron transport. We find that this device delivers a large amount of power, nearly twice that produced by the heat engine based on quantum wells, with a small reduction of efficiency. This engine also works as a refrigerator in a different regime of the system's parameters. The thermoelectric performance of the refrigerator is analyzed, including the cooling power and coefficient of performance in the optimized condition. We also calculate phonon heat current through the system and explore the reduction of phonon heat current compared to the bulk

  16. Controlling and measuring quantum transport of heat in trapped-ion crystals.

    PubMed

    Bermudez, A; Bruderer, M; Plenio, M B

    2013-07-26

    Measuring heat flow through nanoscale devices poses formidable practical difficulties as there is no "ampere meter" for heat. We propose to overcome this problem in a chain of trapped ions, where laser cooling the chain edges to different temperatures induces a heat current of local vibrations (vibrons). We show how to efficiently control and measure this current, including fluctuations, by coupling vibrons to internal ion states. This demonstrates that ion crystals provide an ideal platform for studying quantum transport, e.g., through thermal analogues of quantum wires and quantum dots. Notably, ion crystals may give access to measurements of the elusive bosonic fluctuations in heat currents and the onset of Fourier's law. Our results are strongly supported by numerical simulations for a realistic implementation with specific ions and system parameters.

  17. Limits on modes of lithospheric heat transport on Venus from impact crater density

    NASA Technical Reports Server (NTRS)

    Grimm, Robert E.; Solomon, Sean C.

    1987-01-01

    Based on the observed density of impact craters on the Venus surface obtained from Venera 15-16 radar images, a formalism to estimate the upper bounds on the contributions made to lithospheric heat transport by volcanism and lithospheric recycling is presented. The Venera 15-16 data, if representative of the entire planet, limit the average rate of volcanic resurfacing on Venus to less than 2 cu km/yr (corresponding to less than 1 percent of the global heat loss), and limit the rate of lithospheric recycling to less than 1.5 sq km/yr (and probably to less than 0.5 sq km/yr), corresponding to 25 percent (and to 9 percent) of the global heat loss. The present results indicate that heat loss at lithospheric levels in Venus is dominated by conduction.

  18. Simulated spatiotemporal response of ocean heat transport to freshwater enhancement in North Atlantic and associated mechanisms

    NASA Astrophysics Data System (ADS)

    Yu, Lei; Gao, Yongqi

    2011-06-01

    The Atlantic Meridional Overturning Circulation (AMOC) transports a large amount of heat to northern high latitudes, playing an important role in the global climate change. Investigation of the freshwater perturbation in North Atlantic (NA) has become one of the hot topics in the recent years. In this study, the mechanism and pathway of meridional ocean heat transport (OHT) under the enhanced freshwater input to the northern high latitudes in the Atlantic are investigated by an ocean-sea ice-atmosphere coupled model. The results show that the anomalous OHT in the freshwater experiment (FW) is dominated by the meridional circulation kinetic and ocean thermal processes. In the FW, OHT drops down during the period of weakened AMOC while the upper tropical ocean turns warmer due to the retained NA warm currents. Conversely, OHT recovers as the AMOC recovers, and the mechanism can be generalized as: 1) increased ocean heat content in the tropical Southern Ocean during the early integration provides the thermal condition for the recovery of OHT in NA; 2) the OHT from the Southern Ocean enters the NA through the equator along the deep Ekman layer; 3) in NA, the recovery of OHT appears mainly along the isopycnic layers of 24.70-25.77 below the mixing layer. It is then transported into the mixing layer from the "outcropping points" in northern high latitudes, and finally released to the atmosphere by the ocean-atmosphere heat exchange.

  19. Heat and water transport in a polymer electrolyte fuel cell electrode

    SciTech Connect

    Mukherjee, Partha P; Mukundan, Rangachary; Borup, Rod L; Ranjan, Devesh

    2010-01-01

    In the present scenario of a global initiative toward a sustainable energy future, the polymer electrolyte fuel cell (PEFC) has emerged as one of the most promising alternative energy conversion devices for various applications. Despite tremendous progress in recent years, a pivotal performance limitation in the PEFC comes from liquid water transport and the resulting flooding phenomena. Liquid water blocks the open pore space in the electrode and the fibrous diffusion layer leading to hindered oxygen transport. The electrode is also the only component in the entire PEFC sandwich which produces waste heat from the electrochemical reaction. The cathode electrode, being the host to several competing transport mechanisms, plays a crucial role in the overall PEFC performance limitation. In this work, an electrode model is presented in order to elucidate the coupled heat and water transport mechanisms. Two scenarios are specifically considered: (1) conventional, Nafion{reg_sign} impregnated, three-phase electrode with the hydrated polymeric membrane phase as the conveyer of protons where local electro-neutrality prevails; and (2) ultra-thin, two-phase, nano-structured electrode without the presence of ionomeric phase where charge accumulation due to electro-statics in the vicinity of the membrane-CL interface becomes important. The electrode model includes a physical description of heat and water balance along with electrochemical performance analysis in order to study the influence of electro-statics/electro-migration and phase change on the PEFC electrode performance.

  20. Heat transport in a liquid layer locally heated on its free surface

    NASA Astrophysics Data System (ADS)

    Pumir, Alain; Blumenfeld, Laure

    1996-11-01

    A strong heat flux, localized on the upper surface of a fluid, sets up strong convection motions through thermocapillary forces, which limits the temperature elevation in the pool, therefore limiting the efficiency in fusion welding processes. We propose a theoretical estimate of the temperature elevation when the fluid motion is laminar or turbulent, the weld pool surface remaining flat. Our treatment follows the theoretical work of Shraiman and Siggia [

    Phys. Rev. A 42, 3650 (1990)
    ] in Rayleigh-Bénard convection. In the laminar case, the temperature elevation is proportional to the incident power to the 34 power, in agreement with earlier estimates, and in the turbulent case, to the incident power to the 23 power.

  1. Graphene transport properties upon exposure to PMMA processing and heat treatments

    NASA Astrophysics Data System (ADS)

    Gammelgaard, Lene; Caridad, José M.; Cagliani, Alberto; Mackenzie, David M. A.; Petersen, Dirch H.; Booth, Timothy J.; Bøggild, Peter

    2014-12-01

    The evolution of graphene's electrical transport properties due to processing with the polymer polymethyl methacrylate (PMMA) and heat are examined in this study. The use of stencil (shadow mask) lithography enables fabrication of graphene devices without the usage of polymers, chemicals or heat, allowing us to measure the evolution of the electrical transport properties during individual processing steps from the initial as-exfoliated to the PMMA-processed graphene. Heating generally promotes the conformation of graphene to SiO2 and is found to play a major role for the electrical properties of graphene while PMMA residues are found to be surprisingly benign. In accordance with this picture, graphene devices with initially high carrier mobility tend to suffer a decrease in carrier mobility, while in contrast an improvement is observed for low carrier mobility devices. We explain this by noting that flakes conforming poorly to the substrate will have a higher carrier mobility which will however be reduced as heat treatment enhance the conformation. We finally show the electrical properties of graphene to be reversible upon heat treatments in air up to 200 °C.

  2. Effects of tropical cyclones on large-scale circulation and ocean heat transport in the South China Sea

    NASA Astrophysics Data System (ADS)

    Wang, Xidong; Wang, Chunzai; Han, Guijun; Li, Wei; Wu, Xinrong

    2014-12-01

    In this study, we investigate the influence of tropical cyclones (TCs) on large-scale circulation and ocean heat transport in the South China Sea (SCS) by using an ocean general circulation model at a 1/8° resolution during 2000-2008. The model uses a data assimilation system to assimilate observations in order to improve the representation of SCS circulation. The results reveal an unexpected deep SCS circulation anomaly induced by TCs, which suggests that effects of TC can penetrate deeper into the ocean. This deep effect may result from the near inertial oscillations excited by TCs. The inertial oscillations can propagate downward to the oceanic interior. The analyses confirm that TCs have two effects on ocean heat transport of the SCS. Firstly, the wind stress curl induced by TCs affects the structure of SCS circulation, and then changes heat transport. Secondly, TCs pump surface heat downward to the thermocline, increasing the heat injection from the atmosphere to the ocean. Two effects together amplify the outflow of the surface heat southward away the SCS through the Mindoro and Karimata Straits. The TC-induced heat transports through the Mindoro, Balabac and Karimata Straits account for 20 % of the total heat transport through three straits. An implication of this study is that ocean models need to simulate the TC effect on heat transport in order to correctly evaluate the role of the SCS through flow in regulating upper ocean circulation and climate in the Indonesian maritime continent and its adjacent regions.

  3. Finite speed heat transport in a quantum spin chain after quenched local cooling

    NASA Astrophysics Data System (ADS)

    Fries, Pascal; Hinrichsen, Haye

    2017-04-01

    We study the dynamics of an initially thermalized spin chain in the quantum XY-model, after sudden coupling to a heat bath of lower temperature at one end of the chain. In the semi-classical limit we see an exponential decay of the system-bath heatflux by exact solution of the reduced dynamics. In the full quantum description however, we numerically find the heatflux to reach intermediate plateaus where it is approximately constant—a phenomenon that we attribute to the finite speed of heat transport via spin waves.

  4. Working fluid selection for space-based two-phase heat transport systems

    NASA Technical Reports Server (NTRS)

    Mclinden, Mark O.

    1988-01-01

    The working fluid for externally-mounted, space-based two-phase heat transport systems is considered. A sequence of screening criteria involving freezing and critical point temperatures and latent heat of vaporization and vapor density are applied to a data base of 860 fluids. The thermal performance of the 52 fluids which pass this preliminary screening are then ranked according to their impact on the weight of a reference system. Upon considering other nonthermal criteria (flammability, toxicity, and chemical stability) a final set of 10 preferred fluids is obtained. The effects of variations in system parameters is investigated for these 10 fluids by means of a factorial design.

  5. Atmospheric Compensation of Variations in Tropical Ocean Heat Transport: Understanding Mechanisms and Implications on Tectonic Timescales

    NASA Astrophysics Data System (ADS)

    Rencurrel, M. C.; Rose, B. E. J.

    2015-12-01

    The poleward transport of energy is a key aspect of the climate system, with surface ocean currents presently dominating the transport out of deep tropics. A classic study by Stone (1978) proposed that the total heat transport is determined by astronomical parameters and is highly insensitive to the detailed atmosphere-ocean dynamics. On the other hand, previous modeling work has shown that past continental configurations could have produced substantially different tropical ocean heat transport (OHT). How thoroughly does the atmosphere compensate for changes in ocean transport in terms of the top-of-atmosphere (TOA) radiative budget, what are the relevant mechanisms, and what are the consequences for surface temperature and climate on tectonic timescales? We examine these issues in a suite of aquaplanet GCM simulations subject to large prescribed variations in OHT. We find substantial but incomplete compensation, in which adjustment of the atmospheric Hadley circulation plays a key role. We then separate out the dynamical and thermodynamical components of the adjustment mechanism. Increased OHT tends to warm the mid- to high latitudes without cooling the tropics due asymmetries in radiative feedback processes. The warming is accompanied by hydrological cycle changes that are completely different from those driven by greenhouse gases, suggesting that drivers of past global change might be detectable from combinations of hydroclimate and temperature proxies.

  6. Steady-state heat transport: Ballistic-to-diffusive with Fourier's law

    SciTech Connect

    Maassen, Jesse Lundstrom, Mark

    2015-01-21

    It is generally understood that Fourier's law does not describe ballistic phonon transport, which is important when the length of a material is similar to the phonon mean-free-path. Using an approach adapted from electron transport, we demonstrate that Fourier's law and the heat equation do capture ballistic effects, including temperature jumps at ideal contacts, and are thus applicable on all length scales. Local thermal equilibrium is not assumed, because allowing the phonon distribution to be out-of-equilibrium is important for ballistic and quasi-ballistic transport. The key to including the non-equilibrium nature of the phonon population is to apply the proper boundary conditions to the heat equation. Simple analytical solutions are derived, showing that (i) the magnitude of the temperature jumps is simply related to the material properties and (ii) the observation of reduced apparent thermal conductivity physically stems from a reduction in the temperature gradient and not from a reduction in actual thermal conductivity. We demonstrate how our approach, equivalent to Fourier's law, easily reproduces results of the Boltzmann transport equation, in all transport regimes, even when using a full phonon dispersion and mean-free-path distribution.

  7. An asymptotic-preserving Lagrangian algorithm for the time-dependent anisotropic heat transport equation

    SciTech Connect

    Chacon, Luis; del-Castillo-Negrete, Diego; Hauck, Cory D.

    2014-09-01

    We propose a Lagrangian numerical algorithm for a time-dependent, anisotropic temperature transport equation in magnetized plasmas in the large guide field regime. The approach is based on an analytical integral formal solution of the parallel (i.e., along the magnetic field) transport equation with sources, and it is able to accommodate both local and non-local parallel heat flux closures. The numerical implementation is based on an operator-split formulation, with two straightforward steps: a perpendicular transport step (including sources), and a Lagrangian (field-line integral) parallel transport step. Algorithmically, the first step is amenable to the use of modern iterative methods, while the second step has a fixed cost per degree of freedom (and is therefore scalable). Accuracy-wise, the approach is free from the numerical pollution introduced by the discrete parallel transport term when the perpendicular to parallel transport coefficient ratio X /X becomes arbitrarily small, and is shown to capture the correct limiting solution when ε = X⊥L2/X1L2 → 0 (with L∥∙ L⊥ , the parallel and perpendicular diffusion length scales, respectively). Therefore, the approach is asymptotic-preserving. We demonstrate the capabilities of the scheme with several numerical experiments with varying magnetic field complexity in two dimensions, including the case of transport across a magnetic island.

  8. All-optical packet header and payload separation based on two TOADs for optical packet switched networks

    NASA Astrophysics Data System (ADS)

    Ji, Wei; Zhang, Min; Ye, Peida

    2006-09-01

    We present a novel all-optical header and payload separation technique that can be utilized in Un-Slotted optical packet switched networks. The technique uses two modified TOADs, one is for packet header extraction with differential modulation scheme and the other performs a simple XOR operation between the packet and its self-derived header to get the separated payload. The main virtue of this system is simple structure and low power consumption. Through numerical simulations, the operating characteristics of the scheme are illustrated. In addition, the system parameters are discussed and designed to optimize the performance of the proposed scheme.

  9. A non-equilibrium thermodynamics model of multicomponent mass and heat transport in pervaporation processes

    NASA Astrophysics Data System (ADS)

    Villaluenga, Juan P. G.; Kjelstrup, Signe

    2012-12-01

    The framework of non-equilibrium thermodynamics (NET) is used to derive heat and mass transport equations for pervaporation of a binary mixture in a membrane. In this study, the assumption of equilibrium of the sorbed phase in the membrane and the adjacent phases at the feed and permeate sides of the membrane is abandoned, defining the interface properties using local equilibrium. The transport equations have been used to model the pervaporation of a water-ethanol mixture, which is typically encountered in the dehydration of organics. The water and ethanol activities and temperature profiles are calculated taking mass and heat coupling effects and surfaces into account. The NET approach is deemed good because the temperature results provided by the model are comparable to experimental results available for water-alcohol systems.

  10. Convective Heat Transfer in the Reusable Solid Rocket Motor of the Space Transportation System

    NASA Technical Reports Server (NTRS)

    Ahmad, Rashid A.; Cash, Stephen F. (Technical Monitor)

    2002-01-01

    This simulation involved a two-dimensional axisymmetric model of a full motor initial grain of the Reusable Solid Rocket Motor (RSRM) of the Space Transportation System (STS). It was conducted with CFD (computational fluid dynamics) commercial code FLUENT. This analysis was performed to: a) maintain continuity with most related previous analyses, b) serve as a non-vectored baseline for any three-dimensional vectored nozzles, c) provide a relatively simple application and checkout for various CFD solution schemes, grid sensitivity studies, turbulence modeling and heat transfer, and d) calculate nozzle convective heat transfer coefficients. The accuracy of the present results and the selection of the numerical schemes and turbulence models were based on matching the rocket ballistic predictions of mass flow rate, head end pressure, vacuum thrust and specific impulse, and measured chamber pressure drop. Matching these ballistic predictions was found to be good. This study was limited to convective heat transfer and the results compared favorably with existing theory. On the other hand, qualitative comparison with backed-out data of the ratio of the convective heat transfer coefficient to the specific heat at constant pressure was made in a relative manner. This backed-out data was devised to match nozzle erosion that was a result of heat transfer (convective, radiative and conductive), chemical (transpirating), and mechanical (shear and particle impingement forces) effects combined.

  11. On the glacial and interglacial thermohaline circulation and the associated transports of heat and freshwater

    NASA Astrophysics Data System (ADS)

    Ballarotta, M.; Falahat, S.; Brodeau, L.; Döös, K.

    2014-11-01

    The thermohaline circulation (THC) and the oceanic heat and freshwater transports are essential for understanding the global climate system. Streamfunctions are widely used in oceanography to represent the THC and estimate the transport of heat and freshwater. In the present study, the regional and global changes of the THC, the transports of heat and freshwater and the timescale of the circulation between the Last Glacial Maximum (LGM, ≈ 21 kyr ago) and the present-day climate are explored using an Ocean General Circulation Model and streamfunctions projected in various coordinate systems. We found that the LGM tropical circulation is about 10% stronger than under modern conditions due to stronger wind stress. Consequently, the maximum tropical transport of heat is about 20% larger during the LGM. In the North Atlantic basin, the large sea-ice extent during the LGM constrains the Gulf Stream to propagate in a more zonal direction, reducing the transport of heat towards high latitudes by almost 50% and reorganising the freshwater transport. The strength of the Atlantic Meridional Overturning Circulation depends strongly on the coordinate system. It varies between 9 and 16 Sv during the LGM, and between 12 to 19 Sv for the present day. Similar to paleo-proxy reconstructions, a large intrusion of saline Antarctic Bottom Water takes place into the Northern Hemisphere basins and squeezes most of the Conveyor Belt circulation into a shallower part of the ocean. These different haline regimes between the glacial and interglacial period are illustrated by the streamfunctions in latitude-salinity coordinates and thermohaline coordinates. From these diagnostics, we found that the LGM Conveyor Belt circulation is driven by an enhanced salinity contrast between the Atlantic and the Pacific basin. The LGM abyssal circulation lifts and makes the Conveyor Belt cell deviate from the abyssal region, resulting in a ventilated upper layer above a deep stagnant layer, and an

  12. SEAWAT Version 4: A Computer Program for Simulation of Multi-Species Solute and Heat Transport

    USGS Publications Warehouse

    Langevin, Christian D.; Thorne, Daniel T.; Dausman, Alyssa M.; Sukop, Michael C.; Guo, Weixing

    2008-01-01

    The SEAWAT program is a coupled version of MODFLOW and MT3DMS designed to simulate three-dimensional, variable-density, saturated ground-water flow. Flexible equations were added to the program to allow fluid density to be calculated as a function of one or more MT3DMS species. Fluid density may also be calculated as a function of fluid pressure. The effect of fluid viscosity variations on ground-water flow was included as an option. Fluid viscosity can be calculated as a function of one or more MT3DMS species, and the program includes additional functions for representing the dependence on temperature. Although MT3DMS and SEAWAT are not explicitly designed to simulate heat transport, temperature can be simulated as one of the species by entering appropriate transport coefficients. For example, the process of heat conduction is mathematically analogous to Fickian diffusion. Heat conduction can be represented in SEAWAT by assigning a thermal diffusivity for the temperature species (instead of a molecular diffusion coefficient for a solute species). Heat exchange with the solid matrix can be treated in a similar manner by using the mathematically equivalent process of solute sorption. By combining flexible equations for fluid density and viscosity with multi-species transport, SEAWAT Version 4 represents variable-density ground-water flow coupled with multi-species solute and heat transport. SEAWAT Version 4 is based on MODFLOW-2000 and MT3DMS and retains all of the functionality of SEAWAT-2000. SEAWAT Version 4 also supports new simulation options for coupling flow and transport, and for representing constant-head boundaries. In previous versions of SEAWAT, the flow equation was solved for every transport timestep, regardless of whether or not there was a large change in fluid density. A new option was implemented in SEAWAT Version 4 that allows users to control how often the flow field is updated. New options were also implemented for representing constant

  13. The Arctic Mediterranean Sea - Deep convection, oceanic heat transport and freshwater

    NASA Astrophysics Data System (ADS)

    Rudels, Bert

    2014-05-01

    The speculations about the driving forces behind the oceanic meridional circulation and the importance of the northward transports of oceanic heat for the ice conditions in the Arctic Ocean have a long history, but only after the Fram expedition 1893-1896 and from the studies by Nansen, Helland-Hansen and Sandström in the early 1900s did these speculations attain observational substance. In the late 1970s and onward these questions have again risen to prominence. A study of deep convection in the Greenland Sea, then assumed to drive the global thermohaline circulation, started with the Greenland Sea Project (GSP), while the investigation of the exchanges of volume and heat through Fram Strait had a more hesitant start in the Fram Strait Project (FSP). Not until 1997 with the EC project VEINS (Variation of Exchanges in the Northern Seas) was a mooring array deployed across Fram Strait. This array has been maintained and has measured the exchanges ever since. Eberhard Fahrbach was closely involved in these studies, as a secretary for the GSP and as the major driving force behind the Fram Strait array. Here we shall examine the legacy of these projects; How our understanding of these themes has evolved in recent years. After the 1980s no convective bottom water renewal has been observed in the Greenland Sea, and the Greenland Sea deep waters have gradually been replaced by warmer, more saline deep water from the Arctic Ocean passing through Fram Strait. Small-scale convective events penetrating deeper than 2500m but there less dense than their surroundings were, however, observed in the early 2000s. The Fram Strait exchanges have proven difficult to estimate due to strong variability, high barotropic and baroclinic eddy activity and short lateral coherence scales. The fact that the mass transports through Fram Strait do not balance complicates the assessment of the heat transport through Fram Strait into the Arctic Ocean and mass (volume) and salt (freshwater

  14. Isotopic and trace element sensors for fluid flow, heat- and mass transport in fractured rocks

    NASA Astrophysics Data System (ADS)

    DePaolo, D. J.

    2012-12-01

    The flow of fluids through fractured rocks is critically important in hydrothermal systems associated with geothermal energy production, base metal ore deposits, and global geochemical cycles through the enormous volumes of fluids in mid-ocean ridge systems. The nature of heat and mass transport in hydrothermal systems is determined by the spacing and volume of fractures, the nature of chemical transport in matrix blocks between fractures, the dissolution and precipitation rates of minerals in the matrix blocks, and the rates of fluid flow. Directly measuring these properties in active systems is extremely difficult, but the chemical and isotopic composition of fluids, where they can be adequately sampled, provides this information in coded form. Deciphering the signals requires appropriate models for the mineral-fluid chemical reactions and transport in the inter-fracture rock matrix. Ultimately, numerical reactive transport models are required to properly account for coupling between mineral reaction kinetics and fluid phase transport, but it is surprisingly difficult to adequately represent isotopic exchange in these models. The difficulty comes partly from the additional bookkeeping that is necessary, but more fundamentally from limitations in the detailed molecular dynamics of the mineral-fluid interfaces and how they control isotopic exchange and partitioning. Nevertheless, relatively simple analytical models illustrate how the isotopic and trace element composition of fluids relates to fracture aperture and spacing, mineral dissolution kinetics, competition between diffusive and advective transport, and competition between chemical exchange and heat exchange. The large number of geochemical parameters that can be measured potentially allows for detailed characterization of the effective mass transport and system characteristics like average fracture spacing and mineral dissolution rates. Examples of useful analytical models and applications to available data

  15. Three-Dimensional Modeling of Fluid and Heat Transport in an Accretionary Complex

    NASA Astrophysics Data System (ADS)

    Paula, C. A.; Ge, S.; Screaton, E. J.

    2001-12-01

    As sediments are scraped off of the subducting oceanic crust and accreted to the overriding plate, the rapid loading causes pore pressures in the underthrust sediments to increase. The change in pore pressure drives fluid flow and heat transport within the accretionary complex. Fluid is channeled along higher permeability faults and fractures and expelled at the seafloor. In this investigation, we examined the effects of sediment loading on fluid flow and thermal transport in the decollement at the Barbados Ridge subduction zone. Both the width and thickness of the Barbados Ridge accretionary complex increase from north to south. The presence of mud diapers south of the Tiburon Rise and an observed southward decrease in heat flow measurements indicate that the increased thickness of the southern Barbados accretionary prism affects the transport of chemicals and heat by fluids. The three-dimensional geometry and physical properties of the accretionary complex were utilized to construct a three-dimensional fluid flow/heat transport model. We calculated the pore pressure change due to a period of sediment loading and added this to steady-state pressure conditions to generate initial conditions for transient simulations. We then examined the diffusion of pore pressure and possible perturbation of the thermal regime over time due to loading of the underthrust sediments. The model results show that the sediment-loading event was sufficient to create small temperature fluctuations in the decollement zone. The magnitude of temperature fluctuation in the decollement was greatest at the deformation front but did not vary significantly from north to south of the Tiburon Rise.

  16. The development of a high-capacity instrument module heat transport system, appendixes

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Data sheets provide temperature requirements for 82 individual instruments that are under development or planned for grouping on a space platform or pallet. The scientific objectives of these instrument packages are related to solar physics, space plasma physics, astronomy, high energy astrophysics, resources observations, environmental observations, materials processing, and life sciences. System specifications are given for a high capacity instrument module heat transport system to be used with future payloads.

  17. Numerical simulations of heat and moisture transport in thermal protective clothing under flash fire conditions.

    PubMed

    Song, Guowen; Chitrphiromsri, Patirop; Ding, Dan

    2008-01-01

    A numerical model of heat and moisture transport in thermal protective clothing during exposure to a flash fire was introduced. The model was developed with the assumption that textiles are treated as porous media. The numerical model predictions were compared with experimental data from different fabric systems and configurations. Additionally, with the introduction of a skin model, the parameters that affect the performance of thermal protective clothing were investigated.

  18. Heat transport in polymer thin films for micro/nano-manufacturing

    NASA Astrophysics Data System (ADS)

    Hung, Ming-Tsung

    The rapid growth in micro/nanotechnology has opened a great opportunity for polymer thin films and polymer nanocomposites. Thermal management or thermal effects in those applications need to be carefully examined. For example, the local heating in electron-beam lithography, emersion lithography, and scanning near field optical lithography may cause the degradation of photoresists and reduce the resolution. The development of many organic electronics, polymer micro-electro-mechanical-systems (MEMS) devices, and polymer nanocomposites may require the knowledge of heat transport in micro/nano-sized polymers. Thermolithography, a novel lithography, uses controlled localized heating to transfer patterns and requires the thermal conductivity data to control. It is of considerable scientific and technological interests for study heat transport in polymer thin films. Unlike bulk polymers that can be measured using commercially available instruments, polymer thin films are difficult to measure. In this manuscript, we develop the measurement techniques suitable for measuring thermal conductivity of polymer thin films and polymer nanocomposites. Using a microfabricated membrane-based device, we study the heat conduction in photoresists at difference process stages. This data is used in our thermolithography study, where we use microheater to study the kinetic of crosslinking reaction of photoresist. The feasibility of thermolithography and potential three dimensional micro/nano-fabrication is presented. The uniqueness of thermolithography is also demonstrated by patterning amorphous fluoropolymers. A modified hot-wire technique is used to measure the thermal conductivity of graphite nanoplatelet (GNP) reinforced nanocomposites, one of the promising candidates for multifunctional materials. Thermal interface resistance in GNP nanocomposites is investigated, which shows a strong effect on energy transport in the nanocomposites and can be diminished through surface treatment.

  19. Heat Exchanger Design Options and Tritium Transport Study for the VHTR System

    SciTech Connect

    Chang H. Oh; Eung S. Kim

    2008-09-01

    This report presents the results of a study conducted to consider heat exchanger options and tritium transport in a very high temperature reactor (VHTR) system for the Next Generation Nuclear Plant Project. The heat exchanger options include types, arrangements, channel patterns in printed circuit heat exchangers (PCHE), coolant flow direction, and pipe configuration in shell-and-tube designs. Study considerations include: three types of heat exchanger designs (PCHE, shell-and-tube, and helical coil); single- and two-stage unit arrangements; counter-current and cross flow configurations; and straight pipes and U-tube designs in shell-and-tube type heat exchangers. Thermal designs and simple stress analyses were performed to estimate the heat exchanger options, and the Finite Element Method was applied for more detailed calculations, especially for PCHE designs. Results of the options study show that the PCHE design has the smallest volume and heat transfer area, resulting in the least tritium permeation and greatest cost savings. It is theoretically the most reliable mechanically, leading to a longer lifetime. The two-stage heat exchanger arrangement appears to be safer and more cost effective. The recommended separation temperature between first and second stages in a serial configuration is 800oC, at which the high temperature unit is about one-half the size of the total heat exchanger core volume. Based on simplified stress analyses, the high temperature unit will need to be replaced two or three times during the plant’s lifetime. Stress analysis results recommend the off-set channel pattern configuration for the PCHE because stress reduction was estimated at up to 50% in this configuration, resulting in a longer lifetime. The tritium transport study resulted in the development of a tritium behavior analysis code using the MATLAB Simulink code. In parallel, the THYTAN code, previously performed by Ohashi and Sherman (2007) on the Peach Bottom data, was revived

  20. Icing Protection for a Turbojet Transport Airplane: Heating Requirements, Methods of Protection, and Performance Penalties

    NASA Technical Reports Server (NTRS)

    Gelder, Thomas F.; Lewis, James P.; Koutz, Stanley L.

    1953-01-01

    The problems associated with providing icing protection for the critical components of a typical turbojet transport airplane operating over a range of probable icing conditions are analyzed and discussed. Heating requirements for several thermal methods of protection are evaluated and the airplane performance penalties associated with providing this protection from various energy sources are assessed. The continuous heating requirements for icing protection and the associated airplane performance penalties for the turbojet transport are considerably increased over those associated with lower-speed aircraft. Experimental results show that the heating requirements can be substantially reduced by the deve1opment of a satisfactory cyclic deicing system. The problem of providing protection can be minimized by employing a proper energy source since the airplane performance penalties vary considerably with the source of energy employed. The optimum icing protection system for the turbojet transport or for any other particular aircraft cannot be generally specified; the choice of the optimum system is dependent upon the specific characteristics of the airplane and engine, the flight plan, the probable icing conditions, and the performance requirements of the aircraft.

  1. A one-dimensional heat-transport model for conduit flow in karst aquifers

    USGS Publications Warehouse

    Long, A.J.; Gilcrease, P.C.

    2009-01-01

    A one-dimensional heat-transport model for conduit flow in karst aquifers is presented as an alternative to two or three-dimensional distributed-parameter models, which are data intensive and require knowledge of conduit locations. This model can be applied for cases where water temperature in a well or spring receives all or part of its water from a phreatic conduit. Heat transport in the conduit is simulated by using a physically-based heat-transport equation that accounts for inflow of diffuse flow from smaller openings and fissures in the surrounding aquifer during periods of low recharge. Additional diffuse flow that is within the zone of influence of the well or spring but has not interacted with the conduit is accounted for with a binary mixing equation to proportion these different water sources. The estimation of this proportion through inverse modeling is useful for the assessment of contaminant vulnerability and well-head or spring protection. The model was applied to 7 months of continuous temperature data for a sinking stream that recharges a conduit and a pumped well open to the Madison aquifer in western South Dakota. The simulated conduit-flow fraction to the well ranged from 2% to 31% of total flow, and simulated conduit velocity ranged from 44 to 353 m/d.

  2. The role of radiation transport in the thermal response of semitransparent materials to localized laser heating

    SciTech Connect

    Colvin, Jeffrey; Shestakov, Aleksei; Stolken, James; Vignes, Ryan

    2011-03-09

    Lasers are widely used to modify the internal structure of semitransparent materials for a wide variety of applications, including waveguide fabrication and laser glass damage healing. The gray diffusion approximation used in past models to describe radiation cooling is not adequate for these materials, particularly near the heated surface layer. In this paper we describe a computational model based upon solving the radiation transport equation in 1D by the Pn method with ~500 photon energy bands, and by multi-group radiationdiffusion in 2D with fourteen photon energy bands. The model accounts for the temperature-dependent absorption of infrared laser light and subsequent redistribution of the deposited heat by both radiation and conductive transport. We present representative results for fused silica irradiated with 2–12 W of 4.6 or 10.6 µm laser light for 5–10 s pulse durations in a 1 mm spot, which is small compared to the diameter and thickness of the silica slab. Furthermore, we show that, unlike the case for bulk heating, in localized infrared laser heatingradiation transport plays only a very small role in the thermal response of silica.

  3. Physical aspects of thermotherapy: A study of heat transport with a view to treatment optimisation

    NASA Astrophysics Data System (ADS)

    Olsrud, Johan Karl Otto

    1998-12-01

    Local treatment with the aim to destruct tissue by heating (thermotherapy) may in some cases be an alternative or complement to surgical methods, and has gained increased interest during the last decade. The major advantage of these, often minimally-invasive methods, is that the disease can be controlled with reduced treatment trauma and complications. The extent of thermal damage is a complex function of the physical properties of tissue, which influence the temperature distribution, and of the biological response to heat. In this thesis, methods of obtaining a well-controlled treatment have been studied from a physical point of view, with emphasis on interstitial laser-induced heating of tumours in the liver and intracavitary heating as a treatment for menorrhagia. Hepatic inflow occlusion, in combination with temperature-feedback control of the output power of the laser, resulted in well defined damaged volumes during interstitial laser thermotherapy in normal porcine liver. In addition, phantom experiments showed that the use of multiple diffusing laser fibres allows heating of clinically relevant tissue volumes in a single session. Methods for numerical simulation of heat transport were used to calculate the temperature distribution and the results agreed well with experiments. It was also found from numerical simulation that the influence of light transport on the damaged volume may be negligible in interstitial laser thermotherapy in human liver. Finite element analysis, disregarding light transport, was therefore proposed as a suitable method for 3D treatment planning. Finite element simulation was also used to model intracavitary heating of the uterus, with the purpose of providing an increased understanding of the influence of various treatment parameters on blood flow and on the depth of tissue damage. The thermal conductivity of human uterine tissue, which was used in these simulations, was measured. Furthermore, magnetic resonance imaging (MRI) was

  4. The effect of anisotropic heat transport on magnetic islands in 3-D configurations

    SciTech Connect

    Schlutt, M. G.; Hegna, C. C.

    2012-08-15

    An analytic theory of nonlinear pressure-induced magnetic island formation using a boundary layer analysis is presented. This theory extends previous work by including the effects of finite parallel heat transport and is applicable to general three dimensional magnetic configurations. In this work, particular attention is paid to the role of finite parallel heat conduction in the context of pressure-induced island physics. It is found that localized currents that require self-consistent deformation of the pressure profile, such as resistive interchange and bootstrap currents, are attenuated by finite parallel heat conduction when the magnetic islands are sufficiently small. However, these anisotropic effects do not change saturated island widths caused by Pfirsch-Schlueter current effects. Implications for finite pressure-induced island healing are discussed.

  5. Linearization of a heat-transfer system model with approximation of transport time delay

    NASA Astrophysics Data System (ADS)

    Shilin, A. A.; Bukreev, V. G.

    2014-10-01

    A method is proposed for linearizing the nonlinear model of a heat-transfer facility the state variables of which at equilibrium points are determined by numerically solving the initial bilinear system of differential equations for a stationary position of the control valve equipped with a constant-speed electric drive. The considerable transport time delay resulting from the distributed design of the heat-transfer system secondary circuit is approximated by a limited number of first-order inertial sections for obtaining a mathematical model in the Cauchy form. The proposed linearization method is tested on an operating hot-water supply heat-transfer system, and the study results are presented in the form of transient curves.

  6. Fingerprint of topological Andreev bound states in phase-dependent heat transport

    NASA Astrophysics Data System (ADS)

    Sothmann, Björn; Hankiewicz, Ewelina M.

    2016-08-01

    We demonstrate that phase-dependent heat currents through superconductor-topological insulator Josephson junctions provide a useful tool to probe the existence of topological Andreev bound states, even for multichannel surface states. We predict that in the tunneling regime topological Andreev bound states lead to a minimum of the thermal conductance for a phase difference ϕ =π , in clear contrast to a maximum of the thermal conductance at ϕ =π that occurs for trivial Andreev bound states in superconductor-normal-metal tunnel junctions. This opens up the possibility that phase-dependent heat transport can distinguish between topologically trivial and nontrivial 4 π modes. Furthermore, we propose a superconducting quantum interference device geometry where phase-dependent heat currents can be measured using available experimental technology.

  7. Anomalous quantum heat transport in a one-dimensional harmonic chain with random couplings.

    PubMed

    Yan, Yonghong; Zhao, Hui

    2012-07-11

    We investigate quantum heat transport in a one-dimensional harmonic system with random couplings. In the presence of randomness, phonon modes may normally be classified as ballistic, diffusive or localized. We show that these modes can roughly be characterized by the local nearest-neighbor level spacing distribution, similarly to their electronic counterparts. We also show that the thermal conductance G(th) through the system decays rapidly with the system size (G(th) ∼ L(-α)). The exponent α strongly depends on the system size and can change from α < 1 to α > 1 with increasing system size, indicating that the system undergoes a transition from a heat conductor to a heat insulator. This result could be useful in thermal control of low-dimensional systems.

  8. Mass transport, corrosion, plugging, and their reduction in solar dish/Stirling heat pipe receivers

    SciTech Connect

    Adkins, D.R.; Andraka, C.E.; Bradshaw, R.W.; Goods, S.H.; Moreno, J.B.; Moss, T.A.

    1996-07-01

    Solar dish/Stirling systems using sodium heat pipe receivers are being developed by industry and government laboratories here and abroad. The unique demands of this application lead to heat pipe wicks with very large surface areas and complex three-dimensional flow patterns. These characteristics can enhance the mass transport and concentration of constituents of the wick material, resulting in wick corrosion and plugging. As the test times for heat pipe receivers lengthen, we are beginning to see these effects both indirectly, as they affect performance, and directly in post-test examinations. We are also beginning to develop corrective measures. In this paper, we report on our test experiences, our post-test examinations, and on our initial effort to ameliorate various problems.

  9. Gas production and transport during bench-scale electrical resistance heating of water and trichloroethene.

    PubMed

    Hegele, P R; Mumford, K G

    2014-09-01

    The effective remediation of chlorinated solvent source zones using in situ thermal treatment requires successful capture of gas that is produced. Replicate electrical resistance heating experiments were performed in a thin bench-scale apparatus, where water was boiled and pooled dense non-aqueous phase liquid (DNAPL) trichloroethene (TCE) and water were co-boiled in unconsolidated silica sand. Quantitative light transmission visualization was used to assess gas production and transport mechanisms. In the water boiling experiments, nucleation, growth and coalescence of the gas phase into connected channels were observed at critical gas saturations of Sgc=0.233±0.017, which allowed for continuous gas transport out of the sand. In experiments containing a colder region above a target heated zone, condensation prevented the formation of steam channels and discrete gas clusters that mobilized into colder regions were trapped soon after discontinuous transport began. In the TCE-water experiments, co-boiling at immiscible fluid interfaces resulted in discontinuous gas transport above the DNAPL pool. Redistribution of DNAPL was also observed above the pool and at the edge of the vapor front that propagated upwards through colder regions. These results suggest that the subsurface should be heated to water boiling temperatures to facilitate gas transport from specific locations of DNAPL to extraction points and reduce the potential for DNAPL redistribution. Decreases in electric current were observed at the onset of gas phase production, which suggests that coupled electrical current and temperature measurements may provide a reliable metric to assess gas phase development.

  10. Gas production and transport during bench-scale electrical resistance heating of water and trichloroethene

    NASA Astrophysics Data System (ADS)

    Hegele, P. R.; Mumford, K. G.

    2014-09-01

    The effective remediation of chlorinated solvent source zones using in situ thermal treatment requires successful capture of gas that is produced. Replicate electrical resistance heating experiments were performed in a thin bench-scale apparatus, where water was boiled and pooled dense non-aqueous phase liquid (DNAPL) trichloroethene (TCE) and water were co-boiled in unconsolidated silica sand. Quantitative light transmission visualization was used to assess gas production and transport mechanisms. In the water boiling experiments, nucleation, growth and coalescence of the gas phase into connected channels were observed at critical gas saturations of Sgc = 0.233 ± 0.017, which allowed for continuous gas transport out of the sand. In experiments containing a colder region above a target heated zone, condensation prevented the formation of steam channels and discrete gas clusters that mobilized into colder regions were trapped soon after discontinuous transport began. In the TCE-water experiments, co-boiling at immiscible fluid interfaces resulted in discontinuous gas transport above the DNAPL pool. Redistribution of DNAPL was also observed above the pool and at the edge of the vapor front that propagated upwards through colder regions. These results suggest that the subsurface should be heated to water boiling temperatures to facilitate gas transport from specific locations of DNAPL to extraction points and reduce the potential for DNAPL redistribution. Decreases in electric current were observed at the onset of gas phase production, which suggests that coupled electrical current and temperature measurements may provide a reliable metric to assess gas phase development.

  11. The study of latent heat transport characteristics by solid particles and saccharide solution mixtures

    NASA Astrophysics Data System (ADS)

    Morita, Shin-ichi; Hayamizu, Yasutaka; Inaba, Hideo

    2011-06-01

    The purpose of this study is the development of latent heat transport system by using the mixture of the minute latent heat storage materials and the saccharine solution as medium. The experimental studies are carried out by the evaluation of viscosity and pressure loss in a pipe. Polyethylene (P.E.) is selected as the dispersed minute material that has closeness density (920kg/m3) of ice (917kg/m3). D-sorbitol and D-xylose solutions are picked as continuum phase of the test mixture. The concentration of D-sorbitol solution is set 48mass% from measured results of saturation solubility and the melting point. 40mass% solution of D-xylose is selected as the other test continuum phase. The non-ion surfactant, EA157 Dai-ichiseiyaku CO. Ltd, is used in order to prevent of dispersed P.E. powder cohere. The pressure loss of test mixture is measured by the straight circular pipe that has smooth inner surface. The measuring length for pressure loss is 1000 mm, and the inner diameter of pipe is 15mm. The accuracy of experiment apparatus for measuring pressure loss is within ±5%. The pressure loss data is estimated by the relationship between the heat transport ratio and the required pump power. It is clarified that the optimum range of mixing ratio exists over 10mass% of latent heat storage material.

  12. Solute and heat transport model of the Henry and hilleke laboratory experiment.

    PubMed

    Langevin, Christian D; Dausman, Alyssa M; Sukop, Michael C

    2010-01-01

    SEAWAT is a coupled version of MODFLOW and MT3DMS designed to simulate variable-density ground water flow and solute transport. The most recent version of SEAWAT, called SEAWAT Version 4, includes new capabilities to represent simultaneous multispecies solute and heat transport. To test the new features in SEAWAT, the laboratory experiment of Henry and Hilleke (1972) was simulated. Henry and Hilleke used warm fresh water to recharge a large sand-filled glass tank. A cold salt water boundary was represented on one side. Adjustable heating pads were used to heat the bottom and left sides of the tank. In the laboratory experiment, Henry and Hilleke observed both salt water and fresh water flow systems separated by a narrow transition zone. After minor tuning of several input parameters with a parameter estimation program, results from the SEAWAT simulation show good agreement with the experiment. SEAWAT results suggest that heat loss to the room was more than expected by Henry and Hilleke, and that multiple thermal convection cells are the likely cause of the widened transition zone near the hot end of the tank. Other computer programs with similar capabilities may benefit from benchmark testing with the Henry and Hilleke laboratory experiment.

  13. Solute and heat transport model of the Henry and Hilleke laboratory experiment

    USGS Publications Warehouse

    Langevin, C.D.; Dausman, A.M.; Sukop, M.C.

    2010-01-01

    SEAWAT is a coupled version of MODFLOW and MT3DMS designed to simulate variable-density ground water flow and solute transport. The most recent version of SEAWAT, called SEAWAT Version 4, includes new capabilities to represent simultaneous multispecies solute and heat transport. To test the new features in SEAWAT, the laboratory experiment of Henry and Hilleke (1972) was simulated. Henry and Hilleke used warm fresh water to recharge a large sand-filled glass tank. A cold salt water boundary was represented on one side. Adjustable heating pads were used to heat the bottom and left sides of the tank. In the laboratory experiment, Henry and Hilleke observed both salt water and fresh water flow systems separated by a narrow transition zone. After minor tuning of several input parameters with a parameter estimation program, results from the SEAWAT simulation show good agreement with the experiment. SEAWAT results suggest that heat loss to the room was more than expected by Henry and Hilleke, and that multiple thermal convection cells are the likely cause of the widened transition zone near the hot end of the tank. Other computer programs with similar capabilities may benefit from benchmark testing with the Henry and Hilleke laboratory experiment. Journal Compilation ?? 2009 National Ground Water Association.

  14. Turbulent transport regimes and the scrape-off layer heat flux width

    SciTech Connect

    Myra, J. R.; D'Ippolito, D. A.; Russell, D. A.

    2015-04-15

    Understanding the responsible mechanisms and resulting scaling of the scrape-off layer (SOL) heat flux width is important for predicting viable operating regimes in future tokamaks and for seeking possible mitigation schemes. In this paper, we present a qualitative and conceptual framework for understanding various regimes of edge/SOL turbulence and the role of turbulent transport as the mechanism for establishing the SOL heat flux width. Relevant considerations include the type and spectral characteristics of underlying instabilities, the location of the gradient drive relative to the SOL, the nonlinear saturation mechanism, and the parallel heat transport regime. We find a heat flux width scaling with major radius R that is generally positive, consistent with the previous findings [Connor et al., Nucl. Fusion 39, 169 (1999)]. The possible relationship of turbulence mechanisms to the neoclassical orbit width or heuristic drift mechanism in core energy confinement regimes known as low (L) mode and high (H) mode is considered, together with implications for the future experiments.

  15. Heat transport in Rayleigh-Bénard convection and angular momentum transport in Taylor-Couette flow: a comparative study.

    PubMed

    Brauckmann, Hannes J; Eckhardt, Bruno; Schumacher, Jörg

    2017-03-13

    Rayleigh-Bénard convection and Taylor-Couette flow are two canonical flows that have many properties in common. We here compare the two flows in detail for parameter values where the Nusselt numbers, i.e. the thermal transport and the angular momentum transport normalized by the corresponding laminar values, coincide. We study turbulent Rayleigh-Bénard convection in air at Rayleigh number Ra=10(7) and Taylor-Couette flow at shear Reynolds number ReS=2×10(4) for two different mean rotation rates but the same Nusselt numbers. For individual pairwise related fields and convective currents, we compare the probability density functions normalized by the corresponding root mean square values and taken at different distances from the wall. We find one rotation number for which there is very good agreement between the mean profiles of the two corresponding quantities temperature and angular momentum. Similarly, there is good agreement between the fluctuations in temperature and velocity components. For the heat and angular momentum currents, there are differences in the fluctuations outside the boundary layers that increase with overall rotation and can be related to differences in the flow structures in the boundary layer and in the bulk. The study extends the similarities between the two flows from global quantities to local quantities and reveals the effects of rotation on the transport.This article is part of the themed issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number'.

  16. Heat transport in Rayleigh-Bénard convection and angular momentum transport in Taylor-Couette flow: a comparative study

    NASA Astrophysics Data System (ADS)

    Brauckmann, Hannes J.; Eckhardt, Bruno; Schumacher, Jörg

    2017-03-01

    Rayleigh-Bénard convection and Taylor-Couette flow are two canonical flows that have many properties in common. We here compare the two flows in detail for parameter values where the Nusselt numbers, i.e. the thermal transport and the angular momentum transport normalized by the corresponding laminar values, coincide. We study turbulent Rayleigh-Bénard convection in air at Rayleigh number Ra=107 and Taylor-Couette flow at shear Reynolds number ReS=2×104 for two different mean rotation rates but the same Nusselt numbers. For individual pairwise related fields and convective currents, we compare the probability density functions normalized by the corresponding root mean square values and taken at different distances from the wall. We find one rotation number for which there is very good agreement between the mean profiles of the two corresponding quantities temperature and angular momentum. Similarly, there is good agreement between the fluctuations in temperature and velocity components. For the heat and angular momentum currents, there are differences in the fluctuations outside the boundary layers that increase with overall rotation and can be related to differences in the flow structures in the boundary layer and in the bulk. The study extends the similarities between the two flows from global quantities to local quantities and reveals the effects of rotation on the transport.

  17. Transport coefficients and heat fluxes in non-equilibrium high-temperature flows with electronic excitation

    NASA Astrophysics Data System (ADS)

    Istomin, V. A.; Kustova, E. V.

    2017-02-01

    The influence of electronic excitation on transport processes in non-equilibrium high-temperature ionized mixture flows is studied. Two five-component mixtures, N 2 / N2 + / N / N + / e - and O 2 / O2 + / O / O + / e - , are considered taking into account the electronic degrees of freedom for atomic species as well as the rotational-vibrational-electronic degrees of freedom for molecular species, both neutral and ionized. Using the modified Chapman-Enskog method, the transport coefficients (thermal conductivity, shear viscosity and bulk viscosity, diffusion and thermal diffusion) are calculated in the temperature range 500-50 000 K. Thermal conductivity and bulk viscosity coefficients are strongly affected by electronic states, especially for neutral atomic species. Shear viscosity, diffusion, and thermal diffusion coefficients are not sensible to electronic excitation if the size of excited states is assumed to be constant. The limits of applicability for the Stokes relation are discussed; at high temperatures, this relation is violated not only for molecular species but also for electronically excited atomic gases. Two test cases of strongly non-equilibrium flows behind plane shock waves corresponding to the spacecraft re-entry (Hermes and Fire II) are simulated numerically. Fluid-dynamic variables and heat fluxes are evaluated in gases with electronic excitation. In inviscid flows without chemical-radiative coupling, the flow-field is weakly affected by electronic states; however, in viscous flows, their influence can be more important, in particular, on the convective heat flux. The contribution of different dissipative processes to the heat transfer is evaluated as well as the effect of reaction rate coefficients. The competition of diffusion and heat conduction processes reduces the overall effect of electronic excitation on the convective heating, especially for the Fire II test case. It is shown that reliable models of chemical reaction rates are of great

  18. Addition of simultaneous heat and solute transport and variable fluid viscosity to SEAWAT

    USGS Publications Warehouse

    Thorne, D.; Langevin, C.D.; Sukop, M.C.

    2006-01-01

    SEAWAT is a finite-difference computer code designed to simulate coupled variable-density ground water flow and solute transport. This paper describes a new version of SEAWAT that adds the ability to simultaneously model energy and solute transport. This is necessary for simulating the transport of heat and salinity in coastal aquifers for example. This work extends the equation of state for fluid density to vary as a function of temperature and/or solute concentration. The program has also been modified to represent the effects of variable fluid viscosity as a function of temperature and/or concentration. The viscosity mechanism is verified against an analytical solution, and a test of temperature-dependent viscosity is provided. Finally, the classic Henry-Hilleke problem is solved with the new code. ?? 2006 Elsevier Ltd. All rights reserved.

  19. Classical heat transport and spontaneous fluctuations associated with a temperature filament in a magnetized plasma

    NASA Astrophysics Data System (ADS)

    Burke, Alexander Thomas

    1999-11-01

    We study electron heat transport and spontaneous fluctuations during the DC injection of an electron beam by a 3 mm diameter crystal of LaB 6 at 20 eV and 200 mA, into a magnetized plasma with an ambient magnetic field of 500-1500 G. Thermalization of the beam current and subsequent transport of the electron heat creates a filamentary region about 1 cm wide, on the order of the electron skin depth, c/wpe. This ``temperature filament'' extends along the field about 5 m into the 10 m long, 40 cm wide plasma column, with a peak temperature 5-20 times greater than the 0.2-0.5 eV temperature of the bulk plasma. The plasma density, on the order of 1 × 1012 cm-3, is unperturbed in the filament because the energy of the beam is below the ionization potential of helium. In the temperature filament, under quiescent conditions, we observe simultaneous axial and radial electron heat transport that occurs at the classically predicted rates within the limits of uncertainty in the electron temperature measurement of about 20%. This is based on a comparison of space-time measurements of the filament temperature with the prediction of a computer code developed specifically to model 2-dimensional classical electron heat conduction in the beamheated filament. Langmuir probes were used to measure the temperature profile of the filament, and the spontaneous fluctuations in the filament region. Non-classical or so-called anomalous transport is observed after the onset of fluctuations. Initially these fluctuations are highly coherent with a frequency on the order of 0.1 fci and an m = 1 spiral shape in the x-y plane, having a density fluctuation amplitude, dn/n, of 20% and a magnetic fluctuation amplitude, δB/ B, of.01%. Measurements of the transverse magnetic fluctuation vectors confirm the m = 1 nature of the mode. These fluctuations are identified as drift- Alfven waves. Later in time, a low-frequency fluctuation occurs, on the order of.02 fci, which is confined to the radial center

  20. The role of atmospheric heat transport in the seasonal carbon dioxide cycle

    NASA Technical Reports Server (NTRS)

    Pollack, James B.; Haberle, R. M.; Murphy, James R.; Schaeffer, J.

    1993-01-01

    We have carried out numerical experiments with a general circulations model (GCM) and energy balance model of the martian atmosphere to define the importance of heat transported to the polar regions in determining the amount of CO2 condensed on the surface during the fall and winter seasons and the amount sublimated during the spring and summer seasons. In so doing, we performed both sensitivity experiments, in which the dust opacity was varied over the full range of its observed values, and annual simulations, in which the dust opacity varied continuously with seasonal data, in accord with measurements taken at the Viking landers. Dust opacity represents the key variable for determining the contribution of atmospheric heat advection to the energy budget in the polar regions. The amount of heat advected to the winter polar regions increases monotonically as the dust opacity at low and middle latitudes increases. However, the increase is sharpest between optical depths of 0 and 1 tends to level off at still higher optical depths. Heat advection is more important at times of CO2 condensation than CO2 sublimation, since the temperature gradients are much steeper in the winter hemisphere than in the summer hemisphere. Because dust opacity is much higher during northern winter than during southern winter, atmospheric heat advection reduces the amount of CO2 that condenses in the north by a much larger factor than it does in the south.

  1. Evidence for increased latent heat transport during the Cretaceous (Albian) greenhouse warming

    USGS Publications Warehouse

    Ufnar, David F.; Gonzalez, Luis A.; Ludvigson, Greg A.; Brenner, Richard L.; Witzke, B.J.

    2004-01-01

    Quantitative estimates of increased heat transfer by atmospheric H 2O vapor during the Albian greenhouse warming suggest that the intensified hydrologic cycle played a greater role in warming high latitudes than at present and thus represents a viable alternative to oceanic heat transport. Sphaerosiderite ??18O values in paleosols of the North American Cretaceous Western Interior Basin are a proxy for meteoric ??18O values, and mass-balance modeling results suggest that Albian precipitation rates exceeded modern rates at both mid and high latitudes. Comparison of modeled Albian and modern precipitation minus evaporation values suggests amplification of the Albian moisture deficit in the tropics and moisture surplus in the mid to high latitudes. The tropical moisture deficit represents an average heat loss of ???75 W/m2 at 10??N paleolatitude (at present, 21 W/m2). The increased precipitation at higher latitudes implies an average heat gain of ???83 W/m2 at 45??N (at present, 23 W/m2) and of 19 W/m2 at 75??N (at present, 4 W/m2). These estimates of increased poleward heat transfer by H2O vapor during the Albian may help to explain the reduced equator-to-pole temperature gradients. ?? 2004 Geological Society of America.

  2. Fluid Transport Driven by Heat-Generating Nuclear Waste in Bedded Salt

    NASA Astrophysics Data System (ADS)

    Jordan, A.; Harp, D. R.; Stauffer, P. H.; Ten Cate, J. A.; Labyed, Y.; Boukhalfa, H.; Lu, Z.; Person, M. A.; Robinson, B. A.

    2013-12-01

    The question of where to safely dispose high-level nuclear waste (HLW) provides ample motivation for scientific research on deep geologic disposal options. The goal of this study is to model the dominant heat and mass transport processes that would be driven by heat generating nuclear waste buried in bedded salt. The interaction between liquid brine flow towards the heat source, establishment of a heat pipe in the mine-run salt backfill, boiling, and vapor condensation leads to changes in porosity, permeability, saturation, thermal conductivity, and rheology of the salt surrounding potential waste canisters. The Finite Element Heat and Mass transfer code (FEHM) was used to simulate these highly coupled thermal, hydrological, and chemical processes. The numerical model has been tested against recent and historical experimental data to develop and improve the salt material model. We used the validated numerical model to make predictions of temperature gradients, porosity changes, and tracer behavior that will be testable in a future 2-year field-scale heater experiment to be carried out in an experimental test bed at the Waste Isolation Pilot Plant (WIPP) site near Carlsbad, NM.

  3. Advective heat transport associated with regional Earth degassing in central Apennine (Italy)

    NASA Astrophysics Data System (ADS)

    Chiodini, G.; Cardellini, C.; Caliro, S.; Chiarabba, C.; Frondini, F.

    2013-07-01

    In this work we show that the main springs of the central Apennine transport a total amount of heat of ˜2.2×109 J s-1. Most of this heat (57%) is the result of geothermal warming while the remaining 43% is due to gravitational potential energy dissipation. This result indicates that a large area of the central Apennines is very hot with heat flux values >300 mW m-2. These values are higher than those measured in the magmatic and famously geothermal provinces of Tuscany and Latium and about 1/3 of the total heat discharged at Yellowstone. This finding is surprising because the central Apennines have been thought to be a relatively cold area. Translated by CO2 rich fluids, this heat anomaly suggests the existence of a thermal source such as a large magmatic intrusion at depth. Recent tomographic images of the area support the presence of such an intrusion visible as a broad negative velocity anomaly in seismic waves. Our results indicate that the thermal regime of tectonically active areas of the Earth, where meteoric waters infiltrate and deeply circulate, should be revised on the basis of mass and energy balances of the groundwater systems.

  4. Water and heat transport in hilly red soil of southern China: I. Experiment and analysis.

    PubMed

    Lu, Jun; Huang, Zhi-Zhen; Han, Xiao-Fei

    2005-05-01

    Studies on coupled transfer of soil moisture and heat have been widely carried out for decades. However, little work has been done on red soils, widespread in southern China. The simultaneous transfer of soil moisture and heat depended on soil physical properties and the climate conditions. Red soil is heavy clay and high content of free iron and aluminum oxide. The climate conditions are characterized by the clear four seasons and the serious seasonal drought. The great air temperature differences annually and diurnally result in significant fluctuation in soil temperature in top layer. The closed and evaporating columns experiments with red soil were conducted to simulate the coupled transfer of soil water and heat under the overlaying and opening fields' conditions, and to analyze the effects of soil temperature gradient on the water transfer and the effects of initial soil water contents on the transfer of soil water and heat. The closed and evaporating columns were designed similarly with about 18 degrees C temperatures differences between the top and bottom boundary, except of the upper end closed or exposed to the air, respectively. Results showed that in the closed column, water moved towards the cold end driven by temperature gradient, while the transported water decreased with the increasing initial soil water content until the initial soil water content reached to field capacity equivalent, when almost no changes for the soil moisture profile. In the evaporating column, the net transport of soil water was simultaneously driven by evaporation and temperature gradients, and the drier soil was more influenced by temperature gradient than by evaporation. In drier soil, it took a longer time for the temperature to reach equilibrium, because of more net amount of transported water.

  5. Estimating the health benefits from natural gas use in transport and heating in Santiago, Chile.

    PubMed

    Mena-Carrasco, Marcelo; Oliva, Estefania; Saide, Pablo; Spak, Scott N; de la Maza, Cristóbal; Osses, Mauricio; Tolvett, Sebastián; Campbell, J Elliott; Tsao, Tsao Es Chi-Chung; Molina, Luisa T

    2012-07-01

    Chilean law requires the assessment of air pollution control strategies for their costs and benefits. Here we employ an online weather and chemical transport model, WRF-Chem, and a gridded population density map, LANDSCAN, to estimate changes in fine particle pollution exposure, health benefits, and economic valuation for two emission reduction strategies based on increasing the use of compressed natural gas (CNG) in Santiago, Chile. The first scenario, switching to a CNG public transportation system, would reduce urban PM2.5 emissions by 229 t/year. The second scenario would reduce wood burning emissions by 671 t/year, with unique hourly emission reductions distributed from daily heating demand. The CNG bus scenario reduces annual PM2.5 by 0.33 μg/m³ and up to 2 μg/m³ during winter months, while the residential heating scenario reduces annual PM2.5 by 2.07 μg/m³, with peaks exceeding 8 μg/m³ during strong air pollution episodes in winter months. These ambient pollution reductions lead to 36 avoided premature mortalities for the CNG bus scenario, and 229 for the CNG heating scenario. Both policies are shown to be cost-effective ways of reducing air pollution, as they target high-emitting area pollution sources and reduce concentrations over densely populated urban areas as well as less dense areas outside the city limits. Unlike the concentration rollback methods commonly used in public policy analyses, which assume homogeneous reductions across a whole city (including homogeneous population densities), and without accounting for the seasonality of certain emissions, this approach accounts for both seasonality and diurnal emission profiles for both the transportation and residential heating sectors.

  6. Molecular Dynamics Simulation of DNA Capture and Transport in Heated Nanopores

    PubMed Central

    2016-01-01

    The integration of local heat sources with solid-state nanopores offers new means for controlling the transmembrane transport of charged biomacromolecules. In the case of electrophoretic transport of DNA, recent experimental studies revealed unexpected temperature dependences of the DNA capture rate, the DNA translocation velocity, and the ionic current blockades produced by the presence of DNA in the nanopore. Here, we report the results of all-atom molecular dynamics simulations that elucidated the effect of temperature on the key microscopic processes governing electric field-driven transport of DNA through nanopores. Mimicking the experimental setup, we simulated the capture and subsequent translocation of short DNA duplexes through a locally heated nanopore at several temperatures and electrolyte conditions. The temperature dependence of ion mobility at the DNA surface was found to cause the dependence of the relative conductance blockades on temperature. To the first order, the effective force on DNA in the nanopore was found to be independent of temperature, despite a considerable reduction of solution viscosity. The temperature dependence of the solution viscosity was found to make DNA translocations faster for a uniformly heated system but not in the case of local heating that does not affect viscosity of solution surrounding the untranslocated part of the molecule. Increasing solution temperature was also found to reduce the lifetime of bonds formed between cations and DNA. Using a flow suppression algorithm, we were able to separate the effects of electro-osmotic flow and direct ion binding, finding the reduced durations of DNA–ion bonds to increase, albeit weakly, the effective force experienced by DNA in an electric field. Unexpectedly, our simulations revealed a considerable temperature dependence of solvent velocity at the DNA surface—slip velocity, an effect that can alter hydrodynamic coupling between the motion of DNA and the surrounding fluid

  7. Numerical modeling of coupled thermal chemical reactive transport: simulation of a heat storage system

    NASA Astrophysics Data System (ADS)

    Shao, H.; Watanabe, N.; Singh, A. K.; Nagel, T.; Linder, M.; Woerner, A.; Kolditz, O.

    2012-12-01

    As a carbon-free energy supply technology, the operation time and final energy output of thermal solar power plants can be greatly extended if efficient thermal storage systems are applied. One of the proposed design of such system is to utilize reversible thermochemical reactions and its embedded reaction enthalpy, e.g. the Ca(OH)2/CaO hydration circle, in a fixed-bed gas-solid reactor (Schaube et al. 2011) The modeling of such a storage system involves multiple strongly-coupled physical and chemical processes. Seepage velocity is calculated by the nonlinear Forchheimer law. Gas phase density and viscosity are temperature, pressure and composition dependent. Also, heat transfer between gas and solid phases is largely influenced by the exothermal heat produced by the hydration of calcium oxide. Numerical solution of four governing PDEs include the mass balance, reactive transport, heat balance equations for gas and solid phases, which are implemented into the open source scientific software OpenGeoSys in a monolithic way. Based on it, a 2D numerical model, considering the boundary heat loss of the system, was set up to simulate the energy-storage and release circle. The high performance computing techniques were employed in two stages. First, the dynamic behavior of the heat storage system is simulated on a parallel platform. Second, a large number of processors are employed to perform sensitivity analysis, whereas the reaction rates and efficiency factor of heat transfer are parameterized so that the measured and simulated temperature profile fit with each other. The model showed that heat transfer coefficient between solid and gas phase, grain size of the filling material will influence the final performance greatly. By varying these factors, the calibrated model will be further applied to optimize the design of such energy storage system.

  8. An experimental test plan for the characterization of molten salt thermochemical properties in heat transport systems

    SciTech Connect

    Pattrick Calderoni

    2010-09-01

    Molten salts are considered within the Very High Temperature Reactor program as heat transfer media because of their intrinsically favorable thermo-physical properties at temperatures starting from 300 C and extending up to 1200 C. In this context two main applications of molten salt are considered, both involving fluoride-based materials: as primary coolants for a heterogeneous fuel reactor core and as secondary heat transport medium to a helium power cycle for electricity generation or other processing plants, such as hydrogen production. The reference design concept here considered is the Advanced High Temperature Reactor (AHTR), which is a large passively safe reactor that uses solid graphite-matrix coated-particle fuel (similar to that used in gas-cooled reactors) and a molten salt primary and secondary coolant with peak temperatures between 700 and 1000 C, depending upon the application. However, the considerations included in this report apply to any high temperature system employing fluoride salts as heat transfer fluid, including intermediate heat exchangers for gas-cooled reactor concepts and homogenous molten salt concepts, and extending also to fast reactors, accelerator-driven systems and fusion energy systems. The purpose of this report is to identify the technical issues related to the thermo-physical and thermo-chemical properties of the molten salts that would require experimental characterization in order to proceed with a credible design of heat transfer systems and their subsequent safety evaluation and licensing. In particular, the report outlines an experimental R&D test plan that would have to be incorporated as part of the design and operation of an engineering scaled facility aimed at validating molten salt heat transfer components, such as Intermediate Heat Exchangers. This report builds on a previous review of thermo-physical properties and thermo-chemical characteristics of candidate molten salt coolants that was generated as part of the

  9. Design of a pool boiler heat transport system for a 25 kWe advanced Stirling conversion system

    NASA Technical Reports Server (NTRS)

    Anderson, W. G.; Rosenfeld, J. H.; Noble, J.; Kesseli, J.

    1991-01-01

    The overall operating temperature and efficiency of solar-powered Stirling engines can be improved by adding a heat transport system to more uniformly supply heat to the heater head tubes. One heat transport system with favorable characteristics is an alkali metal pool boiler. An alkali metal pool boiler heat transport system was designed for a 25-kW advanced Stirling conversion system (ASCS). Solar energy concentrated on the absorber dome boils a eutectic mixture of sodium and potassium. The alkali metal vapors condense on the heater head tubes, supplying the Stirling engine with a uniform heat flux at a constant temperature. Boiling stability is achieved with the use of an enhanced boiling surface and noncondensible gas.

  10. The Role of Greenland on Heat and Moisture Transports Into the Arctic.

    NASA Astrophysics Data System (ADS)

    Kindig, D.; Tsukernik, M.; Serreze, M. C.

    2006-12-01

    The region between Greenland and northern Scandinavia is a primary gateway for the transport of moist static energy into the Arctic. Much of this transport is via eddies, namely synoptic scale cyclones associated with the North Atlantic storm track and Icelandic Low. The orography of Greenland strongly influences the evolution, track and behavior of cyclones in the region. Here we examine how Greenland helps to control moist static energy transports into the Arctic through experiments with the Polar MM5 regional model (MM5), forced at the boundaries by NCEP/NCAR Reanalysis data. The focus is on the winter season. Sensitivity studies are run comparing transports under control simulations (CONTROL) with those for which the orography of Greenland is removed (NO_GREEN). Monthly climatologies are built comparing CONTROL and NO_GREEN simulations for positive, negative and neutral phases of the North Atlantic Oscillation. In most NO_GREEN simulations, there are substantial changes in the longitude of peak pole-ward transports of latent and sensible heat, which can in turn be related to shifts in storm tracks and the location/intensity of the Icelandic Low. In global climate simulations with no Greenland orography, the Icelandic Low tends to shift eastward. By contrast, the MM5 NO_GREEN simulations show a westward shift in the storm track.

  11. Diffusive-to-ballistic transition of the modulated heat transport in a rarefied air chamber

    NASA Astrophysics Data System (ADS)

    Gomez-Heredia, C. L.; Macias, J.; Ordonez-Miranda, J.; Ares, O.; Alvarado-Gil, J. J.

    2017-01-01

    Modulated heat transfer in air subject to pressures from 760 Torr to 10-4 Torr is experimentally studied by means of a thermal-wave resonant cavity placed in a vacuum chamber. This is done through the analysis of the amplitude and phase delay of the photothermal signal as a function of the cavity length and pressure through of the Knudsen's number. The viscous, transitional, and free molecular regimes of heat transport are observed for pressures P>1.5 Torr, 25 mTorrheat transport.

  12. Heat transfer enhancement in a lithium-ion cell through improved material-level thermal transport

    SciTech Connect

    Vishwakarma, Vivek; Waghela, Chirag; Wei, Zi; Prasher, Ravi; Nagpure, Shrikant C.; Li, Jianlin; Liu, Fuqiang; Daniel, Claus; Jain, Ankur

    2016-09-25

    We report that while Li-ion cells offer excellent electrochemical performance for several applications including electric vehicles, they also exhibit poor thermal transport characteristics, resulting in reduced performance, overheating and thermal runaway. Inadequate heat removal from Li-ion cells originates from poor thermal conductivity within the cell. This paper identifies the rate-limiting material-level process that dominates overall thermal conduction in a Li-ion cell. Results indicate that thermal characteristics of a Li-ion cell are largely dominated by heat transfer across the cathode-separator interface rather than heat transfer through the materials themselves. This interfacial thermal resistance contributes around 88% of total thermal resistance in the cell. Measured value of interfacial resistance is close to that obtained from theoretical models that account for weak adhesion and large acoustic mismatch between cathode and separator. Further, to address this problem, an amine-based chemical bridging of the interface is carried out. This is shown to result in in four-times lower interfacial thermal resistance without deterioration in electrochemical performance, thereby increasing effective thermal conductivity by three-fold. This improvement is expected to reduce peak temperature rise during operation by 60%. Finally, by identifying and addressing the material-level root cause of poor thermal transport in Li-ion cells, this work may contribute towards improved thermal performance of Li-ion cells.

  13. Study of fast electron transport and ionization in isochorically heated solid foil

    NASA Astrophysics Data System (ADS)

    Sawada, Hiroshi; Sentoku, Yasuhiko; Pandit, Rishi; Yabuuchi, Toshinori; Zastrau, Ulf; Foerster, Eckhart; Beg, Farhat; McLean, Harry; Chen, Hui; Park, J.-B.; Patel, Prav; Link, Anthony; Ping, Yuan

    2016-10-01

    Interaction of a high-power, short-pulse laser with a solid target generates a significant number of relativistic MeV electrons, subsequently heating the target isochorically in the transport process. Fast electron driven ionization of a solid titanium foil was studied by measuring Ti K-alpha x-rays and performing 2-D particle-in-cell simulations. The experiment was performed using the 50 TW Leopard short-pulse laser at UNR's Nevada Terawatt Facility. The 15 J, 0.35 ps laser was tightly focused on to a various sized, 2- μm thick Ti foil within a 8 μm spot to achieve the peak intensity of 2×1019 W/cm2. The transport of the fast electrons produced 4.51 keV Ti K-alpha x-rays. The yields and 2-D monochromatic images were recorded with a Bragg crystal spectrometer and a spherically bent crystal imager. The ionization degree of the heated foil was determined to be 15 from the ionized K-alpha lines and the missing emission in the images. 2-D PIC simulations using a PICLS code with a radiation transport module were performed to calculate the K-alpha profiles and spectra. Details of the experiment and comparison will be presented.

  14. Exact solution of a Lévy walk model for anomalous heat transport.

    PubMed

    Dhar, Abhishek; Saito, Keiji; Derrida, Bernard

    2013-01-01

    The Lévy walk model is studied in the context of the anomalous heat conduction of one-dimensional systems. In this model, the heat carriers execute Lévy walks instead of normal diffusion as expected in systems where Fourier's law holds. Here we calculate exactly the average heat current, the large deviation function of its fluctuations, and the temperature profile of the Lévy walk model maintained in a steady state by contact with two heat baths (the open geometry). We find that the current is nonlocally connected to the temperature gradient. As observed in recent simulations of mechanical models, all the cumulants of the current fluctuations have the same system-size dependence in the open geometry. For the ring geometry, we argue that a size-dependent cutoff time is necessary for the Lévy walk model to behave like mechanical models. This modification does not affect the results on transport in the open geometry for large enough system sizes.

  15. Modeling of limiter heat loads and impurity transport in Wendelstein 7-X startup plasmas

    NASA Astrophysics Data System (ADS)

    Effenberg, Florian; Feng, Y.; Frerichs, H.; Schmitz, O.; Hoelbe, H.; Koenig, R.; Krychowiak, M.; Pedersen, T. S.; Bozhenkov, S.; Reiter, D.

    2015-11-01

    The quasi-isodynamic stellarator Wendelstein 7-X starts plasma operation in a limiter configuration. The field consists of closed magnetic flux surfaces avoiding magnetic islands in the plasma boundary. Because of the small size of the limiters and the absence of wall-protecting elements in this phase, limiter heat loads and impurity generation due to plasma surface interaction become a concern. These issues are studied with the 3D fluid plasma edge and kinetic neutral transport code EMC3-Eirene. It is shown that the 3D SOL consists of three separate helical magnetic flux bundles of different field line connection lengths. A density scan at input power of 4MW reveals a strong modulation of the plasma paramters with the connection length. The limiter peak heat fluxes drop from 14 MWm-2 down to 10 MWm-2 with raising the density from 1 ×1018m-3 to 1.9 ×1019m-3, accompanied by an increase of the heat flux channel widths λq. Radiative power losses can help to avoid thermal overloads of the limiters at the upper margin of the heating power. The power removal feasibility of the intrinsic carbon and other extrinsic light impurities via active gas injection is discussed as a preparation of this method for island divertor operation. Work supported in part by start up funds of the Department of Engineering Physics at the University of Wisconsin - Madison, USA and by the U.S. Department of Energy under grant DE-SC0013911.

  16. Numerical modeling of diffusive heat transport across magnetic islands and local stochastic field

    SciTech Connect

    Yu, Q.

    2006-06-15

    The heat diffusion across magnetic islands is studied numerically and compared with analytical results. For a single island, the enhanced radial heat diffusivity, {chi}{sub r}, due to the parallel transport along the field lines is increased over a region of about the island width w. The maximum enhanced heat conductivity at the rational surface is proportional to w{sup 2}({chi}{sub parallel}{chi}{sub perpendicular}){sup 1/2} for sufficiently high values of {chi}{sub parallel}/{chi}{sub perpendicular}, where {chi}{sub parallel}/{chi}{sub perpendicular} is the ratio between the parallel and the perpendicular heat diffusivity. For low ratios of {chi}{sub parallel}/{chi}{sub perpendicular}, however, the maximum value of {chi}{sub r} is proportional to w{sup 4}{chi}{sub parallel}. In a locally stochastic magnetic field, {chi}{sub r} is again proportional to w{sup 4}{chi}{sub parallel} for low {chi}{sub parallel}/{chi}{sub perpendicular}, which is in agreement with the analytical results. With increasing {chi}{sub parallel/}{chi}{sub perpendicular}, {chi}{sub r} is dominated first by the additive effect of individual islands and then by the field ergodicity.

  17. Nanoscale phase engineering of thermal transport with a Josephson heat modulator.

    PubMed

    Fornieri, Antonio; Blanc, Christophe; Bosisio, Riccardo; D'Ambrosio, Sophie; Giazotto, Francesco

    2016-03-01

    Macroscopic quantum phase coherence has one of its pivotal expressions in the Josephson effect, which manifests itself both in charge and energy transport. The ability to master the amount of heat transferred through two tunnel-coupled superconductors by tuning their phase difference is the core of coherent caloritronics, and is expected to be a key tool in a number of nanoscience fields, including solid-state cooling, thermal isolation, radiation detection, quantum information and thermal logic. Here, we show the realization of the first balanced Josephson heat modulator designed to offer full control at the nanoscale over the phase-coherent component of thermal currents. Our device provides magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a maximum of the flux-to-temperature transfer coefficient reaching 200 mK per flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the exact correspondence in the phase engineering of charge and heat currents, breaking ground for advanced caloritronic nanodevices such as thermal splitters, heat pumps and time-dependent electronic engines.

  18. Exact solution of a Lévy walk model for anomalous heat transport

    NASA Astrophysics Data System (ADS)

    Dhar, Abhishek; Saito, Keiji; Derrida, Bernard

    2013-01-01

    The Lévy walk model is studied in the context of the anomalous heat conduction of one-dimensional systems. In this model, the heat carriers execute Lévy walks instead of normal diffusion as expected in systems where Fourier's law holds. Here we calculate exactly the average heat current, the large deviation function of its fluctuations, and the temperature profile of the Lévy walk model maintained in a steady state by contact with two heat baths (the open geometry). We find that the current is nonlocally connected to the temperature gradient. As observed in recent simulations of mechanical models, all the cumulants of the current fluctuations have the same system-size dependence in the open geometry. For the ring geometry, we argue that a size-dependent cutoff time is necessary for the Lévy walk model to behave like mechanical models. This modification does not affect the results on transport in the open geometry for large enough system sizes.

  19. Nanoscale phase engineering of thermal transport with a Josephson heat modulator

    NASA Astrophysics Data System (ADS)

    Fornieri, Antonio; Blanc, Christophe; Bosisio, Riccardo; D'Ambrosio, Sophie; Giazotto, Francesco

    2016-03-01

    Macroscopic quantum phase coherence has one of its pivotal expressions in the Josephson effect, which manifests itself both in charge and energy transport. The ability to master the amount of heat transferred through two tunnel-coupled superconductors by tuning their phase difference is the core of coherent caloritronics, and is expected to be a key tool in a number of nanoscience fields, including solid-state cooling, thermal isolation, radiation detection, quantum information and thermal logic. Here, we show the realization of the first balanced Josephson heat modulator designed to offer full control at the nanoscale over the phase-coherent component of thermal currents. Our device provides magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a maximum of the flux-to-temperature transfer coefficient reaching 200 mK per flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the exact correspondence in the phase engineering of charge and heat currents, breaking ground for advanced caloritronic nanodevices such as thermal splitters, heat pumps and time-dependent electronic engines.

  20. A Transport Model for Non-Local Heating of Electrons in ICP Reactors

    NASA Technical Reports Server (NTRS)

    Chang, C. H.; Bose, Deepak; Arnold, James O. (Technical Monitor)

    1998-01-01

    A new model has been developed for non-local heating of electrons in ICP reactors, based on a hydrodynamic approach. The model has been derived using the electron momentum conservation in azimuthal direction with electromagnetic and frictional forces respectively as driving force and damper of harmonic oscillatory motion of electrons. The resulting transport equations include the convection of azimuthal electron momentum in radial and axial directions, thereby accounting for the non-local effects. The azimuthal velocity of electrons and the resulting electrical current are coupled to the Maxwell's relations, thus forming a self-consistent model for non-local heating. This model is being implemented along with a set of Navier-Stokes equations for plasma dynamics and gas flow to simulate low-pressure (few mTorr's) ICP discharges. Characteristics of nitrogen plasma in a TCP 300mm etch reactor is being studied. The results will be compared against the available Langmuir probe measurements.

  1. Scaling of high-field transport and localized heating in graphene transistors.

    PubMed

    Bae, Myung-Ho; Islam, Sharnali; Dorgan, Vincent E; Pop, Eric

    2011-10-25

    We use infrared thermal imaging and electrothermal simulations to find that localized Joule heating in graphene field-effect transistors on SiO(2) is primarily governed by device electrostatics. Hot spots become more localized (i.e., sharper) as the underlying oxide thickness is reduced, such that the average and peak device temperatures scale differently, with significant long-term reliability implications. The average temperature is proportional to oxide thickness, but the peak temperature is minimized at an oxide thickness of ∼90 nm due to competing electrostatic and thermal effects. We also find that careful comparison of high-field transport models with thermal imaging can be used to shed light on velocity saturation effects. The results shed light on optimizing heat dissipation and reliability of graphene devices and interconnects.

  2. Electron temperature measurements and heat transport improvement in the RFX-mod experiment.

    NASA Astrophysics Data System (ADS)

    Alfier, Alberto; Bonomo, Federica; Franz, Paolo; Marrelli, Lionello; Pasqualotto, Roberto; Piovesan, Paolo; Spizzo, Gianluca; Annibaldi, Silvia Valeria

    2007-11-01

    Electron temperature profiles at about 1keV have been measured in the RFX-mod experiment during the recent high plasma current campaign (Ip>1.2MA, ne˜4.10^19): peaked Te profiles, obtained through the Thomson scattering diagnostic, are characterized by a steep gradient in the core during the quasi-single helicity (QSH) state. The formation of well defined magnetic flux surfaces during QSH states determines a reduction of thermal heat conductivity, whose estimate is essential to quantify this transport improvement. We apply the M1TeV code [1] to various experimental scenarios in order to estimate heat diffusivity, then also calculating electron confinement time: in this study, we consider the effect of the increase of plasma current and also of eventual external current drive. [1] F.Porcelli et al., Phys. Rev. Lett. 82, 1458 (1999).

  3. Prandtl-Number Dependence of Heat Transport in Laminar Horizontal Convection.

    PubMed

    Shishkina, Olga; Wagner, Sebastian

    2016-01-15

    We report the Prandtl-number (Pr) and Rayleigh-number (Ra) dependencies of the Reynolds number (Re) and mean convective heat transport, measured by the Nusselt number (Nu), in horizontal convection (HC) systems, where the heat supply and removal are provided exclusively through a lower horizontal surface of a fluid layer. For laminar HC, we find that Re∼Ra^{2/5}Pr^{-4/5}, Nu∼Ra^{1/5}Pr^{1/10} with a transition to Re∼Ra^{1/2}Pr^{-1}, Nu∼Ra^{1/4}Pr^{0} for large Pr. The results are based on direct numerical simulations for Ra from 3×10^{8} to 5×10^{10} and Pr from 0.05 to 50 and are explained by applying the Grossmann-Lohse approach [J. Fluid Mech. 407, 27 (2000)] transferred from the case of Rayleigh-Bénard convection to the case of laminar HC.

  4. Nuclear winter - Three-dimensional simulations including interactive transport, scavenging, and solar heating of smoke

    NASA Technical Reports Server (NTRS)

    Malone, R. C.; Auer, L. H.; Glatzmaier, G. A.; Wood, M. C.; Toon, O. B.

    1986-01-01

    A reexamination is conducted of the 'nuclear winter' hypothesis with a three-dimensional global model modified to allow for localized injection of smoke, its transport by the simulated winds, its absorption of sunlight, and its removal by model-simulated precipitation. Smoke injected into the troposphere is driven upward by solar heating. The tropopause, initially above the smoke, reforms below the heat smoke layer and separates it from precipitation below. Although much smoke is scavenged while the thermal structure is being altered, the residence time of the remaining smoke is greatly increased. Particularly for July conditions, a longer-lasting 'nuclear winter' effect is observed than was found in earlier modeling studies in which normal tropospheric residence times were assumed. In January the smaller solar flux in the northern hemisphere allows faster removal of smoke than in July. Significant cooling of the northern hemisphere continents is predicted; its dependence on season and injected smoke mass is described.

  5. A possible closure relation for heat transport in the solar wind

    NASA Technical Reports Server (NTRS)

    Feldman, W. C.; Asbridge, J. R.; Bame, S. J.; Gosling, J. T.; Lemons, D. S.

    1979-01-01

    The objective of the present paper is to search for an empirical closure relation for solar wind heat transport that applies to a microscopic scale. This task is approached by using the quasi-linear wave-particle formalism proposed by Perkins (1973) as a guide to derive an equation relating the relative drift speed between core-electron and proton populations to local bulk flow conditions. The resulting relationship, containing one free parameter, is found to provide a good characterization of Los Alamos Imp electron data measuring during the period from March 1971 through August 1974. An empirical closure relation is implied by this result because of the observed proportionality between heat flux and relative drift speed.

  6. Warm-Core Intensification of a Hurricane Through Horizontal Eddy Heat Transports Inside the Eye

    NASA Technical Reports Server (NTRS)

    Braun, Scott A.; Montgomery, Michael T.; Fulton, John; Nolan, David S.

    2001-01-01

    A simulation of Hurricane Bob (1991) using the PSU/NCAR MM5 mesoscale model with a finest mesh spacing of 1.3 km is used to diagnose the heat budget of the hurricane. Heat budget terms, including latent and radiative heating, boundary layer forcing, and advection terms were output directly from the model for a 6-h period with 2-min frequency. Previous studies of warm core formation have emphasized the warming associated with gentle subsidence within the eye. The simulation of Hurricane Bob also identifies subsidence warming as a major factor for eye warming, but also shows a significant contribution from horizontal advective terms. When averaged over the area of the eye, excluding the eyewall (at least in an azimuthal mean sense), subsidence is found to strongly warm the mid-troposphere (2-9 km) while horizontal advection warms the mid to upper troposphere (5-13 km) with about equal magnitude. Partitioning of the horizontal advective terms into azimuthal mean and eddy components shows that the mean radial circulation cannot, as expected, generally contribute to this warming, but that it is produced almost entirely by the horizontal eddy transport of heat into the eye. A further breakdown of the eddy components into azimuthal wave numbers 1, 2, and higher indicates that the warming is dominated by wave number 1 asymmetries, with smaller contributions coming from higher wave numbers. Warming by horizontal eddy transport is consistent with idealized modeling of vortex Rossby waves and work is in progress to identify and clarify the role of vortex Rossby waves in warm-core intensification in both the full-physics model and idealized models.

  7. Warm-Core Intensification Through Horizontal Eddy Heat Transports into the Eye

    NASA Technical Reports Server (NTRS)

    Braun, Scott A.; Montgomery, Michael T.; Fulton, John; Nolan, David S.; Starr, David OC (Technical Monitor)

    2001-01-01

    A simulation of Hurricane Bob (1991) using the PSU/NCAR MM5 mesoscale model with a finest mesh spacing of 1.3 km is used to diagnose the heat budget of the hurricane. Heat budget terms, including latent and radiative heating, boundary layer forcing, and advection terms were output directly from the model for a 6-h period with 2-min frequency. Previous studies of warm core formation have emphasized the warming associated with gentle subsidence within the eye. The simulation of Hurricane Bob confirms subsidence warming as a major factor for eye warming, but also shows a significant contribution from horizontal advective terms. When averaged over the area of the eye, subsidence is found to strongly warm the mid-troposphere (2-9 km) while horizontal advection warms the mid to upper troposphere (5-13 km) with about equal magnitude. Partitioning of the horizontal advective terms into azimuthal mean and eddy components shows that the mean radial circulation does not, as expected, generally contribute to this warming, but that it is produced almost entirely by the horizontal eddy transport of heat into the eye. A further breakdown of the eddy components into azimuthal wave numbers 1, 2, and higher indicates that the warming is dominated by wave number 1 asymmetries, with smaller coming from higher wave numbers. Warming by horizontal eddy transport is consistent with idealized modeling of vortex Rossby waves and work is in progress to identify and clarify the role of vortex Rossby waves in warm-core intensification in both the full-physics model and idealized models.

  8. Understanding the Atmospheric Response to Ocean Heat Transport: a Model Inter-Comparison

    NASA Astrophysics Data System (ADS)

    Rose, B.

    2012-12-01

    The oceans' contribution to poleward heat transport (1 to 2 PW) is dwarfed by the atmosphere, and yet ocean heat transport (OHT) exerts a powerful climatic influence by exciting various atmospheric feedbacks. OHT drives polar-amplified greenhouse warming through a dynamical redistribution of tropospheric water vapor, and helps set the strength and position of the ITCZ. These complex responses explicitly couple tropical and extra-tropical processes, and depend on interactions between large-scale dynamics and moist physics. Considerable insights have been drawn from recent idealized experiments with aquaplanet GCMs coupled to slab oceans with prescribed OHT convergence (q-flux). However sensitivity to uncertain model parameterizations pose a barrier to deeper understanding. I will introduce a new multi-institution collaboration called the Q-flux / Aquaplanet Model Inter-comparison Project (QAquMIP), designed to test the robustness of the climatic impact of OHT and its relationship to traditional climate sensitivity. A standardized set of GCM experiments, repeated across a broad range of models, are forced by a few simple analytical q-fluxes. Experimental controls include the meridional scale of poleward OHT, strength of inter-hemispheric OHT, and zonally asymmetric equatorial heating. I will compare robust spatial patterns of temperature and precipitation changes associated with OHT forcing to those driven by CO2, and discuss the underlying spatial pattern of atmospheric feedbacks. A recurring theme is the key role of moist convection in communicating sea surface heating signals throughout the atmosphere, with consequences for clouds, water vapor, radiation, and hydrology. QAquMIP will better constrain the possible role of the oceans in past warm climates, provide a standard framework for testing new parameterizations, and advance our fundamental understanding of the moist processes contributing to present-day climate sensitivity.

  9. An Integrated Approach on Groundwater Flow and Heat/Solute Transport for Sustainable Groundwater Source Heat Pump (GWHP) System Operation

    NASA Astrophysics Data System (ADS)

    Park, D. K.; Bae, G. O.; Joun, W.; Park, B. H.; Park, J.; Park, I.; Lee, K. K.

    2015-12-01

    The GWHP system uses a stable temperature of groundwater for cooling and heating in buildings and thus has been known as one of the most energy-saving and cost-efficient renewable energy techniques. A GWHP facility was installed at an island located at the confluence of North Han and South Han rivers, Korea. Because of well-developed alluvium, the aquifer is suitable for application of this system, extracting and injecting a large amount of groundwater. However, the numerical experiments under various operational conditions showed that it could be vulnerable to thermal interference due to the highly permeable gravel layer, as a preferential path of thermal plume migration, and limited space for well installation. Thus, regional groundwater flow must be an important factor of consideration for the efficient operation under these conditions but was found to be not simple in this site. While the groundwater level in this site totally depends on the river stage control of Paldang dam, the direction and velocity of the regional groundwater flow, observed using the colloidal borescope, have been changed hour by hour with the combined flows of both the rivers. During the pumping and injection tests, the water discharges in Cheongpyeong dam affected their respective results. Moreover, the measured NO3-N concentrations might imply the effect of agricultural activities around the facility on the groundwater quality along the regional flow. It is obvious that the extraction and injection of groundwater during the facility operation will affect the fate of the agricultural contaminants. Particularly, the gravel layer must also be a main path for contaminant migration. The simulations for contaminant transport during the facility operation showed that the operation strategy for only thermal efficiency could be unsafe and unstable in respect of groundwater quality. All these results concluded that the integrated approach on groundwater flow and heat/solute transport is necessary

  10. Nodal superconductivity in FeS: Evidence from quasiparticle heat transport

    NASA Astrophysics Data System (ADS)

    Ying, T. P.; Lai, X. F.; Hong, X. C.; Xu, Y.; He, L. P.; Zhang, J.; Wang, M. X.; Yu, Y. J.; Huang, F. Q.; Li, S. Y.

    2016-09-01

    We report low-temperature heat transport measurements on superconducting iron sulfide FeS with Tc≈5 K, which has the same crystal structure and similar electronic band structure to the superconducting iron selenide FeSe. In zero magnetic field, a significant residual linear term κ0/T is observed. At low field, κ0/T increases rapidly with increasing field. These results suggest a nodal superconducting gap in FeS. We compare it with the sister compound FeSe and other iron-based superconductors with nodal gaps.

  11. Saturation of poleward atmospheric heat transport in warm climates and the low-gradient paradox.

    NASA Astrophysics Data System (ADS)

    Caballero, R.; Langen, P.

    2004-12-01

    The equable climates of the deep past featured higher atmospheric greenhouse gas concentrations, greater global-mean surface temperatures and much weaker equator-to-pole temperature contrasts than today. Climate models readily reproduce the higher mean temperatures, given sufficient increases in greenhouse gases, but they have proved incapable of matching the low meridional gradients indicated by proxy data. A crucial step in resolving this 'low-gradient paradox' is uderstanding why climate models fail to reproduce the correct feedback between global mean temperature and its meridional gradient. Though models do achieve some reduction in temperature gradients, mostly through snow and sea-ice albedo feedback, the remaining discrepancy must be accounted for by either more exotic forms of radiative forcing feedback, which are not represented in current models, or by more efficient oceanic and/or atmospheric poleward heat transports, which the models for some reason do not capture. This latter feature is especially puzzling for the atmosphere, since there are plausible reasons to expect atmospheric energy transport to be be considerably more efficient in a warmer climate. We explore this issue by systematically studying the response of atmospheric heat transpor in a GCM to a very broad range of global mean temperatures and meridional gradients. We find that heat transport increases with global mean temperature when the latter is less than about 15C; above this value, heat transport saturates, becoming insensitive to surface temperature. This behavior has a dynamical origin traceble to changes in the structure of the atmosphere's general circulation. Mean tropospheric static stability increases with surface temperature, reducing baroclinicity and suppressing storm-track eddy activity. Furthermore, as temperature increases the storm-tracks as a whole migrate poleward over cooler waters, and thus do not experience the full global-mean surface temperature increase. These

  12. Rotation drive and momentum transport with electron cyclotron heating in tokamak plasmas.

    PubMed

    Yoshida, M; Sakamoto, Y; Takenaga, H; Ide, S; Oyama, N; Kobayashi, T; Kamada, Y

    2009-08-07

    The role of electron cyclotron resonance heating (ECRH) on the toroidal rotation velocity profile has been investigated in the JT-60U tokamak device by separating the effects of the change in momentum transport, the intrinsic rotation by pressure gradient, and the intrinsic rotation by ECRH. It is found that ECRH increases the toroidal momentum diffusivity and the convection velocity. It is also found that ECRH drives the codirection (co) intrinsic rotation inside the EC deposition radius and the counterdirection (ctr) intrinsic rotation outside the EC deposition radius. This ctr rotation starts from the EC deposition radius and propagates to the edge region.

  13. Multiresonance of energy transport and absence of heat pump in a force-driven lattice.

    PubMed

    Zhang, Song; Ren, Jie; Li, Baowen

    2011-09-01

    Energy transport control in low dimensional nanoscale systems has attracted much attention in recent years. In this paper, we investigate the energy transport properties of the Frenkel-Kontorova lattice subject to a periodic driving force, in particular, the resonance behavior of the energy current by varying the external driving frequency. It is discovered that, in certain parameter ranges, multiple resonance peaks, instead of a single resonance, emerge. By comparing the nonlinear lattice model with a harmonic chain, we unravel the underlying physical mechanism for such a resonance phenomenon. Other parameter dependencies of the resonance behavior are examined as well. Finally, we demonstrate that heat pumping is actually absent in this force-driven model.

  14. Review of energy confinement and local transport scaling results in neutral-beam-heated tokamaks

    SciTech Connect

    Kaye, S.M.

    1985-05-01

    Over the past several years, tokamak neutral beam injection experiments have evolved from the brute force study of the effects of global discharge characteristics (I/sub p/, anti n/sub e/, P/sub heat/, etc.) on energy confinement to the appreciation that there are effects more subtle, yet controllable, that may influence confinement dramatically. While this evolution from first to second generation experiments is derived from an empirical understanding of low and high energy confinement modes and how to achieve them operationally, the underlying physics is still unknown. Several theories with different physical bases appear to describe the global scaling of the low confinement mode discharges quite well. On the other hand, little agreement has been found between theoretical and experimentally deduced values of local transport coefficients. While it is known operationally how to achieve any one of several types of high confinement mode discharges, here too, the underlying physics of the transport associated with these modes is poorly understood.

  15. Investigation of ion and electron heat transport of high-Te ECH heated discharges in the large helical device

    SciTech Connect

    Pablant, N. A.; Satake, S.; Yokoyama, M.; Gates, D. A.; Bitter, M.; Bertelli, N.; Delgado-Aparicio, L.; Dinklage, A.; Goto, M.; Hill, K. W.; Igamai, S.; Kubo, S.; Lazerson, S.; Matsuoka, S.; Mikkelsen, D. R.; Morita, S.; Oishi, T.; Seki, R.; Shimozuma, T.; Suzuki, C.; Suzuki, Y.; Takahashi, H.; Yamada, H.; Yoshimura, Y.

    2016-01-28

    An analysis of the radial electric field and heat transport, both for ions and electrons, is presented for a high-${{T}_{\\text{e}}}$ electron cyclotron heated (ECH) discharge on the large helical device (LHD). Transport analysis is done using the task3d transport suite utilizing experimentally measured profiles for both ions and electrons. Ion temperature and perpendicular flow profiles are measured using the recently installed x-ray imaging crystal spectrometer diagnostic (XICS), while electron temperature and density profiles are measured using Thomson scattering. The analysis also includes calculated ECH power deposition profiles as determined through the travis ray-tracing code. This is the first time on LHD that this type of integrated transport analysis with measured ion temperature profiles has been performed without NBI, allowing the heat transport properties of plasmas with only ECH heating to be more clearly examined. For this study, a plasma discharge is chosen which develops a high central electron temperature (${{T}_{\\text{eo}}}=9$ keV) at moderately low densities (${{n}_{\\text{eo}}}=1.5\\times {{10}^{19}}$ m-3). The experimentally determined transport properties from task3d are compared to neoclassical predictions as calculated by the gsrake and fortec-3d codes. The predicted electron fluxes are seen to be an order of magnitude less than the measured fluxes, indicating that electron transport is largely anomalous, while the neoclassical and measured ion heat fluxes are of the same magnitude. Neoclassical predictions of a strong positive ambipolar electric field (${{E}_{\\text{r}}}$ ) in the plasma core are validated through comparisons to perpendicular flow measurements from the XICS diagnostic. Furthermore, this provides confidence that the predictions are producing physically meaningful results for the particle fluxes and radial electric field, which are a key component in correctly predicting plasma confinement.

  16. Modification of argon impurity transport by electron cyclotron heating in KSTAR H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Hong, Joohwan; Henderson, S. S.; Kim, Kimin; Seon, C. R.; Song, Inwoo; Lee, H. Y.; Jang, Juhyeok; Park, Jae Sun; Lee, S. G.; Lee, J. H.; Lee, Seung Hun; Hong, Suk-Ho; Choe, Wonho

    2017-03-01

    Experiments with a small amount of Ar gas injection as a trace impurity were conducted in the Korea Superconducting Tokamak Advanced Research (KSTAR) H-mode plasma ({{B}\\text{T}}   =  2.8 T, {{I}\\text{P}}   =  0.6 MA, and {{P}\\text{NBI}}   =  4.0 MW). 170 GHz electron cyclotron resonance heating (ECH) at 600 and 800 kW was focused along the mid-plane with a fixed major radial position of R   =  1.66 m. The emissivity of the Ar16+ (3.949 {\\mathring{\\text{A}}} ) and Ar15+ (353.860 {\\mathring{\\text{A}}} ) spectral lines were measured by x-ray imaging crystal spectroscopy (XICS) and a vacuum UV (VUV) spectrometer, respectively. ECH reduces the peak Ar15+ emission and increases the Ar16+ emission, an effect largest with 800 kW. The ADAS-SANCO impurity transport code was used to evaluate the Ar transport coefficients. It was found that the inward convective velocity found in the plasma core without ECH was decreased with ECH, while diffusion remained approximately constant resulting in a less-peaked Ar density profile. Theoretical results from the NEO code suggest that neoclassical transport is not responsible for the change in transport, while the microstability analysis using GKW predicts a dominant ITG mode during both ECH and non-ECH plasmas.

  17. Transmission line model for strained quantum well lasers including carrier transport and carrier heating effects.

    PubMed

    Xia, Mingjun; Ghafouri-Shiraz, H

    2016-03-01

    This paper reports a new model for strained quantum well lasers, which are based on the quantum well transmission line modeling method where effects of both carrier transport and carrier heating have been included. We have applied this new model and studied the effect of carrier transport on the output waveform of a strained quantum well laser both in time and frequency domains. It has been found that the carrier transport increases the turn-on, turn-off delay times and damping of the quantum well laser transient response. Also, analysis in the frequency domain indicates that the carrier transport causes the output spectrum of the quantum well laser in steady state to exhibit a redshift which has a narrower bandwidth and lower magnitude. The simulation results of turning-on transients obtained by the proposed model are compared with those obtained by the rate equation laser model. The new model has also been used to study the effects of pump current spikes on the laser output waveforms properties, and it was found that the presence of current spikes causes (i) wavelength blueshift, (ii) larger bandwidth, and (iii) reduces the magnitude and decreases the side-lobe suppression ratio of the laser output spectrum. Analysis in both frequency and time domains confirms that the new proposed model can accurately predict the temporal and spectral behaviors of strained quantum well lasers.

  18. Ocean heat transport in a simple ocean data assimilation (SODA): Structure, mechanisms, and impacts on climate

    NASA Astrophysics Data System (ADS)

    Zheng, Yangxing

    A Simple Ocean Data Assimilation (SODA) reanalysis is used to investigate the trend and variability of global ocean heat transport for the period 1958-2004. The forecast model utilizes Parallel Ocean Program (POP) physics, with an average 0.4° (lon) x 0.25° (lat) x 40-level resolution, and is forced with ERA-40 atmospheric reanalysis from 1958 to 2001. The reanalysis is updated in a second run which is forced with QuickSCAT wind stress from 2000 to 2004. SODA uses a sequential estimation algorithm, with observations from the historical archive of hydrographic profiles supplemented by ship intake measurements, moored hydrographic observations and remotely sensed sea surface temperature. The results suggest that the interannual to decadal variability of ocean heat transport (OHT) is primarily controlled by the strength of the meridional overturning circulation (MOC), particularly in the Atlantic Ocean. The role of variation of temperature on variability of meridional OHT increases in the northern North Atlantic Ocean. Results from an analysis of the vertical structure of OHT show that most change of OHT in the oceans occurs in the upper 1000m. A heat budget analysis for the North Atlantic Ocean suggests that the long-term change of surface heat flux is principally balanced by the convergence of OHT as compared to change in the heat storage. The linear change in heat storage rate is only about one third as large as the convergence of OHT. Enhanced subtropical cells (STCs), largely affected by strengthened equatorial upwelling processes, are responsible for an intensified northward OHT in the north tropical Atlantic Ocean and a weakened northward OHT in the south tropical Atlantic Ocean. Convergence of flow due to a northward shift of the atmospheric circulation in the mid-latitude Atlantic reinforces the MOCs, which contribute to a positive trend of OHT. Finally, in the northern North Atlantic Ocean, a small increase in meridional OHT and a slight weakening of MOC

  19. The role of ocean heat transport in the habitaility of tidal-locking exoplanets around M dwarfs

    NASA Astrophysics Data System (ADS)

    Hu, Y.; Yang, J.

    2013-12-01

    The distinctive feature of tidally locked exoplanets is the very uneven heating by stellar radiation between the dayside and nightside. Previous work has focused on the role of atmospheric heat transport in preventing atmospheric collapse on the nightside for terrestrial exoplanets in the habitable zone (HZ) around M dwarfs. In the present paper, we carry out the first simulation with a fully coupled atmosphere-ocean general circulation model (AOGCM) to investigate the role of ocean heat transport in climate states of tidally locked habitable exoplanets around M dwarfs. Our simulation results demonstrate that ocean heat transport substantially extends the area of open water along the equator, showing a lobster-like spatial pattern of open water, instead of an 'eyeball'. For sufficiently high-level greenhouse gases or strong stellar radiation, ocean heat transport can even lead to complete deglaciation of the nightside. Our simulations also suggest that ocean heat transport likely narrows the width of M dwarfs' HZ. This study provides the first demonstration of the importance of exo-oceanography in determining climate states and habitability of exoplanets.

  20. Heat pipe radiators for space. [vacuum tests

    NASA Technical Reports Server (NTRS)

    Sellers, J. P.

    1977-01-01

    An optimized flight-weight prototype fluid-header panel (heatpipe radiator system) was tested in a vacuum environment over a wide range of coolant inlet temperatures, coolant flow rates, and environmental absorbed heat fluxes. The maximum performance of the system was determined. Results are compared with earlier data obtained on a smaller fluid-header feasibility panel, and computer predictions. Freeze-thaw tests are described and the change in thaw recovery time due to the addition of a low-freezing point feeder heat pipe is evaluated. Experimental panel fin-temperature distributions are compared with calculated results.

  1. A fully coupled model for water-gas-heat reactive transport with methane oxidation in landfill covers.

    PubMed

    Ng, C W W; Feng, S; Liu, H W

    2015-03-01

    Methane oxidation in landfill covers is a complex process involving water, gas and heat transfer as well as microbial oxidation. The coupled phenomena of microbial oxidation, water, gas, and heat transfer are not fully understood. In this study, a new model is developed that incorporates water-gas-heat coupled reactive transport in unsaturated soil with methane oxidation. Effects of microbial oxidation-generated water and heat are included. The model is calibrated using published data from a laboratory soil column test. Moreover, a series of parametric studies are carried out to investigate the influence of microbial oxidation-generated water and heat, initial water content on methane oxidation efficiency. Computed and measured results of gas concentration and methane oxidation rate are consistent. It is found that the coupling effects between water-gas-heat transfer and methane oxidation are significant. Ignoring microbial oxidation-generated water and heat can result in a significant difference in methane oxidation efficiency by 100%.

  2. Measurement of quasi-ballistic heat transport across nanoscale interfaces using ultrafast coherent soft x-ray beams

    SciTech Connect

    Siemens, M.; Li, Q.; Yang, R.; Nelson, K.; Anderson, E.; Murnane, M.; Kapteyn, H.

    2009-03-02

    Understanding heat transport on nanoscale dimensions is important for fundamental advances in nanoscience, as well as for practical applications such as thermal management in nano-electronics, thermoelectric devices, photovoltaics, nanomanufacturing, as well as nanoparticle thermal therapy. Here we report the first time-resolved measurements of heat transport across nanostructured interfaces. We observe the transition from a diffusive to a ballistic thermal transport regime, with a corresponding increase in the interface resistivity for line widths smaller than the phonon mean free path in the substrate. Resistivities more than three times higher than the bulk value are measured for the smallest line widths of 65 nm. Our findings are relevant to the modeling and design of heat transport in nanoscale engineered systems, including nanoelectronics, photovoltaics and thermoelectric devices.

  3. Fiber Lasers and all Optical Logic Gates for Header Processing in High-Bit Optical Networks

    NASA Astrophysics Data System (ADS)

    Barnett, Brandon Craig

    As information technologies push network capacities toward higher bit rates, fiber-optic communication networks will eventually be capable of transmitting data at a rate at which electronic switches cannot respond. A solution to this problem is to replace the electronics at the front and back ends of the transmission system where data enters and exists in optical format with all-optical header processors. In this thesis, I will describe how the header processor has been divided into all-optical switching modules, which will act as the basic building block for the header processing unit. Each module arises from the integration of an erbium -doped fiber laser and an all-optical logic gate. The erbium-doped fiber laser (EDFL) acts as a local power supply for the module. It restores the pulse shape, pulse amplitude, and timing of an incoming optical bit stream. The development of a short-pulse EDFL and a high-power EDFL for this application is described. The high-power EDFL employs a unique cavity design that eliminates multiple pulses when pumped with high powers. Data processing is performed within the module by all-optical logic gates, which switch due to the nonlinear interaction of one pulse of light with another in optical fiber. Therefore, these gates can work at the bit rate of the transmission system and avoid the bottlenecks inherent in electronic processors. The design and demonstration of a low-latency soliton-dragging gate and a low-birefringent nonlinear optical loop mirror (low-bi NOLM) logic gate are described. The two logic gates are optimized for energy contrast, switching energy, timing sensitivity, and cascadability. Logic functionality is also demonstrated. The thesis culminates in an experiment that integrates the laser and logic gate work by driving two cascaded low -bi NOLM's with an EDFL. It is shown that this experiment utilizes all the components necessary to read the header of a high-bit-rate data packet, bringing closure to the switching

  4. Integrated 10 Gb/s AWG-based correlator for multi-wavelength optical header recognition.

    PubMed

    Aljada, Muhsen; Alameh, Kamal E

    2008-03-31

    In this paper we experimentally demonstrate a novel optical correlator employing dual integrated Arrayed Waveguide Grating (AWG) in conjunction with variable delay lines. The variable delay lines provide wavelength-dependent time delays and generate a wavelength profile that matches arbitrary bit patterns, whereas the AWGs are used to demultiplex and multiplex the wavelength components of the multi-wavelength header bit pattern. The recognition of 4-bit optical patterns at different wavelengths is experimentally demonstrated at 10 Gb/s by showing that the correlator produces an autocorrelation waveform of high peak whenever the input bit pattern matches the wavelengths profile, and a low-amplitude cross-correlation function otherwise.

  5. Current & Heat Transport in Graphene Nanoribbons: Role of Non-Equilibrium Phonons

    NASA Astrophysics Data System (ADS)

    Pennington, Gary; Finkenstadt, Daniel

    2010-03-01

    The conducting channel of a graphitic nanoscale device is expected to experience a larger degree of thermal isolation when compared to traditional inversion channels of electronic devices. This leads to enhanced non-equilibrium phonon populations which are likely to adversely affect the mobility of graphene-based nanoribbons due to enhanced phonon scattering. Recent reports indicating the importance of carrier scattering with substrate surface polar optical phonons in carbon nanotubes^1 and graphene^2,3 show that this mechanism may allow enhanced heat removal from the nanoribbon channel. To investigate the effects of hot phonon populations on current and heat conduction, we solve the graphene nanoribbon multiband Boltzmann transport equation. Monte Carlo transport techniques are used since phonon populations may be tracked and updated temporally.^4 The electronic structure is solved using the NRL Tight-Binding method,^5 where carriers are scattered by confined acoustic, optical, edge and substrate polar optical phonons. [1] S. V. Rotkin et al., Nano Lett. 9, 1850 (2009). [2] J. H. Chen, C. Jang, S. Xiao, M. Ishigami and M. S. Fuhrer, Nature Nanotech. 3, 206 (2008). [3] V. Perebeinos and P. Avouris, arXiv:0910.4665v1 [cond-mat.mes-hall] (2009). [4] P. Lugli et al., Appl. Phys. Lett. 50, 1251 (1987). [5] D. Finkenstadt, G. Pennington & M.J. Mehl, Phys. Rev. B 76, 121405(R) (2007).

  6. Heat Transport Compensation in Atmosphere and Ocean over the Past 22,000 Years

    PubMed Central

    Yang, Haijun; Zhao, Yingying; Liu, Zhengyu; Li, Qing; He, Feng; Zhang, Qiong

    2015-01-01

    The Earth’s climate has experienced dramatic changes over the past 22,000 years; however, the total meridional heat transport (MHT) of the climate system remains stable. A 22,000-year-long simulation using an ocean-atmosphere coupled model shows that the changes in atmosphere and ocean MHT are significant but tend to be out of phase in most regions, mitigating the total MHT change, which helps to maintain the stability of the Earth’s overall climate. A simple conceptual model is used to understand the compensation mechanism. The simple model can reproduce qualitatively the evolution and compensation features of the MHT over the past 22,000 years. We find that the global energy conservation requires the compensation changes in the atmosphere and ocean heat transports. The degree of compensation is mainly determined by the local climate feedback between surface temperature and net radiation flux at the top of the atmosphere. This study suggests that an internal mechanism may exist in the climate system, which might have played a role in constraining the global climate change over the past 22,000 years. PMID:26567710

  7. Heat Transport and Long-Term Change in the Southern Ocean: Assessing the Role of Eddies

    NASA Astrophysics Data System (ADS)

    Gille, S. T.; Zajaczkovski, U.; Mazloff, M. R.

    2015-12-01

    Long-term change in the Southern Ocean can be difficult to evaluate because of both the paucity of historic observations and the magnitude of eddy variability. The low stratification of the Southern Ocean means that eddies detected by altimetry at the ocean surface extend through the top 2 km of the ocean. Sea surface height anomalies are more strongly correlated with sub-surface variability at depths between about 600 and 1400 dbars than they are with variability in the upper 200 dbars. Altimetric variability can thus be used to remove eddy-related anomalies from individual Argo profiles, resulting in a smoother estimate of mean temperature and salinity. This "eddy-free" mean field serves as a benchmark against which to assess decadal-scale changes in the Southern Ocean, and we use historic hydrographic data to evaluate temperature and salinity changes through the second half of the 20th century. We also evaluate the behavior of Southern Ocean eddies themselves: Although in most parts of the ocean closed oceanic eddies appear to result in thermally indirect heat transport, eddies that are carried eastward by the ACC tend to propagate in the opposite direction, resulting in thermally direct, poleward heat transport across the ACC. Evidence suggests that this cell is maintained by the effective eastward propagation of eddies relative to the mean flow at deep levels.

  8. Monitoring of the Heat and Moisture Transport through Walls of St. Martin Cathedral Tower in Bratislava

    NASA Astrophysics Data System (ADS)

    Kubičár, Ľudovít; Hudec, Ján; Fidríková, Danica; Štofanik, Vladimír; Dieška, Peter; Vretenár, Viliam

    2014-05-01

    Historic monuments are subject to degradation due to exposition to surrounding meteorological conditions and groundwater. Construction of buildings consists of the plaster and material components that have porous structure. Processes like heat transport, moisture diffusion, moisturizing and drying; freezing and thawing can be found in such structures depending on environmental conditions. Monitoring of the temperature - moisture regime gives a picture on the processes running in the structure. Long term monitoring of the tower of St. Martin Cathedral in Bratislava have been performed under window sill of the belfry in exterior in south orientation. Principle of the hot-ball method is used for monitoring of the temperature and thermal conductivity. The thermal conductivity of the porous system depends on the pore content. Moisture sensors are constructed from the parent material in a form of cylinder. Sensors are calibrated for dry and water saturated stage prior installation in the walls. Monitoring has been carried out in plaster and in the masonry in a distance about 10 cm from the wall surface, where sensors are installed. Information on temperature, moisture and thermal conductivity can be gained from measured signal. Use of two sensors allows estimation on heat and moisture transport through the wall. Monitoring has been performed in the period from April 2013 up to July 2013. Monitored data are correlated to the meteorological data. Details of various effects will be discussed.

  9. Improved estimates of global ocean circulation, heat transport and mixing from hydrographic data.

    PubMed

    Ganachaud, A; Wunsch, C

    2000-11-23

    Through its ability to transport large amounts of heat, fresh water and nutrients, the ocean is an essential regulator of climate. The pathways and mechanisms of this transport and its stability are critical issues in understanding the present state of climate and the possibilities of future changes. Recently, global high-quality hydrographic data have been gathered in the World Ocean Circulation Experiment (WOCE), to obtain an accurate picture of the present circulation. Here we combine the new data from high-resolution trans-oceanic sections and current meters with climatological wind fields, biogeochemical balances and improved a priori error estimates in an inverse model, to improve estimates of the global circulation and heat fluxes. Our solution resolves globally vertical mixing across surfaces of equal density, with coefficients in the range (3-12) x 10(-4) m2 s(-1). Net deep-water production rates amount to (15 +/- 12) x 10(6) m3 s(-1) in the North Atlantic Ocean and (21 +/- 6) x 10(6) m3 s(-1) in the Southern Ocean. Our estimates provide a new reference state for future climate studies with rigorous estimates of the uncertainties.

  10. Different spatial discretization methods of fault systems on heat transport processes in hard rock aquifers

    NASA Astrophysics Data System (ADS)

    Kruppa, Lisa; König, Christoph M.; Becker, Martin; Seidel, Torsten

    2016-04-01

    Most hard rock aquifers, which are important for geothermal use, contain fractures of different type and scale. These fault systems are of major significance for heat flow in the groundwater. The hydrogeological characterization of fault systems must therefore be part of any site investigation in hard rock aquifers and hydraulically important fault systems need to be appropriately represented in associated numerical models. This contribution discusses different spatial discretization methods of fault systems in three-dimensional groundwater models and their impact on the simulated groundwater flow field as well as density and viscosity dependent heat transport. The analysis includes a comparison of the convergence behavior and numerical stability of the different discretization methods. To ensure defendable results, the utilized numerical model SPRING was first verified against data from the Hydrocoin Level 1 Case 2 project. After verification, the software was used to evaluate the impact of different discretization strategies on steady-state and transient groundwater flow and transport model results. The results show a significant influence of the spatial discretization strategy on predicted flow rates and subsequent mass fluxes as well as energy balances.

  11. Modeling anisotropic flow and heat transport by using mimetic finite differences

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Clauser, Christoph; Marquart, Gabriele; Willbrand, Karen; Büsing, Henrik

    2016-08-01

    Modeling anisotropic flow in porous or fractured rock often assumes that the permeability tensor is diagonal, which means that its principle directions are always aligned with the coordinate axes. However, the permeability of a heterogeneous anisotropic medium usually is a full tensor. For overcoming this shortcoming, we use the mimetic finite difference method (mFD) for discretizing the flow equation in a hydrothermal reservoir simulation code, SHEMAT-Suite, which couples this equation with the heat transport equation. We verify SHEMAT-Suite-mFD against analytical solutions of pumping tests, using both diagonal and full permeability tensors. We compare results from three benchmarks for testing the capability of SHEMAT-Suite-mFD to handle anisotropic flow in porous and fractured media. The benchmarks include coupled flow and heat transport problems, three-dimensional problems and flow through a fractured porous medium with full equivalent permeability tensor. It shows firstly that the mimetic finite difference method can model anisotropic flow both in porous and in fractured media accurately and its results are better than those obtained by the multi-point flux approximation method in highly anisotropic models, secondly that the asymmetric permeability tensor can be included and leads to improved results compared the symmetric permeability tensor in the equivalent fracture models, and thirdly that the method can be easily implemented in existing finite volume or finite difference codes, which has been demonstrated successfully for SHEMAT-Suite.

  12. Giant suppression of phononic heat transport in a quantum magnet BiCu2PO6

    PubMed Central

    Jeon, Byung-Gu; Koteswararao, B.; Park, C. B.; Shu, G. J.; Riggs, S. C.; Moon, E. G.; Chung, S. B.; Chou, F. C.; Kim, Kee Hoon

    2016-01-01

    Thermal transport of quantum magnets has elucidated the nature of low energy elementary excitations and complex interplay between those excited states via strong scattering of thermal carriers. BiCu2PO6 is a unique frustrated spin-ladder compound exhibiting highly anisotropic spin excitations that contain both itinerant and localized dispersion characters along the b- and a-axes respectively. Here, we investigate thermal conductivity κ of BiCu2PO6 under high magnetic fields (H) of up to 30 tesla. A dip-feature in κ, located at ~15 K at zero-H along all crystallographic directions, moves gradually toward lower temperature (T) with increasing H, thus resulting in giant suppression by a factor of ~30 near the critical magnetic field of Hc ≅ 23.5 tesla. The giant H- and T-dependent suppression of κ can be explained by the combined result of resonant scattering of phononic heat carriers with magnetic energy levels and increased phonon scattering due to enhanced spin fluctuation at Hc, unequivocally revealing the existence of strong spin-phonon coupling. Moreover, we find an experimental indication that the remaining magnetic heat transport along the b-axis becomes almost gapless at the magnetic quantum critical point realized at Hc. PMID:27845377

  13. Coupled Water Flow and Heat Transport in Seasonally Frozen Soils with Snow Accumulation

    NASA Astrophysics Data System (ADS)

    kelleners, T.

    2013-12-01

    A numerical model is developed to calculate coupled water flow and heat transport in seasonally frozen soil and snow. Separate equations are used to describe both unsaturated and saturated soil water flow. The effect of dissolved ions on soil water freezing point depression is included by combining an expression for osmotic head with the Clapeyron equation and the van Genuchten soil water retention function. The coupled water flow and heat transport equations are solved using the Thomas algorithm and Picard iteration. Ice pressure is always assumed zero and frost heave is neglected. The new model is tested using data from an existing laboratory soil column freezing experiment and an ongoing field experiment in a high-elevation rangeland soil. A dimensionless impedance factor describing the effect of ice pore blocking on soil hydraulic conductivity is treated as a calibration parameter for both cases. Calculated values of total water content for the laboratory soil column freezing experiment compare well with measured values, especially during the early stages of the experiment, as is also found by others. Modeling statistics for the rangeland field experiment show varied performance for soil water content and excellent performance for soil temperature, in accordance with earlier results with an older version of the model.

  14. Coupled Water Flow and Heat Transport in Seasonally Frozen Soils with Snow Accumulation

    NASA Astrophysics Data System (ADS)

    King, J. M.; Kasurak, A.; Kelly, R. E.; Duguay, C. R.; Derksen, C.

    2011-12-01

    A numerical model is developed to calculate coupled water flow and heat transport in seasonally frozen soil and snow. Separate equations are used to describe both unsaturated and saturated soil water flow. The effect of dissolved ions on soil water freezing point depression is included by combining an expression for osmotic head with the Clapeyron equation and the van Genuchten soil water retention function. The coupled water flow and heat transport equations are solved using the Thomas algorithm and Picard iteration. Ice pressure is always assumed zero and frost heave is neglected. The new model is tested using data from an existing laboratory soil column freezing experiment and an ongoing field experiment in a high-elevation rangeland soil. A dimensionless impedance factor describing the effect of ice pore blocking on soil hydraulic conductivity is treated as a calibration parameter for both cases. Calculated values of total water content for the laboratory soil column freezing experiment compare well with measured values, especially during the early stages of the experiment, as is also found by others. Modeling statistics for the rangeland field experiment show varied performance for soil water content and excellent performance for soil temperature, in accordance with earlier results with an older version of the model.

  15. New insights into self-heating in double-gate transistors by solving Boltzmann transport equations

    SciTech Connect

    Thu Trang Nghiêm, T.; Saint-Martin, J.; Dollfus, P.

    2014-08-21

    Electro-thermal effects become one of the most critical issues for continuing the downscaling of electron devices. To study this problem, a new efficient self-consistent electron-phonon transport model has been developed. Our model of phonon Boltzmann transport equation (pBTE) includes the decay of optical phonons into acoustic modes and a generation term given by electron-Monte Carlo simulation. The solution of pBTE uses an analytic phonon dispersion and the relaxation time approximation for acoustic and optical phonons. This coupled simulation is applied to investigate the self-heating effects in a 20 nm-long double gate MOSFET. The temperature profile per mode and the comparison between Fourier temperature and the effective temperature are discussed. Some significant differences occur mainly in the hot spot region. It is shown that under the influence of self-heating effects, the potential profile is modified and both the drain current and the electron ballisticity are reduced because of enhanced electron-phonon scattering rates.

  16. Atmospheric Heat Transport Feedbacks to Freshwater Forcing in the Coupled GCM GISS Model

    NASA Astrophysics Data System (ADS)

    Legrande, A. N.; Schmidt, G. A.

    2005-12-01

    We perform a range of North Atlantic fresh water forcing simulations in the GISS ModelE coupled GCM. Here we present results from two sets of experiments designed to explore the sensitivity of the model to varying fresh water pulses: (1) 12 relatively small simulations emulate the magnitude and placement of 8kyr event and (2) much larger and longer PhosMIP2 hosing experiments (0.1 Sv rate and 1 Sv rate). We find that within the first set of simulations, the modeled THC response to the freshwater forcing is stochastic - the largest volume of fresh water produces neither the largest response, nor the longest perturbation of THC. We evaluate the nature of modeled THC response given (1) a range of volumes, rates, and lengths of freshwater forcing; (2) two locations of fresh water input; and (3) two base states prior to the freshwater forcing. In all simulations, reduced overturning circulation in the Atlantic results in reduced northward heat transport by the ocean (OHT); we evaluate the response of heat transport in the atmosphere (AHT) and address to what extent the rest of the climate system compensates for the reduced OHT.

  17. Numerical Modeling of Coupled Water Flow and Heat Transport in Soil and Snow

    NASA Astrophysics Data System (ADS)

    Kelleners, T.

    2015-12-01

    A numerical model is developed to calculate coupled water flow and heat transport in seasonally frozen soil and snow. Both liquid water flow and water vapor flow are included. The effect of dissolved ions on soil water freezing point depression is included by combining an expression for osmotic head with the Clapeyron equation and the van Genuchten soil water retention function. The coupled water flow and heat transport equations are solved using the Thomas algorithm and Picard iteration. Ice pressure is always assumed zero and frost heave is neglected. The new model is tested using data from a high-elevation rangeland soil that is subject to significant soil freezing and a mountainous forest soil that is snow-covered for about 8 months of the year. Soil hydraulic parameters are mostly based on measurements and only vegetation parameters are fine-tuned to match measured and calculated soil water content, soil & snow temperature, and snow height. Modeling statistics for both systems show good performance for temperature, intermediate performance for snow height, and relatively low performance for soil water content, in accordance with earlier results with an older version of the model.

  18. Giant suppression of phononic heat transport in a quantum magnet BiCu2PO6

    NASA Astrophysics Data System (ADS)

    Jeon, Byung-Gu; Koteswararao, B.; Park, C. B.; Shu, G. J.; Riggs, S. C.; Moon, E. G.; Chung, S. B.; Chou, F. C.; Kim, Kee Hoon

    2016-11-01

    Thermal transport of quantum magnets has elucidated the nature of low energy elementary excitations and complex interplay between those excited states via strong scattering of thermal carriers. BiCu2PO6 is a unique frustrated spin-ladder compound exhibiting highly anisotropic spin excitations that contain both itinerant and localized dispersion characters along the b- and a-axes respectively. Here, we investigate thermal conductivity κ of BiCu2PO6 under high magnetic fields (H) of up to 30 tesla. A dip-feature in κ, located at ~15 K at zero-H along all crystallographic directions, moves gradually toward lower temperature (T) with increasing H, thus resulting in giant suppression by a factor of ~30 near the critical magnetic field of Hc ≅ 23.5 tesla. The giant H- and T-dependent suppression of κ can be explained by the combined result of resonant scattering of phononic heat carriers with magnetic energy levels and increased phonon scattering due to enhanced spin fluctuation at Hc, unequivocally revealing the existence of strong spin-phonon coupling. Moreover, we find an experimental indication that the remaining magnetic heat transport along the b-axis becomes almost gapless at the magnetic quantum critical point realized at Hc.

  19. Investigation of inter-ELM ion heat transport in the H-mode pedestal of ASDEX Upgrade plasmas

    NASA Astrophysics Data System (ADS)

    Viezzer, E.; Fable, E.; Cavedon, M.; Angioni, C.; Dux, R.; Laggner, F. M.; Bernert, M.; Burckhart, A.; McDermott, R. M.; Pütterich, T.; Ryter, F.; Willensdorfer, M.; Wolfrum, E.; the ASDEX Upgrade Team; the EUROfusion MST1 Team

    2017-02-01

    The ion heat transport in the pedestal of H-mode plasmas is investigated in various H-mode discharges with different pedestal ion collisionalities. Interpretive modelling suggests that in all analyzed discharges the ion heat diffusivity coefficient, {χ\\text{i}} , in the pedestal is close to the neoclassical prediction within the experimental uncertainties. The impact of changing the deposition location of the electron cyclotron resonance heating on the ion heat transport has been studied. The effect on the background profiles is small. The pre-ELM (edge localized modes) edge profiles as well as the behaviour of the electron temperature and density, ion temperature and impurity toroidal rotation during the ELM cycle are very similar in discharges with on- and off-axis ECRH heating. No significant deviation of {χ\\text{i}} from neoclassics is observed when changing the ECRH deposition location to the plasma edge.

  20. Solute transport modelling in a coupled water and heat flow system applied to cold regions hydrogeology

    NASA Astrophysics Data System (ADS)

    Frampton, Andrew; Destouni, Georgia

    2016-04-01

    In cold regions, flow in the unsaturated zone is highly dynamic with seasonal variability and changes in temperature, moisture, and heat and water fluxes, all of which affect ground freeze-thaw processes and influence transport of inert and reactive waterborne substances. In arctic permafrost environments, near-surface groundwater flow is further restricted to a relatively shallow and seasonally variable active layer, confined by perennially frozen ground below. The active layer is typically partially saturated with ice, liquid water and air, and is strongly dependent on seasonal temperature fluctuations, thermal forcing and infiltration patterns. Here there is a need for improved understanding of the mechanisms controlling subsurface solute transport in the partially saturated active layer zone. Studying solute transport in cold regions is relevant to improve the understanding of how natural and anthropogenic pollution may change as activities in arctic and sub-arctic regions increase. It is also particularly relevant for understanding how dissolved carbon is transported in coupled surface and subsurface hydrological systems under climate change, in order to better understand the permafrost-hydrological-carbon climate feedback. In this contribution subsurface solute transport under surface warming and degrading permafrost conditions is studied using a physically based model of coupled cryotic and hydrogeological flow processes combined with a particle tracking method. Changes in subsurface water flows and solute transport travel times are analysed for different modelled geological configurations during a 100-year warming period. Results show that for all simulated cases, the minimum and mean travel times increase non-linearly with warming irrespective of geological configuration and heterogeneity structure. The travel time changes are shown to depend on combined warming effects of increase in pathway length due to deepening of the active layer, reduced transport

  1. Effects of heat stress on the gene expression of nutrient transporters in the jejunum of broiler chickens ( Gallus gallus domesticus)

    NASA Astrophysics Data System (ADS)

    Sun, Xiaolei; Zhang, Haichao; Sheikhahmadi, Ardashir; Wang, Yufeng; Jiao, Hongchao; Lin, Hai; Song, Zhigang

    2015-02-01

    In broiler chickens, heat stress disrupts nutrient digestion and absorption. However, the underlying molecular mechanism is not clearly understood. Hence, to investigate the effects of high ambient temperatures on the expression levels of nutrient transporters in the jejunum of broiler chickens, seventy-two 35-day-old male broiler chickens with similar body weights were randomly allocated into two groups: control (24 ± 1 °C) and heat-stressed (32 ± 1 °C). The chickens in the heat-stressed group were exposed to 10 h of heat daily from 08:00 to 18:00 and then raised at 24 ± 1 °C. The rectal temperature and feed intake of the chickens were recorded daily. After 7 days, nine chickens per group were sacrificed by exsanguination, and the jejunum was collected. The results show that heat exposure significantly decreased the feed intake and increased the rectal temperature of the broiler chickens. The plasma concentrations of uric acid and triglyceride significantly increased and decreased, respectively, in the heat-stressed group. No significant differences in the levels of plasma glucose, total amino acids, and very low-density lipoprotein were observed between the heat-stressed and control groups. However, the plasma concentration of glucose tended to be higher ( P = 0.09) in the heat-stressed group than in the control group. Heat exposure did not significantly affect the mRNA levels of Na+-dependent glucose transporter 1 and amino acid transporters y + LAT1, CAT1, r-BAT, and PePT-1. However, the expression levels of GLUT-2, FABP1, and CD36 were significantly decreased by heat exposure. The results of this study provide new insights into the mechanisms by which heat stress affects nutrient absorption in broiler chickens. Our findings suggest that periodic heat exposure might alter the jejunal glucose and lipid transport rather than amino acid transport. However, intestinal epithelial damage and cell loss should be considered when interpreting the effects of heat

  2. Effects of heat stress on the gene expression of nutrient transporters in the jejunum of broiler chickens (Gallus gallus domesticus).

    PubMed

    Sun, Xiaolei; Zhang, Haichao; Sheikhahmadi, Ardashir; Wang, Yufeng; Jiao, Hongchao; Lin, Hai; Song, Zhigang

    2015-02-01

    In broiler chickens, heat stress disrupts nutrient digestion and absorption. However, the underlying molecular mechanism is not clearly understood. Hence, to investigate the effects of high ambient temperatures on the expression levels of nutrient transporters in the jejunum of broiler chickens, seventy-two 35-day-old male broiler chickens with similar body weights were randomly allocated into two groups: control (24 ± 1 °C) and heat-stressed (32 ± 1 °C). The chickens in the heat-stressed group were exposed to 10 h of heat daily from 08:00 to 18:00 and then raised at 24 ± 1 °C. The rectal temperature and feed intake of the chickens were recorded daily. After 7 days, nine chickens per group were sacrificed by exsanguination, and the jejunum was collected. The results show that heat exposure significantly decreased the feed intake and increased the rectal temperature of the broiler chickens. The plasma concentrations of uric acid and triglyceride significantly increased and decreased, respectively, in the heat-stressed group. No significant differences in the levels of plasma glucose, total amino acids, and very low-density lipoprotein were observed between the heat-stressed and control groups. However, the plasma concentration of glucose tended to be higher (P = 0.09) in the heat-stressed group than in the control group. Heat exposure did not significantly affect the mRNA levels of Na(+)-dependent glucose transporter 1 and amino acid transporters y + LAT1, CAT1, r-BAT, and PePT-1. However, the expression levels of GLUT-2, FABP1, and CD36 were significantly decreased by heat exposure. The results of this study provide new insights into the mechanisms by which heat stress affects nutrient absorption in broiler chickens. Our findings suggest that periodic heat exposure might alter the jejunal glucose and lipid transport rather than amino acid transport. However, intestinal epithelial damage and cell loss should be considered when interpreting

  3. Hydrothermal Heat Transport within an Abruptly Formed Permeable Slot: An Application to Heat Flow Peaks Observed at the Japan Trench Offshore of Sanriku

    NASA Astrophysics Data System (ADS)

    Kawada, Y.; Yamano, M.

    2015-12-01

    Anomalous heat flow has been observed within 150 km seaward of the trench axis at the Japan Trench offshore of Sanriku, northeast Japan [Yamano et al., 2008, 2014]. The average heat flow is ~70 mW/m2 (50 mW/m2 is expected for the plate age), and small-scale (2 to 3 km) variations, whose peak value is >100 mW/m2, are embedded. In the area of high heat flow, a high Vp/Vs layer in the oceanic crust has been detected [Fujie et al., 2013]. The layer thickness is increased toward the trench axis. Fujie et al.[2013] interpreted this layer as a result of fracturing due to bending of the subducting plate. This layer may work as an aquifer in which heat is transported by fluid circulation. In a previous study [Kawada et al., 2014], we constructed a model for aquifer thickening in order to explain the observed anomalous heat flow: a 500-m-thick aquifer 150 km seaward of the trench axis is gradually thickened to 3000 m toward the trench axis. We found that hydrothermal circulation within the thickening aquifer mines heat beneath its underlying part, and heat flow is elevated accordingly. Although the model can explain the observed high heat flow in an average sense, the origin of the small-scale heat flow variations remains to be solved. This study expands the previous model by incorporating abrupt thickening of the aquifer to account for the small-scale heat flow. Typically, we consider a situation in which a permeable slot of 2000 m wide and 3000 m deep suddenly appears. This model results in a high heat flow peak of 100 mW/m2 above the permeable slot, which persists over hundreds of thousand years. Heat outside the slot is transported horizontally toward the slot by thermal conduction and then is transported vertically due to hydrothermal circulation within the slot. Because the volume of the permeable slot is smaller than its surrounding region, high heat flow above the slot lasts for a long time.

  4. Heat Stress Reduces Intestinal Barrier Integrity and Favors Intestinal Glucose Transport in Growing Pigs

    PubMed Central

    Pearce, Sarah C.; Mani, Venkatesh; Boddicker, Rebecca L.; Johnson, Jay S.; Weber, Thomas E.; Ross, Jason W.; Rhoads, Robert P.; Baumgard, Lance H.; Gabler, Nicholas K.

    2013-01-01

    Excessive heat exposure reduces intestinal integrity and post-absorptive energetics that can inhibit wellbeing and be fatal. Therefore, our objectives were to examine how acute heat stress (HS) alters intestinal integrity and metabolism in growing pigs. Animals were exposed to either thermal neutral (TN, 21°C; 35–50% humidity; n = 8) or HS conditions (35°C; 24–43% humidity; n = 8) for 24 h. Compared to TN, rectal temperatures in HS pigs increased by 1.6°C and respiration rates by 2-fold (P<0.05). As expected, HS decreased feed intake by 53% (P<0.05) and body weight (P<0.05) compared to TN pigs. Ileum heat shock protein 70 expression increased (P<0.05), while intestinal integrity was compromised in the HS pigs (ileum and colon TER decreased; P<0.05). Furthermore, HS increased serum endotoxin concentrations (P = 0.05). Intestinal permeability was accompanied by an increase in protein expression of myosin light chain kinase (P<0.05) and casein kinase II-α (P = 0.06). Protein expression of tight junction (TJ) proteins in the ileum revealed claudin 3 and occludin expression to be increased overall due to HS (P<0.05), while there were no differences in claudin 1 expression. Intestinal glucose transport and blood glucose were elevated due to HS (P<0.05). This was supported by increased ileum Na+/K+ ATPase activity in HS pigs. SGLT-1 protein expression was unaltered; however, HS increased ileal GLUT-2 protein expression (P = 0.06). Altogether, these data indicate that HS reduce intestinal integrity and increase intestinal stress and glucose transport. PMID:23936392

  5. Moisture sorption kinetics for water-soluble substances. I: Theoretical considerations of heat transport control.

    PubMed

    Van Campen, L; Amidon, G L; Zografi, G

    1983-12-01

    A model based on heat transport control was developed to describe the uptake of water on a deliquescent solid in an atmosphere of pure water vapor. The model assumes the presence of a saturated liquid film on the surface of the solid. The decrease in the vapor pressure of water over the surface, brought about by the colligative effect of solid dissolved in the liquid film, is effectively offset by the increase in temperature of the film (and the solid) caused by the heat released on condensation of the water vapor. The thermal transients die out quickly and a steady-state analysis is valid. At steady state the temperature of the liquid film (and solid) is that temperature at which the vapor pressure of water above the saturated solution is equal to the chamber pressure. Consequently, water uptake occurs at a rate that depends on the heat flux away from the surface. The water uptake rate, W'h, is constant at a given relative humidity and is described by an equation of the form W'h = (C + F) . ln (RHi/RHo), where C and F are conductive and radiative coefficients, RHi the chamber relative humidity, and RHo the relative humidity at and above which continuous water uptake (deliquescence) occurs. The model contains no adjustable parameters and can thus be directly tested against experimental results.

  6. Pool boiler heat transport system for a 25 kWe advanced Stirling conversion system

    NASA Technical Reports Server (NTRS)

    Anderson, W. G.; Rosenfeld, J. H.; Saaski, E. L.; Noble, J.; Tower, L.

    1990-01-01

    Experiments to determine alkali metal/enhanced surface combinations that have stable boiling at the temperatures and heat fluxes that occur in the Stirling engine are reported. Two enhanced surfaces and two alkali metal working fluids were evaluated. The enhanced surfaces were an EDM hole covered surface and a sintered-powder-metal porous layer surface. The working fluids tested were potassium and eutectic sodium-potasium alloy (NaK), both with and without undissolved noncondensible gas. Noncondensible gas (He and Xe) was added to the system to provide gas in the nucleation sites, preventing quenching of the sites. The experiments demonstrated the potential of an alkali metal pool boiler heat transport system for use in a solar-powered Stirling engine. The most favorable fluid/surface combination tested was NaK boiling on a -100 +140 mesh 304L stainless steel sintered porous layer with no undissolved noncondensible gas. This combination provided stable, high-performance boiling at the operating temperature of 700 C. Heat fluxes into the system ranged from 10 to 50 W/sq cm. The transition from free convection to nucleate boiling occurred at temperatures near 540 C. Based on these experiments, a pool boiler was designed for a full-scale 25-kWe Stirling system.

  7. Transport properties, specific heat and thermal conductivity of GaN nanocrystalline ceramic

    SciTech Connect

    Sulkowski, Czeslaw; ChuchmaLa, Andrzej; Zaleski, Andrzej J.; Matusiak, Marcin; Mucha, Jan; GLuchowski, PaweL; Strek, WiesLaw

    2010-10-15

    The structural and transport properties (resistivity, thermopower and Hall effect), specific heat and thermal conductivity have been measured for GaN nanocrystalline ceramic prepared by hot pressing. It was found that the temperature dependence of resistivity in temperature range 10-300 K shows the very low activation energy, which is ascribed to the shallow donor doping originating in amorphous phase of sample. The major charge carriers are electrons, what is indicated by negative sign of Hall constant and Seebeck coefficient. The thermopower attains large values (-58 {mu}V/K at 300 K) and was characterized by linear temperature dependence which suggests the diffusion as a major contribution to Seebeck effect. The high electron concentration of 1.3x10{sup 19} cm{sup -3} and high electronic specific heat coefficient determined to be 2.4 mJ/molK{sup 2} allow to conclude that GaN ceramic demonstrates the semimetallic-like behavior accompanied by very small mobility of electrons ({approx}0.1 cm{sup 2}/V s) which is responsible for its high resistivity. A low heat conductivity of GaN ceramics is associated with partial amorphous phase of GaN grains due to high pressure sintering. - Graphical Abstract: Thermal resistivity and thermopower measurements indicates the high phonon scattering and lack of phonon-drag contribution to thermopower in GaN nanoceramics pressed under 4 GPa at 800 {sup o}C.

  8. Palm cooling to reduce heat strain in subjects during simulated armoured vehicle transport.

    PubMed

    Kuennen, Matthew R; Gillum, Trevor L; Amorim, Fabiano T; Kwon, Young Sub; Schneider, Suzanne M

    2010-04-01

    This study examined whether palm cooling (PC) could reduce heat strain, measured through changes in core, mean skin, mean body temperatures, and thermal sensation in resting hyperthermic subjects wearing chemical protective garments. Ten male subjects performed three exercise bouts (6.1 km h(-1), 2-4% grade) in a hot, dry environment [mean (SD) air temperature 42.2 (0.5 degrees C), relative humidity 36.5 (1%)] until core temperature reached 38.8 degrees C. Subjects then simulated transport in an armoured vehicle by resting in a seated position for 50 min with either no cooling (NC), (PC at 10 degrees C) or palm cooling with vacuum application around the hand (PCVAC, 10 degrees C, 7.47 kPa negative pressure). Core, skin, and mean body temperatures with PC and PCVAC were lower (P < 0.05) than NC from 15 to 50 min of cooling, and thermal sensation was lower (P < 0.05) from 30 to 50 min, with no differences in any variables between PC and PCVAC. Maximal heat extraction averaged 42 (12 W), and core temperature was reduced by 0.38 (0.21 degrees C) after 50 min of PC. Heat extraction with PC was modest compared to other cooling approaches in the literature.

  9. Effects of molecular structure on microscopic heat transport in chain polymer liquids

    SciTech Connect

    Matsubara, Hiroki Kikugawa, Gota; Ohara, Taku; Bessho, Takeshi; Yamashita, Seiji

    2015-04-28

    In this paper, we discuss the molecular mechanism of the heat conduction in a liquid, based on nonequilibrium molecular dynamics simulations of a systematic series of linear- and branched alkane liquids, as a continuation of our previous study on linear alkane [T. Ohara et al., J. Chem. Phys. 135, 034507 (2011)]. The thermal conductivities for these alkanes in a saturated liquid state at the same reduced temperature (0.7T{sub c}) obtained from the simulations are compared in relation to the structural difference of the liquids. In order to connect the thermal energy transport characteristics with molecular structures, we introduce the new concept of the interatomic path of heat transfer (atomistic heat path, AHP), which is defined for each type of inter- and intramolecular interaction. It is found that the efficiency of intermolecular AHP is sensitive to the structure of the first neighbor shell, whereas that of intramolecular AHP is similar for different alkane species. The dependence of thermal conductivity on different lengths of the main and side chain can be understood from the natures of these inter- and intramolecular AHPs.

  10. Criteria for local equilibrium in a system with transport of heat and mass

    NASA Astrophysics Data System (ADS)

    Hafskjold, Bjørn; Ratkje, Signe Kjelstrup

    1995-01-01

    Nonequilibrium molecular dynamics is used to compute the coupled heat and mass transport in a binary isotope mixture of particles interacting with a Lennard-Jones/spline potential. Two different stationary states are studied, one with a fixed internal energy flux and zero mass flux, and the other with a fixed diffusive mass flux and zero temperature gradient. Computations are made for one overall temperature, T=2, and three overall number densities, n=0.1, 0.2, and 0.4. (All numerical values are given in reduced, Lennard-Jones units unless otherwise stated.) Temperature gradients are up to ∇ T=0.09 and weight-fraction gradients up to ∇ w 1=0.007. The flux-force relationships are found to be linear over the entire range. All four transport coefficients (the L-matrix) are determined and the Onsager reciprocal relationship for the off-diagonal coefficients is verified. Four different criteria are used to analyze the concept of local equilibrium in the nonequilibrium system. The local temperature fluctuation is found to be δ T≈0.03 T and of the same order as the maximum temperature difference across the control volume, except near the cold boundary. A comparison of the local potential energy, enthalpy, and pressure with the corresponding equilibrium values at the same temperature, density, and composition also verifies that local equilibrium is established, except near the boundaries of the system. The velocity contribution to the Boltzmann H-function agrees with its Maxwellian (equilibrium) value within 1%, except near the boundaries, where the deviation is up to 4%. Our results do not support the Eyring-type transport theory involving jumps across energy barriers; we find that its estimates for the heat and mass fluxes are wrong by at least one order of magnitude.

  11. Energy Transport Effects in Flaring Atmospheres Heated by Mixed Particle Beams

    NASA Astrophysics Data System (ADS)

    Zharkova, Valentina; Zharkov, Sergei; Macrae, Connor; Druett, Malcolm; Scullion, Eamon

    2016-07-01

    We investigate energy and particle transport in the whole flaring atmosphere from the corona to the photosphere and interior for the flaring events on the 1st July 2012, 6 and 7 September 2011 by using the RHESSI and SDO instruments as well as high-resolution observations from the Swedish 1-metre Solar Telescope (SST3) CRISP4 (CRisp Imaging Spectro-polarimeter). The observations include hard and soft X-ray emission, chromospheric emission in both H-alpha 656.3 nm core and continuum, as well as, in the near infra-red triplet Ca II 854.2 nm core and continuum channels and local helioseismic responses (sunquakes). The observations are compared with the simulations of hard X-ray emission and tested by hydrodynamic simulations of flaring atmospheres of the Sun heated by mixed particle beams. The temperature, density and macro-velocity variations of the ambient atmospheres are calculated for heating by mixed beams and the seismic response of the solar interior to generation of supersonic shocks moving into the solar interior. We investigate the termination depths of these shocks beneath the quiet photosphere levels and compare them with the parameters of seismic responses in the interior, or sunquakes (Zharkova and Zharkov, 2015). We also present an investigation of radiative conditions modelled in a full non-LTE approach for hydrogen during flare onsets with particular focus on Balmer and Paschen emission in the visible, near UV and near IR ranges and compare them with observations. The links between different observational features derived from HXR, optical and seismic emission are interpreted by different particle transport models that will allow independent evaluation of the particle transport scenarios.

  12. 2-D numerical simulations of groundwater flow, heat transfer and 4He transport — implications for the He terrestrial budget and the mantle helium heat imbalance

    NASA Astrophysics Data System (ADS)

    Castro, Maria Clara; Patriarche, Delphine; Goblet, Patrick

    2005-09-01

    Because helium and heat production results from a common source, a continental 4He crustal flux of 4.65 * 10 - 14 mol m - 2 s - 1 has been estimated based on heat flow considerations. In addition, because the observed mantle He / heat flux ratio at the proximity of mid-ocean ridges (6.6 * 10 - 14 mol J - 1 ) is significantly lower than the radiogenic production ratio (1.5 * 10 - 12 mol J - 1 ), the presence of a terrestrial helium-heat imbalance was suggested. The latter could be explained by the presence of a layered mantle in which removal of He is impeded from the lower mantle [R.K. O'Nions, E.R. Oxburgh, Heat and helium in the Earth, Nature 306 (1983) 429-431; E.R. Oxburgh, R.K. O'Nions, Helium loss, tectonics, and the terrestrial heat budget, Science 237 (1987) 1583-1588]. van Keken et al. [P.E. van Keken, C.J. Ballentine, D. Porcelli, A dynamical investigation of the heat and helium imbalance, Earth Planet, Sci. Lett. 188 (2001) 421-434] have recently claimed that the helium-heat imbalance remains a robust observation. Such conclusions, however, were reached under the assumption that a steady-state regime was in place for both tracers and that their transport properties are similar at least in the upper portion of the crust. Here, through 2-D simulations of groundwater flow, heat transfer and 4He transport carried out simultaneously in the Carrizo aquifer and surrounding formations in southwest Texas, we assess the legitimacy of earlier assumptions. Specifically, we show that the driving transport mechanisms for He and heat are of a fundamentally different nature for a high range of permeabilities ( k ≤ 10 - 16 m 2) found in metamorphic and volcanic rocks at all depths in the crust. The assumption that transport properties for these two tracers are similar in the crust is thus unsound. We also show that total 4He / heat flux ratios lower than radiogenic production ratios do not reflect a He deficit in the crust or mantle original reservoir. Instead, they

  13. Coupled electrochemical and heat/mass transport characteristics in passive direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Chen, Rong

    This thesis presents both experimental and theoretical investigations of coupled heat/mass transfer and electrochemical characteristics in the passive DMFC. Unlike active fuel cells, which can be operated under stabilized operating conditions, the discharging behavior of the passive DMFC usually varies with time, as the methanol concentration in the fuel reservoir decreases with time. This poses a difficulty in characterizing the performance of the passive DMFC under relatively stable operating conditions. In this work, we found that the performance of the passive DMFC became relatively stable as the cell operating temperature rose to a relatively stable value. This finding indicates that the performance of the passive DMFC can be characterized by collecting polarization data at the instance when the cell operating temperature under the open-circuit condition rises to a relatively stable value. With this proposed standard of passive DMFC performance characterization, the effects of two important parameters, including methanol concentration and cell orientation, on the passive DMFC performance were then investigated. It is found that the cell performance increased with methanol concentration. Unlike previous studies that attributed the improved performance as a result of increasing methanol concentration to the reduced anode mass transport polarization, our experimental results revealed that the improved cell performance was primarily due to the increased cell operating temperature as a result of the increased rate of methanol crossover with high methanol concentration operation. We also found that the performance was sensitive to the cell orientation. The vertical operation always yielded better performance than did the horizontal operation. This can be attributed to the increased operating temperature as a result of a higher rate of methanol crossover, which resulted from the stronger natural convection in the vertical orientation. These parametric studies

  14. Effect of heat stress on amino acid digestibility and transporters in meat-type chickens.

    PubMed

    Habashy, W S; Milfort, M C; Adomako, K; Attia, Y A; Rekaya, R; Aggrey, S E

    2017-03-02

    The present study was conducted to investigate the effect of heat stress (HS) on performance, digestibility, and molecular transporters of amino acids in broilers. Cobb 500 chicks were raised from hatch till 13 d in floor pens. At d 14, 48 birds were randomly and equally divided between a control group (25°C) and a HS treatment group (35°C). Birds in both treatment classes were individually caged and fed ad libitum on a diet containing 18.7% CP and 3,560 Kcal ME/Kg. Five birds per treatment at one and 12 d post treatment were euthanized and the Pectoralis major (P. major) and ileum were sampled for gene expression analysis. At d 33, ileal contents were collected and used for digestibility analysis. Broilers under HS had reduced growth and feed intake compared to controls. Although the apparent ileal digestibility (AID) was consistently higher for all amino acids in the HS group, it was not significant except for hydroxylysine. The amino acid consumption and retention were significantly lower in the HS group when compared to the control group. Meanwhile, the retention of amino acids per BWG was higher in the HS group when compared to the control group except for hydroxylysine and ornithine. The dynamics of amino acid transporters in the P. major and ileum was influenced by HS. In P. major and ileum tissues at d one, transporters SNAT1, SNAT2, SNAT7, TAT1, and b0,+AT, were down-regulated in the HS group. Meanwhile, LAT4 and B0AT were down-regulated only in the P. major in the treatment group. The amino acid transporters B0AT and SNAT7 at d 12 post HS were down-regulated in the P. major and ileum, but SNAT2 was down-regulated only in the ileum and TAT1 was down-regulated only in the P. major compared with the control group. These changes in amino acid transporters may explain the reduced growth in meat type chickens under heat stress.

  15. Relativistic electron beam transport through cold and shock-heated carbon samples from aerogel to diamond

    NASA Astrophysics Data System (ADS)

    Krauland, C. M.; Wei, M.; Zhang, S.; Santos, J.; Nicolai, P.; Theobald, W.; Kim, J.; Forestier-Colleoni, P.; Beg, F.

    2016-10-01

    Understanding the transport physics of a relativistic electron beam in various plasma regimes is crucial for many high-energy-density applications, such as fast heating for advanced ICF schemes and ion sources. Most short pulse laser-matter interaction experiments for transport studies have been performed with initially cold targets where the resistivity is far from that in warm dense plasmas. We present three experiments that have been performed on OMEGA EP in order to extend fast electron transport and energy coupling studies in pre-assembled plasmas from different carbon samples. Each experiment has used one 4 ns long pulse UV beam (1014 W/cm2) to drive a shockwave through the target and a 10 ps IR beam (1019 W/cm2) to create an electron beam moving opposite the shock propagation direction. These shots were compared with initially cold target shots without the UV beam. We fielded three different samples including 340 mg/cc CRF foam, vitreous carbon at 1.4 g/cc, and high density carbon at 3.4 g/cc. Electrons were diagnosed via x-ray fluorescence measurements from a buried Cu tracer in the target, as well as bremsstrahlung emission and escaped electrons reaching an electron spectrometer. Proton radiograph was also performed in the foam shots. Details of each experiment, available data and particle-in-cell simulations will be presented. This work is supported by US DOE NLUF Program, Grant Number DE-NA0002728.

  16. Coupled turbulent flow, heat, and solute transport in continuous casting processes

    NASA Astrophysics Data System (ADS)

    Aboutalebi, M. Reza; Hasan, M.; Guthrie, R. I. L.

    1995-08-01

    A fully coupled fluid flow, heat, and solute transport model was developed to analyze turbulent flow, solidification, and evolution of macrosegregation in a continuous billet caster. Transport equations of total mass, momentum, energy, and species for a binary iron-carbon alloy system were solved using a continuum model, wherein the equations are valid for the solid, liquid, and mushy zones in the casting. A modified version of the low-Reynolds number k-ɛ model was adopted to incorporate turbulence effects on transport processes in the system. A control-volume-based finite-difference procedure was employed to solve the conservation equations associated with appropriate boundary conditions. Because of high nonlinearity in the system of equations, a number of techniques were used to accelerate the convergence process. The effects of the parameters such as casting speed, steel grade, nozzle configuration on flow pattern, solidification profile, and carbon segregation were investigated. From the computed flow pattern, the trajectory of inclusion particles, as well as the density distribution of the particles, was calculated. Some of the computed results were compared with available experimental measurements, and reasonable agreements were obtained.

  17. MHD Modeling of the Solar Wind with Turbulence Transport and Heating

    NASA Technical Reports Server (NTRS)

    Goldstein, M. L.; Usmanov, A. V.; Matthaeus, W. H.; Breech, B.

    2009-01-01

    We have developed a magnetohydrodynamic model that describes the global axisymmetric steady-state structure of the solar wind near solar minimum with account for transport of small-scale turbulence associated heating. The Reynolds-averaged mass, momentum, induction, and energy equations for the large-scale solar wind flow are solved simultaneously with the turbulence transport equations in the region from 0.3 to 100 AU. The large-scale equations include subgrid-scale terms due to turbulence and the turbulence (small-scale) equations describe the effects of transport and (phenomenologically) dissipation of the MHD turbulence based on a few statistical parameters (turbulence energy, normalized cross-helicity, and correlation scale). The coupled set of equations is integrated numerically for a source dipole field on the Sun by a time-relaxation method in the corotating frame of reference. We present results on the plasma, magnetic field, and turbulence distributions throughout the heliosphere and on the role of the turbulence in the large-scale structure and temperature distribution in the solar wind.

  18. Effect of heat stress and feeding phosphorus levels on pig electron transport chain gene expression.

    PubMed

    Weller, M M D C A; Alebrante, L; Campos, P H R F; Saraiva, A; Silva, B A N; Donzele, J L; Oliveira, R F M; Silva, F F; Gasparino, E; Lopes, P S; Guimarães, S E F

    2013-12-01

    The purpose of this study was to evaluate the effect of temperature and different levels of available phosphorus (aP) on the expression of nine genes encoding electron transport chain proteins in the Longissimus dorsi (LD) muscle of pigs. Two trials were carried out using 48 high-lean growth pigs from two different growth phases: from 15 to 30 kg (phase 1) and from 30 to 60 kg (phase 2). Pigs from growth phase 1 were fed with three different levels of dietary aP (0.107%, 0.321% or 0.535%) and submitted either to a thermoneutral (24°C and RH at 76%) or to a heat stress (34°C and RH at 70%) environment. Pigs from growth phase 2 were fed with three different levels of dietary aP (0.116%, 0.306% or 0.496%) and submitted either to a thermoneutral (22ºC and RH at 77%) or to a heat stress (32ºC and RH at 73%) environment. Heat stress decreased (P<0.001) average daily feed intake at both growth phases. At 24°C, pigs in phase 1 fed the 0.321% aP diet had greater average daily gain and feed conversion (P<0.05) than those fed the 0.107% or 0.535% while, at 34°C pigs fed the 0.535% aP had the best performance (P<0.05). Pigs from phase 2 fed the 0.306% aP had best performance in both thermal environments. Gene expression profile was analyzed by quantitative real-time polymerase chain reaction. Irrespective of growing phase, the expression of six genes was lower (P<0.05) at high temperature than at thermoneutrality. The lower expression of these genes under high temperatures evidences the effects of heat stress by decreasing oxidative metabolism, through adaptive physiological mechanisms in order to reduce heat production. In pigs from phase 1, six genes were differentially expressed across aP levels (P<0.05) in the thermoneutral and one gene in the heat stress. In pigs from phase 2, two genes were differentially expressed across aP levels (P<0.05) in both thermal environments. These data revealed strong evidence that phosphorus and thermal environments are key factors to

  19. Estimation of heat and freshwater transports in the North Pacific using high-resolution expendable bathythermograph data

    NASA Astrophysics Data System (ADS)

    Uehara, Hiroki; Kizu, Shoichi; Hanawa, Kimio; Yoshikawa, Yasushi; Roemmich, Dean

    2008-02-01

    The mean heat and freshwater transports in the North Pacific subtropical gyre during 1998-2002 are estimated. High-resolution expendable bathythermograph/expendable conductivity-temperature-depth (XBT/XCTD) transects (PX-40, Honolulu to Japan; PX-37, San Francisco to Honolulu; PX-10, Honolulu to Guam; PX-44, Guam to Taiwan/Hong Kong) are used to calculate geostrophic transport across each of the ship tracks. Ekman transport is estimated from satellite-scatterometer wind stress. The mean heat and freshwater transport convergences into the northern box bounded by the PX-40/37 transects and the Tsushima and Bering Straits are 0.26 ± 0.16 pW (pW = 1015 W) and -0.26 ± 0.11 Sv (Sv = 106 m3/s), respectively. Heat and freshwater transport convergences into the western box bounded by the PX-40/10/44 transects and the Tsushima Strait are estimated to be 0.32 ± 0.17 pW and 0.08 ± 0.07 Sv, respectively. In both boxes, warmer waters transported inward by the Ekman flow and by the Kuroshio are compensated by the export of waters at cooler temperatures, whose peaks are found in the temperatures of the mode waters formed in the North Pacific. The salt budget is also described to consider the mechanisms of freshwater transport. Since the western box includes the region with the strongest heat loss to the atmosphere and is possibly a key region for climatic decadal variation, it is necessary to continue the high-resolution XBT/XCTD measurement and to make an effort at improving the estimation of heat and freshwater transports in order to contribute to advancing climate studies.

  20. A Mechanism for a Tropical Cloud Thermostat in response to Ocean Heat Transport Changes

    NASA Astrophysics Data System (ADS)

    Koll, D.; Pierrehumbert, R.; Abbot, D. S.

    2011-12-01

    Past studies have proposed that clouds could hold tropical temperatures constant in response to rising CO2 levels and thus act like a tropical thermostat. If such a thermostat exists, it would help explain the low meridional temperature gradients during the Pliocene and Eocene. Subsequent observational and theoretical work, however, has raised questions about the validity of a tropical cloud thermostat in response to changes in CO2 . Independently, recent work has suggested that tropical cyclones could have increased the ocean heat transport (OHT) and lowered temperature gradients in the Pliocene and Eocene. This motivates further theoretical investigation of the influence of OHT on tropical and global mean temperature. We consider this question with a global climate model (CAM4 and CAM5) that is coupled to a slab ocean run in aquaplanet mode with no sea ice. We force the model with an idealized OHT profile and vary the amplitude of the profile. We find that increased OHT raises global mean temperature and decreases the temperature gradient, consistent with previous studies. Unlike other studies, we also find a negative tropical cloud feedback that keeps tropical temperatures nearly constant in response to OHT changes, i.e., a cloud thermostat. The thermostat is linked to the global water feedback and atmospheric circulation. Increasing the OHT causes less evaporation in the tropics and a weaker Hadley circulation, both of which dry the deep tropics. This leads to less reflective clouds in the deep tropics, which causes a warming and counteracts the cooling effects of increased ocean heat export from the tropics. We investigate the thermostat's robustness across a large range of ocean heat transport strengths, including cases in which the ocean reverses its transport. We find that global temperatures and tropical clouds respond approximately linearly and antisymetrically to changes in OHT (see figure). In contrast, increases in CO2 cause a simple warming of both

  1. Influence of Aerosol Heating on the Stratospheric Transport of the Mt. Pinatubo Eruption

    NASA Technical Reports Server (NTRS)

    Aquila, Valentina; Oman, Luke D.; Stolarski, Richard S.

    2011-01-01

    On June 15th, 1991 the eruption of Mt. Pinatubo (15.1 deg. N, 120.3 Deg. E) in the Philippines injected about 20 Tg of sulfur dioxide in the stratosphere, which was transformed into sulfuric acid aerosol. The large perturbation of the background aerosol caused an increase in temperature in the lower stratosphere of 2-3 K. Even though stratospheric winds climatological]y tend to hinder the air mixing between the two hemispheres, observations have shown that a large part of the SO2 emitted by Mt. Pinatubo have been transported from the Northern to the Southern Hemisphere. We simulate the eruption of Mt. Pinatubo with the Goddard Earth Observing System (GEOS) version 5 global climate model, coupled to the aerosol module GOCART and the stratospheric chemistry module StratChem, to investigate the influence of the eruption of Mt. Pinatubo on the stratospheric transport pattern. We perform two ensembles of simulations: the first ensemble consists of runs without coupling between aerosol and radiation. In these simulations the plume of aerosols is treated as a passive tracer and the atmosphere is unperturbed. In the second ensemble of simulations aerosols and radiation are coupled. We show that the set of runs with interactive aerosol produces a larger cross-equatorial transport of the Pinatubo cloud. In our simulations the local heating perturbation caused by the sudden injection of volcanic aerosol changes the pattern of the stratospheric winds causing more intrusion of air from the Northern into the Southern Hemisphere. Furthermore, we perform simulations changing the injection height of the cloud, and study the transport of the plume resulting from the different scenarios. Comparisons of model results with SAGE II and AVHRR satellite observations will be shown.

  2. Asynchronous broadcast for ordered delivery between compute nodes in a parallel computing system where packet header space is limited

    DOEpatents

    Kumar, Sameer

    2010-06-15

    Disclosed is a mechanism on receiving processors in a parallel computing system for providing order to data packets received from a broadcast call and to distinguish data packets received at nodes from several incoming asynchronous broadcast messages where header space is limited. In the present invention, processors at lower leafs of a tree do not need to obtain a broadcast message by directly accessing the data in a root processor's buffer. Instead, each subsequent intermediate node's rank id information is squeezed into the software header of packet headers. In turn, the entire broadcast message is not transferred from the root processor to each processor in a communicator but instead is replicated on several intermediate nodes which then replicated the message to nodes in lower leafs. Hence, the intermediate compute nodes become "virtual root compute nodes" for the purpose of replicating the broadcast message to lower levels of a tree.

  3. Molecular dynamics simulation of heat transport across silicon-carbon nanotubes interface

    NASA Astrophysics Data System (ADS)

    Kim, Taejin

    Thermal interfacial resistance across single wall nanotube (SWNT) and silicon interface is investigated by molecular dynamics (MD) simulation. The effect of the interaction on thermal interfacial resistance is studied by applying bonded interaction as sum of bonded and non-bonded van der Waals interactions, and only non-bonded van der Waals interaction on the interface. For both cases, different temperature discontinuities (drops) at the interface are obtained. It is found that the thermal interfacial resistance of non-bonded interaction at the 3A separation is 20 times greater than that of the bonded interaction. At 300K, the thermal interfacial resistance of the bonded interaction is 2.85x10-9m2K/W and that of non-bonded interaction is 5.65x10-8m2K/W. It is also found that the thermal interface resistance decreases as temperature increases up to room temperature. The low frequency radial phonon modes in CNT are excited due to the coupling with silicon phonon modes and contribute the heat transport across interface under the bonded interaction. In contrast, no change of radial phonon mode in non-bonded interaction is found. The excitation of the radial breath mode (RBM) and low frequency radial phonon modes increase with temperature and transport more heat energy across interface and results in lowering the thermal interfacial resistance at high temperature. The propagation of heat pulses in zigzag and armchair double wall nanotubes (DWNTs) are also investigated using molecular dynamics simulations. It is found that the leading heat wave packets in zigzag (9,0)/(18,0) and armchair (5,5)/(10,10) DWNT move with the speed of longitudinal acoustic (LA) phonon modes. The intensities of the leading heat wave packets in outer and inner shells in DWNTs were found to be five to seven times larger than that of the corresponding single wall nanotubes (SWNT). The heat energy carried by the leading heat wave packets in zigzag DWNT was about four and five times more than those

  4. Heat transport in the high-pressure ice mantle of large icy moons

    NASA Astrophysics Data System (ADS)

    Choblet, G.; Tobie, G.; Sotin, C.; Kalousová, K.; Grasset, O.

    2017-03-01

    While the existence of a buried ocean sandwiched between surface ice and high-pressure (HP) polymorphs of ice emerges as the most plausible structure for the hundreds-of-kilometers thick hydrospheres within large icy moons of the Solar System (Ganymede, Callisto, Titan), little is known about the thermal structure of the deep HP ice mantle and its dynamics, possibly involving melt production and extraction. This has major implications for the thermal history of these objects as well as on the habitability of their ocean as the HP ice mantle is presumed to limit chemical transport from the rock component to the ocean. Here, we describe 3D spherical simulations of subsolidus thermal convection tailored to the specific structure of the HP ice mantle of large icy moons. Melt production is monitored and melt transport is simplified by assuming instantaneous extraction to the ocean above. The two controlling parameters for these models are the rheology of ice VI and the heat flux from the rock core. Reasonable end-members are considered for both parameters as disagreement remains on the former (especially the pressure effect on viscosity) and as the latter is expected to vary significantly during the moon's history. We show that the heat power produced by radioactive decay within the rock core is mainly transported through the HP ice mantle by melt extraction to the ocean, with most of the melt produced directly above the rock/water interface. While the average temperature in the bulk of the HP ice mantle is always relatively cool when compared to the value at the interface with the rock core (∼ 5 K above the value at the surface of the HP ice mantle), maximum temperatures at all depths are close to the melting point, often leading to the interconnection of a melt path via hot convective plume conduits throughout the HP ice mantle. Overall, we predict long periods of time during these moons' history where water generated in contact with the rock core is transported to

  5. On the calculation of turbulent heat transport downstream from an abrupt pipe expansion

    NASA Technical Reports Server (NTRS)

    Chieng, C. C.; Launder, B. E.

    1980-01-01

    A numerical study of flow and heat transfer in the separated flow region produced by an abrupt pipe explosion is reported, with emphasis on the region in the immediate vicinity of the wall where turbulent transport gives way to molecular conduction and diffusion. The analysis is based on a modified TEACH-2E program with the standard k-epsilon model of turbulence. Predictions of the experimental data of Zemanick and Dougall (1970) for a diameter ratio of 0.54 show generally encouraging agreement with experiment. At a diameter ratio of 0.43 different trends are discernable between measurement and calculation, though this appears to be due to effects unconnected with the wall region studied here.

  6. Two-scale approach for the coupled heat and moisture transport

    NASA Astrophysics Data System (ADS)

    Kruis, Jaroslav; Krejčí, Tomáš

    2016-06-01

    This paper describes two-level approach for coupled heat and moisture transport in masonry structures. Motivation for two-level description comes from two major difficulties connected with masonry. First, the size of stone blocks is much larger than the size of mortar layers and very fine mesh has to be used. Second, the masonry composition is always random and therefore the concept of representative volume is reasonable. In two-level approach, the macro-scale level deals with a structure while the meso-scale level is concentrated on detailed composition of the masonry. Connection between the macro and meso level will be described. This two-level approach is suitable for parallel computers.

  7. Plasma networking in magnetically confined plasmas and diagnostics of nonlocal heat transport in tokamak filamentary plasmas

    NASA Astrophysics Data System (ADS)

    Kukushkin, A. B.; Rantsev-Kartinov, V. A.

    1999-02-01

    The method of multilevel dynamical contrasting is applied to analyzing available data from tokamak plasmas. The results illustrate a possibility of extending the concept of the plasma percolating networks in dense Z pinches (and other inertially confined plasmas) to the case of magnetically confined plasmas. This extension suggests a necessity to append the conventional picture of the nonfilamentary plasma (which is nearly a fluid described by conventional magnetohydrodynamics) with a "network" component which is formed by the strongest long-living filaments of electric current and penetrate the "fluid" component. Signs of networking are found in visible light and soft x-ray images, and magnetic probing data. A diagnostic algorithm is formulated for identifying the role of plasma networking in observed phenomena of nonlocal (non-diffusive) heat transport in a tokamak.

  8. Lattice Boltzmann technique for heat transport phenomena coupled with melting process

    NASA Astrophysics Data System (ADS)

    Ibrahem, A. M.; El-Amin, M. F.; Mohammadein, A. A.; Gorla, Rama Subba Reddy

    2017-01-01

    In this work, the heat transport phenomena coupled with melting process are studied by using the enthalpy-based lattice Boltzmann method (LBM). The proposed model is a modified version of thermal LB model, where could avoid iteration steps and ensures high accuracy. The Bhatnagar-Gross-Krook (BGK) approximation with a D1Q2 lattice was used to determine the temperature field for one-dimensional melting by conduction and multi-distribution functions (MDF) with D2Q9 lattice was used to determine the density, velocity and temperature fields for two-dimensional melting by natural convection. Different boundary conditions including Dirichlet, adiabatic and bounce-back boundary conditions were used. The influence of increasing Rayleigh number (from 103 to 105) on temperature distribution and melting process is studied. The obtained results show that a good agreement with the analytical solution for melting by conduction case and with the benchmark solution for melting by convection.

  9. Transport of radial heat flux and second sound in fusion plasmas

    SciTech Connect

    Guercan, Oe. D.; Berionni, V.; Hennequin, P.; Morel, P.; Vermare, L.; Diamond, P. H.; Garbet, X.; Dif-Pradalier, G.; Kosuga, Y.

    2013-02-15

    Simple flux-gradient relations that involve time delay and radial coupling are discussed. Such a formulation leads to a rather simple description of avalanches and may explain breaking of gyroBohm transport scaling. The generalization of the flux-gradient relation (i.e., constitutive relation), which involve both time delay and spatial coupling, is derived from drift-kinetic equation, leading to kinetic definitions of constitutive elements such as the flux of radial heat flux. This allows numerical simulations to compute these cubic quantities directly. The formulation introduced here can be viewed as an extension of turbulence spreading to include the effect of spreading of cross-phase as well as turbulence intensity, combined in such a way to give the flux. The link between turbulence spreading and entropy production is highlighted. An extension of this formulation to general quasi-linear theory for the distribution function in the phase space of radial position and parallel velocity is also discussed.

  10. Estimating Ocean Heat Transport Attributable to Tropical Cyclone Activity Using ERA-40 Data

    NASA Astrophysics Data System (ADS)

    Sriver, R. L.; Huber, M.

    2005-12-01

    Ocean mixing is an important physical process because it drives ocean heat transport (OHT) and primary productivity. Tropical cyclones (TCs) have shown to be efficient ocean mixers, the extent of which can be characterized by the cold wakes left behind these storms. Preliminary work proposes that TCs may be responsible for an amount of mixing sufficient, by itself, to account for all modern OHT (Emanuel 2001, 2002, 2003). Here we analyze ECMWF ERA-40 TC-induced sea surface temperature and surface air temperature anomalies during the past 40 years to estimate the TC contribution to mean annual OHT. TC winds from several data sets are also analyzed, and trends in the annually integrated winds and OHT are compared. TC-winds and mixing correlate well, which suggests that future increases in TC strength and frequency may result in increased OHT.

  11. Material transport in laser-heated diamond anvil cell melting experiments

    NASA Technical Reports Server (NTRS)

    Campbell, Andrew J.; Heinz, Dion L.; Davis, Andrew M.

    1992-01-01

    A previously undocumented effect in the laser-heated diamond anvil cell, namely, the transport of molten species through the sample chamber, over distances large compared to the laser beam diameter, is presented. This effect is exploited to determine the melting behavior of high-pressure silicate assemblages of olivine composition. At pressures where beta-spinel is the phase melted, relative strengths of partitioning can be estimated for the incompatible elements studied. Iron was found to partition into the melt from beta-spinel less strongly than calcium, and slightly more strongly than manganese. At higher pressures, where a silicate perovskite/magnesiowuestite assemblage is melted, it is determined that silicate perovskite is the liquidus phase, with iron-rich magnesiowuestite accumulating at the end of the laser-melted stripe.

  12. Numerical investigation of plasma edge transport and limiter heat fluxes in Wendelstein 7-X startup plasmas with EMC3-EIRENE

    NASA Astrophysics Data System (ADS)

    Effenberg, F.; Feng, Y.; Schmitz, O.; Frerichs, H.; Bozhenkov, S. A.; Hölbe, H.; König, R.; Krychowiak, M.; Pedersen, T. Sunn; Reiter, D.; Stephey, L.; W7-X Team

    2017-03-01

    The results of a first systematic assessment of plasma edge transport processes for the limiter startup configuration at Wendelstein 7-X are presented. This includes an investigation of transport from intrinsic and externally injected impurities and their impact on the power balance and limiter heat fluxes. The fully 3D coupled plasma fluid and kinetic neutral transport Monte Carlo code EMC3-EIRENE is used. The analysis of the magnetic topology shows that the poloidally and toroidally localized limiters cause a 3D helical scrape-off layer (SOL) consisting of magnetic flux tubes of three different connection lengths L C. The transport in the helical SOL is governed by L C as topological scale length for the parallel plasma loss channel to the limiters. A clear modulation of the plasma pressure with L C is seen. The helical flux tube topology results in counter streaming sonic plasma flows. The heterogeneous SOL plasma structure yields an uneven limiter heat load distribution with localized peaking. Assuming spatially constant anomalous transport coefficients, increasing plasma density yields a reduction of the maximum peak heat loads from 12 MWm‑2 to 7.5 MWm‑2 and a broadening of the deposited heat fluxes. The impact of impurities on the limiter heat loads is studied by assuming intrinsic carbon impurities eroded from the limiter surfaces with a gross chemical sputtering yield of 2 % . The resulting radiative losses account for less than 10% of the input power in the power balance with marginal impact on the limiter heat loads. It is shown that a significant mitigation of peak heat loads, 40–50%, can be achieved with controlled impurity seeding with nitrogen and neon, which is a method of particular interest for the later island divertor phase.

  13. Characterization of Single Phase and Two Phase Heat and Momentum Transport in a Spiraling Radial Inow Microchannel Heat Sink

    NASA Astrophysics Data System (ADS)

    Ruiz, Maritza

    Thermal management of systems under high heat fluxes on the order of hundreds of W/cm2 is important for the safety, performance and lifetime of devices, with innovative cooling technologies leading to improved performance of electronics or concentrating solar photovoltaics. A novel, spiraling radial inflow microchannel heat sink for high flux cooling applications, using a single phase or vaporizing coolant, has demonstrated enhanced heat transfer capabilities. The design of the heat sink provides an inward swirl flow between parallel, coaxial disks that form a microchannel of 1 cm radius and 300 micron channel height with a single inlet and a single outlet. The channel is heated on one side through a conducting copper surface, and is essentially adiabatic on the opposite side to simulate a heat sink scenario for electronics or concentrated photovoltaics cooling. Experimental results on the heat transfer and pressure drop characteristics in the heat sink, using single phase water as a working fluid, revealed heat transfer enhancements due to flow acceleration and induced secondary flows when compared to unidirectional laminar fully developed flow between parallel plates. Additionally, thermal gradients on the surface are small relative to the bulk fluid temperature gain, a beneficial feature for high heat flux cooling applications. Heat flux levels of 113 W/cm2 at a surface temperature of 77 deg C were reached with a ratio of pumping power to heat rate of 0.03%. Analytical models on single phase flow are used to explore the parametric trends of the flow rate and passage geometry on the streamlines and pressure drop through the device. Flow boiling heat transfer and pressure drop characteristics were obtained for this heat sink using water at near atmospheric pressure as the working fluid for inlet subcooling levels ranging from 20 to 80 deg C and mean mass flux levels ranging from 184-716 kg/m. 2s. Flow enhancements similar to singlephase flow were expected, as well

  14. A Comprehensive Flow, Heat and Mass Transport Uncertainty Quantification in Discrete Fracture Network Systems

    NASA Astrophysics Data System (ADS)

    Ezzedine, S. M.

    2010-12-01

    Fractures and fracture networks are the principle pathways for migration of water, heat and mass in enhanced geothermal systems, oil and gas reservoirs, CO2 leakage from saline aquifers, and radioactive and toxic industrial wastes from underground storage repositories. A major issue to overcome when characterizing a fractured reservoir is that of data limitation due to accessibility and affordability. Moreover, the ability to map discontinuities in the rock with available geological and geophysical tools tends to decrease particularly as the scale of the discontinuity goes down. Geological characterization data include measurements of fracture density, orientation, extent, and aperture, and are based on analysis of outcrops, borehole optical and acoustic televiewer logs, aerial photographs, and core samples among others. All of these measurements are taken at the field scale through a very sparse limited number of deep boreholes. These types of data are often reduced to probability distributions function for predictive modeling and simulation in a stochastic framework such as stochastic discrete fracture network. Stochastic discrete fracture network models enable, through Monte Carlo realizations and simulations, for probabilistic assessment of flow and transport phenomena that are not adequately captured using continuum models. Despite the fundamental uncertainties inherited within the probabilistic reduction of the sparse data collected, very little work has been conducted on quantifying uncertainty on the reduced probabilistic distribution functions. In the current study, using nested Monte Carlo simulations, we present the impact of parameter uncertainties of the distribution functions that characterize discrete fracture networks on the flow, heat and mass transport. Numerical results of first, second and third moments, normalized to a base case scenario, are presented and compared to theoretical results extended from percolation theory.

  15. An Assessment of Transport Property Estimation Methods for Ammonia-Water Mixtures and Their Influence on Heat Exchanger Size

    NASA Astrophysics Data System (ADS)

    Kærn, M. R.; Modi, A.; Jensen, J. K.; Haglind, F.

    2015-07-01

    Transport properties of fluids are indispensable for heat exchanger design. The methods for estimating the transport properties of ammonia-water mixtures are not well established in the literature. The few existent methods are developed from none or limited, sometimes inconsistent experimental datasets, conducted for the liquid phase only. These datasets are usually confined to low concentrations and temperatures, which are much less than those occurring in Kalina cycle boilers. This paper presents a comparison of various methods used to estimate the viscosity and the thermal conductivity of ammonia-water mixtures. Firstly, the different methods are introduced and compared at various temperatures and pressures. Secondly, their individual influence on the required heat exchanger size (surface area) is investigated. For this purpose, two case studies related to the use of the Kalina cycle are considered: a flue-gas-based heat recovery boiler for a combined cycle power plant and a hot-oil-based boiler for a solar thermal power plant. The different transport property methods resulted in larger differences at high pressures and temperatures, and a possible discontinuous first derivative, when using the interpolative methods in contrast to the corresponding state methods. Nevertheless, all possible mixture transport property combinations used herein resulted in a heat exchanger size within 4.3 % difference for the flue-gas heat recovery boiler, and within 12.3 % difference for the oil-based boiler.

  16. The Asian monsoon's role in atmospheric heat transport responses to orbital and millennial-scale climate change

    NASA Astrophysics Data System (ADS)

    McGee, D.; Green, B.; Donohoe, A.; Marshall, J.

    2015-12-01

    Recent studies have provided a framework for understanding the zonal-mean position of the tropical rain belt by documenting relationships between rain belt latitude and atmospheric heat transport across the equator (Donohoe et al., 2013). Modern seasonal and interannual variability in globally-averaged rain belt position (often referred to as 'ITCZ position') reflects the interhemispheric heat balance, with the rain belt's displacement toward the warmer hemisphere directly proportional to atmospheric heat transport into the cooler hemisphere. Model simulations suggest that rain belt shifts are likely to have obeyed the same relationship with interhemispheric heat transport in response to past changes in orbital parameters, ice sheets, and ocean circulation. This relationship implies that even small (±1 degree) shifts in the mean rain belt require large changes in hemispheric heat budgets, placing tight bounds on mean rain belt shifts in past climates. This work has primarily viewed tropical circulation in two dimensions, as a pair of zonal-mean Hadley cells on either side of the rain belt that are displaced north and south by perturbations in hemispheric energy budgets, causing the atmosphere to transport heat into the cooler hemisphere. Here we attempt to move beyond this zonal-mean perspective, motivated by arguments that the Asian monsoon system, rather than the zonal-mean circulation, plays the dominant role in annual-mean heat transport into the southern hemisphere in the modern climate (Heaviside and Czaja, 2012; Marshall et al., 2014). We explore a range of climate change experiments, including simulations of North Atlantic cooling and mid-Holocene climate, to test whether changes in interhemispheric atmospheric heat transport are primarily driven by the mean Hadley circulation, the Asian monsoon system, or other regional-scale atmospheric circulation changes. The scalings that this work identifies between Asian monsoon changes and atmospheric heat

  17. Heat and particle transport in a one-dimensional hard-point gas model with on-site potential

    SciTech Connect

    Wang, Lei

    2015-05-15

    Heat and particle transport in a one-dimensional hard-point gas of elastically colliding particles are studied. In the nonequal mass case, due to the presence of on-site potential, the heat conduction of the model obeys the Fourier law and all the transport coefficients asymptotically approach constants in the thermodynamic limit. The thermoelectric figure of merit ZT increases slowly with the system length L and is proportional to the height of the potential barriers H in high H regime. These findings may serve as a guide for future theoretical and experimental studies.

  18. Water, solute and heat transport in the soil: the Australian connection

    NASA Astrophysics Data System (ADS)

    Knight, John

    2016-04-01

    The interest of Peter Raats in water, solute and heat transport in the soil has led to scientific and/or personal interactions with several Australian scientists such as John Philip, David Smiles, Greg Davis and John Knight. Along with John Philip and Robin Wooding, Peter was an early user of the Gardner (1958) linearised model of soil water flow, which brought him into competition with John Philip. I will discuss some of Peter's solutions relevant to infiltration from line and point sources, cavities and basins. A visit to Canberra, Australia in the early 1980s led to joint work on soil water flow, and on combined water and solute movement with David Smiles and others. In 1983 Peter was on the PhD committee for Greg Davis at the University of Wollongong, and some of the methods in his thesis 'Mathematical modelling of rate-limiting mechanisms of pyritic oxidation in overburden dumps' were later used by Peter's student Sjoerd van der Zee. David Smiles and Peter wrote a survey article 'Hydrology of swelling clay soils' in 2005. In the last decade Peter has been investigating the history of groundwater and vadose zone hydrology, and recently he and I have been bringing to light the largely forgotten work of Lewis Fry Richardson on finite difference solution of the heat equation, drainage theory, soil physics, and the soil-plant-atmosphere continuum.

  19. Non-local Lateral electron heat transport from one or more hot spots.

    NASA Astrophysics Data System (ADS)

    Matte, Jean-Pierre; Alouani-Bibi, Fathallah

    2000-10-01

    Fokker-Planck simulations of collisional absorption and transport in long scale length, preformed, underdense plasmas heated by intense and narrow laser hot spots, as in certain recent LANL experiments [1], are presented. The temperature profiles compared with those obtained from flux limited or delocalized heat flow models. For the former, the temperature peaks can be matched only if a very low flux limiter is used, and even then, the scale length of the temperature profile is always overestimated. The electron distribution function will be characterized, and compared to the "DLM" shape, exp(-(v/u)^m), [2] and the best fit for m will be compared to older formulas for uniform plasmas [2]. Hydrodynamic effects are also addressed with simulations which include ion motion; both with and without the ponderomotive force. The enhancement of sound velocity due to the "DLM" shape [3] inside the hot spot will be quantified. [1] J.A. Cobble et al., Phys. Plasmas, 7, 323 (2000) [2] J.P. Matte et al., Plasma Phys. and Contr. Fusion, 30, 1665, (1988) [3] B. B. Afeyan et al., PRL 81, 2322 (1998).

  20. Off-axis electron cyclotron heating and the sandpile paradigm for transport in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    March, T. K.; Chapman, S. C.; Dendy, R. O.; Merrifield, J. A.

    2004-02-01

    Previous observations that suggest a substantial role for nondiffusive energy transport in tokamaks subjected to off-axis electron cyclotron heating (ECH) are compared to the output from a sandpile model. The observations considered include local and global aspects of temperature profile evolution in the DIII-D [for example, C. C. Petty and T. C. Luce, Nucl. Fusion 34, 121 (1994)] and RTP (Rijnhuizen Tokamak Project) [for example, M. R. de Baar, M. N. A. Beurskens, G. M. D. Hogeweij, and N. J. Lopes Cardozo, Phys. Plasmas 6, 4645 (1999)] tokamaks. The sandpile model employed is an extension, to incorporate noncentral fueling, of one used previously to address tokamak physics issues [S. C. Chapman, R. O. Dendy, and B. Hnat, Phys. Rev. Lett. 86, 2814 (2001)]. It is found that there are significant points of resemblance between the phenomenology of the noncentrally fueled sandpile and of the tokamaks with off-axis ECH. This suggests that the essential ingredient of the sandpile model, namely avalanching conditioned by a local critical gradient, may be one of the key transport effects generated by the tokamak plasma physics.

  1. Predicting the fidelity of JPEG2000 compressed CT images using DICOM header information

    SciTech Connect

    Kim, Kil Joong; Kim, Bohyoung; Lee, Hyunna; Choi, Hosik; Jeon, Jong-June; Ahn, Jeong-Hwan; Lee, Kyoung Ho

    2011-12-15

    Purpose: To propose multiple logistic regression (MLR) and artificial neural network (ANN) models constructed using digital imaging and communications in medicine (DICOM) header information in predicting the fidelity of Joint Photographic Experts Group (JPEG) 2000 compressed abdomen computed tomography (CT) images. Methods: Our institutional review board approved this study and waived informed patient consent. Using a JPEG2000 algorithm, 360 abdomen CT images were compressed reversibly (n = 48, as negative control) or irreversibly (n = 312) to one of different compression ratios (CRs) ranging from 4:1 to 10:1. Five radiologists independently determined whether the original and compressed images were distinguishable or indistinguishable. The 312 irreversibly compressed images were divided randomly into training (n = 156) and testing (n = 156) sets. The MLR and ANN models were constructed regarding the DICOM header information as independent variables and the pooled radiologists' responses as dependent variable. As independent variables, we selected the CR (DICOM tag number: 0028, 2112), effective tube current-time product (0018, 9332), section thickness (0018, 0050), and field of view (0018, 0090) among the DICOM tags. Using the training set, an optimal subset of independent variables was determined by backward stepwise selection in a four-fold cross-validation scheme. The MLR and ANN models were constructed with the determined independent variables using the training set. The models were then evaluated on the testing set by using receiver-operating-characteristic (ROC) analysis regarding the radiologists' pooled responses as the reference standard and by measuring Spearman rank correlation between the model prediction and the number of radiologists who rated the two images as distinguishable. Results: The CR and section thickness were determined as the optimal independent variables. The areas under the ROC curve for the MLR and ANN predictions were 0.91 (95% CI; 0

  2. A non-equilibrium model for soil heating and moisture transport during extreme surface heating: the soil (heat-moisture-vapor) HMV-Model Version 1

    NASA Astrophysics Data System (ADS)

    Massman, W. J.

    2015-11-01

    Increased use of prescribed fire by land managers and the increasing likelihood of wildfires due to climate change require an improved modeling capability of extreme heating of soils during fires. This issue is addressed here by developing and testing the soil (heat-moisture-vapor) HMV-model, a 1-D (one-dimensional) non-equilibrium (liquid-vapor phase change) model of soil evaporation that simulates the coupled simultaneous transport of heat, soil moisture, and water vapor. This model is intended for use with surface forcing ranging from daily solar cycles to extreme conditions encountered during fires. It employs a linearized Crank-Nicolson scheme for the conservation equations of energy and mass and its performance is evaluated against dynamic soil temperature and moisture observations, which were obtained during laboratory experiments on soil samples exposed to surface heat fluxes ranging between 10 000 and 50 000 W m-2. The Hertz-Knudsen equation is the basis for constructing the model's non-equilibrium evaporative source term. Some unusual aspects of the model that were found to be extremely important to the model's performance include (1) a dynamic (temperature and moisture potential dependent) condensation coefficient associated with the evaporative source term, (2) an infrared radiation component to the soil's thermal conductivity, and (3) a dynamic residual soil moisture. This last term, which is parameterized as a function of temperature and soil water potential, is incorporated into the water retention curve and hydraulic conductivity functions in order to improve the model's ability to capture the evaporative dynamics of the strongly bound soil moisture, which requires temperatures well beyond 150 °C to fully evaporate. The model also includes film flow, although this phenomenon did not contribute much to the model's overall performance. In general, the model simulates the laboratory-observed temperature dynamics quite well, but is less precise (but

  3. Quantitative estimates of past changes in ITCZ position and cross-equatorial atmospheric heat transport

    NASA Astrophysics Data System (ADS)

    McGee, D.; Donohoe, A.; Marshall, J.; Ferreira, D.

    2012-12-01

    The mean position and seasonal migration of the Intertropical Convergence Zone (ITCZ) govern the intensity, spatial distribution and seasonality of precipitation throughout the tropics as well as the magnitude and direction of interhemispheric atmospheric heat transport (AHT). As a result of these links to global tropical precipitation and hemispheric heat budgets, paleoclimate studies have commonly sought to use reconstructions of local precipitation and surface winds to identify past shifts in the ITCZ's mean position or seasonal extent. Records indicate close ties between ITCZ position and interhemispheric surface temperature gradients in past climates, with the ITCZ shifting toward the warmer hemisphere. This shift would increase AHT into the cooler hemisphere to at least partially compensate for cooling there. Despite widespread qualitative evidence consistent with ITCZ shifts, few proxy records offer quantitative estimates of the distance of these shifts or of the associated changes in AHT. Here we present a strategy for placing quantitative limits on past changes in mean annual ITCZ position and interhemispheric AHT based on explorations of the modern seasonal cycle and models of present and past climates. We use reconstructions of tropical sea surface temperature gradients to place bounds on globally averaged ITCZ position and interhemispheric AHT during the Last Glacial Maximum, Heinrich Stadial 1, and the Mid-Holocene (6 ka). Though limited by the small number of SST records available, our results suggest that past shifts in the global mean ITCZ were small, typically less than 1 degree of latitude. Past changes in interhemispheric AHT may have been substantial, with anomalies approximately equal to the magnitude of modern interhemispheric AHT. Using constraints on the invariance of the total (ocean+atmosphere) heat transport we suggest possible bounds on fluctuations of the OHT and AMOC during Heinrich Stadial 1. We also explore ITCZ shifts in models and

  4. Thermal conductivity and specific heat of the spin-ice compound Dy2Ti2O7: Experimental evidence for monopole heat transport

    NASA Astrophysics Data System (ADS)

    Kolland, G.; Breunig, O.; Valldor, M.; Hiertz, M.; Frielingsdorf, J.; Lorenz, T.

    2012-08-01

    Elementary excitations in the spin-ice compound Dy2Ti2O7 can be described as magnetic monopoles propagating independently within the pyrochlore lattice formed by magnetic Dy ions. We studied the magnetic-field dependence of the thermal conductivity κ(B) for B||[001] and observe clear evidence for magnetic heat transport originating from the monopole excitations. The magnetic contribution κmag is strongly field dependent and correlates with the magnetization M(B). The diffusion coefficient obtained from the ratio of κmag and the magnetic specific heat is strongly enhanced below 1 K, indicating a high mobility of the monopole excitations in the spin-ice state.

  5. Required conditions for and coincident 1/1-mode activity associated with the nonlocal electron heat transport effect on TFTR

    SciTech Connect

    Kissick, M.W.; Callen, J.D.; Fredrickson, E.D.

    1997-08-01

    A database of 71 distinct and randomly collected cold pulse cases from TFTR is analyzed. Observations show a striking parameter regime cutoff for the presence of nonlocal transient transport and coincident MHD (1/1-mode) activity as well as for changes in the radial speed of the nonlocal transport effect and changes in the sawtooth period. A nontrivial link is demonstrated between electron heat transport and MHD properties through observation of a common cutoff in the parameter n{sub e}(0)/T{sub e}(0){sup 1/2} and a common threshold in injection size for radial speed and sawtooth period changes. Auxiliary heating (via energetic neutral beams) destroys whatever process is responsible for the nonlocal transport effect, unless the discharge contains significant amounts of injected tritium. These observations are preliminary, but they represent important circumstantial evidence for mysterious propagation of changes in some MHD-related phenomenon as being responsible for a large fraction of electron heat transport. This propagation is then probably a function of n{sub e}(0)/T{sub e}(0){sup 1/2}, ion mass, and possibly beam power. An analysis of Ohmic cases shows that the cutoff in n{sub e}(0)/T{sub e}{sup 1/2} indicates the nonlocal transport effects may occur when the electrons are collisionally thermally decoupled from the ions.

  6. Climate of Earth-Like Planets With and Without Ocean Heat Transport Orbiting a Range of M and K Stars

    NASA Technical Reports Server (NTRS)

    Kiang, N. Y.; Jablonski, Emma R.; Way, Michael J.; Del Genio, Anthony; Roberge, Aki

    2015-01-01

    The mean surface temperature of a planet is now acknowledged as insufficient to surmise its full potential habitability. Advancing our understanding requires exploration with 3D general circulation models (GCMs), which can take into account how gradients and fluxes across a planet's surface influence the distribution of heat, clouds, and the potential for heterogeneous distribution of liquid water. Here we present 3D GCM simulations of the effects of alternative stellar spectra, instellation, model resolution, and ocean heat transport, on the simulated distribution of heat and moisture of an Earth-like planet (ELP).

  7. Ion heat flux and energy transport near the magnetotail neutral sheet

    NASA Astrophysics Data System (ADS)

    Kaufmann, Richard L.; Paterson, William R.

    2008-05-01

    Ten-year averages of energy transport rates near the neutral sheet showed that the enthalpy flux density or thermal energy term QT = (5/2)PV was the largest, where P is the isotropic pressure and V is the bulk flow velocity. The ion heat flux, qi, was the next largest term. Sorting data using a magnetic flux transport parameter showed that qi could become dominant during periods of slow flow. Both qi and the ion bulk velocity Vi were duskward on the dusk side of the neutral sheet. This relationship is characteristic of cross-tail drift and a heat flux that can be attributed to the energy dependent gradient and curvature drifts. The qi and Vi vectors often pointed in different directions on the dawn side. The x component of qi on the dawn side pointed tailward, suggesting entry through the magnetopause of a suprathermal ion component. On the dusk side the qix plots that were sorted using a magnetic flux transport parameter showed evidence of plasma sheet reconnection. The long-term averaged x component of QT pointed earthward almost everywhere in the neutral sheet, and was attributed to periods of very fast plasma flow. The cross-tail component of QT was separated into two contributions. One part of QTy involved a common drift away from midnight during both earthward and tailward fast flows. This feature suggests that thermal energy and plasma flow from the outer plasma sheet toward the neutral sheet near midnight, and then toward the flanks. The other part of QTy involved a differential duskward drift during fast earthward flows and a dawnward drift during fast tailward flows. The incremental E fields that would produce such convection point tailward during the fastest earthward flows and earthward during the fastest tailward flows. The dependencies of Vi, qi and QT on the interplanetary magnetic field (IMF) clock angle also were studied. Both Vi and QT were reduced when the IMF was northward and the neutral sheet plasma became cold and dense. However, no

  8. Increasing transports of volume, heat, and salt towards the Arctic in the Faroe Current 1993-2013

    NASA Astrophysics Data System (ADS)

    Hansen, B.; Larsen, K. M. H.; Hátún, H.; Kristiansen, R.; Mortensen, E.; Østerhus, S.

    2015-06-01

    The flow of warm and saline water from the Atlantic Ocean, across the Greenland-Scotland Ridge, into the Nordic Seas - the Atlantic inflow - is split into three separate branches. The most intensive of these branches is the inflow between Iceland and the Faroe Islands (Faroes), which is focused into the Faroe Current, north of the Faroes. The Atlantic inflow is an integral part of the North Atlantic thermohaline circulation (THC), which is projected to weaken during the 21 century and might conceivably reduce the oceanic heat and salt transports towards the Arctic. Since the mid-1990s, hydrographic properties and current velocities of the Faroe Current have been monitored along a section extending north from the Faroe shelf. From these in situ observations, time series of volume, heat, and salt transport have previously been reported, but the high variability of the transport series has made it difficult to identify trends. Here, we present results from a new analysis of the Faroe Current where the in situ observations have been combined with satellite altimetry. For the period 1993 to 2013, we find the average volume transport of Atlantic water in the Faroe Current to be 3.8 ± 0.5 Sv (1 Sv =106 m3 s-1) with a heat transport relative to 0 °C of 124 ± 15 TW (1 TW =1012 W). Consistent with other results for the Northeast Atlantic component of the THC, we find no indication of weakening. The transports of the Faroe Current, on the contrary, increased. The overall trend over the two decades of observation was 9 ± 8% for volume transport and 18 ± 9% for heat transport (95% confidence intervals). During the same period, the salt transport relative to the salinity of the deep Faroe Bank Channel overflow (34.93) more than doubled, potentially strengthening the feedback on thermohaline intensity. The increased heat and salt transports are partly caused by the increased volume transport and partly by increased temperatures and salinities of the Atlantic inflow

  9. Heat-transport enhancement in rotating turbulent Rayleigh-Bénard convection.

    PubMed

    Weiss, Stephan; Wei, Ping; Ahlers, Guenter

    2016-04-01

    We present new Nusselt-number (Nu) measurements for slowly rotating turbulent thermal convection in cylindrical samples with aspect ratio Γ=1.00 and provide a comprehensive correlation of all available data for that Γ. In the experiment compressed gasses (nitrogen and sulfur hexafluride) as well as the fluorocarbon C_{6}F_{14} (3M Fluorinert FC72) and isopropanol were used as the convecting fluids. The data span the Prandtl-number (Pr) range 0.74heat transport Nu_{r}(1/Ro)≡Nu(1/Ro)/Nu(0) as a function of the dimensionless inverse Rossby number 1/Ro at constant Ra is reported. For Pr≈0.74 and the smallest Ra=3.6×10^{8} the maximum enhancement Nu_{r,max}-1 due to rotation is about 0.02. With increasing Ra, Nu_{r,max}-1 decreased further, and for Ra≳2×10^{9} heat-transport enhancement was no longer observed. For larger Pr the dependence of Nu_{r} on 1/Ro is qualitatively similar for all Pr. As noted before, there is a very small increase of Nu_{r} for small 1/Ro, followed by a decrease by a percent or so, before, at a critical value 1/Ro_{c}, a sharp transition to enhancement by Ekman pumping takes place. While the data revealed no dependence of 1/Ro_{c} on Ra, 1/Ro_{c} decreased with increasing Pr. This dependence could be described by a power law with an exponent α≃-0.41. Power-law dependencies on Pr and Ra could be used to describe the slope S_{Ro}^{+}=∂Nu_{r}/∂(1/Ro) just above 1/Ro_{c}. The Pr and Ra exponents were β_{1}=-0.16±0.08 and β_{2}=-0.04±0.06, respectively. Further increase of 1/Ro led to further increase of Nu_{r} until it reached a maximum value Nu_{r,max}. Beyond the maximum, the Taylor-Proudman (TP) effect, which is expected to lead to reduced vertical fluid transport in the bulk region, lowered Nu_{r}. Nu_{r,max} was largest for the largest Pr. For Pr=28.9, for example, we measured an increase of the heat transport by up to 40% (Nu_{r}-1

  10. Heat-transport enhancement in rotating turbulent Rayleigh-Bénard convection

    NASA Astrophysics Data System (ADS)

    Weiss, Stephan; Wei, Ping; Ahlers, Guenter

    2016-04-01

    We present new Nusselt-number (Nu) measurements for slowly rotating turbulent thermal convection in cylindrical samples with aspect ratio Γ =1.00 and provide a comprehensive correlation of all available data for that Γ . In the experiment compressed gasses (nitrogen and sulfur hexafluride) as well as the fluorocarbon C6F14 (3M Fluorinert FC72) and isopropanol were used as the convecting fluids. The data span the Prandtl-number (Pr) range 0.74 heat transport Nur(1 /Ro ) ≡Nu (1 /Ro ) /Nu (0 ) as a function of the dimensionless inverse Rossby number 1 /Ro at constant Ra is reported. For Pr ≈0.74 and the smallest Ra =3.6 ×108 the maximum enhancement Nur ,max-1 due to rotation is about 0.02. With increasing Ra, Nur ,max-1 decreased further, and for Ra ≳2 ×109 heat-transport enhancement was no longer observed. For larger Pr the dependence of Nur on 1/Ro is qualitatively similar for all Pr. As noted before, there is a very small increase of Nur for small 1/Ro, followed by a decrease by a percent or so, before, at a critical value 1 /Roc , a sharp transition to enhancement by Ekman pumping takes place. While the data revealed no dependence of 1 /Roc on Ra, 1 /Roc decreased with increasing Pr. This dependence could be described by a power law with an exponent α ≃-0.41 . Power-law dependencies on Pr and Ra could be used to describe the slope SRo+=∂ Nur/∂ (1 /Ro ) just above 1 /Roc . The Pr and Ra exponents were β1=-0.16 ±0.08 and β2=-0.04 ±0.06 , respectively. Further increase of 1/Ro led to further increase of Nur until it reached a maximum value Nur ,max. Beyond the maximum, the Taylor-Proudman (TP) effect, which is expected to lead to reduced vertical fluid transport in the bulk region, lowered Nur. Nur ,max was largest for the largest Pr. For Pr =28.9 , for example, we measured an increase of the heat transport by up to 40% (Nur-1 =0.40 ) for the smallest Ra =2.2

  11. Heat-Pipe Development for Advanced Energy Transport Concepts Final Report Covering the Period January 1999 through September 2001

    SciTech Connect

    R.S.Reid; J.F.Sena; A.L.Martinez

    2002-10-01

    This report summarizes work in the Heat-pipe Technology Development for the Advanced Energy Transport Concepts program for the period January 1999 through September 2001. A gas-loaded molybdenum-sodium heat pipe was built to demonstrate the active pressure-control principle applied to a refractory metal heat pipe. Other work during the period included the development of processing procedures for and fabrication and testing of three types of sodium heat pipes using Haynes 230, MA 754, and MA 956 wall materials to assess the compatibility of these materials with sodium. Also during this period, tests were executed to measure the response of a sodium heat pipe to the penetration of water.

  12. Neoclassical transport of energetic minority tail ions generated by ion-cyclotron resonance heating in tokamak geometry

    SciTech Connect

    Chang, C.S. . Courant Inst. of Mathematical Sciences); Hammett, G.W.; Goldston, R.J. . Plasma Physics Lab.)

    1990-01-01

    Neoclassical transport of energetic minority tail ions, which are generated by high powered electromagnetic waves of the Ion Cyclotron Range of Frequencies (ICRF) at the fundamental harmonic resonance, is studied analytically in tokamak geometry. The effect of Coulomb collisions on the tail ion transport is investigated in the present work. The total tail ion transport will be the sum of the present collision-driven transport and the wave-driven transport, which is due to the ICRF-wave scattering of the tail particles as reported in the literature. The transport coefficients have been calculated kinetically, and it is found that the large tail ion viscosity, driven by the localized ICRF-heating and Coulomb slowing-down collisions, induces purely convective particle transport of the tail species, while the energy transport is both convective and diffusive. The rate of radial particle transport is shown to be usually small, but the rate of radial energy transport is larger and may not be negligible compared to the Coulomb slowing-down rate. 18 refs., 2 figs.

  13. High-R Walls for New Construction Structural Performance: Integrated Rim Header Testing

    SciTech Connect

    DeRenzis, A.; Kochkin, V.; Wiehagen, J.

    2013-01-01

    Two prominent approaches within the Building America Program to construct higher R-value walls have included use of larger dimension framing and exterior rigid foam insulation. These approaches have been met with some success; however for many production builders, where the cost of changing framing systems is expensive, the changes have been slow to be realized. In addition, recent building code changes have raised some performance issues for exterior sheathing and raised heel trusses, for example, that indicates a need for continued performance testing for wall systems. The testing methods presented in this report evaluate structural rim header designs over openings up to 6 ft wide and applicable to one- and two-story homes.

  14. Writing user selectable data on the extended header of seismic recordings made on the Texas Instruments DFS-V

    USGS Publications Warehouse

    Robinson, W.C.

    1996-01-01

    A circuit has been developed to allow the writing of up to 192 digits of user-selectable data on a portion of tape called extended header, which is always available for use before each DFS-V seismic record is written. Such data could include navigation information, air gun and streamer depth and shot times.

  15. Heat, electricity, or transportation? The optimal use of residual and waste biomass in Europe from an environmental perspective.

    PubMed

    Steubing, Bernhard; Zah, Rainer; Ludwig, Christian

    2012-01-03

    The optimal use of forest energy wood, industrial wood residues, waste wood, agricultural residues, animal manure, biowaste, and sewage sludge in 2010 and 2030 was assessed for Europe. An energy system model was developed comprising 13 principal fossil technologies for the production of heat, electricity, and transport and 173 bioenergy conversion routes. The net environmental benefits of substituting fossil energy with bioenergy were calculated for all approximately 1500 combinations based on life cycle assessment (LCA) results. An optimization model determines the best use of biomass for different environmental indicators within the quantified EU-27 context of biomass availability and fossil energy utilization. Key factors determining the optimal use of biomass are the conversion efficiencies of bioenergy technologies and the kind and quantity of fossil energy technologies that can be substituted. Provided that heat can be used efficiently, optimizations for different environmental indicators almost always indicate that woody biomass is best used for combined heat and power generation, if coal, oil, or fuel oil based technologies can be substituted. The benefits of its conversion to SNG or ethanol are significantly lower. For non-woody biomass electricity generation, transportation, and heating yield almost comparable benefits as long as high conversion efficiencies and optimal substitutions are assured. The shares of fossil heat, electricity, and transportation that could be replaced with bioenergy are also provided.

  16. Observational Constraints on Atmospheric and Oceanic Cross-Equatorial Heat Transports: Revisiting the Precipitation Asymmetry Problem in Climate Models

    NASA Astrophysics Data System (ADS)

    Loeb, N. G.; Wang, H.; Cheng, A.; Kato, S.; Fasullo, J.; Xu, K. M.; Allan, R. P.

    2015-12-01

    Recent studies have shown strong linkages between hemispheric asymmetries in atmospheric and oceanic energy budgets, tropical precipitation and the mean position of the Intertropical Convergence Zone (ITCZ). The energetics framework has been used to explain why the mean position of the ITCZ is in the Northern Hemisphere and to study large-scale circulation and precipitation responses to changes in the hemispheric distribution of heating. Here, we expand upon these earlier studies by also considering estimates of hemispheric asymmetry in surface and atmospheric radiation budget derived from satellite observations, which enables a decomposition of cross-equatorial heat transport in terms of radiative and non-radiative (i.e., combined latent and sensible heat) components. Satellite observations of top-of-atmosphere (TOA) and surface radiation budget from the Clouds and the Earth's Radiation Budget (CERES) are combined with mass corrected vertically integrated atmospheric energy divergence from reanalysis to infer the regional distribution of the TOA, atmospheric and surface energy budget terms over the globe. Observed radiative and combined sensible and latent heat contributions to atmospheric and oceanic cross-equatorial heat transports are compared with simulations from 30 models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Results show that most CMIP5 models that overestimate tropical precipitation in the SH have too much net downward surface radiation and combined latent and sensible heat flux in the SH relative to the NH. In addition, many of the models also underestimate atmospheric radiative cooling in the SH compared to the NH. Consequently, the models have excessive heating of the SH atmosphere and anomalous SH to NH cross-equatorial heat transport. The anomalous northward heat transport occurs via the upper branch of the northern Hadley Cell, while anomalous NH to SH moisture transport occurs in the lower branch of the northern

  17. Heat transport variation due to change of North Pacific subtropical gyre interior flow during 1993-2012

    NASA Astrophysics Data System (ADS)

    Nagano, Akira; Kizu, Shoichi; Hanawa, Kimio; Roemmich, Dean

    2016-12-01

    Applying segment-wise altimetry-based gravest empirical mode method to expendable bathythermograph temperature, Argo salinity, and altimetric sea surface height data in March, June, and November from San Francisco to near Japan (30∘ N, 145∘ E) via Honolulu, we estimated the component of the heat transport variation caused by change in the southward interior geostrophic flow of the North Pacific subtropical gyre in the top 700 m layer during 1993-2012. The volume transport-weighted temperature ( T I) is strongly dependent on the season. The anomaly of T I from the mean seasonal variation, whose standard deviation is 0.14∘C, was revealed to be caused mainly by change in the volume transport in a potential density layer of 25.0-25.5 σ 𝜃 . The anomaly of T I was observed to vary on a decadal or shorter, i.e., quasi-decadal (QD), timescale. The QD-scale variation of T I had peaks in 1998 and 2007, equivalent to the reduction in the net heat transport by 6 and 10 TW, respectively, approximately 1 year before those of sea surface temperature (SST) in the warm pool region, east of the Philippines. This suggests that variation in T I affects the warm pool SST through modification of the heat balance owing to the entrainment of southward transported water into the mixed layer.

  18. Assessment of Joule heating and its effects on electroosmotic flow and electrophoretic transport of solutes in microfluidic channels.

    PubMed

    Tang, Gongyue; Yan, Deguang; Yang, Chun; Gong, Haiqing; Chai, John Chee; Lam, Yee Cheong

    2006-02-01

    Joule heating is inevitable when an electric field is applied across a conducting medium. It would impose limitations on the performance of electrokinetic microfluidic devices. This article presents a 3-D mathematical model for Joule heating and its effects on the EOF and electrophoretic transport of solutes in microfluidic channels. The governing equations were numerically solved using the finite-volume method. Experiments were carried out to investigate the Joule heating associated phenomena and to verify the numerical models. A rhodamine B-based thermometry technique was employed to measure the solution temperature distributions in microfluidic channels. The microparticle image velocimetry technique was used to measure the velocity profiles of EOF under the influence of Joule heating. The numerical solutions were compared with experimental results, and reasonable agreement was found. It is found that with the presence of Joule heating, the EOF velocity deviates from its normal "plug-like" profile. The numerical simulations show that Joule heating not only accelerates the sample transport but also distorts the shape of the sample band.

  19. Salt tectonics and shallow subseafloor fluid convection: models of coupled fluid-heat-salt transport

    USGS Publications Warehouse

    Wilson, A.; Ruppel, C.

    2007-01-01

    Thermohaline convection associated with salt domes has the potential to drive significant fluid flow and mass and heat transport in continental margins, but previous studies of fluid flow associated with salt structures have focused on continental settings or deep flow systems of importance to petroleum exploration. Motivated by recent geophysical and geochemical observations that suggest a convective pattern to near-seafloor pore fluid flow in the northern Gulf of Mexico (GoMex), we devise numerical models that fully couple thermal and chemical processes to quantify the effects of salt geometry and seafloor relief on fluid flow beneath the seafloor. Steady-state models that ignore halite dissolution demonstrate that seafloor relief plays an important role in the evolution of shallow geothermal convection cells and that salt at depth can contribute a thermal component to this convection. The inclusion of faults causes significant, but highly localized, increases in flow rates at seafloor discharge zones. Transient models that include halite dissolution show the evolution of flow during brine formation from early salt-driven convection to later geothermal convection, characteristics of which are controlled by the interplay of seafloor relief and salt geometry. Predicted flow rates are on the order of a few millimeters per year or less for homogeneous sediments with a permeability of 10−15 m2, comparable to compaction-driven flow rates. Sediment permeabilities likely fall below 10−15 m2 at depth in the GoMex basin, but such thermohaline convection can drive pervasive mass transport across the seafloor, affecting sediment diagenesis in shallow sediments. In more permeable settings, such flow could affect methane hydrate stability, seafloor chemosynthetic communities, and the longevity of fluid seeps.

  20. Impact of electro-magnetic stabilization, small- scale turbulence and multi-scale interactions on heat transport in JET

    NASA Astrophysics Data System (ADS)

    Mantica, Paola

    2016-10-01

    Heat transport experiments in JET, based on ICRH heat flux scans and temperature modulation, have confirmed the importance of two transport mechanisms that are often neglected in modeling experimental results, but are crucial to reach agreement between theory and experiment and may be significant in ITER. The first mechanism is the stabilizing effect of the total pressure gradient (including fast ions) on ITG driven ion heat transport. Such stabilization is found in non-linear gyro-kinetic electro-magnetic simulations using GENE and GYRO, and is the explanation for the observed loss of ion stiffness in the core of high NBI-power JET plasmas. The effect was recently observed also in JET plasmas with dominant ICRH heating and small rotation, due to ICRH fast ions, which is promising for ITER. Such mechanism dominates over ExB flow shear in the core and needs to be included in quasi-linear models to increase their ability to capture the relevant physics. The second mechanism is the capability of small- scale ETG instabilities to carry a significant fraction of electron heat. A decrease in Te peaking is observed when decreasing Zeff Te/Ti, which cannot be ascribed to TEMs but is in line with ETGs. Non-linear GENE single-scale simulations of ETGs and ITG/TEMs show that the ITG/TEM electron heat flux is not enough to match experiment. TEM stiffness is also much lower than measured. In the ETG single scale simulations the external flow shear is used to saturate the ETG streamers. Multi-scale simulations are ongoing, in which the ion zonal flows are the main saturating mechanism for ETGs. These costly simulations should provide the final answer on the importance of ETG-driven electron heat flux in JET. with JET contributors [F.Romanelli, Proc.25thIAEA FEC]. Supported by EUROfusion Grant 633053.

  1. Non-Fourier heat transport in metal-dielectric core-shell nanoparticles under ultrafast laser pulse excitation

    NASA Astrophysics Data System (ADS)

    Rashidi-Huyeh, M.; Volz, S.; Palpant, B.

    2008-09-01

    Relaxation dynamics of embedded metal nanoparticles after ultrafast laser pulse excitation is driven by thermal phenomena of different origins, the accurate description of which is crucial for interpreting experimental results: hot electron-gas generation, electron-phonon coupling, heat transfer to the particle environment, and heat propagation in the latter. Regarding this last mechanism, it is well known that heat transport in nanoscale structures and/or at ultrashort timescales may deviate from the predictions of the Fourier law. In these cases heat transport may rather be described by the Boltzmann transport equation. We present a numerical model allowing to determine the electron and lattice temperature dynamics in a spherical gold nanoparticle core under subpicosecond pulsed excitation as well as that in the surrounding shell dielectric medium. For this, we have used the electron-phonon coupling equation in the particle with a source term linked with the laser pulse absorption and the ballistic-diffusive equations for heat conduction in the host medium. Either thermalizing or adiabatic boundary conditions have been considered at the shell external surface. Our results show that the heat transfer rate from the particle to the matrix can be significantly smaller than the prediction of Fourier’s law. Consequently, the particle-temperature rise is larger and its cooling dynamics might be slower than that obtained by using Fourier’s law. This difference is attributed to the nonlocal and nonequilibrium heat conductions in the vicinity of the core nanoparticle. These results are expected to be of great importance for analyzing pump-probe experiments performed on single nanoparticles or nanocomposite media.

  2. Guide to the Revised Ground-Water Flow and Heat Transport Simulator: HYDROTHERM - Version 3

    USGS Publications Warehouse

    Kipp, Kenneth L.; Hsieh, Paul A.; Charlton, Scott R.

    2008-01-01

    The HYDROTHERM computer program simulates multi-phase ground-water flow and associated thermal energy transport in three dimensions. It can handle high fluid pressures, up to 1 ? 109 pascals (104 atmospheres), and high temperatures, up to 1,200 degrees Celsius. This report documents the release of Version 3, which includes various additions, modifications, and corrections that have been made to the original simulator. Primary changes to the simulator include: (1) the ability to simulate unconfined ground-water flow, (2) a precipitation-recharge boundary condition, (3) a seepage-surface boundary condition at the land surface, (4) the removal of the limitation that a specified-pressure boundary also have a specified temperature, (5) a new iterative solver for the linear equations based on a generalized minimum-residual method, (6) the ability to use time- or depth-dependent functions for permeability, (7) the conversion of the program code to Fortran 90 to employ dynamic allocation of arrays, and (8) the incorporation of a graphical user interface (GUI) for input and output. The graphical user interface has been developed for defining a simulation, running the HYDROTHERM simulator interactively, and displaying the results. The combination of the graphical user interface and the HYDROTHERM simulator forms the HYDROTHERM INTERACTIVE (HTI) program. HTI can be used for two-dimensional simulations only. New features in Version 3 of the HYDROTHERM simulator have been verified using four test problems. Three problems come from the published literature and one problem was simulated by another partially saturated flow and thermal transport simulator. The test problems include: transient partially saturated vertical infiltration, transient one-dimensional horizontal infiltration, two-dimensional steady-state drainage with a seepage surface, and two-dimensional drainage with coupled heat transport. An example application to a hypothetical stratovolcano system with unconfined

  3. Heat Transfer and Fluid Transport of Supercritical CO2 in Enhanced Geothermal System with Local Thermal Non-equilibrium Model

    DOE PAGES

    Zhang, Le; Luo, Feng; Xu, Ruina; ...

    2014-12-31

    The heat transfer and fluid transport of supercritical CO2 in enhanced geothermal system (EGS) is studied numerically with local thermal non-equilibrium model, which accounts for the temperature difference between solid matrix and fluid components in porous media and uses two energy equations to describe heat transfer in the solid matrix and in the fluid, respectively. As compared with the previous results of our research group, the effect of local thermal non-equilibrium mainly depends on the volumetric heat transfer coefficient ah, which has a significant effect on the production temperature at reservoir outlet and thermal breakthrough time. The uniformity of volumetricmore » heat transfer coefficient ah has little influence on the thermal breakthrough time, but the temperature difference become more obvious with time after thermal breakthrough with this simulation model. The thermal breakthrough time reduces and the effect of local thermal non-equilibrium becomes significant with decreasing ah.« less

  4. MHD thermosolutal marangoni convection heat and mass transport of power law fluid driven by temperature and concentration gradient

    NASA Astrophysics Data System (ADS)

    Jiao, Chengru; Zheng, Liancun; Ma, Lianxi

    2015-08-01

    This paper studies the magnetohydrodynamic (MHD) thermosolutal Marangoni convection heat and mass transfer of power-law fluids driven by a power law temperature and a power law concentration which is assumed that the surface tension varies linearly with both the temperature and concentration. Heat and mass transfer constitutive equation is proposed based on N-diffusion proposed by Philip and the abnormal convection-diffusion model proposed by Pascal in which we assume that the heat diffusion depends non-linearly on both the temperature and the temperature gradient and the mass diffusion depends non-linearly on both the concentration and the concentration gradient with modified Fourier heat conduction for power law fluid. The governing equations are reduced to nonlinear ordinary differential equations by using suitable similarity transformations. Approximate analytical solution is obtained using homotopy analytical method (HAM). The transport characteristics of velocity, temperature and concentration fields are analyzed in detail.

  5. Investigations on the heat transport capability of a cryogenic oscillating heat pipe and its application in achieving ultra-fast cooling rates for cell vitrification cryopreservation.

    PubMed

    Han, Xu; Ma, Hongbin; Jiao, Anjun; Critser, John K

    2008-06-01

    Theoretically, direct vitrification of cell suspensions with relatively low concentrations ( approximately 1 M) of permeating cryoprotective agents (CPA) is suitable for cryopreservation of almost all cell types and can be accomplished by ultra-fast cooling rates that are on the order of 10(6-7) K/min. However, the methods and devices currently available for cell cryopreservation cannot achieve such high cooling rates. In this study, we constructed a novel cryogenic oscillating heat pipe (COHP) using liquid nitrogen as its working fluid and investigated its heat transport capability to assess its application for achieving ultra-fast cooling rates for cell cryopreservation. The experimental results showed that the apparent heat transfer coefficient of the COHP can reach 2 x 10(5) W/m(2).K, which is two orders of the magnitude higher than traditional heat pipes. Theoretical analyzes showed that the average local heat transfer coefficient in the thin film evaporation region of the COHP can reach 1.2 x 10(6) W/m(2).K, which is approximately 10(3) times higher than that achievable with standard pool-boiling approaches. Based on these results, a novel device design applying the COHP and microfabrication techniques is proposed and its efficiency for cell vitrification is demonstrated through numerical simulation. The estimated average cooling rates achieved through this approach is 10(6-7)K/min, which is much faster than the currently available methods and sufficient for achieving vitrification with relatively low concentrations of CPA.

  6. Optimization of TCR and heat transport in group-IV multiple-quantum-well microbolometers

    NASA Astrophysics Data System (ADS)

    Morea, Matthew; Gu, Kevin; Savikhin, Victoria; Fenrich, Colleen S.; Pop, Eric; Harris, James S.

    2016-09-01

    Group-IV semiconductors have the opportunity to have an equivalent or better temperature coefficient of resistance (TCR) than other microbolometer thermistor materials. By using multiple-quantum-well (MQW) structures, their TCR values can be optimized due to a confinement of carriers. Through two approaches - an activation energy approximation and a custom Monte Carlo transfer matrix method - we simulated this effect for a combination of Group-IV semiconductors and their alloys (e.g., SiGe and GeSn) to find the highest possible TCR, while keeping in mind the critical thicknesses of such layers in a MQW epitaxial stack. We calculated the TCR for a critical-thickness-limited Ge0.8Sn0.2/Ge MQW device to be about -1.9 %/K. Although this TCR is lower than similar SiGe/Si MQW thermistors, GeSn offers possible advantages in terms of fabricating suspended devices with its interesting etch-stop properties shown in previous literature. Furthermore, using finite element modeling of heat transport, we looked at another key bolometer parameter: the thermal time constant. The dimensions of a suspended Ge microbolometer's supporting legs were fine-tuned for a target response time of 5 ms, incorporating estimations for the size effects of the nanowire-like legs on thermal conductivity.

  7. Bimodal Control of Heat Transport at Graphene–Metal Interfaces Using Disorder in Graphene

    NASA Astrophysics Data System (ADS)

    Kim, Jaehyeon; Khan, Muhammad Ejaz; Ko, Jae-Hyeon; Kim, Jong Hun; Lee, Eui-Sup; Suh, Joonki; Wu, Junqiao; Kim, Yong-Hyun; Park, Jeong Young; Lyeo, Ho-Ki

    2016-10-01

    Thermal energy transport across the interfaces of physically and chemically modified graphene with two metals, Al and Cu, was investigated by measuring thermal conductance using the time-domain thermoreflectance method. Graphene was processed using a He2+ ion-beam with a Gaussian distribution or by exposure to ultraviolet/O3, which generates structural or chemical disorder, respectively. Hereby, we could monitor changes in the thermal conductance in response to varying degrees of disorder. We find that the measured conductance increases as the density of the physical disorder increases, but undergoes an abrupt modulation with increasing degrees of chemical modification, which decreases at first and then increases considerably. Moreover, we find that the conductance varies inverse proportionally to the average distance between the structural defects in the graphene, implying a strong in-plane influence of phonon kinetics on interfacial heat flow. We attribute the bimodal results to an interplay between the distinct effects on graphene’s vibrational modes exerted by graphene modification and by the scattering of modes.

  8. Global heat transport scaling in plume-controlled regime in turbulent Rayleigh-Bénard convection

    NASA Astrophysics Data System (ADS)

    Chong, Kai Leong; Huang, Shi-Di; Xia, Ke-Qing

    2016-11-01

    Previous study by Chong et al. has introduced a normalized aspect-ratio Γ /Γopt (Γopt = 29 . 37 Ra - 0 . 31) where the plume coverage at fixed Γ /Γopt is invariant with respect to Ra in the so-called plume-controlled regime in Rayleigh-Bénard convection. We have studied the global heat transport scaling (expressed as Nusselt number Nu) at fixed Γ /Γopt with the Rayleigh number Ra between 107 and 1010 at fixed Prandtl number Pr = 4 . 38 by direct numerical simulations. It is found that at Γ /Γopt = 1 where the thermal plume becomes highly coherent and system-sized, Nu exhibits the scaling Nu - 1 Ra 0 . 327 +/- 0 . 001 over three decades of Ra . This scaling is different from that found at Γ = 1 for which Nu - 1 Ra 0 . 308 +/- 0 . 001 , and this difference in scaling can be shown evidently in the compensated plots. This work was supported by RGC of HKSAR (No. CUHK404513), CUHK Direct Grant (No. 3132740) and through a HKPhD Fellowship.

  9. Heat transport in low-Rossby-number Rayleigh-Bénard convection.

    PubMed

    Julien, Keith; Knobloch, Edgar; Rubio, Antonio M; Vasil, Geoffrey M

    2012-12-21

    We demonstrate, via simulations of asymptotically reduced equations describing rotationally constrained Rayleigh-Bénard convection, that the efficiency of turbulent motion in the fluid bulk limits overall heat transport and determines the scaling of the nondimensional Nusselt number Nu with the Rayleigh number Ra, the Ekman number E, and the Prandtl number σ. For E < 1 inviscid scaling theory predicts and simulations confirm the large Ra scaling law Nu-1 ≈ C(1)σ(-1/2)Ra(3/2)E(2), where C(1) is a constant, estimated as C(1) ≈ 0.04 ± 0.0025. In contrast, the corresponding result for nonrotating convection, Nu-1 ≈ C(2)Ra(α), is determined by the efficiency of the thermal boundary layers (laminar: 0.28 ≤ α ≤ 0.31, turbulent: α ~ 0.38). The 3/2 scaling law breaks down at Rayleigh numbers at which the thermal boundary layer loses rotational constraint, i.e., when the local Rossby number ≈ 1. The breakdown takes place while the bulk Rossby number is still small and results in a gradual transition to the nonrotating scaling law. For low Ekman numbers the location of this transition is independent of the mechanical boundary conditions.

  10. Modelling heat and moisture transport in the ANDRA/SKB temperature buffer test

    NASA Astrophysics Data System (ADS)

    Hökmark, H.; Ledesma, A.; Lassabatere, T.; Fälth, B.; Börgesson, L.; Robinet, J. C.; Sellali, N.; Sémété, P.

    The present paper regards heat and moisture transport in the barrier of the temperature buffer test (TBT) large-scale experiment. TBT includes two individually powered 1500 W heaters, vertically positioned on top of each other in a KBS-3 type disposal pit with 0.5 m of compacted MX80 bentonite in between. The experiment is run at high temperatures and with controlled hydraulic boundary conditions. This, and an extensive instrumentation of the barriers, makes the TBT experiment particularly suited for modelling and for testing and evaluation of different modelling approaches. This is in particular true for the two horizontal sections at the heater mid-height levels, where radial arrays of densely spaced thermocouples allow for accurate direct monitoring of the temperature development and for monitoring of the saturation development with indirect interpretation methods. Examples of early predictions, given by a number of modelling teams using different codes and different approaches, are presented in the paper. Comparisons are made between different sets of modelling results and measurements.

  11. Turbulent heating and cross-field transport near the magnetopause from THEMIS

    NASA Astrophysics Data System (ADS)

    Chaston, C.; Bonnell, J.; McFadden, J. P.; Carlson, C. W.; Cully, C.; Le Contel, O.; Roux, A.; Auster, H. U.; Glassmeier, K. H.; Angelopoulos, V.; Russell, C. T.

    2008-05-01

    We demonstrate that the low frequency broadband magnetic fluctuations observed during THEMIS spacecraft traversals near the Earth's magnetopause may be described as a turbulent spectrum of Doppler shifted kinetic Alfvén waves (KAWs). These waves are most intense along reconnected flux-tubes in the magnetosheath just outside the magnetopause. We identify distinct power-law scalings of wave spectral energy density in wavenumber and show that Landau (LD) and transit time damping (TD) on ions and electrons is largest at the wavenumber where the power-law index changes. The threshold amplitude for stochastic ion scattering/acceleration is also exceeded by these waves. These acceleration processes are manifest in observations of field-aligned and transverse heating of electrons and ions respectively. From integration over the range of observed wavenumbers we show that, if the wave-normal angles are sufficiently large, these waves can provide diffusive transport of magnetosheath plasmas across the magnetopause at up to the Bohm rate.

  12. Bimodal Control of Heat Transport at Graphene–Metal Interfaces Using Disorder in Graphene

    PubMed Central

    Kim, Jaehyeon; Khan, Muhammad Ejaz; Ko, Jae-Hyeon; Kim, Jong Hun; Lee, Eui-Sup; Suh, Joonki; Wu, Junqiao; Kim, Yong-Hyun; Park, Jeong Young; Lyeo, Ho-Ki

    2016-01-01

    Thermal energy transport across the interfaces of physically and chemically modified graphene with two metals, Al and Cu, was investigated by measuring thermal conductance using the time-domain thermoreflectance method. Graphene was processed using a He2+ ion-beam with a Gaussian distribution or by exposure to ultraviolet/O3, which generates structural or chemical disorder, respectively. Hereby, we could monitor changes in the thermal conductance in response to varying degrees of disorder. We find that the measured conductance increases as the density of the physical disorder increases, but undergoes an abrupt modulation with increasing degrees of chemical modification, which decreases at first and then increases considerably. Moreover, we find that the conductance varies inverse proportionally to the average distance between the structural defects in the graphene, implying a strong in-plane influence of phonon kinetics on interfacial heat flow. We attribute the bimodal results to an interplay between the distinct effects on graphene’s vibrational modes exerted by graphene modification and by the scattering of modes. PMID:27698372

  13. Numerical simulation of heat and mass transport during space crystal growth with MEPHISTO

    NASA Technical Reports Server (NTRS)

    Yao, Minwu; Raman, Raghu; Degroh, Henry C., III

    1995-01-01

    The MEPHISTO space experiments are collaborative United States and French investigations aimed at understanding the fundamentals of crystal growth. Microgravity experiments were conducted aboard the USMP-1 and -2 missions on STS-52 and 62 in October 1992 and March 1994 respectively. MEPHISTO is a French designed and built Bridgman type furnace which uses the Seebeck technique to monitor the solid/liquid interface temperature and Peltier pulsing to mark the location and shape of the solid/liquid interface. In this paper the Bridgman growth of Sn-Bi and Bi-Sn under terrestrial and microgravity conditions is modeled using the finite element code, FIDAP*. The numerical model considers fully coupled heat and mass transport, fluid motion and solid/liquid phase changes in the crystal growth process. The primary goals of this work are: to provide a quantitative study of the thermal buoyancy-induced convection in the melt for the two flight experiments; to compare the vertical and horizontal growth configurations and systematically evaluate the effects of various gravity levels on the solute segregation. Numerical results of the vertical and horizontal Bridgman growth configurations are presented.

  14. Tropical Cyclone-Induced Ocean Mixing, Ocean Heat Transport, and the Potential for Climatic Feedbacks

    NASA Astrophysics Data System (ADS)

    Sriver, R. L.; Huber, M.

    2006-12-01

    Ocean heat transport (OHT) is an important physical process that influences Earth's climate. Ocean mixing is considered to be a critical component in driving OHT, but potential climatic feedbacks between mixing and OHT are poorly understood. Tropical cyclones (TC)s are efficient ocean mixers, as evidenced by the cold wakes left behind these storms, and may substantially contribute to driving OHT (Emanuel, 2001). Furthermore, recent studies propose that TC activity is linked to the climate system via tropical sea surface temperature (SST) (Emanuel, 2005; Webster et al., 2005; Sriver and Huber, 2006), thus exposing a potential climatic feedback between global TC activity and OHT. Here we use near surface wind and SST data from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis project (ERA-40) to investigate the relationship between globally integrated TC winds, TC-induced OHT, and mean annual tropical SST over the last 25 years. We show that the time series for these quantities exhibit agreement, and TC-induced OHT is extremely sensitive to changes in tropical SST. Results suggest future increases in SST will be accompanied by an increase in global TC activity and increased OHT.

  15. Coupled Soil Water and Heat Transport Near the Land Surface in Arid and Semiarid Regions - Multi-Domain Modeling

    NASA Astrophysics Data System (ADS)

    Mohanty, Binayak; Yang, Zhenlei

    2016-04-01

    Understanding and simulating coupled water and heat transfer appropriately in the shallow subsurface is of vital significance for accurate prediction of soil evaporation that would improve the coupling between land surface and atmosphere, which consequently could enhance the reliability of weather as well as climate forecast. The theory of Philip and de Vries (1957), accounting for water vapor diffusion only, was considered physically incomplete and consequently extended and improved by several researchers by explicitly taking water vapor convection, dispersion or air flow into account. It is generally believed that the soil moisture is usually low in the near surface layer under highly transient field conditions, particularly in arid and semiarid regions, and that accurate characterization of water vapor transport is critical when modeling simultaneous water and heat transport in the shallow field soils. The first objective of this study is thus mainly to test existing coupled water and heat transport theories and to develop reasonable and simplified numerical models using field experimental data collected under semi-arid and arid hydro-climatic conditions. In addition, more complex multi-domain models are developed for ubiquitous heterogeneous terrestrial surfaces such as horizontal textural contrasts or structured heterogeneity including macropores (fractures, cracks, root channels, etc.). This would make coupled water and heat transfer models applicable in such non-homogeneous soils more meaningful and enhance the skill of land-atmosphere interaction models at a larger context.

  16. Nonlinear heat-transport equation beyond Fourier law: application to heat-wave propagation in isotropic thin layers

    NASA Astrophysics Data System (ADS)

    Sellitto, A.; Tibullo, V.; Dong, Y.

    2017-03-01

    By means of a nonlinear generalization of the Maxwell-Cattaneo-Vernotte equation, on theoretical grounds we investigate how nonlinear effects may influence the propagation of heat waves in isotropic thin layers which are not laterally isolated from the external environment. A comparison with the approach of the Thermomass Theory is made as well.

  17. The role of parallel heat transport in the relation between upstream scrape-off layer widths and target heat flux width in H-mode plasmas of NSTX.

    SciTech Connect

    Ahn, J W; Boedo, J A; Maingi, R; Soukhanovskii, V A

    2009-01-05

    The physics of parallel heat transport was tested in the Scrape-off Layer (SOL) plasma of the National Spherical Torus Experiment (NSTX) [M. Ono, et al., Nucl. Fusion 40, 557 (2000) and S. M. Kaye, et al., Nucl. Fusion 45, S168 (2005)] tokamak by comparing the upstream electron temperature (T{sub e}) and density (n{sub e}) profiles measured by the mid-plane reciprocating probe to the heat flux (q{sub {perpendicular}}) profile at the divertor plate measured by an infrared (IR) camera. It is found that electron conduction explains the near SOL width data reasonably well while the far SOL, which is in the sheath limited regime, requires an ion heat flux profile broader than the electron one to be consistent with the experimental data. The measured plasma parameters indicate that the SOL energy transport should be in the conduction-limited regime for R-R{sub sep} (radial distance from the separatrix location) < 2-3 cm. The SOL energy transport should transition to the sheath-limited regime for R-R{sub sep} > 2-3cm. The T{sub e}, n{sub e}, and q{sub {perpendicular}} profiles are better described by an offset exponential function instead of a simple exponential. The conventional relation between mid plane electron temperature decay length ({lambda}{sub Te}) and target heat flux decay length ({lambda}{sub q}) is {lambda}{sub Te} = 7/2{lambda}{sub q}, whereas the newly-derived relation, assuming offset exponential functional forms, implies {lambda}{sub Te} = (2-2.5){lambda}{sub q}. The measured values of {lambda}{sub Te}/{lambda}{sub q} differ from the new prediction by 25-30%. The measured {lambda}{sub q} values in the far SOL (R-R{sub sep} > 2-3cm) are 9-10cm, while the expected values are 2.7 < {lambda}{sub q} < 4.9 cm (for sheath-limited regime). We propose that the ion heat flux profile is substantially broader than the electron heat flux profile as an explanation for this discrepancy in the far SOL.

  18. Heat transport and dynamics of the large-scale circulation of turbulent Rayleigh-Benard convection

    NASA Astrophysics Data System (ADS)

    Brown, Eric

    Experimental studies of turbulent Rayleigh-Benard convection in cylindrical water-filled containers of equal height and diameter, with an applied vertical temperature difference DeltaT are presented. High-precision measurements of the heat flux Q were shown to agree with the Grossman-Lohse (GL) scaling model of thermal convection for small DeltaT, but for large DeltaT a regime was reached where Q ∝ DeltaT 1/3 in disagreement with the GL model. A prediction that the heat transport in the fluid would be reduced for endplates with finite conductivity was confirmed by switching out plates with different thermal conductivities. The effect of the spatial variation of fluid properties with temperature was measured by comparing experiments in samples of different sizes with the same dimensionless control parameters but different DeltaT. Thermistors on the sidewall were used to measure various aspects of the large-scale circulation (LSC). The turnover and an azimuthally twisting oscillatory mode were found to have the same frequency for small DeltaT which agrees with the GL model, but the frequencies were found to differ from each other and from the GL model for large DeltaT. The azimuthal orientation theta0(t) of the LSC was found to meander in time as a diffusive process over long time scales. In addition it contained spontaneous events in which the orientation changed by a large angle Deltatheta, either by a rotation of the circulation plane, or by a cessation of the circulation followed by a restart in a randomly chosen direction as seen by the uniform probability distribution p(Deltatheta). Rotations occurred with a monotonically decreasing p(Deltatheta). The distribution of rotations and cessations in time followed Poissonian statistics. Also presented is a model of the dynamics of the LSC consisting of a pair of stochastic differential equations motivated by the Navier-Stokes equations. The equations have terms representing buoyancy, drag, and angular momentum of

  19. Combining in-situ measurements and altimetry to estimate volume, heat and salt transport variability through the Faroe Shetland Channel

    NASA Astrophysics Data System (ADS)

    Berx, B.; Hansen, B.; Østerhus, S.; Larsen, K. M.; Sherwin, T.; Jochumsen, K.

    2013-01-01

    From 1994 to 2011, instruments measuring ocean currents (ADCPs) have been moored on a section crossing the Faroe-Shetland Channel. Together with CTD (Conductivity Temperature Depth) measurements from regular research vessel occupations, they describe the flow field and water mass structure in the channel. Here, we use these data to calculate the average volume transport and properties of the flow of warm water through the channel from the Atlantic towards the Arctic, termed the Atlantic inflow. We find the average volume transport of this flow to be 2.7 ± 0.5 Sv (1 Sv = 106 m3 s-1) between the shelf edge on the Faroe side and the 150 m isobath on the Shetland side. The average heat transport (relative to 0 °C) was estimated to be 107 ± 21 TW and the average salt import to be 98 ± 20 × 106 kg s-1. Transport values for individual months, based on the ADCP data, include a large level of variability, but can be used to calibrate sea level height data from satellite altimetry. In this way, a time series of volume transport has been generated back to the beginning of satellite altimetry in December 1992. The Atlantic inflow has a seasonal variation in volume transport that peaks around the turn of the year and has an amplitude of 0.7 Sv. The Atlantic inflow has become warmer and more saline since 1994, but no equivalent trend in volume transport was observed.

  20. KPNA3-knockdown eliminates the second heat shock protein peak associated with the heat shock response of male silkworm pupae (Bombyx mori) by reducing heat shock factor transport into the nucleus.

    PubMed

    Li, Jun; Wei, Guoqing; Wang, Lei; Qian, Cen; Li, Kedong; Zhang, Congfen; Dai, Lishang; Sun, Yu; Liu, Dongran; Zhu, Baojian; Liu, Chaoliang

    2016-01-10

    In this study, we investigated the role of karyopherin alpha 3 in the heat shock response in male silkworm pupae. Karyopherin alpha recognizes the classical nuclear location sequence on proteins and transports them into the nucleus by forming a trimetric complex with karyopherin beta. Three predicted karyopherin alphas (KPNA1, KPNA2 and KPNA3) have been identified from the silkworm Bombyx mori. Pull-down assay result showed that KPNA3 can pull down heat shock transcription factor (HSF) from proteins extracted from tissues using non-denature lysis buffer. After 45 °C heat shock on male B. mori pupae for 30 min, we identified two heat shock protein (HSP) mRNA expression peaks correlating with HSP19.9, HSP20.4 and HSP25.4 at 4 h (peak 1) and 24 h (peak 2). The second peak was eliminated after knockdown of KPNA3. Similar results were obtained following knockdown of HSF, which is the trans-activating factor of heat shock. However, KPNA3 knockdown was not accompanied by the decreased HSF protein levels at 24 h after heat shock which were observed following HSF knockdown. We also expressed recombinant protein GST-KPNA3 and His-HSF in Escherichia coli to perform GST pull-down assay and the result confirmed the interaction between KPNA3 and HSF. We concluded that KPNA3 knockdown eliminates the second heat shock protein peak in the heat shock response of male silkworm pupae by reducing HSF transport into the nucleus.

  1. SODIUM-WATER HEAT EXCHANGER

    DOEpatents

    Simmons, W.R.; Koch, L.J.

    1962-04-17

    A heat exchanger comprising a tank for hot liquid and a plurality of concentric, double tubes for cool liquid extending vertically through the tank is described. These tubes are bonded throughout most of their length but have an unbonded portion at both ends. The inner tubes extend between headers located above and below the tanmk and the outer tubes are welded into tube sheets forming the top and bottom of the tank at locations in the unbonded portions of the tubes. (AEC)

  2. Gap structure of iron-pnictide superconductors from low-temperature heat transport

    NASA Astrophysics Data System (ADS)

    Reid, Jean-Philippe

    2010-03-01

    The structure of the superconducting gap provides important clues on the symmetry of the order parameter and the pairing mechanism. Here I describe how measurements of the thermal conductivity at very low temperature can be used to determine whether nodes are present in the gap function of a particular superconductor, and how the application of a magnetic field probes the low-energy quasiparticle excitations. Measurements on hole-doped and electron-doped pnictide superconductors, Ba1-xKxFe2As2 [1] and Ba(Fe1-xCox)2As2 [2], reveal a negligible residual linear term at T->0, showing that the gap of these two superconductors has no nodes, at least in the basal plane. In both pnictides, a small field is found to be very effective in exciting quasiparticles, showing that the gap must be very small in some direction on the Fermi surface. In Ba(Fe1-xCox)2As2, the evolution with doping x is as follows: at low x, the gap is large everywhere on the Fermi surface, and beyond optimal doping the minimum gap becomes progressively smaller. I discuss what these features tell us about the nature of the superconducting state in pnictide superconductors. * Measurements of heat transport performed in collaboration with X.-G. Luo, H. Shakeripour, M.A. Tanatar, N. Doiron-Leyraud and L. Taillefer. [1] X.-G. Luo et al., Phys. Rev. B 80, 140503 (2009). [2] M.A. Tanatar et al., arXiv:0907.1276.

  3. Exploring electron beam induced heat and mass transport at the atomic scale

    NASA Astrophysics Data System (ADS)

    Kisielowski, Christian

    2011-03-01

    In recent years the performance of mid-voltage electron microscopes was significantly boosted to reach deep sub-Ångstrom resolution around 0.5 Å at 300 kV in broad beam (TEM) and focused probe (STEM) modes. Atomic resolution microscopy at voltages as low as 50 kV (and possibly below) was fostered. As a result the detection of single atoms across the Periodic Table of Elements is now possible even if light atoms are considered. After decades of striving for resolution enhancement, electron microscopy has now reached a limit that is given at a fundamental level by the Coulomb scattering process itself and by beam-sample interactions, which set a maximum dose limit that can be easily reached for soft and hard materials with the developed high-brightness electron guns. Consequently, new frontiers for electron microscopy emerge and this contribution addresses dynamic processes at the single atom level that can now be captured in time series of images at frequencies below 1 Hz reaching towards kHz. In this frequency range much of the observed atom dynamics is electron beam induced and the control of beam-sample interaction imposes constraints as well as opportunities. In this contribution it is shown that it seems feasible to exploit beam sample interactions to gain better insight into heat and mass transport in soft and hard matter at atomic resolution. This work was supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  4. The role of oceanic heat transport in abrupt millennial-scale climate transitions

    NASA Astrophysics Data System (ADS)

    Arzel, Olivier; de Verdière, Alain Colin; England, Matthew H.

    2010-05-01

    The last glacial period was punctuated by rapid climate shifts, known as Dansgaard-Oeschger events, with strong imprint in the North Atlantic sector suggesting that they were linked with the Atlantic Meridional Overturning Circulation. Here an idealized single-hemisphere three-dimensional ocean-atmosphere-sea ice coupled model is used to explore the possible origin of the instability driving these abrupt events and to provide a plausible explanation for the relative stability of the Holocene. Focusing on the physics of noise-free millennial oscillations under steady external (solar) forcing, we show that cold climates become unstable, that is, exhibit abrupt millennial-scale transitions, for significantly lower freshwater fluxes than warm climates, in agreement with previous studies making use of zonally-averaged coupled models. This fundamental difference is a direct consequence of the weaker temperature stratification of the glacial ocean, mainly caused by upper ocean cooling. With similar overturning strengths between the cold and warm climates, this weaker temperature stratification implies a weaker baroclinic heat transport that ultimately leads to a weaker stabilization of the circulation by the negative temperature advection feedback. Using a two-hemisphere configuration of a coupled climate model of intermediate complexity, we show that this result is robust to the added presence of a bottom water mass of southern origin. The analysis reveals that under particular conditions, a pronounced interdecadal variability develops during warm interstadials, with maximum variance in the northern extension of the western boundary current in the North Atlantic. While the nature of the instability driving the millennial oscillations is identical to that found in ocean models under mixed boundary conditions, these interstadial-interdecadal oscillations share the same characteristics as those previously found in ocean models forced by fixed surface fluxes: they originate

  5. Transport Properties of Bulk Thermoelectrics: An International Round-Robin Study, Part II: Thermal Diffusivity, Specific Heat, and Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Wang, Hsin; Porter, Wallace D.; Böttner, Harald; König, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolet, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Patricia; Sharp, Jeff; Lo, Jason; Kleinke, Holger; Kiss, Laszlo

    2013-06-01

    For bulk thermoelectrics, improvement of the figure of merit ZT to above 2 from the current values of 1.0 to 1.5 would enhance their competitiveness with alternative technologies. In recent years, the most significant improvements in ZT have mainly been due to successful reduction of thermal conductivity. However, thermal conductivity is difficult to measure directly at high temperatures. Combined measurements of thermal diffusivity, specific heat, and mass density are a widely used alternative to direct measurement of thermal conductivity. In this work, thermal conductivity is shown to be the factor in the calculation of ZT with the greatest measurement uncertainty. The International Energy Agency (IEA) group, under the implementing agreement for Advanced Materials for Transportation (AMT), has conducted two international round-robins since 2009. This paper, part II of our report on the international round-robin testing of transport properties of bulk bismuth telluride, focuses on thermal diffusivity, specific heat, and thermal conductivity measurements.

  6. Initial exploration of scenarios with Internal Transport Barrier in the first NBI-heated L-mode TCV plasmas

    NASA Astrophysics Data System (ADS)

    Piron, Chiara; Sauter, Olivier; Coda, Stefano; Merle, Antoine; Karpushov, Alexander; Pigatto, Leonardo; Bolzonella, Tommaso; Piovesan, Paolo; Vianello, Nicola; TCV Team; EUROfusion MST1 Team

    2016-10-01

    Fully non-inductive operation of high performance plasmas is one of the main objectives of contemporary Tokamak research. In this perspective, plasmas with Internal Transport Barriers (ITBs) are an attractive scenario, since they can attain a high fraction of bootstrap current. In this work we start exploring ITB scenarios on the Tokamak à Configuration Variable (TCV) heated by a newly available 1MW Neutral Beam Injector (NBI). Here we investigate for the first time in this device the impact of the additional NBI power on the performance and stability of L-mode plasmas with ITBs. Results of both experimental data analyses and ASTRA transport simulations are presented. The work examines also the Magneto Hydro-Dynamics (MHD) activity and stability of the explored plasmas. In particular, the role of plasma magnetic equilibrium parameters, such as plasma elongation and triangularity, on the sustainment of these NBI-heated ITB scenarios is discussed.

  7. An inexact Newton method for fully-coupled solution of the Navier-Stokes equations with heat and mass transport

    SciTech Connect

    Shadid, J.N.; Tuminaro, R.S.; Walker, H.F.

    1997-02-01

    The solution of the governing steady transport equations for momentum, heat and mass transfer in flowing fluids can be very difficult. These difficulties arise from the nonlinear, coupled, nonsymmetric nature of the system of algebraic equations that results from spatial discretization of the PDEs. In this manuscript the authors focus on evaluating a proposed nonlinear solution method based on an inexact Newton method with backtracking. In this context they use a particular spatial discretization based on a pressure stabilized Petrov-Galerkin finite element formulation of the low Mach number Navier-Stokes equations with heat and mass transport. The discussion considers computational efficiency, robustness and some implementation issues related to the proposed nonlinear solution scheme. Computational results are presented for several challenging CFD benchmark problems as well as two large scale 3D flow simulations.

  8. Tracer dye transport from a well fitted with a downhole heat exchanger, Klamath Falls, Oregon

    SciTech Connect

    Dunstall, M.G.

    1990-02-01

    Low or medium temperature geothermal resources are often used for space and domestic hot water heating. If the resource is located at reasonably shallow depths and adjacent to a major population centre large amounts of relatively cheap, clean heat can be provided. Geothermal fluid is often brought to the surface, either under natural artesian pressure or by pumping, to be used in surface heat exchangers (SHEs). This method generally requires a second well for disposal of the cooled fluid and a substantial capital outlay for pumps and heat exchangers. Large amounts of heat can be extracted from just one or two wells using surface heat exchangers and the method can prove very cost effective in areas with a high density of energy intensive users. For smaller heat loads surface heat exchangers can become expensive and in many instances a downhole heat exchanger (DHE) installed directly in the well bore is capable of supplying cheap heat to a smaller number of users. This report first describes the methods used to carry out the series of dye tests, from well selection to injection of the dye samples. It then discusses the results of these tests in terms of how much dye was recovered, where it was recovered from and how long it took to arrive. The results of the concurrent temperature monitoring work and DHE heat output performance are also presented. Some recommendations are made for any future testing. 13 refs., 42 figs.

  9. Permanent El Nino Conditions in the Early Pliocene, the Poleward Heat Transport Paradox, and Contemporary Global Warming.

    NASA Astrophysics Data System (ADS)

    Fedorov, A. V.; Brierley, C.

    2007-12-01

    Proxy temperature records show that in the early Pliocene, approximately 3 to 5 million years ago, the tropics were characterized by permanently warm El Nino-like conditions. The equatorial Pacific was as warm as in the east as it is in the west today, and the zonal SST gradient along the equator was significantly reduced or absent. Concurrently, major coastal upwelling regions were up to 10 degrees C warmer than they are today. The globally averaged temperatures of the Earth's surface were also substantially higher. This climate state persisted even though the external factors that control climate were essentially the same as at present and the Earth was experiencing greenhouse conditions similar to today's, with the concentration of CO2 in the atmosphere comparable to present day values. Thus far, there is no satisfactory explanation for the climate state of the Pliocene, especially for the climate conditions in the tropics and subtropics. State-of-the-art climate models fail to reproduce a permanent El Nino even when forced by CO2 concentrations many times larger than those estimated for the early Pliocene. Predicting the impact on the tropics of global warming caused by anthropogenic factors also remains a serious challenge for climate scientists. Coupled general circulation models yield a wide range of possible scenarios for the region, but many suggest a slightly higher likelihood of an El Nino-like state in global warming. Efforts to predict future global warming should benefit enormously from a better understanding of the state of permanent El Nino which imposes a strong dynamical constraint on both oceanic and atmospheric circulations. Modeling permanent El Nino with atmospheric and oceanic GCMs reveals a poleward heat transport paradox: Calculations with ocean-only models suggest that a permanent El Nino should correspond to a reduced poleward heat transport by the ocean. This is related to a deeper thermocline in the eastern equatorial Pacific, which

  10. Role of Te/Ti and ∇vtor in ion heat transport of ASDEX Upgrade H-mode plasmas

    NASA Astrophysics Data System (ADS)

    Manini, A.; Angioni, C.; Peeters, A. G.; Ryter, F.; Jacchia, A.; Maggi, C. F.; Suttrop, W.; ASDEX Upgrade Team

    2006-12-01

    Experiments in H-mode plasmas have shown that both heat and particle transport are sensitive to the ratio between electron and ion temperature (Te/Ti). While decreasing Te/Ti is beneficial for confinement, an increased electron heating in these so called 'hot ion plasmas' deteriorates the confinement. H-mode plasmas with low Te/Ti are often accompanied by high toroidal rotation velocity (vphi). Its gradient (∇vphi) can destabilize the ion temperature gradient mode (ITG) through its parallel component in the parallel velocity shear, but it has also stabilizing effects since it produces an E × B shearing rate (ωE × B). In this paper, the effects of electron heating on the ion heat transport is investigated in H-mode plasmas heated by neutral beam injection (NBI) and electron cyclotron heating (ECH). In particular, the correlation on Te/Ti and ∇vphi is studied and compared with calculations made with GLF23 and GS2. Experimentally it is shown that the normalized gradient length of the ions ( R/L_{T_{\\rmi}} ) is correlated with both Te/Ti and ∇vphi: peaked ion temperature profiles are only obtained with low Te/Ti and high ∇vphi, and vice-versa. When ECH is added, both ion heat and momentum transport are enhanced, leading to a drop of both the Ti and vphi profiles. The effective growth rate γeff = γ-ωE × B is calculated, with the mode growth rate γ determined with GS2 and ωE × B with GLF23. The ion transport is enhanced due to the decrease of the ITG R/L_{T_{\\rmi}} threshold with increasing Te/Ti. Comparison of the dependence of R/L_{T_{\\rmi}} on Te/Ti and ∇vphi between experiments and modelling indicates that the deterioration of confinement cannot be explained by the changes in only Te/Ti or ∇vphi, but by the combined effects of both parameters. The changes in Te/Ti act directly on the ITG threshold, while the ones in ∇vphi modify the ωE × B shearing rate leading to changes in the effective threshold.

  11. Controls on permafrost thaw in a coupled groundwater-flow and heat-transport system: Iqaluit Airport, Nunavut, Canada

    NASA Astrophysics Data System (ADS)

    Shojae Ghias, Masoumeh; Therrien, René; Molson, John; Lemieux, Jean-Michel

    2016-12-01

    Numerical simulations of groundwater flow and heat transport are used to provide insight into the interaction between shallow groundwater flow and thermal dynamics related to permafrost thaw and thaw settlement at the Iqaluit Airport taxiway, Nunavut, Canada. A conceptual model is first developed for the site and a corresponding two-dimensional numerical model is calibrated to the observed ground temperatures. Future climate-warming impacts on the thermal regime and flow system are then simulated based on climate scenarios proposed by the Intergovernmental Panel on Climate Change (IPCC). Under climate warming, surface snow cover is identified as the leading factor affecting permafrost degradation, including its role in increasing the sensitivity of permafrost degradation to changes in various hydrogeological factors. In this case, advective heat transport plays a relatively minor, but non-negligible, role compared to conductive heat transport, due to the significant extent of low-permeability soil close to surface. Conductive heat transport, which is strongly affected by the surface snow layer, controls the release of unfrozen water and the depth of the active layer as well as the magnitude of thaw settlement and frost heave. Under the warmest climate-warming scenario with an average annual temperature increase of 3.23 °C for the period of 2011-2100, the simulations suggest that the maximum depth of the active layer will increase from 2 m in 2012 to 8.8 m in 2100 and, over the same time period, thaw settlement along the airport taxiway will increase from 0.11 m to at least 0.17 m.

  12. On the Sensitivity of Atmospheric Model Implied Ocean Heat Transport to the Dominant Terms of the Surface Energy Balance

    SciTech Connect

    Gleckler, P J

    2004-11-03

    The oceanic meridional heat transport (T{sub o}) implied by an atmospheric General Circulation Model (GCM) can help evaluate a model's readiness for coupling with an ocean GCM. In this study we examine the T{sub o} from benchmark experiments of the Atmospheric Model Intercomparison Project, and evaluate the sensitivity of T{sub o} to the dominant terms of the surface energy balance. The implied global ocean TO in the Southern Hemisphere of many models is equatorward, contrary to most observationally-based estimates. By constructing a hybrid (model corrected by observations) T{sub o}, an earlier study demonstrated that the implied heat transport is critically sensitive to the simulated shortwave cloud radiative effects, which have been argued to be principally responsible for the Southern Hemisphere problem. Systematic evaluation of one model in a later study suggested that the implied T{sub o} could be equally as sensitive to a model's ocean surface latent heat flux. In this study we revisit the problem with more recent simulations, making use of estimates of ocean surface fluxes to construct two additional hybrid calculations. The results of the present study demonstrate that indeed the implied T{sub o} of an atmospheric model is very sensitive to problems in not only the surface net shortwave, but the latent heat flux as well. Many models underestimate the shortwave radiation reaching the surface in the low latitudes, and overestimate the latent heat flux in the same region. The additional hybrid transport calculations introduced here could become useful model diagnostic tests as estimates of implied ocean surface fluxes are improved.

  13. In-situ measurement of the heat transport in defect- engineered free-standing single-layer graphene

    PubMed Central

    Wang, Haidong; Kurata, Kosaku; Fukunaga, Takanobu; Takamatsu, Hiroshi; Zhang, Xing; Ikuta, Tatsuya; Takahashi, Koji; Nishiyama, Takashi; Ago, Hiroki; Takata, Yasuyuki

    2016-01-01

    Utilizing nanomachining technologies, it is possible to manipulate the heat transport in graphene by introducing different defects. However, due to the difficulty in suspending large-area single-layer graphene (SLG) and limited temperature sensitivity of the present probing methods, the correlation between the defects and thermal conductivity of SLG is still unclear. In this work, we developed a new method for fabricating micro-sized suspended SLG. Subsequently, a focused ion beam (FIB) was used to create nanohole defects in SLG and tune the heat transport. The thermal conductivity of the same SLG before and after FIB radiation was measured using a novel T-type sensor method on site in a dual-beam system. The nanohole defects decreased the thermal conductivity by about 42%. It was found that the smaller width and edge scrolling also had significant restriction on the thermal conductivity of SLG. Based on the calculation results through a lattice dynamics theory, the increase of edge roughness and stronger scattering on long-wavelength acoustic phonons are the main reasons for the reduction in thermal conductivity. This work provides reliable data for understanding the heat transport in a defective SLG membrane, which could help on the future design of graphene-based electrothermal devices. PMID:26906476

  14. Confining interparticle potential makes both heat transport and energy diffusion anomalous in one-dimensional phononic systems

    NASA Astrophysics Data System (ADS)

    Kosevich, Yuriy A.; Savin, Alexander V.

    2016-10-01

    We provide molecular dynamics simulation of heat transport and energy diffusion in one-dimensional molecular chains with different interparticle pair potentials at zero and non-zero temperature. We model the thermal conductivity (TC) and energy diffusion (ED) in the chain of coupled rotators and in the Lennard-Jones chain either without or with the confining parabolic interparticle potential. The considered chains without the confining potential have normal TC and ED at non-zero temperature, while the corresponding chains with the confining potential are characterized by anomalous (diverging with the system length) TC and superdiffusion of energy. Similar effect is produced by the anharmonic quartic confining pair potential. We confirm in such a way that, surprisingly, the confining pair potential makes both heat transport and energy diffusion anomalous in one-dimensional phononic systems. We show that the normal TC is always accompanied by the normal ED in the thermalized anharmonic chains, while the superdiffusion of energy occurs in the thermalized chains with only anomalous heat transport.

  15. Thermophobicity of liquids: Heats of transport in mixtures as pure component properties—The case of arbitrary concentration

    NASA Astrophysics Data System (ADS)

    Hartmann, S.; Wittko, G.; Schock, F.; Groß, W.; Lindner, F.; Köhler, W.; Morozov, K. I.

    2014-10-01

    We have measured Soret coefficients of a large number of binary mixtures of 23 different organic solvents. The present analysis is based on 77 equimolar mixtures and strongly supports the thermophobicity concept previously developed for the heats of transport of originally 10 different substances [S. Hartmann, G. Wittko, W. Köhler, K. I. Morozov, K. Albers, and G. Sadowski, Phys. Rev. Lett. 109, 065901 (2012)]. Among the investigated compounds, cis-decalin is the most thermophobic, hexane the most thermophilic one. In addition to the equimolar mixtures, we have also analyzed the composition dependence of the Soret coefficients and the heats of transport for 22 selected binary mixtures. Both the interpretation of the heats of transport in equimolar mixtures as pure component thermophobicities and the composition dependence of the Soret coefficient can be understood on the basis of the thermodiffusion theory developed by Morozov [Phys. Rev. E 79, 031204 (2009)], according to which the composition dependence is determined by the excess volume of mixing.

  16. Observational constraints on atmospheric and oceanic cross-equatorial heat transports: revisiting the precipitation asymmetry problem in climate models

    NASA Astrophysics Data System (ADS)

    Loeb, Norman G.; Wang, Hailan; Cheng, Anning; Kato, Seiji; Fasullo, John T.; Xu, Kuan-Man; Allan, Richard P.

    2016-05-01

    Satellite based top-of-atmosphere (TOA) and surface radiation budget observations are combined with mass corrected vertically integrated atmospheric energy divergence and tendency from reanalysis to infer the regional distribution of the TOA, atmospheric and surface energy budget terms over the globe. Hemispheric contrasts in the energy budget terms are used to determine the radiative and combined sensible and latent heat contributions to the cross-equatorial heat transports in the atmosphere (AHTEQ) and ocean (OHTEQ). The contrast in net atmospheric radiation implies an AHTEQ from the northern hemisphere (NH) to the southern hemisphere (SH) (0.75 PW), while the hemispheric difference in sensible and latent heat implies an AHTEQ in the opposite direction (0.51 PW), resulting in a net NH to SH AHTEQ (0.24 PW). At the surface, the hemispheric contrast in the radiative component (0.95 PW) dominates, implying a 0.44 PW SH to NH OHTEQ. Coupled model intercomparison project phase 5 (CMIP5) models with excessive net downward surface radiation and surface-to-atmosphere sensible and latent heat transport in the SH relative to the NH exhibit anomalous northward AHTEQ and overestimate SH tropical precipitation. The hemispheric bias in net surface radiative flux is due to too much longwave surface radiative cooling in the NH tropics in both clear and all-sky conditions and excessive shortwave surface radiation in the SH subtropics and extratropics due to an underestimation in reflection by clouds.

  17. Quantum heat transport of a two-qubit system: Interplay between system-bath coherence and qubit-qubit coherence

    SciTech Connect

    Kato, Akihito Tanimura, Yoshitaka

    2015-08-14

    We consider a system consisting of two interacting qubits that are individually coupled to separate heat baths at different temperatures. The quantum effects in heat transport are investigated in a numerically rigorous manner with a hierarchial equations of motion (HEOM) approach for non-perturbative and non-Markovian system-bath coupling cases under non-equilibrium steady-state conditions. For a weak interqubit interaction, the total system is regarded as two individually thermostatted systems, whereas for a strong interqubit interaction, the two-qubit system is regarded as a single system coupled to two baths. The roles of quantum coherence (or entanglement) between the two qubits (q-q coherence) and between the qubit and bath (q-b coherence) are studied through the heat current calculated for various strengths of the system-bath coupling and interqubit coupling for high and low temperatures. The same current is also studied using the time convolutionless (TCL) Redfield equation and using an expression derived from the Fermi golden rule (FGR). We find that the HEOM results exhibit turnover behavior of the heat current as a function of the system-bath coupling strength for all values of the interqubit coupling strength, while the results obtained with the TCL and FGR approaches do not exhibit such behavior, because they do not possess the capability of treating the q-b and q-q coherences. The maximum current is obtained in the case that the q-q coherence and q-b coherence are balanced in such a manner that coherence of the entire heat transport process is realized. We also find that the heat current does not follow Fourier’s law when the temperature difference is very large, due to the non-perturbative system-bath interactions.

  18. Evaluation of moisture and heat transport in the fast-response building-resolving urban transport code QUIC EnvSim

    NASA Astrophysics Data System (ADS)

    Briggs, Kevin A.

    QUIC EnvSim (QES) is a complete building-resolving urban microclimate modeling system developed to rapidly compute mass, momentum, and heat transport for the design of sustainable cities. One of the more computationally intensive components of this type of modeling system is the transport and dispersion of scalars. In this paper, we describe and evaluate QESTransport, a Reynolds-averaged Navier-Stokes (RANS) scalar transport model. QESTransport makes use of light-weight methods and modeling techniques. It is parallelized for Graphics Processing Units (GPUs), utilizing NVIDIA's OptiX application programming interfaces (APIs). QESTransport is coupled with the well-validated QUIC Dispersion Modeling system. To couple the models, a new methodology was implemented to efficiently prescribe surface flux boundary conditions on both vertical walls and flat surfaces. In addition, a new internal boundary layer parameterization was introduced into QUIC to enable the representation of momentum advection across changing surface conditions. QESTransport is validated against the following three experimental test cases designed to evaluate the model's performance under idealized conditions: (i) flow over a step change in moisture, roughness, and temperature, (ii) flow over an isolated heated building, and (iii) flow through an array of heated buildings. For all three cases, the model is compared against published simulation results. QESTransport produces velocity, temperature, and moisture fields that are comparable to much more complex numerical models for each case. The code execution time performance is evaluated and demonstrates linear scaling on a single GPU for problem sizes up to 4.5 x 4.5 km at 5 m grid resolution, and is found to produce results at much better than real time for a 1.2 x 1.2 km section of downtown Salt Lake City, Utah.

  19. Time-dependent photon heat transport through a mesoscopic Josephson device

    NASA Astrophysics Data System (ADS)

    Lu, Wen-Ting; Zhao, Hong-Kang

    2017-02-01

    The time-oscillating photon heat current through a dc voltage biased mesoscopic Josephson Junction (MJJ) has been investigated by employing the nonequilibrium Green's function approach. The Landauer-like formula of photon heat current has been derived in both of the Fourier space and its time-oscillating versions, where Coulomb interaction, self inductance, and magnetic flux take effective roles. Nonlinear behaviors are exhibited in the photon heat current due to the quantum nature of MJJ and applied external dc voltage. The magnitude of heat current decreases with increasing the external bias voltage, and subtle oscillation structures appear as the superposition of different photon heat branches. The overall period of heat current with respect to time is not affected by Coulomb interaction, however, the magnitude and phase of it vary considerably by changing the Coulomb interaction.

  20. Efficiency of Energy Use in the United States: Transportation, space heating, and air conditioning provide opportunities for large energy savings.

    PubMed

    Hirst, E; Moyers, J C

    1973-03-30

    We described three uses of energy for which greater efficiency is feasible: transportation, space heating, and air conditioning. Shifts to less energy-intensive transportation modes could substantially reduce energy consumption; the magnitude of such savings would, of course, depend on the extent of such shifts and possible load factor changes. The hypothetical transportation scenario described here results in a 22 percent savings in energy for transportation in 1970, a savings of 2800 trillion Btu. To the homeowner, increasing the amount of building insulation and, in some cases, adding storm windows would reduce energy consumption and provide monetary savings. If all homes in 1970 had the "economic optimum" amount of insulation, energy consumption for residential heating would have been 42 percent less than if the homes were insulated to meet the pre-1971 FHA standards, a savings of 3100 trillion Btu. Increased utilization of energy-efficient air conditioners and of building insulation would provide significant energy savings and help to reduce peak power demands during the summer. A 67 percent increase in energy efficiency for room air conditioners would have saved 15.8 billion kilowatt-hours in 1970. In conclusion, it is possible-from an engineering point of view-to effect considerable energy savings in the United States. Increases in the efficiency of energy use would provide desired end results with smaller energy inputs. Such measures will not reduce the level of energy consumption, but they could slow energy growth rates.

  1. Radiation and gas conduction heat transport across a helium dewer multilayer insulation system

    SciTech Connect

    Green, M.A.

    1995-02-01

    This report describes a method for calculating mixed heat transfer through the multilayer insulation used to insulated a 4K liquid helium cryostat. The method described permits one to estimate the insulation potential for a multilayer insulation system from first principles. The heat transfer regimes included are: radiation, conduction by free molecule gas conduction, and conduction through continuum gas conduction. Heat transfer in the transition region between the two gas conduction regimes is also included.

  2. Radiation and gas conduction heat transport across a helium dewar multilayer insulation system

    SciTech Connect

    Green, M.A.

    1994-10-10

    This report describes a method for calculating mixed heat transfer through the multilayer insulation used to insulate a 4 K liquid helium cryostat. The method described here permits one to estimate the insulation potential for a multilayer insulation system from first principles. The heat transfer regimes included are: radiation, conduction by free molecule gas conduction, and conduction through continuum gas conduction. Heat transfer in the transition region between the two gas conduction regimes is also included.

  3. A wave-dominated heat transport mechanism for negative differential thermal resistance in graphene/hexagonal boron nitride heterostructures

    NASA Astrophysics Data System (ADS)

    Chen, Xue-Kun; Liu, Jun; Peng, Zhi-Hua; Du, Dan; Chen, Ke-Qiu

    2017-02-01

    Nonlinear thermal transport in graphene/hexagonal boron nitride (h-BN) heterostructure is investigated by the nonequilibrium molecular dynamics method. It is found that negative differential thermal resistance (NDTR) will appear as the applied temperature difference increases. Detailed phonon spectra analysis reveals that the excited out-of-plane acoustic wave plays an important role in the heat transport across such interface. That is, the mechanical wave results in a significant mismatch between the lattice vibrations of graphene and h-BN domains and hinders interfacial thermal transport. In addition, NDTR can be tuned through the temperature parameter. Interestingly, the regime of NDTR becomes smaller and eventually vanishes with increasing the heterostructure length. However, NDTR is insensitive to the variation of system width. The work may be useful for nanoscale thermal managements utilizing the graphene/h-BN heterostructure.

  4. Probing liquation cracking and solidification through modeling of momentum, heat, and solute transport during welding of aluminum alloys

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Chakraborty, S.; DebRoy, T.

    2005-05-01

    A transport phenomena-based mathematical model is developed to understand liquation cracking in weldments during fusion welding. Equations of conservation of mass, momentum, heat, and solute transport are numerically solved considering nonequilibrium solidification and filler metal addition to determine the solid and liquid phase fractions in the solidifying region and the solute distribution in the weld pool. An effective partition coefficient that considers the local interface velocity and the undercooling is used to simulate solidification during welding. The calculations show that convection plays a dominant role in the solute transport inside the weld pool. The predicted weld-metal solute content agreed well with the independent experimental observations. The liquation cracking susceptibility in Al-Cu alloy weldments could be reliably predicted by the model based on the computed solidifying weld-metal composition and solid fraction considering nonequilibrium solidification.

  5. The effects of heat treatments on the transport properties of Cu/x/S thin films

    NASA Astrophysics Data System (ADS)

    Hmurcik, L.; Allen, L.; Serway, R. A.

    1982-12-01

    The resistivity and Hall effect of Cu(x)S (x = 1.995-2) thin films, which are used in the CdS/Cu(x)S solar cell currently investigated as an alternate source of electrical energy, has been measured as a function of temperature and heat treatment time. It is found that initial heat treatments cause copper in grain boundaries to diffuse irreversibly into the bulk. Further heating in hydrogen causes the resistivity to increase and the charge density and the mobility to decrease as surface oxides break up and free copper diffuses into the copper sulfide. Heating in oxygen reverses this process.

  6. Role of Remote Interfacial Phonon (RIP) Scattering in Heat Transport Across Graphene/SiO2 Interfaces.

    PubMed

    Koh, Yee Kan; Lyons, Austin S; Bae, Myung-Ho; Huang, Bin; Dorgan, Vincent E; Cahill, David G; Pop, Eric

    2016-10-12

    Heat transfer across interfaces of graphene and polar dielectrics (e.g., SiO2) could be mediated by direct phonon coupling, as well as electronic coupling with remote interfacial phonons (RIPs). To understand the relative contribution of each component, we develop a new pump-probe technique called voltage-modulated thermoreflectance (VMTR) to accurately measure the change of interfacial thermal conductance under an electrostatic field. We employed VMTR on top gates of graphene field-effect transistors and find that the thermal conductance of SiO2/graphene/SiO2 interfaces increases by up to ΔG ≈ 0.8 MW m(-2) K(-1) under electrostatic fields of <0.2 V nm(-1). We propose two possible explanations for the small observed ΔG. First, because the applied electrostatic field induces charge carriers in graphene, our VMTR measurements could originate from heat transfer between the charge carriers in graphene and RIPs in SiO2. Second, the increase in heat conduction could be caused by better conformity of graphene interfaces under electrostatic pressure exerted by the induced charge carriers. Regardless of the origins of the observed ΔG, our VMTR measurements establish an upper limit for heat transfer from unbiased graphene to SiO2 substrates via RIP scattering; for example, only <2% of the interfacial heat transport is facilitated by RIP scattering even at a carrier concentration of ∼4 × 10(12) cm(-2).

  7. A lead-before-break strategy for primary heat transport piping of 500 MWe Indian PHWR

    SciTech Connect

    Chattopadhyay, J.; Dutta, B.K.; Kushwaha, H.S.

    1997-04-01

    Leak-Before-Break (LBB) is being used to design the primary heat transport piping system of 500 MWe Indian Pressurized Heavy Water Reactors (IPHWR). The work is categorized in three directions to demonstrate three levels of safety against sudden catastrophic break. Level 1 is inherent in the design procedure of piping system as per ASME Sec.III with a well defined factor of safety. Level 2 consists of fatigue crack growth study of a postulated part-through flaw at the inside surface of pipes. Level 3 is stability analysis of a postulated leakage size flaw under the maximum credible loading condition. Developmental work related to demonstration of level 2 and level 3 confidence is described in this paper. In a case study on fatigue crack growth on PHT straight pipes for level 2, negligible crack growth is predicted for the life of the reactor. For level 3 analysis, the R6 method has been adopted. A database to evaluate SIF of elbows with throughwall flaws under combined internal pressure and bending moment has been generated to provide one of the inputs for R6 method. The methodology of safety assessment of elbow using R6 method has been demonstrated for a typical pump discharge elbow. In this analysis, limit load of the cracked elbow has been determined by carrying out elasto-plastic finite element analysis. The limit load results compared well with those given by Miller. However, it requires further study to give a general form of limit load solution. On the experimental front, a set of small diameter pipe fracture experiments have been carried out at room temperature and 300{degrees}C. Two important observations of the experiments are - appreciable drop in maximum load at 300{degrees}C in case of SS pipes and out-of-plane crack growth in case of CS pipes. Experimental load deflection curves are finally compared with five J-estimation schemes predictions. A material database of PHT piping materials is also being generated for use in LBB analysis.

  8. Charge and heat transport in soft nanosystems in the presence of time-dependent perturbations

    PubMed Central

    Perroni, Carmine Antonio; Ramaglia, Vincenzo Marigliano; Cataudella, Vittorio

    2016-01-01

    Summary Background: Soft nanosystems are electronic nanodevices, such as suspended carbon nanotubes or molecular junctions, whose transport properties are modulated by soft internal degrees of freedom, for example slow vibrational modes. Effects of the electron–vibration coupling on the charge and heat transport of soft nanoscopic systems are theoretically investigated in the presence of time-dependent perturbations, such as a forcing antenna or pumping terms between the leads and the nanosystem. A well-established approach valid for non-equilibrium adiabatic regimes is generalized to the case where external time-dependent perturbations are present. Then, a number of relevant applications of the method are reviewed for systems composed by a quantum dot (or molecule) described by a single electronic level coupled to a vibrational mode. Results: Before introducing time-dependent perturbations, the range of validity of the adiabatic approach is discussed showing that a very good agreement with the results of an exact quantum calculation is obtained in the limit of low level occupation. Then, we show that the interplay between the low frequency vibrational modes and the electronic degrees of freedom affects the thermoelectric properties within the linear response regime finding out that the phonon thermal conductance provides an important contribution to the figure of merit at room temperature. Our work has been stimulated by recent experimental results on carbon nanotube electromechanical devices working in the semiclassical regime (resonator frequencies in the megahertz range compared to an electronic hopping frequency of the order of tens of gigahertz) with extremely high quality factors. The nonlinear vibrational regime induced by the external antenna in such systems has been discussed within the non-perturbative adiabatic approach reproducing quantitatively the characteristic asymmetric shape of the current–frequency curves. Within the same set-up, we have

  9. Solar heat transport fluids for solar energy collection systems: A collection of quarterly reports

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Noncorrosive fluid subsystem is being developed that is compatible with closed-loop solar heating and combined heating and hot water systems. The system is also to be compatible with both metallic and nonmetallic plumbing systems, and any combination of these. At least 100 gallons of each type of fluid recommended by the contractor will be delivered.

  10. Device for plasma confinement and heating by high currents and nonclassical plasma transport properties

    DOEpatents

    Coppi, B.; Montgomery, D.B.

    1973-12-11

    A toroidal plasma containment device having means for inducing high total plasma currents and current densities and at the same time emhanced plasma heating, strong magnetic confinement, high energy density containment, magnetic modulation, microwaveinduced heating, and diagnostic accessibility is described. (Official Gazette)

  11. Heat pipe radiator. [for spacecraft waste heat rejection

    NASA Technical Reports Server (NTRS)

    Swerdling, B.; Alario, J.

    1973-01-01

    A 15,000 watt spacecraft waste heat rejection system utilizing heat pipe radiator panels was investigated. Of the several concepts initially identified, a series system was selected for more in-depth analysis. As a demonstration of system feasibility, a nominal 500 watt radiator panel was designed, built and tested. The panel, which is a module of the 15,000 watt system, consists of a variable conductance heat pipe (VCHP) header, and six isothermalizer heat pipes attached to a radiating fin. The thermal load to the VCHP is supplied by a Freon-21 liquid loop via an integral heat exchanger. Descriptions of the results of the system studies and details of the radiator design are included along with the test results for both the heat pipe components and the assembled radiator panel. These results support the feasibility of using heat pipes in a spacecraft waste heat rejection system.

  12. The impact of multidecadal NAO variations on Atlantic ocean heat transport and rapid changes in Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Delworth, Thomas; Zeng, Fanrong

    2016-04-01

    The Arctic and North Atlantic have experienced pronounced changes over the 20th and early 21st centuries, including a rapid loss of Arctic sea ice over the last several decades, prominent multidecadal variability in both ocean temperatures and sea ice, and decadal-scale change in tropical storm activity. We use suites of coupled climate model simulations to probe some of the factors responsible for the observed multidecadal variability in the Atlantic/Arctic system. In our models we show that multidecadal fluctuations of the North Atlantic Oscillation (NAO) induce multidecadal fluctuations of the Atlantic Meridional Overturning Circulation (AMOC). A positive phase of the NAO is associated with strengthened westerly winds over the North Atlantic. These winds extract more heat than normal from the subpolar ocean, thereby increasing upper ocean density, deepwater formation, and the strength of the AMOC and associated poleward ocean heat transport. In model simulations the observed negative phase of the NAO in the 1960s and 1970s led to a weaker than normal AMOC, reduced poleward ocean heat transport, a cold North Atlantic, and an increase in Arctic sea ice extent in both winter and summer. The NAO strengthened from the 1970s to the mid 1990s, leading to an increase of the AMOC and a warming of the North Atlantic. The increased heat transport extended throughout the North Atlantic, into the Barents Sea, and finally into the Arctic, contributing to a rapid reduction of sea ice in the 1990s through the 2000s. Feedbacks involving shortwave radiation are an important component of the overall changes. The NAO-induced AMOC increase also led to hemispheric-scale atmospheric circulation changes and increased Atlantic hurricane activity, as well as atmospheric teleconnections to the Southern Ocean. Since the mid 1990s the strong positive phase of the NAO has weakened to a more neutral phase. Climate projections for the next decade that take into account recent behavior of the

  13. Harvesting low-grade heat energy using thermo-osmotic vapour transport through nanoporous membranes

    NASA Astrophysics Data System (ADS)

    Straub, Anthony P.; Yip, Ngai Yin; Lin, Shihong; Lee, Jongho; Elimelech, Menachem

    2016-07-01

    Low-grade heat from sources below 100 ∘C offers a vast quantity of energy. The ability to extract this energy, however, is limited with existing technologies as they are not well-suited to harvest energy from sources with variable heat output or with a small temperature difference between the source and the environment. Here, we present a process for extracting energy from low-grade heat sources utilizing hydrophobic, nanoporous membranes that trap air within their pores when submerged in a liquid. By driving a thermo-osmotic vapour flux across the membrane from a hot reservoir to a pressurized cold reservoir, heat energy can be converted to mechanical work. We demonstrate operation of air-trapping membranes under hydraulic pressures up to 13 bar, show that power densities as high as 3.53 ± 0.29 W m-2 are achievable with a 60 ∘C heat source and a 20 ∘C heat sink, and estimate the efficiency of a full-scale system. The results demonstrate a promising process to harvest energy from low-temperature differences (<40 ∘C) and fluctuating heat sources.

  14. The Effect of Diffusional Transport and Surface Catalysis on the Aerothermodynamic Heating for Martian Atmospheric Entry

    NASA Technical Reports Server (NTRS)

    Henline, William D.; Papadopoulos, Periklis; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    For the reentry heating of 70-degree blunt sphere-cones entering Mars at velocities in excess of 6 km/sec, a study was performed to determine the magnitude of both convective and catalytic heating on the cone forebody. Case studies of the peak heating conditions for the current NASA Mars Pathfinder entry probe, as well as the peak heating conditions of the proposed NASA Mars 2001 aerobraking orbiter mission were performed. Since the actual behavior of the chemical recombination of Mars atmosphere hypersonic shock layer species on heat shield materials is not known, and no experimental studies of any consequence have been done to determine surface reaction rates for the CO2 system, a parametric analysis of various reaction schemes and surface catalytic mechanistic models was performed. In many cases the actual Mars entry probe will have a heat shield composed of an ablative material which can either partially or completely preclude the existence of catalytic surface recombination phenomena. The extent of this blockage effect has not been examined at this time and is not considered in this effort. Instead only non-ablative computations are performed to separately evaluate the full extent of the surface catalysis and related diffusional phenomena. Parametric studies include peak heating point comparisons of non-catalytic, partially catalytic and fully catalytic total surface heat transfer for three difference surface recombination catalytic mechanisms (with and without simultaneous CO + O and O + O recombination) as well as with different species diffusion models. Diffusion model studies include constant Schmidt number (equal diffusivities) and the bifurcation, approximate multi-component diffusion model. Since the gas phase reaction kinetics for the Mars CO2 based atmosphere have also not been validated, the effect of two different (fast and slow) sets of gas kinetics on heat transfer is presented.

  15. A full-Bayesian approach to the inverse problem for steady-state groundwater flow and heat transport

    NASA Astrophysics Data System (ADS)

    Jiang, Yefang; Woodbury, Allan D.

    2006-12-01

    The full (hierarchal) Bayesian approach proposed by Woodbury & Ulrych and Jiang et al. is extended to the inverse problem for 2-D steady-state groundwater flow and heat transport. A stochastic conceptual framework for the heat flow and groundwater flow is adopted. A perturbation of both the groundwater flow and the advection-conduction heat transport equations leads to a linear formulation between heads, temperature and logarithm transmissivity [denoted as ln (T)]. A Bayesian updating procedure similar to that of Woodbury & Ulrych can then be performed. This new algorithm is examined against a generic example through simulations. The prior mean, variance and integral scales of ln (T) (hyperparameters) are treated as random variables and their pdfs are determined from maximum entropy considerations. It is also assumed that the statistical properties of the noise in the hydraulic head and temperature measurements are also uncertain. Uncertainties in all pertinent hyperparameters are removed by marginalization. It is found that the use of temperature measurements is showed to further improve the ln (T) estimates for the test case in comparison to the updated ln (T) field conditioned on ln (T) and head data; the addition of temperature data without hydraulic head data to the update also aids refinement of the ln (T) field compared to simply interpolating ln (T) data alone these results suggest that temperature measurements are a promising data source for site characterization for heterogeneous aquifer, which can be accomplished through the full-Bayesian methodology.

  16. Combining in situ measurements and altimetry to estimate volume, heat and salt transport variability through the Faroe-Shetland Channel

    NASA Astrophysics Data System (ADS)

    Berx, B.; Hansen, B.; Østerhus, S.; Larsen, K. M.; Sherwin, T.; Jochumsen, K.

    2013-07-01

    From 1994 to 2011, instruments measuring ocean currents (Acoustic Doppler Current Profilers; ADCPs) have been moored on a section crossing the Faroe-Shetland Channel. Together with CTD (Conductivity Temperature Depth) measurements from regular research vessel occupations, they describe the flow field and water mass structure in the channel. Here, we use these data to calculate the average volume transport and properties of the flow of warm water through the channel from the Atlantic towards the Arctic, termed the Atlantic inflow. We find the average volume transport of this flow to be 2.7 ± 0.5 Sv (1 Sv = 106 m3 s-1) between the shelf edge on the Faroe side and the 150 m isobath on the Shetland side. The average heat transport (relative to 0 °C) was estimated to be 107 ± 21 TW (1 TW = 1012 W) and the average salt import to be 98 ± 20 × 106 kg s-1. Transport values for individual months, based on the ADCP data, include a large level of variability, but can be used to calibrate sea level height data from satellite altimetry. In this way, a time series of volume transport has been generated back to the beginning of satellite altimetry in December 1992. The Atlantic inflow has a seasonal variation in volume transport that peaks around the turn of the year and has an amplitude of 0.7 Sv. The Atlantic inflow has become warmer and more saline since 1994, but no equivalent trend in volume transport was observed.

  17. ICRF heating and transport of deuterium-tritium plasmas in TFTR

    SciTech Connect

    Murakami, M.; Batchelor, D.B.; Bush, C.E.

    1994-12-31

    This paper describes results of the first experiments utilizing high-power ion cyclotron range of frequency (ICRF) to heat deuterium-tritium (D-T) plasmas in reactor-relevant regimes on the Tokamak Fusion Test Reactor (TFTR). Results from these experiments have demonstrated efficient core, second harmonic, tritium heating of D-T supershot plasmas with tritium concentrations ranging from 6%--40%. Significant direct ion heating on the order of 60% of the input radio frequency (rf) power has been observed. The measured deposition profiles are in good agreement with two-dimensional modeling code predictions. Confinement in an rf-heated supershot is at least similar to that without rf, and possibly better in the electron channel. Efficient electron heating via mode conversion of fast waves to ion Bernstein waves (IBW) has been demonstrated in ohmic, deuterium-deuterium and DT-neutral beam injection plasmas with high concentrations of minority {sup 3}He (n{sub {sup 3}He}/n{sub e} > 10%). By changing the {sup 3}He concentration or the toroidal field strength, the location of the mode-conversion radius was varied. The power deposition profile measured with rf power modulation showed that up to 70% of the power can be deposited on electrons at an off-axis position. Preliminary results with up to 4 MW coupled into the plasma by 90-degree phased antennas showed directional propagation of the mode-converted IBW. Heat wave propagation showed no strong inward thermal pinch in off-axis heating of an ohmically-heated (OH) target plasma in TFIR.

  18. Transport Phenomena in Fluid Dynamics: Matrix Heat Exchangers and Their Applications in Energy Systems

    DTIC Science & Technology

    2009-07-01

    derived correlations of Nusselt number , heat transfer coefficient and friction factor in terms of Reynolds number , flow characteristics and geometry for a...empirical correlations for heat transfer coefficient (expressed in terms of Nusselt number , Stanton Number , J number , or simply h), and friction factor, f...an average solution for the perforated plate. They were able to derive an average Nusselt number correlation based on the Reynolds number and Prandtl

  19. A microscopic model for noise induced transport: Heat-bath nonlinearly driven by external white noise

    SciTech Connect

    Ghosh, Pradipta; Shit, Anindita; Chattopadhyay, Sudip; Chaudhuri, Jyotipratim Ray

    2011-03-15

    This work explores the observation that, even in the absence of a net externally applied bias, a symmetric homogeneous system coupled linearly to two heat baths is capable of producing unidirectional motion simply by nonlinearly driving one of the heat baths by an external Gaussian white noise. This is quite contrary to the traditional observation that, in order to obtain a net drift current, a state-dependent dissipation, which is a consequence of nonlinear system-bath coupling, is ubiquitous.

  20. Integral collector storage system with heat exchange apparatus

    DOEpatents

    Rhodes, Richard O.

    2004-04-20

    The present invention relates to an integral solar energy collector storage systems. Generally, an integral collector storage system includes a tank system, a plurality of heat exchange tubes with at least some of the heat exchange tubes arranged within the tank system, a first glazing layer positioned over the tank system and a base plate positioned under the tank system. In one aspect of the invention, the tank system, the first glazing layer an the base plate each include protrusions and a clip is provided to hold the layers together. In another aspect of the invention, the first glazing layer and the base plate are ribbed to provide structural support. This arrangement is particularly useful when these components are formed from plastic. In yet another aspect of the invention, the tank system has a plurality of interconnected tank chambers formed from tubes. In this aspect, a supply header pipe and a fluid return header pipe are provided at a first end of the tank system. The heat exchange tubes have inlets coupled to the supply header pipe and outlets coupled to the return header pipe. With this arrangement, the heat exchange tubes may be inserted into the tank chambers from the first end of the tank system.